PRACTICAL AND SCIENTIFIC 
 TREATISE 
 
 ON CALCAREOUS 
 
 MORTARS AND CEMENTS, 
 
 ARTIFICIAL AND NATURAL; 
 
 CONTAINING, 
 
 DIRECTIONS FOR ASCERTAINING THE QUALITIES OF THE DIFFERENT INGREDIENTS, FOR 
 
 PREPARING THEM FOR USE, AND FOR COMBINING THEM TOGETHER IN THE MOST 
 
 ADVANTAGEOUS MANNER ; WITH A THEORETICAL INVESTIGATION OF THEIR PROPERTIES 
 
 AND MODES OF ACTION. 
 
 THE WHOLE FOUNDED UPON AN EXTENSIVE SERIES OF ORIGINAL EXPERIMENTS, 
 
 WITH EXAMPLES OF THEIR 
 
 PRACTICAL APPLICATION ON THE LARGE SCALE. 
 
 BY L. J. VICAT, 
 
 ENGINEER IN CHIEF OF BRIDGES AND ROADS ; FORMERLY PUPIL OF THE " ECOLE 
 POLYTECHNIQUE J " MEMBER OF THE LEGION OF HONOUR, ETC., ETC., ETC. 
 
 TRANSLATED, 
 
 WITH THE ADDITION OF EXPLANATORY NOTES, EMBRACING REMARKS UPON THE RESULTS 
 OF VARIOUS NEW EXPERIMENTS, 
 
 BY 
 
 CAPTAIN J. T. SMITH, MADRAS ENGINEERS, F.R.S. 
 
 ASSOCIATE MEMBER OF THE CIVIL ENGINEERS INSTITUTION, LATE PRESIDENT 
 OF THE EDINBURGH PHILOSOPHICAL SOCIETY. 
 
 LONDON : 
 
 JOHN WEALE, ARCHITECTURAL LIBRARY, 
 59, HIGH HOLBORN. 
 
 1837. 
 
Digitized by the Internet Archive 
 
 in 2010 with funding from 
 
 NCSU Libraries 
 
 http://www.archive.org/details/practicalscientiOOvica 
 
TO 
 
 JOHN GRANT MALCOLMSON, ESQ., 
 
 MADRAS MEDICAL ESTABLISHMENT, M.D. , F.G.S., F. R.A.S., 
 ETC., KTC, ETC., 
 
 THIS WORK IS INSCRIBED, 
 
 IX TESTIMONY OF UNFEIGNED ESTEEM, 
 
 AND IN GRATEFUL ACKNOWLEDGEMENT OF NUMEROUS AND 
 
 DISINTERESTED ACTS OF REAL KINDNESS, 
 
 BY HIS ORLIOED 
 
 AND VERY SINCERE FRIEND, 
 
 J. T. SMITH, 
 
AUTHOR'S PREFACE. 
 
 The art of composing calcareous cements was confined, 
 till within the last few years, to the knowledge of a small 
 number of facts, and to the observance of certain rules 
 long since admitted into use without examination, on the 
 authority of Vitruvius and the architects who followed him. 
 But the rules were almost always found to be at fault, and 
 the facts, for want of correlativeness, were of but little aid. 
 Could we, for instance, manufacture good mortar in France, 
 by mixing three parts in bulk of dry pit sand, or two of river 
 sand, with one part of slaked lime derived from a white mar- 
 ble of great hardness ? Such, however, are the proportions of 
 admixture, and the characteristics of good limestone pointed 
 out by Vitruvius. It was of little importance besides to 
 those, to whom it was impossible to procure it, that the 
 pouzzolana of Italy and the Dutch tarras were possessed 
 of extraordinary binding qualities; that lime eminently 
 adapted for hydraulic works was to be found at Metz, Viviers, 
 Nismes, &c, in France, at Lcea in Upland, at Aberthaw in 
 England, and elsewhere. With all this information, and 
 even adding to it the discoveries of the Swedish Baggc, 
 and Count Chaptal, regarding the transformation of some 
 schists, and certain ochreous clays into pouzzolanas by calci- 
 nation, it was not the less necessary to work by guess in most 
 instances, or to trust to obscm-e analogies for the success of 
 the most important works. One engineer vaunted the effi- 
 cacy of the powder of tcell-burnt tile, another looked upon 
 smithy slag and iron-dross as the finest ingredients. These 
 again, on the other hand, asserted, that such substances are 
 destitute of energy. Lastly, this difference of opinion extended 
 even to the manipulation of the compounds. Was the lime 
 to be slaked with much water, or to be allowed to fall to 
 
IMU I 
 
 powder after having immersed it for a few second? ? .Should 
 it be applied hot or cold ? &c. Even- plan had its partisans ; 
 and what doubtless appears paradoxical was, that each me- 
 thod too was supported by experiments and testimony, of 
 which it was hardly possible to dispute the authenticity. 
 
 We shall leave it to the reader to appreciate a state of things 
 like this, and to decide whether such a chaos of opinions and 
 opposing facts could or could not make up a science. — a doc- 
 trine of calcareous cements. Perhaps it may be replied, that 
 at the epoch of which we speak, builders had learnt to erect 
 bridges, locks, Mc. without either tarras or pouzzolana, and 
 in countries where the lime possessed no extraordinary quality. 
 Without denying this truth, we must remark, that most of these 
 works have not endured, nor can continue to endure, but 
 by frequent and expensive repairs. That on many canals it 
 has been necessary to reconstruct a great many locks, whose 
 side walls were in a few years found to be quite stripped of 
 mortar. That a multitude of dikes, sluices, weirs, («* bar- 
 rage?,*') and aqueduct-, of recent construed' >n, already exhibit 
 all the characteristics of age. without the possibilitv of attri- 
 buting these unexpected dilapidations to any other cause than 
 the bad quality of the mortars or cements made use of. 
 
 These facts, known to a number of engineers, have long 
 since attested the insufficiency of the art : and this insuf- 
 ficiency exhibited itself more and more, owing to the mul- 
 tiplicity of marine works called for bv a constantly increasing 
 commerce. It wa- to put an end to such a state of things, 
 that we, in 181 '2, commenced our experimental researches, 
 published in 1818. The subject, so to speak, is one of intrinsic 
 importance, and consequently to discuss it merelv is sufficient 
 to attract public attention. We may. therefore, be allowed 
 to say. laying aside personal vanity, that the experimental 
 researches on lime and mortars have been the subject of se- 
 rious examination by chemists, architects, and engineers. Cer- 
 tain theoretical points, independent of general results, have 
 given rise to the-e di -. which have themselves stimu- 
 
PREFACE. Ill 
 
 lated us on our part to new labours. Experiments in contrast 
 with one another, undertaken in various parts of the kingdom 
 by order of Mr. Becquey, Director-General of Public Roads 
 and Mines, while they consolidated the necessary fundamental 
 points established by us, enlarged the domain of facts to such 
 an extent, that it became necessary to re-digest the whole, 
 in order to arrange and compare them together. But by 
 this very operation, owing to the multiplication and mutual 
 support of the truths, they have added fresh confirmation to 
 those which we were already possessed of. They have also en- 
 abled us to contract the scale comprehending them, both by 
 leaving us at liberty to adopt a mode of classification before 
 impossible, as well as by affording us the power of casting into 
 notes a crowd of details and historic or scientific documents, 
 useful to consult, but not indispensable to the understanding 
 of the whole. 
 
 It is, moreover, in the nature of things to become more 
 simple, in proportion as they approach perfection ; and this is 
 the more fortunate, as now-a-days, much more than formerly, 
 large volumes create alarm, and are no longer read. 
 
 These explanations having been given, we are anxious here 
 to make known the fresh obligations which we labour under 
 to the analytic and synthetic labours of Messrs. John and 
 Berthier, on calcareous compounds and hydraulic limes ; to the 
 researches of M. Bruyere, Inspector-General of Roads and 
 Bridges, on the manufacture of artificial pouzzolanas and 
 cements, resulting from the calcination of clays combined with 
 a small proportion of lime ; to the very remarkable experi- 
 ments of Messrs. Avril and Girard de Caudemberg, Engineers, 
 the first on the psammites of Finisterre — the second on the 
 arenes of Perigord ; to the examination of the limes of Russia 
 by Col. Raucourt, an examination which has led that Engineer 
 to enrich the science with numerous important observations ; 
 and lastly, to the interesting results obtained by M. Lacor- 
 daire, Engineer, in using the hydraulic limestones imper- 
 fectly burned, as natural cements. 
 
1\ I'HLIACL. 
 
 There are services of another kind which require no . 
 acknowledgment — such is the generous and enlightened 
 maimer in which M. Bruycre, Inspector-General, first, in 
 [Q18, obtained for rny work the attention and support of the 
 Director-General and Council of Roads and Bridges ; such 
 alpo if the succour afforded to this work by the honourable 
 mention of it which Messrs. Gay-Lussac and Thenard have 
 been pleased to make in their Lectures in the u Ecole Poly- 
 technique ;" in the Syllabus of his Lectures on Building by 
 ,M. Sgauzin. Inspector-General ; and lastly, in an able Re- 
 port to the Academy of Science?, by M. Girard, Member of 
 the Academy. 
 
TRANSLATOR'S PREFACE. 
 
 The merits of M. Vicat's valuable researches into the 
 composition of mortars and cements are already too well 
 known, to render it necessary for me to apologise for an 
 endeavour to extend their usefulness, by submitting them 
 to the public in a more accessible form. But as the motives 
 which induced me to undertake this work, and have en- 
 couraged me to persevere in its fulfilment, may require 
 explanation, I ought not to refrain from making them 
 known, nor from claiming that indulgence for the result of 
 my labours, which the peculiar circumstances under which 
 they have been accomplished render necessary. 
 
 Having been occupied for many years in the construction 
 and repairs of numerous public buildings, the charge of 
 which devolved upon me in the performance of staff duties, 
 I was long embarrassed, in the endeavour to give durability 
 to works executed under my superintendence, by many dif- 
 ficulties arising from the defective quality of the cements 
 employed, the dampness of the situation, and other causes 
 at the time unknown. 
 
 Anxious to remedy these evils, I engaged in a series of 
 experiments, in which numerous modifications of the pro- 
 cesses previously employed, and even.- suggestion which could 
 be gleaned from the scattered hints contained in the writings 
 of the various English authors who have incidentally touched 
 on the subject, were put to trial, both with reference to the 
 durability of the compounds, as well as their economy on the 
 large scale. But although these endeavours were followed 
 by many promising results, it was not until I became pos- 
 
VI TRANSLATOR B PREFACE. 
 
 sessed of M. Vicat's Work, that the theory of the composition 
 of mortars and cements was developed in a sufficiently satis- 
 factory and comprehensive manner, to enable me to take a 
 full view of the varied resources found within the limits of 
 almost every locality, for the fulfilment of the objects of 
 which I was in search. But, systematic and plain as M. 
 Vicat's instructions and experiments are when well under- 
 stood ; yet it was not without much labour, in repeating 
 many of the experiments, and the perusal of other French 
 authors on the same subject, that I was enabled to over- 
 come the difficulties occasioned by my imperfect acquaint- 
 ance with the exact meaning of the numerous technical term- 
 employed in it, and fully to appreciate the originality and 
 appropriateness of the experiments, and the depth and philo- 
 sophical accuracy of the reasoning founded on them. Hav- 
 ing surmounted these obstacles, and felt the great value of 
 the copious information placed at my disposal, I could not 
 look back upon the pains which it had cost me to effect my 
 object without being led to consider, that others similarly 
 situated with myself might have the same impediments to 
 contend with; and that I might assist future incpairers. by 
 placing the labours of M. Vicat within the reach of those, who 
 might not possess sufficient leisure to give that attention to 
 his work which I had found to be indispensable. 
 
 Of the desirableness of such a work, indeed, it needed but 
 little consideration to Batisfj me; for though intimately con- 
 nected as such researches are with the success and durability 
 of our most important const ructions, and with the security and 
 domestic comforts of every class of civilized society: it is re- 
 markable, that since the publication of Dr. Iliggins, now- 
 rendered obsolete by the rapid strides which the art has 
 taken since his time, no English work on this subject has 
 yet appeared. Nor have the investigations connected with 
 it, hitherto, attracted the attention of any of the distin- 
 guished philosophers, to whom science and the arts are in 
 other respect* so largely indebted. 
 
TRANSLATOR S PREFACE. VU 
 
 At a time, therefore, when the rapidly extending demands 
 of a quickly progressive civilization, daily give birth to new 
 and stupendous undertakings, there could be no doubt as 
 to the benefits which must result from bringing before the 
 public, the labours of those who have devoted themselves 
 to the study of this very important and hitherto neglected 
 branch of Architecture, and of placing within their reach the 
 manv valuable facts brought to light bv them. 
 
 But of my own fitness for this undertaking, even with 
 the advantages of expected leisure under which it was com- 
 menced, I could not avoid feeling the greatest diffidence ; nor 
 should I have ever ventured to incur so great a responsi- 
 bility, had I not been encouraged by the consideration, 
 that much which could not fail to be of service, might 
 be effected by the mere exertion of persevering industry. 
 And that, although, as I felt conscious, numbers might 
 have been found infinitely better qualified than myself to 
 do justice to the task; yet, that the very circumstance of 
 superior fitness, joined to the increasing demands upon the 
 talented members of the profession to whose province it 
 would most properly belong, would be sufficient to pre- 
 vent the public from ever deriving the benefit of their 
 assistance. 
 
 Under the influence of these considerations, therefore, and 
 in the hope of thereby finding useful and instructive occupa- 
 tion, for the leisure which an absence from my duties on ac- 
 count of ill health would afford me, I made up my mind to 
 commence the task. But I had not proceeded far, when I was 
 unfortunately deprived of the advantage upon which I had 
 principally relied for success, by being called upon to apply 
 the time I had intended to devote to this object, to the 
 service of Government in a different pursuit ; whereby I was 
 deprived of the ability to devote that attention and study to 
 it, which it was my earnest wish to have done. 
 
 These causes must, I fear, necessarily be pleaded as an ex- 
 cuse, for those inaccuracies which I cannot hope to have escaped 
 
viii TRANSLATOR S PREFACE. 
 
 from : and which will, I trust, be treated with indulgence. 
 In the general design and execution of the work, however, I 
 have not failed to keep in view the convenience of the reader, 
 in so far as it lay in my power to add to it, or to the general 
 usefulness of the volume. I have therefore, throughout, en- 
 deavoured to communicate whatever information it was in my 
 power to collect, either from the published works of others, or 
 from my own experiments, in illustration or support of the 
 opinions or statements contained in the text. The whole of 
 the measures made use of have, also, except when clearly unne- 
 cessary, been reduced to the corresponding English standard ; 
 a process which has also been applied to the very valuable 
 results collected together in the Tables. Thus, these experi- 
 ments now admit of a ready comparison with similar ones 
 made in this country, and the reader will find no difficulty 
 in forming a clear apprehension as to the efficiency of the 
 processes to which they are applied as tests. It may be pro- 
 per to add, that these calculations have been made from tables 
 of the correspondence of English and French weights and 
 measures, given at the end of Ure's Chemical Dictionary 
 (Edition of 1824). 
 
 In the first, or more practical part of the volume, ex- 
 planations have been given in the notes, of such scientific 
 terms as may not be familiar to the general reader. This, 
 however, has not been done in respect to all the notes in the 
 Appendix; as many of them, consisting of purely scientific 
 reasoning, conk) not, in the limited space of a note, have been 
 rendered perfectly intelligible to those by whom the terms 
 themselves were not understood. 
 
 These additions, with that of a copious Index, and a more 
 di-tinct separation of the various subjects severally treated, 
 will, I hope, materially assist the perusal ; more particularly by 
 obviating the confusion liable to be occasioned by the apparent 
 contradiction of the different directions given in the work, ap- 
 plicable to various circumstances. In the latter part of the 
 volume, I have ventured to take a liberty with respect to its 
 
TRANSLATOR S PREFACE. IX 
 
 arrangement, to which I was prompted by a desire to attract 
 the attention of the scientific reader to a subject hitherto little 
 noticed. I have for this purpose converted the " note on the 
 theory of calcareous mortars and cements" into a distinct 
 chapter (the seventeenth); to which the appendix to that note, 
 together with the particulars of some experiments by myself 
 in prosecution of the same subject, have formed an appro- 
 priate appendix. To this more prominent position in the 
 body of the work, the theoretical investigations above men- 
 tioned seemed to me to be entitled, both from their close 
 connexion with and essential influence over successful prac- 
 tice, as well as from their intrinsic value and philosophical in- 
 terest. Its discussion is accompanied, moreover, by so many 
 hints calculated to awaken attention and stimulate inquiry, 
 whilst so little seems to be wanting to complete the evidence, 
 that we may soon hope to be possessed of a sufficient number 
 of facts, to form the basis of a correct theory of the hitherto ill- 
 understood causes of solidification, under all the various cir- 
 cumstances in which it takes place. 
 
 In regard to the use of some new terms which I have 
 found it necessary to apply, it may be right to explain, 
 that after trying many substitutes taken from the tech- 
 nical language of the best authorities on this subject, I 
 found M. Vicat's classification so different and so much 
 more methodical than any which has hitherto obtained in 
 this country, that I should have run the risk of sacrificing 
 the clearness of his arrangement, had I attempted to intro- 
 duce any synonymes taken from the English language to 
 express his meaning, in lieu of the simple translation to which 
 I have confined myself. Other words, used for the purpose 
 of defining substances hitherto classed by us under a more 
 general category, and consequently intended to mark distinc- 
 tions at present unknown, such as " arenes," " psammites," 
 &c, I have thought it advisable to convert at once into Eng- 
 lish terms, taking care to explain their meaning on their first 
 application. 
 
X TRANSLATORS PREFACE. 
 
 Of the particular merits of the numerous practical instruc- 
 tions and varied processes contained in this volume, it would 
 perhaps be premature in me here to speak ; the most satisfac- 
 tory recommendation being the experience of those, who may 
 have occasion to put them to the test of actual trial. I ought 
 not, however, to omit to notice a circumstance which it would 
 be injustice to M. Vicat not to refer to. This is, that although 
 the processes he has laid down for the manufacture of artificial 
 hydraulic compounds are of a comprehensive nature, capable 
 of accommodating their results to the exact wants of the archi- 
 tect in every situation, thus including all the various kinds of 
 Roman Cements, &c. ; yet, it will be observed, that his own 
 practice seems to have been chiefly confined to the adoption 
 of the hydraulic limes, in lieu of the more energetic cements 
 more generally used in this Country. This preference 
 may expose him to the opposition of many firmly-established 
 usages and opinions, where the latter practice has so long and 
 successfully prevailed, with respect to the justice of which it 
 would not become me to hazard an opinion. M. Vicat has, 
 however, relieved me from that necessity, by expressing his 
 own very decidedly, in his declaration (in Chapter XV., Art. 
 263)] that the superior adhesion of the hydraulic limes over 
 our (so called) Roman cements, must inevitably, in time, give 
 them the preference, whenever the comparative merits of the 
 two are fairly known and appreciated. Now, without entering 
 upon the discussion of this question, I may remark, that it 
 appears to be one in which a contrariety of opinion may be oc- 
 casioned by a difference of situation and circumstances. Thus 
 it may perhaps be important, in considering the merits of the 
 two systems, to recollect, that in one the means of minute me- 
 chanical division are an essential element, in the other, that 
 it. is unnecessary ; and that this element which in one situation 
 may be obtained at a cheap rate, may in another be expensive 
 or unattainable. The hydraulic limes, therefore, which do not 
 require to be ground previous to use, are at all events, what- 
 ever may be their other merits, more especially suitable to 
 
TRANSLATOR S PREFACE. XI 
 
 those situations where the facilities of mechanical agency 
 cannot be resorted to. This circumstance would in itself 
 be sufficient to justify M. Vicat's opinion; but I have now 
 referred to it principally to point out, that the use of ground 
 cements, valuable as they are in our constructions, are better 
 adapted to the vicinity of a large capital, where it is of little 
 importance that the builder becomes dependent upon others 
 for his supply, than for a remote situation or a new country, 
 in which the unground limes cannot fail to be preferred, from 
 the facility with which they may be prepared by the mason 
 himself. The difference, in fact, consists in this, that the 
 ground cements, of whatever kind, will ever be furnished by 
 manufacturers, whereas the hydraulic limes may at all times be 
 prepared by the common workman, without machinery, and 
 at a cost not much exceeding that of common lime (vide note 
 to App. XVIII). And it will be in reference to this advantage, 
 in addition to those pointed out by M. Vicat, and in opposi- 
 tion to the inconveniences which may be occasioned by the 
 defect peculiar to them, their comparatively tardy solidification, 
 that the engineer will be guided in making the selection best 
 suited to his situation and exigencies. 
 
 Moreover, it is not merely in the accuracy of the details 
 of his valuable invention, that M. Vicat has done the most 
 service to the profession by the publication of his work ; we 
 must not forget the variety of other processes which he has 
 illustrated and verified by numerous and exact experiments, 
 and by which he has increased the resources of the practical 
 engineer in every situation. And it is by the broad light 
 thrown upon the relations of the numerous but ill-known in- 
 gredients, that he has placed within his reach a clew for the 
 formation of compounds, hitherto guided by empirical rules, 
 seldom derived from and therefore not adapted to the cir- 
 cumstances under which they are to be applied. 
 
 It now only remains for me to express my acknowledg- 
 ments for the assistance of which I have availed myself, in 
 the execution of my small part of this volume. Of the pub- 
 
xii translator's preface. 
 
 lished works to which I have had occasion to refer, I have 
 made a point of duly stating the authority to whom I have 
 been indebted; and to the distinguished authors to whom 
 these obligations are due, I have merely to add the names of 
 my friend Dr. Malcolmson, whose valuable services will be 
 recognised in various parts of the Work, and of Colonel Sim. 
 of the Madras Engineers, whose kindness in the ready com- 
 munication of the results of his extensive experience in the 
 processes for the manufacture of the celebrated mortars and 
 stuccoes of Madras, has added another favour to the many 
 debts of gratitude long due to him. 
 
TABLE OF CONTENTS. 
 
 SECTION I. 
 
 VARIOUS LIMES, OR AGENTS OF ADHESION IM CALCAREOUS 
 MORTARS AND CEMENTS. 
 
 CHAPTER I. 
 
 Pages. 
 
 Of limestones, and the various limes they furnish. — Distinction 
 of the known limes into rich, poor, and hydraulic limes. 
 Characteristics of the different limes. — Method of distin- 
 guishing and classifying them. — Relation between the quali- 
 ties of limes and the chemical composition of the stones 
 whence they are derived 1 
 
 CHAPTER II. 
 
 Calcination of limestone on the large scale. — Conditions neces- 
 sary to render the calcination as easy as possible. — Case of 
 the rich limes. — Case of the hydraulic limes. — Different kilns 
 made use of. — Average quantity of combustibles required 
 for the calcination of a cubic metre of lime. — Irregular 
 action of the coal kiln by slow heat 13 
 
 CHAPTER III. 
 
 Of artificial hydraulic limes. — Two modes of preparing them. 
 Comparison between the hydraulic limes and the water- 
 cements used in England. — Description of the processes 
 followed by M. Saint Leger at Paris. — Average price of 
 
 the artificial hydraulic limes 20 
 
 b 
 
li i Ai'.i i OB < "\i 1 S i • 
 
 CHAPTER IV. 
 
 Page?. 
 
 Of the slaking of lime. — Ordinary process. — How abused. 
 Expansion of the different kinds of lime. — Effect of cold 
 water upon rich lime in effervescence. — What renders lime 
 sluggish in slaking. — Second process of extinction. — How it 
 ought to be practised in order to reduce rich lime well. 
 Water absorbed. — Expansion of the various limes, in powder 
 not compressed. — Third process. — Water absorbed. — Expan- 
 sion. — Order of the throe processes in reference to the 
 degree of division communicated to the lime. — Action of 
 the carbonic acid of the atmosphere upon lines differently 
 slaked. — Method of preserving the different limes before 
 and after extinction 26 
 
 CHAPTER V. 
 
 Of the hydrates of lime, or solids resulting from the simple 
 combination of water and lime. — Influence of the degree of 
 consistency given to the hydrate in the first instance. — Ac- 
 tion of the air. — Mode of exhibiting this action. — Action of 
 the water. — Use that may be made of the hydrates in the arts. 34- 
 
 SECTION II. 
 
 VARIOUS INGREDIENTS WHICH UNITE WITH LIME IN THE 
 PREPARATION OF CALCAREOUS MORTARS AND CEMENTS. 
 
 CHAPTER VI. 
 
 Of sands. — Of arenes. — Of psammites. — Of clays. — Of volcauic 
 or pseudo-volcanic pouzzolanas. — Of the artificial products 
 analogous to pouzzolanas. — History of these substances ... 43 
 
 CHAPTER VII. 
 
 Qualities of the ingredients mentioned in the preceding 
 chapter. — Definitions — inert substances — slightly energetic 
 
TABLE OF CONTENTS. Ill 
 
 Page?, 
 substances — very energetic ditto. — Insufficiency of their 
 physical characters to denote the qualities specified under 
 the above denominations. — Approximate chemical methods 
 of recognising them ; by means of acids, by lime-water ... 52 
 
 CHAPTER VIII. 
 
 "Manufacture of artificial pouzzolanas. — What are the substances 
 most proper for such fabrication. — Conditions to be fulfilled 
 to attain the object. — Influence of a slight calcination and 
 the contact of the air. — Nature and quantity of the ingre- 
 dients in a good pouzzolana which are acted upon by 
 muriatic acid 58 
 
 CHAPTER IX. 
 
 Mutual suitableness of the ingredients, with the various limes, 
 in relation to the destination of the mortars or cements for 
 the preparation of which we use them. — Case of constant 
 immersion. — Case of alternations of dryness and moisture. 
 Case of exposure to the weather 64 
 
 SECTION III. 
 
 COMBINATION OF THE ELEMENTS OF CALCAREOUS MORTARS 
 AND CEMENTS. 
 
 CHAPTER X. 
 
 Mortars or cements intended for immersiou. — Choice of pro- 
 portions. — They are variable. — Limits established for certain 
 cases. — The proportions exert a more important influence 
 the less energetic the mixed substances are. — They must be 
 modified according to the use for which the mixtures are 
 intended. — Choice of the process of slaking — Order of pre- 
 
 b 2 
 
iv TABLE OK CONTENTS. 
 
 Pages, 
 eminence of the three known processes, in reference to the 
 nature of the lime made use of. — Manipulation or manufac- 
 ture — How it ought to be conducted under various circum- 
 stances. — Application to use, or immersion. — Difficulties to be 
 overcome, huw to manage them. — Old method defective. 
 Action of the water upon the parts of immersed mortars or 
 cements with which it is in immediate contact. — Influence 
 of time 67 
 
 CHAPTER XI. 
 
 Mortars or cements constantly exposed to the weather. — Mode 
 of correcting the bad qualities of rich limes. — Use of sand 
 in different mortars — Opinion of the ancients upon the 
 quality of sands. — Influence of their size — it varies with 
 different limes. — Method of mixing them. — Choice of pro- 
 portions, — with rich limes, — with hydraulic limes. — Choice 
 of the process of slaking ; — it is the same as in the case of 
 immersion. — Fabrication. — Conditions of a good manipula- 
 tion. — Use — difficulties to be overcome. — How to attain the 
 object. — Precautions in respect to drying to be taken after 
 application. — Very remarkable influence of time upon mor- 
 ta» of rich limey after many centuries 84 
 
 CHAPTEfl XII. 
 
 Mortars or cements subjected to the constant influence of ■ 
 damp soil — Influence of the coarseness of the sand. — Of the 
 process of slaking. — Proportions. — Application to use. — Of 
 concrete 9g 
 
 ( IIAPTKR XIII. 
 
 Of the vicissitudes to which cements and mortars may 
 be exposed. — Influence of these vicissitudes. — Case of 
 frosts. — Effects of the proportions and the size of well-mixed 
 Nmdi ]qo 
 
TABLE OF CONTENTS. V 
 
 CHAPTER XIV. 
 
 Pages. 
 
 Influence of beating upon the resistance of mortars — Cases in 
 which it is more injurious than useful. — Difficulties which 
 mortar when used as a plastic substance opposes to mould- 
 ing. — Case in which these difficulties disappear 106 
 
 CHAPTER XV. 
 
 Natural cements. — Composition of the calcareous minerals 
 which produce them. — Their advantages, their inconveni- 
 ences. — All argillaceous limestones when imperfectly burnt 
 afford natural cements Ill 
 
 CHAPTER XVI. 
 
 Of ancient mortals compared with mortars of the middle ages. 
 Description of the cement used in the Egyptian Pyramids. 
 State of the art in Egypt; — amongst the Greeks; — amongst 
 the Romans. — False opinion of the moderns as to the cause 
 of the hardness of ancient mortal's. — Known limits of abso- 
 lute resistance of mortars 1 14- 
 
 CHAPTER XVII. 
 
 Theories of calcareous mortars and cements ; their insufficiency. 
 M. John's experiments. — Macquer's hypothesis. Loriot 
 and Lafaye's opinions. — Definitions. — Four cases presented 
 by aggregates. — Probable consequences of the first case ; 
 ditto of second case; — ditto of third case; — ditto of 
 fourth case. — Theory of the solidification of hydraulic 
 limes. — M. Petot's experiments. — Remarkable influence of 
 sand on the absorption of carbonic acid in old mortars. 
 M. Berthier's opinion. — Its insufficiency. — Concluding re- 
 marks 124 
 
\1 1ABI.E OF I 
 
 APPENDIX. 
 
 NOTES OX CHAPTER L 
 
 No. Pages. 
 
 1. History of lime and calcareous minerals 141 
 
 2. Chemical methods of appreciating the qualities of lime- 
 
 stone* — Fruitless attempts of the ancients in this respect... 1-13 
 
 3. Of the way in which we have been enabled to add to the 
 
 facts made known in 1818. — Authenticity of the i 
 
 results 145 
 
 4. On the colour of limes ib. 
 
 5. Method of analyzing a magnesian limestone by hydration 146 
 
 6. Account of the Madras magnesia 14-7 
 
 7. History of artificial hydraulic limes 150 
 
 NOTES ON CHAPTER 11. 
 
 8. Effects of calcination on compound limestones. — Mutual 
 
 re-action of the constituents 152 
 
 9. Influence of aqueous vapour upon the calcination of lime- 
 
 stones. — Experiment by M. Gay-Lussac ib. 
 
 10. Fact relative to calcination in a clos< i --> I 153 
 
 11. Consequence of the imperfect burning of limesl 
 
 Contradictory experiments on this subject Ml 
 
 cperiments upon the di ffer e n t quantities of combustibles 
 used in tin burning of Kme 157 
 
 13. Sensible improvement which takes place in the burning of 
 lime with coal, by very alight modifications in the manage- 
 ment of the fire, and in the selection of the combustible ... 158 
 
 11. Irregular action of the coal kilns by slow heal (Jkm 
 ctmtmu). — Use of turf 159 
 
 15. Kilns with alternative fires for the buri; jriHaceous 
 
 limestone — manner of using them ib. 
 
TABLE OF CONTENTS. Vll 
 
 NOTES ON CHAPTER III. 
 
 No. Pages. 
 
 16. Remarkable instances of the use of artificial hydraulic limes 161 
 
 17. Opinion of certain chemists on the efficacy of oxide of 
 
 manganese in lime and mortars — Striking instance in op- 
 position to that opinion 163 
 
 18. Details of the manufacture of artificial hydraulic lime on 
 
 the first calcination under the most unfavourable circum- 
 stances ... 164 
 
 NOTES ON CHAPTER IV. 
 
 19. Examination of the vapour and gas disengaged during the 
 
 slaking of lime 166 
 
 20. Opinions of the masons regarding lime which slakes to 
 dryness 167 
 
 21. History of the various processes of slaking. — Examination 
 
 of Fleuret's process ib. 
 
 22. Numerical comparison of the bulks, with the quantities of 
 
 water absorbed 168 
 
 23. Observations on the quantity of lime contained in equal 
 bulks of the same consistency, of the different hydrates... 169 
 
 24. Remarkable fact of the indefinite preservation of rich lime 
 
 in paste, in damp trenches ib. 
 
 25. Notes regarding the preservation of limes slaked by im- 
 
 mersion 170 
 
 26. Repugnance of the workmen to the use of hydraulic lime. 
 
 Reasons of this repugnance ib. 
 
 27. Methods made use of at Doue (Maine and Loire) to slake 
 
 hydraulic lime, on the large scale and by immersion, and 
 
 to convey it by the Loire ib. 
 
 28. Experiment on a large scale on the preservation of quick- 
 
 lime 171 
 
 NOTES ON CHAPTER V. 
 
 29. Definition of the hydrate of lime by chemists. — How to 
 
 obtain it , 171 
 
 30. Experiments on the absorption of carbonic acid by mortars IT'2 
 
Mil TABLE OF CONTESTS. 
 
 No. Pages. 
 
 31. Progress of carbonic acid in the various hydrates of lime. 
 
 Jyses and remarks 173 
 
 32. Use of unmixed lime in buildings. — Composition of the 
 
 Madras chunam 175 
 
 NOTES ON CHAPTER VII. 
 
 33. Account of the use of arenes as pouzzolanas 177 
 
 34. Of the use of certain psammites as pouzzolanas ib. 
 
 35. Use of pouzzolana by the Romans. — Dutch tarras l~ s 
 
 36. Observations of Count Chaptal on the action of sulphuric 
 
 acid on some pouzzolanas 17i> 
 
 37. Experiment regarding the chemical inaction of lime towards 
 
 quartz. — Ditto upon the inaction of hydraulic lime in the 
 same circumstances ISO 
 
 NOTES ON CHAPTER VIII. 
 
 38. Account of some artificial pouzzolanas [82 
 
 39. Opinion of certain builders regarding the efficacv of the 
 
 oxide of iron — invalidated by facta 183 
 
 40. Opinion of Colonel Raucourt, Engineer, npon the influence 
 
 of the contact of the air in the calcination of artificial 
 pouzzolanas. — The absorption ofoxj gen is not sufficiently 
 ilished. — Investigation of the constituent principles of 
 pouzzolanas separately mixed with rich lime. — Case in 
 which it is impossible to overlook a chemical com- 
 bination ib. 
 
 11. Etererberatorj furnace proposed for the calcination of 
 
 pouzzolanas — its inconveniences — other forms 186 
 
 42. Experiments of M. Bruyen , Inspector-General of Roads, 
 upon artificial pouzzolanas. — Repeated on a large scale 
 
 by M. De Saint Leger 187 
 
 Kperiment tending to prove that clays calcined in contact 
 with the air do not absorb any gas. — The clays which 
 are calcined in a close vessel are not acted upon by acids 
 to the same degree as those calcined in the air ib. 
 
TABLE OE CONTENTS. IX 
 
 No. Pages. 
 4-4. Research into the influence of the admixture of pure 
 potash or soda with the clays previous to their cal- 
 cination, in reference to the energy of the artificial 
 pouzzolanas produced 189 
 
 45. Notice of Mr. Martin's new Patent cement 191 
 
 NOTES ON CHAPTER IX. 
 
 46. Explanation of the contradictions exhibited by various 
 
 writings regarding mortars and pouzzolanas 191 
 
 47. Table of the composition of the various mortars and 
 
 cements used by Mr. Smeaton 193 
 
 NOTES ON CHAPTER X. 
 
 48. Exceptions offered by the poor limes in relation to pro- 
 
 portions 194 
 
 49. Explanation of the influence of the various methods of 
 
 slaking ib. 
 
 50. The exception of the hydraulic limes explained 196 
 
 51. Different ways of viewing cements and mortars ib. 
 
 52. With reference to their texture and preparation 197 
 
 53. A mode of slaking approved by trial on a large scale ... ib. 
 
 54. The methods of fabrication and immersion approved, by 
 
 adoption on a large scale in the foundations of the bridge 
 
 of Charles X. at Lyons ib. 
 
 55. Fatal instance of the use of lime imperfectly slaked 198 
 
 56. Explanation of the deterioration of some water-cements and 
 
 mortars. — M. Petot's experiments 199 
 
 57. Cases of exception applicable to what has been said re- 
 
 garding the influence of time 201 
 
 NOTES ON CHAPTER XI. 
 
 58. Experiment upon the influence of calcareous sand in com- 
 
 parison with granitic 201 
 
 59. Ancient examples, accidental or designed, in favour of the 
 
 principles laid down regarding the influence of the coarse- 
 ness of the grain in sands 202 
 
i TABLE OF CONTENTS. 
 
 incient examples tending to prove the fatal influence of 
 
 clav in mortars exposed to the weather 203 
 
 61. Explanation of the varied effects of the different methods 
 
 of slaking ib. 
 
 nanimous opinion respecting mortars and cements mixed 
 thin. — Means tried to effect kneading them very stiff ... 204 
 Method employed at the canal from Nantes to Brest, to 
 guard the hands of the masons from the action of the 
 lime. — Precautions to be taken relative to the soakiug 
 the materials used in masonry 206 
 
 64. The influence of slow drying upon the goodness of mor- 
 
 tars known in Italy, and made use of in the fabrication 
 
 cf artificial stones 207 
 
 65. Remarkable instance of the time which mortar of rich lime 
 
 requires to harden. — Chemical comparison of various 
 old and ancient mortars of excellent quality. — Mode of 
 reducing the results of chemical anayles into technical 
 language 209 
 
 NOTES OX CHAPTER XIII. 
 
 66. Observations upon certain cases of deterioration of cen 
 
 removed from a damp situation to a dry one 212 
 
 •he protection of stuccoes from the 
 
 weather ib. 
 
 rfeets of frost upon mortars and cement-. — Difficulty of 
 
 explaining them. — Usual mode of experiment- — Remarks 
 
 on the decay of mortars in the mild climate of India ... 213 
 
 lethod proposed by M. Brard to distinguish E 
 
 liable to be affected by frost. — Application of that method 
 
 to various mortars, — Bran! ■ does not ai;- 
 
 with mixtun - kind; — ii. t to bricks and 
 
 stones it may be of great service 
 
 )X CHAPTE1 XIV. 
 
 70. Poor success of Loriot's process applied to mortar c 
 
 dcred as a plastic substance. — Smeaton's remarks on ditto 21 9 
 
TABLS OK CONTENTS. XI 
 
 NOTES ON CHAPTER XV. 
 
 No. Pages. 
 
 71. Account of the English and Russian natural cements. 
 
 Notice of a cement found in the Madras Presidency ... 220 
 
 NOTES ON CHAPTER XVI. 
 
 72. Particulars of the analysis of the cement of the Pyramid 
 
 of Cheops, by Dr. Malcolmson 222 
 
 73. Observations upon certain calcai'eous incrustations 224? 
 
 74-. Examples of ancient mortars of great hardness 225 
 
 NOTES ON CHAPTER XVII. 
 
 75. Particulars of an experiment upon the solidification of the 
 
 calcined sulphate of lime (Plaster of Paris) 226 
 
 76. Experiments upon the solidification of cements composed 
 
 of rich lime, and artificial pouzzolana ib. 
 
 77. Remarks upon M. Girard's " Notice sur de nouveaux 
 
 mortiers hydrauliques" 228 
 
 TABLES. 
 
 Account of the manner in which the experiments were made. 234 
 
 TABLE No. 1. 
 
 Comparison of the qualities of various limes with the chemical 
 composition of the limestones from which they are derived... 237 
 
 TABLE No. 2. 
 
 Comparison of the hardness and absolute resistance of com- 
 pounds, resulting from the combination of water with various 
 limes 238 
 
Xll TAB1.L 01 >- OS 1 KM li. 
 
 TABLE No. 3. (bis.) 
 
 Pages. 
 The action of muriatic acid upon clays taken in different states, 
 compared 239 
 
 TABLE No. 3. 
 
 Comparison of the qualities of ingredients with their behaviour 
 in regard to muriatic acid 210, 211 
 
 TABLE No. 1. 
 
 Comparison of the various artificial pouzzolanas with the Italian 
 pouzzolana, tarras, and the aqua-fortis cement 212 
 
 TABLE No. 5. 
 
 Comparison to aid in establishing the reciprocal adaptability of 
 the various limes to the different ingredients of mortars and 
 cements 213 
 
 TABLE No. 6. 
 
 Hvdraulic mortars and cements compared, in reference to the 
 process of slaking made use of 211.215 
 
 TABLE No. 7. 
 
 Comparison of the relative resistances of the various hydraulic 
 mortars and cements, immersed in different states of con- 
 ristancy 246 
 
 TABLE No. 8. 
 
 Water-cements and mortars compared in reference to the dete- 
 rioration which they undergo at their surfaces. — The quick- 
 ness of set of different cements compared with the varieties 
 of composition of these cements, and the resistance they ac- 
 quired after one year's immersion 217 
 
TABLE 01 CONTENTS. X1U 
 
 TABLE No. 9. 
 
 Pages. 
 Quickness of set of various cements compared with the propor- 
 tions and the hardness acquired after one year's immersion 248 
 
 DOUBLE TABLE No. 10. 
 
 Absolute resistance of mortars, compared with that of the 
 hydrates of lime which form their matrix. — Mortars com- 
 pared in reference to the coarseness of the sand made use of 249 
 
 TABLE No. 11. 
 
 Mortars taken from various buildings compared with mortars 
 compounded for experiment from the same limes 250 
 
 TABLE No. 12. 
 
 Mortars compared in reference to their proportions, and the 
 mode of slaking 251 
 
 TREBLE TABLE No. 13. 
 
 Mortars of rich lime compared in reference to the influence of 
 manipulation. — Mortars compared in reference to the con- 
 sistency given to the mixture of lime and sand. — Mortars 
 compared in relation to the influence of desiccation 252 
 
 DOUBLE TABLE No. 14. 
 
 Absolute resistances of various mortars compared in reference 
 to the effect of beating. — Mortars and cements compared in 
 reference to their specific gravity and their porosity 253 
 
 TABLE No. 15. 
 
 Characteristics, composition, and absolute resistances of some 
 Roman mortars from the South of France 254 
 
XIV TAIU.r OF CONTENTS. 
 
 TABLE No. 16. 
 
 Pages. 
 Comparison of the resistances of various compounds in refe- 
 rence to the proportions, and the coarseness of the sub- 
 stances introduced into the matter forming the matrix 255 
 
 TABLE No. 17. 
 Analyses of various old mortars 256 
 
 INDEX 257 
 
A 
 
 COMPENDIUM, 
 
 &c. &c. 
 
 SECTION I. 
 
 CHAPTER I. 
 
 OF CALCAREOUS MINERALS, AND THE VARIOUS KINDS 
 OF LIME THEY FURNISH. 
 
 1. Calcareous minerals are substances essentially 
 composed of lime and carbonic acid ; a they always dis- 
 solve, either wholly or in part, in weak acids, with a 
 more or less brisk effervescence, and may be scratched 
 with an iron point. 
 
 2. Limestones arc sometimes pure, that is to say, 
 wholly composed of lime and carbonic acid ; at others, 
 the lime is associated in intimate combination with 
 silica, alumina, b magnesia, with quartz in grains, 
 oxide of iron, manganese, bitumen, or sulphurctted- 
 
 a Carbonic acid is a gas composed of one equivalent of carbon 
 and two of oxygen : it is transparent and colourless, and incapable 
 of supporting combustion or respiration: it combines with the alka- 
 lies, oxides, &c, forming the class of carbonates. — Tr. 
 
 b Alumina, or oxide of aluminum as it is now termed, is the sub- 
 stance which forms the basis of the plastic clays. — Tr. 
 
 c Manganese is a metal similar in appearance to iron, but rarely- 
 met with in the metallic state. — Tr. 
 
2 CALCAREOUS MINERALS, [CHAP. 
 
 hvdrogen. d The presence of these substances one 
 bv one, or two and two, or three and three, &c, con- 
 stitutes the various kinds of limestone, which arc fur- 
 ther subdivided into different varieties. 
 
 3. Mineralogists distinguish the argillaceous, mag- 
 nesian, sandy (arcnaces), ferruginous, manganesian, 
 bituminous, fetid, &c. ; and then in each of these kinds 
 point out varieties of form and structure, which they 
 specify under the denominations of foliated, lamellar, 
 saccharoidal, 6 granular, compact, globular, coarse/ 
 chalky, pulverulent, pseudo-morphous, g concretionary, 
 nodular, ("geodiques" h ) incrusting, &c, &c. (App. I.) 
 
 d Sulphuretted-hydrogen is a compound gas, containing one equi- 
 valent of sulphur, and one of hydrogen. It is liable to be extricated 
 on the decomposition of a metallic sulphuret by water, whence it is 
 not an uncommon natural product. — Tr. 
 
 c " The whitest and most esteemed (granular limestone), from its 
 resemblance to sugar, has been termed by the French mineralogists 
 chaux carbonatee saccharoide ; but it has more generally, from its 
 important uses in the arts, obtained the name of Statuary Marble." 
 — PltiUij)s's Mineralogy, edit. 1816. 
 
 f " The bouses of Paris are built of a large-grained and soft cal- 
 careous stone, which is incapable of polish, and is of B dingy white, 
 grey, or yellowish-white colour. It is found in immense horizontal 
 Id its, forming the plains south of Paris. It is a very impure lime- 
 stone, and furnishes when calcined a very bad lime. The use to 
 which it is put has occasioned its receiving the familiar name of 
 Pierre a batir. Ilaiiy describes it under that of chaux carbonatee 
 grossiere." — Ibid, p. \9B* 
 
 8 " Minerals exhibiting impressions of the forms peculiar to the 
 crystals of other substances are said to be pseudo-morphous." — 
 Ibid, p. 1. 
 
 h " A geode is a hollow ball. At Oberstein, in Saxony, are found 
 hollow balls of agate lined witli crystals of quartz or amethyst, 
 which are termed geodes." — Ibid, p. xlvi. 
 
I.] \XD LIMES THEY FURNISH. 3 
 
 4. It is useful to be acquainted with this nomencla- 
 ture ; but that which it is of the most importance for 
 the builder to be aware of, is, that each variety of 
 limestone furnishes a peculiar kind of lime, distinct 
 in colour, weight, in its avidity for water, and above 
 all by the hardness it acquires on being mixed inti- 
 mately after slaking with the earthy substances known 
 under the names of sand, puzzuolana, &c. 
 
 5. The physical characters which serve to distin- 
 guish calcareous minerals, fail to give anv certain 
 indication of the qualities of the lime they contain. 
 Even chemical analysis itself is mostly but an ap- 
 proximate mode of investigating them, in addition to 
 its being onlv within the reach of those familiar with 
 laboratory manipulation. Experience by actual trial 
 ought to be the builder's only guide. (App. II.) 
 
 6. We readily assure ourselves that a mineral be- 
 longs to the calcareous class, by trying it, as I have 
 already said, with an iron point, and a weak acid.' 
 Having established this fact, we reduce the experi- 
 mental specimens to the average size of a large wal- 
 nut, and fill with them a crucible ("gazette"), or any 
 other vessel of baked earth, pierced with holes to 
 favour the circulation of the air : wc place the whole 
 in the middle of a potterv furnace, (a brick or lime- 
 kiln will answer equally as well, if it is heated by the 
 flame of a fire of wood or furze,) and at the end of 
 its calcination (fifteen to twenty hours) we remove the 
 material, and introduce it while still warm into large- 
 mouthed bottles, quite dry, and which we immediately 
 
 ' Vide Articles 1 and 23. 
 
 B 2 
 
4 CALCAREOUS MINERALS, [CHAP. 
 
 close hermetically. The object of this precaution is 
 to preserve the lime in all its activity (causticity), 
 till the moment fixed on to submit it to experiment. 11 
 
 7. When we feel disposed to begin this experiment, 
 we remove the lime from the bottle, and take as much 
 in bulk as would about fill a quart measure (includ- 
 ing voids) : we put it into a cloth bag of an open 
 material, or rather a small basket ; we immerse the 
 whole for five or six seconds only in pure water ; we 
 drain it an instant, and then empty the bag or basket 
 into a stone or cast-iron mortar. 
 
 8. The following are the different phenomena 
 which may ensue after this immersion : — 
 
 1st. The lime hisses, decrepitates, swells, gives out 
 a great quantity of hot vapours, and falls to powder 
 instantaneously, or nearly so. 
 
 2nd. The lime remains inactive for a space more 
 or less long, not exceeding five or six minutes ; after 
 which the phenomena above described manifest them- 
 selves with energy. 
 
 3rd. The lime exhibits no alteration even after five 
 or six minutes ; a quarter of an hour even may elapse 
 before it appears to change its state. However, it 
 begins to smoke and crack with little or no decrepita- 
 tion : the vapour formed is less abundant, and not so 
 hot, as in the preceding case. 
 
 4th. The phenomena do not commence till an hour, 
 and sometimes till many hours, after the cxmcrsion. 
 
 k In order to make sure that the calcination is complete, it 
 would be as well to subject a small portion of the lime to trial, by 
 slaking it with a little water, and adding dilute muriatic acid : if 
 sufficiently burned it ought to dissolve without effervescence. — Tr. 
 
I.] AND LIMES THEY FURNISH. 5 
 
 Cracks form without decrepitation, slight fumes are 
 given out, and but little heat is disengaged. 
 
 5th. The phenomena commence at periods very 
 variable, but are hardly sensible ; the heat developed 
 barely manifests itself except to the touch ; the pul- 
 verulence is but obscurely marked, and sometimes 
 does not ensue at all. 1 
 
 9. In no case is it necessary to wait till the effer- 
 vescence has ceased in order to finish the slaking ; 
 as soon as the disaggregation manifests itself, we pour 
 water into the vessel, not upon the lime, but on one 
 side, in such a manner that it may flow freely to the 
 bottom, whence it is sucked up by those portions of the 
 material which are farthest advanced. We stir it at 
 the same time with a spatula; continuing to add water 
 if it be required, but with care not to drown the mix- 
 ture. Lastly, we substitute the pestle for the spatula, 
 and work the whole up to a stiff clayey consistency. 
 
 10. Thus prepared, the lime must be left to itself 
 till the more sluggish portions have completed their 
 developement. The termination of this part of the 
 operation is indicated by the perfect cooling of the 
 whole mass. It lasts from two to three hours, and 
 sometimes more. 
 
 1 If the calcined mineral (having been proved to be calcareous 
 by trial with dilute acid — Articles 1 and 6) should not .--lake at all, 
 or very imperfectly, it must be reduced mechanically to a perfectly 
 impalpable powder, without the addition of water, and then dealt 
 with as afterwards explained (Articles 11 and 12). Many of the 
 most energetic and useful of the water-cements, such as the York- 
 shire, the Harwich, and Sheppy cements, require to be treated in 
 this manner. — Tu. 
 
li CALCAREOUS MINERALS, [CHAP. 
 
 11. We now take the lime again with the pestle, 
 and add water if it be required, in such quantity as to 
 give us a paste as stiff as possible, yet not entirely de- 
 prived of a certain degree of ductility. Its consist- 
 ency may be compared to that of clay ready to be 
 worked up in the manufacture of pottery. 
 
 12. We then take any vessel of greater height than 
 breadth ; (a china mustard-pot, or a large drinking 
 glass, will answer the purpose very well;) we transfer 
 the lime to it in such quantity as to fill it up about 
 two-thirds or three-fourths, striking the bottom of it 
 with the palm of the hand or on a block to cause the 
 material to settle down and spread itself on the bot- 
 tom of it ; we then label it carefully, and immcrge 
 the whole without delay, noting the day and hour of 
 the immersion. 
 
 13. In studying successively during fourteen years 
 the most remarkable limes of this kingdom treated in 
 this manner, I have been led to arrange them in five 
 categories, distinguished bv the following denomina- 
 tions (App. III.) : — 1st, Rich limes; 2nd, Poor limes; 
 3rd, Limes slightly hydraulic ; 1th, Hydraulic limes ; 
 5th, Limes eminently hydraulic. 
 
 1 1. The rich limes are such as may have their 
 volume doubled, or more, by slaking in the ordinary 
 manner," and whose consistency after many years of 
 immersion remains still the same, or nearly the same 
 a- on the first day, and which dissolve to the last 
 grain in pure water frequently changed." 
 
 m Vide Article 56. and App. XXII. — Tr. 
 
 n Solubility in water may be used as a eonvenn at 1 the 
 
I.] AND LIMES THEY FURNISH. 7 
 
 15. The poor limes are such as have their volume 
 but little or not at all augmented by slaking, and 
 which, in other respects, exhibit in the water very 
 nearly the same phenomena as the rich limes, but 
 with this difference, that they only dissolve partially, 
 leaving a residue of no consistency. 
 
 16. The moderately hydraulic limes will set v in 
 fifteen or twenty days after immersion, and con- 
 tinue to harden ; but their progress becomes more 
 and more slow, particularly after the sixth to the 
 eighth month. After one year their consistency is 
 about equal to that of hard soap. They dissolve also 
 in pure water, but with great difficulty ; their expan- 
 sion by slaking (" foisonnement" q ) is variable ; it fre- 
 
 propcr calcination of rich lime : in this case, if a little coarse sugar 
 be melted previously in the water, it will very much increase its 
 solvent power. — Tk. 
 
 ° Rich limes also may leave an insoluble residue (of carbonate 
 of lime) if either insufficiently burned, or if they should have been 
 much exposed to the air, and become partially regenerated by the 
 absorption of carbonic acid. Should there be any reason to sus- 
 pect this, a drop or two of muriatic acid should be added to the 
 water ; when, if the residue be the carbonate of lime, formed as 
 above explained, it will dissolve with effervescence ; but if it be 
 composed of the silicious matter of a " poor lime," it will remain 
 insoluble. — Tr. 
 
 p Vide Article 20. 
 
 i "Lorsqu'on Otciut lachaux commune avec de 1\ au,a sa sortie du 
 lour, pour la lvduire en pate, on trouve qu'elle augmente considcra- 
 blementde volume; cette augmentation est telle qu'une partie de 
 chaux vive inesuree en volume en produit qnelque fois plus de 
 trois mesuree a l'etat de pate epaisse : e'est ce qu'on appelle le foi- 
 sonnement." — General Treussart, Memoire sur les Jlurtkrs Ily- 
 (havlifjues, p. 3. 
 
8 CALCAREOUS MINERALS, [CHAP. 
 
 quently reaches the limits of the poor limes, without 
 ever attaining that of the rich limes. 
 
 17. The hydraulic limes set after six or eight days' 
 immersion, and continue to harden. The progress 
 of this induration may he continued to the twelfth 
 month, although the greatest part of the effect will he 
 attained after six months. At this period, the hard- 
 ness of the lime may he already compared with that 
 of the very soft kinds of stone, and the water ceases 
 to have any action on it. Their expansion by slaking 
 is always small, like the poor limes. 
 
 18. The eminently hydraulic limes set from the 
 second to the fourth day of immersion. After one 
 month they are already very hard, and altogether in- 
 soluble. At the sixth month they appear like the 
 absorbent calcareous stones, whose surface admits of 
 being cut. They splinter under a blow, and present 
 a slaty fracture. Their expansion by slaking is con- 
 stantly small, like the poor limes. 
 
 19. In other respects, the rich, and poor, and hydrau- 
 lic limes of all grades, may be white, grey, mouse- 
 coloured, red, &c. r (App. IV.) 
 
 T As no reference is here made to the properties of magnesian 
 limestones, it may be useful to describe a mode by which they may 
 be recognised. Though capable of setting under water, they may 
 be entirely soluble in dilute acid ; but magnesia not combining with 
 water till exposed for some time in contact with it, the mineral, if 
 containing a large proportion of this substance, will cither not slake 
 at all, Or will do so imperfectly, and will gain much less in weight 
 than an equal quantity of calcined rich lime would do. Upon this 
 property of magnesian limestone, Mr. Prinsep has founded a very 
 neat and umple process for estimating the proportions of the consti- 
 
I.] AND LIMES THEY FURNISH. 9 
 
 20. We say that a lime has set, when it bears with- 
 out depression a knitting-needle of 0.12 cent. (.017 
 or nearly ^ T) inch) diameter, filed square at its ex- 
 tremity, and loaded with a weight of 0.30 kil. (about 
 10 ozs. 9 drs. avoirdupois weight). In this state the 
 lime will resist the finger pushed with the mean 
 strength of the arm, and it is incapable of altering 
 its form without fracture. 
 
 21. The chemical examination of the minerals 
 which supply the various kinds of lime of the preceding 
 categories, points out, in a general way, as follows: — 
 
 1st. As furnishing the rich limes : 1st, the pure 
 limestones, or such as contain only an admixture of 
 from .01 to .06 of silica, alumina, magnesia, iron, &c, 
 taken separately, or two and two, three and three, 
 &c. ; 2dly, the simple, bituminous, or fetid limestones. 8 
 
 2nd. Such as form the poor limes: 1st, limestones 
 associated with silica in the state of sand, magnesia, 
 the oxides of iron and manganese, in variable propor- 
 tions, but limited to .15 to .30 of the whole, whether 
 these principles exhibit themselves one by one, two 
 and two, three and three, or all together. 
 
 3rd. As furnishing the slightly hydraulic limes : 
 
 tuent ingredients, of which an explanation will be found in the 
 notes. (Vide App. V.) — Tr. 
 
 s " Swine-stone, or stink-stone, so called from the strong fetid 
 odour given out when scraped or rubbed, is found massive and 
 compact, and of various shades of grey, brown, and black. By cal- 
 cination it becomes white, and burns into quicklime. The offensive 
 odour which it gives out when scraped is considered to be owing to 
 its including sulphuretted-hydrogen: it is commonly attributed to 
 bitumen, which tines not <eom to enter into the composition of 
 Bwine-fitone." — Phillips's Mincraloyy, p. 130. 
 
10 CALCAREOUS MINERALS, [CHAP. 
 
 the limestones united with clay, magnesia, iron, and 
 manganese, the relative proportions of which being 
 variable, but not exceeding .OS to .12 of the whole. 
 The oxides of iron and manganese also, being present 
 either in the relations one to one, two and two, three 
 and three, \c, &c, or even entirely wanting. 
 
 lth. The ingredients constituting the hydraulic limes. 
 These are the limestones containing silica, alumina, 
 magnesia, iron, and manganese, in variable relative 
 proportions, amounting to not more than from fifteen 
 to eighteen hundredths of the whole, and in other re- 
 spects such, that the silica always has a predominance, 
 no matter whether the other substances appear, as one 
 to one, or two and two, &c, kc. The iron, manganese, 
 and magnesia, may also be entirely wanting. 
 
 jth. The minerals affording the eminently hydraulic 
 limes are, the limestones which contain silica, alumina, 
 magnesia, iron, and manganese, in different relative 
 proportions, but usually limited to from twenty to 
 twenty-five hundredths of the whole ; the silica al- 
 ways predominating, sometimes to the extent of form- 
 ing of itself more than half the whole; and the other 
 substances only occurring one by one, two and two, or 
 three and three, &c. It is very seldom that we meet 
 with them all at one time. The magnesia, and still 
 more, the manganese, are very frequently absent. 
 
 22. In the present state of our knowledge regard- 
 ing the different varieties of lime, it is impossible to 
 say whether there exi^t certain determinate propor- 
 tions of silica alone, or of silica and alumina, or of 
 silica and magnesia, &c, ftc., which, by their inti- 
 mate association with the same quantity of calcareous 
 
I.] AND LIMES THEY FURNISH. 11 
 
 matter, are capable of producing limestones of equal 
 energy. But one thing which is certain, and which 
 it is important to recollect, is, that no perfectly 
 hydraulic mortar exists without silica, 1 and that all 
 lime which can be so denominated, is found by che- 
 mical analysis to contain a certain quantity of clay, 
 made up of silica and alumina in proportions similar 
 to what constitutes the ordinary clays. (App. VII.) 
 
 23. The preceding observations being clearly un- 
 derstood, we see how easy it is in a few minutes to 
 detect a mineral composed of rich lime, by dissolving 
 three or four grammes (fifty or sixty grains) of it in 
 dilute nitric or muriatic acid. If there should be left 
 no insoluble residue, or if that residue be very tri- 
 fling, it is useless to carry the experiment any farther." 
 In the other case, in order to classify the mineral, it 
 is necessary to reduce it into lime, and proceed in the 
 manner above described/ The time which such lime 
 takes to set, if it be measured very exactly, will alwavs 
 be sufficient to afford an approximate indication of its 
 place. 
 
 2k Twenty years ago we knew hardly a dozen 
 
 1 An exception must be made in favour of the Dolomites, with 
 the properties of which Mr. Vicat does not appear to have been 
 acquainted. Colonel Pasley found that the carbonate of magnesia 
 itself furnished an excellent water-cement; and in Borne experiments, 
 made on a small scale, I found that a paste of equal parts of the 
 hydrates of lime and magnesia calcined together set with great firm- 
 ness in a few hours, whence I infer the probability that some of the 
 magnesian limestones may be found to be useful in this way; but I 
 have as yet had no opportunity of making a direct experiment on 
 this subject. (Vide App. VI.) — Tr. 
 
 u Vide Note to Article 19. • Vide Articles 9, 10, II, and 12. 
 
1J CALCAREOUS MINERALS, ETC. 
 
 localities in France affording hydraulic lime. Now 
 ire are no longer able to reckon them. w Wheresoever 
 we have been sent to look for it, it has been met with, 
 oven in Brittany. The Departments of Lot, Lot and 
 Garronne, Tarn, Dordogne, Charente, Cher, Allier, 
 Xievre, the Yonne, Cote-d'Or, Ain, Isere, Jura, 
 Doubs, Upper Rhine, &c, &c, are abundantly sup- 
 plied with it. 
 
 w As an exemplification of the practical usefulness of the methods 
 described in this work, for recognising villi facility the minerals 
 capable of being applied to hydraulic purposes, I may state, that 
 whilst superintending the Department of Public Works in the 
 Northern Division of the Madras Presidency at Masulipatam, they 
 Mere the means of discovering an excellent water-lime superior 
 to the Aberthaw in setting power, which existed in abundance in 
 the imin< 'diate neighbourhood, but whose properties had been pre- 
 \iuii-ly altogether unknown. And there can be no doubt that these 
 valuable linns will be found plentifully in many other situations, 
 when Mr. Yicat's simple methods of recognising and estimating 
 their qualities are more generally understood. With this object the 
 ela<s of Indian calcareous minerals called '• cancars" seems to be 
 particularly worthy of experiment, some of them which have been 
 already analyzed exhibiting nearly the exact proportions a insti- 
 tuting the best cement.-, and others being alloyed in various ratios, 
 corresponding with the composition of water-limes of different quali- 
 ( )f these a valuable catalogue has been published by Mr. Prin- 
 sep : but it i< impossible to predict from it the value of the minerals 
 it describes, as cements, until the exact nature of the alloy in each 
 be determined. — Tr. 
 
CHAPTER II. 
 
 ON THE BURNING OF LIMESTONE IN THE LARGE WAY. 
 
 25. Limestone becomes lime on being deprived 
 of its carbonic acid, and of the water it contained, 
 whether hygrometrically or in combination. The 
 agent employed to effect this is heat. (App. VIII.) 
 
 26. With the same heat, the calcination is effected 
 with more ease and rapidity in proportion as the stone 
 is of a less compact texture, to the smallness in bulk 
 of the fragments into which it is reduced, and to its 
 being impregnated with a certain degree of humidity. 
 (App. IX.) 
 
 27. The contact of the air is not indispensable, 
 but it exercises a useful influence, especially in regard 
 to argillaceous limestone. Moreover, no limestone can 
 be converted into lime in a vessel so close as to render 
 the escape of the carbonic acid impossible. (App. X.) 
 
 28. Limestone which is pure, or nearly so, supports 
 a white heat without inconvenience ; n the compound 
 limestone, on the other hand, alloyed in the propor- 
 tions necessary to form hydraulic or eminently hy- 
 draulic lime, fuses easily. Its calcination demands 
 certain precautions : the heat ought never to be 
 
 ■ Under the intense heat of the hydro-oxygen blowpipe this 
 substance affords the brilliant light, the beautiful application of 
 which to the microscope is now so well known. — Tit. 
 
14 BURNING OF LIMESTONE [CHAP. 
 
 pushed bcvond the common red heat, the intensity 
 being made up for by its duration. 
 
 ■. The compound limestone, when too much burnt, 
 is lieavv, compact, dark-coloured, covered with a kind 
 of enamel, especially about the angular parts ; it 
 slakes with great difficulty, and gives a lime carbon- 
 ized and without energy ; sometimes it will not slake 
 at all, but becomes reduced, after some days exposure 
 to the air, to a harsh powder altogether inert. b 
 
 30. The pure and compound limestones when in- 
 sufficiently burnt, either refuse to slake, or slake only 
 partiallv, leaving a solid kernel, a kind of sub-carbo- 
 nate with excess of base, which possesses properties 
 of which I shall have to speak elsewhere. (App. XI.) 
 
 b This is called dead lime, and should be carefully distinguished 
 from the sub-c . -. or unburnt limes, mentioned in the next 
 
 paragraph. Mr. Andrews | Mechanics Magaiim . No. 126) notices 
 four c a s e s in which dead lime may be formed: 1st, when the lime- 
 - much alumina, and it has been heated so as to harden 
 the mass; 2nd. when the limestone contains silica, and it has been 
 strongly heated after the expulsion of the carbonic acid ; 3rd. when 
 the limestone is so strongly 1 i be in aosne measure narllrrt. 
 
 in which case the carbonic acid is frequently not entirely separated 
 from the central parts of the large lumps, and they of course 
 
 with acids ; Jth. when the Ihnestone n strongly heated after 
 the total separation of the carbonic acid, so that the lime neither .-plits 
 when water is added to it. nor does it i ffcr v c sc c with acids Tr. 
 
 c A snb-carbonate is a combination of one equivalent of 
 alkali with lest than a full equivalent of carbonic acid. Thus a 
 combination of one equivalent of lime, with half an equivalent of 
 carbonic acid (if such a compound could be formed'), would be a 
 snb-carbonate of lime. The meaning of the term equivalent, is the 
 definite proportion of acid required to neutralise exactly a given 
 quantity of alkali, or of alkali to neutralise a given quantity of acid. 
 
II.] IN THE LARGE WAY. 15 
 
 31. The calcining of calcareous minerals consti- 
 tutes the art of the lime-burner. According to situa- 
 tion, either firewood, faggots, brushwood, turf, or coal 
 is used. 
 
 32. It would be tedious, as well as useless, to de- 
 scribe in this place all the limekilns which have 
 been suggested or tried within the last few years. 
 I shall content myself with saying, that the forms of 
 interior most generally adopted are, 1st, the upright 
 rectangular prism (pi. I. figs. 1 and 2) ; 2nd, the cy- 
 linder (pi. I. figs. 3 and 4) ; 3rd, the cylinder sur- 
 mounted by an erect cone slightly truncated (pi. I. fig. 
 5) ; 4th, a truncated inverted cone (pi. I. figs. 7 and 
 S) ; 5th, an ellipsoid of revolution variously curvated, 
 or egg-shaped kiln. (PL I. figs. 7, 8, 11, and 12.) 
 
 S3. The rectangular kilns are in use in Nivernais, 
 and in the south of France : they burn in them, at 
 the same time, limestone and bricks. The limestone 
 occupies very nearly the lower half of its eapaeitv. 
 The upper is filled with bricks, or tiles, laid and 
 packed edgeways. 
 
 34. The cylindric kilns are principallv employed 
 upon works which consume a large quantity of lime 
 in a short time. They are termed " field-kilns" 
 (" fours de campagnc") ; their construction is expe- 
 ditious and economical, but precarious. Above a 
 pointed (" ogive") or oven-shaped vault, they raise, in 
 the form of a tower, a high stack of limestone, which 
 they enclose by a curtain of rammed earth, and sup- 
 Thus 22 grains of carbonic acid combine with, and exactly neutralise 
 28 grains of lime ; the equivalents of carbonic acid and lime, therefore, 
 are always in the proportion to one another of 22 : 28. — Tr. 
 
16 BURNING OF LIMESTONE [cnAP. 
 
 port outwardly by a coarse wattling, in which car 
 taken to leave an opening to introdi; tire be- 
 
 neath the vault. 
 
 '. The kilns of the third kind are constructed 
 in a solid and durable manner, like the four-sided 
 kilns : no bricks arc burnt in these ; the largest 
 stones occupy the lower part of the cylinder, the 
 smaller pieces and fragments are thrown into the 
 cone which surmounts it. 
 
 S'o. The kilns of the fourth and fifth kind u -; - 
 ciallv intended for burning with coal. 
 
 37. The interior wall of the kiln is generally built 
 with bricks, or other material unalterable by heat, 
 cemented throughout a thickness of from thirty-two 
 to forty centimetres (12 to 15 inches nearly), with a 
 mixture of sand and refractory clay beaten together. 
 
 3S. In the flare-kilns fed bv Iolts or brushwood, 
 the charge always rests upon one or two vaults built 
 up dry with the materials of the charge itself. Un- 
 derneath these vaults they light a small fire, which 
 they gradually incn - - they retire, in proportion 
 as the draught establishes itself, and gains force. ( ha 
 reaching the exterior they adjust the aperture at the 
 • if the kiln suitably, and then keep it constantly 
 filled with the combustible. The air which rushes 
 in, carries the flame to a distance over every point of 
 the vaults: it insinuates itself by the joints, and is not 
 Ion"" in extending the ineaudescence by degl the 
 
 highest parts. 
 
 There are some kinds of stone which the fire, 
 however well regulated, seizes suddenly, and causes 
 to flv with detonation : we cannot, without running 
 
II. j IN THE LARGE WAV. 17 
 
 the risk of spoiling the charge, use these for the 
 construction of the vaults and piers in loading the 
 kiln. In such a ease, we employ for that purpose 
 materials which arc free from such an inconvenience. 
 
 40. Practice can alone indicate the time proper for 
 the calcination. It varies with a multitude of cir- 
 cumstances, such as the more or less green, more or 
 less dry quality of the wood ; the direction of the 
 wind, if it favour the draft, or otherwise, &c. d The 
 master burners usually judge by the general settling 
 of the charge, which varies from A to J. In a kiln 
 of the capacity of from GO to 75 cubic metres, 6 the 
 fire lasts from 100 to 150 hours : every cubic metre 
 of lime consumes (on an average) 1.60 steres in fire- 
 wood, 22.00 steres in faggots, and 30 steres in fascines, 
 furze, or other brushwood/ (App. XII.) 
 
 41. In the coal kilns by slow heat, the stone and 
 coal are mixed. Of all the methods of burning lime, 
 this is certainly the most precarious and difficult ; 
 more especiallv when applied to the argillaceous lime- 
 stone. A mere change in the duration or intensity 
 of the wind, any dilapidation of the interior wall of 
 
 d General Treussart remarks concerning the burning of the 
 Obernai lime, that being calcined with wood, it is very difficult to 
 obtain a homogeneous result ; there are always lumps of lime which 
 are over-burnt, and others which are not sufficiently so. The lime- 
 burners, he adds, ought to keep up the calcination of their lime for 
 a longer period, but with a less intense heat; this would not con- 
 sume more wood, and a much belter result would be obtained. — 
 Tr. 
 
 e From 211.3 to 264.75 cubic feet— Tit. 
 
 f A stere is equal to one cubic metre, or 35.3 English cubic 
 feet. — Tr. 
 
IS BUSHING OF LIMESTONE [CHAP. 
 
 the kiln, a too great inequality in the size of the fin _- 
 ments, are so many causes which may retard or a 
 leratc the draft, and occasion irregular movements in 
 the descent of the materials, which become locked to- 
 gether, form a vault, and precipitate at one time the 
 coal, and another the stone, upon the same point ; 
 hence an excess or deficiency in the calcination. 
 
 .. Sometimes a kiln works perfectly well for many 
 weeks, and then all at once gets out of order without 
 nnv visible cause. A mere change in the quality of 
 the coal is sufficient to lead the most experienced lime- 
 burner into error. In a word, the calcination by 
 means of coal, and the slow heat, is an affair of cau- 
 tious investigation and habit. (App. XIII.) 
 
 1 o. The capacity of a furnace contributes, no less 
 than does its form, to an equable and proper calcina- 
 tion. There are limits beyond which we cannot en- 
 large it without serious evils. We have drawn and 
 marked in plate I., figs. 9, 10, 11, and \% the sections 
 of four kilns executed and tried in the Department of 
 the Maine and Loire, by Messrs. Ollivier Lrothers, 
 manufacturers of hydraulic limes. Number 9 has I 
 abandoned in consequence of producing lime always 
 
 much or too little burnt; number 10 ansv. \ 
 tolerably; numbers 11 and V2 ansvered perfectly. 
 (A,,,,. XIV.) 
 
 11. The bulk of coal burnt to produce a cubic 
 metre of lime, necessarily varies with the hardness 
 the limestone used ; but within narrow limits. A\ hen 
 not referring to the chalks, or friable marles, we cal- 
 dilate on an average upon three cubic metres of lime 
 from one of coal. 
 
II.] IN THE LARGE WAY. 19 
 
 45. The calcination of limestones presents other 
 important problems for solution ; but the reasonings 
 of the closet, unaided by experiment, will always be 
 insufficient in a matter of this kind. It is for this rea- 
 son, that we here abstain from the discussion of a 
 number of projects more or less ingenious, but wholly 
 theoretical. We must beg the reader nevertheless to 
 refer to the notes ; he will there find some details use- 
 ful to be known, when he is called upon to apply him- 
 self specially to the burning of lime. (App. XV.) 
 
 c Q 
 
CHAPTER III. 
 
 ON ARTIFICIAL HYDRAULIC LIMES. 
 
 4G. Six years have elapsed since the publication of 
 my first researches into this subject ; and already the 
 artificial limes have been applied to a number of 
 important works. The canals of Saint Martin and 
 Saint Maur made almost exclusive use of them. 
 Nearly a thousand cubic metres' 1 have been cm- 
 ployed within five years at the harbour of Toulon. 
 These limes have served for the fabrication of the bc- 
 ton b for the foundations of several bridges ; and their 
 consumption is increasing daily in Paris and its en- 
 virons. (App. XVI.) 
 
 47. We have no longer, therefore, to attend to la- 
 boratory experiments, but indeed to a new art, very 
 nearly arrived at perfection. 
 
 a Equal to 1307 cubic yards 11 cubic feet English. — Tr. 
 
 fc I had originally translated this word into our English term 
 "concrete;" but upon Further consideration, it occurred to me, that 
 that term i> applied by us to a substance so essentially different in 
 its nature and mode of preparation, although similar in its uses, that 
 it would be best to avoid confusion, by a distinctive appellation. 
 Beton, then, is a mass composed of hydraulic lime and rubble, in 
 which the lime is usually slaked precious to its mixture with the 
 Other ingredients, and the mass seta under water. In concrete, the 
 lime slakes offer mixture with the rubble, and the mass cannot be 
 immerged till after consolidation Tr. 
 
ARTIFICIAL HYDRAULIC LIMES. l 2 1 
 
 48. The artificial hydraulic limes are prepared by 
 two methods : the most perfect, but also the most ex- 
 pensive, consists in mixing with rich lime slaked in 
 any way, a certain proportion of clay, and calcining 
 the mixture ; this is termed artificial lime twice kilned. 
 
 4 ( J. By the second process, we substitute for the 
 lime anV very soft calcareous substance (such, for ex- 
 ample, as chalk, or the tufas), which it is easy to bruise 
 and reduce to a paste with water. From this a great 
 saving is derived, but at the same time an artificial 
 lime perhaps of not quite so excellent a quality as 
 by the first process, in consequence of the rather 
 less perfect amalgamation of the mixture. In fact, 
 it is impossible, by mere mechanical agency, to re- 
 duce calcareous substances to the same degree of 
 fineness as slaked lime. Nevertheless, this second 
 process is the more generally followed, and the results 
 to which it leads become more and more satisfactory. 
 (App. XVII.) 
 
 50. "We see that by being able to regulate the pro- 
 portions, we can also give to the factitious lime what- 
 ever degree of energy we please, and cause it at plea- 
 sure to equal or surpass the natural hydraulic limes. 
 
 51. We usually take twenty parts of dry clay, to 
 eighty parts of very rich lime, or to one hundred and 
 forty of carbonate of lime. d But if the lime or its car- 
 
 c " The artificial hydraulic limes manufactured at MeudoD under 
 my direction, by Messrs. Brian and Saint Leger, gained the gold 
 medal at the exhibition of the products of the useful arts in 1827*" 
 '—Original note* 
 
 d The SO parts of lime here mentioned, refer to the lime in the 
 unslaked condition, and the 140 parts to the uncalcined mineral. 
 
JJ ARTIFICIAL HYDRAULIC LIMES. [CHAP. 
 
 bonatc should already be at all mixed (with clay, Tu.) 
 in the natural state, then fifteen parts of clay will In- 
 sufficient. Moreover, it is proper to determine the 
 proportions for every locality. In fact, all clays do 
 not resemble one another to such an extent as to 
 admit of their beino* considered as identical : the fi: 
 
 o 
 
 and softest are the best. 
 
 59. There is at Meudon, near Paris, a manufactory 
 of artificial lime set on foot by Messrs. Brian and 
 Saint Leger. The materials made use of are, the 
 
 If the lime be slaked, the proportion should be increased to 110 
 parts. The mixture here described, is such as to produce the hy- 
 draulic times, whose properties are similar to the Aberthaw, the ana- 
 lysis of which, by Mr. Phillips (Annals Phil., new series, vol. viii. p. 
 72), shows it to correspond nearly with the proportions here recom- 
 mended ; as it consists of 86.2 of carbonate of lime to 11.2 clav, 
 (with 2.6 water and carbonaceous matter,) being at the rat.- <>t' 18.2 
 parts clay to IK) of the carbonate of lime. The eementa now 
 commonly in u.-e in England, are much quicker setting than 
 . and differ from them in In iing tmslaked. Tiny contain a 
 greater proportion of clay, but may be manufactured artificially 
 with equal ease, by combining such relative quantities of chalk, 
 <>r lime, and clay, as will suit the purpose intended. Parker's 
 :-t Cement, as analyzed by Sir Humphry Davy (Ure's Diction- 
 ary, art. Cement), contains 15 per cent of clay t<> 55 carbonate of 
 lime. The Yorkshire cement, 31 clay to 62 carbonate of lime. The 
 Sheppy, 32 clay to 66 carbonate of lime. And the Harwich, which 
 i- ■ quick* r netting cement, 47 clay to +9 carbonate of lime. (Prac- 
 tical Remarks on Cements, p. 32.) These facts may serve as a guide 
 towards the admixture of ingredients, for the formation of a com- 
 pound suited to our purpose, in any situation ; but for the exact 
 proportions, recourse moat be had to experiment in ercri/ case 
 when new materials are to be employed. In fact, so different may- 
 be the chemical properties of apparently similar materials, that no 
 vex <!• finite, or however Bnceessful in one locality, can 
 
III.] ARTIFICIAL HYDRAULIC LIMES. 23 
 
 chalk of the country, and the clay of Vaugirard, c 
 which is previously broken up into lumps of the size 
 of one's fist. A millstone set up edgeways, and a 
 strong wheel with spokes and felloes, firmly attached 
 to a set of harrows and rakes, are set in movement by 
 a two-horse gin, in a circular basin of about two 
 metres (six feet and a half English) radius. In the 
 middle of the basin is a pillar of masonry, on which 
 turns the vertical arbor to which the whole system is 
 fixed : into this basin, to which water is conveyed by 
 means of a cock, they throw successively four mea- 
 sures of chalk, and one measure of clay. After an 
 hour and a half working, they obtain about 1.50 metres 
 cube (nearly fifty-three cubic feet English) of a thin 
 pulp, which they draw off by means of a conduit, 
 pierced horizontally on a level with the bottom of the 
 basin. 
 
 53. The fluid descends by its own weight ; first 
 into one excavation, then into a second, then a third, 
 
 with safety be trusted to in another, as more than a clew for the 
 direction of similar experiments, applied to the new materials at our 
 disposal. For such trials the process of manufacture, and the choice 
 of clay, &c, arc explained in the text; and it is therefore merely 
 necessary to add, that when aiming at the production of a compound 
 similar to Roman Cement, it would be necessary to increase the dose 
 of clay to about that indicated by the composition of the materials 
 from which our cements are manufactured, and in which it varies, as 
 above shown, from one-third to one-half of tin whole. Particular 
 attention should he paid to the perfect amalgamation of the mate- 
 rials ; ami the degree of calcination best suited to it should he care- 
 folly observed, before attempting to imitate the process on the large 
 scale. — Tit. 
 
 e "A hundred parts of this clay consist of silica 03, alumina 
 oxide of iron 7, loss 2." — General Treussart, p. 63. 
 
964 ARTIFICIAL HYDRAULIC LIMES. [CHAP. 
 
 and so on to a fourth or fifth. These excavation- 
 communicate with one another at top. When the 
 first is full, the fresh liquid, as it arrives, as trail as 
 the supernatant fluid, flow over into the second exca- 
 vation ; from the second into the third, and so on to 
 the last, the clear water from which drains off into a 
 cesspool. Other excavations, cut in steps like the 
 preceding, serve to receive the fresh products of the 
 work, whilst the material in the first scries acquires 
 the consistency necessary for moulding. The smaller 
 the depth of the pans in relation to their superficies, 
 the sooner is the above-mentioned consistency obtained. 
 
 54k The mass is now subdivided into solids of a 
 regular form by means of a mould. This operation 
 is executed with rapidity. A moulder, working by 
 the piece, makes on an average five thousand prisms 
 a day, which will measure about six cubic metres 
 (211.8 cubic feet English). These prisms are ar- 
 ranged on drying shelves, where in a short time they 
 acquire the degree of desiccation and hardness proper 
 for calcination/ This may be effected by any one of 
 the methods described in the preceding chapter. At 
 Paris they employ a mixture of coke and coal, and 
 the common mode of burning by slow heat, rendered 
 necessary by that kind of combustible. 
 
 55. The artificial hydraulic limes are intended to 
 supply the place of the natural ones in those coun- 
 
 f "It i> in CCIMITJ that the prisms be thoroughly dried previous to 
 catenation, as experience shows, that if subjected to heat while re- 
 taining any mo istu re, it may deprive tin in ■hnOOt, if not rutin ly. of 
 their hydraulic properties." — Trmt6 *mr FAri <l< Fain <h U»<> M 
 tiers, $c, par h Coltmd Faiuourt J< Ckarleviih, p. 39. 
 
III.] ARTIFICIAL HYDRAULIC LIMES. 25 
 
 tries where the argillaceous limestone is entirely want- 
 ing. They are sold at Paris, at from seventy to 
 seventy-four francs per cubic metre. g In the country, 
 they may be had for forty francs, on an average, when 
 twice kilned, and will not come to more than thirty 
 francs, when they result from a mere mixture of 
 chalk and clay. (App. XVIII.) 
 
 s At the exchange of 25 francs for a pound sterling, this Mould 
 be at the rate of from £2. 2s. 10(7. to £2. 5s. 3d. per English cubic 
 yard. — Tr. 
 
CHAPTER IV. 
 
 THE SLAKING OF LIME. 
 
 First Metliod. 
 
 5C). Quick-lime, taken as it leaves the kiln, ami 
 thrown into a proper quantity of water, splits with 
 noise, puffs up, produces a large disengagement of 
 hot slightly-caustic vapour, 3 (these phenomena may 
 be more or less marked, App. XIX.) and mils into 
 a thick paste : in this state it is termed indifferently 
 (" chaux fondue" " chaux coulee" "chaux <unortie") 
 slaked lime. 
 
 57. This method is generally adopted, but they 
 abuse it strangely. They reduce the lime to a milky 
 consistency in a separate basin, whence it runs off into 
 a large trench. Thus drowned, it loses the greater 
 part of its binding qualities. 
 
 58. The rich limes, when slaked and brought to a 
 very thick pulp,- give from two to three volumes for 
 one. The poor limes, most of the hydraulic limes, 
 
 a The specific gravity of pure lime is 3.08. " So much heat i- 
 produced (in slaking it) that part of tin- water flies off in vapour. 
 If the quantity of lime slaked be great, the heat produced is suffi- 
 cient to set fire to combustibles. In this manner vessels loaded with 
 lime have sometimes been burnt. When gnat quantities of lime 
 are slaked in a dark place, not only beat but light also is emitt. I 
 Mr. Pelletier has observed." — Thomso7i's Chemistry, vol. i. pp. t35-(3. 
 
SLAKING OF LIME. &7 
 
 and all the eminently hydraulic limes, do not give, 
 under the same circumstances, more than from one 
 to one and a quarter, or one and a half at most. 
 
 59. Rich lime, at the moment of being quenched 
 with much water, sometimes slakes to dryness in cer- 
 tain parte of the vessel, to which the water reaches 
 in but small quantity. If we now suddenly throw a 
 fresh supply of water upon the parts which slake in 
 this manner, it causes a hissing resembling the immer- 
 sion of a red-hot iron in water; and what is remark- 
 able, the lime being numbed by this sudden aspersion, 
 afterwards falls to powder very imperfectly, and con- 
 tinues gritty. The colder the water thrown upon it, 
 the more marked is the effect, more especially with 
 the rich limes. When we wish to procure a slaked 
 lime of great fineness, (for whitewashing walls for 
 instance,) we should have a sufficient quantity of water 
 at first, to avoid the necessity of replenishing it at the 
 moment of effervescence : or rather, we should sup- 
 ply it insensibly round the dry pieces, which will take 
 it up spontaneously by aspiration. (App. XX.) 
 
 GO. All lime becomes effete, or difficult to slake, after 
 it has been acted on by the air : this fact is more 
 especially remarkable in the hydraulic limes, which 
 finally are brought to such a state, that they fall to 
 pieces in water, without exhibiting anything but a 
 slight disengagement of heat. 
 
 o"o 
 
 Second Met I toil. 
 
 61. Quick-lime, plunged into water for a few seconds, 
 and withdrawn before it commences to slake, hisses, 
 
'2S SLAKING OF LIME. [c'IIAT. 
 
 splits with noise, gives out hot vapours, (these phe- 
 nomena may be more or less marked,) and falls to 
 powder. It is then called slaked lime by immersion. 
 It may be kept a long time in this state, provided 
 that we shelter it from moisture. It does not a^ain 
 become heated on tempering it. (App. XXI.) 
 
 6*2. One hundred parts of rich lime slaked in this 
 manner, do not contain, on an average, more than 18 
 parts of water, whilst the hydraulic limes take from 20 
 to 35. This tact presents itself in opposition to the 
 phenomena exhibited by the ordinary mode of slaking. 
 63. The very rich limes, if we content ourselves 
 with breaking them roughly into lumps previous to 
 immersion, and leaving them on the ground to slake, 
 fall with difficulty to a very fine powder. More than 
 half is still left in solid lumps of the size of a pea, 
 and these, when once chilled, may remain in water a 
 long time without falling in it. This difficulty may 
 be avoided, by reducing the fragments of quick-lime, 
 before immcrging them, to the size of a walnut,* 
 and still more, by heaping them together immediately 
 after immersion in casks or large bins : the heat is 
 then concentrated; a great portion of the water, con- 
 verted into vapour on the first instant, being unable 
 to escape is taken up by the lime, which is thus 
 brought to a satisfactory state of division. 
 
 64. One volume of caustic rich lime measured in 
 powder, barely gives more than l.oO to I.70 of slaked 
 powder uncompressed. 
 
 b " It ia fouml by experience, thai one day's labour u sufficient for 
 bruising and immersing Four-and-twenty cubic feel of quick-time.'' 
 
 — Colonel Raucourt, i>. l(j(>. 
 
TV.] SLAKING OF LIME. 29 
 
 65. The hydraulic limes, under the same circum- 
 stances, give from 1.80 to 2.18. 
 
 Third Method. 
 
 66. Quick-lime, subjected to the slow and continued 
 action of the atmosphere, is reduced to a very fine 
 powder. During this natural slaking, there is a 
 slight disengagement of heat, but unaccompanied by 
 any sensible vapours. 
 
 67. The rich limes increase J- ths in weight, and give 
 a volume of 3.5-2 to one (of the quick-lime in powder). 
 The hydraulic limes take, on an average, but g-th of 
 water, and give a bulk of from 1.75 to 2.55 (the 
 powders are measured without compression, " tasse- 
 ment") : to obtain these results, it is necessary to 
 seize the moment when the pulverization is com- 
 plete, and by no means to operate in too damp an 
 atmosphere. 
 
 68. Of the three processes, the ordinary mode of ex- 
 tinction is that which most perfectly divides the rich 
 limes, and the hydraulic limes of all degrees, and con- 
 sequently, which raises their expansion to the highest 
 
 c Even with rich limes it appears, that the spontaneous extinc- 
 tion does not effect a perfect division ; so that, should it be thought 
 advantageous to adopt that method, in order to increase the. 
 binding quality of the lime, it would be desirable to obviate this 
 defect, and improve its qualities by mechanical subdivision. Ge- 
 neral Treussart makes the following observation, in reference to 
 common (not hydraulic) lime : " I shall add, that all the mortars 
 made with lime slaked in powder (by immersion) were very homo- 
 geneous, whereas those which were slaked by the air, exhibited in 
 their interior a multitude of white specks, which appeared to me to 
 
.30 BLAKING or li.mi:. [chat. 
 
 limit. Next in order in the same respects, the spon- 
 taneous mode of extinction is more suitable to the 
 rich, than the hydraulic, and eminently hydraulic 
 limes ; but vice versa in slaking bv immersion. 
 (A PP . XXII.) 
 
 G9. From these differences it ensues, that three 
 equal volumes of lime, in paste of the same consist- 
 ency, but slaked by different processes, contain nei- 
 ther the same quantity of lime, nor the same quantity 
 of water. (App. XXIII.) 
 
 7<). Every kind of lime, if exposed in its caustic 
 state to the contact of the air in a sheltered situation, 
 insensibly re-absorbs as much carbonic acid as is 
 necessary to saturate it d : the time required for this 
 change varies with the nature and the volume of 
 the lime. Is it rich ? ten months suffice, when we 
 spread it in beds of only m .0i2 c (rather more than 
 three-quarters of an inch) thick. After that lapse of 
 time, one hundred and ninety-one parts of it will be 
 composed as follows : — 
 
 Caustic lime IOC) 
 
 Carbonic acid 7 1 
 
 Water 17 
 
 In particles of lime which had absorbed carbonic acid. This was 
 • specially remarkabh on breaking the mortars." It is unnecessary 
 to point out how much this must have impaired the energy of thl M 
 mortars. — Tr. 
 
 d The quantity of carbonic acid regained from the atinosplu iv. 
 M ver amounts to the full saturating dose : and as it appeals to 
 depend upon a previous re-union with water derived from the atmos- 
 phere, (vide note to Art. 75,) it is most probable thai the time of 
 6uch absorption will be regulated essentially by the >tau of the wea- 
 
IV.] SLAKING OF LIME. 31 
 
 Is it hydraulic? In that case, under the same cir- 
 cumstances, the change is complete after the seventh 
 or eighth month. At that period, 16 ( J parts of it 
 will contain as follows : caustic lime combined with 
 one-fifth clay 100, carbonic acid 54, water 15. 
 
 71. All lime, when first slaked by immersion, and 
 then exposed to the contact of the air in a sheltered 
 situation, becomes gradually loaded with carbonic acid 
 and water, but only up to a certain point : the amount 
 of this change, as well as the time required for it, 
 varies with the quality of the lime. 
 
 72. One hundred and sixty parts of rich lime so 
 slaked, contain, after seven and a half months of expo- 
 sure (as before said), caustic lime 100, carbonic acid 
 36.15, water 23.85. 
 
 73. One hundred and sixty-nine parts of hydraulic 
 lime, under the same circumstances, contain, caustic 
 lime with one-fifth of clay 100, carbonic acid 44, 
 water 25. 
 
 74. After the period alluded to, the weight of the 
 powders does not sensibly increase further ; the ba- 
 lance will merely detect hygrometric changes, some- 
 times positive, sometimes negative. Water, however, 
 in which we may mix these powders, dissolves a small 
 quantity. 
 
 75. The evident consequence of these last results is, 
 that a sudden immersion robs the rich and hydraulic 
 limes for ever of the faculty of regaining, by a long 
 
 ther, and the humidity or otherwise of the climate in which the 
 experiment is made. — Tn. 
 
.'3 C 2 SLAKING OF LIME. [CHAT. 
 
 exposure to the air, the quantity of carbonic acid of 
 which they have been deprived by calcination. 
 
 70. In the work -yards, rich limes slaked by the 
 "ordinary" process, are preserved by placing them in 
 trenches nearly impermeable, and covering them over 
 with thirty to forty centimetres (11.8 to 15.7 inches) 
 of sand or fresh earth. (App. XXIV.) When slaked 
 by immersion, or spontaneously, they may be kept with- 
 out change for a tolerably long time, either in casks, 
 or under sheds, in large bins covered with cloths, or 
 with straw. (App. XXV.) 
 
 77* The hydraulic limes harden in a short time in 
 a trench (App. XXVI) : they cannot be kept long, 
 nor especially be much carried about, without very 
 sensible alteration, unless they be slaked by immer- 
 sion, and then secured in that state in casks, or sacks 
 of cloth. (App. XXVII.) One may, however, keep 
 a pretty large quantity in a caustic state for five or 
 six months, by adopting the following method. 
 
 78. We spread a layer of fifteen to twenty centi- 
 
 e It seems to be essential to the re-union of carbonic acid with the 
 
 lime, that the latter should have previously combined with its equi- 
 valent of water; fori found that stuccoes which had been hastily 
 formed with unslaked lime, got up with as little water as possible, 
 were, alter a couple of years' exposure, still in a caustic, state quite 
 close to the surface; while a similar stucco, composed with well- 
 tempered lime, would be neutralized by the carbonic acid of the air 
 to the depth of half or three-quarters of an inch in the same cir- 
 cumstances. This observation is also confirmed by an experiment 
 detailed by Dr. Henry (System of Chemistry, vol. i. p. 610) ; for he 
 states, that if a piece of dry quick -linn be passed into ajar of car- 
 bonic acid over mercury, no absorption whatever takes place. — Tr. 
 
IV.] SLAKING OF LIME. 33 
 
 metres (5.9 to 7-9 inches) thick, of the lime reduced 
 to powder by immersion, on the floor of the shed where 
 the supply is to be laid up : on thi3 layer we pile up 
 the quick-lime, packing it as close as possible. If 
 there be no planking, the sides of the heap are finished 
 in slopes, which are covered by a final layer of lime, 
 taken at the moment of its undergoing immersion ; this, 
 falling to powder, lodges itself amongst the interstices 
 of the lumps of lime, and covers it sufficiently to de- 
 fend it from the air and all damp. (App. XXVIII.) 
 
 i) 
 
CHAPTER V. 
 
 OF THE HYDRATES* OF LIME (.\PP. XXIX), OR THE 
 SOLIDS RESULTING FROM THE SIMPLE COMBINATION 
 OF WATER AND LIME. 
 
 79. The study of these substances would be attended 
 with but little interest, if it were not linked in its re- 
 sults to facts most important in the history of mortars. 
 
 80. Numerous preliminary trials have shown, that 
 the quantity of water employed in slaking the lime 
 exerts a powerful influence on the hardness of the 
 hvdrate which results. And this is easily under- 
 stood. Too little water fails to bind the mass ; an 
 excess swells out the stuff, which remains light, 
 porous, and friable, if it does not shrink propor- 
 tionably in drying. Plaster b mixed thin, or stiff, 
 exhibits a remarkable instance of this fact. 
 
 81. The pasty consistency which produces the 
 greatest hardness, is at once ductile and firm. We 
 have given it the name of " clayey," because, in fact, 
 we can compare it to nothing better than clay which 
 is in a state of readiness for the manufacture of 
 potterv. It is this kind of consistency which we con- 
 
 * A hydrate is a compound of water chemically united with anv 
 substance. The hydrate of lime consist* of about twenty-eight parts 
 by weight of lime to nine of water. This compound i> formed by 
 tin- proeea of slaking. — Tr. 
 
 b Plaster of Paris is here meant. — Tn. 
 
HYDRATES OF LIME. 35 
 
 stantly gave to the pastes of the hydrates made use of 
 in our experiments. 
 
 Action of the Air on Hydrates. 
 
 82. Different limes prepared in this manner, and 
 exposed in the form of quadrangular prisms to the 
 action of the air during one year, have furnished the 
 following results : — 
 
 1st. The carbonic acid contained in the atmosphere 
 attacks the hydrates, fixes itself in them insensibly, 
 and carbonises them ; its influence extending from the 
 surfaces towards the centre. The thickness of the 
 coats thus carbonised, amounts after a year to not 
 more than six millimetres (.236 inches, Tr.) for hy- 
 draulic limes, and to two or three (.07S inches to .118 
 inches, Tr.) for the rich limes. We may convince 
 ourselves of this, by making sections of the prisms 
 in different directions by means of a small spring saw. 
 The coloured limes exhibit a band enveloping them, 
 which is distinguished from the interior by a deeper 
 tint. This tint is owing to the oxidation of the iron. 
 No appearance of this kind is observed with the 
 hydrates of white limes ; but on applying a- slightly 
 moistened test-paper to the sections, we have at once 
 an evidence of the breadth of the carbonated parts. d 
 
 c " The consistency of a good mortar should be such as to be 
 capable of supporting, without very sensible depression, an iron 
 necdlo of a line diameter loaded with a quarter of a pound." — Rau- 
 court sur let Jlortiers. 
 
 d This operation, however, although simple, is difficult to perform; 
 for the whole sectional surface being hidden by the test-paper, the 
 eye is deprived of the comparison between the operation of those 
 parts which affect it and those which have no action. At the same 
 
 D Q 
 
36 HYDRATES OF LIME. [CHAP. 
 
 83. The annual progress of the carbonic acid is 
 maintained with decreasing rapidity. In fact, the 
 greater the distance the part acted on by the car- 
 bonic acid is from the surface, the more difficulties 
 docs the regenerating principle meet with in reaching 
 it. These difficulties further vary with accidental 
 circumstances, and with the more or less compact 
 texture of the surface. (App. XXXI.) 
 
 S 1 . 2nd. The hardness acquired by the hydrates, 
 varies with the mode of slaking made use of. The 
 three common processes bear the following relation of 
 superiority to one another with regard to rich limes: — 
 1st, Ordinary extinction ; l 2nd, Spontaneous; '3rd, By 
 immersion. With regard to the hydraulic and emi- 
 nently hydraulic limes, that order of superiority be- 
 
 time, that the difficulty of closely approximating the uneven surface 
 of the cement to the test-paper, more especially in coarse mortars 
 containing gravel, makes the effect, even of the caustic portion, \< ry 
 irregular and undefined; bo that it i> almost impossible to fix the 
 line of demarcation with tolerable exactness, putting measurement 
 almost out of the question. 
 
 The method I have been in the habit of adopting, and which 
 su gge s te d it-elf to me at the time I first noticed the phenomenon 
 alluded to in the text, will be found more easy in practical application, 
 and satisfactory in its results. It consists in merely detaching a frag- 
 ment of the mortar to be examined, and immersing it in a neutral me- 
 tallic solution, containing any dark-coloured oxide, which will be pre- 
 cipitated bv caustic lime. The superior affinity of the lime for the acid 
 which is combined with the metallic oxide, immediately decomposes 
 the compound, and tin' oxide attarhfin itself to the surface; whereas 
 no action takes place on those part- which have been acted on by the 
 air, the lime being rendered powerless by union with carbonic acid. 
 I found the most convenient test to be a fresh prepared solution of 
 the protosulphate of iron (green vitriol), which deposits the dark 
 
V.] HYDRATES OF LIME. S"/ 
 
 comes, 1st, Ordinary extinction ; 2nd, By immersion ; 
 3rd, Spontaneous. 
 
 85. On referring to what has been said in Chapter 
 IV., we see without difficulty, that the order of rela- 
 tive hardness is absolutely the same as that of their 
 expansion ; that is to say, the method of extinction 
 which reduces the lime to the finest state, is also that 
 which gives the hydrates the greatest strength ; a 
 result in conformity with this principle, that the 
 cohesion of a compound ought to be in proportion to 
 the tenuity of its particles, since they can then arrange 
 themselves mutually in the most intimate contact. 
 
 86. On consulting the tables in which the experi- 
 ments are recorded, it is easy to deduce the following 
 conclusions, which are a sequel to the preceding ob- 
 servations : — 
 
 1st. Certain very rich limes, free from colour, are 
 capable of forming, by mere union with water, bodies 
 as hard as a number of natural minerals. 
 
 green protoxide of iron ; but I have also made use of many other solu- 
 tions and substances with very excellent effect. Some of these are, 
 the bichloride, and the proto, and pernitrates of mercury, producing 
 bright yellow, and brown, or black precipitates, the nitrate of silver, 
 black. Also the infusion and tincture of nut-galls, or of the seed- 
 vessels of the Terminalia chebulica (one of the mirabolans), a plant 
 common in India, which gives a dark green colour (with a strong 
 infusion), in a short time turning to chocolate. With the solution of 
 green vitriol the action is immediate, and when applied to the fresh 
 broken surface of a fragment (not less than half an inch to an inch 
 in thickness, and from six to twelve months old) of a light-coloured 
 plaster, the materials of which have been well incorporated, the 
 separation will be very clearly and beautifully exhibited, the parts 
 acted on by the atmosphere being accurately defined, by a white band 
 surrounding the darker-coloured centre. (Vide A pp. XXX.) — Tk. 
 
38 HYDRATES OI LIME. [CHAP. 
 
 2nd. The carbonic acid diffused through the atmos- 
 phere increases, with age, the hardness of those bodies 
 on which it fixes itself. 
 
 3rd. The hydraulic limes of all kinds, more especi- 
 allv those which are strongly coloured by iron, cannot, 
 by mere union with water, form any but bodies which 
 are light, and of but moderate hardness. 
 
 lth. The carbonic acid augments their hardness 
 also, but never to such a degree as to raise it to an 
 equality with that which it gives to the hydrates of 
 the rich and white limes. 
 
 Action of Water on the Hydrates. 
 
 87. Water dissolves those parts of the hydrates of 
 rich lime, which are not combined with carbonic acid, 
 whatsoever may be their cohesion. 6 
 
 88. If from the same rich lime, we make, by the 
 three common processes of extinction, three hydrates 
 of the same stiff consistency, and in every respect 
 exactly alike ; and if we immerse them immediately 
 in pure water, they will absorb, in a given time proper 
 to each, a certain quantity hereafter specified, viz. : — 
 
 S9. A thousand parts of the hydrate made by the 
 
 c When water contains carbonic acid associated with it, which it 
 almost invariably does, it is then capable of dissolving the carbonate 
 of lime. Tins operation takes place extensively in Nature, when 
 the superficial waters of the earth, in filtering through calcareous 
 strata, carry with them carbonate of lime in solution, which is de- 
 posited in recesses and caverns, in the form of stalactites. The same 
 effect may 1»< observed underneath the arches of some bridges; 
 though it i- probable that, in this case, the lime at first carried down 
 is dissolved in the caustic state. — Tit. 
 
V.] HYDRATES OF LIME. 39 
 
 first process, will after one month take forty parts of 
 water, which is the limit of saturation. 
 
 90. A thousand parts of the hydrate made by the 
 second process, will after two and a half months take 
 one hundred and eight parts of water, which is the 
 saturating limit. 
 
 91. A thousand parts of the hydrate made by the 
 third process, will after two and a half months take 
 two hundred and forty-six parts of water, which is 
 the limit of saturation. 
 
 92. The duration of the operation depends upon 
 the mass of hydrate immersed. When we place the 
 materials for experiment in an impermeable vessel, of 
 such a kind that a very small quantity of water suf- 
 fices to cover it, then the lime dissolved by it, and 
 which it is necessary to take into account, forms only 
 a very minute fraction of the total quantity of the 
 hydrate. 
 
 93. It evidently results from the preceding compa- 
 risons, that the deficiency in expansion which accom- 
 panies the use of the second and third processes of 
 extinction, enables the same lime to be reduced to a 
 paste at first, with a much smaller quantity of water 
 than is necessary to its complete saturation ; but we 
 also see that they retain the faculty of completing the 
 dose by an internal and progressive action, yet unac- 
 companied by any change, except an alteration of 
 density, and by consequence, of hardness ; for after the 
 cessation of the action of which we have spoken, no 
 sensible alteration of volume can be perceived/ 
 
 f General Trenssart details an experiment which affords a very 
 easy demonstration of this fact : — Two mixtures of a pulpy consist- 
 
10 HYDRATES OF LIME. [CHAP. 
 
 9 4. This observation is of much importance : wo 
 shall take care to avail ourselves of it when neces- 
 sary. 
 
 95. We have already, in the first chapter, considered 
 the hydrates of hydraulic limes immersed in the con- 
 dition of paste, and the hardness they acquire in con- 
 sequence of this immersion. It remains now for us 
 to point out that this hardness, as well as the quick- 
 ness of setting, is influenced by the method of ex- 
 tinction, in a manner the more remarkable the less 
 energetic the lime is. The order of pre-eminence of 
 the three modes of extinction is not constant : it is 
 the same for the rich, and slightly hydraulic limes ; 
 for the hydraulic, and eminently hydraulic limes, the 
 order is the same as that given in treating of the 
 action of the air. 
 
 96. The hydrates of the hydraulic, and eminentlv 
 hydraulic limes, immersed in the condition of very soft 
 pastes, reject a portion of the superabundant water 
 they contain, and become solid : in the condition of 
 very stiff paste, on the contrary, they absorb an addi- 
 tional quantity, solidify more quickly, and in time 
 acquire a degree of hardness, which lime immersed in 
 the soft state never attains. 
 
 97* All hydraulic lime which has hardened in the 
 
 r iky were made, the one composed of a rich slaked lime, which had 
 been tempered for four years, and the other, of lime fn >h alaked 
 as it came from the kiln, both mixed with water. In the course of 
 time, the second mixture became very thick and stiff, the first re- 
 taining it< fluidity unaltered: water was added to dilute the thick- 
 ened one to the same consistency as the other ; and it again, though 
 more slowly, bt scame agglutinated; and this wan repeated several 
 times, before it. could retain it> fluidity unaltered like the first. — Tn. 
 
V.] HYDRATES OF LIME. 41 
 
 air, may afterwards be immersed with impunity, with- 
 out the water dissolving any sensible quantity of it. 
 
 9S. The hydrates of the rich limes are not of any 
 great benefit in the art ; (App. XXXII.) the prin- 
 cipal difficulty consists in the shrinkage which the 
 mass undergoes on drying in the air, more especially 
 when it has been slaked by the ordinary process. 
 When we mould it into prisms, of which the dimen- 
 sions do not exceed those of a very small brick, and 
 if we place them at intervals on an area to which they 
 do not adhere, the mass concentrates itself without 
 obstacle, and the process of drying and solidification 
 proceeds tolerably well ; nevertheless the prisms be- 
 come covered with a slight efflorescence, arising from 
 small portions of the surface which have been unable 
 to participate in the general movement in shrinking. 
 But when the dimensions are enlarged, when the forms 
 become complicated, and the use of moulds becomes 
 necessary, then the material is cramped, the paste 
 adheres to the sides, cracks show themselves, and we 
 get nothing but fragments. Beating is not of any 
 avail whatever. 
 
 99. The shrinkage is the more considerable, the 
 richer the nature of the lime employed, and the more 
 it has been swelled in slaking/ But, if we could con- 
 
 8 It appears, that when slaked with much water, the lime shrinks 
 on drying, because it is incapable of combining with the fluid which 
 forms it into paste ; and its particles must therefore necessarily ap- 
 proach one another when it is withdrawn from between them by 
 evaporation. It shrinks least when made into paste after bring 
 slaked by exposure to the air, for then all the interstitial fluid may 
 be solidified by the lime itself, and it is probable that the expansion 
 of the particles of lime during this absorption tills up the spaces 
 
1 J HYDRATES OF LIME. 
 
 fine ourselves to simple forms, we might succeed in 
 manufacturing at slight cost, with the rich and very 
 white limes, small slabs, which being susceptible of a 
 good finish, and polished on a fine free-stone, would 
 imitate handsome white marble, and might be applied 
 to many uses. 
 
 100. The hydraulic mortars in the condition of 
 hydrates, can only be employed with success under 
 ground, or in the water, whether it be in puddling, or 
 in masses of beton. But they will not succeed better 
 than the mortar which is obtained by mixing them 
 with common sand ; so that it would be very bad policy 
 to neglect that means of at least doubling the bulk of 
 the material. 
 
 left by the abstraction of the water. (Art. 93.) It must not be for- 
 gotten, that the remarks contained in this Chapter refer merely to 
 the solids formed of lime and water, without the admixture of sand 
 or other ingredient. — Tit. 
 
SECTION II. 
 
 CHAPTER VI. 
 
 OF THE MATERIALS WHICH ARE ADDED TO LIME, IN THE 
 FORMATION OF MORTARS OR CALCAREOUS CEMENTS. 
 
 101. These materials are, 1st, The different kinds 
 of sand, properly so called : 2nd, Arenes : 3rd, Psam- 
 mites : a 4th, Clays : 5th, Volcanic or pseudo-volcanic 
 products : 6th, Artificial products arising from the 
 calcination of the clays, the arenes, and the psam- 
 mites ; and the rubbish and slag of manufactories, 
 forges, glasshouses, &c. 
 
 INGREDIENTS OF MORTAR. 
 
 Sand. 
 
 102. The granitic, schistose, and calcareous rocks, 
 the free-stones ("gres"), &c, &c, reduced to the state 
 of hard and palpable grains, either by the agitation 
 of water, or by spontaneous disaggregation, give birth 
 to the various kinds of sand. We distinguish them 
 from powders, by their at once falling to the bottom 
 
 a These terms are explained in Articles 109, 110, 111, and 
 112.— Tu. 
 
i 1 MATERIALS IN THE [cHAl\ 
 
 when thrown into limpid water, and that without 
 altering- the transparency in a sensible degree. b 
 
 103. The disaggregation of rocks is often accom- 
 panied bv a decomposition which produces a powder. 
 This powder renders the sand "rich," or, in other 
 terms, susceptible of a certain cohesion, when tempered 
 with water ; washed by rains and currents of water, it 
 on freed from the pulverulent particles, and is 
 deposited pure in the beds of rivers. 
 
 l"i. This purity is generally changed near the 
 mouths of streams, and in the small rivulets whose 
 tributaries flow over a bed of clay or mould ; the 
 sand mixes with vegetable debris and animal matters, 
 and becomes "loamy." The particles composing sand 
 faithfully represent those of the rocks whence they are 
 derived. The granitic regions furnish quartz, felspar, 
 and mica ; and the volcanic regions, lavas of all kinds. 
 The tabular-shaped sands, whose particles are tender, 
 are furnished by the schistose mountains ; it is difficult 
 for them to be transported far without being reduced 
 to powder. 
 
 I 1 15. The calcareous sands are the least common. 
 This very probably arises from the circumstance, that 
 
 b The specific gravity of siliceous or quartzose sand I found, by a 
 mean of various experin. _• . which is the same as that 
 
 of quartz. A cubic foot of thi*. if it wen solid, would therefore 
 
 I _ e a cubic foot of wat . a 1000 ov. 
 
 But I found that, when measured in the way usually adopted in ap- 
 portioning the ingredients of mortar, (in which case the sand, which 
 was usually rather damp from being fr _ as thrown into the 
 
 measure, but not beaten or compressed.) a cubic foot of i: 
 only 75 lbs. Hence the voids or spaces between the grains were 
 rather more than equal to the bulk of the sand itself, when mr-n ly 
 thrown together. The same method may be employed to ascertain 
 
VI.] FORMATION OF MORTARS. 45 
 
 there are but few rivers but what take their rise from 
 primitive summits, or such as are composed of primitive 
 elements. The calcareous rocks, besides, are not sus- 
 ceptible of that kind of disaggregation wdiich could 
 be called granitic ; for if they be of a soft kind, they 
 merely produce powder ; if hard, scaly splinters. 
 
 10(5. The partial and secondary revolutions of the 
 globe, have occasioned immense deposits of sand in 
 situations where now neither brooks nor rivers flow : 
 these are the fossil sands ; and they should be carefully 
 distinguished from the virgin sands, which are still in 
 their original scite, and have not been operated on 
 by the waters. 
 
 107. The fossil sands generally exhibit a more an- 
 gular grain than the sea or river sand ; but in other 
 respects they are the same elements, sometimes pure, 
 sometimes coloured by ochres, &c. 
 
 108. Among the fossil sands is one very remark- 
 able, the arene. Its peculiar properties entitle it to 
 a distinct place in our category. 
 
 the density of sand in other conditions ; and it is equally applicable 
 to any mixture of gravel or rubble and sand, if the pebbles and 
 grains contained in it do not vary much in specific gravity from that 
 of flint and other siliceous minerals, which is rarely the case. The 
 knowledge derived from this experiment is of considerable import- 
 ance, in reference to the established principle, that the best propor- 
 tion of lime or other cementing matter in a mortar, is that which 
 exactly fills up the voids between the particles of sand with which it 
 is mixed, and which is thus obtained. For the difference between the 
 weight of a cubic foot of the materials, when condensed as much as 
 possible, and 162^ lbs., will indicate the proportion which remains 
 to be filled up with cementing matter ; which is the least dose (sup- 
 posing the whole of it to be active) that will bind them firmly toge- 
 ther, but beyond which as little should be added as possible. — Tr. 
 
46 MATERIALS IN THE [CHAP. 
 
 INGREDIENTS OF CEMENTS. 
 
 Arenes. 
 
 109. This is a sand, generally quartzose, with very 
 irregular, unequal grains, and mingled with yellow, 
 red, brown, and sometimes white clay, in propor- 
 tions varvinor from one to three-fourths of the whole 
 
 volume. 
 
 110. The arene almost always occupies the sum- 
 mits of the rounded and moderately-elevated hills : it 
 sometimes constitutes entire hillocks ; frequently it in- 
 terposes itself in large veins and seams in the clefts of 
 calcareous rocks: it belongs essentially to alluvial soils. 
 (App. XXXIII.) 
 
 Psammites. 
 
 111. We apply this term to an assemblage of the 
 irrains of quartz, schist, felspar, and particles of 
 mica/ agglutinated by a variable cement. The varie- 
 ties of these are very numerous ; those which in ap- 
 pearance strongly resemble the free-stones, and sili- 
 ceous breccias, 1 belong to the class of rocks whose dis- 
 aggregation furnishes sand properly so called. But the 
 psammites, which are slaty, of a yellow, red, or brown 
 colour, fine grained, unctuous to the touch, producing 
 
 Sc]ii>t" i- the German term for slate : felspar is "a simple 
 
 mineral, which next to quartz constitutes the chief material of 
 
 | Lyell's Geology.) " Mici is a simple mineral, having a 
 
 shining silvery surface, and capable of being split into very thin 
 
 elastic leaves or scales." (Ibid.) It is often mistaken for talc, which 
 
 • mbles. — Tr. 
 
 d An a-s( mblage of angular fragments glued together by any 
 
 cement is called a M breccia." — Tr. 
 
VI.] FORMATION OF MORTARS. 47 
 
 a clayey paste with water, form a distinct species, and 
 one which merits our attention. 
 
 112. These last belong to the primitive schistose 
 formations ; they do not, and cannot exist, except " in 
 situ ;" they are found in beds or veins, forming- part 
 of the schist of which they are merely a decomposi- 
 tion. The Department of Finisterre, in the neighbour- 
 hood of Carhoix and Brest, furnishes it in abundance. 
 (App. XXXIV.) 
 
 Clays. 
 
 113. Clays are earthy substances variously coloured, 
 fine, soft to the touch, which diffuse in water with fa- 
 cility, forming with it a paste, which, when kneaded to a 
 certain consistency, possesses unctuosity and tenacitv, 
 and may be drawn out and kneaded in every direction 
 without separating. The clayey paste, when dried, 
 retains its solidity, hardens in the fire, &c. 
 
 114. Clays are essentially composed of silica and 
 alumina : these two substances are adulterated by 
 the presence of the oxide of iron, the carbonates of 
 lime and magnesia, sulphuret of iron, and of vege- 
 table combustible matter partly decomposed. 
 
 115. The clays are separated into four classes: 
 viz., the refractory, which resist, without melting, 
 the heat of the porcelain furnaces (1 40° AVedgwood) ; 
 the fusible clays ; the effervescing, or clayey marls ; 
 and, lastly, the ochrey clays, coloured red or pure 
 yellow by the oxide of iron. 
 
 116. The position of clays is very varied: we find 
 them as veins in primitive formations ; in hillocks, on 
 
IS MATERIALS ix THE [chai\ 
 
 the confines of the primitive chains ; in horizontal 
 beds, or layers, in the secondary formations ; in threads, 
 thin veins, or infiltrations, in chinks and hollows of 
 calcareous masses ; lastly, in volcanic regions. There, 
 their formation is attributed to the decomposition of 
 the compact lavas, and perhaps also, with some proba- 
 bility, to miry eruptions. 
 
 117. AVe shall confine ourselves to these short ob- 
 servations ; as the mineralogical history of the clays 
 cannot be entered upon here. On this subject, the 
 reader may consult the excellent article " Argile" of 
 M, Brogniart. (Dictionnaire d'Histoire Xaturclle.) 
 
 Natural Pouzzolanas, or Volcanic and Pseudo- 
 Volcanic Products. 
 
 IIS. Pouzzolana, properly so called, is a volcanic 
 matter, pulverulent, of a violet red colour, first dug 
 out of the earth by the Romans near the town of 
 Pouzzol, not far from Vesuvius. 
 
 119. The environs of Rome furnish it equally. 
 The naturalist Faujas de St. Fond, has found it in 
 France, on the extinct volcanoes of Vivarais. There 
 are few regions exposed to igneous agency which are 
 destitute of it. But it presents itself under very dif- 
 ferent physical appearances ; sometimes pulverulent, 
 sometimes in coarse grains, often in slag, pumice, tufa/ 
 
 e " Tuff, or tufa, volcanic. An Italian name for a variety of vul- 
 canic rock of an earthy texture, seldom very compact, and composed 
 of an agglutination of fragment! of scoriae and loose matter ejected 
 from a volcano." — Li/clfs Gcolor/i/, 5th edit., vol. i. p. 461. 
 
VI.] FORMATION OF MORTARS. 49 
 
 &c. Its colour, which is generally brown, passes to 
 yellow, grey, and black/ 
 
 120. We shall, in the rest of this work, comprehend 
 under the name of pouzzolanas, the pseudo-volcanic 
 products arising from the ignition of coal-pits, such 
 as the tripolis, calcined sandstones, clays, &c. 
 
 121. Of these substances, some appear to have been 
 exposed to a very high temperature ; others seem to 
 have been only slightly scorched. Many appear to 
 have been re-acted on, and modified anew by the 
 heat, or altered by the effect of a very slow sponta- 
 neous decomposition. These changes have deter- 
 mined in the constituent principles a union more or 
 less close, and consequently more or less difficult to 
 overcome by chemical agents. 
 
 122. The pouzzolanas are essentially composed of 
 silica and alumina, united with a small quantity of 
 lime, potash, soda, and magnesia. Iron is associated 
 with them mechanically, in the magnetic state. 
 
 123. The mineralogical history of the pouzzolanas 
 will be found in the works of Desmarest, Faujas-de- 
 Saint-Fond, and other authors. (App. XXXV.) 
 
 Artificial Pouzzolanas. 
 
 121. Under this denomination we shall include the 
 clays, arenes, psammites, and schists, properly cal- 
 
 f The only preparation this material undergoes previous to use, is 
 that of pounding, or grinding and sifting, whereby it is reduced to 
 powder; in which state it is beaten to a proper consistency with a 
 due proportion of lime. A specimen of it analyzed by M. Berthier 
 contained, silica 44.5, alumina 15, lime S.8, magnesia 4.7, oxides of 
 iron 12, soda 4, potash 1.4, water 9.2, in a hundred parts. — Tr. 
 
.00 MATERIALS IN 1111. [CHAP. 
 
 cined ; smithy ^lasj, the refuse of the combustion of 
 
 turf and coal, and pounded earthenware ; and, lastly, 
 tile and pot shards/ 
 
 125. Such is a brief account of the substances 
 which unite with lime in forming calcareous cements. 
 But these bodies, although generally composed of 
 silica and alumina, are far from acting in a uniform 
 manner ; some bind well with the rich limes, others 
 with the slightly hydraulic, or eminently hydraulic 
 limes ; and of these several mixtures, some resist the 
 effects of the air, the weather, and the action of 
 water ; others only retain their solidity while im- 
 mersion continues : and airain, there are some which 
 
 I Mr. Smeaton tried powdered forge-scales, such as fall from iron 
 at a smith's anvil, with excellent effect. Also the sittings of the iron- 
 stone after calcination at the iron-furnaces, called " minion." which 
 were ground in a mill previous to mixture with lime. He considered 
 the forge-scales, when well powdered, and sifted clean from dirt and 
 glassy slag, to be equivalent to as much pouzzolana, or tarras ; rust 
 of iron, or iron-ore burnt, powdered, and sifted, to be equivalent to 
 minion ; and each of these last to about half the quantity of pouzzo- 
 lana, or tarras. In the construction of the new Docks at Sunder- 
 land, which I visited during their progress, in May I8S5, I found 
 that the cement used there, was a mixture of two parts of lime 
 (which was obtained from a blue species of limestone, probably 
 lias) and one part of the ground slag from the iron-founderies in 
 the neighbourhood. I examined some of the lumps of slag lying 
 about ; they seemed to contain much iron, either in the metallic 
 state, or as the protoxide. (Vide note to Art. 138.) Before being 
 applied to use, they are ground on a cast-metal bed to a very fine 
 powder j and I was informed that the ashlar work mi mostly all 
 united with a cement of this powdered slag and water, without any 
 admixture of lime. This was kept dry for a couple of days, in 
 which time it set ; and it afterwards indurated slowly, becoming of a 
 Monv hardness. — Tr. 
 
VI.] FORMATION OF MORTARS. 51 
 
 lose all their cohesion as soon as they are immersed, 
 &c, &c. 
 
 126. To what are these differences owing? They 
 can neither be accounted for by the physical character, 
 nor chemical composition of the different varieties ; (if 
 we confine ourselves to determining the number and 
 the proportions of the constituent principles;) for in 
 this last respect, most of them will be found to be 
 identical. 
 
 f S 
 
CHAPTER VII. 
 
 OF THE QUALITIES OF THE DIFFERENT MATERIALS 
 WHICH ARE JOINED WITH LIME IN THE FABRICATION 
 OF MORTARS, OR CALCAREOUS CEMENTS. 
 
 127. In what follows, we shall term every sub- 
 stance " very energetic" which, when kneaded to a 
 clayey consistency with very rich lime, slaked by the 
 ordinary process, forms a cement or mortar capable, 
 1st, of setting from the first to the third day after im- 
 mersion ; 2nd, of acquiring after one year the hard- 
 ness of good brick ; 3rd, of yielding a dry powder 
 under the spring-saw (a little saw whose blade is a 
 clock-spring). 
 
 128. 2nd. We shall call merely " energetic" every 
 substance which, under the same circumstances as 
 before, will produce a cement or mortar capable, 1st, 
 of setting from the fourth to the eighth day ; 2nd, of 
 acquiring, after a year's immersion, the hardness of a 
 very soft stone ; 3rd, of yielding a moist powder with 
 the spring-saw. 
 
 129. 3rd. We shall call every substance "feebly 
 energetic" which, under the same circumstances as 
 before, produces a cement or mortar which, 1st, will 
 set from the tenth to the twentieth day ; 2nd, which 
 acquires, after a year's immersion, the hardness of dry 
 soap ; 3rd, which clogs the saw. 
 
QUALITY OF MATERIALS, ETC. 53 
 
 130. 4-th. Lastly, we shall say that a substance 
 is " inert" when its presence in proper proportions 
 in rich lime in paste makes no alteration whatever 
 in the manner in which the lime would behave, if 
 immersed without mixture. 
 
 131. In the first three cases, what rigidly charac- 
 terizes the substance, is the hardness acquired at the 
 period fixed; for the "time of set" may sometimes 
 transgress the prescribed limits. In fact, we know 
 hydraulic cements which set on the third or fourth 
 day, without ever attaining the hardness of soft stone ; 
 and others, on the contrary, which become very hard, 
 although sluggish at first. 
 
 1S2. These definitions being fixed, we establish as 
 the result of experiment, 
 
 1st. That the sands, properly so called, are gene- 
 rally "inert" substances. 
 
 2nd. The arenes, the psammites, and the clays, are 
 generally " feebly energetic," and rarely " energetic " 
 materials.* 
 3rd. The pouzzolanas, natural or artificial, may 
 
 a I have met with a clay of a common kind which, when pow- 
 dered in its crude state, and made into a stiff paste with rich slaked 
 lime, set under water in ten days ; but it soiled the finger on first 
 hardening, was meagre and gritty, and did not possess much co- 
 hesion. In five months and ten days, however, it had very much 
 improved, and seemed to promise to turn out an excellent cement. 
 I was, however, unfortunately compelled to abandon it at that time, 
 and have been unable to learn its subsequent progress. Its hard- 
 ness was then indicated by a depression of .2125 inch, when tried 
 by an instrument similar to that used by Mr. Vicat, but no part of 
 the surface was removed previous to subjecting it to the blow of the 
 proving needle. — Tr. 
 
54 QUALITY OF MATERIALS, ETC. [CHAP. 
 
 be "very energetic," or "simply energetic," or "feebly 
 energetic." 
 
 133. There is nothing in the physical charaet< 
 either of the arenes, the psammites, or the clays, which 
 will enable us to prognosticate with entire certainty, 
 what their action on rich lime will be. 
 
 134. In this respect, the natural and artificial pouz- 
 zolanas offer some indications, but they are merely ne- 
 gative. Thus the hardness of grain, density, vitreous 
 or enamelled aspect, want of adhesion to the tongue, 
 in a word, cvcrvthing which indicates a great cohesion, 
 is an almost sure sign of mediocrity. \\ ith these 
 substances then, as with the different kinds of lime, 
 it is still experience which must guide the builder. 
 Nevertheless those who possess chemical knowledge, 
 may applv it usefully in this case ; for without making 
 a rigorouslv exact measurement of the qualities of the 
 above-mentioned substances, these agents assist us in 
 classing them in an approximate manner, by pointing 
 out, to a certain extent, the state of combination of 
 their principles ; it is this state which we shall endea- 
 vour briefly to investigate in what follows. 
 
 The Art i<m ofAcidi. 
 
 13.5. The pure sands, which are chiefly quartzose, 
 are not acted upon, either with heat or cold, by the 
 common acids (sulphuric, nitric, and muriatic), even 
 when most hijrhlv concentrated : this is not the case 
 when thev contain particles of very hard volcanic or 
 pseudo-volcanic mineral ; but even then the action of 
 acids 18 extremely slow, and very partial, (the calea- 
 
VII.] P01ZZ0LANAS. -55 
 
 reous sands, or those mixed with calcareous matter, 
 being excepted.) 
 
 136. The clay of arenes, when separated from the 
 sand by washing, dried, pulverized, and set to ma- 
 cerate for several days in muriatic acid, parts with a 
 portion of its iron, and moreover from one-tenth to 
 three-fifths of its alumina. 
 
 137. The schistose psammites are exactly in the 
 
 same position. 
 
 138. Muriatic acid dissolves a large portion of the 
 oxide of iron, b and nearly all the carbonate of lime in 
 common clays, when they contain them ; but it does 
 not act upon their alumina with anything like the 
 same energy, except in certain arenes and psammites. 
 The quantity dissolved rarely exceeds one-fifth, after 
 two or three days' digestion, and often does not amount 
 to one-tenth of the whole. 
 
 139. The action of acids upon the natural pouzzo- 
 lanas is extremely varied ; some of them are quite 
 refractory ; others yield up a good quantity of oxide 
 of iron, and more than half of their alumina, even 
 in dilute acids. There are kinds, which when treated 
 with sulphuric acid, become in a short time covered 
 with an aluminous efflorescence, and others exhibit 
 no change after a month, or even much more. (App. 
 XXXVI.) 
 
 1 10. The artificial pouzzolanas may exhibit exactly 
 the same phenomena. This observation sufficiently 
 
 b " As far as is known at present, iron combines with only two 
 proportions of oxygen, and forms two oxides, the protoxide and the 
 peroxide. The protoxide ha- a dark blue colour ; the peroxide is 
 rC rl." — Thomson's Chemistry, vol. i. p. 487. 
 
56 QUALITY OF MATERIALS, ETC. [CHAP. 
 
 proves, that the principles of the different substances 
 are in a varied state of combination ; that in some, 
 for example, the oxide of iron is merely mechanically 
 interposed, while in others it is more or less fixed 
 by the silica and alumina; that these earths them- 
 selves mav exist in a state of partial mixture ; and 
 lastly, that sometimes the whole of the elements are 
 closelv and intimately united, by a strong chemical 
 cohesion. 
 
 Action of Lime-water. 
 
 111. Lime, even in a boiling state, is destitute of 
 action upon the quartzose or calcareous sands. (App. 
 XXXYII.) Such is not the case with regard to the 
 arenes, the psammites, the clays, and the natural and 
 artificial pouzzolanas. These substances, if thrown in 
 the state of powder into limpid lime-water, decompose 
 it more or less ; and when in sufficient quantity, re- 
 duce it to a state of purity. 
 
 142. The following, then, are the conclusions which 
 result from a comparison of the actual qualities of the 
 ingredients of hvdraulic cements, and the behaviour 
 of these ingredients, with regard to acids and lime- 
 water. 
 
 1st. All the substances which we have termed 
 
 c This mav perhaps be due to the iron present in these sub- 
 stances ; for I found that peroxide of iron, prepared from green 
 vitriol, after being washed till it gave no trace of precipitate, on 
 adding the muriate or nitrate of baryta, entirely deprived lime-water 
 of its causticitv, on being shaken up, or boiled with it for a short 
 time. Bone-ash and phosphate of lime also have tin nine property ; 
 but silica, even in the gelatinous state, does not affect it — Tn. 
 
VII.] rOUZZOLANAS. 5J 
 
 " inert" (except the calcareous sands), are in general 
 entirely unaffected by acids, and have no action upon 
 lime-water. 
 
 2nd. Most of the substances which we have termed 
 " feebly energetic," are slightly acted on by acids, 
 and restore a very small quantity of lime (water) to 
 its pure state. 
 
 3rd. Most of those substances which we have called 
 " very energetic," are powerfully acted upon by acids, 
 and can restore a pretty large quantity of lime-water 
 to a state of purity. 
 
 143. In using the expression " most of the sub- 
 stances," we would have it sufficiently understood that 
 there are exceptions. Hence we see why we should 
 alwavs wait for proof by experiment, when we wish to 
 class a pouzzolana, an arene, or a clay, with perfect 
 certainty. 
 
CHAPTER VIII. 
 
 MANUFACTURE OF ARTIFICIAL POUZZOLANAS. 
 
 144. The object which we here aim at, is that 
 of replacing the volcanic, or pseudo-volcanic pouzzo- 
 lanas, by artificial products of at least equal quality, 
 at a slight expense. (App. XXXVIII.) 
 
 1 15. Amongst the rocks, or earths, essentially com- 
 posed of silica and alumina, those which have been 
 selected as lending themselves with the most facility 
 to the transformation which we have in view, are, 1st, 
 the clavs ; 2nd, the brown or yellow schistose psam- 
 mites, which form a clayey paste with water; 3rd, the 
 arenes rich in clay ; and 4th, some species of schists. 
 
 1 1 0. The agent employed is heat ; and the conditions 
 of the change are, 1st, that the material shall acquire 
 so much cohesion, as to be incapable of forming a paste 
 with water;* "2nd, that it should reach its minimum 
 specific gravity, and its maximum of the faculty of 
 absorption ; 3rd, that it become more subject than 
 before to the influence of chemical agents, such as the 
 weak acids. (App. XXXIX.) 
 
 I47« We fulfil these conditions by the aid of a verv 
 moderate roasting, so managed moreover, as to enable 
 
 1 " When the clay contains more than one-tenth of carbonate of 
 lime, it is apt to be deteriorated in quality by a high temperature, 
 and will form a much better pouzzolana when slightly calcined. 
 When it contains little or none, it is improved by an active heat." — 
 (,< nrr.il J'n "<sar(. 
 
MANUFACTURE OF ARTIFICIAL POUZZOLAN AS. 5Q 
 
 us to keep all the particles exposed to the air in a state 
 of incandescence. (App. XL.) 
 
 148. The first and best method, consists in pre- 
 viously pulverizing the clay, the psammite, or the 
 arene, which we have selected, and then strewing a 
 layer of it, about a centimetre (four-tenths of an inch 
 nearly) or more, on a plate of iron b heated to a point 
 between a cherry red and forging heat. We leave it 
 there till it be raised to the same degree, for a space 
 of time which varies, for each kind of material, from 
 five to twenty-five minutes. We take care to stir the 
 powder continually with a small rod, in order that the 
 
 b Having, in the course of some experiments on this subject, met 
 with a species of clay capable of transformation into a highly ener- 
 getic pouzzolana, I was led, in prosecuting a further investigation, 
 instituted with a view to discover the most economical process of 
 conversion, to try the effect of the powder of some broken pieces 
 of a vessel for containing' water, made of porous biscuit manufactured 
 from the same clay ; and I was much surprised to find it nearly 
 equally energetic with that which had been fresh calcined. The 
 broken fragments of biscuit had lain amongst a heap of rubbish in 
 a damp situation, exposed to heavy rains and the vicissitudes of the 
 weather for many months, after the vessel of which they had been 
 parts had fulfilled its office by holding water for perhaps a twelve- 
 month previous. Yet this powder, without a second calcination, 
 when mixed in stiff paste with half its weight of rich lime, set with 
 great firmness in six hours (the same as the calcined clay). We 
 may therefore conclude, that artificial pouzzolanas of this kind are 
 not materially injured by moisture, a fact which greatly enhances 
 their value ; and this observation is in correspondence with the ex- 
 perience of General Treussart, who says (p. 123), " As to arti- 
 ficial tarras, when once it has been prepared it requires no further 
 care ; for neither the action of the air nor humidity deprive it of any 
 of its properties ;" as well as with the results of other independent 
 experiments by myself. (Vide note to Art. 31 4.) — Tit. 
 
C)0 MANUFACTURE OF [CHAP. 
 
 whole of the particles may he uniformly calcined. 
 The clays or ochrey psammites, of a brown, or orange 
 red, or a full blood red, require a heat of a higher 
 degree, and sustained for a longer time, than the others. 
 Twenty minutes, and an incandescence nearer the 
 forging temperature than a cherry red heat, appear 
 to be the limits proper for them. The experiments 
 moreover are so easy, that we recommend every 
 builder to trust, in that respect, merely to his own 
 experience. The mode of calcination which I have 
 just pointed out, has not yet been applied on a large 
 scale ; it presents some difficulties. (App. XLI.) 
 
 149. The second method consists in rendering- the 
 material exceedingly porous, and permeable to the 
 air, if it be not so already, and then roasting it in the 
 manner of bricks, but in the highest part of a lime- 
 kiln, where the heat is insufficient, not merelv to 
 vitrify, but even to give a fusible brick the deoree 
 of burning necessary for commerce. 
 
 150. We make the material porous, by kneading it 
 with an equal quantity of quartzose sand, after which 
 it is divided into loaves or prisms, which are left 
 to dry and harden properly. This plan is particularly 
 suited to the compact and fusible clays ; but the pouz- 
 zolana which results from it has the defect of beino- 
 
 o 
 
 mixed with sand ; an inconvenience which might per- 
 haps be avoided, by substituting for the quartzose 
 sand any combustible substances in a finelv divided 
 state, such as sawdust, chopped-straw, wheat-chaff, 
 &c, &c. c (App. XLII.) 
 
 c Vide App. X. ami fa note. — Tk. 
 
VIII.] ARTIFICIAL POUZZOLANAS. 6l 
 
 151. When it is not our object to attain the highest 
 degree of perfection, we content ourselves with roast- 
 ing the material which we select in the state in which 
 nature provides it. Nevertheless it is proper to re- 
 duce it to a small bulk, less than the size of one's fist 
 for instance, if it be not so alreadv ; not forget tinp- 
 that a simple incandescence is sufficient, and that it is 
 by no means necessary to keep it up a very long time. 
 
 152. The limekilns, which answer at the same time 
 for burning bricks, draw a great deal of air, and in 
 that respect are perfectly adapted to the calcination 
 of the artificial pouzzolanas. We might also, with 
 equal success, apply the flame which rises above the 
 high smelting furnaces, where they reduce the iron- 
 ore. 
 
 153. All clay, principally composed of silica and 
 alumina, and moreover, fine, soft to the touch, and 
 which contains more or less of the oxide of iron, with 
 little or none of the carbonate of lime, will give a 
 "very energetic" pouzzolana, if it be treated by one 
 of the two first methods described above. d 
 
 d Two varieties tried by myself, and calcined according to the 
 first method (Art. 148), afforded excellent artificial pouzzolanas. 
 One of them, a stiff brown clay, which did not effervesce in nitric 
 acid, and which turned brick-red after calcination, set in three hours 
 with half its weight of rich lime. The other, a white kind of pipe- 
 clay, in which silica predominated, but containing no carbonate of 
 lime, and which changed to a light pink colour after burning, set 
 in six hours when made into a stiff paste with lime in the same 
 proportions. After five and a half months' immersion, no impression 
 whatever could be made upon the first of these cements, by the 
 action of an instrument exactly similar to Mr. Vicat's (described at 
 the end of the volume, and represented in plate II.) : upon the 
 
Ii l 2 MANUFACTURE OF [CHAP. 
 
 15k The BUM clay calcined in powder in a close 
 1, will also give a very energetic pouzzolana ; but 
 that pouzzolana will make the cements slower in set- 
 ting, and more susceptible of alteration by the imme- 
 diate contact of a flowing stream ; while it will also 
 augment the cohesion of its internal particles, and 
 their adherence to foreign bodies. (App. XLIII.) 
 
 155. The same clay calcined in fragments, according 
 to the third process," will furnish a pouzzolana simply 
 " energetic ;" but if the heat should be pushed so 
 high as to the full burning of brick, we should have 
 only a "feebly energetic " pouzzolana, or perhaps a 
 substance entirely " inert," if, owing to the presence 
 of any fluxes, it should have commenced vitrification/ 
 
 156. These observations apply only to the clavs, 
 the arenes, and the argillaceous psammites. The 
 schists succeed sometimes, but they generallv give onlv 
 mediocre results, more particularly the slatv species. 
 
 157- The matters improperly called cements bv 
 builders, are artificial pouzzolanas, obtained bv the 
 pulverization of old tiles and the rubbish of brick- 
 yards and potteries. Now, as they cast aside among 
 the refuse whatever is defective, either bv excess or 
 
 second. a v t tv >light indentation was made by the needle, measuring, 
 as nearly as could be ascertained, 0.0125 of an inch. — Tr. 
 
 ' Vide Art. 151. 
 
 f Five per cent of carbonate of lime will produce this effect But 
 the use of such a clay is not to be prohibited on this account as it 
 is easy to moderate the heat, and its presence is attended with some 
 advantage. General Treussart recommends a rather meagre clay 
 containing the above proportions of lime, in those cases wherein it is 
 impossible to provide machines to effect pulverization, as the\ an 
 inor.- easily reduced tn powder than the richer clays. — Tr. 
 
VIII.] ARTIFICIAL POUZZOLANAS. C)3 
 
 deficiency in burning- ; since moreover they employ, for 
 tiles especially, clays impoverished by sand, and more 
 frequently simply stiff earths, we perceive to how 
 many hazards the qualities of these kinds of pouzzo- 
 lanas are left. 
 
 158. The cinders of coal and turf sometimes form 
 an energetic pouzzolana, but they are sometimes also 
 altogether " inert." This depends upon the internal 
 constitution of these substances. 
 
 1.59- The slag from the forge, and the dross from the 
 large furnaces, ordinarily give but " feebly energetic" 
 pouzzolanas. 
 
 160. The remarkable cement known by the name 
 of the " aqua-fortis cement," is nothing more than a 
 combination of argil and potash, resulting from a 
 very feeble calcination of nitre and moistened clay. 
 It is a very energetic pouzzolana, but very dear. 8 
 (App. XLIV.) 
 
 ? Silex, alumina, and baryta, decompose this salt (the nitrate of 
 potash, or nitre,) in a high temperature, by uniting with its base. 
 (Ure's Dictionary.) The potash is rendered caustic, so that it may 
 perhaps act by favouring the partial vitrification of the elements 
 of the clay. Carbonate of soda or potash would, in such case, 
 produce the same effect. (Vide App. XLV.) — Tr. 
 
CHAPTER IX. 
 
 OF THE RECIPROCAL SUITABLENESS OF THE VARIOUS 
 KINDS OF LIME. AND THE INGREDIENTS WHICH 
 UNITE WITH IT, IN THE COMPOSITION OF MOR- 
 TARS AND CEMENTS. 
 
 161. Let us imagine that we have at our disposal 
 the four kinds of lime described in the first Chapter ; 
 and further, all the ingredients mentioned up to 
 Chapter VI. ; and, that being puzzled in our choice, 
 we are at a loss to know what course to take. The 
 following are the rules indicated by a very numerous 
 assemblage of facts, collected during observations of 
 fourteen years' continuance. (App. XLYI.) 
 
 First Case. 
 
 162. To obtain mortars or cements capable of ac- 
 quiring a great hardness in the water, or underground, 
 or in situations constantly damp, we must combine : 
 
 WITH THE 
 RICH 
 
 WITH TBI 
 
 6LIGRTLY 
 
 HYDRAULIC LIMES. 
 
 WITH THE 
 HYDRAULIC LIMES. 
 
 WITH THE 
 : NTLY 
 HYDRAULK 
 
 The " very ener-J The " simply encr- 
 p> .uziolanas, getic"pouziolanas,na- 
 natural or artificial, tural or artificial. 
 
 The " very energe- 
 tic" pouzzolanas, na 
 tural or artificial, tem 
 pered by the mixture 
 of a half of sand or 
 other " inert" sub- 
 stance. 
 
 The " energetic" 
 arenes and psam- 
 mites. 
 
 The " feebly ener-l " Inert" materials, 
 getic " pouziolanas, such as the quart- 
 natural or artificial. zose and calcareous 
 
 The " energetic" sands - a 
 Ipouzzolanas, natural Slag, dross, &c. 
 or artificial, tempered 
 by a mixture of about 
 one-half of sand. 
 
 The " feebly ener- 
 arenes and 
 psammites. 
 
 * With an eminently hydraulic lime, found in the neighbourhood 
 of Ma>ulipatam (vide not. to Art. 24), I found that the mixture of 
 
LIMES IN MORTARS AND CEMENTS. 
 
 65 
 
 Second Case. 
 
 163. To obtain mortars or cements capable of ac- 
 quiring great hardness in the open air, and of resist- 
 ing rain, heat, and severe frosts, we must combine : 
 
 WITH THE 
 RICH LIMES. 
 
 WITH THE 
 
 SLIGHTLY 
 
 HYDRAULIC LIMES. 
 
 WITH THE 
 HYDRAULIC T.IMF.S. 
 
 WITH THE 
 
 EMINENTLY 
 
 HYDRAULIC LIMES. 
 
 No ingredient 
 will effect this.b 
 
 No ingredient 
 will completely 
 effect this. 
 
 Any very pure 
 sands. 
 
 Quartzose pow- 
 ders. 
 
 The powders of 
 hard calcareous mi- 
 nerals, or other 
 " inert" matters. 
 
 Any very pure 
 sands. 
 
 Quartzose pow- 
 ders. 
 
 The powders of 
 hard calcareous mi- 
 nerals, or other 
 " inert" matters. 
 
 164. If, for any reasons, we should modify the rules 
 above given, we may still succeed in making tolerable, 
 and perhaps good mortar ; but to a certainty we shall 
 be farther off the best, and that in a greater degree, the 
 more completely the combinations made use of tend 
 to invert the scale, which places the " very energetic" 
 pouzzolanas opposite the very caustic rich limes, and 
 
 two parts of a highly energetic artificial pouzzolana produced a 
 much inferior cement to a like mixture of the same pouzzolana with 
 rich slaked lime. I did not find the time of set to differ much, but 
 the cement containing the hydraulic lime was meagre, and friable, 
 and soiled the finger on touching it, for a day or two after solidifica- 
 tion ; that prepared with rich lime, formed a compact, perfectly hard 
 mass, with clean surface, and conchoidal fracture, and so homoge- 
 neous in texture, and closely united, as to be superior to many sub- 
 stances which had undergone the action of heat, such as bricks, 
 tiles, See. — Tr. 
 
 b Having analyzed several very old mortars, with the view of dis- 
 covering, if possible, to what their superior durability might be attri- 
 buted, I found that the hardest and most compact almost invariably 
 
h(. LIMES IN' MORTARS AND CEMENTS. 
 
 the " inert" sands opposite the eminently hydraulic, 
 very mild limes. Lastly, we shall have done the great- 
 est mischief possible, when we have united together 
 rich limes and any kind of sands. Such is the language 
 dictated by a comparison of facts. It is unnecessary 
 to add, that when we meet with substances of quali- 
 ties intermediate between those which constitute the 
 categories given above, we must use medium propor- 
 tions ; but fresh experiments can alone tell, what will 
 be the peculiar result of this or that new combination 
 of principles, which it may suit the fancy of the builder 
 to adopt. 
 
 contained a considerable quantity of silica in a minute state of divi- 
 sion, and a portion in a gelatinous state, which I presumed to have 
 been in chemical combination with the lime. In some excellent 
 specimens of very old mortar also, magnesia was found to exist 
 in considerable proportion. The limestones, therefore, from which 
 these mortars were prepared, must have contained the silica and 
 magnesia as constituent principles ; and it is to be recollected, that 
 it is the presence of these substances which communicates the pro- 
 perty of hardening under water. Hence we may infer, that the 
 most durable common mortars are such as have been manufactured 
 from hvdraulic limes. — Tr. 
 
SECTION III. 
 
 MIXTURES OF THE DIFFERENT LIMES WITH SAND, 
 AND THE OTHER INGREDIENTS OF MORTARS 
 AND CEMENTS. 
 
 CHAPTER X. 
 
 OF CALCAREOUS MORTARS OR CEMENTS INTENDED 
 FOR IMMERSION. 
 
 165. Every calcareous mortar or cement destined 
 for immersion, and mixed beforehand as a matrix, 
 with a certain quantity of stones, fragments, or rub- 
 bish, constitutes what is called a beton. It is a real 
 piece of masonry of small materials, which is depo- 
 sited at once in the situation which it is to occupy. 
 In what follows, we have merely to consider the matrix 
 of the bctons. 
 
 Choice of Proportions. 
 
 166. The proportions which lead to the greatest in- 
 duration, are as varied as the number of possible 
 combinations of the various known ingredients ; that 
 is to say, in a word, the question cannot be well 
 discussed in any but an imperfect and altogether ap- 
 
 f '2 
 
68 MORTARS OR CEMENTS [cHAP. 
 
 proximativo manner, and that in this respect, every 
 builder ought to study the materials at his disposal.' 
 
 lf>7. Of the known materials, the arenes, the 
 psammites, and the clays, appear to have the least 
 affinity for lime ; when reduced to a dry powder, 
 and measured in that state, they take, for a volume 
 represented by unity, as follows : — Of rich lime slaked 
 by the ordinary process in stiff paste, from 0.15 to 
 0.30; of slightly hydraulic lime, from 0.2 to 0.2 5; 
 and of hydraulic lime from 0.25 to O.oO. 
 
 168. The energetic, and very energetic pouzzolanas, 
 require, in the same circumstances, of rich lime, from 
 0.30 to 0.50 ; of slightly hydraulic lime, from 0. M > 
 to 0.60. 
 
 It if). The quartzose or calcareous sands — of hydrau- 
 lic, or eminently hydraulic lime, from 0.50 to 0.66. 
 
 170. In general terms, it is better to err from a de- 
 ficiency, than an excess of lime, when making mix- 
 tures of rich lime, and any kind of pouzzolanas ; and 
 trice versa in the case of hydraulic or eminently hy- 
 draulic limes, mixed with quartzose or calcareous 
 sands/ 1 (App. XLVIII.) 
 
 171. The proportions play a more important part, 
 the weaker are the ingredients which are mixed 
 
 " The reader will find in the notes (App. XLYII.) an extract 
 from Mr. Smeaton's excellent essay on water-cements, containing the 
 proportions of twenty different compositions employed by him, in the 
 construction of the Eddystone Lighthouse and other works, and 
 which, being prepared from materials in common use in England, 
 can not fail to be valuable. — Tr. 
 
 b " A considerable excess of lime is proper in common mortars ; 
 an excess of cement cannot be injurious to hydraulic mortars, except 
 when employed in plastering." — Raucourt de ChnrhviUe. p. 14-. 
 
X.] INTENDED FOR IMMERSION. (J9 
 
 together; that is to say, that slight differences in 
 these proportions may, in that case, correspond to 
 very considerable differences in the hardness of the 
 compounds. 
 
 172. Furthermore, all that we have just said may 
 be modified according to the purpose to which we pro- 
 pose to apply the mortars or cements ; more especially 
 in dealing with pouzzolanas and the rich limes. Are 
 these cements intended to bind materials together ? 
 Let there be given a slight excess of lime, without 
 which they will not adhere to stone without much 
 difficulty. Are they to be employed alone merely ? 
 Let us keep as close as we can to the exact propor- 
 tions, in order that their hardness may be the greatest 
 possible. 
 
 Choice of the Process of Extinction. 
 
 173. The nature of the lime, and of the ingre- 
 
 c Colonel Raucourt de Charleville considers the best hydraulic 
 lime to be composed of equal parts of pure caustic lime, and of such 
 other ingredient, as by its chemical action gives birth to hydraulic 
 properties; such as silica, alumina, magnesia, &c, and which he 
 terms "base hydraulique." None however is to be considered 
 such, unless in a sufficiently minute state of division to exert its full 
 influence, and allowance is to be made for all such gritty and inert 
 particles as the best hydraulic lime is apt to contain, their amount 
 being ascertained by experiment, and a proportionally smaller 
 quantity of sand being used in forming the mortar. The best hy- 
 draulic mortar he considers to be that prepared from a mixture of 
 clean sand with so much of the above matrix as is at least sufficient 
 to intercede its grains. Many hydraulic cements, particularly those 
 made by mixtures after calcination, contain so much inert matter as 
 to be incapable of the addition of sand. — Tr. 
 
70 MORTARS OR CEMENTS [CBAP. 
 
 dients employed, regulates the choice of the process 
 of slaking. 
 
 174. Facts lead to the following general observa- 
 tion, viz. : — 
 
 1st. That for all possible kinds of cement, of rich, 
 or slightly hydraulic limes, the order of superiority of 
 the three common kinds of extinction is as follows : 
 spontaneous, — by immersion, — and ordinary. 
 
 2nd. That for every possible kind of cement or 
 mortar, of hydraulic and eminently hydraulic lime, or- 
 dinary extinction, — by immersion, — and spontaneous.' 1 
 
 17-5. There may be exceptions doubtless, but we 
 have to this day met with none. 
 
 I7C. The differences of induration, which follow 
 the use of this or that process, are very variable ; they 
 reach their maximum in the case of the rich limes, 
 when mixed with inert substances, and become almost 
 insensible, when these same limes are allied to the 
 very energetic pouzzolanas. Between these limits, 
 the differences observe a progressive scale, which is 
 regulated by the variable energy of the ingredients. 
 (App. XLIX.) 
 
 177- ^ e may slake the hydraulic, or eminently 
 hydraulic limes, either by immersion, or by the 
 ordinary process, without entailing any great dif- 
 ference in the mortars or cements in which these 
 limes are employed ; but this is not the case with 
 regard to the spontaneous extinction, the influence of 
 
 d Mr. Smealon mentions, that the Aberfhaw blue lias, when 
 
 quenched hot from the kiln, falls to powder as freely as any other 
 kind of lime, and that when mixed as fresh burnt as possible, i" 
 thought t<> -. t more strongly in tmder^water vwks. — Tn. 
 
X.] INTENDED FOR IMMERSION. J I 
 
 which is accompanied with a more injurious conse- 
 quence, the more eminently hydraulic the lime to 
 which it is applied. (App. L.) 
 
 Of the Manipulation or Manufacture. 
 
 178. The manufacture includes the slaking of the 
 lime, and its mixture with the ingredients which unite 
 with it in the composition of the mortar or cement. 
 
 179. In whatsoever way it may have been slaked, 
 the lime ought to be first brought to the condition 
 of a thoroughly homogeneous paste, and then to be 
 mixed with the ingredients destined for it. f 
 
 180. This paste ought to be as stiff as possible, 
 whenever it is intended to act the part of a matrix 
 amongst hard and palpable grains, which preserve 
 
 e Mr. Vicat has omitted to mention what seems to me to be an 
 important caution regarding the choice of the process of extinc- 
 tion, viz., that the extinction by immersion will be attended with 
 similar evil consequences, if the lime be exposed to the influ- 
 ence of a humid atmosphere for any length of time ; and this is 
 equally the case with the ordinary process, if the mortar be per- 
 mitted to remain mixed sufficiently long to allow the injurious action 
 of water upon the lime to take effect. Hydraulic lime should be re- 
 duced to the utmost state of division, and used as quickly a possible 
 afterwards. (Vide note to Art. 185, and App. L.) — Tr. 
 
 f In hydraulic mortar composed of lime and tarras, repeated 
 beatings rather improved those compositions in which lime pre- 
 dominated, more particularly when it was rich lime. " The cus- 
 tomary allowance for tarras mortar beating, first and last, is a day's 
 work of a man for every bushel of tarras ; that is, for two bushels 
 of lime powder with one bushel of tarras." — Smeaton, Construction 
 of Eddyslone Lighthouse. 
 
7 l 2 MORTARS OR CEMENTS [CHAP* 
 
 a sensible interval between one anotber. Such is 
 the case with mortars, or mixtures of lime and sand. 
 (App. LI.) 
 
 181. It may have a more or less thin consistency, 
 when, with a pulverulent substance, whose grains are 
 impalpable, and at the same time absorbent, we would 
 form a whole of a homogeneous appearance, in which 
 the eye is unable to discern any one of the consti- 
 tuent elements. This is the case with the calcareous 
 cements, or the mixtures of lime with the pouzzolanas, 
 arenes, clays, or psammitcs. (App. LI I.) 
 
 182. But in every possible case, the resulting mix- 
 ture, be it mortar, or cement, must exhibit a good 
 chn/e// consistency, according to the definitions laid 
 down in that respect in Chapter V. g 
 
 183. We may at pleasure bring lime which has 
 been slaked by immersion, or spontaneously, to the 
 condition of stiff paste or pulp, when we take it in the 
 pulverulent state ; but this is no longer possible when 
 we have to deal with lime slaked by the ordinary pro- 
 cess, if it has been drowned at first in too much water. 
 To avoid committing this mistake, we ought to em- 
 ploy, at the moment of slaking by that process, no more 
 than the water rigorously required, that is to sav, 
 which is necessary to cause the lime to pass from the 
 solid caustic state to that of a stiff paste. In fact there 
 is always an opportunity to add it, if necessary, at the 
 time of applying it to use. 
 
 184. The hydraulic, and eminently hydraulic limes, 
 
 R Vide App. LXII. and its note. — Ta. 
 
X.] INTENDED FOR IMMERSION. J3 
 
 present certain difficulties in this respect. We shall 
 here detail the process to be followed, when the ordi- 
 nary mode of slaking is applied to them. 
 
 185. The quick-lime in lumps is shovelled into an 
 impermeable basin, where it is spread out in beds of 
 equable depth from 20 to Q5 centimetres (7.8 to 
 9.8 inches, Tr.) ; the water is poured in gradually, 
 and in such a manner that it may spread, and easily 
 penetrate the spaces which the fragments of lime leave 
 between one another. The effervescence is not long 
 in displaying itself: we continue to throw in lime 
 and water alternately ; but we must take especial 
 care not to mash the materials, and bring them to 
 a pulpy consistency, according to the bricklayers' 
 custom. But when by accident any of the shovel- 
 fulls of lime slake to dryness, we turn the water to it 
 by means of little channels, which we draAv lightly 
 through the pasty mass, and from time to time thrust 
 a pointed stick into those parts where we suspect the 
 w r ater has been wanting : if the stick comes out of it 
 covered with an adhesive coating of lime, then the 
 extinction has been proper ; if, on the contrary, there 
 escape a floury smoke, it is a proof that the lime has 
 slaked to dryness : we then enlarge the hole, make 
 others beside it, and direct the water upon it. h 
 
 h With eminently hydraulic limes, it may be found highly advan- 
 tageous after slaking, and the separation of the stony and unburnt 
 parts, to bruise and reduce to powder those minute lumps, of which 
 they are often full, as in some instances this operation may have 
 the effect of developing unexpected hydraulic properties. 
 
 Colonel Kaucourt de Charleville in this manner discovered the 
 virtues of the Narva lime, the best of the Russian cements, which 
 
7 1 MOllTAKS OR CEMENTS [cil.U. 
 
 L86. We ou^ht not in this way to slake more lime 
 than is required for the completion of one or two 
 days' work at most. Two separate basins, or two 
 compartments in the same basin, are indispensable. 
 We begin to fill the one, when the other is nearly 
 emptied. By this means the lime has at least twenty- 
 four hours to sour, and the doggish lumps become all 
 reduced. 
 
 187. The lime which has been slaked as I have 
 just described, is already very stiff next day ; it is 
 necessary either to pick it, or at least to cut it with a 
 spade, in order to remove it. It seems in a state that 
 it can no longer be brought to a pasty condition with- 
 out a further supply of water, but that is a mistake; 
 it is easily rendered ductile by means of the pestle. 
 The beater (" rabot") has no longer power to bind it : 
 but if it is battered perpendicularly with rammers of 
 cast-iron, fixed to handles of wood, it is not lomj in 
 disgorging a part of the water, which, if we mav so 
 say, it had rendered latent ; it then forms a paste 
 sufficiently thin to receive the sand. (App. LIU.) 
 
 188. The materials which combine in the formation 
 of calcareous cements, arc worked up and mixed to- 
 gether with the more facility, the greater the quantity 
 of water with which they have been diluted ; this is to 
 such an extent, that the same workmen will take four 
 times as much time to prepare a stiff mortar, as would 
 be required to prepare the same quantity of that degree 
 of softness adopted by masons. If, then, it signified 
 but little, in regard to the promptitude with which 
 
 had been entirely unknown till he thought of trying tlii- experi- 
 ment — Tk. 
 
X.] INTENDED FOR IMMERSION. 7$ 
 
 the mortar set, and its ultimate hardness, whether it 
 were worked stiff or soft, it would on the other hand 
 be of importance, in an economical view, to know the 
 limit of the greatest quantity of water proper to be 
 used, in order to keep as near the mark as possible. 
 
 189. However, the most exact and varied experi- 
 ments show, that every mortar or cement destined for 
 immediate immersion, ought, as we have before said, 
 to be worked to a stiff clayey consistency, or lose 
 one-half to two-thirds, and sometimes four-fifths, of 
 the strength it would have acquired if properly 
 treated. 1 
 
 190. But it is not with the ordinary instruments 
 that we can hope to attain the object alluded to. It 
 is absolutely necessary to substitute the rammers we 
 have spoken of above for the beaters, and batter the 
 mass vertically with force and suddenness. It is not 
 until the mortar or cement has been fully worked, 
 that we introduce the rubble or flints which constitute 
 the beton : this second operation also is effected by 
 the aid of the rammer. 
 
 Of the Using or Immersion. 
 
 191. All the trouble taken in the fabrication is 
 
 ' By leaving a mortar, which has been mixed to too thin a con- 
 sistency, exposed to the air, and stirring it from time to time, to 
 change the surfaces of contact, till it has become sufficiently firm, it 
 may regain half of the virtues of which the drowning has deprived it. 
 (Raucourt, p. 99). When, however, hydraulic mortars which had 
 become dry, were beaten up again and water added to them, they 
 were found to be deprived of hydraulic properties ; and this was 
 more remarkable in the eminently hydraulic limes (p. 108). Pouz- 
 zolanas are not injured in this manner, until after admixture with 
 the lime. (Vide note to Art. 311.) — Tn. 
 
7') MORTARS OK CEMENTS [CHAP. 
 
 pretty nearly dead loss, if the immersion of the beton 
 be ill done ; in no ease ought it to be shovelled in. If 
 the depth of the water be inconsiderable, as, for ex- 
 ample, a metre, (39.37 inches, Tn.) we should lower 
 it to the bottom, and there deposit it gently. The 
 hopper ought to be generally interdicted. The mass 
 of water which it contains, although stagnant, always 
 soaks the beton which passes through it. 
 
 192. The bux proposed by Belidor is without doubt 
 the best. We have simplified it, by giving it the 
 form of a truneated quadrangular pyramid, inverted. 
 It is suspended a little above its centre of gravity ; 
 on reaching the bottom of the water, it empties itself 
 like a tumbrel, turning over by a tumbler movement. 
 The beton leaves it in pyramidal shape, and settles 
 firmly upon its largest base. 
 
 193. The immersion of beton is carried on by suc- 
 cessive layers, whose depth should not exceed O m . 40°. 
 (15."/ 5 inches, Tr.) As fast as the layer advances 
 within the coffer-dam, or trench, it drives before it a 
 pulp, or milky fluid, which is continually increasing, 
 and becomes the more abundant the greater the 
 breadth and height of the layers arc. This pulp, by 
 reason of its fluidity, makes way for the product of 
 each partial immersion, and finally, if we do not take 
 care, rises from one layer to the next, and in such a 
 manner as to leave behind it a thickness of from 3 to 5 
 centimetres (1.18 to 1.9 inches, Tr.) between the two 
 successive beds : a very serious evil ; for being com- 
 posed, as it is, of lime which has been drowned, this 
 pulp never sets more than imperfectly, and thus ruins 
 the continuity of the mass, of which it moreover 
 favours the settlement. 
 
X.] INTENDED FOR IMMERSION. 77 
 
 194. It is oasv to obviate this inconvenience in a 
 flowing stream ; it is sufficient to contrive little open- 
 ings in the sides of the coffer-dam, and to multiply 
 them to such an extent, that the water of the enclosure 
 may be renewed without ceasing. We must, however, 
 keep them so narrow, as that the beton be not carried 
 through. k 
 
 195. In stagnant water, we may establish one or 
 two powerful pumps at the extremity of the enclosure, 
 where each layer in it ends, and pump out the pulpy 
 fluid as fast as it arrives. Brooms are employed with 
 success, when the coffer-dam affords an outlet ; but 
 this method supposes that we can give each layer time 
 to set. 
 
 190. Furthermore, we reduce the formation of this 
 milky fluid to a mere trifle, when we take great care 
 in the immersion. We ought above all to avoid beat- 
 ing the beton when immersed. It is a perfectly use- 
 less operation, and is moreover very injurious. The 
 beton of itself settles as much as we could desire ; 
 the beating has no other effect than that of diluting 
 and impoverishing it. The only thing which we may 
 allow ourselves to do, is to spread or w r eigh down the 
 product of each partial immersion by compression, 
 but without giving it any blow. 1 (App. LIV.) 
 
 k Mr. Smeaton used a coating of Plaster of Paris to guard the 
 cement of the Eddystone Lighthouse, when there was not time for 
 it to set before being subjected to the violence of the sea. — Tr. 
 
 1 The following ingenious method of immersion, proposed by Gene- 
 ral Treussart, is well deserving of attention, although he does not 
 speak of it as having been subjected to trial. The space on which the 
 foundation is to rest, is first surrounded by sheeting piles, and cleared 
 
78 MORTARS OR CEMENTS [CHAP. 
 
 1<)7. A practice very generally admitted in former 
 times, and which naturally sprung from the persua- 
 sion, that the most rapid set led to the greatest abso- 
 lute induration, consisted in making use of hot lime, 
 and in immersing the beton while still warm. Now a 
 bcton still warm is necessarily one imperfectly re- 
 duced ; it is in fact quite impossible, that the heat 
 developed by the quick-lime should be retained during 
 the whole period of time required by a good manipu- 
 lation. Every manifestation of heat at that period 
 
 out to the depth of about six feet, which space is filled up to the h \ < 1 
 of the bed of the river with beton. While thi- i> -till somewhat 
 soft, a second row of sheeting piles parallel to the first, and at the 
 distance of four or five feet, is driven into the beton itself, to the 
 depth of eight inches. The two rows are to be firmly bound and 
 united together by struts, braces, and other means, and the space be- 
 tween them filled in with a puddling of clay. Thus a coffer-dam 
 resting on the beton is formed, so that when it has become induratt d. 
 the whole of the water may be pumped out, and the masonry of the 
 piers built up within it. But as the removal of the water from the 
 interior may expose the whole to the danger of being lifted up by 
 the pressure of the fluid, since it then becomes similar to an empty 
 caiaaon, it may be necessary to guard against this danger, by load- 
 ing it with weights placed upon trestles supported by the beton, 
 which will keep the whole down till the masonry has been exi cuted. 
 When this has been done, the interior line of piles may be easily 
 removed. The outer row will require more trouble if they have 
 I., i ii driven to the depth of six feet or more; and there is also a 
 risk of the lu ton insinuating itself between them, and opposing a 
 further n -i-tance to their extrication ; to guard against which, a 
 stout piece of sheet-iron might be bent round the inside of them 
 before filling in the foundation with the beton. which would 
 prevent its entering the joints. Or the outer row of piles may 
 be sawed off level with the beton, and ^o hit, which seems 
 better. — Ta. 
 
X.] INTENDED FOR IMMERSION. 7Q 
 
 indicates the successive developement of a sluggish 
 lime, and consequently an imperfect extinction and 
 mixture." 1 Now if such a mixture be immersed in a 
 spot where nothing confines it, it swells, becomes di- 
 luted, and spreads. Hence we must conclude, that 
 it is not proper to use the lime, until after it has com- 
 pletely cooled, which is a certain sign of its being 
 completely slaked. Moreover, it will rest with the 
 intelligence of the builder, to distinguish when the 
 heat given out by a large quantity of slaked lime in 
 paste, is the result of a real internal action, or the 
 remains of the first effervescence. (App. LV.) 
 
 19S. We ought not, as Belidor directs, to wait to 
 immerge the beton, till it has been deprived of its duc- 
 tility by an incipient desiccation ; for it parts asunder 
 and crumbles in an incredible manner, and will then 
 merely form a pulp, which necessarily sets very slowly 
 and imperfectly : such a beton does not finally attain 
 more than from one-tenth to three-tenths of the hard- 
 ness of which it is susceptible, when properly immerged. 
 
 199. When, from unexpected hinderances in works, 
 we are obliged to postpone the immersion of a cer- 
 tain quantity of beton already prepared, and it has 
 begun to harden in consequence, there is not the 
 least danger in beating it up afresh, and bringing 
 it to its first consistency by the addition of water ; 
 provided nevertheless, that the hardness it has ac- 
 
 m These remarks cannot be applied to the employment of those 
 hydraulic mixtures, which are used unslaked, and ground previous 
 to mixture, such as our Roman cements, concrete, &c, &c\ the 
 theory of the consolidation in these cases, being quite distinct from 
 that of the lurdening of common mortars and betons. — Tr. 
 
SO MOETAB8 OE CEMENTS [CHAP. 
 
 quired merely arise from a too rapid desiccation, 
 brought on in a few hours by the heat of the sun, or a 
 scorching wind. 
 
 £1 N ). When it is possible to make use of mortars 
 and cements in the dry way, in a drained enclosure, 
 the beton is generally supplanted by masonry. \Ve 
 may then double the future resistance of which these 
 mortars or cements are capable, by leaving them to 
 acquire, previous to admitting water into the enclo- 
 sure, a certain degree of hardness, not incompatible 
 with an obvious humidity ; such, in a word, that the 
 white tint, which is characteristic of dryness, shall 
 never make its appearance. 
 
 Action of the Water upon the parts of the Mortars 
 and Cements in immediate contact vitJi it. 
 
 '201. The parts of mortars and cements in imme- 
 diate contact with the water, after having acquired a 
 certain degree of hardness, at periods varying with 
 everv description of lime and ingredients, sometimes 
 finally retrograde so far, as even to lose the consistency 
 they had at the moment of immersion. They also 
 form themselves a kind of envelope, whose thickness 
 is constantly increasing, and tends to reach the centre. 
 If we remove it by an iron knife by scraping the sur- 
 face down to the sound part, it forms a second, and so 
 on, one after another. 
 
 l J( £. These phenomena, which are very remarkable 
 when we make use of the rich limes and feebly ener- 
 getic pouzzolanas, are imperceptible in every case, 
 where we use the very energetic pouzzolanas, or the 
 
X.] INTENDED FOR IMMERSION. 81 
 
 hydraulic and powerfully hydraulic limes combined 
 with the ingredients proper for them. We see of 
 how much importance this observation is to the dura- 
 bility of works exposed to the dashing and erosion 
 of a current or agitated water ; but in a tranquil 
 pool the progress of this species of decomposition 
 has a limit. A very thin blackish or whitish crust 
 insensibly forms on the soft envelope of which we 
 have spoken ; behind this sort of shield, the forma- 
 tion of which is due to carbonic acid with which 
 every water is more or less impregnated, the soft 
 parts regain their consistency by little and little, 
 and everything seems to indicate that at some period 
 its solidification will be complete. It is certain that 
 after six years it is still not equal to the centre in 
 hardness." 
 
 203. On being submitted to examination, the de- 
 teriorated parts exhibit much less lime than the others ; 
 what is deficient then, has been dissolved and carried 
 off; it was in excess in the compound. 
 
 201. Nature, we see, labours to arrive at exact pro- 
 portions, and to attain them, corrects the errors of the 
 hand which has adjusted the doses. Thus the effects 
 which we have just described, and in the cases alluded 
 to, become the more marked, the further we deviate 
 from these exact proportions. (App. LVI.) 
 
 n Mr. Smeaton made some experiments to ascertain whether any 
 difference would arise in the strength of hydraulic mortar when 
 mixed with fresh or sea-water, the compositions being immersed in 
 the same water ; and he found, that after a trial of two or three 
 months, those made up with the salt-water appeared, if there were 
 any difference, to have the preference Tu. 
 
 G 
 
82 MORTARS OR CEMENTS [CHAP. 
 
 Influence of Time. 
 
 205. Some persons are in the habit of concluding 
 upon the future goodness of a cement by the rapidity 
 of its " set. ;" numerous facts prove that this indication 
 is not always constant. The second process of extinc- 
 tion, for instance, hastens the set of all bctons of power- 
 fully hydraulic lime, but does not lead to as great a 
 degree of hardness as the ordinary process. Besides, 
 there are ingredients whose binding qualities are only 
 developed in a slowly progressive manner, and which 
 nevertheless attain a very high degree of solidification. 
 The time of first setting cannot be taken as an exact 
 prognostic of the future hardness, except when we 
 compare together cements or mortars of the same 
 kind ;° thus, for example, when a mixture of 200 parts 
 of pouzzolana and 100 of rich lime takes six days to 
 set, while a mixture of the same consistency of 200 
 parts of the same pouzzolana with 270 parts of the 
 same lime take nineteen days, it is certain that the 
 first will become more hard than the second. And 
 this will also be true, if, while the proportions con- 
 tinue invariable, the cements differ merely by the quan- 
 tity of water introduced into them, and if, by reason of 
 this difference, the more stiff one sets sooner than the 
 other. 
 
 206. The following remarks are deduced from the 
 
 " I have remarked also, that mortars of hydraulic limes which 
 set very quickly did not exhibit great resistance; but those formed 
 of pouzzolanas, which caused common (rich) lime to set speedily, 
 always gave good mortars." — General Treussart, p. 1 2.3. 
 
X.J INTENDED FOR IMMERSION. 83 
 
 facts which have been observed up to the present 
 day : — 
 
 1st. An excess of rich, or slightly hydraulic lime 
 in a cement, retards its set ; the proportions most 
 favourable to that set are also those which give the 
 greatest hardness. 
 
 2nd. The second and third modes of extinction 
 seem generally more adapted to hasten the set than 
 the first. 
 
 3rd. The progress of the cements of rich limes and 
 the energetic or very energetic pouzzolanas, continues 
 still sensible during the third year following their im- 
 mersion. 
 
 4th. The progress of the mortars formed of the hy- 
 draulic or eminently hydraulic limes and the quartzose 
 and calcareous sands, is no longer appreciable after 
 the second year of immersion. 
 
 5th. Time modifies, but does not invert the rela- 
 tions in respect to hardness which are deduced from 
 a comparison of the three processes of slaking. That 
 is to say, the order of pre-eminence observed at the 
 end of the first year, is still the same at the end of 
 the third, and so on afterwards. (App. LVII.) 
 
CHAPTER XL 
 
 OF MORTARS CONSTANTLY EXPOSED TO THE AIR 
 AND WEATHER. 
 
 207. We have already said in Chapter IX., that 
 the only mortars capable of standing the vicissitudes 
 of the atmosphere, and of acquiring at the same time 
 a great hardness, were those composed exclusively of 
 the pure quartzose, granitic, or calcareous sands, and 
 of the hydraulic, or powerfully hydraulic limes. If 
 then in what follows we treat of ordinary mortars, or 
 the mixtures of sand and rich limes, it is because we 
 are compelled to do so to complete the history of the 
 phenomena which we have to describe. For it is our 
 most decided opinion, that their use ought for ever to 
 be prohibited, at least in works of any importance. 11 
 
 a In those situations in which it « impossible to avoid the use of 
 rich limes, it may be useful to be aware that their bad qualities may 
 be in some degree corrected, by the use of a comparatively small 
 quantity of the coarsest sugar dissolved in the water with which 
 they are worked up. This substance (or "jaghery") is extensively 
 employed in the East, and with admirable effect ; for the common 
 mortars made of calcined shells, when avcII prepared at first, resist 
 the action of the weather for centuries ; and I have no doubt that 
 this is in great part to be attributed to the use of sugar, the influence 
 of which on the first solidification of the mortar is very marked. 
 Even in this country it may occasionally be found advantageous 
 to employ the cheapest sugar, or molasses, when works of import- 
 ance have to be stuccoed with rich lime; for its aid is chiefly con- 
 fined to the hardening of the outer surface, which is effected by 
 
MORTARS EXFOSED TO THE AIR, ETC. 85 
 
 208. Among the results which flow from a general 
 comparison of the mortars with the hydrates, or solids 
 formed by the combination of water alone with the va- 
 rious known kinds of lime, the most remarkable and 
 most important may be exhibited as follows : — 
 
 1st. That the hydrates of lime which in the open 
 air attain the Greatest hardness, are those whose mix- 
 tures with pure sands, on the contrary, produce the 
 weakest mortars. 
 
 2nd. The intervention of pure sand does not tend, 
 as was before believed, to augment the cohesion of 
 which every kind of lime indifferently is susceptible ; 
 but it is injurious to rich limes, very serviceable to the 
 hydraulic and eminently hydraulic limes, and is neither 
 beneficial nor injurious to the intermediate kinds. 
 
 209. Sands being, as we have already said in Chap- 
 ter VII., merely inert substances, it would seem that 
 they ought not to differ in quality from one another, 
 
 employing a stronger solution when laying on the stucco, and rub- 
 bing it with wooden floats afterwards, which is sometimes continued 
 several hours ; and as the quantity of fluid required for these pur- 
 poses is not great, the expense of the sugar, if purchased wholesale, 
 would not be a very serious addition to the cost of the work. The 
 proportions used in India are various, depending upon the judgment 
 of the workmen. I am unable to state precisely what quantities the 
 solutions usually contain, but as well as I recollect, there need not be 
 more than about a pound weight to every eight or ten gallons of Mater 
 in mixing the stucco, and the same quantity to two or three gallons 
 for laying on and floating afterwards. After the sugar has been dis- 
 solved, and the solution prepared for use, a quantity of fresh quick- 
 lime is added, and well stirred with it, so that as much may be taken 
 up as possible ; by this means a very strong lime-water is prepared 
 (note, Art. 11), which is made use of in the manner above men- 
 tioned. — Tr. 
 
8(j MORTAKS EXPOSED TO THE AIR [CHAP. 
 
 in anv wav except by the form, the size, and the hard- 
 ness of their grains. The ancient builders wished us 
 to choose the fossil sands, harsh to the touch, in pre- 
 ference to the rounded and polished sands : they re- 
 garded the colour also, rejected the yellow, &c, &c. 
 But the whole of their writings on that subject are so 
 vague, the experiments on which they depended are 
 so incomplete, and conducted with so little method, 
 that we can conclude absolutely nothing from them. 
 One thing which we know to be quite certain, and 
 which we ought never to lose sight of, is this — that 
 there is no sand whatever, be it red or vellow, erey 
 or white, with round grains or angular ones, &c, 
 which can, if it be inert, form a good mortar with 
 rich lime. Whilst, on the other hand, all possible 
 kinds of sand, provided they be pure, that their grains 
 be hard, and do not exceed a certain size, give excel- 
 lent mortars with the hydraulic and eminently hy- 
 draulic limes. Nevertheless, we admit that there are 
 differences in the quality of sands, according as their 
 constituent elements may be granitic, calcareous, schis- 
 tose, or volcanic, &c. ; but these differences being in 
 general very small, we shall in what follows merely 
 attend to those which depend upon the size of the 
 grains. (App. LVIII.) 
 
 Influence of the Size of the Sand. 
 
 210. We shall call coarse sand, that, whose grains, 
 supposing them round, vary from one and a half to 
 three millimetres (.0.59 to .118 inch) in diameter; 
 fine sand, that of which the dimensions in the same 
 
XI.] AND WEATHER. 87 
 
 way are comprised between one and one and a half 
 millimetres (.039 and .059 inch) ; and powders, the 
 solid substances of the same nature, whose largest 
 particles never reach the fifth of a millimetre (.00787 
 inch). These definitions being understood, experi- 
 ments prove, that the quartzose and calcareous sands 
 take, with respect to each species of lime, the follow- 
 ing order of superiority, viz. : — 
 
 211. For the eminently hydraulic, and simply hy- 
 draulic, 1st, fine sand; 2nd, irregular-grained sand, 
 resulting from the mixture of coarse and fine ; b 3rd, 
 coarse sand. 
 
 *> The object of mixing sands is, to obtain the greatest possible 
 quantity of matter within a given bulk ; and this is attained by filling 
 up the interstices between the parts of a coarse rubble by the finer 
 particles of sand, and then the interstices of both these by the ce- 
 menting matter. A method of estimating the proportion of these 
 interstices or voids in a mass of sand is given in note to Art. 102; 
 and by the plan therein detailed, the amount of condensation ob- 
 tained by mixing them, is at once shown by the increase of weight 
 which it produces. When, however, the means for making such a 
 trial are not at hand, another excellent process, described by Colonel 
 Raucourt de Charleville, may be resorted to. To estimate the voids 
 in any mass of stones, gravel, or sand, a measure is taken and exactly 
 filled with it, and a similar one filled with water ; part of the water 
 is gradually transferred from the second to the first measure (pour- 
 ing it over the stones or sand), till it is full. It is then easy to judge 
 by the quantity of water used, what proportion the voids bear 
 to the whole bulk of the sand, and which will evidently be the same 
 as the ratio of the quantity of water taken from the second measure 
 (to fill them up) to its whole capacity. Colonel Raucourt de Charle- 
 ville found, that rubble, consisting of pebbles of about half an inch dia- 
 meter, required half a measure to fill up their voids ; gravel, of grains 
 from oue to two lines, five-twelfths of do. ; common sand, of grains 
 half a line diameter, two-fifths do. ; fine sand, one-tenth of a line dia- 
 
88 MORTARfi EXPOSED TO THE A1K [CHAP. 
 
 212. For the slightly hydraulic limes, 1st, irregular- 
 grained sand, mixed as above ; 2nd, line sand ; 3rd, 
 coarse sand. — For rich limes, 1st, coarse sand ; 2nd, 
 mixed sand ; 3rd, fine sand. ( App. LIX.) 
 
 213. The greatest difference in the hardness of 
 mortars of the rich limes, which the use of this or 
 that kind of sand is capable of occasioning, rarely 
 amounts to more than a fifth; but it exceeds one-third 
 with the mortars made from the hydraulic or emi- 
 nently hydraulic limes. That is to say, if we repre- 
 sent the maximum hardness in the two cases by 100, 
 the minimum will be not far from 80 in the first case, 
 and 60 in the second. 
 
 meter, one-third do. ; very fine sands and earths, two-sevenths do. 
 The same author gives an excellent practical method of determining 
 the proportions in which gravel, stones, and Bands ought to be mixed, 
 and which is very similar in principle to the process above describee 
 A measure is first exactly filled with the gravel or stones, and they 
 are shaken down in it so as to condense them into as small a bulk 
 as possible. By reason however of the interstices which still exist 
 between these stones, and which by the experiments just quoted have 
 been shown to be equal to one-half of the whole bulk, (when they are 
 of an average size of half an inch diameter or more,) it i- evident thai 
 there may still be added a huge quantity of .-and, without sensibly 
 increasing their volume. A similar measure full of sand is therefore 
 prepared, and part of its content- by degrees taken out and poured 
 amongst the stones, which are well Bhaken, to cause the sand to 
 penetrate and till up the voids perfectly, more and more sand being 
 added, as hist a- it settles into it- place, until it be observed that the 
 hulk of the whole begins to augment sensibly, which is a proof thai 
 all the voids are filled up. The quantity of sand remaining in the 
 second measure, will now indicate what proportion the gravel can 
 bear to be mixed \\ it 1 1 it, without augmentation of volume; and to thi- 
 mixture a >till finer kind may be added if thoughl proper, and the 
 quantity which the mixture will bear, estimated in the same, way. 
 
XI.] AND WEATHER. 8 ( J 
 
 214. When the sand reaches that degree of fine- 
 ness which constitutes the powders, its mixture with 
 the hydraulic or eminently hydraulic limes still pro- 
 duces excellent mortars, more especially when these 
 powders are derived from calcareous substances en- 
 dued with great cohesion, such as the marbles. The 
 quartzose powders, though not so efficient as sand of 
 the same nature, may still be very advantageously 
 employed ; but, it cannot be too often repeated, that 
 the intervention of any loamy or argillaceous particles 
 in the above-mentioned powders, robs them of their 
 qualities. (App. LX.) 
 
 Choice of Proportions. 
 
 215. In this case (as well as with regard to mortars 
 destined for immersion) we cannot, to speak exactly, 
 lay down a general rule, since each kind of lime 
 behaves, with respect to this or that sand, in a man- 
 ner which is peculiar to it. Nevertheless we are suf- 
 ficiently advanced to lay down certain limits, and to 
 determine a few points, so to speak, of the line which 
 it is impossible to trace throughout with exactness. 
 
 In order that this process may succeed fully, the two kinds of sand 
 mixed ought never to bear a less proportion to one another in the 
 diameter of their particles than ten to one, as unless that be the case, 
 thi' finer will not penetrate effectually. When therefore this condi- 
 tion is not fulfilled, or when we want to compare the condensation 
 obtained by mixing different proportions of common gravel and 
 sands, whose parts are of various dimensions, it will be best to make 
 the mixtures first, and then proceed with the experiment by ascer- 
 taining the comparative weights of the same measure filled with each, 
 as before explained in the note above quoted (to Art. 102.) — Tu. 
 c 3Jr. Higgins' Patent Stucco, made from the best stone lime, 
 
90 MORTAllS EXTOSED TO THE AIR [CHAP. 
 
 Case of the Rich Limes. 
 
 21 6. 1st, The resistance of mortars made from 
 verv rich limes slaked by the ordinary process, in- 
 creases from 50 up to 210 parts of sand to 100 of 
 lime in stiff paste, and beyond that decreases indefi- 
 nitely. 
 
 217. 2nd, The resistance of the same mortars, when 
 the lime has been slaked by immersion, or spontane- 
 ously, increases from 50 to 220 parts of sand to 100 
 of lime in stiff paste, and then diminishes indefinitely 
 beyond that proportion. 
 
 Case of the Simply Hydraulic Limes. 
 
 21 S. 1st, The resistance of mortars of hydraulic- 
 lime, slaked by the ordinary process, increases from 
 the proportion zero up to ISO parts of sand to 100 
 of lime in stiff paste, and then diminishes indefinitely 
 beyond that point. 
 
 219. 2nd, The resistance of the same mortars, when 
 the lime has been slaked by immersion, or spontane- 
 ously, increases from the proportion zero up to 17" 
 parts of sand to 1UU of lime in stiff paste, and then 
 diminishes indefinitely beyond that point. 
 
 slaked bj immersion, consisted of fifty-six pounds of coarse, and 
 forty-two pounds of fine sand (both washed), with fourteen pounds 
 of lime, and fourteen pounds of sifted bone-ash ; the whole wetted 
 and well incorporated together with as small a quantity as possible 
 of lime-water, and applied expeditiously. When a finer texture was 
 required, the coarse sand was omitted, and ninety-eight pounds of 
 fine sand used, and to this, fifteen pounds of lime, and fourt- 1 1. 
 pounds of bone-ash, were added. — Tn. 
 
XI.] AND WEATHER. 91 
 
 220. These results are sufficient to establish the 
 fact, that the best proportions are subordinate, not 
 only to the nature of the lime made use of, but also 
 to the mode of extinction to which that lime has been 
 subjected. We shall see hereafter, that there are a 
 vast number of other considerations on which they 
 depend. 
 
 Choice of the Mode of Slaking. 
 
 221. We have stated, in speaking of cements and 
 mortars when immersed, that the manner of slaking 
 the lime exerts a very remarkable influence on their 
 hardness. This influence is by no means so marked 
 in mortars exposed to the deteriorating action of the 
 air. We may, however, by using this or that process 
 with discernment, sometimes do as much as double 
 the resistance which we should have obtained by the 
 contrary process, a fact which well recompenses the 
 trouble of making a few experiments. 
 
 222. An examination of the Tables, in which the 
 facts which we have succeeded in collecting together 
 on this subject are recorded, points out at once the 
 same laws which we have already remarked, in respect 
 to cements and mortars when immersed ; that is to 
 say, that the three processes of extinction, arranged 
 in the order of pre-eminence, are, for the hydraulic, or 
 powerfully hydraulic limes, 1st, the ordinary process ; 
 2nd, by immersion ; 3rd, spontaneous ; and vice versa 
 for the rich, or slightly hydraulic limes. ( App. LXI.) 
 
 Tlie Manufacture or Manipulation. 
 '223. Many authors assert, that mortars are very 
 
gSt MORTARS EXPOSED TO THE .Mil [CHAP. 
 
 much benefited by being soured a long time, but 
 without precisely fixing anything. To put an end to 
 all uncertainty in this respect, we engaged in a new 
 course of experiments, which were further called for by 
 the insufficiency of those we had published in ISIS. 
 
 22 1-. Quartzose and calcareous substances acting 
 in "-eneral to more advantage in the state of sand than 
 as powders, with every species of lime, the mechanical 
 effect of a laborious trituration kept up beyond the 
 time necessary for the perfection of the mixture, can 
 obviously be only hurtful. But there is another point 
 of view in which the subject ought to be considered ; 
 it is that of the atmospheric influence upon the ingre- 
 dients of mortars, an influence which a long tritura- 
 tion keeps up and assists, by the frequent succession 
 of fresh contacts. 
 
 225. Now we have seen, that the hydraulic and emi- 
 ncntlv hydraulic limes, when exposed to the air, lose in 
 it a part of their qualities, while the rich limes acquire 
 new ones from it ; hence it follows, that a mortar of rich 
 lime is the only one which can gain anything by being a 
 long time soured, and this is also proved by our more 
 recent experiments. They show, in fact, that a mix- 
 ture of 150 parts of sand and 100 parts of this lime, 
 slaked by immersion, and measured in paste, having 
 been kneaded and worked up afresh with additional 
 water every eight days during five months consecu- 
 tively, acquired after one year, an absolute resistance 
 of 5 k . 13 per centimetre square ; d while, in the case 
 of the ordinary manipulation, the same mixture only 
 
 d Equal to 77.3 pounds Avoirdupois per English square inch. — Tk. 
 
XI.] AND WEATHER. 93 
 
 reached 4Mi ; e but, however sensible this difference 
 is, it is by no means commensurate with the labour 
 which it cost. 
 
 226. It is therefore only by means of renewing the 
 contacts, and favouring the action of the atmosphere, 
 that a long-continued trituration can become favour- 
 able to mortars of rich lime ; and this furnishes a 
 complete vindication of the Lyonese method, which 
 consists, as is well known, in preparing large heaps 
 of mortar beforehand, from which they take succes- 
 sively as much as is wanted for the day's consumption, 
 rendering it ductile by adding water. 
 
 227. But we see at the same time, that the same 
 method may be ill-judged in a country where the lime 
 may be hydraulic or eminently hydraulic. 
 
 228. Everything which has been said of the slak- 
 ing of lime, and the consistency of the mixtures, in 
 treating of mortars and cements for immersion, applies 
 exactly to mortars exposed to the air. The mortars 
 of hydraulic lime may lose four-tenths of the ultimate 
 hardness of which they are capable, when, instead of 
 that stiff consistency of which we have spoken, we 
 make use of that adopted by the masons. 
 
 229. Mortar in every season ought to be prepared 
 as much as possible under cover, whether it be to 
 avoid the rapid desiccation which takes place in sum- 
 mer, or to obviate the still more serious inconvenience 
 in the rainy season. In the latter case, we ought to 
 deviate a little from the principles which we have laid 
 
 c Equal to 58.93 pounds Avoirdupois per English square inch 
 — Tk. 
 
94 MORTARS EXPOSED TO THE AIR [CHAP. 
 
 down in the preceding pages, and choose the hydraulic 
 lime slaked by immersion, in preference to that pro- 
 duced bv the ordinary mode ; and this in order to 
 have it in our power at pleasure to absorb the water 
 contained in the wet sand ; without this plan, it is 
 impossible to obtain a stiff mortar. 
 
 230. In summer, on the contrary, the lime in paste 
 is not always sufficient to moisten the sand, which is 
 sometimes hot. It then becomes indispensable to add 
 water, but gradually, and with the greatest caution. 
 One could hardly believe, without witnessing it, how 
 very small a quantity is sufficient to drown the mix- 
 ture. (App. LXII.) 
 
 Application. 
 
 231. It is quite evident, that a very stiff mortar 
 cannot be used with dry and absorbent material?. 
 When we have materials of this kind, they must be 
 watered without ceasing, and kept in a perfect and 
 permanent state of imbibition. The whole secret of 
 good manipulation and right employ, is condensed in 
 the following precept : " Stiff mortar, and materials 
 soaked.'' Our bricklayers, on the contrary, seem to 
 have taken for their motto, "Dry bricks, and drowned 
 mortar.'* 
 
 232. It is true, that to build in the way here 
 understood, we must change certain habits ; as, for ex- 
 ample, never after the first supply have to introduce 
 mortar between stones too close to one another, but 
 to lav under each one, in the first instance, a sufficient 
 
XI.] AND WEATHER. 95 
 
 quantity to allow those at the side to supply them- 
 selves from it when it is battered down in bedding it. 
 
 233. The mason's hands will soon be covered with 
 sores, if he do not at the same time take some pre- 
 cautions to guard himself from the action of the 
 lime. Liquid tar remedies this very effectually ; f it 
 is sufficient to rub the hand with it frequently 
 during the day: the thin coating which remains 
 sticking to the skin acts as an impermeable glove. 
 (App. LXIII.) 
 
 Precautions to be taken after Application. 
 
 234. In general, all mortars become pulverulent 
 when, after being applied, they are exposed to a rapid 
 desiccation. The influence of such a desiccation be- 
 comes the more fatal, the more erninentlv hvdraulic 
 the mortars are. They may then lose four-fifths of 
 the strength which they would have acquired by 
 drying slowly. It is therefore proper to water the 
 masonry when we build during the hot season ; and 
 this in such a way, as never to permit the mortar to 
 whiten, and thus part with the water necessary for its 
 solidification/ (App. LXIV.) 
 
 f The necessity for this preventive is obviated in England by 
 the pallet or board (called the " hawk"), used by plasterers for 
 mixing 6mall quantities of stucco as they apply it, and for catching 
 such as may fall ; it consists merely of a piece of plank about a 
 foot square, with a handle about six or seven inches in length, 
 fixed perpendicularly underneath the middle of it, by which it is 
 grasped. — Tr. 
 
 g It was found by Mr. Higgins to be injurious to chalk mortar to 
 be kept too long in a very damp state. The object here intended, is 
 
MORTARS EXPOSED TO THE AIR [CHAP. 
 
 Influence of Time. 
 
 235. Mortar a hundred years old is still in its in- 
 fancy. This saying of the masons is the result of 
 the daily observations which they have the opportu- 
 nitv of making in demolitions. It is seldom in fact 
 that we meet with good mortars of rich lime, except 
 in the foundations or masonry of buildings of four or 
 five hundred years old. What is it that determines 
 such a tardy solidification ? It is a thing which it 
 appears difficult to account for ; however, there is one 
 thing which it is not at all difficult to apprehend, 
 and that is, that a mortar which does not harden 
 for four or five hundred years, is to us much the 
 same as if it never hardened at all. h (App. LXV.) 
 
 236. As regards hydraulic, or eminently hydraulic 
 mortars, numerous experiments which we have col- 
 lected prove, that when exposed to the air in small 
 bulk, they in a very short time (eighteen to twenty 
 months) attain, if not the ultimate degree of hard- 
 
 iv to retard the desiccation of the mortar. Colonel Raucourt 
 de Charleville recommends straw-mats to be suspended in front of 
 the walls as the best means of effecting this. It is an important 
 fact too, that the mortars composed of the very hydraulic limes 
 used in the " active" or imperfectly-slaked condition, are best 
 adapted to resist the injurious effect of too speedy drying. This 
 observation of the above author corresponds with my own experi- 
 ments on this subject. — Tr. 
 
 h " Colonel Raucourt de Charleville is of opinion, that in donates 
 not subject to frost, atmospheric vicissitudes, so far from being inju- 
 rious to mortars, increase their induration, and that in a greater 
 degree the h ss hydraulic the lime of which they are composed." — 
 / i, p. 1 12. 
 
XI.] AND WEATHER. 97 
 
 ncss of which they arc susceptible, yet at least a 
 condition differing so little from it, that we are en- 
 abled to predict with certainty what they will ulti- 
 mately become. 
 
 237. Thus the influence of ages may modify, but 
 not overturn, the relations in respect to durability 
 established by our observations. 
 
 H 
 
CHAPTER XII. 
 
 OF CALCAREOUS CEMENTS AND MORTARS SUBJECTED TO 
 THE CONSTANT INFLUENCE OF A DAMP SOIL. 
 
 i 28S. With respect to cements, we may refer to all 
 that has been said concerning the proportions, the 
 mode of slaking, and the manufacture, in the case of a 
 constant immersion ; and with regard to mortars, to all 
 that has just been said in reference to the case of ex- 
 posure to the weather, with the exception of the follow- 
 ing modifications. 
 
 o 
 
 Size of Sa)id. 
 
 - ?9« When the quartzose or calcareous sands are of 
 that degree of fineness which constitutes powders, their 
 presence is injurious to the hydraulic and eminently 
 hydraulic limes ; and this effect is the most remarkable 
 in regard to the calcareous sands derived from the 
 softest kind of stone. 
 
 Process of Extinction. 
 
 240. The varieties of hardness resulting from a 
 difference in the modes of slaking employed, conform 
 to the order laid down, but in general in a more 
 marked way than in the case of exposure to the air. a 
 
 • Vide Art 222. 
 
CEMENTS AND MORTARS, ETC. 99 
 
 Proportions. 
 
 241. These are essentially modified agreeably to 
 the following observations : — 
 
 1st. The resistance of mortars made from very rich 
 limes slaked by the ordinary process, continually di- 
 minishes, reckoning from 50 to 190 parts of sand and 
 more, to 100 parts of lime in paste. 
 
 2nd. The resistance of the same mortars when the 
 lime has been slaked by immersion, remains very 
 nearly the same, from 50 to 130 parts of sand to 100 
 parts of lime in paste, and diminishes indefinitely 
 beyond that proportion. 
 
 3rd. The resistance of the same mortars, when the 
 lime has been slaked spontaneously, remains very 
 nearly the same, from 50 to 200 parts of sand to 100 
 parts of lime in paste, and then decreases indefinitely. 
 
 4th. The resistance of hydraulic mortars, no mat- 
 ter by what process slaked, is augmented by very 
 small differences, from zero up to 90 parts of sand to 
 100 of lime in paste, and remains constant from that 
 proportion up to 240 parts of sand. 
 
 Employ. 
 
 242. Cements intended to bind together the parts 
 of underground masonry, are used with the same 
 precautions, and the same care, as the mixtures of 
 lime and sand. They lay hold but feebly of the stone 
 or brick when compounded in exact proportions. We 
 augment their adherence by giving them a slight ex- 
 
 ii 2 
 
100 CEMENTS AND MORTARS [CHAP'. 
 
 of limo, but. this is always at the expense of their 
 «>wn proper cohcsion. b 
 
 b Tor foundations and works of that kind, the use of concrete as 
 a substratum in dangerous soils seems in England to be fast super- 
 seding every other method, and it offers so valuable a resource in so 
 many difficult situations that I cannot omit the opportunity of doing 
 the reader a service, bv giving a short account of its nature 
 and preparation. Concrete is a composition of stones or rubble and 
 sand with fresh-burned stone lime (ground to powder without slaking), 
 in the proportions of from one-fifth to one-ninth of lime, to one of the 
 mixture of rubble and sand. These ingredients should lie \\ ell blended 
 together dry, and as small a quantity of water added as will bring 
 them to the consistency of mortar, and then, after turning over the 
 materials with the shovel once or twice, thrown as quickly as possi- 
 ble into the foundation from a height of eight or ten feet It sets 
 very quickly, so that it is desirable that the mixture should be 
 made at, or close to the height from which it is precipitated, and 
 after being expeditiously spread and brought to a level, or puddled, 
 it ought not to be again touched. The best proportions of admix- 
 ture of the stones and gravel or sand, are such as produce the great- 
 est possible condensation, and depend therefore upon the dimensions 
 of both ; and the principles by which these proportions may be de- 
 termined with accuracy will be found in note to Art. 211, it being 
 remembered that the greater the condensation, or the greater the n al 
 bulk of the materials packed into a given space, the less the quantity 
 of cementing matter necessary to bind them together. The concrete 
 osi d near London is composed of Thames ballast, containing about 
 two of stones to one of >and, which proportion Mr. Godwin, the 
 author of a valuable essay on this composition, considers to be the 
 best ; and as the size of all the stones used is limited to the bigness 
 of a hen's egg (all beyond that dimension being broken), it will be 
 that this practical result is in perfect accordance with the ex- 
 periment* referred to in the note above quoted. The quantity of lime 
 (if hot from the kiln, and perfectly well burnt and pulverised) should 
 l.e such as is sufficient to form good mortar with the $tmd (only), 
 which i> the simplest rule to go by. afl by it the exact proportion.* in 
 
XII.] SUBJECTED TO A DAMP SOIL. 101 
 
 every case can be decided according to the nature of the materials, 
 and the energy of the lime used, according to the experience and 
 judgment of the architect who employs them. I have not heard of 
 concrete being employed under water, but when once consolidated, 
 it may be exposed immediately to its action without risk. In setting 
 it expands in the same manner as hydraulic lime (vide App. XLIX, 
 par. 3), which renders it very valuable in some situations. This in- 
 crease of dimensions amounts to three-eighths of an inch in a foot in 
 height on the first setting of the concrete, and it continues to expand 
 insensibly for a month or two afterwards. It is proper to add, that 
 this expansion follows a previous condensation of about one-fifth in 
 bulk, by which the ballast and lime are found to be contracted after 
 being incorporated together. — Tr. 
 
CHAPTER XIII. 
 
 OF THE VICISSITUDES TO WHICH CEMENTS AND MORTA15S 
 MAY BE EXPOSED, AND OF THE CONSEQUENCES. 
 
 QU3. Some mortars and cements which solidify tole- 
 rably in the water, lose part or the whole of their 
 cohesion when exposed to a dry and warm air. This 
 happens generally with those whose elements do not 
 suit one another perfectly ; for instance, the cements 
 of rich limes and feebly energetic substances, such as 
 the arenes, the psammites, clays, &c. ; the mixtures 
 of feebly hydraulic limes with inert materials, &c. 
 The deterioration is more particularly marked in re- 
 spect to the exterior surface, which the dissolving 
 action of the water has already caused to undergo an 
 incipient alteration ; these parts lose all their con- 
 sistency. 
 
 244. Mortars formed from the hydraulic or emi- 
 nently hydraulic limes, whose solidification takes place 
 in a damp soil, behave equally well in the open air, 
 and in the water. 
 
 245. In general, most kinds of cement which have 
 well hardened under a damp soil, stand equally in the 
 water, but they behave variously in the open air ; some 
 resist, others are altered by it. We are unable to say 
 to the presence of what principles these differences are 
 to be attributed. (App. LXVI.) 
 
 246. The mortars of hydraulic or eminently by- 
 
CHANGES OF CEMENTS AND MORTARS, ETC. 103 
 
 draulic limes, and in general most cements which 
 have acquired considerable hardness in the open air, 
 will retain it indefinitely in the water, or under a 
 damp soil. 
 
 247. The simple mixtures of rich lime with inert 
 sands, whose hardness is merely due to their drying in 
 the air, become completely decomposed in the water. 
 
 248. In general, all cements of rich limes resist 
 frosts but imperfectly ; they give way like hard stones 
 by irregular cleavage. This action of the frost is 
 considerably weakened, and may even be entirely 
 avoided, by mixing a certain quantity of pure sand 
 with the powdery ingredients which arc employed in 
 their composition/ (App. LXVIII.) 
 
 249- All the mortars of rich limes, and coarse and 
 
 a In India, where the very speedy decay of mortars and cements, in 
 some situations, appears to be attributable to frequent alternations of 
 dryness and humidity (vide note to App. LXVIII.), I found the best 
 preventive was a coating of tar, which I tried with a view to check 
 the transition of moisture. Part of the surface of a very damp wall, 
 the plastering of which had been long remarked for its repeated 
 and very early failures, was newly stuccoed with the usual composi- 
 tion (4 of rich lime to 5 sand), and after it had dried thoroughly, a 
 portion of it, containing about 50 superficial feet, was painted with a 
 double coating of common tar. This was renewed by a third coat 
 about nine months after, the heavy rains of the monsoon having 
 intervened ; and at the end of eighteen months, at which time I was 
 compelled to quit the station, the whole Mas perfectly sound in 
 every part. The remaining parts of the stucco which had not 
 been thus defended by the tar, began to decay in little more than a 
 month after first completion, and having been restored throughout 
 after a total dilapidation, were again (a second time) in complete 
 ruin when the tarred surface received its third coat ; that is, in nine 
 months after it was hist applied. (Vide App. LXVII.) — Tit. 
 
i'^ CHANGE? OF CEMENTS AND MORTAR?, [CHAT. 
 
 verv pure sand, resist the winters of our climate when 
 they have attained a certain degree of solidification ; 
 in the contrary case, they are variously acted upon, 
 and this in relation to the proportion of lime they con- 
 tain. Experience furnishes the following indication- 
 on this subject : — 
 
 1st. Everv mortar prepared in the month of April, 
 with rich lime slaked by the ordinary process, is at- 
 tacked the following winter, when it contains less than 
 - . parts of sand to 1<X> of lime in pa- 
 
 2nd. It is attacked in the same way, when it con- 
 tains less than 160 parts of sand to KX) of the same 
 lime, in paste obtained by immersion. 
 
 3rd. It is attacked in the same way, when it con- 
 tain? les? than 240 part? of ?and to 1<X) of the same 
 lime in paste, slaked spontaneously. 
 
 -2j<). After two years the danger is past, and after 
 six years the most severe frosts are powerless, except 
 the elements of the sand made use of be themselves 
 liable to injury, and consequently subject to be indefi- 
 nitely subdivided, as far as pulverizat: 
 
 851. With r eg ivd to hydraulic and eminently hy- 
 draulic mortars, six to seven months' age is sufficient 
 to place them beyond its reach, whatsoever may be 
 
 b Several authors agree in the observation, that stuccoes which 
 have to bear exposure to the action of the air. wet, and fro&t, ought 
 not in any climate to be laid on in successive coats as in in-door 
 work, as their adherence to one another is feeble, and they have a 
 
 ■arate. The joints of the masonry should be (' 
 out, the bricks well soaked with water, and a angle coat 
 of eminently hydraulic lime and gnu with sand appliedj 
 
 and afterwards floated. — Tr. 
 
XIII.] AND THEIR CONSEQUENCES. 105 
 
 the proportion in which they may be compounded ; 
 but they resist nevertheless in proportion to the 
 quantity of sand they contain. That is to say, that 
 the " poorest" are attacked the last, if any can be. 
 (App. LXIX.) 
 
 252. In the covered parts of buildings, the mortars 
 of rich limes have not to undergo these vicissitudes, 
 but they do not become better on that account. The 
 maximum limit of sand proper for them in that case, 
 is from 55, 125, or 175 parts to 100 of lime in paste, 
 according as it is obtained by the ordinary extinction, 
 by immersion, or spontaneously. On referring to the 
 maximum limits laid down for the case of exposure to 
 the weather in Chapter XL, we shall easily deduce 
 therefrom, that the same atmospheric changes are 
 favourable to mortars loaded with sand, and on the 
 other hand are injurious to those in which the lime 
 predominates. 
 
CHAPTER XIV. 
 
 INFLUENCE OF BEATING ON THE RESISTANCE OF 
 MORTARS IN GENERAL. 
 
 253. Mortar, considered as a plastic material, 
 fit for moulding, may be made to take every possible 
 form in moulds or sbapes. We are besides able to 
 give it the appearance of stone, by making it with 
 fine colourless sand, or rather with fine calcareous 
 powders derived from hard stones. 
 
 254. Mortar contained in a mould may be beaten 
 or rammed in the manner of pise, a and acquires by 
 that means great compactness ; but as an increase 
 of resistance does not always result from this, it 
 is as well to study the effects of this ramming, and 
 to distinguish those cases where it may occasion more 
 evil than benefit. 
 
 2.55. In order that any material be beaten with 
 effect, it is necessary that it should possess a certain 
 degree of consistency, which is a mean between com- 
 plete pulverulence, and that state of ductility which 
 constitutes a firm paste. In fact, we must be aware 
 that no compression is possible, when the material is 
 
 * Pise, a mode of building formerly in use, whereby wall- were 
 formed by ramming and beating down earth, day, &c between 
 upright planks. — Tk. 
 
INFLUENCE OF BEATING, ETC. 107 
 
 able to escape from under the rammer ; and this is 
 well understood by the builders in pise, who never 
 employ any but earth slightly moistened. Now, wc 
 always have it in our power to prepare our mortar in 
 this way, whether immediately, or far better, leaving 
 the mortar after it has been worked in the ordinary 
 manner, to undergo desiccation to a proper extent. 
 
 256. The successive approximation of the particles 
 of the compressed material to one another, necessa- 
 rily determines a foliated structure, which though it 
 may not be perceived is nevertheless real. Analogy 
 would lead us to conclude, that in every possible 
 case, a body thus formed ought to oppose a greater re- 
 sistance to a tractile force in proportion as its direc- 
 tion forms a smaller angle with the plane of the 
 laminae ; however, experience shows that this in 
 general does not take place. The following is what 
 has been determined in this respect : — 
 
 1st. Beating has the effect of augmenting the abso- 
 lute resistance of mortars of rich limes and pure 
 sand in every case, but in an unequal manner. The 
 greatest resistance assumes a direction perpendicular 
 to the planes of the laminae when the mortars are 
 buried in a damp soil, immediately after their fabrica- 
 tion. It remains parallel to these same planes when 
 the mortars have been exposed to the atmospheric 
 influence. 
 
 2nd. The effect of beating is not constantly useful 
 to mortars of hydraulic or eminently hydraulic limes, 
 and calcareous or quartzosc sands or powders, except 
 in the case when these mortars arc used under a 
 
108 INFLUENCE OF BEATING [CHAP. 
 
 damp soil. The greatest resistance is then in a 
 direction perpendicular to the planes of these lamiine, 
 as with the mortars of rich limes ; but in the air, 
 the superiority of the mortars which have been 
 beaten, over those which have not, is only exhibited 
 in one direction, and that is parallel to the plane of 
 the lamina?. 
 
 3rd. Beating becomes injurious in every case, 
 when the hydrates of the hydraulic or eminently 
 hydraulic limes are employed without admixture, and 
 subjected to the influence of a damp soil ; and is 
 favourable to it only in the direction parallel to the 
 lamina? when the stuff dries in the air. 
 
 257. In engaging in the researches which form 
 the subject of this chapter, our object has been to 
 study the properties of mortars of hydraulic limes 
 considered as plastic substances. The numerous 
 casts which we have moulded, both in bas-relief, and 
 in alto relievo, prove, as we have said, that mortar 
 receives and retains impressions well. These oasts 
 have stood the rough weather of several winters with- 
 out the least accident; their hardness has continu- 
 ally been on the increase, and a kind of varnish, with 
 which time has covered them, gives them actually so 
 strong a resemblance to common stone, that the most 
 practised eye mistakes them for it. 
 
 •2.~>*. There remains but one problem to be solved, 
 thi- is, to discover a means of hastening the set of a 
 mortar, without injuring its future qualities; and 
 this, in order to avoid being obliged to multiply tli 
 moulds indefinitely for the same casting. This las! 
 
XIV.] ON MORTARS I\ T GENERAL. 109 
 
 point seems difficult ; Loriot's process is altogether 
 insufficient, and besides produces only mortars of 
 bad quality. b (App. LXX.) The natural cements, 
 which harden almost instantly in the air and in the 
 water, when worked up like plaster (of Paris, Tu.), 
 are subject to the inconvenience of being* tinged 
 brown. Such as we could fabricate artificially (" de 
 toutes pieces"} by calcining mixtures of lime and 
 clay free from iron, (Chapter XV.) do not stand the 
 weather. 
 
 259« But henceforth, mortar of hydraulic lime may 
 be employed as a plastic substance in a multitude of 
 cases, in which the number of moulds ceases to be a 
 difficulty. Such is the case when we have to prepare 
 artificial stones bearing mouldings, vases, or orna- 
 ments of any kind susceptible of formation by the 
 rectilinear or circular movement of a profile ("cali- 
 bre"). It is evident that it will then answer to set 
 the mould in a trench, and run the profile along 
 the clayey paste, prepared and arranged for that pur- 
 pose. The economy which such a process would 
 
 b Colonel Raucourt de Charleville found that a good liquid mor- 
 tar for grouting was composed of eminently hydraulic lime and fine 
 sand run into the joints immediately after mixing, and while still fluid ; 
 it hardens immediately without shrinking, and solidifies all its water. 
 Smeaton formed an excellent grouting of pouzzolana and lime, in 
 the proportions constituting mortar (1 lime to 1 pouzzolana) m 11 
 beaten and incorporated together, and then tempered with water 
 till sufficiently dilute to pour into the joints of his work. In the 
 course of a month this composition became of a moderate stony 
 hardness under water, so that he was obliged to break the vessel in 
 which it was contained to get at it — Tr. 
 
110 INFLUENCE OF BEATING, ETC. 
 
 introduce into our ornamental constructions is indeed 
 incredible. 
 
 g6(X In support of what we have just advanced, 
 we may quote the honourable testimony of the Society 
 of Encouragement. It has welcomed our endeavours 
 favourably, and has been pleased to signify its ap- 
 proval, by presenting us with a gold medal, at the ses- 
 sion of 29th of October, 1833. 
 
CHAPTER XV. 
 
 OF THE NATURAL CEMENTS. 
 
 2Gl. When the proportion of clay in calcareous 
 minerals exceeds 27 to 30 per cent., it is seldom that 
 they can be converted into lime by calcination ; but 
 they then furnish a kind of natural cement, which 
 may be employed in the same manner as Plaster of 
 Paris, by pulverizing it, and kneading it with a cer- 
 tain quantity of water. 
 
 262. There are some natural cements which do 
 not set in water for many days, and some which har- 
 den in less than a quarter of an hour ; these last are 
 the only ones which have been made use of at present. 
 Though very useful in circumstances where a quick 
 solidification is indispensable, they are far from afford- 
 ing, in ordinary cases, the advantages of hydraulic 
 mortars or cements of good quality. In fact, they 
 merely adhere to the stone owing to the roughness of 
 its surface, and the entanglement resulting from it ; a 
 and, however dexterous or experienced the workman 
 
 a This statement must, I imagine, be understood to apply only 
 to cements which harden in contact with the bricks under water, 
 because the adhesion of such as dry in the open air is well known 
 to be much greater than what would be caused merely by asperities 
 of the surface. It is not uncommon to see from 20 to 30 bricks 
 stuck to one another by Roman Cement, and projecting at right 
 angles from the side of a wall, as a proof of the excellence of the 
 composition ; and an instance has recently been mentioned to me, 
 in which 33 bricks were successfully supported in this manner. 
 
11-2 NATURAL CEMENTS. [CHAP. 
 
 may be who makes use of them, he will be unable to 
 connect the different parts of his masonry in one con- 
 tinuous bond by means of it. 
 
 L 2G3. That which is in England very improperly 
 termed Roman Cement, (App. LXXI.) is nothing 
 more than a natural cement, resulting from a slight 
 calcination of a calcareous mineral, containing about 
 31 per cent, of ochreous clay, and a few hundredths of 
 carbonate of magnesia and manganese. A very great 
 consumption of this cement takes place in London, 
 but its use will infallibly become restricted, in propor- 
 tion as the mortars of eminently hydraulic lime shall 
 become better known, and in consequence better ap- 
 preciated. 
 
 26-t. Very recently, natural cements have been 
 found in Russia, and in France ; we may compose 
 them at once, by properly calcining mixtures made in 
 the average proportions of 66 parts of ochreous clay 
 to 100 parts of chalk. It is fair however to admit, 
 that no artificial product yet obtained has been able 
 to match the English cement in point of hardness. 
 
 L 26o. We remarked (in Chapter II.) that the pure 
 calcareous substances when imperfectly calcined, be- 
 came converted into sub-carbonates, possessed of 
 certain properties. These properties are to afford a 
 
 Now, if we assume the weight of a brick, and its corresponding joint 
 of cement, to be six pounds, and their thickness, when the bricks 
 were joined one to another in the manner above alluded to, (in 
 which the longest dimension of the brick was placed vertically,) at 
 21 inches, then the cohesive force necessary to unite the first brick 
 to the wall, with sufficient firmness to bear the strain occasioned 
 by tin weighJ of the remaining 32 supported by it, poBl have been 
 neazij U]\\». par square inch; or equivalent to a direct load of 
 llba. upon it- whole surface of about 4-0 square inches — Tn. 
 
XV.] NATURAL CEMENTS. 113 
 
 powder, which when kneaded with water in the same 
 way as Plaster of Paris, acquires in it at first a con- 
 sistency more or less firm, but which does not con- 
 tinue its progress at the same rate. 
 
 266. The argillaceous limestones, and the artificial 
 mixtures of pure lime and clay, in the proportions 
 requisite to constitute hydraulic lime by the ordinary 
 calcination, become natural or artificial cements when 
 they have been subjected merely to a simple incan- 
 descence, kept up for some hours, or even for some 
 minutes. This result, which has often occurred in the 
 course of our first experiments in burning the artifi- 
 cial hydraulic limestones, has been equally observed 
 in Russia, by Col. Raucourt ; and M. Lacordairc, 
 Engineer of Roads, has not only just verified it with 
 respect to the different argillaceous limestones of 
 the neighbourhood of Pouilly, but has also made a 
 useful and happy application of it in the works which 
 he is directing at the junction of the Burgundy canal ; 
 both in transforming these limestones into natural 
 cements, and in turning to account the large quantity 
 of half-burnt lime which is found in the upper layers 
 of the kilns, when the intensity and duration of the 
 heat is so regulated, as not to exceed the limit proper 
 for the lower strata of the change. 
 
 9,61. The history of these new cements will not be 
 complete, till authentic and multiplied experiments 
 shall have established, both the manner in which they 
 behave in the open air, and stand frost, and the 
 degree of adherence with which they unite to the 
 building stone. We hope that Mr. Lacordaire will 
 soon solve these important questions. 
 
 i 
 
CHAPTER XVI. 
 
 OF THE ANTIQUE MORTARS COMPARED WITH THOSE 
 OF MEDIUM AGE AND MODERN MORTARS. 
 
 268. The Egyptian monuments present beyond 
 doubt the most ancient and most remarkable examples 
 which we can quote of the use of lime in building-. 
 The mortar which binds the blocks of the Pyramids, 
 and more particularly those of Cheops, is exactly 
 similar to our mortars in Europc. a That which we 
 
 a By the kindness of my friend Dr. Maleolmson, of the Madras 
 Medical Establishment, to whom I am indebted for many important 
 suggestions and valuable assistance throughout the progress of this 
 work, I have been put in possession of some specimens of mortar 
 taken by himself from the joints of the largest of the Pyramids 
 (that of Cheops), and which, interesting as it is from its great an- 
 tiquity, is the more so from some peculiarities in its external ap- 
 pearance and its chemical constitution, the former of which I shall 
 here notice ; as from the account of it contained in the text, I am in- 
 duced to think that the cement submitted to Mr. Vicat's examina- 
 tion could not have been taken from the same edifice as that which 
 I am about to describe. 
 
 The specimens which I examined were of a whitish, or pale cream 
 colour where fractured, and the broken surface exhibited a number 
 of white specks, which, on attentively observing the action of strong 
 nitric acid upon them under a microscope, were found to be in- 
 soluble. As the cement Mas also studded throughout with nume- 
 rous crystals of the sulphate of lime, I satisfied myself that these 
 specks were occasioned by the fracture of (lie smaller grains of it, 
 
ANTIQUE AND MODERN MORTARS COMPARED. 115 
 
 find between the joints of the decayed buildings at 
 Ombos, at Edfou, in the Island of Phila, and in other 
 places, gives evidence by its colour, of a reddish very 
 fine sand mixed with lime in the ordinary propor- 
 tions. The use of cements was therefore already 
 known two thousand years before our time ; perhaps 
 it would be easy to carry that epoch still farther 
 back, were we to consult the ancient monuments of 
 India, and the Sanscrit books, if they speak of the 
 ancient relations of Egypt with that country ; but 
 this would be to attach too much importance to an 
 inquiry, more curious than useful. 
 
 269. In confining the use of cements to filling 
 
 and not, as I at first supposed, by the unreduced particles of an 
 imperfectly flaked lime. The crystals above alluded to were of 
 various sizes, the largest I saw being half an inch long by a quarter 
 in breadth ; and most of them corresponded in every respect 
 with the well-known characteristics of selenite, but other portions 
 were of a more granular earthy structure, being also opaque. In 
 .general appearance, with the exception of containing these crystals, 
 the cement was exactly similar to a common mortar of the present 
 day. I also observed, here and there, fragments of the size of a 
 small pea downwards, of an indurated ochreous clay, in some cases 
 of a dark red, or purplish colour, similar to that of an over-burnt 
 brick — in other places yellow ; and in one instance I found this clay 
 surrounded by, and imbedded in the crystals of the sulphate of lime, 
 of which it formed a kind of nucleus. Now, as the analysis of this 
 cement proves it to contain no siliceous matter, I have no doubt 
 that the particles of clay which exist in it are fragments which ac- 
 cidentally adhered to the sulphate of lime when it was dug out of 
 the earth, and that the mortar is a composition of rich lime and 
 roarsely-powdered gypsum, which has been used as a substitute for 
 sand, in the proportion of about one of the former (by weight) to five 
 of the latter. Its appearance quite corresponds with this supposi- 
 tion, and for a cement of that kind it possesses considerable tenacity. 
 
 I 2 
 
116 ANTIQUE AND MODERN [CHAP. 
 
 the narrow joints of their courses, the Egyptian! 
 appear to have foreseen the opposing influence which 
 an always scorching atmosphere exerts on the har- 
 dening of calcareous compounds. Time has shown 
 us, how their prudence, or chance, has aided them in 
 this respect : for the Roman works on the banks of 
 the Nile already leave no traces, whilst, after forty 
 centuries, many of the Egyptian temples exhibit them- 
 selves to our admiration untouched. 
 
 270. Besides, a masonry of small materials would 
 not suit a people, who covered the walls of their 
 public buildings with bas-reliefs, and thus confided 
 
 The specific gravity of a lump about the size of a walnut I found to 
 be 1.98. 
 
 The particulars of the analysis (by Dr. Malcolmson) of this inte- 
 resting specimen will be found in Appendix LXXIL, one of the re- 
 sults exhibited by which is more particularly noticed at the end of 
 the note to Appendix XXXI. In the mean time, as the possibility of 
 the formation of the crystals within t/a ccnunt, by the mutual ex- 
 change of constituents, of sulphate of soda and the nascent carbonate 
 of lime, (the resulting carbonate of soda being supposed to have 
 been subsequently washed out,) has been suggested, it would be in- 
 -•ing to inquire whether, in accordance with my own explana- 
 tion, gypsum be procurable anywhere within reach of the Pyramids; 
 and if so, whether, as is frequently the case, it be in connexion with 
 an argillaceous deposit? The absence of sand in a locality where 
 such an abundance is now to be met with, is also a remarkable 
 circumstance. 
 
 In reference to the above suggestion, I ought not to omit to 
 mention, that the cement was found to contain a considerable pro- 
 portion (18J per cent) of soluble salts; principally the sulphate of 
 lime, but with also a small quantity of the sulphate, and a trace of 
 the muriate of soda. These last were, no doubt, derived from the 
 water, which I am informed is in no place anything like pure in the 
 plains near the Pyramids. — Tit. 
 
XVI.] MORTARS COMPARED. 117 
 
 to sculpture the history of their manners, their arts, 
 their battles, and their conquests. Unburnt bricks 
 cemented with clay sufficed for simple habitations, 
 and beneath a constantly unclouded sky such a me- 
 thod of building was equally safe, as expeditious and 
 economical. 
 
 271. It was in the country of the fine arts, in that 
 Greece so fruitful in ingenious inventions, that in- 
 dustrv, favoured by the climate, began to vary the 
 application of calcareous cements, and to apply them 
 to a number of uses, of which Egypt did not furnish 
 an example. At the same epoch in which the roof 
 of the Areopagus, built of earth, was exhibited as a 
 curious antique at Athens, the houses of the simple 
 citizens were ornamented with stuccoes, which for 
 whiteness, hardness, and polish, were comparable to 
 the Parian marble, and their terraced roofs defended 
 them from the action of the elements. They con- 
 structed with flints, or other hard stones of small size, 
 walls, which were not inferior in hardness to free- 
 stone ; and the artificial pavements were brought 
 to such perfection, that in a few instants they would 
 absorb all the water with which they washed them : 
 thus the slaves walked over them barefooted, without 
 being incommoded by damp or cold. Such, in the 
 times of Pericles and Plato, was the progress of the 
 arts among the same people, who seven centuries and 
 a half before contented themselves with erecting a 
 monument of clay on the Sigcian promontory to their 
 bravest hero ! 
 
 272. Italy soon witnessed the spread of Oriental 
 customs through her. Greek artisans also flocked 
 thither from all parts. The Romans, in turn, were 
 
118 ANTIiJl'i: AND MODERN [CHAT. 
 
 able to instruct themselves from the writings of Anaxa- 
 goras, Agatarchus, Metagcncs, Phytheus, Thcocides, 
 and others. Fussitius published the first book of 
 Architecture which appeared in Rome. After him 
 came Terentius Yarro, Publius Septimius, and lastly 
 Yitruvius, who lived under Augustus, whose archi- 
 tect he was. His work, the onlv one which has 
 reached us, is the more precious as it contains, ac- 
 cording to the confession of the writer himself, all 
 that the Greeks knew of the art of building. Pliny 
 the Elder in his natural history, and Palladius (Rut. 
 P. iEmil.) in his treatise " De re Rusticii," have 
 added nothing to what Yitruvius had said before 
 them. We are even tempted to believe, that in more 
 than one place they confined themselves to copying 
 him. 
 
 27S. It is therefore Yitruvius whom we ought to 
 consult, when we want to clear up anv point of contro- 
 versy regarding the architecture of the Greeks and 
 Romans. Rut the monuments erected by these people 
 speak still more plainly than their books ; and what 
 remain to us in that way, are sufficient to clear up all 
 the difficulties started on that subject. 
 
 274. The Romans, as we have already observed, 
 considered that lime of the finest qualitv, which 
 was furnished by a marble of the hardest and most 
 pure kind. Hydraulic lime, judging from the silence 
 of Yitruvius, was totally unknown to them, at least ai 
 regards its properties. Thus they were unable to do 
 without pouzzolana, when engaged on hydraulic works 
 of great importance, such as a pier or jetty into the 
 sea. They were besides so well aware that common 
 lime and sand only could never set under water, that 
 
XVI.] MOKTAItS COMPARED. 119 
 
 after having laid the foundations of the piers of their 
 bridges, by means of coffer-dams, they still kept the 
 dam empty for two months, in order to allow the 
 masonry time to acquire some degree of consistency. 
 " Relinquatur pila," says Yitruvius, " ne minus quam 
 duos menses, ut siccescat." 
 
 275. They did not trust the success of any works, ex- 
 cept such as did not require great strength, to pounded 
 brick used in the way of pouzzolana. In general, all 
 their mortars which are exposed to the air are alike ; 
 we recognise them by the presence of coarse sand 
 mixed with gravel ; the lumps of lime in it are some- 
 times so multiplied, that it is impossible to attribute 
 them to defective manipulation. The extinction by 
 immersion, as applied to a very rich lime, can alone 
 account for it. 
 
 276. The Roman hydraulic mortars are very re- 
 markable, and differ from ours essentially : they are 
 composed, with few exceptions, of pure lime mixed in 
 large proportion with the fragments of bricks coarsely 
 pounded ; thus they resemble a breccia of which lime 
 is the matrix. Nevertheless, as the hrick could not 
 be broken up without leaving a small quantity of ra- 
 ther fine powder, it follows that the lime in such an 
 aggregate is never white ; it is on the contrary tinged 
 slightly red or yellow, according to the colour of the 
 brick made use of. 
 
 277« This mortar was usually intended to prevent 
 the infiltration of water ; they formed the bottom 
 and side lining of cisterns, fish-ponds, aqueducts, 
 &c. They beat it forcibly and for a long time, and 
 
180 ANTIQUE AND MODERN [CHAP. 
 
 after having smoothed the surface of it with a sand- 
 stone, they sometimes laid over it a plaster, or red 
 paint, whose composition is unknown. After the 
 above explanation, it is evident that the Romans cm- 
 ployed lime in paste in the way of lining, and that the 
 spongy dry substances which they introduced into it, 
 were for no other object but to hasten the solidifica- 
 tion, by exhausting its superabundant water. We 
 can understand, that owing to the size of these bodies, 
 the absorption could only take place slowly, and after 
 application of the mixture, a circumstance which faci- 
 litated its being compressed while in its place, to 
 make up for the shrinking of the lime. Besides, the 
 bits of bricks being insulated, and surrounded by the 
 matrix, did not injure its continuity, as the same 
 brick would have done had it been comminuted into 
 fine powder. Thus the desiccation of the plaster 
 took place, and the compactness and impermeability 
 of its texture were maintained. 
 
 278. Everything therefore in the composition of this 
 cement had its use, and the general application made 
 of it, shows that it answered its object well, without 
 however offering a great resistance, if we may judge 
 from the numerous specimens which have come to our 
 hands. The lime in them is in fact hardly harder 
 than chalk. However, it is of this same cement that 
 the Italians of our day manufacture those caskets and 
 snuff-boxes which they sell to the curious ; but it is 
 remarked that they never make use of any but the 
 outward and superficial parts of the plasters, which 
 are usually incr listed by a deposit of carbonate of lime. 
 
XVI.] MORTARS COMPARED. 121 
 
 Now it is this deposit which, when perfectly polished, 
 supports the rest, and constitutes the beauty and 
 curiosity of the work. (App. LXXIII.) 
 
 279. There is a prejudice already pretty generally 
 spread throughout France, that is, that the Romans 
 possessed a secret for the fabrication of mortars. 
 Some suppose the secret to be lodged in the choice of 
 the materials, and others merely in the way of apply- 
 ing them to use. b The very evident consequence of 
 these two opinions is, that the Roman mortars ought 
 everywhere to be equally hard. Now there are six 
 to one in which this is not true, as may be seen in 
 Table, No. 15. It is besides certain, that the ingre- 
 dients, lime, sand, and brick, always apparent in these 
 mortars, are absolutely the same as those of the 
 country where the monuments exist ; and Vitruvius 
 has saved us the trouble of this observation by saying, 
 (lib. i. chap. 5,) "I do not decide what ought to 
 be the materials for walls, because we do not every- 
 where meet with such as are most desirable ; but we 
 must make use of such as we can find," &c. 
 
 280. Some have thought to give a triumphant an- 
 swer to this, by saying, that from the mere fact of 
 their having existed for eighteen centuries and more, 
 
 b Leoni Baptista Alberti speaks of the use of oil, which he 
 declares to have been much employed by the ancients. He says, 
 (book iii. chap. 16,) " The work will be more secure still, if between 
 the rubbish and the plaster you lay a row of plain tiles cemented 
 with mortar mixed up with oil :" and again, "The ancients made 
 their shell either of baked earth or of stone; and where men's feet 
 were not to tread, they made their tiles sometimes a foot and a half 
 every way, cemented with mortar mixed t(j) with oil." — Appeal to tht 
 Public, Liardet, 1778. 
 
122 ANTIQUE AND MODERN [CHAP. 
 
 the antique mortars must be much superior to the 
 modern ones, whose unfitness is shown by the deplor- 
 able condition of most of our buildings. In order that 
 this conclusion be just, we ought to compare grand 
 monuments with grand monuments, and the puny un- 
 substantial buildings, with buildings of the same kind. 
 We could then, even with advantage, put in opposition 
 to the antique mortars those of our old ramparts, and 
 generally those of the grand edifices of the middle 
 ages. (App. LXXIY.) As for the fragile walls of our 
 private houses, they would figure perfectly by the side of 
 those which Pliny speaks of when he says (lib. 36,) — 
 " Ruinarum urbis ea maxima causa, quod furto calcis 
 sine ferrumine suo csementa compomentur." 
 
 281. On taking a general survey of the different 
 categories of mixtures contained in our Tables, it 
 will be seen that the limits of absolute resistance of 
 mortars of lime and sand vary from 18 kil .53 to &'-.''■ 
 per centimetre square. Xow the resistances of build- 
 ing-stone, taking the basalt of Auvergne for the 
 last degree on the scale, and for the first, the lime- 
 stone which is not sufficiently hard to stand polish- 
 ing, are 77 kil .OO and i 20 kil . d (The soft stone made use 
 of at Paris gives hardly 10 kil . c ) By this comparison 
 we see, that we ought to be verv guarded against un- 
 derstanding, in a literal sense, what some authors say 
 of the possibility of compounding factitious stones as 
 hard as flints, by means of lime and sand. 
 
 c Reduced to English measures these give from 263.75 to 10.675 
 pounds Avoirdupois per square i)tch. — Tn. 
 
 d l,0961bs. to 284.711m. p. r »qa*re inch.— Tr. 
 e 1 12.3 tlbs. per square inch. — Tr. 
 
XVI.] MORTARS COMPARED. 1 23 
 
 282. In calculations into which the tenacity of mor- 
 tar enters as a datum, when we have neglected nothing 
 in regulating the proportions correctly, and the choice 
 of the mode of extinction, we may reckon, one may 
 say, — 
 
 In the case of the eminently hydraulic mortars, 
 
 on an absolutely resistance of 12.00 kilf 
 
 With common hydraulic mortars 10.00 
 
 With hydraulic mortars of medium quality . . 7.00 
 
 With rich limes 3.00 
 
 The bad mortars which our builders manu- ) 
 
 > 0.75 g 
 facture do not give more than J 
 
 These resistances refer to mixtures continually exposed 
 
 to the weather, and one year old. 
 
 283. The best cements and mortars, of the same age, 
 which have been immersed, or buried in a constantly 
 damp foundation, do not give more than 10 kil .00. h 
 
 f It resulted from some experiments made by Mr. White (Phil. 
 Mag. No. 64-), that Parker's and Mulgrave's cements, and pouzzo- 
 lana, are in respect to incompressibility equally useful, and that 
 brickwork constructed with them would bear on each superficial 
 foot, before the bricks would crack, about twenty-three tons ; that 
 fifty tons would totally crush such brickwork ; that Portland stone 
 of the best cpiality would not split with less than one hundred and 
 seventy-three tons and a half; and that a bedding or joint of pouzzo- 
 lana mortar was not destructible with that weight. — Tr. 
 
 k The following are the resistances in pounds Avoirdupois when 
 
 reduced to correspond with the English square inch. 
 
 Pounds. 
 The eminently hydraulic limes 1 70.8 
 
 Ordinary ditto 142.34- 
 
 Hydraulic limes of medium quality... 99.64 
 
 Rich limes 42.7 
 
 Bad mortars 10.67 Tr. 
 
 h 1 12.34-lbs. per square inch. — Tr. 
 
CHAPTER XVII. 
 
 ON THE THEORY OF CALCAREOUS MORTARS AND 
 CEMENTS. 
 
 28 1. The solidification of mortars has been at 
 all times the subject of controversy ; Yitruvius has 
 entered into the subject, and many celebrated che- 
 mists in our days have made it the object of their 
 meditations. It would be irksome, as well as useless, 
 to notice in this place all the whimsical and odd 
 theories which have been published upon this subject ; 
 there are some amongst them which it would suffice 
 to name to show their absurdity. We shall confine 
 ourselves in what follows to discussing, as briefly as 
 possible, the most remarkable and plausible hypo- 
 theses ; and we shall suppose that the reader is in 
 possession of the principal facts mentioned in the 
 course of this work. 
 
 285. The cause of the phenomena was first attri- 
 buted to the regeneration of the lime by the slow and 
 successive action of the carbonic acid of the atmos- 
 phere. This opinion, supported by Black, Higgins, 
 Achard, and many others, held sway for a long time. 
 But Darcet, in analyzing some mortars procured on 
 the demolition of the Bastile, found in them only one- 
 half of the acid necessary for the saturation of the 
 lime ; and very recently, M. John, of Berlin, has dis- 
 covered that some very ancient and hard mortars were 
 
ON THE THEORY, ETC. 125 
 
 far from containing that proportion. After these 
 facts, and our own remarks upon the difficulty which 
 the carbonic acid meets with in penetrating into the 
 depths of masonry, the received explanation could be 
 no longer maintained. 1 
 
 28f>. The experiments of Guyton Morvcau, on the 
 mutual re-actions, in the humid way, of lime-water 
 and the solutions of silica and alumina, in potash or 
 soda, have caused it to be presumed with some proba- 
 bility, that chemical affinity may take a part in good 
 mortars, and that a portion of the alumina and silica 
 of the sand being acted upon by the lime, enters into 
 combination with it. This opinion, which we adopted 
 in our early researches, was also that of Mr. John ; 
 but that able chemist was not long in discovering its 
 insufficiency, by assuring himself by direct experi- 
 ments, that caustic, and even boiling lime, has no 
 action upon quartz. Soon afterwards, upon some 
 objections by Mr. Bcrthier, we became convinced on 
 own part, by disaggregating some mortars eighteen 
 
 1 There can be no doubt, nevertheless, that common mortars 
 ■which do not set, are very much improved in hardness by re-union 
 with carbonic acid, a fact which is easily proved by comparing the 
 resistance of the interior of a large mass of mortar, of chalk lime, a 
 twelvemonth old, with that of its superficial crust ; the former will 
 be found in a crumbling tender state, while the particles constituting 
 the envelope are firmly knit together and compact in texture. In 
 mortars, however, which set, the induration appears to be due to 
 other causes, and they ought, therefore, to be classed in a category 
 distinct from the simple mixtures of the hydrate of lime and inert 
 materials, and their phenomena studied independently, lest the 
 facts which they exhibit should interfere with our attempts at 
 generalization, by their apparent contradiction to truths already 
 established. — Tu. 
 
i'J.'i ON THE THEORY OF [dlAP. 
 
 months old by muriatic acid, (the sand of which had 
 been very exactly weighed,) that hydraulic lime is 
 equally without action on the granitic sands. 
 
 287. In this state of things the most precise notions 
 we as vet have, of the induration of the mixtures, 
 mortars, are confined to the knowledge that there 
 is neither any combination between the lime and 
 the sand, nor any integral transformation of this 
 lime into its carbonate, by a principle derived from 
 without. 
 
 288. It remains, therefore, for us to inquire into 
 the possible influence of a mechanical agency of the 
 particles, either considered as the result of a mere 
 interlacement, or as the proper cohesion of the lime, 
 in comparison with its adherence to the quartzose, or 
 calcareous substances embodied by it. 
 
 289. The hypothesis of a mere interlacement will 
 not bear examination, since any two bodies whatever 
 when joined by tenons and mortices, and without glue, 
 always separate by an even section, at the very joint, 
 and nowhere else, when they arc subjected to a trac- 
 tive force directed in any way in reference to the joint; 
 whence it follows, that no mortar can be superior in 
 resistance to its matrix. 
 
 290. Macquer seems to be the first who endeavoured 
 to explain the resistance of mortar by the adherence of 
 the lime, as compared with its own proper cohesion. 
 " The minute fineness of this substance," says he, 
 "and its extreme division, which reduces it altogether 
 to surfaces, gives it the faculty of applying itself most 
 intimatelv upon the surface of the sand, and of adher- 
 ing to it with a force proportioned to the nicety and 
 
XVII.] MOUTAUS AND CEMENTS. 127 
 
 closeness of the contact." This able chemist, else- 
 where accounts for the superiority of the aggregate 
 over its matrix, by the property which the particles of 
 slaked lime possess, of adhering to hard bodies more 
 exactly than to one another, or, in other terms, by the 
 superiority of its adherence over its cohesion. This 
 system has been developed very recently, though not 
 published, by Mr. Girard, Engineer of Roads and 
 Bridges. k 
 
 k It is surprising that in the construction of a theory based upon 
 these properties of adherence and cohesion, no pains should have 
 been taken to throw any light upon the nature of the properties 
 themselves. With the causes of either the one or the other we 
 are at present quite unacquainted ; for though the study of the 
 facts connected with their developement in certain circumstances 
 may sometimes afford a clew to the explanation of individual cases, 
 much must be added to our present knowledge of the subject, to 
 elucidate satisfactorily even the simplest phenomena. From some 
 experiments which I made with a view to investigate the cause of 
 the simple cohesion of pastes (which were not capable of absorbing 
 the fluid forming them), and their hardening when dry, I found 
 that the hydrates of lime and alumina, fresh precipitated oxalate 
 and phosphate of lime (containing water), silica when gelatinous, 
 the hydrated oxides, starch, gums, &c, all possessed considerable 
 tenacity when powdered and kneaded with water ; whilst the an- 
 hydrous substances, on the contrary, such as sulphur, carbon, 
 silica, and phosphate of lime freed from water, carbonate of lime, 
 and sulphate of lead, were very feebly coherent. In hardening on 
 desiccation, an evident superiority was exhibited by those sub- 
 stances which possessed the greatest affinity for the fluid ; while, on 
 the other hand, substances capable of acquiring considerable hard- 
 ness with one fluid, were altogether void of it with another. Thus 
 a paste of slaked lime made with water, when dried slowly acquired 
 a certain cohesion, but a similar paste of slaked (rich) lime with 
 alcohol fell to powder. The same substance kneaded with a solu- 
 tion of sugar, for which it has a great attraction, acquired a remark- 
 
1 28 ON THE THEORY OF [CHAP. 
 
 291. Loriot and Lafayc viewed nothing but the 
 interlacement in the aggregation of mortars ; hence 
 all their pains were directed towards the physical per- 
 fection of the matrix, to which they strove to give 
 great compactness ; whether by the adoption of pro- 
 cesses of extinction, which, by partially dividing the 
 substance, caused it to take but a small quantity of 
 water, or by introducing quick-lime in powder after 
 it was made up ; experience has not completely justi- 
 fied these attempts. 
 
 292. Before going farther, and to avoid complicat- 
 ing this discussion too much, we shall proceed to define 
 adherence such as we should understand it, and to 
 examine Macquer's hypothesis in all its bearings. 
 
 293. Adherence is the result of internal and un- 
 known forces which only act in contact ; it therefore 
 increases with the polish of surface, when we apply 
 hard bodies to hard bodies, and with the roughness 
 of surface, when we apply a soft or fluid body to a 
 hard one. But the asperities of a surface, although 
 they may increase the number of contacts, can add 
 nothing to the strength of an aggregate, if the cohe- 
 sion of its ganguc be much less than its adherence ; 
 for the rupture or separation will constantly take place 
 in the ganguc, and all the excess of adherence beyond 
 the limit which marks the inequality referred to, will 
 evidently be superfluous. 
 
 294. The first consequence deducible from this 
 observation is, that the size of grain being the same, 
 
 able consistency, hut with spirits of terpentine, lor which rt has none, 
 ii attained hardly any at all. — Tit. 
 
XVII.] MORTARS AND CEMENTS. L29 
 
 the more or less perfect polish of the grains, in sand 
 of the same nature, ought not to influence the resist- 
 ance of mortars of hydraulic limes. 
 
 295. Aggregates present four extremely remark- 
 able cases : — 1st. The matrix possesses the faculty of 
 hardening without perceptible shrinkage, and its ad- 
 herence is much stronger than its cohesion ; let us 
 call this G'. 
 
 2nd. The matrix can not harden without shrinking, 
 and its adherence is much stronger than its cohesion ; 
 let us call this G". 
 
 3rd. The matrix is capable of hardening without 
 perceptibly shrinking, but its adherence is much less 
 than its cohesion ; let us call this G'". 
 
 lth. The matrix will not harden without shrinking, 
 and its cohesion is much stronger than its adherence ; 
 let us call this G"". 
 
 Probable Theoretical Consequences of the First Case. 
 
 296. 1st. The matrix G' must, it seems, always ex- 
 hibit a less absolute resistance than that of its aggre- 
 gates, because its rupture always takes place freely in 
 the direction of a plane surface of least resistance, 
 while the aggregate can only be fractured along an 
 irregular jagged surface of larger developement. 
 
 297« 2nd. Proportions being the same, the strength 
 of the aggregates ought to be independent of the size 
 of the sand, if the grains are likewise somewhat similar, 
 because the section of fracture will in every case keep 
 the same developement, and since the notches, whether 
 consisting of plane or curved faces, will expose the same 
 number of elements, and under the same inclination. 
 
 K 
 
130 ON THE THEORY OF [CHAP. 
 
 298. 3rd. In every possible case, an inequality in 
 the proportions of sand should carry with it that of 
 the resistances, inasmuch as the developement of the 
 section of fracture is dependent upon this inequality. 
 
 299- 4th. The nature of the sand ought to be per- 
 fectly indifferent, ccrteris paribus, when their proper 
 cohesion surpasses that of the gangue. 
 
 300. The hydraulic and eminently hydraulic limes 
 afford the only gangues that we can with entire cer- 
 tainty assimilate to G'. Hence the mortars which 
 result from the use of these limes, ought to satisfy the 
 four consequences above established. Now experi- 
 ence shows, that the second and fourth are constantly 
 and completely invalidated, and that the third is so, 
 in the case of mortars buried underground. 
 
 301. We see, moreover, that we can gain nothing 
 by modifying the foregoing consequences ; for if, for 
 instance, we reverse the two first, we shall place our- 
 selves in continual opposition to the third and fourth, 
 which are indisputable. It is in fact, because matter 
 cannot lend itself to the mathematical conceptions 
 from which the first three consequences are derived ; 
 for in reality, the asperities and incidental irregulari- 
 ties of surface of rupture of a solid mass of the hydrate 
 of hydraulic lime, are very nearly of the same order as 
 those which we observe on the fracture of mortars of 
 sand of the ordinary size. Thus the mathematical 
 distinctions drawn between the developcments of these 
 fractures are, physically speaking, null, and conse- 
 quently in no relation to the enormous differences 
 which experience points out between the effectiye 
 resistance of mortars and that of their gangue-. 
 
XVII.] MORTARS AND CEMENTS. 1.31 
 
 Probable Theoretical Consequences of the Second 
 Case. 
 
 302. 1st. The gangue G" ought to form aggre- 
 gates of less resistance than itself: for the sand beino- 
 
 o 
 
 unable to follow the general movement of such a 
 gangue in shrinking, this movement is obliged to be 
 subdivided, so to speak, into an infinite number of 
 partial contractions, whence arises pulverulence. 
 
 303. This consideration perfectly accounts for the 
 bad qualities of mortars of rich lime slaked with much 
 water by the ordinary process, and there is no need to 
 search for any other cause. 
 
 Probable Theoretical Consequences of the Third 
 
 Case. 
 
 304. 1st. The matrix G" must necessarilv oive 
 birth to aggregates of less resistance than itself, be- 
 cause the interposed grains, from their want of adhe- 
 rence, interrupt the continuity of strength throughout 
 the mass. 
 
 305. This consequence is completely justified in the 
 instance of the bastard mortar, or mixture of plaster 
 and sand; as it would also be in the instance of the 
 mortars of rich limes, called Loriot s and Lafaye's, if 
 it were proved that in these mortars the cohesion of 
 the gangue surpassed its adherence. Now this is a 
 circumstance at least doubtful. 
 
 Probable Theoretical Consequences of the Fourth 
 
 Case. 
 
 306. 1st. The gangue G" must produce the worst 
 
 k 2 
 
132 ON T THE THEORY OF [CHAP. 
 
 of all the aggregates, and this evident conclusion is 
 justified by the instance of the mixtures of clay with 
 sand of all sizes. 
 
 307. Thus the mortars of hydraulic, and eminently 
 hydraulic limes, are the only ones which cannot he 
 explained by the theory of aggregates. We are 
 therefore compelled to have recourse to other consi- 
 derations ; and most of the difficulties will at once 
 disappear, if we consent to admit, 1st, that the action 
 of adherence is not confined to a superficial effect or 
 to contact, but that to a certain extent it augments 
 the cohesion peculiar to the matrix ; 2nd, that the 
 limits of this extent are the more enlarged, the more 
 favourable are the circumstances in which the mixture 
 is placed, to a continuance of the molecular movement 
 which takes place in the gangue ; 3rd, that lastly, 
 the increase of cohesion in this matrix is inversely 
 proportional to the distance of its particles from the 
 aggregated body which acts the part of the nucleus. 1 
 
 1 That some cases of the solidification of hydraulic mortars are to 
 be explained upon the principle here laid down cannot be denied, 
 as this volume contains many facts in support of it, (vide Arts. 309 
 and 314-, with the notes, especially the latter,) which render it im- 
 possible to exclude chemical agency from an important place amongst 
 the causes of the hardening of mortars. Neither, on the other hand, 
 can it be denied, that many instances may be adduced, in which 
 the chemical affinity of the component parts is insufficient to afford 
 a satisfactory explanation of the phenomena, and the energy of such 
 cements must therefore be attributed to some other cause. Thus, 
 the setting of Plaster of Paris, and calcined magnesia in powder, in 
 which there is no chemical re-action between the solid particles, 
 seems to be more probably due to the solidification of the intersti- 
 tial fluid (by which they are kneaded into a paste), by its combina- 
 tion with the solid substance of the paste ; which combination I 
 
XVII.] MORTARS AND CEMENTS. 133 
 
 308. We shall proceed to support this hypothesis 
 by facts and considerations of great weight. When we 
 examine most of the calcareous incrustations attached 
 to the sides of caverns, and above all ancient aque-' 
 ducts, we remark that the density of the layers de- 
 creases in proportion as they recede from the part in- 
 crusted. This fact is, so to speak, inscribed on many 
 specimens taken from the bed of the aqueduct of Gard, 
 specimens which we have before our eyes. Molecular 
 and successive motion within solid bodies is attested 
 by a multitude of observations." 1 Mr. Arago has 
 given us some unanswerable instances of it in the 
 change of elasticity of steel springs. Why refuse to 
 admit it in gangues which appear possessed of great 
 powers of crystallization, such as the hydrate of hy- 
 draulic lime ? Is it contrary to the principles of 
 science to suppose, that the film of lime which attaches 
 itself in adhesion to the face of a hard body, becomes 
 itself a hard substance in respect to the film next to 
 it, and that one after another these films may finally 
 adhere one to another by an attraction superadded to 
 the cohesion natural to them ? Doubtless no ; such 
 an action may even be kept up for a very long con- 
 tinuance, especially when the moist condition of the 
 matrix favours it, 
 
 have ascertained to have actually taken place in these cases. The 
 same may perhaps be a correct explanation of the first set of 
 Parker's and other cements, of the concrete now so well known, and 
 of some of the hydraulic limes (vide note to App. L.), though there 
 are no doubt many of these which combine both causes of solidifi- 
 cation. (Vide App. LXXV.)— Tk. 
 
 m The crystallization of the metallic mirrors used in Telescopes, 
 induced, after solidification, by certain processes, is a remarkable 
 example of this. — Vide London Encyclopedia., art. Speculum. — Tft, 
 
13 1 ON THE THEORY OF [CHAP. 
 
 309- The very remarkable experiments of Mr. 
 Petot, Engineer of Roads, on the relations which 
 exist between the solubilities of hydraulic lime joined 
 with sand, and the proportions of the mixtures, leave 
 no doubt of the influence exerted by the presence of 
 the quartz upon the cohesion of the lime. n The 
 conclusions to which that observation leads, are ne- 
 cessarily analogous to those which have been given 
 above. 
 
 310. We shall leave it to the reader's care to apply 
 these principles to the various cases of resistance 
 offered by mortars of hydraulic lime ; and in respect 
 to mortars of rich lime slaked by immersion, or spon- 
 taneously, we shall confine ourselves to remarking, 
 that in lieu of endeavouring to account for their 
 inferiority by the purely gratuitous hypothesis of the 
 
 n This observation seems to be confirmed by the result of some 
 of my own experiments, although they were undertaken with quite 
 a different view. In endeavouring to account for the absence of 
 carbonic acid in mortars of great age (note to App. XXYIII.), and in 
 searching for the neutralizing power which had supplied its place 
 in part, in deprhing the lime of its caustic quality, I wa< naturally 
 led to inquire into the influence which the presence of the other 
 ingredients of the mortars might exercise over the exhibition of 
 the phenomenon, in the hopes of tracing it to its true cause. In 
 some of the cements water was found to be a component principle, 
 but this was not always the case, others being met with in which 
 the analyses were complete, although there was little or no water. 
 The only remaining ingredient therefore to which the effect could be 
 referred WW the silica ; and although, in respect to it, I was unable 
 to obtain any direct proofs on which to found the assertion, that 
 silica exercises a neutralizing power with lime in the humid way. 
 yet its affinity for it and the alkalies is so Btroagly shown by many 
 well-known far-, n ially in it- action in hydraulic Cements, 
 
 an '1 there are so nianv indirect circum-taii'-i - connected with its 
 
XVII.] MOllTAUS AND CEMENTS. 135 
 
 superiority of the cohesion over the adherence of the 
 matrix, it is much better to believe with Mr. Petot, 
 that being deprived of all power of crystallization, the 
 matrix has no occasion for the presence of the sand in 
 aid of its own proper cohesion. 
 
 311. Calcareous cements, as we have already re- 
 marked, cannot be assimilated to aggregates ; their 
 solidification presents phenomena of another order, 
 which have only been viewed in their proper light 
 within the last few years. Rich lime, when lodged 
 amongst the grains of quartz of an ordinary mortar, 
 retains in it its characteristic properties, which are, 
 to be soluble to the last particle in water, and to 
 remain soft for a great number of years when ex- 
 cluded from the contact of the air. When mixed 
 however in certain proportions with an energetic 
 
 influence upon these bodies which tend to strengthen the above 
 opinion, that I cannot avoid looking upon the subject as one well 
 worthy of investigation, under which impression I venture to 
 subjoin the following remarks : — In revising the simplest cases of 
 the phenomenon, the facts are as follows, — 1st, That a certain 
 weight of lime which is associated with silica and carbonic acid, 
 is found to be perfectly neutral to the action of tests, though 
 there is only sufficient carbonic acid present to combine with part 
 of it. — 2nd, That silica has a strong affinity for lime in circum- 
 stances which may frequently occur in cements; these are, when 
 it is in a minute state of division, especially if gelatinous ; a fact 
 which is shown by its communicating to it the property of har- 
 dening under water, (App. XXXVII.) under circumstances in 
 which the iuduration cannot be occasioned by absorption of the 
 fluid, as in the setting of Plaster of Paris and some other cements 
 (note to Art. 307). — 3rd, It is remarkable, that many very old 
 mortals, and particularly those which considering their age pre- 
 sent a striking deficiency in carbonic acid, are very difficult of 
 solution in the cold, even in strong acid, some even requiring days 
 
136 ON THE THEORY OF [CH.U\ 
 
 pouzzolana in a pulverulent state, the lime disappears 
 in a way, becomes insoluble, and communicates to the 
 compound the faculty of hardening in a short time, 
 either in water, or in enclosures impermeable to 
 the air. Now, in what way does this lime thus 
 change its nature? The ancients appear to have 
 attributed a part of these phenomena to the faculty of 
 pouzzolanas to absorb a large quantity of water ; but 
 it is evident that that effect is null when the absorp- 
 tion of the pouzzolana is complete. Now mix a rich 
 lime in paste with a pouzzolana soaked to saturation, 
 and immerse the mixture ; it will harden none the 
 less after a few days. 
 
 312. On attentively reading over Mr. John's ob- 
 servations upon the efficacy of pouzzolanas, which he 
 compares neither more nor less to every kind of sand, 
 
 before yielding, and parts being occasionally quite insoluble except 
 at an elevated temperature. — 4th, What has contributed still more 
 to turn my attention towards the possibility of a neutralizing agency 
 in the silica, is the remarkable fact exhibited by a comparison of 
 mortars of the same age, and of similar compositions of lime and 
 sand, but of different proportions, and which show a manifest rela- 
 tion between the quantity of silica, and the quantity of carbonic 
 acid, the latter being always in the smallest proportion, when the 
 former was in excess, and vice versa. I have extracted from my 
 notes the following analyses in illustration of this, and they are the 
 only ones strictly comparable with reference to the point in ques- 
 tion, as in them the cements which are ranked in the same series and 
 opposed to one another, are all taken from the same part of the same 
 building, and are consequently of the same age, and have been sub- 
 jeeted to the same exposure. I should also mention in referring to 
 them, that the analyses were all completed without reference to 
 the point now under examination ; as it was not till long afterwards 
 that a comparison of the results kd me to observe the relation I have 
 stated. 
 
XVII.] 
 
 MOinWUS AND CEMENTS. 
 
 137 
 
 and more especially this singular assertion, " That if 
 the pulp of lime cannot harden of itself, and without 
 any addition, neither will it be able to do so a bit the 
 better by any admixtures," we saw at once that that 
 scientific chemist had not studied water-cements, and 
 thus that on this head his authority could be of no 
 service. 
 
 313. Mr. Berthier, Engineer in Chief of Mines, who 
 was perfectly sensible of the strangeness of Mr. John's 
 
 Table extracted from the analyses of various cements (Table 17), 
 showing the relative proportions of lime, sand, and carbonic acid 
 contained by them : — 
 
 Series. 
 
 No. of 
 Analyses 
 
 in 
 Table 17. 
 
 Age. 
 Years. 
 
 Lime 
 
 Sand. 
 
 Proportion per cent, borne by 
 the carbonic acid contained 
 in the cement, to the full sa- 
 turating dose. 
 
 1st. 
 Mortar of 
 Rich Lime. 
 
 1 
 
 2 
 3 
 
 120 
 do. 
 do. 
 
 1 
 1 
 1 
 
 1.9 
 2.1 
 5.9 
 
 92.0 
 93.8 
 83.3 
 
 2nd. 
 
 Mortar 
 
 of 
 
 Rich Lime. 
 
 4 
 5 
 
 6 
 
 7 
 8 
 
 200 
 do. 
 do. 
 do. 
 do. 
 
 1 
 1 
 1 
 
 1 
 
 1 
 
 1.6 
 
 1.7 
 1.8 
 1.9 
 3.3 
 
 93.4 
 93.2 
 91.2 
 91.05 
 
 77.4 
 
 3rd. 
 Mortar of 
 Rich Lime. 
 
 9 
 10 
 
 150 
 
 do. 
 
 1 
 
 1 
 
 1.83 
 2.93 
 
 79.0 
 76.9 
 
 4th. 
 Mortar of 
 Magnesian 
 Lime, con- 
 sisting of 2 
 Lime to 1 
 Magnesia. 
 
 11 
 12 
 
 400 
 do. 
 
 1 
 
 1 
 
 2.2 
 3.7 
 
 The carbonic acid 
 
 I in these two cases 
 
 o*7 ry amounts merely to 
 
 J the per centage nam- 
 
 ( ed of the saturating 
 
 «ro *7| dose for the lime 
 
 ' -• ' Ic/i/v, leaving the mag - 
 
 | nesia entirely desti- 
 
 1 tute of it. 
 
 The quantities of sand in the above Table have been reduced to 
 the unit of lime to render comparison more easy ; by which means 
 
1'38 OM THE THEORY 01 [CHAP. 
 
 opinion, has endeavoured to explain the solidification 
 of hydraulic cements, by the intervention of carbonic 
 acid, held in condensation in the same way as other 
 gases, in the pores of pouzzolanas and analogous sub- 
 stances : but analysis does not confirm this supposi- 
 tion ; on the contrary, it proves that there is very 
 little carbonic acid in the greater part of water- 
 cements. For instance, Mr. John found only £.25 
 of acid to 32.76 of lime contained in 100 part* of 
 tanas cements. Besides, how could we explain the 
 deterioration which, with certain water-cements, fol- 
 lows a solidification already far gone ? By virtue of 
 what affinity does the lime, when once carbonized, get 
 rid of its acid in order to regain its solubility ? 
 
 311. "We persist in thinking, as we have always 
 maintained till now, that the lime in cements of natural 
 or artificial pouzzolanas, as well as in cements formed 
 with the uncalcined psammitcs and arenes, enters into 
 chemical combination with these substances. Our 
 
 the remarkable correspondence between the proportions of silica 
 and carbonic acid are rendered obvious. Indeed, the surprising 
 accordance to the supposed relation, which is exhibited by the first 
 four numbers of the second series, is I have no doubt accidental, as 
 the experiments were not made with the scrupulous exactness neces- 
 sary to entitle them to confidence in such minute particulars ; but I 
 cannot attribute to that cause the close correspondence to it exhi- 
 bited by the sudden change in the proportion of both substances 
 in the fifth analysis of that series. — Tr. 
 
 A remarkable confirmation of this opinion was exhibited by 
 the result of some experiments on artificial pouzzolanas made by 
 myself. From these it appeared, that no absorption of fluid what- 
 < -vi r took place dmfog the set of a cement composed of one part 
 of well-tempered rich lime to two of an excellent artificial pouz- 
 zolana. I al<o found that this powder, which when used fresh 
 
XVII.] .MORTARS AND CEMENTS. 13<) 
 
 opinion harmonizes with numerous facts set forth 
 in the course of this work ; these facts, it is true, 
 cannot be looked upon as direct proofs, but we 
 know, that in matters of this kind direct proofs are 
 extremely difficult, and sometimes impossible to ob- 
 tain ; we know, moreover, that geometricians consider 
 two straight lines to be equal, when they have proved 
 that one can neither be smaller nor larger than the 
 other. (App. LXXVII.) 
 
 ■with half its weight of lime set firmly in six hours, was not percep- 
 tibly impaired in energy by an immersion in water of a month 
 and eight days ; but a similar artificial pouzzolana, immersed after 
 being combined with lime, and formed into cement, was very 
 nearly deprived of its virtues in little more than the same period, 
 when tried by being a second time reduced to the finest powder, 
 kneaded into a stiff paste, and put under water. (App. LXXVI.) 
 The same opinion is entertained by General Treussart ; for he says 
 (p. 143), " In accounting for the solidification of mortars under 
 water, it seems to me that we ought to divide them into two 
 classes, altogether distinct ; those which are composed of hydraulic 
 lime and sand, and those composed of rich lime and pouzzolana." 
 And again, (p. 144,) "As to mortars of rich lime and pouzzolana, 
 I do not see how we can explain their solidification under Avater, 
 without admitting a combination between the lime and the pouz- 
 zolana." And I have been led to the same conclusion myself, 
 though adopting a different explanation of the hardening of hydrau- 
 lic limes from that of the author just quoted. (Vide note to Art. 307, 
 and App. LX.) — Tr. 
 
APPENDIX. 
 
 NOTES ON CHAPTER FIRST. 
 
 (I.) We find the history of lime in all the systems of 
 chemistry ; considered as an elementary substance till 1807, 
 it now belongs to the category of metallic oxides, under the 
 name of the oxide of calcium. When associated with car- 
 bonic acid in the proportion of 127.4 to 100, it constitutes 
 the carbonate of lime of mineralogists ; it is a substance the 
 most widely diffused in nature, and without doubt the most 
 varied in its form, texture, appearance, and association. 
 Carbonate of lime, in fact, belongs to every formation and 
 every epoch of the globe ; it is associated with the primitive 
 rocks, forms a part in the transition regions, and composes a 
 large portion of the secondary and tertiary formations. The 
 coral worms create this substance in a perfect state, and erect 
 immense reefs of it; the molluscous animals cover themselves 
 with it ; and lastly, all the classes of inferior beings produce 
 and apply it to use daily. 
 
 The oldest lime-stone is found in the primitive formations : 
 it is usually very crystalline and large grained, mostly of a 
 white or grey colour ; when in large masses, or in beds alternat- 
 ing with gneiss a and the schists, its crystalline appearance 
 seems to diminish, in proportion as it rises to the highest 
 limit of these formations. 
 
 The primitive stratifiedlime-stone frequently contains foreign 
 minerals included in it, such as quartz and mica. This 
 latter substance gives it a schistose aspect, and it then makes 
 it a real calcareo-micaceous schist. 
 
 a " A compound rock, consisting of felspar, quartz, and mica, disposed 
 'n slates, from the predominance of the mica scales. Its structure is 
 called by Werner, granular-slaty. Tin's geognostic formation is always 
 stratified;" &c. — L're's Chemical Dictionary. 
 

 1 18 APPENDIX. 
 
 The limestone of the intermediate or transition forma- 
 tions, is essentially distinguished from the preceding, by its 
 position. It may otherwise exhibit the same mineralogical 
 characters. We should remark, however, that although 
 crystalline, it is very small grained, and that we seldom 
 meet with any great extent of it that is decidedly of a 
 granular texture ; that its fracture is most frequently tabular, 
 and tends to approach the compact ; that it generally belongs 
 only to the secondary formations ; and lastly, that its colours 
 are in general lively, intense, and agreeably mixed. 
 
 In the secondary formations, of which lime-stone constitutes 
 the greater bulk, geologists in France remark two stages 
 or formations : 1st, the Alpine, 2d, that of the Jura. These 
 formations are sometimes separated by beds of sand-stone, 
 gypsum, marl, clay, and rock salt, in conformable beds. 
 
 The deep grey Alpine lime-stone, after passing to a black 
 or blueish grey, exhibits a compact tabular fracture, some- 
 times granular, which admits of its being made use of as mar- 
 ble. The Jura lime-stone which is of a clear grey or yel- 
 lowish white colour, with a compact and smooth conchoidal 
 fracture, \ery often takes an oolitic structure. 
 
 It is principally in the secondary formations that we meet 
 the argillaceous lime-stone calculated to furnish hydraulic 
 limes. We often find it in beds underlying the Alpine lime- 
 stone, and between this ast and the Jura limc-stonc, which 
 is itself frequently alloyed with clay b . 
 
 b An abundant supply of hydraulic lime-stone is distributed through 
 England by the lias-beds, which the geological maps represent traversing 
 the island from north to south, commencing at Whitby, on the Yorkshire 
 coa>t, passing through that county, and the west of Lincolnshire, border- 
 ing Nottinghamshire, thence following for some distance the east bank of 
 the Trent, afterwards crossing Warwickshire and Gloucestershire, and 
 malting its appearance in various parts of Somersetshire, finally termi- 
 nating near the junction of the counties of Devon and Dorset, in the 
 neighbourhood of Lyme. " This formation consists of thick argillaceous 
 deposits, constituting the base on which the whole oolitic series reposes. 
 The upper portion of these deposits, including about two thirds of their 
 total depth, consists of beds of a deep blue marl, containing only a few 
 irregular and mbbly lime-stone beds. In the lower portion, the lime-stone 
 
APPENDIX. 113 
 
 'Die shelly formations and the marls of the tertiary strata 
 are also very often argillaceous, and help to swell the calcgory 
 of hydraulic lime-stones. (Vide the systems of geology.) 
 
 (II.) The following is a method of analysis proposed by 
 M . Berthier, for persons who have some acquaintance with che- 
 mistry, as well adapted to distinguish hydraulic lime-stone. 
 
 " We pound the mineral, and pass the powder through a 
 hair sieve ; 10 grammes (15-1.4 grs.) of this powder are put 
 into a capsule, and we pour upon it, little by little, muriatic 
 acid, (in case we have no muriatic, we may use nitric acid 
 or vinegar,) diluted with a small portion of water, stirring 
 it continually with a glass rod or strip of wood ; we dis- 
 continue adding the acid as soon as the effervescence ceases. 
 We then evaporate the solution by a gentle heat, until the 
 whole be brought to a pasty condition ; the pasty mass is now 
 
 beds increase in frequency, and assume the peculiar aspect which charac- 
 terise* the lias, presenting a series of thin stony beds separated by 
 narrow argillaceous partings ; so that quarries of this rock at a distance 
 assume a striped and riband-like appearance; in the lower beds of this 
 lime-stone, the argillaceous partings often become very slight and almost 
 disappear, as may be seen in the lias tract of South Wales : beds of blue 
 marl with irregular calcareous masses, generally separate these strata 
 from the red marl belonging to the subjacent new red sand-stone form- 
 ation. The lime-stone beds, towards their centre, where most free from 
 external mixture, contain more than 90 per cent of carbonate of lime ; the 
 residuum has never been distinctly analysed, but appears to con- 
 sist of alumine and iron, and in some varieties traces of silex have been 
 found : towards the edges of the beds, however, where they come in con- 
 tact with the alternating strata of clay, the proportion of alumine is, as" 
 might be expected, more considerable. This lime-stone is particularly 
 characterised by its dull earthy aspect, and large conchoidal fracture ; in 
 colour it varies in different beds from light slate blue, or smoke grev, to 
 white : the former varieties usually constituting the upper ; the latter, 
 the lower portions of the formation. The blue lias, which contains much 
 iron, affords a strong lime, distinguished by its property of setting under 
 water." " The irregular beds consist of fibrous lime-stone and cement 
 stones (septaria) so called, because used in making Parker's cement." 
 Com/bcare and Phillips's Geology of England and Wales, 
 
 Towards the southern extremity of the lias formation above referred to, 
 the bed widens in extent, so as to include a small part of Glamorganshire, 
 whence the celebrated Aberthaw lime-stone is procured. But of late years 
 the valuable properties of this lime have acquired it a reputation at other 
 
 *B 2 
 
] I I VPPKNDIX. 
 
 diffused in about half a litre c of nraler, ami we filter ii. The 
 
 clay remains on the filter. This substance is now dried in the 
 sun, or before the fire, and weighed. Or what is still better, 
 it may be calcined to redness in an earthenware or metal 
 crucible, previous to weighing. Very clear lime-water is 
 poured into the solution, as long as it continues to form a 
 precipitate *. This precipitate, which is magnesia, is collected 
 as hastily as possible on a filter, it is washed in pun- water, 
 dried as perfectly a- possible, and lastly weighed." 
 
 The weight of the clay, as compared with that of the 
 calcareous mineral dissolved, gives an approximate indica- 
 tion of the place which it ought to occupy in the scale ■>! 
 hydraulic lime-stones. It is important to remark, that instead 
 of clay, there may very probably remain after the first filtra- 
 tion, nothing but a very fine sand, or perhaps a mixture of 
 very fine sand and clay. In the first case, the mineral under 
 examination is incapable of affording any thing but a " poor 
 lime." In the second, we must separate the sand and clay 
 by washing and decantation, and estimate the weight of each 
 independently. 
 
 The varieties in the quality of lime did not escape the ob- 
 servation of the ancient architects. Hence they took much 
 
 points of the line above traced, as for instance, at Barrow-on-Soar, in 
 Leicestershire, and Watchet, in Somersetshire, both of which will be 
 observed to be within the limit of the same formation. It a]>; 
 however, that the quality of the lime is not uniform throughout the 
 whole extent of it- range, being in sumo places slightly less energetic 
 than others, a circumstance no doubt to be attributed to variations in 
 the quality, or proportion, of the alloy contained by it. — 
 
 c A litre i- equal to about a quart English. — Tb. 
 
 d It would be better to ascertain by an independent experiment, (viz. 
 by dissolving a separate portion of the mineral in the acid, and adding an 
 excess of lime-water,) whether it contain magnesia or not ; because, 
 should there not be any. the lime may be precipitated by car bo nate of 
 potash, and its Quantity estimated, u a cheek t<> the accuracy of the 
 rest of the process. The weight of the precipitate obtained by the 
 carbonate of potash, (which is carbonate of lime, with perhaps a little 
 iron, &c.,) after being washed and dried, ought, with that of the silex 
 and alumina, to make up the whole amount of the mineral dissolved 
 for analysis.— 
 
APPENDIX. 145 
 
 trouble to discover relations between these qualities and the 
 external characters of the lime-stones. Their labours were 
 necessarily fruitless, since the chemical composition on which 
 their intimate qualities depend, cannot be exhibited by the 
 weight, hardness, fracture, colour, or. iii a word, by what 
 constitutes the physiognomy ot'a body. 
 
 The modern works which have taken up this question, 
 moreover, all repeat, in a pretty uniform manner, the rules 
 which Yitruvius has transmitted to us. The Roman ar- 
 chitect had, as he himself confesses, consulted the Greek 
 works which existed in his time ; so that all these doctrines 
 >eem to refer themselves to a common and very ancient 
 origin ; possibly they were perfectly suited to the materials 
 of the countries where the first observations were made. 
 
 (III.) The field of our early experiments was siugulavlv 
 enlarged by the researches on hydraulic limes which we under- 
 took in 1824, 1S25, and 18'2t>. by order of the Director General 
 of Roads and Bridges, on the lines of navigation from Xantes 
 to St. Bffalb, from Xautes to Brest, from Briare to Digoin, 
 from Decise to the course of the Yonne near Chatillon, and 
 in the environs of Besan^on. "NYe were enabled to examine 
 and to submit to uniform methods of comparison eighty-three 
 varieties of lime, both hydraulic as well as slightly and emi- 
 nently hydraulic. The details of this examination and of 
 the results which accompanied it, have been confirmed, as 
 regards the canals of Brittany, by M. Bouessel, inspector of 
 division ; Piou, Engineer-in-chief; Mequin, Leguay, and Coi- 
 quand, Engineers in ordinary, attached to the works of the 
 canal of Isle and Ranee ; and, for the canals of the Loire and 
 in Nivcrnais, by Messrs. Yigoi-eux and Tibord, Engineers in 
 chief, and Barraude, Engineer in ordinary, attached to the 
 service of the canal of the Loire. 
 
 (1Y.) A very small quantity of iron is sufficient to change 
 the ordinary whiteness of lime, and communicate to it the 
 yellow, red, or greenish-yellow tinge, which we frequently 
 see. It is therefore quite plain, that a lime may be coloured 
 without ceasing to be " rich," while at the same time there is 
 nothing t<> prevent a very white lime being powerfully hy- 
 
146 Ari'KNnix. 
 
 frantic", since it may owe this latter property entirely to the 
 pivsi -nee of a pure clay, that is to say, one wholly composed 
 of silica and alumina. 
 
 (V.) — *Thc following account of the process alluded to, is 
 extracted from the " Gleanings in Science," vol. i. p. -17. 
 
 " The method of analysis was rather different from that 
 usually employed. The lime-stone in powder, was exposed in 
 small covered cupels to the regulated heat of an assay fur- 
 nace. "When the first heating was not sufficient to expel all 
 the carbonic acid, they were again submitted to the fire ; and 
 to prove that all the gas had been driven off, a few of 
 the samples were further heated without loss of weight iu a 
 forge. 
 
 " A very ingenious method was adopted to prove the 
 correctness of this mode of analysis. The lime, rendered 
 caustic by the preceding operation, was converted into a 
 hydrate. The increase of weight was found to correspond 
 with the carbonic acid driven off f . 
 
 " The employment of this method of verification has 
 afforded a very valuable hint towards the solution of the very 
 difficult problem of separating lime from magnesia, or rather 
 
 • From experiments en various limes, Mr. Smeaton concluded, that 
 their goodness for hydraulic purposes could not he inferred from their 
 colour previous to burning, inasmuch as he found blue, whitish, and brown 
 of equally good quality, but they ad seemi d to agree in falling, after calci- 
 nation, into a powder of a buff-coloured tinge, and in containing a consi- 
 derable quantity of day. — Construction of the Eddystone Lighthouse. 
 
 1 Should the mineral consist of carbonate of lime only, then the quantit) 
 of carbonic add expelled will be gtha of its weight, the remaining fgths being 
 pure lime. This remainder gains an increase of jgths by slaking, which is 
 the weight of the water which unites with the lime by that process. Hence 
 the following rule for ascertaining the quantity of lime in a compound of 
 lime and magnesia, by the process of hydration. Multiply the increase 
 of weight after slaking by f (or by 3,',) which will give the amount of 
 pure lime, or by 5j for the quantity of carbonate of lime corresponding to 
 it which existed in the mineral previous to calcination. The remainder 
 will be carbonate of magnesia, unless there be other ingredient-, which 
 must be ascertained by a separate process. In carbonate of magnesia 
 Hdths or nearly 47 per cent, is magnesia, and the remaining 53 carbonic 
 acid Tr. 
 
A1TLNDIX. 147 
 
 of estimating their respective quantities. It appears that 
 magnesia does not form a hydrate e , so that the increase of 
 weight is an index to the quantity of lime in any magnesian 
 lime-stone." In recording some further experiments in pro- 
 secution of this subject, the author says, M the results were 
 in even- way coincident and satisfactory, and leave no doubt 
 in my mind, that the dry analysis of mixtures of lime and 
 magnesia is capable of much greater precision than the 
 humid analysis, in which according to Daubeny, five, and 
 even ten per cent, of difference will result from the use of 
 different precipitants. 
 
 " With care in the process of calcination, and the check 
 operation of slaking, I do not imagine that one per cent, of 
 error should find its way into the result. And the method is 
 applicable even when there is silex or any of the inalterable 
 earths united to the carbonates ; provided that the proportion 
 of these be first ascei'tained by solution in an acid." — Tb. 
 
 (VI.) — ^Extensive beds of the native carbonate of magnesia 
 have been recently discovered in the South of India, near Salem 
 and Trichinopoly, in the Madras Presidency, and the supply is 
 so abundant, that measures have already been taken for turning 
 this valuable material to account as a cement, for which pur- 
 pose the experiments of Colonel Pasley have shown it to be 
 admirably adapted. Some varieties of the mineral are so 
 
 s This is not correct, as magnesia does combine with water, and form a 
 hydrate, but not with sufficient rapidity to interfere with the correctness 
 of this method of analysis, if its completion be not unduly retarded. I 
 found by experiment, that a hundred grains of fresh calcined magnesia, 
 powdered while warm, and immersed in water, had in twenty hours 
 gained 18j grains in weight, and after three days and a half immersion bad 
 combined with very nearly the whole of their saturating dose of water, 
 (the weight being then 142. 9, and some allowance for loss beinsr neces- 
 sary, owing to its having been dried and weighed repeatedlv) and become 
 converted into a true hydrate of magnesia. It is remarkable also, that as 
 long as this reabsorption of water continues, the mass has a great ten- 
 dency to set and harden, and requires to be continually stirred to prevent 
 its doing so ; but as soon as the saturation is complete, the powder 
 becomes quite inert, and incapable of setting under water Tb. 
 
]48 APPENDIX. 
 
 haul, pre\ ious to calcination, as to strike fire with steel, 
 others are of a softer description. The constituents of a spe- 
 cimen analysed by my friend Dr. Malcolmson, of the Madras 
 medical service, to whose kindness I am indebted for the fol- 
 lowing particulars, are, in a hundred grains, magnesia 17], 
 carbonic acid 51^, water £, and silica £, the proportion of the 
 last ingredient varying in different samples within very nar- 
 row limits. Alter calcination, the magnesia does not slake 
 like lime, but when powdered and made into a paste, a sen- 
 sible heat is extricated ; it is capable of hardening nude) 
 water, though it is preferable to allow it to dry for twelve 
 hours or more previous to immersion. In time it acquires a 
 firm consistency, and even as a common stucco has been de- 
 scribed as of " extreme hardness." An admixture of not 
 more than one and a half times its bulk of clean sand is found 
 to improve its qualities for general purposes, at the same time 
 that it diminishes its cost, but the proportion of such alloy 
 must, of course, be regulated by the use for which the mixture 
 is intended. As a stucco it is considered the most beautiful 
 of all the cements, and that even at Madras, where the chu- 
 nam, so long celebrated, is made in the greatest perfection. 
 In fact, the only impediments to its exclusive adoption seem 
 to be the cost of transporting it from the situation in which 
 it is found, and the difficulty of preserving its properties, 
 after calcination, unimpaired, it being subject to deterioration 
 by the absorption of moisture from the atmosphere ; together 
 with the cost of pulverising it previous to use. With regard 
 to the use of magnesian lime-stone, I shall merely add to 
 what is stated on this subject in the note, that I have met 
 with very excellent common mortar of great hardness which, 
 iiom the proportions of lime and magnesia which it contained, 
 appeared to have been made from dolomite. And the follow- 
 ing quotation from Phillip's Mineralogy, p. 166, where in 
 speaking of inagnesian lime-stone, he says, " The lime ob- 
 tained from it is greatly esteemed foff cements, being less sub- 
 net to decay; owing to its absorbing less carbonic acid from 
 
Al'I'ENDIX. 149 
 
 the atmosphere than the lime of common lime-stone," seems to 
 correspond with the opinion I have been inclined to form of it. 
 I have recently had an opportunity of making some expe- 
 riments with the calcined mineral referred to in the preceding 
 paragraph. I found it exceedingly hard, and difficult to 
 reduce to a sufficiently minute state of division, but after 
 this was effected, a mass which had been squeezed into the 
 bottom of a jar, and immediately immersed, set perfectly in 
 thirty-eight hours, and gradually hardened ; but a ball of the 
 same paste fell to pieces in half an hour. It appeared that in 
 the first case a thin superficial layer of the cement was dete- 
 riorated by the action of the water, and became detached 
 from the rest of the mass, but as it could not leave its position, 
 (the surface of the paste being horizontal,) it served as a pro- 
 tection to the parts underneath. In the ball, on the contrary, 
 similar deteriorated parts at the sides and underneath, having 
 no support, fell from it, and exposed fresh surfaces to the ac- 
 tion of the water, which were again destroyed by it, till the 
 whole had fallen to pieces. In the mass which set there was 
 a thin layer of this powder covering the surface, which was 
 of a harsh meagre description, altogether devoid of consist- 
 ency. The cement beneath was in a fortnight already very 
 hard, so that no mark whatever could be made upon it by the 
 nail. It split the vessel (which was a preserve jar of 2| inches 
 diameter) in which it set, and the crack very slowly, but per- 
 ceptibly, widened day by day, being at the end of the fort- 
 night about T Vth of an inch in width. A quantity of the pow- 
 der which had been diffused in water and allowed to settle, 
 and had remained undisturbed during fourteen days, was 
 found to have some consistency, and seemed inclined to set. 
 A thick fluid pulp which had been poured into a phial so as to 
 till it, and tightly corked up, had solidified, and was become 
 nearly dry, but its hardness was not then of the kind that is 
 acquired by immersion, or by drying in the open air, and was 
 more like that of mortar which has dried in the heap. It 
 seemed to want the previous condensation. — Tjr. 
 
150 appendix. 
 
 Since the above was sent to press I have met with the notice 
 of a paper on the sole efficacy of magnesia in rendering certain 
 limr-stones hydraulic, submitted by Bff. Vicat to the Royal 
 demy of Sciences at Paris, and which is thus referred 
 to: — " This paper has for its object the correction of an opi- 
 nion given by Iff. Berthier in the Journal des Mines of 1832, 
 that magnesia alone has no more efficacy than alumina to 
 render lime hydraulic ; from which it would follow that silex 
 was the only essential principle in all cases." 
 
 M. Vicat was, for a long time, of the same opinion, which 
 he now declares incorrect ; and says that magnesia alone, 
 when in sufficient quantity, will render pure lime hydraulic. 
 lie does not explain the degree of energy of these new spe- 
 cies of lime, but only affirms that they will solidify from the 
 sixth to the eighth day, and continue to harden in the same 
 manner as ordinary hydraulic lime. 
 
 Until his experiments are further advanced, he states that 
 the proportions of magnesia, taken and weighed after calcina- 
 tion, should be from 30 to 40 for every 40 of pure anln-drous 
 lime. The native lime-stones examined and cited by M. 
 Berthier contained only from 20 to 20 of magnesia for every 
 78 to 00 of lime. It is probable that this want of proper 
 proportions was the cause of his negative results. M. Vicat, 
 in conclusion, points out the importance of these observations ; 
 hydraulic lime never having been found in the calcareous for- 
 mation below the lias, is because the dolomites have never 
 been examined, but it is now probable it may be found in 
 iliis lower formation." — Vide Journal Frank. Inst. Vol. xviii. 
 No. 4.— Tk. 
 
 (VII.) It was for a long time thought, according to Berg- 
 mann, that the virtue of hydraulic lime depended upon the 
 presence of a few hundredths of manganese. Guyton was of 
 tlii^ opinion. Smeaton, the English Engineer, had remarked, 
 earlier than 1756, that the limes of England fitted for sub- 
 aqueous constructions, all left an argillaceous sandy residuum 
 after solution in nitric acid. (Construction of the Eddvstonc 
 
API'ENDIX. 151 
 
 Lighthouse, extracted from the " Bibliotheque Brittanique.") h 
 Thirty years alter, Saussure announced that the lime of Cha- 
 niouni, although destitute of manganese, hardened under 
 water, whence he inferred, with reason, that that property de- 
 pended solely upon the clay. (Tour in the Alps by Saussure.) 
 Lastly, Colets-Descotils, on analysing the compact marl of 
 Scnonches, in 1813, found in it very nearly a fourth of silica, 
 a circumstance which led him to conclude that " the cause of 
 the phenomenon was due to the presence of a large quantity 
 of siliceous matter, disseminated in very fine particles through- 
 out the texture of the mineral." 
 
 The opinion of Descotils did not invalidate that of Saussure, 
 inasmuch as clay generally contains more silica than alu- 
 mina ; and besides, the two chemists perfectly coincided in 
 the opinion, that the oxide of manganese, if not useless, was 
 at least not an essential element. Such was the state of 
 the question in 1813. To put an end to all these doubts, 
 we determined at this time to proceed synthetically, and to 
 compound hydraulic limes at once, by calcining different 
 mixtures of common lime slaked spontaneously, and clay : 
 the success exceeded our expectations. All rich limes, soft 
 to the touch, afforded the same result. Our experiments, 
 repeated at Paris in 1817, with the lime of Clayes and 
 Chanipigny, and the clay of Vanvres, soon afterwards in 
 England by M. St. Leger, at Nemours by M. Giraut, and 
 in Russia by Colonel Raucourt de Charleville, coincide with 
 one another without exception. 
 
 M. Berthier, Engineer in chief of mines, has since 
 thrown much light on these phenomena, by studying the 
 action of lime, in the dry way, on the oxides, silica, alumina, 
 magnesia, and the peroxides of iron and manganese, taken 
 singly, and afterwards two and two, &c, &c. The results 
 
 >' The Abcrthaw lime-stone left a muddy residuum, which being brought 
 into an argillaceous state, was very tough and tenacious while soft ; and 
 when sufficiently hardened, being worked into a little ball, and dried in 
 that slate, appeared to be a very fine compact blue clay, weighing nearlv 
 one-eighth of the original masb — Ibid. p. 107. 
 
1.V2 APFENDIXh 
 
 at which this able chemist has arrived, are comprehended in 
 the statement preceding the number of this note (in Chap- 
 ter I.). The reader who is anxious to make himself ac- 
 quainted with them in all their details, will find them in the 
 22d volume of the " Annales de Chimie et de Physique," 
 page (i-. 
 
 NOTES ON CHAPTER II. 
 
 (VIII.) The effects of calcination are not confined to driv- 
 ing off the water of crystallization and carbonic acid from 
 compound limestones ; it further modifies the constituent 
 oxides, one by the other. In fact, if we treat an argilla- 
 ceous carbonate of lime by a weak acid, it forms a deposit 
 or insoluble residuum more or less abundant. After cal- 
 cination, on the contrary, a complete solution is effected ; 
 the clay therefore has entered into combination with the 
 lime. 
 
 The arenaceous lime-stones still leave an insoluble residue, 
 when we submit them to the action of acids after calcination ; 
 and this deposit is more nearly equivalent to what we should 
 get on treating the carbonate, in proportion as the size of 
 the quartzose grains is greater. 
 
 It follows from this, that when the silica, in lieu of being 
 minutely divided, as in clay, is on the contrary, dispersed 
 through the calcareous fabric in the form of sand, its cohe- 
 sion cannot then be overcome, or at least only in an imper- 
 fect degree. 
 
 Descotils, to whom a part of these observations is due, 
 justly concluded, that silica does not assist to render lime 
 hydraulic, except in so far as its extreme attenuation allows 
 it to be acted upon by the lime, and enter into combination 
 with it in the dry way. From this we may understand, how 
 there may be limes which are not hydraulic, although con- 
 taining a notable quantity of silica. 
 
 I \.) Dalton has observed that a current of aqueous vapour 
 
APPENDIX. l.->:} 
 
 .ice delates the reduction of lime-stone into lime'. This re- 
 mark ought not to be passed over, in reference to its economy 
 of fuel. We should do well then, if when burning during 
 the dry season, we were to sprinkle the lime-stone with water 
 before charging the kiln with it, and from time to time throw 
 a few buckets of water on the burning faggots near the eye 
 of the kiln. Or, if we are burning coal, to place a large vessel 
 filled with water in the draught of air at the mouth of the 
 vault. We are informed that Lord Stanhope has made a 
 successful application of this principle in England. 
 
 (X.) The carbonate of lime,w 7 hen violently heated in a close 
 vessel, melts, and afterwards crystallises on cooling, arranging 
 itself anew in the state of carbonate ; this observation is due 
 to the chemists Hall and Watt; it is more than half a 
 century old. 
 
 The carbonate of lime alloyed with clay, when burnt in 
 contact with charcoal, does not become converted into nearly 
 so good an hydraulic lime, as when it is burnt with coal. 
 And the fire from coal, in turn, does not answer so well as 
 the blaze resulting from the combustion of wood or furze. 
 An authentic experiment made at Nevers in 1825, has proved, 
 that charcoal can deprive hydraulic lime of a half of the 
 
 ' M. Gay-Lussac, (Annates de Chimie, No. 63,) has recently proved 
 this by the following interesting experiment. He filled a porcelain tube 
 with fragments of marble, and attached a retort containing water to one 
 end of it. Heat was applied to the tube till the carbonic acid began to 
 be disengaged from the marble, and it was then slackensd to a dull red, 
 when the gas ceased to come over. On now heating the water in the 
 retort, and allowing the vapour to pass through the tube containing the 
 ignited fragments of carbonate of lime, a copious extrication of gas imme- 
 diately ensued, which ceased the moment the supply of aqueous vapour 
 was cut ofF, and was again disengaged on its renewal. By a similar expe- 
 riment, M. Gay-Lussac found that the same effect was produced by a 
 current of atmospheric air, whence he concluded, that the effects in each 
 case were to be attributed to mere mechanical agency. But the last ex- 
 periment would, I have reason to think, have failed of success, had the 
 air been previously freed from moisture ; as Dr. Faraday has long since 
 proved, that when the aerial current has been carefully dried by passing it 
 through sulphuric acid, carbonate of lime may be exposed to the heat of 
 the oxyhvdrogen blow pipe, without material loss of carbonic acid. As 
 
l.-,l APPENDIX. 
 
 cner^v which it would have acquired, bad it been burnt with 
 the common flame heat. Colonel llaucourt, the Engineer, hM 
 
 on his part observed, that a mixture of pure lime and clay, 
 burnt at oue time on an iron plate heated to redness, and at 
 another in a kiln, constantly gave good hydraulic lime ; 
 whilst the same mixture, if burnt with charcoal, merely pro- 
 duced a poor lime. These facts not only establish the utility 
 of the contact of the atmosphere in burning argillaceous 
 lime-stone, but they lead to the belief that an absorption of 
 oxvgen may help to exalt those qualities, which hydraulic 
 lime owca iwr nlinllj to its combination with clay 1 . This 
 opinion however is not, after all, supported by any fact. 
 
 (XI.) Different degrees of calcination may cause lime-stones 
 to lose from 10, 15, "20, to 40 per cent, of their weight. Tkdf 
 we have various subcarbonates with excess of base, some of 
 which slake in water, and some not 1 : these last possess pome 
 remarkable properties which we shall explain. Having di- 
 vided a certain quantity of pulverized chalk into ten equal 
 parts, we spread the first portion upon an iron plate heated 
 to a cheiTv red, where it underwent a calcination of three 
 minutes : the second was left six minutes, the third nine, and 
 
 no mention is made in the account of If. Gay-Lus-ac's experiment, of 
 this precaution having been attended to, it is very probable that it may 
 
 been omitted, and that tliis circumstance lias led the di>tinguished 
 French chemist to adopt a theory of the action of the vapour, which 
 seems to be quite inconsistent with the fact abore stated. — Tb. 
 
 k On the other hand, Colonel Pauley remarks, that coal dust, (which i< 
 a de -oxidating substance,) though not absolutely necessary to all artificial 
 cements, does no harm to any; and his experiments proved that it often 
 did good. A proportion of about one-twentieth of the compound was 
 mixed previous to burning, the object being to restore the iron of the day 
 as much as possible to the state of protoxide, during the calcination. 
 (Observations on water cements, p. 6.) The clay used in his experiments 
 was of a blue colour, very soft and fine, and was obtained from the lied. 
 wavat low water, by digging from one to two feet below the surface of the 
 mud. — Tb. 
 
 1 Mr. Higgins found that lime-stone or chalk heated to ndness in a 
 covered crucible, or in a perforated crucible through which the air circu- 
 freely, loses only about one-fourth of its weight, however loaf 
 
 be continued. (Vide Experiments on calcareous < < i:.< m-. p. b., — Ta. 
 
APPENDIX. 155 
 
 so on to the tenth, which consequently liad to remain for half 
 an hour. During each operation the powder was well stirred 
 in every direction, to assist the equal distribution of the heat. 
 The ten portions so calcined were then kneaded up with a 
 little water, and brought each to a stiff' paste of the very 
 same degree of consistency. During this manipulation, not 
 the least sign of effervescence or expansion was exhibited. 
 The first numbers merely exhaled the common odour of 
 moistened chalk ; the latter ones exhaled in addition the 
 alkaline smell peculiar to lime, and gave pretty decided indi- 
 cations of causticity. 
 
 After two hours of immersion, all the numbers, excepting 
 the first, had set ; and after four days, it was altogether im- 
 possible to thrust the finger into them. In a word, the first 
 evidence of this solidification, was so similar to that of the 
 hydraulic limes, that it was impossible not to mistake it for 
 it m . But the sequel did not justify the hopes which we had 
 a right to form ; it is for this reason that we expressly give 
 warning against the trial of lime-stones by a calcination 
 effected on a small scale, that is to say, with small portions 
 of material subjected to a chimney or stove heat. 
 
 During the time that we were engaged upon these experi- 
 ments, M. Minard, Engineer in chief of roads, observed on 
 his part analogous phenomena ; but, being without doubt 
 deceived by the rapidity of the first set, this Engineer prema- 
 turely announced, that a properly regulated calcination could 
 be made to bestow upon nearly all pure calcareous sub- 
 stances, the property of furnishing at pleasure, either rich 
 lime, or natural cement analogous to Parker's cement. Un- 
 fortunately the sequel has failed to confirm these predictions. 
 Our own experiments, as well as those which M. Berthier 
 has since made known, have completely invalidated them. 
 
 m It is remarkable also, that rich limes when partially regenerated by 
 the carbonic acid of the atmosphere, appear to possess similar properties. 
 Col. Raucourt de Charleville found that common rich lime, after falling 
 spontaneously, by exposure to the air under a shed, and being stirred from 
 time to time to equalize its action, had acquired hydraulic properties in a 
 month's time, so as to be capable of setting under water when used cither 
 
i:>i; \iti\i.i\. 
 
 If. Berthier is of opinion, that when we throw water upon 
 the sub-carbonates, they we changed into hydro-carbonates, 
 or combinations of the hydrate, and the ordinary carbonate 
 of lime ; combinations which are feeble, and of little perma- 
 nency in the water". 
 
 The sub-carbonates with excess of base, are much more 
 difficult than the neutral carbonates to reduce completely into 
 lime by a second calcination ; a circumstance which ac- 
 counts for the old opinion common to all the master lime- 
 burners, viz. that it is impossible, let you burn a whole forest, 
 to transform into lime a lump of the stone, which has been 
 chilled before the completion of the calcination. 
 
 M. Lacordaire, Engineer of bridges and roads, employed 
 on the works at thejunction of the Burgundy canal at Pouilly, 
 having repeated the experiments made by M. Minard and 
 myself on the pure lime-stones, upon the argillaceous ones of 
 Auxois, has discovered that the latter, when in the state of 
 sub-carbonates, become real natural cements. This observa- 
 tion has led to a number of happy applications to the ad- 
 vantage of the works which he is directing. Thus he has 
 reduced the continuance of the heat, which is usually for six 
 to eight days in ordinary kilns, to three, being confident in 
 his power of turning to account the unburnt lumps which 
 were necessarily formed by this diminished consumption of 
 fuel. To effect this, he slaked the lime by immersion, separated 
 from it the sub-carbonized parts, which he afterwards reduced 
 mechanically to powder, and incorporated with the mortar. 
 
 By a singular coincidence of circumstances, the quantities 
 
 n Some specimens of mortar which I examined in the course of my 
 experiments, and in which the lime was perfectly unalterable by the ac- 
 tion of tests, (being completely neutralized,) exhibited a large deficiency 
 of carbonic acid, although they were in a state of such entire disaggrega- 
 tion, as to leave hardly room for the supposition that a union between 
 i lie silica and the lime, (vide art. 309,) could have taken place. In these 
 there was a considerable quantity of water in chemical combination, and 
 it seemed to me probable, that a bydrated sub-carbonate of lime bad been 
 formed, together with the true carbonate, with which it was mechanically 
 mixed ; and it is remarkable that the mortars whose analyses led me to 
 suspect the existence of the hydro-subcarbonate, were some which had 
 I n prematurely mined bv exposure to damp. — Tr. 
 
APPENDIX. 157 
 
 of quick lime and sab-carbonate furnished by each charge, 
 were found to be in the respective proportions (from 12 
 to 15 cubic metres of the sub-carbonate, to 48 or 45 cubic 
 metres of lime) which experience demands for the pro- 
 duction of the best possible hydraulic mortar (of mor- 
 tars of this kind,) with the addition of a natural calcareous 
 sand found in the country. The economy afforded by the 
 manufacture of this new kind of mortar, cannot be looked 
 upon as a general result. It depends essentially upon the 
 imperfection of the lime-kilus in the neighbourhood of Pouilly, 
 the dearness of fuel, and the scarcity of sand. But let the 
 price of wood or coal be taken at the average rate which it 
 bears every where else, and the form of the kiln be modified 
 in such a way, as to do away with the necessity of expend- 
 ing as much caloric in burning the last fourth or filth of the 
 charge of stone, as is required for first 3-4ths or 4-5ths, 
 then the method of M. Lacordaire will maintain none of its 
 advantages. The mortar of sub-carbonate of lime does not 
 seem as yet to have been exposed to the action of the wea- 
 ther. It is impossible to form a judgment of its actual qua- 
 lities, until varied experiments have sanctioned its use on all 
 occasions. 
 
 (XII.) At the Monsieur canal (a field kiln is used), seventy- 
 five cubic metres of lime required, on an average, 26 cordes 
 of wood (oak). The corde measures 4.74 stores, which 
 makes 1.64 st. per cubic metre . 
 
 At the bridge of Souillac, (the kiln is cylindrical, sur- 
 mounted by a cone,) a hundred metres of lime required, on 
 an average, 107 steres of wood (oak), which is 1.70 st. per 
 metre. 
 
 At the Monsieur canal, (the kiln was a field one) forty- 
 seven cubic metres of lime required, on an average, 7000 
 faggots, measuring together 1050 cubic metres, which comes 
 to 2.234 st. per metre. 
 
 The reader will recollect, that the stere (which is a measure only ap- 
 plied to wood, faggots, &c, &c.) is equal in capacity to the cubic metre ; 
 hence the relative proportions laid down in this and the succeeding para- 
 
158 APPENDIX. 
 
 At Saint Brieux, (the kiln ovoidal,) fifty cubic metres of 
 lime required 2500 fascines of broom, measuring together 
 1500 st., which makes 30 steres per metre. 
 
 At Cartravers (the kiln is ovoidal), thirty cubic metres of 
 lime take, on an average, 15,000 fascines of broom, measuring 
 together 900 St., which makes 30 steres per metre. 
 
 In the coal kilns by slow heat, at Cahors, twelve cubic 
 metres of lime consume, on an average, 1 cubic metres of coal. 
 (The kilns are inverted cones.) This comes to 0.33 Oh per 
 metre. 
 
 In the coal kilns, by slow heat, at Done (Maine et Loire), 
 seventy-eight cubic metres of lime consume, on an average, 
 29m. 80c. of coal (the kilns are ovoidal), which comes t" 
 Oin. 36 c. per metre. 
 
 The broom and the faggots were measured in large piles, 
 and consequently, with the bulk which the pressure they 
 were then subject to, gave them. 
 
 (X11I.) We had occasion, in 1824, to visit the coal kilns esta- 
 blished at Paris, near the bridge of Jena, for burning the artifi- 
 cial hydraulic lime. These kilns, which were built of the shape 
 of inverted cones, after the old method, worked badly. The 
 quantity of " core," or unbumt lime was constantly so great, 
 that it could not be exposed for sale without previously pick- 
 ing out the worst parts. We again visited these same kilns 
 in 1826, and they worked very well. No change had been 
 made, either in the shape, or capacity of the cones; the im- 
 provement was owing — 1st, To their not lowering the u 
 at each drawing of the charge more than from 30 to 35 centi- 
 metres (11. S3 to 13.78 inches, Tr.), instead of 0.04 m. 
 (25.2 in., Tr.),the limit used before. 2dly, To their finishing 
 the charge at the level of the top of the kiln, in lieu of heaping 
 it up in a pyramid as was done before. 3d, and lastly, To the 
 use of a peculiar mixture of coal and coke, and to a well 
 regulated and uniform distribution of this mixed combustible. 
 
 graphs, may be applied with equal oonectnesa to any other kind of mea- 
 sure : f'>r instance, in the present case, acubic yard of lime would require 
 1.64 yard-, of wood. — Tn. 
 
APPENDIX. 159 
 
 (XIV.) The ovoidal kilns are subject to the same caprices 
 ;b the conical ones. They have been seen to work perfectly 
 well lor a long period, and then become suddenly out of order, 
 without any apparent cause. 
 
 The lime furnished by the kiln whose section is given in 
 fig. 9 (plate 1), is always either too much or too little burnt. 
 A current of flame, probably owing to the sudden contraction 
 of the upper opening, rises with force by the circumference, 
 while the middle bums badly. 
 
 The kiln, fig. 10, has been a long time in use, it works 
 tolerably; but Xos. 11 and 1-2, in the last section, answer 
 the best. Number 11 produces 6.84 cubic metres (24 Ik cubic 
 feet,Tr.), and No. 12 — 4. 50 cubic metres (158.8 cubic feet,Tr.) 
 of lime per day. 
 
 It is in the ovoidal kiln, that Messrs. Debline and Donop 
 propose to burn lime with a peat fire. They affirm that two 
 steres of that material, which do not cost more than half the 
 price of wood, are sufficient to burn a cubic metre of lime ; 
 there is therefore much benefit to be derived from using it, 
 wherever it is provided by nature. (The Society of Encou- 
 ragement have decreed to Messrs. Debline and Donop the 
 prize which it had proposed for the invention of an econo- 
 mical mode of burning, applicable to the manufacture of lime.) 
 The turf is placed upon a grate fixed beneath the vault of the 
 charge, and burns with a flame, in the manner of wood. 
 
 (XV.) In the flame kilns from five to seven metres (10.4 to 
 23 feet, Tr.) high, it is extremely difficult, or rather impos- 
 sible, to burn the upper layers properly, without exceeding 
 the measure of right calcination for the lower strata ; this in- 
 convenience is of little moment with respect to rich lime ; 
 but it is accompanied by serious consequences with the argil- 
 laceous lime-stone, which in such case vitrifies, and is no 
 longer good for any thing. 
 
 We have proposed to the Administration of Roads and 
 Bridges, a kiln, and a mode of calcination, which would appear 
 to obviate the inconveniences above mentioned, at least in a 
 great measure. The following is a description of it. 
 
 *C 2 
 
160 APPENDIX. 
 
 The form of the lower part of its interior, to the height 
 of about two metres (6£ feet, Tr.), is cylindrical, on a cir- 
 cular, or elliptic base (figs. 5 and 6, plate 1). The remainder, 
 to the height of 5 metres (16.4 feet, Tr.), is finished off by a 
 conical hood truncated at its vertex, so as to leave an opening 
 of in. 60 (23.6 in., Tr.) for the smoke and heated air. The infe- 
 rior capacity is divided by partitions into two or three rounded 
 chambers. In the first case, the partitions are raised 3 metres 
 (9 ft. 10 in., Tr.), in the second 2.60 metres (8 J- feet, Tr.) 
 above the floor. The object of these various arrangements is, 
 1st, to avoid angular parts, in which the calcination always 
 proceeds badly ; 2d, to keep up the intensity of the heat in 
 the upper parts, by a more powerful concentration than takes 
 place in prismatic or cylindric spaces whose sides are per- 
 pendicular ; 3d and lastly, the partitions are intended to be 
 adapted for the alternate calcination of the lower strata, with- 
 out the discontinuance of it to the upper layers. For instance, 
 supposing the kiln with three chambers to be loaded on 
 vaults, as is usual, with an easily verifiable argillaceous lime- 
 stone. We shut very exactly the openings of the two 
 fires, b and c. (fig. 6, pi. 1.) We light that in d, and keep 
 it up for two days. Before the close of the second day, 
 we unclose the opening of the kiln />, and ignite it with- 
 out delay; as soon as it begins to draw, we imperceptibly 
 slacken that of d, which we allow to go out altogether, when 
 b is in full activity, by quickly closing the aperture. We 
 change the fire of b for that of c with the same precautions. 
 It will then by this means ensue, that the whole of the upper, 
 and one portion of the middle region, will have undergone 
 144 hours of the direct heat, while the lower parts will only 
 have received 48 hours of the same heat. 
 
 The kiln with two chambers, is intended for the argilla- 
 ceous lime-stone of medium hardness ; we proceed in the man- 
 ner above described, and each chamber will receive 72 hours 
 of the direct heat. 
 
 The height of the partitions, and the continuance of the 
 heat in each chamber, are evidently two circumstances which 
 
APPENDIX. 101 
 
 depend upon the hardness of the stone, the quantity of clay 
 it contains, and the heat given out by the wood within a given 
 time, according as it may be green or dry. One or two ex- 
 periments made by an intelligent foreman, ought to be suf- 
 ficient to decide all these questions. Besides, nothing is 
 easier than to raise or depress the partitions, without in the 
 least injuring the body of the kiln. 
 
 Much stress ought to be laid upon the necessity of chang- 
 ing the heat from one fire to the other, without in the slightest 
 degree slackening its continued and general action in the 
 regions situated above the partitions. 
 
 When, by reason of its peculiar nature, or its friability, the 
 lime-stone is incapable of bearing the pressure to which the 
 vault and piers of the charge are subjected, that vault is 
 divided into two others, by placing a pier in the middle. 
 Should this precaution appear insufficient, we build the facing 
 of the piers, and the first course of the intrados of the vault, 
 with incombustible stone, or common lime-stone. The latter 
 expedient, in a word, consists in building a skeleton vault 
 of refractory bricks, as is practised in the pottery furnaces. 
 
 NOTES ON CHAPTER III. 
 
 (XVI.) At the canals of Saint Martin and Saint Maur, the 
 artificial hydraulic limes have been put to every possible 
 proof; they have been applied to the masonry of locks, to 
 the coating of the basins, to subterranean vaults, &c, &c. 
 The following are other instances, in which mortar manu- 
 factured with the same ingredients, has fulfilled different 
 functions. 
 
 1. At the bridge Duke D'Angouleme, over the Dordogne at 
 Souillac, the foundation of one of the piers is entirely laid 
 on a beton composed of sand, flints, and artificial hydraulic 
 lime. This beton was immersed in five metres (16.4 feet Tr.) 
 reduced depth, across a current, in a caisson without a bot- 
 tom. Alter eight months it bore the weight of 2,500,000 
 
lb'2 A IT). N nix. 
 
 kil. (2402 tons, 7 rift*. 2 qrs. 0^ lb., Tr.) distributed over a 
 surface of eighty metres. ([)') sq. yds., (i ft. 70 in., Tr.) p . 
 
 2. The bridge of Melisey is in the .same way founded aped 
 a bed of beton of artificial hydraulic lime. 
 
 3. In the repairs of dilapidations, made at the bridges of 
 Tavernay and liaudoncourt, with the same lime made use of 
 at the bridge of Melisey ; the beton immersed did not after 
 fifteen days sink more than two millemetres (.08 inch, Tr.) 
 under the pressure of an iron needle a centimetre (.89 inch, 
 Tr.) square, loaded with a weight of 300 kilogrammes 
 (5 cut. 3 qrs. 17 lbs. 14 oz., Tr.). The experiment was made by 
 If. Laeordaire. Engineer. 
 
 1. Experimental pointing with mortar, eomposed of sand 
 and hydraulic lime, made use of at the base of the Triche 
 mole at Saint Malo, on the 12ih July, 1821, by M. Robinot, 
 (be engineer. This mortar, which was introduced into joints 
 from which the water flowed as from a spring, had, when we 
 visited the work, resisted the actiop of the sea for the years 
 1821, 1822, 1823, 1824. It was in very good condition, 
 although over dosed with lime. X<>w. there is no Engineer, 
 who is not aware of what the effects of the ocean upon 
 the mortars of revetments are at Saint Malo. M. Bernard, 
 Engineer of bridges and roads, attached to the works at the 
 harbour of Toulon, wrote me word on the 20th October, 
 1820, that having had oeeasion to demolish certain portions 
 of masonry, fioe <>/■ nx pmuthtC old, he found that the mortal 
 
 Of artificial lime which had been made use of, had already 
 bound the stones together with such force, that it was often 
 
 more ea^y to break them, than to tear them asunder. All 
 Paris could in 1826 have witnessed the hardness which the 
 beton of the lloor of the basin at the canal of Saint Martin 
 had acquired. The fragments which were taken out where 
 the lloor had sunk, were like mill-sione ; it was therefore 
 determined to turn them to use. They were broken by hea\ y 
 
 I i.i- b ;it the latent about 6402 lbs. j» r Lngli-h square foe*; 01 
 uurh 4Jllib. per square inch — Ti.. 
 
APPENDIX. 163 
 
 blows of a mallet, in order to employ them in lumps for the 
 fabrication of a new beton destined to repair the breach. 
 These examples will suffice, we trust, to show the value of 
 those attempts which some persons have made, to cast a slur 
 upon the efficacy of artificial mortars. We have been 
 anxious, in the preceding pages, to rest solely upon examples 
 in the large way. The experiments on a small scale, would 
 not have been sufficiently conclusive ; on this account we 
 have passed over in silence, the examination instituted by the. 
 Council of Civil Buildings* on the -24th December, 18-21, and 
 the detailed report of the Commission nominated for that pur- 
 pose. From which report it results, that the artificial lime at 
 Paris, is superior to the natural hydraulic lime of Senonches 
 for the first few months of immersion. The experiments of the 
 Commission being incompetent to establish the progressive 
 law of solidification, we ought, in fact, to refrain from coming 
 to any conclusion, as to the future state of the limes compared 
 together. 
 
 (XVII.) The efficacy of the oxide of manganese, first sup- 
 posed by Bergmann, and afterwards assented to by Guy ton, 
 suggested to the French chemists, two methods of procuring 
 artificial hydraulic limes; the first, consisted in mixing four 
 parts of grey clay, and six parts of the black oxide of manga- 
 nese, with ninety parts of lime-stone reduced to powder, and 
 calcining the mixture. The second, was to add to common 
 quicklime, a certain quantity of white iron-stone, which is in 
 great part composed of carbonate of lime and manganese. 
 
 These two methods, supposing them to be good, must have 
 been of very limited use ; for the peroxide of manganese, and 
 the white iron stene, although abundant natural products, are 
 nevertheless not so much so, as to be used as materials for 
 large buildings. 
 
 M. Pach, Professor of the Arts and Sciences at Stockholm, 
 informed me that, in reliance upon M. Bergmann, they had in 
 Sweden constructed a whole lock with mortar of rich lime 
 and the peroxide of manganese, but that the wretched con- 
 dition of the masonry had necessitated its demolition. 
 
l(i| APPENDIX. 
 
 (XVIII.) We shall lievc relate the particulars of the first 
 attempt at the manufacture which has been made on a large 
 scale. It took place at the works of ihe bridge of the Duke 
 d'Angouleme, at Souillac. 
 
 They had a large stock of rich lime slaked to powder bj 
 immersion, and kept in that state under a shed. A guy. 
 slightly effervescent clay of the neighbourhood was procured. 
 This, when dried in the sun, and reduced to fragments of the 
 size of a nut, acquired the property of dissolving and dif- 
 fusing itself spontaneously in water, forming a pulp, which it 
 was sufficient to stir about a few seconds, to render very fine. 
 To effect the mixture of the materials, a score of little heaps of 
 lime in powder, about one-fourth of a cubic metre (fMJ cubic 
 feet, TV.), were made on an area of a certain size. Each of 
 these being hollowed in the middle like a funnel, received a 
 fluid pulp, composed of Om. 03 c. (1.059 cubic feet, Tr.) 
 of clav and tvater, in such proportions, that by beating and 
 amalgamating them with the aid of pestles, there resulted a 
 tolerably stiff paste. The partial products of each division 
 were accumulated together into two or three large heaps, 
 which were allowed to acquire such a consistency, as to 
 admit <>f their being afterwards divided into irregular fragments, 
 by means of shovels, or an adze. These fragments, which 
 were of the size of small blocks (" moellon "), were removed 
 and spread out on the ground, to acquire a proper degn 
 hardness by drying. They were afterwards taken up, to be 
 housed under a shed appertaining to a lime-kiln, like No. 5, 
 pi. 1 (except the partitions), and of the capacity of 100 cubic 
 metres. (130 cubic yards, 20 feet, Tr.) 
 
 The base of the charge of the kiln was composed of com- 
 mon lime-sti'iif, and the upper part, of the artificial lime. 
 
 An exact extract from the list of the ''ays' labour, and other 
 items of expense, gives the following detail: — 
 
MI'INDIX. 165 
 
 Materials. 
 
 Francs. 
 
 34 in. 55 c. (45 cub. yds., Tr.) rich lime in the caustic 
 state, which will be made by the burthen of the 
 kiln [v. statement) 00.00 
 
 5 m. 76 c. (7^- cub. yds., Tr.) of clay, measured in 
 
 powder, at 6 francs q per metre 34.50 
 
 43 m. 18 c. (56'4 cub. yds., Tr.) of lime-stone of rich 
 lime, to furnish the lime credited ; and to form the 
 base of the charge, at 3 f. 1*29.54 
 
 150 m. (196 cub. yds., Tr.) steres of fire-wood, 
 at 4 f. 20c 630.00 
 
 Carried on F. 794.10 
 
 Workmanship. 
 
 Francs, 
 
 Brought forward 794.10 
 Slaking 34 m. 55 c. of rich lime by immersion ; 50 
 
 days' work, at 1 f. 50 c. per day .... 84.00 
 Mixing the same lime with the clay ; 140 days, at 
 
 If. 50c 210.00 
 
 Dividing the paste and putting out to dry in the sun ; 
 
 65 days, at 1 f. 50 c 97.50 
 
 Lifting the fragments, about 50 cubic metres {65 vds. 
 9 ft., Tr.), carrying them, and measuring them 
 under the shed; 16 days, at 1 f. 50 c. . . . -24.00 
 Loading the kiln with 43 m. 18c of lime-stone, in- 
 cluding building the vaults ; and also with 50 
 cubic metres of artificial lime : — 
 
 7 days, a master burner at 3 f. .... 21.00 
 30.40 assistants at 2 f. 72.80 
 
 Carried over, 1303.40 
 
 1 As the cost of materials necessarily varies with every locality, I have 
 not thought it n e c es sa r y to reduce these items to their corresponding 
 values in English money — Tr. 
 
106 APPENDIX. 
 
 Franrs, 
 
 Brought over, 1303.40 
 
 Burning and keeping up the fire for six days and 
 six nights, as follows: — 
 
 12 days a master burner, at 3 f. . . . 36.00 
 
 24 do. of his assistants, at 2 f . . . . . 48.00 
 
 1 387.40 
 
 Sundries at 20 per cent 277.50 
 
 Cost of 50 cubic metres (05 cubic yds., TV.) of J 
 
 artificial hydraulic lime, which will be dimi-F 
 Dished to 40 (52 cubic yds., TV.) by the£ 
 shrinkage of the material ) 
 
 1664.90 
 
 At this price the metre costs 41 francs 02 centimes. Such 
 is the result of an experiment made under the most unfavour- 
 able circumstanees, that is to say, without the aid of any 
 previous experience, and without any other power for the 
 manipulation, than manual labour. 
 
 At the bridge of Melisey, the cubic metre of twice-burnt 
 artificial hydraulic lime like the above, amounted, inclusive of 
 20 per cent, for sundries, &c, to 38 francs, taken at the kiln ; 
 which is not far from the price which it came to at the bridge 
 of the Duke d , Angouleme r . 
 
 NOTES ON CHAPTBB IV. 
 
 (XIX.) The vapour which rises during extinction, turns 
 paper tinged with mallow, green, which is occasioned by a 
 portion of the lime in a minute state of division, which the 
 vapour carries along with it. 
 
 We introduced successively several kinds of quick lime, 
 still retaining some carbonic acid, into a large earthenware 
 retort, with distilled water ; and then by means of a bent 
 
 r Col. Raucourt dc Charleville estimates thecost of the factitious hy- 
 
 dr.nilic lime, twice kilned, at one-third more than the ordinary (niick- 
 lime of which it is composed. — Esmi. p. 21 i 
 
APPENDIX. 167 
 
 tube, collected the vapours and gas disengaged during the ex- 
 tinction, in a large bottle full of filtered lime water, inverted 
 over a pneumatic trough filled with the same water. When 
 the operation was completed, we corked and withdrew the 
 bottle, which contained about two-thirds of gas, and one- 
 third of lime water, and then shook it for a long time, with- 
 out perceiving any precipitate in the liquid ; having returned 
 and uncorked the bottle again in the trough, not the least 
 absorption was manifested. Lastly, a lighted match burnt in 
 the gas which it contained, without its light changing in 
 colour or intensity ; therefore, there was nothing which 
 escaped from the retort, but common air and water. 
 
 (XX.) The masons say of rich lime which slakes to dryness, 
 that it is scorched, and has lost its properties ; it in fact loses 
 the faculty of producing so fine and so perfect a pulp, as 
 when it passes immediately from the state of quick lime to 
 the state of paste; but it gains in respect to its binding 
 qualities. 
 
 (XXI.) This method of extinction is due to M. de Lafaye, 
 who published it in 1777, as a secret restored from the Ro- 
 mans. He founded his opinion upon a forced interpretation 
 of the expressions " lapis calcis intinctus in aqua," which 
 we find in Vitruvius, Book II. Chap. 5, and " perfundere 
 calcem, perfusio calcis" in Saint Augustin, Book XXI. 
 Chap. 4. of the " City of God." It is sufficient to read at- 
 tentively the passages from which these words are exti'acted, to 
 be convinced of the very small probability of the interpretation 
 of M. de Lafaye. His process was very much in vogue at 
 the time. Fleuret, professor of architecture in the old mili- 
 tary school, published in 1807, under the title of " L'Art 
 de Composer des Pierres aussi dures que le Caillou," a 
 treatise on the fabrication of mortar by Lafaye's process; which 
 process, however, he modifies by endeavouring to retain and 
 turn to use, the purely aqueous vapour which is disengaged 
 at the moment of effervescence. " This vapour," says Fleu- 
 ret, (pages 40 and 41,) " arouses and stimulates the appe- 
 tite of the workmen, whence I conclude, that it contains 
 
168 
 
 APrENMX. 
 
 principles suited to the regeneration of lime, and conse- 
 quently, to the induration of the mortar" The other reason- 
 ings bj which the author endeavours to demonstrate the 
 excellence of his method, are pretty much of the same force. 
 Experience has done justice to the exclusive pretensions of 
 If. de Lalaye, by pointing out in what cases, and with what 
 kinds of lime, it is proper to apply the extinction by im- 
 mersion. It has also afforded an explanation, in the differ- 
 ence of the lime made use of, of the success which M. Fleu- 
 ret met with at Metz. and the disastrous result of his attempts 
 at the basin of Villette. 
 
 Water 
 absorbed. 
 
 Bulk of 
 the paste 
 
 XXII.) 100 kilogrammes of rich lime, 
 
 converted into a thin paste by the first 
 
 process, give 
 
 The same, previously slaked by immer- 
 sion 
 
 The same, first slaked spontaneously . . 
 
 100 kilogrammes of hydraulic lime, re- 
 duced to a thin paste by the first pro- 
 cess, give 
 
 The same, previously slaked by immer- 
 sion 
 
 The same, previously slaked spontaneously 
 
 On examining these results, we see at once the enormous 
 
 • By a mean of three experiments, I found that a cubic foot of dry 
 slaked rich lime, (prepared from sea shells and slaked by immersion,) whin 
 thrown loosely into the measure, and shaken down, but not comprt 
 and then striked, weighed very nearly thirty pounds. And the experi- 
 ments of General Treussart show, that rich slaked limes, when converted 
 from the drv powder to the state of paste, are reduced to about one half 
 their bulk. These facts will be of use in reference to some of the direc- 
 tions contained in this work, which generally apply to mixtures of sand 
 with lime in the latter condition. — Tb. 
 
 1 As the numbers in this table are merely comparative, I have thought 
 it better not to encumber it, by reducing them to their equivalents in 
 English weight. — Tr. 
 
 Kil. 
 
 VoL 
 
 291 
 
 350 
 
 17Q 
 
 234 
 
 188 
 
 258 
 
 105 
 
 137 
 
 71 
 
 127 
 
 68 
 
 100 l 
 
APPENDIX. 1G9 
 
 difference in expansion, which results with the rich limes, 
 from the adoption of the two last methods of extinction. We 
 notice besides, that with the exception of the very white 
 limes, all the others acquire a clearer colour by the ordinary 
 mode of extinction, than when they are subjected to spon- 
 taneous extinction, or extinction by immersion. Now we 
 know, that many substances may be blanched, and acquire 
 clearness, by a minute subdivision of their particles, which 
 become so many more faces adapted to reflect white light. 
 Such arc the black marbles, green bottle-glass, &c, and 
 which give white powders by pulverisation. 
 
 (XXIII.) Let us suppose, that making use of the three com- 
 mon processes of extinction, we have prepared three equal 
 volumes, V, V", V", of the same degree of consistency, (in 
 thin paste,) with the same rich lime ; the elements of V 
 being, for instance, 
 
 kil. kil. 
 
 Quick lime . . 100 . . water 290 
 Those of V" will be . . 150 . . do. 253) including some 
 Ditto V" will be . . 135 . . do. 254j carbonic acid. 
 If then to each of these equal volumes V, V", V", we add 
 for example, the same quantity of sand, we shall obtain three 
 mortars equally rich in appearance, yet, nevertheless, very 
 different in the proportions of lime and water. The conse- 
 quences of this difference are important. In general, in 
 practice, when we make use of lime slaked by the ordinary 
 process, we never know how much we put into the mortar. 
 In fact, between the limits of the consistency of a good 
 paste, to that of a milky one, the lime may receive from 130 
 to 400 kil. of water for every 100. There is no point esta- 
 blished ; all depends upon the pleasure, or rather upon habit, 
 which guides the hand of the workman entrusted witli the 
 slaking. 
 
 (XXIV.) Rich lime, when slaked in paste, and covered with 
 fresh mould in a trench secure from absorption, may be kept 
 many ages. Leoni Baptiste Alberti speaks, (Book II. Chap. 
 XI.) of having seen lime in an old trench, which had been 
 left for about five hundred years, as many evident indications 
 led them to conjecture; that this lime was still so moist, so 
 
170 \PIMM>I\. 
 
 well tempered, and so rich, that neither honey. norbeaets 
 marrow were more so. 
 
 (XXV.) Lime, housed in this way, becomes earbonised 
 superficially, it forms itself a crust, not very hard to be sure, 
 but sufficiently so to protect the internal particles. Were 
 the powder to rest upon a damp floor, the lime would suck 
 up the water with force, and would pass to the solid or pasty 
 state, according to its being hydraulic or rich. 
 
 (XXVI.) It is this faculty of hardening quickly in a trench, 
 which gives the hydraulic lime so bad a reputation amongst 
 the workmen : so that it is only in the last extremity, and for 
 kick of any other, that they will consent to make use of it. 
 They then endeavour to retard its .set, by drowning it as 
 much as possible; this is what they call deadening it; an 
 expression which is by no means synonymous with slaknitj, 
 but which properly signifies depriving the lime of the power 
 and energy which cause it to harden after slaking. 15 nt 
 spite of their efforts, the hydraulic lime always ends In- 
 hardening in a certain time. They then determine upon break- 
 ing it up with hammers, and working it up to the condition 
 of paste, with the addition of water ; with such a lime as 
 this they make their mortar ; it is needless to enquire if it be 
 of good quality. 
 
 (XXVII.) Extinction by immersion is not, as one might 
 suppose, a difficult operation, more particularly when it is 
 done on the large scale. We shall proceed to describe the 
 method employed atDoue, by Messrs. Ollivier, brothers, con- 
 tractors for the supply of hydraulic lime for the Xantes and 
 Brest canal, for the passage to Xantes. 
 
 On leaving the furnace, the lime is put into a bucket, the 
 bottom of which opens and lets down at pleasure. This 
 bucket is suspended at the end of a rope hooked to the jib 
 of a crane. It is lowered into a basin full of water, and then 
 raised after a few seconds, and a quarter of a turn of the 
 crane brings it above an opening left in the roof of a small 
 vaulted building. The bucket opens by the trigger of a 
 spring, and the lime falls into this building, which they 
 call the magazine of immersion. In it, they thus collect all 
 
APPENDIX. 171 
 
 the lime which leaves the kilns during the day's operations, 
 and next day it is found reduced to powder. The maga- 
 zine empties itself by an opening into a building below; 
 the lime being pushed through this opening, first falls into 
 an iron meshed cylinder, which by a rotatory movement 
 separates the unburn t lumps, and discharges them outside 
 the building. The powder which escapes through the 
 cylinder, falls into a hopper, by which it is conveyed into a 
 second cylinder of metallic web, which performs the office 
 of a finishing bolter. From this it passes into two hoppers 
 fixed to the summits of two vaults, through which they 
 descend. These vaults support the floor of the sifting house, 
 and form the magazine for delivery, on the ground floor. 
 The shoot of these hoppers descends vertically from the 
 summit of the vaults, and opens or shuts at pleasure, over 
 sacks placed at the end of the beam of a balance. 
 
 By these means, more easy to uuderstand than to describe, 
 the lime is slaked, sifted, put into sacks, and weighed, in the 
 most simple and expeditious manner ; it is embarked upon 
 the Loire. In this way it may be earned many months, even 
 a year, without experiencing any deterioration. 
 
 (XXYIII.) A trial on the large scale, with 60 cubic metres, 
 (78 yds. 12 ft., Tr.) of quick lime, at the works of the Duke 
 d'Angouleme bridge at Souillac, proved the excellence of this 
 process. The lime taken from the heap heated and slaked 
 again very well, after five months of a continually rainy winter. 
 
 NOTES OX CHAPTER V. 
 
 (XXIX.) Pure lime and water combined, constitute the 
 hydrate of lime. It is obtained, 1st. In the solid state* 
 white, and more or less pulverulent, by exposing lime, in a 
 pulpy state, to the heat of a spirit lamp. -dly. In a crystal- 
 lized state, by placing lime-water under a glass receiver with 
 concentrated sulphuric acid beside it'j the lime then civstal- 
 
 u Concentrated sulphuric acid being very liable to deterioration bv ex- 
 posure to the air, in consequence of its powerful avidity for moisture, it 
 would be as well, previous to employing it for the purpose for which it is 
 
172 APPENDIX. 
 
 liscs in regular hexahedrons, composed of 0.70 of lime, and 
 0.30 water. 3dly. When a cold saturated solution of lime is 
 boiled, the hydrate of lime is precipitated in the form of 
 small crystals. 
 
 Such arc not the hydrates referred to in Chapter V.j under 
 that denomination we comprehend all the solid combinations 
 or pasty mixtures of water and every kind of lime. 
 
 (XXX.) — *By the method described in the note to Article 82, 
 and availing myself of the advantage of being in superintend- 
 ence of the erection and repairs of numerous public build- 
 ings, I have been enabled to undertake and carry through a 
 connected series of observations, as to the rapidity of the 
 absorption referred to in the text, in the case of stuccoes 
 freely exposed ; and in order to exhibit this action more 
 clearly, I have thrown together in the form of a table, the 
 mean results of many hundred measurements, showing the 
 average progress of induration of mortars of the common 
 sort. But the individual observations themselves are not in 
 such close accordance as might be expected; the depth of 
 penetration of the carbonic acid of the air, being influenced 
 by smoothness of surface, and compactness of structure, to 
 an extent, which renders it difficult to secure close uniformity 
 in the results. 
 
 In referring to this table, however, I ought not to omit to 
 mention, that the whole of the stuccoes from which the 
 measurements were taken, were strictly similar in composition, 
 and were prepared by mixing one measure of aver}- pure slaked 
 lime, with one measure and a quarter of clear sharp sand, and 
 incorporating them well together by beating. They were 
 also laid on and finished in an exactly similar manner, and 
 the different series were all fully exposed in the same situa- 
 tions. The measurements here given, may therefore be con- 
 sidered to approach the true average, under the conditions 
 above stated, as nearly as possible. 
 
 here proposed, to make sure of its energy, by boiling it for a sbort time. 
 Wben this cannot be done, and in those cases in which its use may be 
 attended with inconvenience, the dry chloride of calcium in powdei maj 
 
 be used as a substitute. — Tit. 
 
APPENDIX. 
 
 178 
 
 Table of the Depth of Penetration of Carbonic Acid into different 
 Mortars, after exposure to the influence of the air for various periods. 
 
 TIME OF EXPOSURE- 
 
 1 Week 
 
 2 do. . 
 9 do. 
 
 1 Month 
 
 2 do. . 
 
 3 do. . 
 
 4 do. . 
 
 5 do. . 
 
 6 do. . 
 
 7 do. . 
 
 8 do. . 
 
 9 do. . 
 
 10 do. . 
 
 11 do. . 
 
 12 do. . 
 
 Mean depth of 
 
 penetration of 
 
 the carbonic 
 
 acid. 
 
 Lines. 
 
 0.25 
 
 0.50 
 
 1.0 
 
 1.5 
 
 1.875 
 
 2.00 
 
 2.37 
 
 2.9 
 
 3.3 
 
 3.85 
 
 4.0/ 
 
 4.35 
 
 4.6 
 
 4.8 
 
 4.9 
 
 Being very nearly half an inch at the end of a year's ex- 
 posure. A similar set of experiments was commenced with 
 mortars of eminently hydraulic lime and sand, and in every 
 other respect similar to the above, which as far as thev went 
 gave very nearly the same results. I was, however, compelled 
 to abandon them, before they were sufficiently numerous to 
 exhibit the mean depths for the respective periods with suf- 
 ficient exactness, (by the mutual compensation of errors) to 
 admit of being associated together in a tabular form. — Tit. 
 
 (XXXI.) In plate second we have given representations of 
 the carbonated bands of various sections, cut from prisms of 
 lime and mortar a year old. It would be difficult to credit, 
 did we not see it, how great an obstacle a smoothness of 
 surface presents to the penetration of the carbonic acid. 
 
 It is not certain, besides, that the reunion of this acid can 
 ever be complete, even in the most accessible parts. The 
 following are the results of the analyses of some very small 
 pieces of hydrate of lime, which had been exposed to the air 
 for eight years. 
 
MM 
 
 561 
 567 
 
 424 
 416 
 422 
 
 IS 
 
 2:5 
 11 
 
 
 ("lav anil 
 
 Water. 
 
 510 
 
 570 
 517 
 
 311 
 
 278 
 355 
 
 179 
 252 
 128 
 
 174 APPENDIX. 
 
 Id. W llr . 
 
 f When slaked !>\ the ordinary 
 
 The hydrate of veryN process 
 rich lime gave, for even j Ditto ditto by immersion 
 1000 parts . . . .(, Ditto ditto spontaneously 
 
 m, , , , c ,. , , C When slaked by the ordinary 
 lhehvdrateofsliirlitlvV J J 
 
 , ,.- ,• r > process 
 
 hydraulic lime gave, fori Dj » ^ fa immersion , 
 
 every 1000 parte. . / Ditto ditt0 spontaneous , v . 
 
 Turmeric paper, when applied in a moistened state to the 
 centre of the broken pieces, did not change colour ; they had 
 therefore no causticity left, although the proportions of car- 
 bonic acid were incomplete". We shall observe, moreover, 
 that the hydrates obtained by the second process of extinc- 
 
 u This fact, which has been exhibited by the researches of several 
 eminent chemist-, is so difficult to account for in a satisfactory manner, 
 that I have taken pains to repeat the "analyses of cements exhibiting it, 
 with a view to detect, if possible, any inaccuracy in the process, to which 
 to attribute the apparent deficiency in the quantity of carbonic acid se- 
 parated. The results, however, of many experiments made with this 
 object, have all tended to confirm the statement contained in the text, 
 however anomalous it may appear to be, in reference to the received opi- 
 nions regarding atomic combinations. No case has occurred to myself, 
 among analyses of cements of various ages, in which I have found the 
 lime fully saturated, (although entirely deprived of its alkaline qualities,) 
 and some cases have presented themselves, in which the deficiency has 
 been decidedly marked, even after an exposure of considerable duration, 
 as for instance, one-fourth the equivalent dose of acid being deficient after 
 an exposure of a couple of centuries. 
 
 Thus we see by referring to the table of analyses of old mortars, bv Mr. 
 John (App. LX.), that No. 1, though no less than 600 years old, con- 
 tained only 5 of carbonic acid to 8.7 of lime, being 73 per cent, of the 
 saturating dose ; No. 2, of the same age, contained only 24.3 per cent.; 
 No. 3, 1800 years old, 75 per cent. ; No. 4, the same age, 63± ditto; 
 and No. 5, whose age is not stated, not quite 42 per cent. 
 
 As no reference is, however, made in these analyses, to the use of any 
 tests to ascertain the condition in which the lime existed in the cement, 
 rendering it possible that part might still have remained unaltered by the 
 action of the air, I subjoin the following extracts from analyses by myself, 
 in which that point was particularly attended to ; a part of the specimen 
 operated on being in each case reduced to powder, and minutely examined, 
 to detect the existence of lime in the caustic state ; but invariably without 
 success, although I availed myself, in addition to the usual method, by 
 
APPENDIX* 
 
 175 
 
 lion, arc those which took the least carbonic acid, and the 
 greatest quantity of water; a result in conformity with what 
 lias been stated in Chapter IV., in relation to the unequal 
 capacities of the powders of lime slaked spontaneously, and 
 by immersion, for carbonic acid. 
 
 (XXXII.) Vitruvius (Book 2, Chapter II.), and Pliny (Book 
 3o, Chapter XXIII.) speak of a light species of work which 
 the Romans called " Albaria Opera," and into which nothing 
 but lime entered. 
 
 Thevenot says (in his collection of reports), that in India 
 
 the application of moistened turmeric paper, of the more searching tests 
 described in the Note to Art. 82. 
 
 Extracts from the Analyses of various old Cements, showing the 
 quantities of lime and carbonic acid which they were found to contain. 
 
 Number of the 
 analysis in the 
 Tabic WI1. 
 
 Age of the ce- 
 ment analysed. 
 
 Weight of 
 lime. 
 
 Weight of car- 
 bonic nciil. 
 
 Proportion per cent. 
 which the quantity 
 
 of carbonic acid con- 
 tained in the cement 
 hears to the full sa- 
 turating dose. 
 
 
 Years. 
 
 
 
 
 14 
 
 1800 
 
 29.1 
 
 20.0 
 
 87.4 
 
 17 
 
 45 
 
 60.1 
 
 39.5 
 
 83.6 
 
 5 
 
 200 
 
 99.68 
 
 73.0 
 
 93.2 
 
 3 
 
 120 
 
 26. 
 
 17.0 
 
 83.2 
 
 (i 
 
 200 
 
 110.9 
 
 80.0 
 
 91.8 
 
 8 
 
 200 
 
 19.7 
 
 12.0 
 
 77.5 
 
 7 
 
 200 
 
 110.43 
 
 79.0 
 
 91.0 
 
 10 
 
 150 
 
 17.0 
 
 10.3 
 
 77.0 
 
 11 
 
 400 
 
 17.4 
 
 11.9 
 
 87.0 
 
 12 
 
 400 
 
 13.8 
 
 8.0 
 
 73.7 
 
 13 
 
 200 
 
 33.9 
 
 20.0 
 
 75.0 
 
 15 
 
 Recent. 
 
 17.1 
 
 10.0 
 
 74.4 
 
 1G 
 
 Ditto. 
 
 15.6 
 
 10.0 
 
 81.5 
 
 The analyses from which these extracts are made, will be found, at 
 length, in table No. XVII Tr. 
 
 Since writing the above, I have been kindly furnished by my 
 friend Dr. Malcolmson, with the results of some experiments upon the 
 mortar of the pyramid of Cheops, which is described in the Note to 
 Article 268. Thi> cement, though between three and four thousand 
 years old, and exhibiting to the most searching examination not the 
 slightest trace of causticity, yet in one analysis yielded only 5.64 carbonic 
 acid to 11 lime, in 100 grains, and in a second 4.53 carbonic acid to 9.6 
 lime in the same quantity. In the former case, the carbonic acid amounted 
 to 65.4, and in the latter to only 60 per cent, of the saturating dose. 
 These analyse*, which were conducted throughout with great care, and 
 
 *D 2 
 
176 APPENDIX. 
 
 they plaster the walls with a rough cast of quick lime slaked 
 in milk, aud beaten up with sugar, and that they afterwards 
 polish the mortar with an agate. The fact is, that they mix 
 the lime with a little curdled milk, with gingelli oil, and water 
 of jaghcry, a coarse very brown sugar, which is derived from 
 the cocoa tree. (Vide the letters of M. de Bruns, inserted at 
 the end of M. de Lafaye's memoirs 1 .) 
 
 most especially in reference to the separation of the carbonic acid and 
 lime, mav be fully depended upon. The particulars of the first of them 
 will be found in App. LXXII. 
 
 Some further remark- upon this subject will also be found in the Note 
 to Art. 309— Tb. 
 
 * The celebrated Madras chunam is a stucco laid on in three coats. 
 the first a common mixture of shell-lime, and sand, tempered with jaghery 
 water (vide Note to Art. 207.), and about half an inch thick ; the se- 
 cond of a finer description, made with sifted shell lime and white fine 
 sand, which is also sifted to free it from pebbles or foreign matter ; and 
 this coat, as well as the third, is applied without jaghery, which is omitted 
 on account of its colour, and its frequently containing deliquescent 
 salts. The third and last coat which receives the polish, is prepared with 
 great care ; the purest and whitest shells being selected for it, and none 
 but white sand of the finest description, and of that a very small proportion 
 is used, varying from one-fourth to one- sixth. The ingredients of the third 
 coat (as well as the second also, sometimes) are ground with a roller on a 
 granite bed to a perfectly smooth uniform paste, which should have the 
 feel and appearance of white cream. In about every bushel of this paste 
 are mixed the whites of ten or a dozen eggs, half a pound of ghee, (which 
 is butter separated from its caseous parts by melting over a slow fire,) and 
 a quart of tyre, (which is sour curd fresh prepared,) to which some add 
 powdered balapong (or soap-stone) from a quarter to half a pound, which 
 is said to improve the polish. But each master bricklayer has generally a 
 recipe of his own, which he boasts of as superior to all others. The 
 essential inTedients, in addition to the lime and sand, seem to be the 
 albumen (of the eggs), and the oily matter of the clarified butter, for which 
 oil is sometimes substituted. The last coat is laid on exceedingly thin, and 
 before the second is dry ; it dries speedily, and is afterwards rubbed with 
 the smooth surface of a piece of the soap-stone (steatite), or agate, to 
 produce the polish, an operation which is sometimes continued for many 
 hours, after which it is necessary to wipe it from time to time with a soft 
 napkin, to remove the water which continues to exude from it for a day or 
 two after completion. — Tr. 
 
APPENDIX. 177 
 
 NOTES ON CHAPTER VII. 
 
 (XXXIII.) The proprietors of the mills on the tributaries of 
 the Loire, between Nevers and Briare, and on the river Isle, 
 in the department of Dordogne, have for time immemorial 
 used, in repairing their works, a mortar composed of the rich 
 lime of the country, and a reddish, very argillaceous pit sand, 
 which they call arcne. This mortar hardens more or less in 
 the water, but it is sufficient for the preservation of the hy- 
 draulic masonry in which they use it. M. Girard, Engineer 
 of bridges and roads, and in charge of the works connected 
 with the navigation of the river Isle, being naturally struck 
 by so singular a fact, engaged in 1825 in some extremely in- 
 teresting researches regarding the properties of this kind of 
 sand. The sen-ice he was charged with afforded him oppor- 
 tunities of extending his experiments beyond the bounds 
 which confine the mere trials in the laboratory ; and the ob- 
 servations which he has made upon mortars of arene em- 
 ployed in large works, such as locks, wears, &c, &c, afford, 
 in consequence, as great a degree of certainty as could be 
 wished for. These observations, which we have eagerly 
 availed ourselves of, have given a place in the domain of 
 science and art henceforth to facts, which, however well they 
 might have been known to the millers of the Isle and others, 
 were not the less hidden and lost to builders. 
 
 (XXXIV.) The hydraulic properties of the brown schistose 
 psammites, (grey-wackes of the Germans,) when used in their 
 natural state with rich lime, were discovered in 1824 by M. 
 Avril, the Engineer, when charged with the superintendence 
 of a division of the canal from Nantes to Brest, in the depart- 
 ment of Finisterre. " In studying the varieties of schist 
 which compose the soil of our neighbourhood," says this 
 Engineer, (Memoir on the Navigation of the Kergoat, written 
 1st October, 1824,) " chance threw in my way an arenaceous 
 rock of a yellowish red colour, in a state of decomposition, 
 
178 APPENDIX. 
 
 the action of which, when used as sand in its natural Btate, 
 and as a cement, after a calcination of ten hours in a lime- 
 kiln, seemed to promise a solution of the problem which 1 
 had undertaken. This rock belongs to the species of 
 sandstone called grev-wackes by the Germans, and psam- 
 mites by M. Brogniard ; it is so soft as to fall to powder be- 
 tween the fingers; it hardens in the air and the fire, a cir- 
 cumstance which enables us to build it up into vaults, in the 
 same way as lime, to burn it," &C 
 
 The conversion of the schistose psammites into pouzzolanas 
 by a gentle calcination, is by no means a new phenomenon 
 in the science of mortars, for these substances being est 
 tially composed of silica, alumina, and oxide of iron, form, in 
 some measure, the transition of the schistose rocks into clays, 
 and even seem to differ from these merely in having a lighter 
 contexture, and by the faces of mica which their fracture 
 exhibits. But what truly constitutes a new fact, (and which 
 sooner or later must have led to the discovery of the analogous 
 properties of the arenes,) is the circumstance, that in their 
 natural state they act as pouzzolanas with rich lime ; this 
 action it is true is slow, and very variable in its intensity, but 
 it does take place. 
 
 (XXXV.) Pouzzolana was in extensive use amongst the 
 Romans-. The following is what Yitruvius says of it: — 
 
 9 No particular account being here given of the use of Dutch Tarras, I 
 have extracted and thrown together the following notice- of it from Mr. 
 Bmeaton's valuable Essay on Water Cements, in hi> w<nk on the Eddy. 
 Stone Lighthouse. — " I fbtind it in lumps of various sizes, from the 
 
 bignes- of a pea to that of a middle used turnip : it is of a light greyish, 
 or ash colour, is rather tender than hard, and is very porous, somewhat 
 resembling a pumice stone. There seema t«> be nothing calcareous in its 
 composition, for aquafortis dropped upon it only wets it like water: to 
 me it much resembles some petrifactions that 1 have Been | but my more 
 
 learned friends seem to be of opinion that it is a lava 
 
 Although really endowed with those qualities, which have justlj obtained 
 it a reputation for water building, yet it is generally admitted to have some 
 properties, that for our use were not quite so eligible. In the tir.-t place, 
 though it will coi. mpsl kinds of lim^ to set and become hard under 
 •. u w< have -m h\ b) vrral example .-, yet if the cement grows diy 
 
APPENDIX. 17i) 
 
 " There is found in the neighbourhood of Baye, and the mu- 
 nicipal lands lying at the foot of Vesuvius, a kind of powder 
 which produces admirable effects; when mixed with lime 
 and small stones, it has not only the advantage of giving 
 great solidity to common buildings, but possesses the further 
 property of forming masses of masonry, which harden under 
 water. We may account for this property by the great num- 
 ber of burning soils, and hot springs, which give evidence of 
 an extensive subterraneous fire, occasioned by the inflam- 
 mation of sulphur, alum, or bitumen. Tims the vapour of 
 the fire and the flame passing constantly through these beds 
 of earth renders them light, and converts them into a withered 
 tufa without moisture, so that these three substances (the 
 lime, the stones, and the pouzzolana) modified by the violence 
 of the heat, on being mixed together, form a solid substance 
 as soon as we add water. This mixture quickly acquires so 
 great hardness from the damp which it absorbs, that neither 
 the dashing of waves, nor the action of water, are able to 
 destroy it." 
 
 For want of pouzzolana, the Romans made use of pounded 
 brick, which we call cement. 
 
 (XXXVI.) Count Chaptal was the first who remarked the 
 unequal manner in which certain of the pouzzolanas of Italy 
 
 by a gradual exposure to the air, it never sets into a substance so hard as 
 if the same lime bad been mixed with good clean common sand ; but is 
 very friable and crumbly ; and if, after it has acquired a considerable de- 
 gree of bardness by immersion in water, it is then exposed to the air, it 
 loses a considerable part of its firmness, and also becomes crumbly ; 
 though according to my observation, it never becomes so much so, as if 
 it never had acquired a greater hardness by a submersion in water. . . . 
 In a state between wet and dry, or of being wet and dry by intervals, 
 
 Tanas is known not to answer well Another property of Tarras 
 
 mortar is, that when kept always wet, and consequently in a state most 
 favourable to its cementing principle, it throws out a substance something 
 like the stony concrescences in caverns of lime-stone strata, called stalac- 
 tites ; which substance from the Tarras comes to a considerable degree of 
 hardness, and in time becomes so extubcrant as to deform the face of the 
 walls ; and when smoothness and regularity of surface is wanted, as in 
 navigable sluices, mill conduits, &c, it becomes necessary to remove itfi 
 
180 IPMtHDiX. 
 
 and Vivarais behave with sulphuric acid ; without deducing 
 therefrom any conclusion with respect to the energy of these 
 substances. The observations which have, in a general man- 
 ner, established the relations between the qualities of the in- 
 gredients of calcareous cements, and their mode of action in 
 ct to acids and lime-water, are entirely our own. They 
 were published by fragments in the different numbers of the 
 " Annales de Chunk et de Physique," from 1819 to 1826. 
 Till that time it was the general opinion of chemists, that 
 clays were more easily acted upon by acids when in their 
 natural state, than after any degree of calcination ; a mistake 
 the more fatal, inasmuch as it rendered the supposition of a 
 chemical action taking place, in the phenomenon of the 
 solidification of calcareous cements, altogether improbable. 
 
 If. Berthier (in the Journal des Mines, vol. viii. p. 356), 
 has endeavoured to show, in conformity with the opinion of 
 Proust, that the oxide of iron is merely interposed in the 
 ochres, and not in combination with the silica, as Berzelius 
 has stated. This accounts for the facility with which some 
 of the ochreous clays are decolori*ed by the muriatic and 
 nitric acids. 
 
 (XXX VI I.) It was Mr. John, of Berlin, who first pointed 
 out the impotency of the most caustic lime on quartz. This 
 able chemist having, in fact, kept a dozen bits of garnet in 
 
 roughness by tools ; for otherwise the Tarras mortar will grow so much 
 in the joints of these conduits, as to knock off the floats or ladle-boards 
 from the wheels A composition of this kind (2 lime, 1 Tar- 
 ras, 1 sand), is further increased in bulk, by another measure of sand ; 
 so that one cube foot or measure of the common Tarras mortar composi- 
 tion will by this means become two, and quite as good in every respect. 
 Finding this idea so far to answer, not only in experiment, but my expect- 
 ations satisfied in works at large, I was induced to try whether lime 
 would not bear a saill greater addition of sand ; and I soon found that it 
 would, with good beating, take iD, for every two measures of slaked 
 lime, one measure of Tarras, and three of tK-.m -and ; which would pro- 
 duce nearly 3i measures of good water mortar, or full 2£ times the com- 
 mon quantity of mortar from the same quantity of Tarras and lime ; this 
 being near upon four times the bulk in solid mortar of the utujuenched 
 Jimc, or the unburnt stone." — Tr. 
 
APPENDIX. 181 
 
 decoction for eight hours in a fluid pulp made from Carrara 
 marble, these minerals did not lose in it a single atom of their 
 weight ; the same was the case with two bits of rock crystal, 
 left for six months in the same fluid. 
 
 We have on our part established, as follows, the absence of 
 chemical action by the hydraulic limes upon various kinds 
 of sand. 
 
 A certain quantity of white, and entirely quartzose pit 
 sand, was digested in muriatic acid, then washed in much 
 water, and dried at the temperature of boiling water, Parts 
 and weighed 896.000 
 
 On the other hand, we took hydraulic lime, in its 
 quick state, fresh from the kiln 300 
 
 These substances were made into mortar in the 
 ordinary way in a glass vessel, which weighed 787 
 parts, and altogether the whole came to 2620, whence 
 it follows that they had taken a quantity of water 
 represented by . . 647.00 
 
 Thus the whole weight of the fresh mortar No. Awas 1843.00 
 
 A granitic sand mingled with basalt, prepared in 
 the preceding manner, weighed .... 896.000 
 
 Lime as before 300.000 
 
 Water absorbed under the same circumstances as 
 above 612.500 
 
 Total weight of the mortar No. B . 1808.500 
 
 These two mortars, when placed in the circumstances most 
 favourable to a chemical action between their component 
 piinciples, each lost, in fifteen months, 27 per cent, of their 
 weight. Two years after their manufacture, both one and 
 other of them were disaggregated by muriatic acid. The 
 sand of No. A, being separated, washed, and dried, weighed 
 when cool, 892.000 parts. The loss was then only irjj or 
 ToVo o 5 it W evidently to be attributed to the second wash- 
 
182 Al'PENDIX. 
 
 ing, The sand ol* No. B, treated in the .same way, only 
 weighed 883, which gives a loss of -fa. We took 500 parts 
 of this same sand, and digested them in muriatic acid ; and 
 as there was a disengagement of heat during the disaggrega- 
 tion, we took care to raise the temperature of the acid in the 
 counter-proof in an equal degree, and to continue its action 
 during the same time. The sand, when washed, dried, and 
 weighed as before, gave a deficit of 7 out of the 500, or -?!• 
 This result, which differs but slightly from -£g, leaves no doubt 
 regarding the cause of the loss exhibited by the sand mixed 
 with basalt ; and we may conclude from the above experi- 
 ments, that the hydraulic lime has no more action on the 
 granitic and basaltic sands, than on those which are purely 
 quarlzose. 
 
 NOTES ON CHArTEK VIII. 
 
 (XXXVIII.) Tile-dust, which has been used in buildings 
 for time immemorial, is evidently, according to our defini- 
 tions, the most ancient of the artificial pouzzobnias known ; 
 but the products to which that tenn was specially applied, 
 previous to the publication of our first researches, do not date 
 farther back than the middle of the 18th century ; at which 
 period a Swedish engineer, Bagge of Gothembourg, despair- 
 ing to obtain the pouzzolanas of Italy for the hydraulic con- 
 structions which he was superintending, at a sufficiently 
 moderate ] trice, thought of imitating them by calcining the 
 Compact schists, which arc found in abundance in Sweden, 
 near Wcnesborg. 
 
 Count Chaptal, to whom science and the arts are so largely 
 indebted, soon after (1787), made known his experiments 
 upon the calcination of the ochreous clays of Langucdoc, and 
 showed, that when properly chosen and prepared, these sub- 
 stances acted precisely in the same manner as the pouzzo- 
 lanas of Italy. But it was in the number and respective 
 proportion* of their principles, that this celebrated chemist 
 endeavoured to find the cause <>f the phenomena. The con- 
 
APPSNDDL 1^3 
 
 sequences of tbe important observation contained in Appi 
 XXXVI. escaped him. 
 
 (XXXIX.) The hydraulic virtues of the pouzzolanas, have 
 for a long time been attributed to the presence of iron : our 
 experiments upon the non-ferruginous clays have caused us 
 to abandon that opinion. We should be wrong, however, to 
 conclude, that in the red coloured pouzzolanas, the iron is 
 entirely inert ; one thing, however, is certain, that is, that its 
 presence is by no means indispensable, since there are very 
 energetic pouzzolanas which do not contain an atom of it z . 
 
 (XL.) Colonel Raucourt of Charleville, the Engineer, to 
 whom, a few days before his departure for Russia, we com- 
 municated the singular properties which clays acquired, when 
 calcined in powder on metallic plates heated to redness, was 
 eager to repeat our experiments in Russia; but he has 
 thought, that the slight degree of calcination which the clay 
 undergoes by this means, was not the sole cause of the phe- 
 nomenon ; the contact of the air appeared to him to exert a 
 notable influence ; and this suspicion was changed into as- 
 surance, by a series of direct experiments, which led him also 
 to examine the effects of the contact of the air on the burning 
 of artificial hydraulic limes. (See pages 130 and 13], of his 
 treatise on mortars.) The conclusions which he has drawn 
 from the whole of his experiments are, (vide p. 136, of the 
 same treatise,) that there is an absorption of oxygen ; he 
 again expresses himself very clearly to that purpose, in the 
 note placed at the foot of page 161. But such an opinion 
 not to be mere conjecture, has need of the support of direct 
 experiments ; for it is by no means evident, that such is a 
 necessary consequence of the favourable influence of the con- 
 tact of the air on the conversion of clays into good pouzzo- 
 lanas. Whilst engaged with the researches of which this 
 
 " My experiments also tend to establish the authors opinion on tins 
 point, both d.reetly and indirectly, as I have met with elav entirely free 
 from iron, which after calcination formed a highly energetic pouzzolam. 
 and on the other hand, a stiff paste prepared for experiment of rich slaked 
 lime and the washed colcothar of vitriol, (peroxide of iron,) was perfceth 
 •I' .Wtcr seven weeks' immersion Tk. 
 
184 
 
 \mMiix. 
 
 chapter contains a summary, we studied the action of lime in 
 the humid way on silica and alumina, when isolated, and 
 taken in various states of cohesion. Mixtures made in the 
 proportions (by bulk) of 200 parts of these oxides, to 100 of 
 rich lime in paste, gave, after three months of immersion, the 
 following relative resistances under the shock of the experi- 
 mental needle. (Vide the statement of the manner in which 
 the experiments were made, at the end of this volume.) 
 
 Depth of penetration of 
 the needle. 
 
 1st. With the mixtures of the hydrate inche* r 
 
 of rich lime, and gelatinous silica, simply ; 
 
 dried in the air 1-70 0.0704723 
 
 2d. The same, with the silica calcined 
 to redness 2.50 0.098425 
 
 3d. The same, with the silica separated 
 from various clays by boiling sulphuric 
 acid 2.85 0.1122045 
 
 4th. The same, with silica separated 
 from these clays, after they had been 
 slightly calcined 4.16 0.1637792 
 
 5th. The same, with silica in an alto- 
 gether impalpable powder, taken from 
 hyalite, by trituration, and successive 
 
 washings Indefinite. 
 
 6th. The mixtures of the hydrate of 
 lime, and alumina in a gelatinous state, 
 and slightly dried in the air .... 18.17 0.7153 
 
 7th. The same, with the alumina slightly 
 calcined 12.86 0.504298 
 
 8th. The same, with the alumina strongly 
 
 calcined Indefinite. 
 
 These experiments prove, that silica may form a good hy- 
 draulic cement with rich lime, without being soluble in 
 at ids. It suffices for this purpose, that its cohesion be very 
 much less than that it is possessed of in quartz. 
 
APPENDIX. 183 
 
 We see further, that the hardness of the cement is th ! 
 greater, the more nearly the silica approaches the gelatinous 
 state, in which condition it is obtained by the aid of chemical 
 agents. 
 
 With regard to alumina, we sec, that even in the gela- 
 tinous state, although it gives rise to an insoluble compound, 
 yet that it produces a substance which, if not soft, is of a very 
 indifferent consistency ; we have moreover ascertained, that 
 the peroxide, and carbonate of iron, display no action what- 
 ever under the same circumstances. 
 
 It is impossible to avoid recognising the effect of a che- 
 mical combination in the cases Xo. 1 and Xo. 6 a ; and this 
 ought not to surprise us, since it is known, that the solutions 
 of baryta, strontia, and lime, &c, decompose those of 
 alumina and silica in potash, and that the precipitates are 
 binary compounds, of alumina, and of silica, with one of the 
 substances above named. 
 
 These curious facts, for which we are indebted to the 
 celebrated Guyton Morveau, have been since confirmed by 
 Professor d'Obereiner and by John of Berlin. It evidently 
 follows from case Xo. 6, that a firm solidification is not a 
 necessary consequence of the chemical combination of two soft 
 or pasty substances, brought in contact in the humid way. 
 
 With regard to Xos. 2, 3, 4, and 5, although analogy 
 
 1 1 have found this observation to be fully confirmed, when applied to 
 certain artificial pouzzolanas mixed with slaked rich lime ; (vide Note to 
 Art. 314,) but the explanation cannot be extended so as to embrace all 
 cases of the set of hydraulic limes ; (vide Note to Art. 307.) I may 
 here, however, notice an experiment made by General Trcussart, which 
 appears to bear additional evidence in favour of the conclusions contained 
 in the text : he says, " In mixing common (not hydraulic) lime in paste 
 and clay together, I met with a singular phenomenon, which I am unable 
 to account for. It is, that if you diffuse clay in water, so as to bring it 
 to the consistency of thin pulp, and after bringing the lime to the 
 same condition, mix the two ; no sooner is the union effected, than the 
 compound becomes so stiff, that it is difficult to continue the operation 
 without adding a further considerable quantity of water." This seems to 
 indicate a new arrangement of the particles, consequent upon chemical 
 affinity. — Tr. 
 
186 APPENDIX 
 
 would had us t<» look upon them also as combinations, yet 
 when we take into consideration the state of cohesion of tin.' 
 silica employed, and the known absence of action of the 
 hydrate of rich lime upon quartz, we ought not to affirm such 
 
 to be the case. We may nevertheless remark, that it is not 
 correct to compare silica, such as it is in quartz, to such as 
 has just been separated from combination ; the first in fact 
 is only acted on by soda or potash with heat, whilst the 
 other readily dissolves in them in the cold, a fact which leads 
 us to presume, with some probability, that lime is not devoid 
 of action upon it. 
 
 Nos. 1 and -2, which exhibit as much hardness as the best 
 hydraulic cements, lose all their cohesion by an exposure to 
 the air more or less prolonged. 
 
 (XL I.) It has been proposed to make use of the revcrbe- 
 ratory fumace b ; but the powder of the clay, owing to the 
 water which it contains latent within it, undergoes an ebul- 
 lition the moment it touches the incandescent surface, and 
 this raises and dissipates it in clouds ; besides, it is no easy 
 
 b Colonel Raucourt de Charleville describes an air furnace for this 
 purpose, the chimney of which instead of being vertical is curved semi- 
 circularlv, the lower end of it being horizontal, and the upper perpen- 
 dicular, and occupied throughout its entire length by a covered trough of 
 sheet iron, one foot and a half broad, and six inches deep, passing down the 
 middle of it. The lower end of this trough crosses the fire of the fur- 
 nace, and is exposed to its full force ; and the upper end terminates at 
 the top of the chimney, in a hopper filled with the powder to be calcined. 
 The flame and heated air in their passage up the chimney, impart their 
 heat to this trough, which is closed on all sides; and the lower end, being 
 in contact with the fire, is kept constantly of a full red heat. When 
 sufficiently burned, the powder i-; removed by small portions from the lower 
 end of the trough, by a door for the purpose; while the contents of the 
 upper part descend and take its place. This door has apertures left in 
 it to admit of a draft of air up the interior, and which acts upon the 
 thin layer of powder lying on the floor of the trough. In another fur- 
 nace of this kind, the chimney is bent like an elbow, not curved, the part 
 next the fire being nearly horizontal, and the rest vertical ; the first con- 
 tains two troughs like that above described, one above the other, and the 
 vertical part of the chimney is entirely filled with the material. Both 
 these possess the advantage of heating the powder very gradually, by 
 which the difficulties alluded to in the text are avoided — Tr. 
 
APPENDIX. 187 
 
 matter to reduce crude clay to line powder; we know, that 
 however dry it may be, tins substance adheres to the bruising 
 tools, and clogs underneath the stamper. 
 
 (XLII.) M. Bruyere, Inspector-general of bridges and 
 roads, has bestowed much pains upon the conversion of 
 clays into artificial pouzzolanas; his attention was prin- 
 cipally turned to the method of giving these materials that 
 degree of porosity, necessary for them to be quite equably 
 acted on in all their parts by a moderate heat : he employed 
 successively as ingredients for dividing them, lime, sand, 
 and various vegetable substances. The results which he 
 obtained, give us cause for serious regret, that he has not 
 made them known by publication. If. Saint Leger has re- 
 peated most of M. Bruyere's experiments in the large way. 
 He found, that a mixture of three parts of clay in powder, 
 with one part of rich lime in paste, was that which we ought 
 to give the preference to ; and in this he is in perfect accord- 
 ance with the intelligent Inspector-general. The artificial 
 pouzzolanas which are formed by a slight calcination of clay 
 mixed with lime, afford very active cements, which set in a 
 few hours ; but it is proper to add, that these same cements do 
 not finally reach more than a moderate degree of hardness, 
 they are besides very dear. 
 
 (XLIII.) We procured a very fine plastic clay, brought from 
 the environs of Loupiac, (Lot,) and containing in 100 parts, 
 61 of silica, 31 of alumina, an inappreciable trace of the 
 oxide of iron, and 8 of water. This clay, being pulverized 
 and passed through a hair sieve, and equal portions of it 
 put into hessian crucibles with covers let in, (and the joints 
 carefully filled in with a luting of sand and refractory clay,) 
 was in that state subjected to a good incandescence, for 
 about half an hour, in the middle of a small dome furnace. 
 The powders were always cooled in the closed vessels, and 
 100 parts gave by weight- 
 In the first experiment . 88.71 1 ,.,.,, 
 ... I of which the 
 
 mean is 88.543. 
 
 the first experiment . 88.71 "j 
 In a second ditto . 88.32 y 
 In a third ditto . . 80.60 J 
 
UPPENDIX. 
 
 Anotlier portion of the same clay, equally wrll pulverised 
 end sifted, having been calcined at a common red heat, on an 
 incandescent metallic plate, and for 5 minutes, gave for 
 100 parts — 
 
 In a first experiment . 89.85 ) of which the 
 
 second ditto . . 80.80 j mean is 89.825. 
 
 A second portion, calcined in the same manner, but during 
 15 minutes, gave for 100 parts. 
 
 First experiment . 88.50 ) of which the 
 Second ditto . . B8.63 j mean is 8^.575. 
 
 A third portion, calcined as before, but during 30 minutes, 
 gave for 100 parts, 
 
 First experiment 88.45 ) the mean of 
 Second ditto . . 88.55 j which is 88.50. 
 
 The very trifling difference which we observe between the 
 weight of the clay when calcined in the close vessel, aud 
 that of the clay calcined in the open air, prove incontestibly 
 that there is no kind of absorption. These differences may 
 be accounted for; first, by an inequality in the duration and 
 intensity of the heats ; second, by the slight losses inse- 
 parable from a calcination in the open air, more especially 
 when we are obliged to stir the substance. To what then 
 is the real and notable difference in the binding qualities of 
 the clav, as subjected to these two kinds of calcination, to be 
 attributed ? We should in vain endeavour to explain this. 
 
 At any rate, by calcination in a closed vessel, the clay i^ 
 unable to acquire the faculty of yielding to acids the same 
 quantity of alumina, as in the case of the ordinary calcina- 
 tion. The difference amounts to more than half. One part of 
 the above plastic clay, being first calcined in a close vessel. 
 and then, after eight days' exposure to the air, calcined 
 again in an open crucible, lost T oTo °f i* 8 weight. 
 
 One part of the same clay, being first calcined in the open 
 air, and then treated in the same manner as the above, lost 
 yott °f i ts weight. 
 
 From this comparison it results incontestibly, that clays 
 calcined in contact with the air. possess after cooling an 
 
APPFADIX. 
 
 13!) 
 
 absorbent property ; which the same, when calcined in a close 
 vessel do not. 
 
 But in what does this absorption consist ? Is it simply 
 hygromelric ? This it is impossible for us to decide. The 
 following, moreover, is a complete series of facts, observed 
 in reference to cements prepared from two kinds of clay, 
 calcined according to the two methods now in question. 
 
 
 Time of 
 setting. 
 
 Hardness, as measured hy 
 the fall of the needle, after 
 
 | J ~ '- c 
 
 Observations. 
 
 Five months' One year of 
 immersion, inmiersion. 
 
 1. 
 
 White clav, marked 2, in 
 Table No. III., and cal- 
 cined in powder in the 
 
 Rich lime in paste. .. . 2.im 
 
 • 
 
 The same clay calcined in 
 
 .s. 
 
 An ochreous clav, marked 
 No. l.in T..bl'e III..C.-.1- 
 cined in powder in the 
 
 Rich lime in paste .. &00 
 
 1. 
 
 The same calcined in a 
 
 close vessel 3.01 
 
 Rich lime as before. . lA 
 
 Days. 
 1 1.50 
 
 h 50 
 j 
 
 J7-00 
 
 3.2.i mill. 
 0.1279 in. 
 
 .i.immill. 
 0.19585 in. 
 
 3.00 mill. 
 0.H81] in. 
 
 4.(«i mill. 
 0.1575 in. 
 
 2.50 mill. 
 0.0984 in. 
 
 2.00 mill. 
 0.07874 in. 
 
 ■2.t 10 mill. 
 0.7874 in. 
 
 1.7" mill. 
 0.0669 in. 
 
 3.40 mill. 
 0.1338 in. 
 
 100 mill. 
 0.11811 in. 
 
 2.iximill. 
 
 mow in. 
 
 1.80 mill. 
 0.07086 in. 
 
 The cements were tried 
 by the needle.at five 
 or six millemetres 
 (.196 in. or .23»J in., 
 Tr.) below the sur- 
 face, and by the 
 piercer, in the centre. 
 
 With a spring saw, 
 they gave a nearly- 
 dry powder. 
 
 Vumbers 1 and 3 were 
 hard superficially, 
 and did not at all 
 adhere to the sides 
 of the vessels con- 
 taining them ; Nos. 
 2 and 4 werj dete- 
 riorated at the sur- 
 face, to the depth 
 of six millemetres 
 (0.236 in., Tr.), and 
 adhered powerfully 
 to the sides of the 
 vessels. 
 
 (XLIY.) Is it to the presence of the potash, or the de- 
 gree of calcination only, that the aquafortis clay owes its 
 binding properties r In 1818, we subjected to the action of 
 heat some small bricks, composed of clay moistened with 
 solutions of the sub-carbonate of potash, containing from 
 1 to 15 per cent, of the salt, and could observe no relation 
 between the energy of the products obtained, and the 
 quantities of the alkaline oxides introduced ; but on re- 
 flecting on it since, it has occurred to us, that by calcining 
 the clay in the form of bricks, it was possible that, from the 
 sudden action of the heat which that mode of calcination 
 requires, the potash may have acted witli too great intensity, 
 and at last entangled the principles of the substance, by an in- 
 
UK) 
 
 APPENDIX. 
 
 cipient vitrification w bictaj although imperceptible, might be no 
 less sufficiently decided, to destroy all the binding property 
 
 We in consequence recommenced our experiments, as fol- 
 low b. A hundred parts of a red effervescing clay, (containing 
 silica 42.60, alumina 15.90, oxide of iron 8.00, carbonate of 
 lime 24.0-1, water 8.80) were moistened in a solution of 
 caustic soda, containing ten parts of saturated fluid; thej 
 u rre then dried, and brought to the state of powder, and 
 afterwards calcined at a red heat in contact with the air. 
 A hundred parts of slate, previously calcined in powder in 
 contact with the air, and which in that state afforded only 
 a pouzzolana eery nearly inert, were moistened with the same 
 quantity of the soda solution, then dried again, and calcined 
 in the same manner as the clay above mentioned. 
 
 Thus prepared, the two pouzzolanas were mixed of a good 
 consistency, with rich lime in paste, obtained by the ordi- 
 nary extinction, and the products were immersed without 
 delay. The phenomena which accompanied this immersion 
 arc exhibited in the following table. 
 
 COMPOSITION or THE I'KMKNTS. 
 
 Time of Set. 
 
 I ) under the blow 
 
 nf the trial neetlle, after 
 seven months' iinnier- 
 
 Ricb lime in paste, obtained by 
 
 the ordinary mode of extinction 100 
 Pouzzolana, resulting from a 
 
 simple calcination of the red 
 rlay in powder . . . .200 
 
 Rich lime as before . . . 100 
 
 Pouzzolana, resulting from a cal- 
 cination of the aforesaid clay 
 impregnated with soda . . 200 
 
 Rich lime as above . • .100 
 Pouzzolana, resulting from a 
 simple calcination of the pow- 
 dered slate 200 
 
 Rich lime as above . . .100 
 Pouzzolana, resulting from a se- 
 cond calcination of the said 
 slate, when impregnated with 
 soda --ii»" 
 
 y i.oo 
 J 
 
 1.00 
 
 U20.00 j 
 
 coo 
 
 3.00 (0.118 in.. TV.) 
 
 1.75 0.0689 in., Tr.) 
 
 12,26 ,o.»s-2G76 in. 
 Tr.) 
 
 8.0 (0.3 loin., Tr.) 
 
APPENDIX. 191 
 
 (XLV.) — * A patent I recently taken out by Mr. R. F. 
 
 Martin, and a company established for the manufacture of 
 a newly discovered cement, prepared by calcining bricks 
 composed of powdered gypsum, and the solution of the sul- 
 phate of potash (prepared by neutralising the alkali bv the 
 acid). The bricks are pulverised, after calcination at a red 
 heat, and the cement thus formed is applied in the way of 
 common stucco. It sets in about two hours, and some 
 specimens which Mr. Martin had the kindness to exhibit 
 to me, were of extreme hardness. As the material itself is 
 of a pure white, it is admirably adapted as a vehicle for 
 colours, and for the imitation of marbles and various descrip- 
 tions of ornamental work, some of which are very beautiful. 
 The cement is said to be quite uninjured by frost, and to 
 be capable of enduring exposure to the weather without 
 damage, for any length of time. — Tr. 
 
 NOTES ON CHAPTER IX. 
 
 (XLYI.) The reciprocal suitabilities of the ingredients of 
 mortars and calcined cements were laid down in a general 
 way, and for the first time, in the work which we published 
 in 1818. The law which regulates these compatibilities has 
 been since verified by a great number of Engineers, amongst 
 whom we may name Colonel Raucourt, of Charleville. The 
 treatise which he has printed, regarding the various kinds of 
 lime employed in Russia, and on mortars in general, con- 
 tains, besides, many interesting facts, of which we have 
 availed ourselves. 
 
 We are now-a-days enabled to explain the contradictions 
 exhibited by different memoirs relatiug to mortars and pouz- 
 zolanas ; contradictions, which made the collection of facts 
 known up to 1818 a real labyrinth, the clew of which had 
 escaped the search of the most judicious investigations. 
 
19'2 AFPBHDOL 
 
 First example. The experiments made in L786 at tin 
 
 harbour of Cette, by the commissioners of the States of Lan- 
 guedoc, on the occasion of Count Chaptal's researches into 
 artificial pouzzolanas, established in an authentic manner, 
 that the pouzzolanas of Vivarais were very inferior to those 
 of Italy; and yet we find in the supplement to the first me- 
 moir on pouzzolanas, by Faujas de St. Fond, experiments also 
 made with great care, and which demonstrate precisely the 
 contrary. This is because, on the one hand, they used an 
 eminently hydraulic lime, (the lime of Montelimart), and on 
 the other, the rich lime of the environs of Cette. Now the 
 eminently hydraulic lime, when used with the very energetic 
 pouzzolanas of Italy, must, in fact, have afforded to Faujas, 
 results infeiior to those which he obtained at the same time 
 from a feeble pouzzolana mixed with the same lime. 
 
 Second instance. The slaty schists, which were in 1807 
 advertised by G. Lepere, the Engineer, as substances capable 
 of conversion by a powerful calcination, into pouzzolanas 
 equal to those of Italy, deceived all the builders who wished 
 to apply them to use. This was because the trial betons upon 
 which that Engineer rested his comparisons, were made with 
 the hydraulic lime of Grossville, and that lime, in fact, was 
 adapted to a very slightly energetic pouzzolana, which ceased 
 to be the case when rich lime was made use of. 
 
 Third instance. The military Engineers employed upon 
 the works of Alexandria (in Piedmont), being ill satisfied 
 with the induration of the beton prepared with the Casal lime 
 and the powder of bricks once burnt, thought of calcining 
 the powder violently in a reverberatory furnace, and they 
 thus obtained better results than before; this was because, 
 by giving a high degree of calcination to their artificial 
 pouzzolana, they changed it into a pouzzolana of feeble 
 energy, which in that state suited the lime of Casal very well, 
 as it is hydraulic. 
 
 It would be tedious to enumerate in this place all the mis- 
 takes into which our predecessors have been led, by their un- 
 certainty in regard to the mutual adaptation of the ingredients 
 
APPENDIX. 
 
 19:1 
 
 of calcareous mortars and cements. We must believe that 
 Vitruvius, in making the qualities of lime to reside in its 
 whiteness and expansion by slaking, merely viewed that 
 substance in reference to its mixture with the excellent pouz- 
 zolanas of the environs of Rome, and not with pure quart- 
 zose or calcareous sands. Now, all who have written after him 
 have not failed to repeat, in an absolute way, that the hardest 
 and purest marbles furnish the best lime. 
 
 (XLVII.) A Table containing Twenty Compositions of Water Mortar, 
 suited to different situations and circumstances. Extracted from 
 Smeaton's essay on water cements. Narrative of the Construction of 
 the JEddi/stone Lighthouse. 
 
 WATER LIME WITH Lime now-! Pouzzolana 
 POUZZOLANA. der. •""«"»» 
 
 Eddystone mortar . . . 
 
 Stone mortar 
 
 2nd sort. 
 
 Face mortar 
 
 2nd sort , 
 
 Backing mortar 
 
 Bushels. 
 2 
 
 WATER LIME WITH 
 MINION. 
 
 Face mortar 
 
 Calder com- 
 position 
 
 Backing mortar .... 
 2nd sort 
 
 COMMON LIME WITH 
 T ARRAS. 
 
 H Tarras mortar 
 
 12 increased. . 
 
 13 further. . . . 
 
 M still further 
 
 15 Tarras backing mortar. 
 
 16 
 
 2nd sort 
 
 COMMON LIME WITH 
 
 MINION. 
 
 17 Ordinary face mortar . . 
 
 1 8 2nd sort . . 
 
 19 Ordinary backing mor- 
 
 tar 
 
 20 ! 2nd sort. . . I 
 
 Bushels. 
 2 
 1 
 1 
 1 
 i 
 
 Minion. 
 
 i 
 
 Common 
 
 No. of 
 
 Expense pr. 
 
 sand. 
 
 cubic feet. 
 
 cubic foot. 
 
 Bushels. 
 
 
 *. rf. 
 
 
 
 2.32 
 
 3 8 
 
 1 
 
 2.68 
 
 2 14 
 
 2 
 
 3.57 
 
 i n 
 
 3 
 
 4.67 
 
 1 4 
 
 3 
 
 4.17 
 
 1 1 
 
 3 
 
 4.04 
 
 . ... 
 
 11 
 
 1 
 
 3.22 
 
 1 5i 
 
 2 
 
 3.57 
 
 1 1 
 
 3 
 
 4.17 
 
 10 
 
 3 
 
 4.04 
 
 9J 
 
 
 
 1.67 
 
 4 
 
 1 
 
 2.50 
 
 2 9 
 
 2 
 
 3.45 
 
 2 04 
 
 3 
 
 4.35 
 
 1 8 
 
 3 
 
 3.50 
 
 i H 
 
 3 
 
 3.37 
 
 o n* 
 
 
 
 2 
 
 4.75 
 
 1 5. 1 , 
 
 3 
 
 4.34 
 
 8| 
 
 3 
 
 4.05 
 
 8 
 
 3 
 
 3.92 
 
 o n 
 
 The materials in the above mixtures were measured dry. The lime in 
 powder thrown into the bushel and striked, but Dot beaten nor pressed 
 
 down. 
 
194 UTI.M'IV 
 
 NOTKS ON CHAPTER X. 
 
 (XLVI1I.) We confined ourselves in Chapter I. to a simple 
 definition, in what relates to " poor limes," and we have 
 since forborne to speak of them for a very simple reason, viz., 
 because they are very rarely employed, and because we are 
 right in so doing: for, to the want of expansion of the hy- 
 draulic limes, they add all the negative qualities of rich lime. 
 When, however, they are not absolutely devoid of hydraulic- 
 qualities, we may venture to use them, for want of others. 
 In that case, it is evident that we ought to modify, in respect 
 to them, what we have said regarding proportions ; inasmuch 
 as in an equal bulk, these limes actually contain a larger 
 quantity of the earthy or metallic oxides, than the slightly 
 hydraulic limes to which they are assimilated. Thus, M. de 
 Laroche, Engineer of roads and bridges, in the experiments 
 which he made at Brest, with a " poor lime" very slightly hy- 
 draulic, found, that the precept " it is better to err by defect 
 than excess of lime" was not confirmed; because in fact, that 
 precept is applicable only to the rich, and slightly hydraulic 
 limes. 
 
 (XLIX.) This great question of the best method of slaking, 
 has been for a long time agitated amongst builders. It is 
 not astonishing that it has been decided by some in favour of 
 immersion, and by others in favour of the ordinary pic 
 Kvery one made use of the materials which fell to hand, 
 without even suspecting, that the result which followed 
 from any one such experiment, wa*s applicable only with ex- 
 actness, and rigorously, to these same materials, l'aujas, alone. 
 seems to have caught a glimpse of the fact, that lime, ac- 
 cording to its nature, yields in preference to one kind ol 
 extinction rather than another; for he says, in a note of bis 
 memoir, speaking of immersion, " When we are in a sitae 
 tion to use an excellent quick lime," (we imagine thai 
 i»\ quick lime, the author intended to denote an h\ 
 
UM'KNPIX. 10") 
 
 dranlic lime,) u we may dispense with M. Lafaye'a method; 
 but whensoever we are compelled to use a lime of inferior 
 quality, I strongly recommend its adoption. 11 
 
 We shall endeavour to explain, in what manner the ma- 
 nagement of the slaking alter this or that process, exercises 
 so great an influence, on the qualities of cements of rich limes 
 when immersed. It is certain, that all the principles which 
 exist in quick lime, are still contained in it after slaking, 
 since the smoke given out during the effervescence is, as we 
 have shown, nothing more than vapourised water, and that 
 we can therefore neither suppose a decomposition of any part 
 of the water used in the slaking, nor the disengagement of 
 the small quantity of carbonic acid, which the quick lime 
 of commerce usually retains. Thus, the lime parts with 
 nothing it contains. It merely absorbs water, and in ad- 
 dition, some carbonic acid, by the spontaneous extinction. 
 
 But it follows from the details given in Chapter V., that 
 quick lime, when slaked spontaneously, or by immersion, is 
 capable, at first, of forming a paste with much less water than 
 what is necessary to fulfil the proper measure of its saturation. 
 Now, as it retains the faculty of completing the dose by a 
 prolonged immersion, it necessarily results, that when inter- 
 posed in a mass of hydraulic cement, it must in a short time 
 solidify all the water at liberty, and thus accelerate the set 
 of the mixture, and at the same time increase its bulk. A 
 very slight enlargement of size, the result of this action, very 
 frequently exhibited itself in the course of our experiments, 
 by the fracture of the vessels containing the immerged cement. 
 The whole, therefore, explains itself by the aid of these con- 
 siderations. This absorbent faculty of limes slaked spontane- 
 ously, or by immersion, ought evidently to be measured by the 
 difference between the total weight of their proper allowance of 
 water, and the weight of that which they have provisionally 
 taken to form paste. Now this difference readies its maximum 
 with the very rich limes, audits minimum with the eminently 
 hydraulic limes. Thus is explained, in the simplest manner, 
 the progressive extension of the phenomena which H*e ob 
 
li)0 APPENDIX. 
 
 serve, and the correspondence between these phenomena 
 and the different degrees of richness or poverty of the limes 
 made use of. 
 
 (L.) But these considerations only embrace a certain com- 
 pass of the scale, for they do not explain in what manner 
 the ordinary mode of extinction rises superior to the two 
 others, when we arrive at the hydraulic, and a fortiori the 
 eminently hydraulic limes. It is true, indeed, that the dif- 
 ference between the first and second process is but trifling; 
 but between the first and third, the difference is very remark- 
 able. Now, viewing the hydraulic and eminently hydraulic 
 limes as natural ceraeats with excess of lime, we cau con- 
 ceive how the influence of an atmosphere, always more ox 
 less damp, must end by bringing on a chemical combination 
 of the constituent principles , which combination would be 
 the more energetic, the nearer these principles approach those 
 which constitute the true natural cements. Now such is the 
 ease with hydraulic cements. Such limes then, when expose.! 
 for a long time to the air, end by becoming no more than a 
 kind of caput meriuum, deprived of all binding quality. 
 
 (LI.) The strength of mortars, considered as aggregates, 
 e\ idently resides in that of the hydrate of lime or matrix which 
 envelopes the grains of sand. It is therefore very evident, 
 that the greater the density of the hydrate is, the greater 
 will be the resistance of the mixture, and that independently 
 of all the molecular changes which may be caused by the 
 
 c An explanation different to that given by M. Vicat lias suggested 
 itself to me, and I shall venture to give it a place here, although I have 
 not yet had an opportunity of ascertaining its propriety by any direct 
 experiments. The energy of the hydraulic tunes, as ie well known, is 
 developed by minute division, i note art. 185,) but entirely extinguished 
 by the influence of a damp atmosphere. This 1 have imagined (.> b 
 owing to a part of the lime uniting during calcination with the silica, alu- 
 mina, magnesia, &c, and being thereby enabled to resist slaking for 
 some time. When minutely subdivided, and made into a paste with water, 
 these parts gradually combine with and solidify the interstitial fluid, 
 causing the mixture to set and harden (note art. 307) ; and this takes 
 place more perfectly, the more inrimately the panicle; and fluid are 
 iit in contact bv the fineness of the subdivision. As it requires a 
 
APPENDIX. 197 
 
 adherence which unites the lime and sand. For the result 
 of these changes could only tend to increase the natural 
 density of the ganguc. Thus, without experiments, reason- 
 ing alone would have led us to the rule laid down. 
 
 (LII.) The cements cannot be assimilated with aggre- 
 gates, (at least the cements properly made with pouzzolanas 
 reduced to very fine powder). Here we have neither a sen- 
 sible matrix, nor solid substances interposed at appreciable 
 intervals. The mixture, whether it result or not from a 
 chemical combination of the principles, is physically consti- 
 tuted as a homogeneous body. Therefore it signifies but 
 little, before being mixed with the powdery ingredient in- 
 tended for it, whether the lime be in a soft or firm paste, 
 if, in the upshot, the mixture can be kneaded to a good 
 clayey consistency ; for, owing to their absorbing property, the 
 pouzzolanas in general, almost always require an addition of 
 water, and we then regulate the dose in such a maimer as to 
 attain the end proposed. 
 
 (LI1I.) This method of extinction has been constantly 
 applied at the works of the Angouleme bridge at Souillac, 
 and the success of their foundations has completely justified 
 its adoption. 
 
 (LIV.) M. Laguerenne, Engineer of bridges and roads, and 
 in charge of the construction of the bridge of Charles 10th at 
 Lyons, made a point of following, in every particular, the 
 method of manufacture, and immersion, laid down in this 
 chapter; he made use of a simply hydraulic lime, and of no 
 
 powerful effort to enable the water to overcome the cohesion of the 
 semivitrified particles, the ordinary process is best adapted to the hy- 
 draulic limes, to which subdivision is so important. The process by im- 
 mersion, or by exposure to the air, however, in which the action is less 
 strong, merely causes those particles to fall or separate which are ?<«altered 
 by the heat, and consequently incapable of adding to the hydraulic quality 
 of the lime ; while the cementing matter gradually unites with water, 
 but hardens and remains gritty, as the Sheppy stone does if wetted after 
 calcination. Hence, the best possible plan of developing the virtues 
 of hydraulic lime is, to slake it quickly, and then grind it to the finr-st 
 powder, or (as is now frequently done) pulverise first, and then slake 
 quickly. 
 
19B APPENDIX. 
 
 other ingredient than sand and flints. His beton was immersed 
 
 when cold, in a rapid current, and in an inclosure cleared out 
 by dredging. And such was the success of this mode of pro- 
 cedure, that after 12 or 15 days, they were able to lay the 
 foundations on masses of from two to three metres (6 ft. CA in. 
 to 9 ft. 10 in., Tr.) in height. The enormous blocks of free- 
 stone of which the courses were composed, rested on the 
 foundation of beton, as upon a rock. 
 
 The Lvonese builders, who frequently make use of beton 
 in their foundations, slake the lime by aspersion, covering 
 it with sand. They then pound and mix the materials 
 rapidly with a large quantity of water, and employ the whole 
 while still warm ; this method succeeds upon the whole. 
 When the beton is inclosed in the partitions of a framing, 
 and when the foundation is mainly supported by the timber- 
 work of such framing, it is of little consequence if the 
 lime swells up, and absorbs water, and afterwards takes a 
 long time to harden ; the foundation does not stand a bit the 
 worse; but it would have been altogether otherwise in the 
 case which I have mentioned above. The slowness of the 
 set, would hardly have allowed the foundation to be laid in 
 less than a year or fifteen months after immersion ; the rapidity 
 of the current during this interval, would certainly have de- 
 teriorated the beton, and it is even probable, that its immer- 
 sion might have been impossible; because the removal of the 
 lime, would have left behind nothing but a residue of sand 
 and flints, void of coherence. 
 
 (LV.) The works of the navigation -of the Yezere, have just 
 exhibited a sad example of the danger of using lime imper- 
 fectly slaked. Whether to gain time, or from any other motive, 
 they thought that they might dispense with allowing the 
 hydraulic lime they made use of, to stand and sour after slak- 
 ing. The masonry exhibited nothing extraordinary as long 
 M they remained dry during the low water in summer ; but 
 hardly had the winter floods set in, and submerged the works. 
 than the mortar swelled, and with so much force, that the In - 
 stone blocks of the facing of the side walls were displaced in 
 
APPENDIX. 100 
 
 numbers, especially about the shoulders of the abutments. In 
 short, the reconstruction of two locks was the result of these 
 accidents. 
 
 (LVI.) The phenomena described in this paragraph are 
 easily conceived ; the water begins to exert its solvent action 
 upon weak, or too rich cements, immediately after their im- 
 mersion. It first acts upon the very thin superficial coating 
 with which it is in contact, afterwards, it attacks the layer 
 next below it, &c. But its action is retarded by the difficul- 
 ties which the crust already attacked opposes to it, and as 
 these difficulties increase in a rapid progression, the cement 
 gains time to solidify more or less as its nature disposes 
 it. Now since this solidification has a limit, and as the action 
 of water, when continually renewed, is indefinite, the slow and 
 incessant increase in depth of the soft crust of which we have 
 spoken, necessarily ensues. 
 
 Mr. Petot, Engineer of bridges and roads, employed as an 
 apprentice in 1825 on the works of the bridge of the Duke 
 de Bordeaux at Saumur, has made some interesting experi- 
 ments on the action of water at the surface of mortars of 
 hydraulic lime and quartzose sand. He has observed, that 
 the presence of siliceous matter in the state of quartz, ex- 
 erted, during the earlier period of immersion, a powerful in- 
 fluence, which would seem to indicate a molecular action 
 which it would be highly important to establish. The follow- 
 ing is a concise table of Mr. Pctot's experiments. 
 
200 
 
 APPENDIX. 
 
 Nature of the compound! experimented upon. 
 
 Quantities <>( lime 
 
 dinolved, in Iihki 
 
 partt of the water 
 
 Of immersion, after 
 
 three clays. 
 
 1. Hydrate of hydraulic lime slaked spontaneously . . 
 
 2. Mortar, composed of 100 of sand, and 100 of the 
 
 1.030 
 
 0.560 
 
 0.540 
 
 0.607 
 0.601 
 
 1.100 
 0.840 
 0.500 
 0.450 
 0.630 
 
 3. Mortar, composed of 150 of sand, and 100 of the 
 
 4. Mortar, composed of 200 of sand, and 100 of the 
 
 5. Mortar, composed of 250 sand, and 100 hydrate . . 
 
 1. Hydrate of hydraulic lime, slaked by the ordinary 
 
 2. Mortar, composed of 100 parts of sand, and 100 of 
 
 3. Mortar as before, composed of 150 sand, and 100 of 
 
 4. Mortar as before, composed of 200 sand, and 100 of 
 
 5. Mortar as before, composed of 250 sand, and 100 of 
 
 u It is evident from this table," says Mr. Petot, " that it is 
 not by diminishing the number of points of contact, that we 
 diminish the solubility of the lime ; because in that case, it 
 would be necessary that that solubility should decrease, in 
 proportion as the quantity of sand is augmented, which is 
 contrary to the facts." 
 
 The portions of the mother water which were regained for 
 each sample, were about 130 grammes (2007.7 grs., Tr.) some- 
 times more, and sometimes less than the half of the whole with 
 which each of them was covered ; they had been filtered, and 
 precipitated by the binoxalatc of potash. It might be objected, 
 that the same specimen, although quite homogeneous, would, 
 if divided into many perfectly equal parts, and covered with 
 different doses of water, give as many different solubilities ; 
 for each portion should yield the same weight of lime from 
 an equal surface of contact, or nearly so ; but this remark 
 ceases to have any foundation, when the differences between 
 the quantities of water, and, more particularly, those quan- 
 tities themselves, are trilling, as in the ease before us. 
 
ai'I'Kndix. 201 
 
 The relative .solubilities of the different specimens being in 
 perfect accordance with the apparent hardness acquired br- 
 each specimen at the time of trial, it thence follows, that the 
 proportions of sand corresponding to the minimum solubility, 
 are also those which confer upon the mixture the greatest 
 hardness. 
 
 (LVII.) The observations contained in this paragraph, evi- 
 dently apply merely to the first ten or fifteen years following 
 immersion. We are unable to estimate the influence of ages ; 
 it creates between the constituent elements, even of mixtures 
 of rich lime and quartz, placed in certain circumstances, 
 reactions, which it is difficult to explain: reactions from 
 which in time results a cohesive force, which leaves nothing 
 to be desired. But as we have said elsewhere, mortars which 
 continue weak for more than one century, are the same to us 
 as if they would never harden ; for our bridges, locks, piers, 
 dams, &c, have to resist floods, thaws, and bad weather, 
 sometimes even before their entire completion. 
 
 NOTES ON CHAPTEIl XI. 
 
 (LVIII.) We made choice of a calcareous sand, of similar 
 grain to the granitic sand of the Dordogne, for the purpose of 
 preparing with it two mortars of the following proportions : — ■ 
 
 \ Hydraulic lime in paste . . . 100.00 
 £ Calcareous sand 100.00 
 
 No. 2. 
 
 Lime as before 100.00 
 
 Sand do 150.00 
 
 We also prepared in the same way, two other mortars in the 
 like proportions, marked below No. 1 bis, and No. 2 bis, with 
 granitic sand. These various mixtures being divided into 
 bricks, and some exposed to the weather, others to the action 
 of a damp soil for fourteen months, gave the following abso- 
 lute resistances per square centimetre : — 
 
202 APPENDIX. 
 
 I Corresponding resistance-., pel 
 Engush square inch. — Tb. 
 216.21 lbs. avoir. 
 . I So. 1 
 
 to the air . C So. 1 bis 12.24 | 171. 22 
 
 16.99 | 241.88 
 10.80 239.13 
 Mortars buried in C No. 1 . 12.72 I 181.05 
 
 the ground. .( No.'l bis 12.00(170.80 
 
 13.(58 194.72 
 12.48 ! 177.64 
 
 Ditto 
 
 Ditto 
 
 J No. 2 
 
 ( No. 2 
 
 ( No. 2 
 
 ( No. 2 
 
 Thus the superiority is always on the side of the calcareous 
 sand ; though at the same time we observe that the differ- 
 ences are trifling. 
 
 (LIX.) Whether it were the effect of chance, or that the 
 Romans were acquainted with the mutual relations between 
 the qualities of the lime, and the size of the sand ; they 
 frequently made use of unequal grained sand, with feebly 
 hydraulic mortars, and very coarse sand, sometimes even 
 small gravel, with rich lime. The remains of aqueducts, 
 amphitheatres, baths, &c, which we find at Cahors, Vienne, 
 and other places, prove this. Monge, in visiting the ruins of 
 Cesarea in Syria, found sunken impressions of mouldings and 
 ornaments in the heaps of mortar belonging to the counter- 
 forts which sustained the remains of a temple dedicated to 
 Augustus ; the reliefs were chipped at the edges, but the 
 mortar projected. It was so hard, that Monge in vain tried 
 to break off a bit. Now this mortar was composed of very 
 fine sand and a small quantity of lime, which by its greyish 
 colour, we may presume to be hydraulic. The old ramparts 
 of Vivicrs, (Ardeche,) which they were unable to destroy ex- 
 cept by mining, were cemented with a mortar composed of 
 very fine sand mixed with a white, eminently hydraulic lime. 
 This lime, of which we still continue to make use at the pre- 
 sent day, is generally known along the Rhone by its excellent 
 quality. It is probable, that in these cases chance has led to 
 the choice of the sands, more than intention ; but this does 
 not prevent these very examples, as facts, lending their sup- 
 
APPENDIX. 2U3 
 
 port to our own experiments, and confirming the rules laid 
 down in Chapter II. 
 
 (LX.) Loamy or argillaceous particles, deprive powders 
 and sands, which are largely impregnated with them, of the 
 faculty of composing mortars capable of enduring exposure to 
 the weather, in conjunction with the powerfully hydraulic 
 limes, and, a fortiori, with the rich limes. The old canal of 
 Xivernais, is a remarkable instance of this. The locks and 
 other works of art built about thirty-six years ago, with 
 mortar of slightly hydraulic lime and arenaceous sand, were, 
 when the works of that canal were recommenced, in a deplor- 
 able condition. It is especially opposite to the pond at 
 Baye, that the bad quality of these mortars is most remark- 
 able. Nought is to be seen amidst the rubbish of the dila- 
 pidated walls, but a reddish powder, in which we in vain 
 endeavour to find a solid fragment as big as a nut. 
 
 (LXI.) The explanation of the effects of slaking upon mor- 
 tars of rich lime, when exposed to the air, appears to be as 
 simple as the case of mortars immersed. We see, in fact, 
 that the mortar which has received the smallest allowance of 
 water, is also that which has the least to lose by drying, and 
 in a word that there is more substance, and consequentlv 
 more density in any bulk of mortar, the lime of which has 
 been slaked by immersion or spontaneously, than in an 
 equal bulk of mortar, the lime of which has been earned to 
 the farthest possible limit of expansion by the ordinary pro- 
 cess of extinction. In support of what has been said on 
 this subject in App. XXII., we shall subjoin the following 
 facts. 100 parts by weight of rich lime slaked by the ordinarv 
 process, after fifteen months' exposure (in small quantity) to 
 the air, weighed 59.60. A hundred parts of the same lime, 
 and in paste of equal consistency, which had been prepared 
 by immersion, weighed at the same period 77.10. Now the 
 two hydrates had at this time arrived at that point, at which 
 all external influence had ceased ; that is to say, that their 
 weight varied only in an insensible degree, by a purely 
 liygrometric action, sometimes positive, and sometimes nega- 
 
•-NU APPENDIX 
 
 tire ; it ought here to be remarked, that the bulks wire very 
 nearly equal at the commencement of the experiment. Thus 
 the density of the hydrate of lime slaked by the first process, 
 would finally, if shrinking were impossible, have been no 
 more than 0.77 of the density of the same lime slaked by 
 immersion. The superiority of the spontaneous over the 
 ordinary extinction is explained and understood in a pre- 
 cisely similar way ; but the differences of density cannot 
 be referred to, in comparing the extinction by immersion with 
 the spontaneous method ; the superiority of this latter mode 
 rests upon causes which are at present unknown. 
 
 With the simply hydraulic and eminently hydraulic limes, the 
 cohesive property surmounts all the rest; and the differences 
 of density, at all events very small, are in a measure lost, 
 in comparison with the adhesive action arising from the 
 perfect division of the material. Moreover, the negative in- 
 fluence of the spontaneous extinction has no other cause, 
 than that whieh has been specified in App. L. 
 
 (LXII.) Opinions are pretty nearly unanimous, astothebad 
 qualities of a mortar which has been drowned. The an- 
 cients insisted on the necessity of working up the mortar 
 without any addition of water; good mortar, said they, ought 
 to be tempered only with the sweat of the mason d -. It is 
 the fact, that all the power, and all the activity of the cleverest 
 labourer, will not succeed in uniting a very dry sand with 
 a very stiff hydrate of hydraulic lime (these two substances 
 being in tine proportions comprised within ordinary limits) ; 
 
 "' General Treussart gives an opposite opinion ; and as it would, if 
 correct, contribute materially to the economy of the manufacture of 
 mortars, it is desirable that it should not be entirely neglected without 
 being put to the test. He says, " The following experiments will show, 
 that those are in error who pretend, that mortar should be made witli 
 tin- sweat of the workmen only. It is sufficient that the sand be well 
 mixed with the lime, and this mixture can be made more effectually, and 
 much more economically, when the mortar is in a rather thin paste, than 
 when it is stiff. Besides, there is do inconvenience in making it rather 
 thin, since it frequently becomes Btiffer than what it is required to be when 
 the masons use it ; because, as I have remarked above, quick-lime when 
 reduced to thin paste, retains f'<>r a tolerably long period the faculty of 
 
APPENDIX. 205 
 
 in such a case it is necessary to add water, and there will be 
 no harm whatever in doing so, provided we do not exceed 
 the proper quantity. Good preparation of mortar, is an ex- 
 cessively hard thing to obtain in a work-yard: this difficulty 
 has suggested to different builders the idea of making use of 
 machines, and thereby rendering the manipulation independ- 
 ent of the will or strength of the workmen. Amongst the 
 more or less ingenious attempts which we might notice, that 
 which seems to have best succeeded, consists in making a 
 strong wheel, built upon the common pattern, to roll over the 
 lime and sand placed in a circular trough. The movement is 
 given by one or two horses harnessed to a gin. This method, 
 designed by M. Saint Leger, has been employed for the 
 fabrication of hydraulic mortars for the canal of Saint Mar- 
 tin ; it is right to add, that in the mortar so worked, the lime 
 and sand are very exactly mixed, and always of the same 
 consistency ; that the economy of workmanship is consider- 
 able, but it is also certain, that the mixture is far from pos- 
 sessing that degree of stiffness which it ought to have; more- 
 over, we can never attain it by the millstone, the wheel, or 
 the harrow. It is to the stamper alone that we must resort 
 to arrive at a solution of this problem, and its solution is not 
 without difficulties. In fact, it is not sufficient to beat with 
 force and rapidity, it must be struck true, that is to say, in 
 such a way that the blows be not lost. Now it is this which 
 constitutes address, a quality of which machines are not sus- 
 ceptible, except up to a certain point. 
 
 The bad quality of drowned mortar is not merely owing 
 to its want of compactness ; it depends also upon a chemical 
 cause, which it is important to be acquainted with, viz., that 
 
 solidifying water." (Memoire sur les Mortiers Hydrauliques, p. 13.) It 
 ought not to be forgotten, however, that most of General Treussart's 
 experiments were made with mixtures of common lime, and tarras, or 
 pouzzolana. Now the drowning of the mortar would in such a case only 
 deprive the lime of its power of absorbing water, of which property the 
 set of a compound of rich lime and pouzzolana is quite independent. The 
 case may. however, be very different with hydraulic limes, if they owe any 
 part of their virtues to the faculty of solidifying water Tr. 
 
 *F 
 
200 APPENDIX. 
 
 the water which is employed in large quantity, tends to de- 
 compose the silicate of lime with excess of base, and reduce 
 it to the state of the neutral silicate. M. Berthier has re- 
 marked, in fact, that if we take hydraulic lime as it leaves 
 the kiln, and composed for instance of 555 parts of pure lime, 
 to 400 of silica, if we slake and agitate it with a large quan- 
 tity of water, we shall only be able to collect by filtration G15 
 parts of undissolved matter, or neutral silicate, composed in 
 that case of 400 parts of silica, and 215 parts of lime*. 
 
 In using the water in small quantity, on the other hand, 
 it would be absorbed and solidified in great part by the com- 
 bination, so that decomposition would not take place. Now 
 there can be no doubt but that the hydrosilicate of lime, in 
 which the whole mass is chemically united, is of more use 
 than a mere mixture of the neutral hydrosilicate and the 
 pure hydrate of lime, which tends to form when too great a 
 quantity of water is made use of. 
 
 Nevertheless, it may not be impossible to communicate to 
 a mortar, mixed thin, the compactness which results from the 
 stiff consistency given at first; to effect this, it would be 
 best to spread it out in the sun, or in the open air, for the 
 purpose of evaporating the superabundant water quickly ; 
 and afterwards to beat it with stampers, in a trench properly 
 disposed. It will be curious to learn how far a mortar thus 
 prepared, may be equivalent to one obtained directly by a 
 good manipulation. This problem is peculiarly interest- 
 ing in reference to the economy of the labour of its 
 preparation. 
 
 (LXI II.) This method of guarding the mason's hand against 
 the causticity of the lime, was discovered by Mr. Silguy, 
 Engineer-in-chief of bridges and roads, employed upon the 
 canal from Nantes to Brest ; the workmen found it answer so 
 well, and valued its efficacy so highly, that they would at 
 
 e The silicate of lime is a compound of lime and silica ; the silicate 
 with excess of base, is a compound in which the lime exceeds its atomic 
 combating proportion. The neutral, that in which they neutralise one 
 another — Tr. 
 
APPENDIX. 207 
 
 last have gone on to an abuse of it, if care had not been 
 taken. 
 
 The soaking of the materials is evidently an addition to the 
 labour, which should be taken into account in the detailed 
 estimates. It is true it is sufficient to water the compact 
 stones, such as granite, quartz, mill -stone grit, lime-stone, 
 marble, &c, at the moment of using them ; but a mere as- 
 persion will not answer in regard to spongy and absorbent 
 substances, such as bricks, the soft or arenaceous lime-stones, 
 sand-stones, &c. ; when we have such materials, it is neces- 
 sary to moisten them without ceasing, and to keep them in a 
 permanent state of imbibition. To effect this, and to avoid 
 imposition, it is best to water in mass the heap from which 
 they are taken, so that they may reach the mason's hand in a 
 soaked state. In large work-yards, a fire engine, which pro- 
 jects and spreads the water to a great distance, answers per- 
 fectly for this purpose. It was thus that Mr. Inspector-Ge- 
 neral Deschamps, at the bridge of Bordeaux, watered the 
 bricks piled up on the service bridges. 
 
 (LXI V.) The influence of slow desiccation upon the good- 
 ness of mortars of hydraulic limes, has been for a long time 
 known in Italy. At Alexandria, in Piedmont, they manufac- 
 ture artificial stones which they call prisms, because being 
 generally used for the construction of the angles of walls, and 
 the starlings of bridges, &c, they have, in fact, the form of a 
 triangular prism. For this they make use of an hydraulic 
 lime, quarried in the neighbourhood of Casal; they slake it 
 after the ordinary mode, and when it has soured five or six 
 days, they put it into the middle of a basin of irregular 
 grained sand, from the substance of common sand, to that of 
 coarse gravel. This sand is chiefly quartzose, containing 
 calcareous debris ; the mixture is now made, and upon this 
 they bestow considerable pains. Before using it, they prepare 
 a triangular prismatic trench of an arbitrary length, on a level 
 space, secure from floods. They smooth the sides with the 
 trowel and a little water, and form the prisms in it in succes- 
 sive layers, inserting in the mortar stones of uniform size re- 
 
 *F 2 
 
208 APPENDIX. 
 
 gularly distributed. The prisms are tlien covered with the 
 same earth dug out of ihc trench, so as always to give a 
 thickness at top of 30 centimetres, (ll.s in., Tr.) The pro- 
 portions for a cubic metre (35.3 cubic ft., Tr.) are 0.*2 1 c. 
 (8.47 cubic ft., Tr.) of lime in paste, 0m. 90c. (31.77 cubic 
 ft.,Tr.) of uneven grained sand, and 0m. 20c. (7.06 cubic ft., 
 Tr.) of pebbles. 
 
 They give the prisms a length of 1.40 c. (4 ft. 6 in., Tr.) 
 to a breadth of side of Oin. 80c. (2 ft. 7^ in., Tr.); they re- 
 main under ground usually for three years, but two arc suf- 
 ficient when the lime is of the best quality; after that time 
 they are removed and applied to use. They will then bear 
 heavy loads ; we have seen them thrown one on the other, 
 from the height of six or seven metres (19^ to 23 ft., Tr.), they 
 were chipped at the edges, but did not break. 
 
 We left a piece of mortar composed of common granitic 
 sand, and common lime slaked spontaneously, but coated with 
 an hydraulic cement, to prevent the immediate contact of the 
 fluid, underwater for the space of a year; after which it was 
 withdrawn, deprived of its coating, and placed upon the dam]) 
 floor of a cellar, and afterwards, little by little, removed to more 
 elevated situations. After some months, the exterior parts 
 of this brick appeared very hard; we transferred it suddenly 
 from the cellar to a loft, in order to hasten the period of its 
 desiccation a little, and some time afterwards it was subjected 
 to experiment. At the moment of its rapture, the part de- 
 tached divided into two portions, one of which separated 
 from the other, just as the yolk of an egg separates from the 
 white, when it is well boiled. The envelope was pretty hard, 
 but the interior was readily squashed in the lingers. "We again 
 exposed the piece in which this separation had not taken 
 place, to the action of the air, expecting certainly, that at the 
 end of a few months the nucleus and the crust would ex- 
 hibit no difference, but it was not so; the nucleus never 
 attained the hardness of the envelope. The difference was, 
 and always continued to be such, that there was a \ cry marked 
 interruption of continuity between the two parts. Thus the 
 
APPENDIX. -209 
 
 act of solidification had been rudely interrupted, by the 
 transition from a (rash damp atmosphere to a warm one. 
 This fact was too interesting to allow us to trust to one ex- 
 periment. Such as we have since repeated have all exhibited 
 the same phenomena. 
 
 Vilruvius (lib. ii. chap, viii.) gives many instances of build- 
 ings near Rome, ruined in a short lime, owing to the too 
 hasty drying of the mortar. The lime, says he, separates 
 from the sand, if the stones (of the masonry) absorb all the 
 moisture by their pores. 
 
 (LXV.) M. John (in the memoir quoted) mentions, that 
 not long ago, on demolishing one of the columns of the tower 
 of Saint Peter, at Berlin, built about 80 years, and -27 feet 
 in diameter, they found the mortar in the interior of the 
 masonry as fresh as if it had only been applied the day be- 
 fore ; it had the caustic taste, and formed milk of lime with 
 water. But we very often meet with good mortars in the 
 foundations, and in the massive walls of the buildings of the 
 middle ages. We have often discovered the nature of the 
 lime made use of for these mortars, by the particles or lumps 
 of the lime not mixed with the sand ; and we have generally 
 found it to be either rich, or very feebly hydraulic. It results 
 from this, that after a maceration of six or seven hundred 
 years, favoured by the constant humidity of the soil under 
 which they are buried, the mortars of rich lime at last harden ; 
 the term is rather long. With reference to these observations, 
 we shall add the analyses, made by M. Johu, of some old 
 and antique mortars of excellent quality. 
 
210 
 
 APPENDIX. 
 
 TABLE OF THE CONSTITUENT PARTS. 
 Contained in 100 Parts or Mortar. 
 
 DESCRIPTION. 
 
 < 
 
 'c 
 o 
 
 c 
 
 E 
 
 3 
 
 c 
 
 3 
 
 i 
 c 
 
 1 
 
 ■ 
 
 ■ 
 
 3 « r > 
 
 8 
 > 
 
 "5 
 
 •5 
 | 
 
 5 
 a 
 a 
 a 
 Q 
 
 < 
 
 1. — Mortar six hundred years ^ 
 old, from the cathedral ofV 
 
 5.00 
 
 8.70 
 
 1.25 
 
 1.30 
 
 83.75 
 
 
 2. — Mortar six hundred years^ 
 old, from the church of Saint | 
 Peter at Berlin, (the founda- \ 
 tion laid in a situation con- i 
 stantlv impregnated with wa- 
 ter,) " ; 
 
 1.75 
 
 9.25 
 
 3.75 
 
 6.75 
 
 78.50 
 
 
 3. — Roman mortar, from an an-") 
 
 
 
 
 
 
 
 cient city wall, built at Cologne (. 
 under Aurippa, in the 1st cen- f 
 
 tury of the Christian era . . J 
 
 9.00 
 
 15.1G 
 
 0.25 
 
 4.00 
 
 68.00 
 
 2.75 
 
 4. — Roman mortar, from an anO 
 cient tower built by Agrippa, r 
 at the same period .... J 
 
 12.00 
 
 24.00 
 
 0.25 
 
 5.00 
 
 5G.00 
 
 •2.75 
 
 5. — Roman mortar, taken from a J 
 beton built in the Rhine . . S 
 
 2.25 
 
 6.90 
 
 ( 0.35 
 
 1.00 
 
 - L50 
 
 
 By rendering these results, approximately, into technical 
 language, we find as follows f : 
 
 ' Being anxious to compare the quantities of lime and sand exhibited by 
 the analyses of old mortars, with the proportions used for the public 
 works, I made some experiments, in order to determine the ratio be- 
 ll the weight of pure lime, and sand, and the measures of hydrate of 
 lime, and sand, in the condition in which they were usually served out 
 for the mixture of mortar, for the Government building-;. I found, that a 
 cubic foot of slaked lime in that condition, (vide note to Appendix 20,) 
 and weighing 30 lbs., contained only l^i li>~. of pur* lime; an equal 
 measure of 6and weighed 75 lbs., which numbers are very nearly iu the 
 
APFENDIX. 
 
 211 
 
 The composition off Hydraulic lime in paste 
 
 mortar No. 1 
 
 That of No. 2 
 
 Ditto No. 3 
 
 Ditto No. 4 
 
 Ditto No. 5 
 
 C En 
 
 100 
 560 
 
 100 
 004 
 100 
 187 
 100 
 137 
 100 
 607 
 
 £ Quartzosc sand .... 
 
 Eminently hydraulic lime 
 in paste 
 
 Quartzose sand . . . 
 f Rich lime in paste . . 
 (. Quartzose sand . 
 { Very rich lime in paste 
 C Quartzose sand . 
 { Feebly hydraulic lime . 
 ( Quartzose sand . . . 
 
 This reduction is on the supposition — 
 
 1st. That in all probability the silica, alumina, and iron 
 dissolved, belonged to the lime. 
 
 2d. That the cubic metre of quartzose sand weighs 1400 
 kil. (3088.8 lbs., Tr.), and that the same bulk of quick lime 
 without voids, also comes to 1400 kil., (3088.8 lbs., Tr.). 
 
 3d. That the simply hydraulic lime, gives 1.500 for 1.00 by 
 slaking; the emineutly hydraulic lime 1.00 for 1.00, and the 
 rich or feebly hydraulic lime 2.00 for 1.00. 
 
 These hypotheses being in accordance with the average 
 results of experiment, must approach very near the truth. 
 
 This table evidently proves, that the influence of the quali- 
 ties of the lime, and the proportions, is lost in the presence 
 of that of ages, for all the five mortars analyzed, were very 
 hard, especially Nos. 3, 4, and 5. But this astonishing effect 
 of time, is only felt, as I have before remarked, by mortars in 
 foundations, or such as are lodged in the centre of massive 
 
 proportion of 1 to 4. Hence, if the quantity of pure lime furnished by 
 an analysis, be multiplied by 4, its weight will then be to the weight of 
 silica and insoluble matter of that kind contained in the cement, in the 
 same ratio as the bulks of hydrate of lime and sand would be, if measured 
 in the way I have described in the note above referred to. This rule is 
 however only applicable to analyses of mortars of rich lime, as the 
 varying ratios of expansion in slaking, of the poor and hydraulic limes, 
 cause the same experiments to be necessary, for the elimination of the 
 like rule, for their reduction to technical language. — Tb. 
 
•21-2 Airi.Ninx. 
 
 bodies of masonry ; in a word, where the humidity can have 
 been constantly retained. 
 
 NOTES ON CHAPTER XIII. 
 
 (LXVI.) Our observations have led us to think, that 
 the cements of artificial pouzzolanas, obtained by calci- 
 nation of the clays wholly or nearly free from iron, are those 
 whose deterioration is the most marked, when we pass them 
 suddenly, or even by degrees, from a damp situation to a dry 
 atmosphere ; the oxide of iron, therefore, is favourable to 
 cements exposed to the air. The observations which we 
 have made on this kind of phenomenon, are too few to give 
 much weight to this opinion, which it may nevertheless be of 
 use to express. 
 
 (LXVII.) — * "Three parts of oil heated with one sixth of its 
 weight of litharge, and one part of wax, form a good compo- 
 sition for protecting valuable work. One part of linseed oil, 
 one tenth of its weight of litharge, and from two to three parts 
 of resin, form a suitable composition for common work. 
 
 " The oils are heated, and applied with a brush over the sur- 
 face to be preserved ; should the surfaces be impregnated with 
 humidity, they must be heated and perfectly dried before paint- 
 ing them. I have made great use of the boiled lithargirated 
 oils, applied hot, on cornices and parts exposed to moisture, 
 and I have in all climates met with unexpected success ; the 
 stuccoes and the walls thus defended, were dry and sound, 
 and resisted both rainy weather and frosts. With respect to 
 compositions containing tar, bitumen, resin, wax, &c, &c., 
 they ought always to be heated before application." 
 
 " All the pigments composed of oils and the ordinary co- 
 lours, and which have little body, require to be renewed alter 
 ■ few years ; but of those containing wax, resin, &c, a single 
 coat is sufficient; and if the time should arrive when they 
 cease to be of any effect, the hydraulic mortars will by that 
 period have acquired so much solidity, as to oppose sufficient 
 resistance to the usual agents which tend to deteriorate 
 
APPENDIX. 213 
 
 them." — Raucourt dc Charleville, Traite des Mortiers, pp. 
 283, 4, and 293. 
 
 (LXVIII.) In Italy even, where the climate is remarkably 
 mild, the vertical plasters of pouzzolana cement exposed to 
 the north, finally become ruined g ; they repair them by 
 means of rich mastics variously composed. The weak ce- 
 ments overcharged with lime, or those resulting from a bad 
 manipulation, crumble, or become disaggregated by efflores- 
 cence, in the same way as ill-burnt bricks. Cements of good 
 quality split in flakes. These effects of the frost are esta- 
 blished by cases unfortunately too authentic. If, in fact, we 
 consult the military Engineers, as to the pointing in cement 
 applied to the revetments of the forts in the north of France ; 
 the Engineers of roads and bridges, regarding the same ce- 
 
 8 During my superintendence of public buildings in the northern divi- 
 sion of the Madras Presidency, I made many endeavours to investigate 
 the cause of the very speedy decay in certain situations, of stuccoes, which 
 in others, apparently similarly exposed, possessed the greatest durability ; 
 and I was soon led to observe the very injurious effects of alternations of 
 moisture and dryness upon mortars composed of rich lime and sand, by no- 
 ticing the almost constant failure of those mortars which exhibited a mottled 
 appearance on first drying. This phenomenon, which is interesting when 
 viewed in connexion with the future durability of a cement, consists in a 
 distinct exhibition of the courses of the masonry through the plaster, the 
 joints being clearly defined, sometimes on a darker, and at others on a 
 lighter ground, and indicating at one time an excess of humidity in the 
 spaces opposite the bricks, and at others opposite the joints. These 
 appearances were generally confined to within a few feet of the lower 
 portion of the walls, which parts alone were subject to the early decay I 
 allude to ; and as they take place in a climate not subject to frost, and de- 
 note a cause of the degradation of mortars hitherto unexamined, it may be 
 useful to notice briefly the leading facts which were observed. 
 
 Common stucco, when plastered on a wall of brick and mortar, gene- 
 rally presented the appearance, on first drying, of damp joints and dry 
 spaces (opposite the bricks) ; and this seemed to be owing to the spongy 
 nature of the bricks, which, unless fully saturated with water in using 
 them, caused the stucco to part more speedily with its moisture in those 
 parts over them, than elsewhere. After the same stucco has once 
 thoroughly dried, if the situation be damp, these appearances may be 
 reversed, more especially if the bricks be of an absorbent kind, or ill burnt. 
 In tliis case it appears that being kept constantly damp by sucking up moisture 
 
214 APPENDIX. 
 
 ments applied to locks ; and all the proprietors of manufac- 
 tories, or others, who have been in the way of using them, 
 whether in vertical plastering, or in terracing, &.c, &c, — all 
 will answer in the affirmative. 
 
 But the intermixture of sand powerfully checks the ex- 
 pansive force of the freezing water, by assimilating the 
 cements, whose texture it modifies, to porous and permeable 
 stones ; to the sand-stones, sandy lime-stones, &c. In fact, 
 it is not the most compact and most impermeable stones, that 
 are the least acted on by the frost ; experience always proves 
 the contrary. 
 
 The action of frost, presents a class of phenomena which 
 appear incomprehensible, when we look upon them as 
 the mere results of the expansive force of the ice. With the 
 
 from the earth, they become more charged with it than thestuccoitself, which 
 is of a less permeable nature; and exhaling it during hot weather, render the 
 spaces damp in comparison with the joints, which have remained dry. 
 And it is remarkable also that, in such a case, the phenomena may be 
 again reversed by soaking the whole surface with water; for if the stucco 
 be not a very compact one, so as completely to exclude imbibition, the 
 subsequent desiccation will proceed so much more rapidly opposite the 
 bricks, which will then be comparatively dry, that the joints will continue 
 long damp after the spaces have ceased to be so. Stucco, covering walls 
 built of brick and clay, I have always seen exhibiting dry spaces and 
 damp joints. 
 
 Roman cement, Mr. Loriot's composition 6tucco, and such as set on 
 first applying them, I have generally observed to present an opposite 
 appearance to common mortars in which the lime has been well tempered. 
 The best mortars, when exposed in situations which occasioned the above 
 phenomena, were liable to early ruin, sometimes within a week of their 
 completion, the decay being invariably confined to the region in which 
 they were manifested ; such as were beyond the reach of the moisture 
 remaining perfectly sound for years. The failure was accompanied by 
 the separation of large flakes, which were detached from the body of the 
 cement, leaving the mass in a crumbling and disaggregated state behind it. 
 These flakes varied in thickness with the age of the mortar, a fact which 
 led me to the supposition, that they might consist of the superficial crust 
 of the regenerated mortar, separated from the part behind it by some inter- 
 nal changes, occasioned by the alternations of moisture and dryness ; bat 
 I found it impossible to prove this point directly, from the difficulty of 
 detecting the separation of a patch of the falling plaster, in time to find 
 the parts in < <>ntact with it still in a caustic state. — Tb. 
 
APPENDIX. 215 
 
 exception of such stones as are intersected by threads, visible 
 or not, but into which the water may insinuate itself in thin 
 capillary seams, we have hitherto been unable to give any 
 explanation of it. In fact, as often as we endeavour to ap- 
 proach this question, the most contradictory facts present 
 themselves at the same time. Thus, wretched mortars of 
 rich lime, very much overcharged with sand, and which a 
 mere pressure of the finger would crumble, stand a cold of 12° 
 centigrades h , (about -f- 10° Fahrenheit, Tr.,) with impunity, al- 
 though soaked to saturation ; whilst the brick, twenty times 
 harder, falls to powder at 4° or 6° (from 25° to 21° Fahrenheit, 
 Tr.). Some lime-stones of a compact kind("vives"), very hard, 
 intersected in every direction by short closely crowded veins, 
 (as for instance, the Chouin lime-stone, used at Lyons,) en- 
 dure the most severe winters, at the same time that other 
 stones physically alike, (such as those of Saint George's at 
 Cahors,) split in every direction. Lastly, what can we say 
 of those materials, which are liable to injury from frost when 
 impregnated with the water they contained in quarry, and 
 not liable to be acted on after they have lost it, although they 
 may be elsewhere impregnated to saturation by rain water ? 
 
 In this state of the case, we are compelled, in order to 
 speak with certainty, as to the qualities of such and such 
 materials, to note the manner in which they behave for seve- 
 ral years. And even many years may be insufficient in the 
 southern countries, wdiere severe winters ensue only at long 
 intervals. We must therefore try to multiply the causes of 
 destruction, to the specimens which we make trial of, and 
 gain time by accumulating, as it were, the effects of many 
 winters. To effect this, we shall observe, that after having 
 raised or separated the parts of the substances it acts upon, 
 the crystallized water, for all that, keeps them still clinging to 
 one another, until a thaw; at which period the disunion takes 
 
 6 I take this of course, to refer to minus 12° of the centigrade thermo- 
 meter ; and I have given its equivalent accordingly, as about -f- 10° 
 Fahrenheit, or 22° below freezing point. Were it plus 12° instead of 
 minus, it would correspond to very nearly 54° of our thermometer Ta. 
 
210 APPENDIX. 
 
 place. Hence we infer, that we ought to take the duration 
 of the frosts much less into account, than the number of suc- 
 cessions of frosts and thaws which follow one another. Now 
 we can create as many thaws as we have days of frost in a 
 winter, by each time pouring boiling water over the experi- 
 mental specimens, to melt the ice or snowy efflorescence 
 with which they are covered, and release them from their 
 detached Hakes, if they have any. 
 
 It was in this way that we proceeded with respect to ;i 
 number of fragments of mortars and cements of all kinds, 
 which we studied. The results, which are made known in the 
 thirteenth chapter, are the fruit of the observations often con- 
 secutive winters, amongst the number of which, is that of 
 1819 and 20, when the thermometer fell to 1*2° of the centi- 
 grade, (about 10° Fahrenheit, Tr.) 
 
 (LXIX.) Whilst we were engaged with these researches, 
 Mr. Brard, (then director of the collieries of Lardiu, in the 
 department of Dordogne,) tried to distinguish the stones 
 which are injured by frost, from those which are not so, by 
 substituting for the expansive force of congealing water, that 
 of an easily crystallizable salt, the sulphate of soda. No 
 sooner were we made acquainted with this happy idea, than 
 we were eager to try it upon our mortars. In conformity 
 with the directions of the able mineralogist whom we have 
 just named, a hundred specimens were impregnated with a 
 warm saturated solution of the sulphate of soda, and then 
 exposed in a loft to the temperature of 25° to 30° centigrade, 
 (77° to 86° Fahrenheit, Tr.,) and lastly, washed from day to day 
 with pure water. These specimens were not long in giving 
 signs of degradation, in the following order: — 
 
 AFTER TWENTY-FOUK HOURS. 
 
 All the mortars of rich limes have become slightly disaggre- 
 gated. The progress is more perceptible, and more widely 
 diffused, in the set of ordinary (as regards the slaking) speci- 
 mens, than the immersion (as to extinction) series. The 
 spontaneous (extinction) set are the least injured. 
 
UPPENDIX. 217 
 
 The mortars of hydraulic lime and fine gravel, or very 
 coarse sand, split at the corners; those with fine sand, stand 
 well. 
 
 AFTER FORTY-EIGHT HOURS. 
 
 The three series of mortars of rich lime, are in decompo- 
 sition, with the exception of the numbers of the spontaneous 
 series, which correspond to the proportions of 50, CO, 70, 
 and 80 parts of sand, to 100 of lime in paste. The other 
 " rich" mortars detach thick flakes and split at the corners ; 
 the "poor" ones become disaggregated superficiallv. 
 
 The mortars of hydraulic lime, and gravel, or very coarse 
 sand, have completely crumbled to pieces; those in which 
 the sand is fine, continue to stand well. 
 
 AFTER SEVENTY-TWO HOURS. 
 
 None of the mortars of rich lime remain, except numbers 
 1 and -2 of the spontaneous series. Of the mortars composed 
 of hydraulic limes and fine sand, the "richest" split at the 
 corners, the " poorest" continue to do well. 
 
 The observations were continued for 24 davs ; after the 
 twelfth, not one of the mortars remained unimpaired, except 
 those of very poor hydraulic limes, and the mortar of the 
 spontaneous series of rich lime, corresponding to the propor- 
 tions of 50 sand to 100 of lime in paste, which continued 
 well till the twenty-third day. We have thus been con- 
 vinced, that the agency of the alkaline salt is much more 
 powerful than that of water frozen in our climate. We were 
 about to have instituted other experiments made with solu- 
 tions variously charged, when an accident diverted us from 
 it. In trying, in fact, to recover from the washings the por- 
 tions of salt dissolved by the successsivc eleutriations, we 
 perceived that the form of the crystals was no longer the 
 same. Instead of six-sided prisms, we got nothing but 
 crystals flattened into buttons, and entirely of a different 
 structure. No doubt then, the alkaline ley had acted upon 
 the lime of the mortar. 
 
018 APPENDIX, 
 
 M. Brard's process therefore can no longer be applied to 
 this description of materials. We should, however, recom- 
 mend it, when we only wish to establish the relative qualities 
 of cements or mortars. It will then perfectly indicate the 
 order in which the compounds will be able to resist the action 
 of cold; and if we moderate the effects of the crystallization, 
 by impregnating the bodies under trial with a solution not 
 saturated, it is probable that some day we may succeed in 
 discovering that degree of solution which suits bricks and 
 stones, to represent with precision, in respect to them, the 
 power of congealed water, at this or that degree of the 
 thermometer; but it is hardly any where, except in the 
 north, that such an experiment can well be made. 
 
 We have said, that mortar composed of rich lime slaked 
 spontaneously, and compounded in the proportions of 50 
 sand to 100 of lime in paste, continued to do well until the 
 twenty-third day ; and this at a time when excellent mortars 
 of hydraulic lime, and calcareous stones of acknowledged 
 goodness, did not last beyond the seventh or eighth day ; 
 such an experiment deserved to be repeated, and it was so, 
 with the same success. The mortar which behaved in this 
 manner was six years old, its relative resistance by super- 
 ficial ce^/we/re corresponded to 4.80 kil. (68.32 lbs. avoirdu- 
 pois per square inch, Tr.) This is not, as we may sec, 
 quite half of the mean relative resistance of mortars of hy- 
 draulic limes '. Now there are a multitude of cases in reference 
 to ordinary buildings, in which the mortars of revetments 
 have absolutely nothing to contend against bnt the weather, 
 and are besides sufficiently strong, when there is nought to 
 fear from the frost. 
 
 We do not think, that in this respect it is possible to devise 
 any thing in the way of a mixture of lime and sand, which 
 offers a better assurance than the mortar above mentioned. 
 
 i Vide Article 282 — Tn. 
 
APPENDIX. Q19 
 
 NOTES ON CHAPTER XIV. 
 
 (LXX.) Loriot's process consists in introducing into 
 mortar, worked to a thin consistency, such a quantity of 
 quick lime in powder, that the superabundant water of the 
 mixture may suffice for its extinction, and that consequently, 
 the mixture, without reaching that degree of desiccation pro- 
 ducing pulverulence, may nevertheless become solid in a few 
 instants. 
 
 Loriot's process, like many others, has been very much in 
 vogue, and like many others also, has ended by falling into 
 oblivion. Such is the usual fate of all false conceptions, and 
 that was certainly one, which viewed the induration of mor- 
 tars as the mere result of a more or less rapid desiccation, and 
 in consequence, supposed it possible to obtain this end, by 
 the introduction of a powerful absorbent k . 
 
 Specimens cast in mortar of hydraulic lime prepared 
 according to M. Loriot's process, although afterwards sub- 
 mitted to the influence of a very slow desiccation under a fresh 
 soil, never attained more than a moderate hardness. It 
 seemed, that the introduction of the quick lime in powder, how- 
 ever it might have hastened the set, had not made up for the 
 want of density inseparable from the thin consistency which 
 
 k Mr. Smeaton says of this process, " I have made trial of this me- 
 thod, both in small and in large ; for however little likelihood of advan- 
 tage a proposition may contain, yet, when this concerns a physical pro- 
 cess, nothing can be safely concluded but from actual trial : and I must 
 candidly own that the effect was much better than I had expected; for I 
 found the composition not only set more readily than mortar as commonly 
 made up, but much less liable to crack, and consequently, if this cement 
 was made use of in water building, it was less apt to re-dissolve, because 
 it would more speedily get set to a firmer consistence, and so as more 
 ably to resist the water from entering its pores ; but when the water was 
 brought upon it, in whatever state of hardness it was at the time, it at 
 best remained in that state without any further induration, while the water 
 remained upon it ; and as I expect would so remain, till it had some op- 
 portunity of acquiring hardness by further drying."— Construction of the 
 Eddystone Lighthouse. 
 
 In operating with the pure shell-lime of Madras, I have myself found 
 
00(( APPENDIX. 
 
 we wore obliged to give the mixture of Band and slaked lime 
 
 in the first instance. 
 
 NOTES ON CHAPTER XV. 
 
 (LXXI.) " Iii 1706, Messrs. Parker and Wyatt obtained 
 the royal patent for the manufacture in London of a par- 
 ticular kind of lime, which they termed water cement, and 
 to which they afterwards gave the name of Roman cement, a 
 name the more unsuitable, as the Romans neither were ac- 
 quainted with, nor ever made use of any thing of the kind. 
 This speculation has had the greatest success, and it has 
 given birth to several others of the same kind, which prosper 
 equally. 
 
 " M. Lesage, a military Engineer, made known, twenty 
 years ago, the properties of a kind of lirne which they made 
 use of at that time at Boulogne-sur-Mer, (Dover straits,) 
 and which he has designated by the name of platre cement. 
 We learn from the very circumstantial report of it which he 
 published in the " Journal des Mines," vol. XII., p. 145, 
 that that lime is precisely the same material as the English 
 
 this process answer very well for the composition of stucco ; for after a 
 comparison during two years, of surfaces similarly exposed, containing 
 from 120 to 150 square feet each, I found M. Loriot's composition 
 very superior in hardness, and in resistance to atmospheric changes, 
 to the ordinary stucco of irell tempered rick lime and sand. It is, how- 
 ever, very difficult to get workmen unaccustomed to it to apply it pro- 
 perly, as a little want of care mars the whole effect. It is also more 
 expensive. 
 
 The mortars above alluded to were worked up and applied with 
 iaghery (coarse sugar) dissolved in water. Mr. Smeaton agrees with 
 Dr. Hingins in thinking, that both for dry and water works the use of fresh 
 slaked lime, of whatever kind, is preferable to M. Loriot's process; and I 
 am quite of this opinion myself, with respect to hydraulic lime quenched 
 hoi from the kiln and pulverised, which will be found to produce as good 
 an effect with les> labour and uncertainty. — Tn. 
 
APPENDIX. 
 
 221 
 
 natural cement. M. Drappiez has given a very exact 
 analysis of the Boulogne stone, which we shall now compare 
 with that furnished by an analysis of the English one. 
 
 " Carbonate of lime ... 
 Carbonate of magnesia . 
 
 Carbonate of iron 
 
 Carbonate of manganese 
 
 rSilica 
 
 Clay, -J Alumina 
 
 (.Oxide of iron. . 
 Water 
 
 1 English 
 stone. 
 
 Boulogne 
 stone. 
 
 657 
 
 616 
 
 5 
 
 . . 
 
 60 
 
 60 
 
 19 
 
 . . 
 
 180 
 
 150 
 
 66 
 
 48 
 
 
 30 
 
 13 
 
 1000 
 
 66 
 
 970~ 
 
 '' The English stone is of a brown grey colour, compact, 
 line grained, and susceptible of polish ; its specific gravity is 
 2.59. That of Boulogne is also compact, very fine grained, 
 and susceptible of polish, but it is of a yellowish grey colour ; 
 it has never been met with except in rolled pebbles on the sea 
 beach ; while the English stone is dug out from the marls, 
 where it is found imbedded in the form of nodular masses. 
 
 " Saint Petersburg has now, like London, its natural cement; 
 it owes this advantage to Messrs. Clapeyron and Lame, 
 French mining Engineers, temporarily attached as professors 
 to the Polytechnic Institute of Russia. This discovery has 
 already effected important saving in the execution of the 
 great hydraulic works to which the natural cement has been 
 applied." (Extract from M. Berliner's Memoir on hydraulic 
 lime-stones.) 
 
 We have ourselves met with natural cements on the banks 
 of the Loire, between Nevcrs and Briare, and at Baye, at the 
 point of junction of the canal of Nivernais; but in their 
 quickness of setting, and final induration, they were not equal, 
 either to the English cement, or that of Boulogne. 
 
222 appendix. 
 
 The following is an analysis of the cement of Bave. 
 
 Bluish grey Argillaceous Lime-stem . 
 
 Carbonate of lime 3-20 
 
 Silica . * 520 
 
 Alumina S 
 
 Carbonate of magnesia 40 
 
 Alumina and iron, dissolved 94 
 
 Water 30 
 
 1010 
 
 This cement set three days alter immersion, and at the 
 end of one year exhibited a hardness, measured by the de- 
 sion of 3.65 mill. 0.13070 inch, Tr.) ' 
 
 NOTES ON CHAPTER XVI. 
 
 (LXXI1.) — * Extracts from the analysis (by Dr. Malcolm- 
 son) of the cement from the pyramid of Cheops. 
 
 (1.) A hundred grains of this cement, having been pulve- 
 
 1 The following is an analysis of the cement referred to in the note to 
 Art. 24, and the mineral composing which was brought from Bezoarah 
 in the Guntoor district of the Madras presidency. It is found on the 
 banks of the river Kistnah, and in the immediate vicinity, as I was in- 
 formed, in the f>rni of small irr gular shaped nodules, of a dark bluish grey 
 colour, of various shades, very hard, susceptible of a dull j olish, specific 
 gravity 2. .52. The constituents in 100 parts were, lime 43.5, silica and 
 alumina 18, arbonic acid 36. The silica and alumina which 
 
 remained behind on dissolving the stone in acid, presented the appearance 
 of a black clay ; but the lime was of a buffcolour after calcination. 
 
 This cement, when made into -till paste, and immersed in the manner 
 prescribed in the beginning of this volume, (Articles 8, 9, 10, 11, 12,) set in 
 48 hour-; and in 15 da\s was so firm, that I was unable to thrust the 
 needle (Art. 20 j into it, and was obliged to desist for fear of breaking it. 
 At the end of nine months, its hardness was measured by the instrument 
 used by M. Vicat, and was indicated bya depression of 0.15 of an inch; no 
 part '.f the surface baling been removed previous to this trial. — Tr. 
 
APPENDIX. 223 
 
 rised, and dried at a steam heat, were immersed in six ounces 
 of pure water, and after standing over night, were heated in 
 contact with it, for the purpose of removing its soluble salts, 
 Tt was then separated from the water by filtration, washed, and 
 dried, and on weighing amounted to 81.5 grains, having lost 
 18.5 grains of soluble matters, which were examined sepa- 
 rately, and found to consist of sulphate of lime 15.3, sul- 
 phate of soda 3.2. 
 
 (2.) The residue of 81.5 grains, left after the separation of 
 the above soluble salts, was now treated with dilute muriatic 
 acid, (of which 4 cubic inches were used,) and lost of car- 
 bonic acid 4.7 grains. If to this be added 2 cubic inches 
 of the gas, (or 0.94 grains,) for the absorption by the 4 in. 
 of fluid, the whole weight of carbonic acid in the cement 
 will be 5.(>4 grains" 1 . 
 
 (8.) The insoluble parts which were left behind after the 
 action of the muriatic acid in the last process, were now 
 separated froni the solution by filtering, and after being washed 
 and dried, were found to weigh 54.7 grains. This consisted 
 principally of crystals of sulphate of lime, with alumina". 
 
 (4.) The solution just mentioned, and washings, &c, having 
 been tested for magnesia, iron, silica, and other matters, un- 
 successfully, was now boiled with excess of carbonate of 
 potash, which threw down a precipitate, (of carbonate of lime, 
 &c.,) which when washed, dried, and weighed amounted to 
 19.9 grains; and was reduced by ignition to 11 grains. Of 
 
 m Particular attention was paid in this analysis, to the determination of 
 the exact quantities of carbonic acid and lime, and the processes were re- 
 peated, and varied once or twice, with close agreement in the results. 
 Part of the cement was also, previous to analysis, reduced to powder, 
 and tested by moistened turmeric paper, the solution of sulphate of iron, 
 and the tincture of galls, &c, to detect the presence of caustic lime, but 
 no trace was observable. 
 
 n The insoluble residue mentioned in process 3, was levigated with oil 
 and powdered charcoal, and the whole then ignited. On digesting par! 
 of the powder which remained after this process, first in caustic potash 
 to separate alumina, and then (after washing) in dilute nitric acid, fch 
 whole was dissolved without any residue ; whence I concluded that i; 
 consisted of lime and alumina only Tr. 
 
 *G 2 
 
224 APPENDIX. 
 
 this, by a subsequent process, 0.8 is found to be alumina ; 
 the remainder pure lime. 
 
 (5.) In order to ascertain the amount of water in a hundred 
 grains of the cement, that quantity, after being dried at 212", 
 was put into a bent glass tube, one portion of which contained 
 chloride of calcium, and which was connected at its extremity 
 with the mercurial trough. On applying heat, much water 
 was given off, a very small quantity of which (estimated at 
 about one grain) escaped from a leak in the apparatus. After 
 completing the process, the chloride was found to have gained 
 16.5 grainsin weight, to which if we add the one grain which 
 escaped, we shall have the whole quantity of water separated 
 from the cement, which will amount to 17.5 grains. This, 
 however, includes both the water associated with the car- 
 bonate of lime, and that contained in the sulphates of lime 
 and soda. 
 
 The constituents of 100 grains of the cement are as follows : 
 Soluble salts, consisting of sulphates of lime 
 
 and soda 18.5 grains 
 
 Carbonic acid 5.04 
 
 Lime 10.7 
 
 Alumina 0.3 
 
 Insoluble substances, consisting of alumina 
 
 and crystals of selenite 5 J .7 
 
 Water associated with the carbonate of 
 
 lime, and loss 10.10 
 
 Total grains 100.00 
 
 (LXXIII.) There have been discovered at Euriage, not far 
 from Grenoble, the remains of an ancient fish-pond, the 
 borders of which were thickly incrusted °. When submitted 
 
 ° " In May 18 — , I fixed a stick on a mass of travertine covered with 
 water, and I examined it in the beginning of the April following, for the 
 purpose of determining (he nature of the depositions. The water was 
 lower at this time, yet I had some difficulty, by means of a sharp pointed 
 hammer, in breaking the mass which adhered to the bottom of the stick ; 
 
APPENDIX. 225 
 
 to examination, the incrusting matter dissolved eonipletely in 
 nitric acid, the ferro-prussiate of potash occasioned a slight 
 precipitate of the Prussian blue, and the muriate of barytes 
 also precipitated a small portion of the sulphate of barytes ; 
 whence it results, that independently of the lime, the frag- 
 ment experimented on contained also a little iron and sul- 
 phate of lime. 
 
 It is certain that the ancient cements, separated from in- 
 crustations, would not possess sufficient consistency to be cut 
 into thin plates, and afterwards take a polish. The thickness 
 of the coating of carbonate of lime which covers these ce- 
 ments is very variable, in some parts of the channel of the 
 aqueduct of Gard, it amounts to 0.05 m. (1.968 inches, Tr.) 
 
 (LXXIV.) The massive masonry of the ancient Bastile of 
 Paris could only be destroyed by mining ; a few years ago, 
 there were still to be seen at Agen, near the Gravier-gate, the 
 remains of a bridge which was thought to be old from the 
 hardness of its mortar: they were obliged also to use powder 
 to remove the remains of a pier which was in the way of the 
 promenade. This bridge, the construction of which the lovers 
 of the marvellous would gladly have referred back to the 
 Pelasgi, was built in 1180, in virtue of a charter of Richard 
 the First, king of England, and at that time ruler of a part 
 of France. The mortar of the bridge of Valentre, built at 
 Cahors in 1400, is in every respect similar, both as to the 
 quality of the lime, the proportions, and the size of the sand, 
 to that of an ancient theatre, the ruins of which are to be 
 found in the same town, six or seven hundred paces from 
 the river. Frequently repeated trials have shown only a 
 very slight difference between the resistance of antique and 
 old mortar ; and that difference is entirely in favour of the 
 latter. 
 
 it was several inches in thickness. The upper part was a mixture of 
 light tufa and the leaves of confervae ; below this was a darker and more 
 solid travertine, containing black, and decomposed masses of conferva; ; in 
 the inferior part, the travertine was more solid, and of a grey colour." — 
 Sir H. Davy, Consolations in Travel, p. 127. — Tr. 
 
APPENDIX. 
 
 NOTES ON CHAFltK XVII. 
 
 I XXV.)—* A detail of the facts alluded t >. i latiw 
 
 the induration of magnesia, will be found in Note '2 to Ap- 
 pendix V., and the following are the particulars of a similar 
 experiment with the powder of sulphate of lime (plaster of 
 Paris). 
 
 One hundred and thirty-six grams of the common calcined 
 sulphate of lime were diffused in water, and then pal aside 
 and allowed to set and harden. A few days afterwards, 
 the solid cake was removed, and exposed for several hours 
 to a steam heat, after which it appeared quite dry. It was 
 now weighed, and found to have increased IS grains, to 
 which an additional allowance of about 2 grains was due, 
 on account of the quantity dissolved in the water of im- 
 mersion. The cake was afterwards reduced to powder, and 
 a^ain exposed to the steam bath for about an horn, without 
 perceptible change, and it was then re -immersed, but found 
 to be incapable of again solidifying under water. 
 
 As this experiment was undertaken merely with the view 
 to ascertain the fact of the solidification of water during the 
 set of the sulphate of lime, no pains were taken to measure 
 the ratio of combination, in order to which, it would have 
 been necessary to have used ihc sulphate in the precise 
 condition of being entirely Greed from water, but at the same 
 time not over burned. Mr. Graham (Transactions of the K< >j a] 
 . ty of Edinburgh, Vol. XIII. p. 313) state>. that when 
 calcined at 270 : , it is entirely anhydrated, and is then capable 
 of recombining with two equivalents of water, which would 
 amount to 36 grains to 136 of the sulphate. When calcined 
 at too high a heat, it refuses entirely to recombine with it, 
 and is technically termed burnt stucco. — Tr. 
 
 \\VI — *The following particular of the experiments 
 alluded to, are extracted from my memoianda. 
 
 Experiment 1. — Two parti t Rajahmundry (.lay, (a white 
 
APPENDIX. 007 
 
 kind of pipe-clay, which did not effervesce, or lose weight, 
 by diffusion in nitric acid,) were calcined at a red heat, on 
 an iron plate, for half an hour, and then made into a stiff 
 paste with slaked rich lime, and set in six hours. 
 
 2.— Three hundred grains of the same calcined powder 
 were immersed at the same time, and kept under water for 
 twdvc hours. The water was then poured off, and the powder 
 dried at a steam heat, and weighed ; when it was found to 
 amount to 299.5 grains, the 0.5 gr. having been lost in the 
 process. Hence it is evident that, during the period of soli- 
 dification of the above cement, there was no absorption of 
 fluid to which to attribute it. 
 
 3. — And the following experiment proves, that the com- 
 pound also does not combine with, and solidify water during 
 its set ; (unless indeed, it be explained by supposing a union 
 so feeble as to be decomposed at a steam heat;) for 300 
 grains of a similar calcined clay, and 300 grains of well slaked 
 rich lime, after being made into a stiff paste, and immersed, 
 set in six hours, but were retained in the water for two days ; 
 after which, on being taken out, and dried at a temperature of 
 212° F., the weight was found to be 599 grains, a loss of one 
 grain having occurred in making the powders into paste and 
 mixing them. 
 
 4. — A quantity of the Rajahnmndry clay of Experiment 1. 
 calcined in powder, as in that experiment, was kept in water 
 for a month and eight days, and then taken out and made up 
 into a stiff paste with half its weight of slaked rich lime ; 
 and it was found on immersion to set in six hours as before. 
 
 5. — A mixture in stiff paste, composed of two parts of a 
 calcined clay powder, and one part of slaked rich lime, and 
 which set in three hours, was allowed to remain immersed 
 for six weeks. It was then taken out, reduced to fine powder, 
 sifted, and again made into a stiff paste and re-immersed. It 
 set the second time very slowly and imperfectly, but was 
 strong enough to bear the needle in six days. On first so- 
 lidilication it soiled the finger when touched, and though 
 possessing some cohesion as a mass, appeared to have but 
 
228 AlTKNDlX. 
 
 little intimate connection between its particles, as the surface 
 was easily destroyed by gently rubbing it. These detects, 
 however, were not permanent; they ceased to be conspicuous 
 alter the first month of immersion. — TV. 
 
 (LXXV1I.) This work had been completed, when M. Girard 
 de Caudcmberg, Engineer of roads, published, under the un- 
 assuming title of " Notice," a lengthened memoir on hydraulic 
 Him tars composed with arenaceous sands. The positive re- 
 sults made known in this memoir having been communicated 
 to us a long time since by the Author, are contained in the 
 preceding general compendium. We shall therefore confine 
 ourselves in what follows, to noticing some novel assertions, 
 which appear to us to be in manifest contradiction to well 
 established facts; and further, to the discussion of the degree 
 of probability of the theoretical inductions, by means of 
 which M. Girard has attempted to explain the solidification 
 of mortars and cements. 
 
 M. Girard says, in relation to cements of calcined amies, 
 compared with cements of arenes in the natural state, " that 
 after one year there was no appreciable difference between 
 the consistency of one and the other, excepting in the ex- 
 ternal parts, to the depth of one or two centimetres (.39 or .7S 
 inch, Tr.) ; that, consequently, the only advantage afforded 
 by calcination, is that of hastening, in a remarkable manner, 
 tin- period when the set of the bctons is completed. 
 
 The (aCt may be true, but the consequence which H. Gi- 
 rard deduces therefrom cannot be general, as it is founded 
 Only upon one particular ease of calcination. This En- 
 gineer, in fact, confined himself (page 25 of his Memoir) to 
 heating his arenes till they changed colour, in a sheet iron 
 < a/ior«//ii(j basin ; while he ought to have pushed the heat to 
 a strong incandescence, and kept the substance in that con- 
 dition for fifteen or twenty minutes; M. Girard would then 
 have obtained a highly eiienjclic artificial pouzzolana. instead 
 of B s/)///>ti/ energetic one, which his process afforded. 
 
 \\ e pass over in silence some minor details, tin- object of 
 which is to compare the price of the cubic metre of mortar 
 
APPENDIX. 229 
 
 of hydraulic lime and common sand, with that of the cubic 
 metre of rich lime and calcined arene; because an error or 
 exaggeration in a matter of that kind is not likely to be dan- 
 gerous, experience being always prompt in doing justice. 
 
 In the second part of his Memoir, M. Girard developes 
 Macquer's system, and attributes the excess of the resistance 
 of mortar over that of its gangue, to the necessity the aggre- 
 gate is placed in, to break with a jagged surface in lieu 
 of a plain and even one, which would be that which the 
 gangue would assume in its fracture, were it not mixed 
 with sand. 
 
 We have, in Chapter XVII., seen what objections we 
 have made to this hypothesis, which is not even sup- 
 ported by the first and indispensable experiments, whereby 
 we ought to endeavour to ascertain what the ordinary abso- 
 lute resistance of a prismatic solid, taken in the direction of 
 its axis, will be, when owing to any obstacles whatever, the 
 plane of its fracture is obliged to assume various degrees of 
 inclination towards that axis. 
 
 A Ye may make up for this deficiency, though imperfectly, 
 by saying, that from 0° to 45° the resistance remains sensibly 
 proportional to the area of surface. (This assertion is de- 
 lhid from numerous experiments made upon various condi- 
 tions of the rupture of solids of inextensible fibres, of which 
 experiments we submitted an account to the Academy of 
 Sciences, at its sitting of the 11th December, 1826.) This 
 being admitted, it is easy to satisfy ourselves with a lens, or 
 the naked eye, that the limit of 45° is far from being attained 
 by liif average inclination of the various faces exhibited 
 by the sections of fracture of the mortars of line sand; and 
 that in consequence, the development of the linear outline 
 taken from these sections, can never be in the ratio of 1414 
 to 1000 p , to that whieh would be exhibited by a matrix cm- 
 
 p 1.414, &c, is the square root of 2, which is the ratio of the hypo- 
 thenuse of a right angled isosceles triangle to its base ; and consequently 
 also, the ratio of the development of any number of these lines forming 
 an irregular jagged section, to the base they stand on, when their constant 
 inclination to it is 45°. — Tr. 
 
•2:30 aipknpix. 
 
 ployed without Band, and supposed to be stnoot/i and plane 
 in its fracture. Now, not only does the hydrate of hydraulic 
 lime not show a smooth fracture, hut the inequalities it pre- 
 sents seem to be pretty nearly of the same kind as those of 
 the mortars of fine sand. After this, how can we account for 
 the proportion of 3.6 to 1.0 afforded by experiment, between 
 the resistance of a good mortar of line sand, and that of its 
 matrix. 
 
 We shall then fail to explain the solidification of good 
 mortars, as long as we persist in denying to sand a very 
 notable influence upon the cohesion acquired by the hydrate 
 of hydraulic lime which envelopes it. This influence is 
 Its placed beyond a doubt by Mr. Petot's experiments 
 (App. LVI.). 
 
 In the latter part of his memoir, M. Girard discusses se- 
 veral facts relative to hydraulic Cements composed with rich 
 lime and clay, calcined, or in the natural state ; and arrives at 
 this conclusion, " that the solidification of mortars of ar- 
 gillaceous pouzzolana, depends upon the combination which 
 takes place, between the lime and the silica on the one hand, 
 and between the lime, the alumina, and the oxide of iron on 
 the other." 
 
 We shall refrain from following M. Girard through this 
 discussion, 1st, Because it does not comprehend all the known 
 facts respecting artificial pouzzolanas ; and amongst these 
 facts there are some very important ones which are far from 
 accommodating themselves to the hypothesis laid down. 2dly, 
 Because we consider the method adopted by the author, for 
 separating the silica from the alumina and oxide of iron in 
 ochreous clays, to be inadequate ; and that there is reason to 
 suppose that a combination of silica and alumina has been 
 constantly taken for silica alone, a circumstance which brings 
 to nought all the consequences drawn from so inexact a 
 Mipposition q . 
 
 <i M. Girard Bays (p. 07). that lie h pant* <! tin various days which lie 
 
 examined, into BJlica on the one band, and alumina and oxide <>f iron on 
 the other, by means of hydrochloric (.muriatic, Tr.) acid, and ammonia. 
 
APPENDIX. Q31 
 
 Wo agree with M. Girard, that it is impossible to disallow 
 a chemical action in the solidification of cements; but we 
 also think, that the question which has for its object the de- 
 termination of how, and between what principles, that com- 
 bination particularly takes place, is still to be solved. These 
 observations, and those which precede them, do not amount 
 to more than the researches of mere theory, and in no way 
 invalidate the important and positive facts made known by 
 M. Girard regarding the hydraulic properties of the arenes. 
 The title which this engineer has acquired to the esteem and 
 gratitude of builders, is therefore not the less deserved, nor 
 less secure. 
 
 Now clays treated by hydrochloric acid in excess, do not, even after many 
 days" digestion, part with more than a portion of their alumina. Some 
 even, scarcely yield 2 or 3 per cent, of it— Original Xvte. 
 
 THE END. 
 
TABLE S. 
 
TABLES. 
 
 ACCOUNT OF THE MANNER IN WHICH THE EXPERIMENTS 
 WERE MADE. 
 
 All the compounds, whether mortars or cements, (unless when 
 the tables expressly mention the contrary,) were kneaded stiff and, 
 as nearly as possible, to the same degree of consistency, by the aid 
 of a pestle. 
 
 The compounds intended for immersion were put into rather 
 deep than broad cups, sometimes of glass, sometimes of Delft, or 
 common glazed earthenware, and were covered with pure water 
 immediately after their preparation. 
 
 The compounds intended to harden underground, or in the air, 
 were either buried, or exposed under sheds, in the form of quad- 
 rangular prisms, having for section a rectangle of four or five cen- 
 timetres (1.575 in. to 1.97 in., Tr.) base; to 25 to 40 mille- 
 metres (0.98 in. to 1.97 in., Tr.) of height. 
 
 The quickness of set of the immerged compounds was measured 
 by the number of days which elapsed, from the instant of immer- 
 sion, to the moment when the surface of the substance was able to 
 bear, without any appreciable depression, a knitting needle of 
 0.0012m. (0.47 in., Tr.) in diameter, filed at right angles at one of 
 its extremities, and loaded at the other with a leaden knob, of 
 tlu- weight of 0.30 kil. (10 oz. 9 (lis. avoir., Tr.) 
 
 The relative hardnesses of the same compounds were generally 
 ascertained by the penetration* of a steel pin, very slightly tapered, 
 and terminated at its lower extremity, perpendicularly to its axis, 
 
 * We imagined at one time, that we could deduce from a certain number of 
 experiments given in our first work, "that tlie iquarei of the numbers cx- 
 preuing the depths <>f penetration of a needle impelled l>y a shock into any sub 
 stance, are reciprocally proportional t<> the relative or absolute resistances of 
 
FABLES. j; , 
 
 by a small plane circular surface of 0.166 cent. (0.0053 in., Tr.) 
 diameter. This pin, loaded with a weight of 6.9961 kil. (2 lbs. 3oz. 
 2£ dr. avoirdupois, nearly, Tr.), fell freely from a constant height 
 of five centimetres (1.97 in., Tr.). 
 
 Sometimes also, we made use of a piercer similar to that which 
 Perronet employed in measuring the hardness of stones ; the indi- 
 cations set down in the tables in that case make express mention of 
 this. 
 
 The abolute resistances of the prisms which were buried, or ex- 
 posed to the air, have been deduced from the relative resistances 
 of these same prisms by determining from a sufficient number of 
 experiments, and for the dimensions laid down, the actual value 
 assumed by the co-efficient represented by A in the formula of 
 Galileo. 
 
 Some Engineers are in the habit of delaying the immersion 
 of the trial betons, until they have allowed them to acquire a 
 firm consistency in the air. The results thus obtained are alto- 
 gether delusive, and cannot be compared with what takes place on 
 a large scale. 
 
 The experiments which have for their object the comparison of 
 the quickness of set of the various betons, require great care, and 
 are liable to causes of anomaly which we have it not always in 
 our power to avoid. Whatsoever efforts we may make to give 
 the same degree of consistency to the paste of the betons which we 
 wish to compare, it is extremely difficult at all times to obtain any 
 great degree of exactness, because, according to the process of 
 slaking, and the nature of the lime, and the ingredients, we are 
 obliged to make use of different quantities of water. Now it takes 
 very little, either in excess, or defect, to retard or accelerate the 
 set by a day or two. 
 
 We have not, moreover, been able to make all our experiments 
 in the same season ; so that some betons were immerged in the 
 violent heat of summer, and others at a mean temperature; a cir- 
 cumstance which must have differently influenced the quickness of 
 set. We have, in fact, had occasion to remark, that hydraulic 
 
 that substance;" and according to that principle, the depths of penetration were 
 transformed, by calculation, into numbers proportional to the resistances ; but 
 after the very judicious observations of If. Vauthier, the Engineer, we have 
 resolved upon returning to the numbers expressing the deptlis. 
 
236 TABLES. 
 
 mortars and cements, immersed in warm water at 40 degrees, 
 (101° Fahrenheit, TV.,) were capahle of supporting the trial needle 
 
 in a few hours, while corresponding ones kept in a flowing stream 
 at 7 degrees, (444° Fahrenheit, Tr.,) could not do so till after many 
 days. But these variable influences only sensibly affect the period 
 of first set, and when that period was required to be an essential 
 element of comparison in our researches, we took means to avoid 
 all the causes of error. 
 
 The measure of the relative resistances was also attended with 
 numerous difficulties, which depended principally upon the small - 
 ness of the prisms, and the unequal influence of the carbonic acid 
 of the atmosphere upon their different faces, according to their 
 particular position during the period of consolidation. 
 
 It was, besides, necessary to take into account the difference in 
 the dimensions of these prisms, not only because in each solid the 
 sum of the particles regenerated by carbonic acid is not pro- 
 portional to the whole bulk of the substance, but also because the 
 relative resistances are not, as was till now supposed, proportioned 
 to the relation between the square of the height of the section of 
 fracture, to the length of the prism under experiment. 
 
 We shall conclude by remarking, that when we compare the re- 
 sistances of mortars which fulfil various functions in a building, we 
 ought to have regard to the change of place and condition which 
 we cause them to undergo in submitting them to trials. Mortars, 
 and some stony substances which are able to absorb a certain 
 quantity of water, lose in such case, from \ to $ of their strength ; 
 whence it follows, that mortars buried underground, or those which 
 we take from the foundations of an edifice, to compare with others, 
 ought to be tried at once, if we wish to ascertain the real resistance 
 which they were capable of in the very spot they occupied. 
 
 The machines which were made use of in measuring the resist- 
 ances of mortars and cements, are represented, with explanatory 
 notes, in plates 2 and 3 placed after the tables. 
 
ATPENDIX. 
 
 237 
 
 TABLE No. I. 
 
 IN SUPPORT OF CHAPTER I. 
 
 Comparison of the Qualities of various Limes, with the Chemical 
 Composition of the Lime-stones furnishing them. 
 
 CONSTITUENTS IN 100 PARTS. 
 
 DESCRIPTION 
 
 OF THB INGREDIENTS. 
 
 LIME-STONES 
 
 FURNISHING RICH LIME. 
 
 Crystallized carbonate oflime. 100 
 
 Carrara marble Ion 
 
 Incrustations on the walls of 
 
 | the aqueduct of Gard 99.15 
 
 Fresh water lime-stone of Cha- 
 teau Landon, compact, yel- 
 lowish colour, slightly vesi- 
 cular 97.00 
 
 Lime-stone from Cartravers 
 (Cotes du Nord), lamellar, 
 of a blueish grey colour ... . 92.42 
 LIME-STONES 
 
 FURNISHING POOR LIME. 
 
 Sandv lime-stone of Calviac 
 (Diirdogne) 70.00 
 
 Coarse lime-stone of Dessin 
 ( Loire Inferieure) CI. 89 
 
 Lamellar lime-stone of Ville- 
 franche (Aveyron), colour 
 ochrcous 60.09 
 
 LIME-STONES 
 
 FURNISHING FEEBLY HY- 
 DRAULIC LIMK. 
 
 Coarse compact lime-stone of 
 Quilly (Loire Inferieure) .. 74.60 
 
 Tufa of \ toy, near the banks 
 of the Loire (Xievre) • ■ 90.00 
 
 Shelly lime-stone, from the 
 neighbourhood of Songy 
 (Nievre) (0.0(1 
 
 LIME-STONES 
 
 FURNISHING HYDRAULIC 
 LIME. 
 
 Secondary lime-stone from! 
 Nismes (Card), compact, 
 yellowish 82.50 
 
 Oehreous vellow lime-stone, of 
 
 Champ vert (Nievre) 82.63 
 
 Coarse lime-stone from Pom-; 
 peau i Isle el \ Maine), called; 
 
 " brnle-mort vert " i 7.5.03 
 
 Marly lime-stone, from the 
 hillock at I'oids de fer, on 
 the banks of the Loire (Xie- 
 vre) K.00 
 
 Marly lime-stone of Baraigue 
 (Lot), bituminous, blueish 
 grey colour N2.25 
 
 LIMESTONES 
 
 FUH N IM! I NO am N I NTI. Y 
 
 HVDHAUI.IC LIMK. 
 
 Castina (flux) from the plains 
 of Iiarree, near Sardy 
 
 (Yonne) '. 65.00 
 
 Marl; time-stone of Devay, 
 
 near Devise ( \levn0 i:n..-,ii 
 
 Marly lime-stone from the val- 
 ley of liiegco (N'ievre) 78.00 
 
 Semi-compact limestone of 
 
 Fortotot, near Bee d'Allier. 00.76 
 Vellow limestone, of the do- 
 main of Fleury , near IK-cise. 77.40 
 
 0.30 
 
 0.40 
 
 l.oo 
 
 1.25 
 
 i..-,r 
 
 3.10 
 
 3.40 
 
 5.00 
 0.00 
 
 4.00 
 
 7.00 
 
 -..Mi 
 
 8.00 
 7--'" 
 6.00 
 6JU 
 
 0.3.5 
 
 0.45 .... 
 0.(i0 
 
 3.67 
 
 2.00 
 
 3.10 
 
 4.90 
 6.20 
 
 8.40 
 
 11.(10 
 
 9.50 
 
 8.96 
 10.50 
 
 26.25 
 
 I .00 
 
 1 1. I'll 
 
 II JO 
 13.SS 
 
 
 24.75 
 20.00 
 
 3.00 
 2.91 
 
 7.44 
 30.30 
 
 17-40 
 
 0.40 
 1.1S 
 
 0.37 
 1.67 
 
 2.04 
 1.71 
 
 0.78 
 1.30 
 
 2.00 
 1.25 
 1.00 
 
 +6.00 
 
 indef. 
 do. 
 
 ndef. 
 do. 
 
 (lavs. 
 14.00 
 
 9.00 
 
 15.00 
 
 4.00 
 3.00 
 
 I 112 
 
 <• V M S ~ 
 
 6.00 
 
 none, 
 do. 
 
 do. 
 
 do. 
 do. 
 
 do. 
 do. 
 
 inches. 
 0.33<>7 
 
 0.4397 
 0.5472 
 
 0.2126 
 0.1988 
 
 4.0(1 0.2291 
 
 0.2382 
 0.2205 
 
 3.00 
 
 0.11R1 
 
 4.110 
 
 
 3.00 
 
 0.1181 
 
 
 0.0945 
 
 
 1551 
 
 REMARKS. 
 
 All the hydrates submit- 
 ted to experiment, had 
 a year's immersion. 
 
 Most of the analyses are 
 by myself, the rest are 
 due to Mr. Berthier, 
 Engineer in chief. 
 
 The written statements 
 of the experiments, 
 from which most of the 
 annexed results have 
 been extracted, arecer 
 titled bv the engineers 
 attached to the canals 
 of the Isle, Ranee, and 
 Loire. 
 
 * The iron is in the 
 state of carbonate, 
 
 ] The manganese is 
 in the state of car 
 bonate. 
 
 The needle penetrates 
 the hydrates by de 
 pressing their ' sub- 
 stance, without pio 
 during splinters. 
 
 The hydrates of emi- 
 nently hydraulic lime', 
 
 ■'iter under the 
 blow of the proving 
 needle. 
 
- 
 
 APPENDIX. 
 
 rABLE No. II. 
 
 iv sl'PPOKT Off CHAFT1 
 
 Compausom of mr. Habdnem am- Ar.-oiin Resistance of 
 Compounds, resulting from the Union of Water with 
 various Limes. 
 
 Absolute 
 
 an it ■ 
 Atoirdu- 
 
 
 s 1 : 
 
 = - - 
 
 Relative 
 
 of the 
 
 com- 
 pounds. 
 
 c - z ~^ 
 
 Specific 
 
 "of the 
 com- 
 pounds. 
 
 
 Of (he 
 
 lime-stones 
 which fur- 
 :-d the 
 time. 
 
 EM1XF.NT1.Y 11 VDRAU- i K , . ■ . ,. - 
 
 I 1 1 1 IMF J Slaked bv the first process. 
 
 FROM BODGAftDE (*A KN FT f^J» {'> *« "ZgfJ**- 
 BAH* J Ditto by the third ditto. 
 
 lbs. lbs. 
 
 |-172|1-212 
 
 i 
 
 lr2M 1 
 1-143 ) 
 
 
 THE SAMS. 
 
 FROM MONTELIMART 
 IDKOMEL 
 
 HYDRAULIC LIME. 
 
 FROM THE Ev 
 
 nnra iuarm. 
 
 | Slaked by the fir^t process. 
 < Ditto b\ the second ditto. 
 ( Ditto by the third ditto. 
 
 /Slaked by the first process. 
 Ditto bv t! . 
 ( Ditto bv the third ditto. 
 
 3JK» 
 14-1' 
 13-1 
 
 341 
 171 
 
 ; -34? 1-435 1 
 
 " 
 
 11-4 - .155 S 
 
 tup cwr ( Slaked bv the first process. 27-3 85-1 o-o48 (Kfid 1-103 - 
 
 rnonlmirTtiimTl -Ditto hV the second ditto. 1." - ■- 
 
 FROM SAINT CERE (LOT). ^ Dino by tht third ditto. - . " j ' 
 
 SLIGHTLY HYDRAULIC ( Slaked bv the first process. .to\ !i- ■ 
 
 LIME. < Ditto by the second ditto. 1. ' .' 
 
 from T). (Ditto bvthe third ditto. lte, 3] 
 
 I - ed bv the first process. 
 COMMON RICH LIME. -'Ditto bv the second ditto. 
 ( Ditto by the third ditto. 
 
 VERY RICH LIME. 
 
 /'. by the first process, 
 by the second ditto. 
 ( Ditto by the third ditto. 
 
 EMINENTLY RICH ( g*"* J? |J| e firsl I 
 
 i ,», «- ■ Ditto bv the second ditto. 
 
 L1,r - (.Ditto by the third ditto. 
 
 4D3 !■: KYVi i-C'f, ) 
 
 •ii5o 1-114 ;• 
 
 ." 
 
 f»5-5 129 i 
 
 - 462 Hi 
 61-5 154 
 
 27-2 tries 0-SWl 1-4935- 
 
 57-3 92-Sl>121 O16HM361-&H0 -5-535 OS96 
 
 The hardnesses were measured by the action of a piercer : the numbers 
 by which they are expressed, are reciprocally proportional to the depths 
 ot the holts, made by a certain number of revolutions under a constant 
 pressure. 
 
AIM'KXDIX. 
 
 V3«J 
 
 TABLE NO. III'.* 
 
 IN m-ppoht OF m U>TER VII. 
 
 Comparison of the Action of Muriatic Acid uroN Clays 
 taken in different conditions. 
 
 DESCRIPTION 
 
 THE CLAYS. 
 
 Portions of these principles dissolved by digestion 
 in Muriatic Acid, in loo parts of the Clay, taken. 
 
 Constituent principles of the Clays, 
 in 100 parts. 
 
 In the natural 
 state. 
 
 White plaatic clav of 1 ... , u , 
 Loupiac(Lot) (2) \f9UH 
 
 Grey effervescing clay of 1 ,, r , 
 Souillac (Lot) (3) J«M» 
 
 Brown ochreous clay, \ 
 found infiltrating the fis- t . } „ 
 sures of calcareous rocks i "' ' 
 ID J 
 
 Ochreous clay, of a hlood "» 
 colour, separated from [-43.40 
 an arene (4) \) 
 
 Red clay, colour of wine \ 
 dregs, from Have 
 (Nievre) (5) 
 
 28.67 
 
 ■42.60 15.96 24.64 
 
 Calcined in Calcined in 
 
 powder, exposed ' powder, in a 
 
 to the air. < close vessel. 
 
 8.00 . 2.85; .. .. 12.40 
 
 | j 
 
 12.02 6.00 6.46 2.13 18.20 
 
 35 .. 17-40 
 
 12.00 2.30! 13.86 . . | 15.00 
 
 8.80 !.?5 3.51 24.64 
 
 7.00 
 
 2 
 
 not made. 
 
 7.20 4.1: 
 
 not made. 
 
 3.00, 24-60 not made. 
 
 • Table No. III. will hi f mnd on the page following.— Tr. 
 
 >h2 
 
240 APPENDIX. 
 
 TABLE 
 
 -VPPoRT OK 
 
 Comparison of the Qualities of Hydraulic Cements, with 
 
 Constituent principles in \ik< parts of the Substances in the 
 natural state. 
 
 des< uftion of the 
 substances. 
 
 Very enekgetic Sib- 
 STAsa-. 
 
 Tarras from Andernac*. 
 tabling 
 
 Italian Pouzzolana, colour of 
 wine dregs, containing . . 
 
 Artificial Pouzzolana. result- 
 ing from the calcination, 
 in powder, of a brown; 
 ochreous clay. ( 1 ) contain- 
 ing ' 
 
 The same, from a plastic 
 white clay, (2) nontaining 
 
 The same, from a grey. 
 
 .tly effervescing clay, 
 
 (3) containing 
 
 The same, from a brown 
 ochreous clay, (4) contain- 
 
 ing 
 
 The same, from a red. very- 
 effervescent clay, (5) con- 
 taining 
 
 46.60 
 §2.00 
 
 42.00 
 CI. 00 
 
 43. C3 
 
 43.40 
 
 42.00 
 
 43.00 
 
 42.m; 
 
 Energetic Substances. 
 
 Ochreous clay separated by 
 washing from the arene of 
 Perigord. containing . . 
 
 Artificial Pouzzolana, result- 
 : from an ochreous day, 
 over-burnt, containing . 
 
 Slightly energetic 
 
 Sl'HSTANCES. 
 
 Clay, separated from the 
 arene I M I _nac (Dor- 
 
 <■'. containing 
 
 .rited boa the 
 I 
 
 of the Loire), contain 
 Pmnmiteof Kerg 
 ( Finisterre), of mediocre 
 quality, containing 00-80 
 
 l.VEKT SUBSTANCE*. 
 
 Quartzose sand .... 
 ■ 
 pavty fusion, containing.. 
 I large fun. 
 
 100.00 
 
 ; 
 
 20.60 
 10.00 
 
 28.07 
 31.00 
 
 32.90 
 
 20.00 
 
 15.96 
 
 28.40 
 28.67 
 
 24. GO 
 
 1. '...'( i 
 
 ! • " 
 
 13.00 
 
 15.00 
 
 12.33 
 
 9.29 
 
 I860 
 
 8.00 
 
 13.00 
 12.33 
 
 1100 
 
 10.40 
 
 
 2.16 
 
 24.04 
 
 3.00 
 1.96 
 
 38.60 
 
 5.00 
 
 12.80 
 
 4.05 
 
 11.00 
 
 
 16.94 
 
 
 8.00 
 
 •• 
 
 - 1 
 
 
 - 
 
 •• 
 
 880 
 
 ■• 
 
 15.00 
 
 •• 
 
 16.94 
 
 
 16.00 
 
 ■• 
 
 20.00 
 
 
 15.00 
 
 • • 
 
 .. 
 
 • The Alumina contains from three to four hundredths of Magnesia. 
 
APPENDIX; 
 
 No. III. 
 CHAPTER VII. 
 
 the behaviour of their ingredients in regard to Muriatic Acid. 
 
 2JI 
 
 Portion* of these principles dissolved' 
 
 by digestion in Muriatic Acid i. 
 
 12.20 
 9.00 
 
 17-40 
 12.40 
 
 18.20 
 
 15.00 
 
 5.60 
 11.40 
 
 r.oo 
 
 6.00 
 9.80 
 
 2.00 3.00 
 
 16.47 
 10.50 
 
 7.93 
 
 10.00 
 6.20 
 
 212 
 
 24-00 
 
 11.53 
 
 3.03 
 
 .-» 40 
 
 8.80 
 
 Behaviour of the Substances with 
 rich I. line. 
 
 Proportions of the 
 mixtures. 
 
 35 8 
 
 j x ; 
 
 9.40 
 5.60 
 
 2.00 
 
 2.00 
 1.00 
 
 2.00 
 2.00 
 
 2.00 
 
 2.00 
 
 2.00 
 
 §■- 3 
 
 as 
 
 9 » a 
 
 Solidification. 
 
 1.00 
 
 3.00 
 3.00 
 
 3.00 
 3.00 
 
 3.00 
 
 3.00 
 
 3.00 
 
 1.00 
 2.00 
 
 1.00 
 
 1.00 
 
 1.00 
 
 1 oo 
 1.00 
 
 l.on -joo 
 
 3.00 3.00 
 
 
 Days. 
 
 Inches. 
 
 8.00 0.0889 
 
 2.50 | 0.0728 ^ 
 3.00 • 0.0827 \ 
 
 1.00 
 2 50 
 
 2.00 
 
 2.50 
 
 1.00 
 
 3.00 
 
 3.00 
 3.00 
 
 3.00 
 
 2.00 
 200 
 
 9.00 
 
 18.00 
 6.00 
 
 17.00 
 
 Never. 
 Never. 
 
 0.0787 
 0.0984 
 
 0.0866 
 
 0.0984 
 
 0.1181 
 
 0.2405 
 0.2657 
 
 0.3555 
 04228 
 0.4018 
 
 Soft. 
 
 ■ 
 
 Splinter under 
 
 the blow. 
 
 Ditto. 
 Ditto. 
 
 Ditto. 
 Ditto. 
 
 Tlie needle 
 penetrates 
 without 
 splintering. 
 
 Ditto. 
 
 Ditto. 
 Ditto. 
 
 Ditto. 
 
 % The Sub-lances submitted to digestion in Muriatic And «crc in the slate <pecificd in thp 
 
 .";rM column. 
 
212 
 
 APPENDIX. 
 
 TABLE No. IV. 
 
 IN SUPPORT OK CHAPTER Vlll. 
 
 Comparison of various Artificial Polzzolanas with the Italian Pouzzolana, 
 Audenack Tarras, and Aquafortis Cement. 
 
 PROPORTION'S OK THE 
 
 ( KMKNTs PKKP ARKD 
 
 KKJM THK.M. 
 
 I't-LRIPTION 
 
 or THE 
 
 INGREDIENTS. 
 
 Rich ': 
 mej^urnl 
 
 in paste Ingredients 
 obtained In tlie 
 bv the state of 
 ordinary powder, 
 mode of 
 slaking. 
 
 Time 
 of set of 
 
 the 
 cement. 
 
 IVpre»ion 
 produced b\ 
 
 the blow of 
 
 the proving 
 
 needle, after , 
 
 a year's 
 
 immeuion 
 
 Observations. 
 
 Aquafortis cement of Paris LSI 
 
 Italian pouzzolana, colour wine dregs red •! H3 
 Audenack tarras L06 
 
 ARGILLACEOUS SUBSTANl 
 
 lALliXED IX POWDER EXPOSED TO 
 THE AIR. 
 
 Ochreous clay, d) deposited by infiltra- ) , )|f) 
 
 tion in the crevices of lime-stones, J- ., 
 
 calcined in powder ) 
 
 '"Vhreous clav, separated bv weshing from \ 
 
 a brown arene (4) ditto ". < * 
 
 Kn\r\e>cing clav from Bave (Nievret \ ., . 
 
 | - 
 } 2.1.1 
 
 ditto 
 Plastic refractory clav of Loupiac (2) 
 
 (Lot i. ditto '. 
 
 Plastic elav of Nicer-, ditto 
 
 -ciug clav from 
 
 Souillai ' i .* 
 
 Arene from ChatilkM] \ic\ re), ditto. . . . 
 
 ■ Lamothe (Lot), ditto 
 
 Psammite from Kcrgnal 
 
 ARGILI.ACEOLS SUBSTANl ES 
 
 (iL( I.VED IX rciUDER IX ILn.-E 
 --.•-LS. 
 
 Ochreous clav. cited (ll . . 
 Refractor] clay, cited (2) 
 
 1.IKI 
 
 240 
 
 2."<i 
 LOU 
 
 ARGILLAt EOUS SUBSTANCES 
 
 SloDtHATELV HBATED IN FRAC.MENTs 
 IX CONTACT WITH THE AIR. 
 
 Ochreous clay, cited (1) f [[]] 
 
 Pounded brick of the country, (Lot I -' .', '"^ 
 
 Plastic day, cited (2) .' };]" 
 
 Grey effervescing clav, cited (.1) •' '■'" 
 
 l i.mi 
 
 ARGILLACEOUS SUBST V.NCES, 
 
 AND OTi!KI>. rOWWMrWL* HEATED 
 
 IV t-r.Al.V 
 
 Ochreous clay, cited (1) 2.00 
 
 :.g clay, cited (3) 
 
 Common slate 2M0 
 
 Kernijinous sand-stone 2.mi 
 
 Basalt 
 
 ami 
 aim 
 240 
 
 3LO0 
 
 .(.(«l 
 
 aoo 
 
 3.i«i 
 
 aoo 
 
 aoo 
 
 ami 
 
 ami 
 
 aoo 
 
 ami 
 
 ami 
 
 aoo 
 
 8.00 
 
 ami 
 
 - 
 
 340 
 
 am 
 
 3ml 
 
 M0 
 
 ami 
 
 i 
 
 aoo 
 
 ."..mi 
 
 4.ki 
 440 
 
 moo 
 
 12.00 
 
 4.KI 
 
 - 
 
 _■ -1 .« • 
 
 Inches. 
 
 0.1102 
 
 o.i«27 
 0.0889 
 
 0-50 
 1.00 
 
 04649 
 
 j 
 
 2.50 
 
 • •■'•-! 
 
 LOB 
 
 0.1181 
 
 2.50 
 
 
 140 
 
 0.1299 
 
 2.00 
 
 0.(666 
 
 I. .Mi 
 LflO 
 
 0.1004 
 
 tumtf* 
 
 
 a 1653 
 
 IU1HM"! 
 
 O.lKJl 
 0.2m>i 
 O.IWI 
 
 AM these cements 
 j. splinter under the 
 
 • This experiment, 
 communicated by Mr. 
 Avril, Engineer, was 
 uied on a cement more 
 than a year old. 
 
 t The cements fur- 
 .ii>hed by these two expe- 
 riments were sensibly de- 
 I at their -ur- 
 the depth of 
 0-1UN8 to 0436 of aa inch, 
 rhej adhered to the 
 
 taining tlKin with such 
 
 :t it was MCCe- 
 
 - iry to reduce them to 
 
 powdet ti« v paratc them. 
 
 The cements of these 
 
 -do not splinter 
 odei the blow. 
 
 The commas indicate 
 4421 thai the surface was 
 
 i r able to beat the 
 0.4819 lccdle whuh i^ oaed to 
 
 i-ure the lime of the 
 0.6027 
 
 Niirr.— When the calcination i- puttied as h gh as thr ,, the ni ( ,rtars become (with 
 
 thecxieptioiiof the >!au i ccmplctch inert. 
 
APPENDIX. 
 
 243 
 
 TABLE No. V. 
 in support of chapter ix. 
 
 Comparison intended to show the Mutual Suitableness of the various 
 Limes, with the different Ingredients of Cements and Mortars. 
 
 WATER MORTARS, 
 
 Composed of eminently hydraulic lime, and quart 
 zose sand, or inert substances. 
 
 Eminently hydraulic lime of the valley of Rioges 
 (Nievre), with sand from the Loire 
 
 The same, from Baye (Nievre), with the sand of 
 the Loire 
 
 The sam«, from Vaux-Helles, near St. Prive, 
 (Nievre), and Loire sand 
 
 The same, from the marl of Devay on the Loire, 
 with Loire sand 
 
 The same, from Fertotot, near Bee d'Allier, with 
 Loire sand 
 
 The same, from Quenou (Isle et Vilaine), with 
 the quartzose sand of La Vilaine 
 
 The same, from Pompeau (Isle et Vilaine), with 
 the quartzose sand of La Vilaine 
 
 The same from Vivier (Ardeche), with the gra- 
 nitic sand of Dordogne 
 
 Proportions of the 
 Mixtures. 
 
 Lime in 
 
 paste 
 obtained 
 by the 
 ordinarj 
 mode of 
 slaking. 
 
 ( 100 
 
 I 100 
 101) 
 100 
 
 , loo 
 
 I 200 
 
 WATER CEMENTS, 
 
 Composed of eminently rich lime, and very ener- 
 getic pouzzolanas. 
 
 Eminently rich lime, and Italian pouzzolana. . . . 
 
 The same, with Audenack tarras 
 
 The same, with aquafortis cement 
 
 The same, with artificial pouzzolanas, obtained hy 
 calcining various clays, previously reduced to 
 powder, mean result of 14 experiments given 
 in Table No. 4. ) 
 
 WATER CEMENTS, 
 
 Composed of moderately hydraulic limes, and sim- 
 ply energetic pouzzolanas, or mixtures of inert 
 substances with very energetic pouzzolanas. 
 
 Moderately hydraulic lime, and tile-dust; mean re-, 5 100 
 suit of several experiments I 1 00 
 
 The same, with well-burnt clays ; mean result of \ loo 
 many experiments i ( 100 
 
 The same, with clays calcined in powder, tempered i .q*. 
 with one half of quartzose sand; mean of many, r iqq 
 experiments ) 
 
 Quart- 
 zose 
 sand. 
 
 100 
 
 150 
 
 100 
 
 150 
 
 100 
 
 150 
 
 100 
 
 150 
 
 100 
 
 150 
 
 100 
 
 150 
 
 100 
 
 150 
 
 100 
 
 150 
 
 Natural 
 or arti- 
 ficial 
 nou/.zo- 
 lana in 
 powder. 
 
 300 
 150 
 200 
 300 
 
 300 
 300 
 
 200 
 150 
 200 
 150 
 
 200 
 150 
 
 Time of 
 set of 
 the ini- 
 i nerved 
 mortar 
 
 or 
 cement. 
 
 3.00 
 2.50 
 8.00 
 2.50 
 
 I 1.44 
 
 ^2.5 
 
 ,50 
 
 3 00 
 
 Depres- 
 sion pro- 
 duced 
 by the 
 blow of 
 the prov- 
 ing needle 
 
 after a 
 year's im- 
 mersion. 
 
 Days. 
 
 Inches. 
 
 2.50 
 
 0.08GG 
 
 4.00 
 
 0.1161 
 
 4.00 
 
 0.1338 
 
 4.00 
 
 0.0728 
 
 8.00 
 
 0.0787 
 
 4.00 
 
 0.1315 
 
 3.50 
 
 0.1531 
 
 2.00 
 
 0.082G 
 
 0.1181 
 0.1181 
 0.0889 
 0.1102 
 
 0.1015 
 
 0.1354 
 0.1358 
 
 0.114!) 
 
244 
 
 APPENDIX. 
 
 TABLE 
 
 IN SUPPORT OK 
 Hydk M :.. . - v i> Ci -ilnts Compared, with 
 
 = - 
 
 1.:;:; .. 
 
 2.00 1.00 
 
 1.:,:; .. 
 
 1.80 2.00 
 
 2.00 
 
 ■2 1 1 i 
 l.iio 
 1.00 
 
 MORTARS AND CEMENTS 
 
 Of eminently rich Lime from Laurac(Lot). I ., ()1 , j ,,,, ) ,„, 
 The mean depressions for the 1st, 2d, and 
 
 3d processes of slaking, respectively, are 
 
 as follows : 
 
 In. In. 
 
 After the 1st year, 0.8888 0.1!l71 1 
 After the 2d year. 8.187* " 1578 0.1412 
 
 MORTARS AND I'EMESTS 
 
 Of the eminently rich Lime from Loupiac 
 
 {Lot). 
 The mean depressions for the 1st, 2d, and 
 3d processes of slaking, respectively, are 
 
 as follows : 
 
 In. In. In. 
 
 After the W .2086 0.1658 
 
 After the 2d year, 0.2784 0.1703 0.1376 
 
 Mortars and Cement- 
 Of common rich Lime. 
 The mean depressions for the 1 *t, 2d, and ] ^- 00 ¥ 
 3d processes of slaking, respectivelv, art- - J '' 
 
 as follow*: ■- 1 '' 
 
 to. to. in. 1.44 
 
 After the 1st year, IL2390 6.1786 6.1563 L.56 
 
 After the 2d year, 0JU68 6.1402 0.1268 L35 
 
 4 56 1.66 
 
 3.66 .. 
 
 4. .'hi .. 
 
 2.1C 1.00 
 
 2.16 1.00 
 
 1.50 .. 
 
 1.50 l.iio 
 
 2."25 j.un 
 
 1 00 
 
 1.00 
 1.00 
 
 1.00 
 2.00 
 
 Mortars and Cements 
 Of feebly Hydraulic Lime. 
 The mean depressions for the 1st, 2d, and 
 3d processes of slaking, respectively, are 
 
 as follows : 
 
 In. In. In. 
 
 After the let year, n..';:,;; 0.2018 0.1725 
 After the 2d year. 82467 0.1850 0.151 1 
 
 Cements and Mortars 
 
 Of Hydraulic and eminently Hydraulic 
 Lime. 
 
 Themeandt rthe 1*'. 2d, and 
 
 3d processes of slaking, respectively, are 
 Dowa : J 
 
 3.66 
 
 2 (Ml 
 
 :'..(>(• 
 2 16 
 2.16 
 1 44 
 1.50 
 1.50 
 
 1.1=11 
 
 1.00 
 
 240 
 
 1.00 
 1.00 
 
 1.(1(1 
 
 1.00 
 
 2.00 
 1.00 
 1.00 
 
 1.00 
 
 2.i»n 
 
 1.00 
 
 1.(1(1 
 
 I.imi 
 1.00 
 
 I.imi 
 
 I.imi 
 1.00 
 
 1.00 
 1.00 
 
 2.i hi 
 
 1.00 
 
 1.(1(1 
 
 After the 1st year. 0.1263 0.1330 0.1888 ,' 
 
 After the 2d vear, the experiments were 
 
 »ot complete. ^ ^ 
 
 2.(1(1 
 
 1.00 
 2.00 
 
 1.00 
 
 uoo 
 
 1.00 
 2.00 
 
 1.00 
 
 2.00 
 
 I.imi 
 2.(hi 
 
 1.00 
 
 2.(MI 
 
 I.IMI 
 
 2.O0 
 
 1.00 
 
 1.00 
 
 . . L.OO 
 
 l.Od 
 
 1 00 
 
 1 (III 
 
 not having )<ccn immersed in tl.c -.tint -(..uson,norconr*qucnll> , 
 i the Dumben which expreai the rapiditj 
 
 .iricil, alino-i arlmrarv prn|»<irlio!,. t.. Ihc lime, ill IHlhl III I lls hl llh mWT 
 :mi>, indicate rc>|>cvti\cly. the tue of the Untinary, lm Sjwmhmu— ; I 
 
APPENDIX. 
 
 245 
 
 No. VI. 
 
 CHAPTER X. 
 
 regard to the process of slaking made use of. 
 
 
 Time of 
 Set. 
 
 
 Depressions produced by the blow of the proving 
 needle. 
 
 
 After 1 year's immersion. 
 
 After -2 years' immersion. 
 
 o 
 
 I 
 
 s o 
 
 I 
 
 s 
 
 O 
 
 I 
 
 s 
 
 Days. 
 
 Days. 
 
 Days. ] In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 3900 
 
 101.00 
 
 7.00 0.4421 
 
 ).S330 
 
 >.1!)64 
 
 1.2555 
 
 0.2252 
 
 0.1878 
 
 9.00 
 
 17-00 
 
 26-00 0.2476 
 
 U499 
 
 I). 1610 
 
 0.1952 
 
 0.1204 
 
 0.1204 
 
 16.00 
 
 7-00 
 
 8.00 3004 
 
 1.2405 
 
 ►.2027 
 
 0.2177 
 
 0.1653 
 
 1.1378 
 
 4.00 
 
 4.00 
 
 4 00 0.1653 
 
 0.1653 
 
 I). 1010 
 
 1.1204 
 
 01204 
 
 0.1189 
 
 
 
 52.00 Soft 
 
 Soft 
 
 0.6527 
 
 Soft 
 
 Soft 
 
 0.6027 
 
 18.00 
 
 17-00 
 
 16.00 0.5311 
 
 0.1952 
 
 0.1653 
 
 0.4220 
 
 0.1728 
 
 0.1610 
 
 26.00 
 
 81.00 
 
 33.00 0.2102 
 
 0.1653 
 
 0.1653 
 
 0.1653 
 
 0.0976 
 
 0.0925 
 
 61.00 
 
 5200 
 
 60.00 0.3614 
 
 0.1803 
 
 0.1610 
 
 0.2854 
 
 0.1653 
 
 0.1354 
 
 33100 
 
 250.00 
 
 42.00 0.4752 
 
 0.3988 
 
 0-2177 
 
 0.3988 
 
 0.3161 
 
 0.1854 
 
 5.00 
 
 17-00 
 
 20 00 0.2634 
 
 0.1878 
 
 ). 172)1 
 
 0.2634 
 
 0.1653 
 
 0.1425 
 
 1.00 
 
 1.00 
 
 1.00 0.1499 
 
 0.1126 
 
 0.1126 
 
 U354 
 
 0.1051 
 
 0.1051 
 
 
 
 . , 
 
 Soft 
 
 Soft 
 
 Soft 
 
 Soft 
 
 Soft 
 
 Soft 
 
 
 
 •■ 
 
 do. 
 
 do. 
 
 do. 
 
 do. 
 
 do. 
 
 0.6027 
 
 14.00 
 
 2 00 
 
 4.00 
 
 0.2779 
 
 0.2102 
 
 0.1610 
 
 0.2252 
 
 0.1952 
 
 0.1425 
 
 73.00 
 
 7-00 
 
 31.00 0.2177 
 
 0.1653 
 
 0.1610 
 
 0.1610 
 
 0.1204 
 
 0.1204 
 
 321.00 
 
 2-00 
 
 12.00 0.3082 
 
 0.1878 
 
 0.1653 
 
 0.2405 
 
 0.1051 
 
 0.0976 
 
 7&20 
 
 3-00 
 
 37-00 0.2476 
 
 0.2252 
 
 01803 
 
 0.2405 
 
 0.1425 
 
 0.1539 
 
 3.00 
 
 2.00 
 
 3.00 0.2177 
 
 0.1728 
 
 0.1653 
 
 0.2177 
 
 0.1653 
 
 0.1499 
 
 2.00 
 
 1.00 
 
 1.00 0.1653 
 
 0.1126 
 
 0.1051 
 
 0.1204 
 
 0.1126 
 
 0.0976 
 
 
 . , 
 
 .. 1 Soft 
 
 Soft 
 
 Soft 
 
 Soft 
 
 Soft 
 
 Soft 
 
 •• 
 
 
 . . j do. 
 
 do. 
 
 do. 
 
 do. 
 
 do. 
 
 do. 
 
 15.00 
 
 16.00 
 
 15.00 '027 12 
 
 0.2476 
 
 0.1728 
 
 0.2633 
 
 0.2252 
 
 0.1031 
 
 24.00 
 
 24.00 
 
 32.00 0.1610 
 
 0.1499 
 
 0.1499 
 
 0.1204 
 
 0.1499 
 
 0.1122 
 
 39.00 
 
 7-00 
 
 6.00 0.3311 
 
 0.1275 
 
 0.1248 
 
 0.2854 
 
 0.1204 
 
 0.1204 
 
 33.00 
 
 16.00 
 
 22.00 0.2405 
 
 0.1952 
 
 0.1653 
 
 0.2252 
 
 0.1499 
 
 0.1303 
 
 2.00 
 
 7-00 
 
 7.00 0.2027 
 
 0.1803 
 
 0.1425 
 
 01354 
 
 0.1354 
 
 0.1275 
 
 4.00 
 
 7-00 
 
 8.00 0.1126 
 
 0.0901 
 
 0.0826 
 
 0.1126 
 
 0.0752 
 
 0.0752 
 
 113.00 
 
 103.00 
 
 150.00 0.4456 
 
 0.3160 
 
 0.2712 
 
 0.4220 
 
 0.3161 
 
 0.2626 
 
 65 00 
 
 63.00 
 
 77-00 ( 0.4421 
 
 03090 
 
 0.2712 
 
 0.3614 
 
 0.3082 
 
 0.2712 
 
 6.00 
 
 8.00 
 
 8.00 0.1315 
 
 0.1354 
 
 0.2283 
 
 0.1051 
 
 0.1161 
 
 0.1870 
 
 16.00 
 
 10.00 
 
 12.00 0.1511 
 
 0.1575 
 
 0.2401 
 
 0.1259 
 
 0.1299 
 
 0.2204 
 
 10.00 
 
 6.00 
 
 15.00 0.13:;:; 
 
 0.1480 
 
 0.2440 
 
 0.1023 
 
 ,0.1023 
 
 0.2323 
 
 7.00 
 
 6.00 
 
 8.00 0.1618 
 
 0.1834 
 
 0.2598 
 
 0. 1 346 
 
 0.1220 
 
 0.2362 
 
 12.00 
 
 6.00 
 
 15.00 
 
 1 i.l 220 
 
 0.1209 
 
 0.2161 
 
 0.1008 
 
 1 0.1 023 
 
 0.1889 
 
 3.00 
 
 3.00 
 
 4.00 
 
 0.1122 
 
 0.1102 
 
 0.1615 
 
 
 
 
 4.110 
 
 3.00 
 
 6.110 0.1181 
 
 0.1220 
 
 0.1575 
 
 
 
 
 3.110 
 
 2.00 
 
 5.00 0.1144 
 
 0.1161 
 
 0.1535 
 
 
 
 
 340 
 
 2.00 
 
 4.00 0.13.-, i 
 
 ,0.1417 
 
 0.1771 
 
 
 
 
 3.00 
 
 3.00 
 
 4.00 0.0826 
 
 1 
 
 0.0866 
 
 0.1417 
 
 
 
 
 in water of the same temperature, we ought not to attach much importance to the coin 
 
 clearly, the generality of the facts to be observed. The letters O, I, Sj plated over the- 
 slaking. 
 
246 
 
 AI II. MUX- 
 
 TABLE No. VII. 
 
 IX SUPPORT OF CHAPTER X. 
 COMPARISON OF THE RELATIVE RESISTANCES OF VARIOUS HvDRAlLlC MORTARS 
 
 and Cements, immerged in various States of Consistency. 
 
 H A M E .-. 
 
 Relative hard- 
 ness measured 
 very exactly 
 by means of 
 
 5 piercer, after 
 months' im 
 r-ion. 
 
 Lab A cement composed of 100 parts of the hydrate of rich lime slaked by 
 immersion, and 200 parts of energetic artificial pouzzolana, having been im- 
 merged, of a good consistency, and submitted to proof by the piercer, after 
 8 months, offered a resistance re}. resented by ]ihmi 
 
 2d. The same, having been allowed to acquire a stiff consistency in the air. 
 so that it was immersed quite in a bruised state, and without the least co- 
 hesion, gave under the same circumstances no more than 1 4:5 
 
 3d. The same, having been allowed to be altogether blanched, in very- hot 
 weather, so that it was immerged dry and pulverulent, without any co- 
 hesion, gave 333 
 
 4th. The same, taken in the condition N - -ui^ed and beaten up again 
 with additional water to the consistency No. 1, and immediately immerged, 
 gave • 1000 
 
 oth. The same, taken in the condition No. 3, but bruised and beaten up with 
 additional water BSteney Nft 1. and immediately immersed, gave 
 
 6th. The same, taken in the N <■ 2, but immerged with an en 
 lope, and retaining the consistency it had already arquired, gave 
 
 A ■ nd series of betons prepared with 100 parts of the hydrate of modern 
 hvdraulic lime obtained by the ordinary extinction, with 50 par- 
 get ic pouzzolana, and 100 pans of quartzose sand, gave, under the same 
 circumstances, and in the sair.e order respectively, as below. 
 
 Tims : 
 
 in ww 
 
 M 1 1 a 
 
 3d 128 
 
 4 tli 
 
 oth 1000 
 
 bib. 2000 
 
 Mortar composed of 100 parts of the eminently by- \ 
 draulic lime of the valley of Rioges ( Nierre), and < 
 1 « mi parts of the sand of the Loire, immerged . . / 
 
 Mortar, ditto, of the eminently hydraulic line of\ 
 
 the neighbourhood of Champ Vert (Nievre;, and< 
 
 ed / 
 
 Mortar, ditto, of the eminently hydraulic lime of J 
 Beauvoir (Nievre), and immerged j 
 
 -. ditto, of the eminently hydraulic lime of V 
 the domain of Fletiry, dependence of Gennancy J 
 (Nierre), and immerged / 
 
 Depressions 
 
 produced bv 
 
 Time the blow of 
 
 theproving- 
 
 ofset. needle, after; 
 
 years immer 
 
 sion. 
 
 Of a firm and duc- 
 tile consistency 
 ft con 
 
 tej 
 
 Of a linn and duc-i 
 tile consistency .! 
 Of a very nA con- 
 
 
 I I -m and duc- 
 
 tile consistency • 
 
 Of a very soft con- | 
 
 
 Of a firm and due-' 
 tile consistency . 
 
 Of a very soft om. 
 sistencv 
 
 Days. 
 3.00 
 7-00 
 3.00 
 7-00 
 3.00 
 
 SjOB 
 
 5.00 
 
 Inches. 
 0.1181 
 
 . _ 
 0.1 C53 
 
 - - 
 0.1.-. 15 
 0.2499 
 0.12)2 
 0.323G 
 
APPENDIX. 
 
 2J7 
 
 TABLE No. VIII. 
 
 IN SUPPORT OP CHAPTER X. 
 
 Hydraulic Mortars and Cements, compared with reference 
 to the deterioration which they undergo at their surfaces. 
 
 COMPOSITION 
 
 OK THE MORTARS AND CEMENTS. 
 
 Thickness of the deterio- 
 rated PARTS OF VARIOUS 
 
 Hydraulic Mortars, two years 
 old. 
 
 slaked lime in 
 paste. 
 
 2.oo 
 2.00 
 &66 
 8LO0 
 
 2.116 
 
 £66 
 
 2.00 
 &00 
 
 2.1 Ml 
 
 2.66 
 
 2.1 hi 
 
 &66 
 
 1. 00 
 1.00 
 2.00 
 
 2.1(0 
 I.IK) 
 
 1.00 
 
 1.00 
 
 1.IHI 
 
 1.00 
 
 1.INI 
 
 1.00 
 
 1 
 
 1.00 
 
 
 8.00 
 
 
 2.1 Nl 
 
 
 
 1.00 
 
 
 1.00 
 
 
 2.00 
 
 
 2.00 
 
 i. 
 
 . 
 
 •= o3 
 
 — qJ 
 
 s 
 
 
 >^~ 
 
 ^ 1 .— 
 
 
 
 
 rt .32 
 
 C 3 
 
 
 = E 
 
 c2 
 
 a - 
 
 i* 
 
 Indies. 
 
 Inches. 
 
 0.00 
 
 0.4330 
 
 0.00 
 
 0.3543 
 
 O.llll 
 
 0.3643 
 
 0.00 
 
 0.2362 
 
 0.00 
 
 0.1968 
 
 (MX) 
 
 1 1. 1 6?5 
 
 0.00 
 
 0.1575 
 
 0.00 
 
 0.1181 
 
 o.oo 
 
 0.0590 
 
 0.00 
 
 0.0000 
 
 0.00 
 
 0.0000 
 
 0.00 
 
 0.01 
 
 §=J 
 
 Inches. 
 O..V.12 
 0.3937 
 0.4330 
 0.2756 
 0.2362 
 0.2362 
 0.2161 
 
 Inches. 
 0-7086 
 0.6693 
 0.70m; 
 O.7O86 
 0.3543 
 (U346 
 0.2756 
 
 0.1181 I 0.2362 
 
 0.1181 0.1968 
 
 0.1575 
 
 0.0787 
 
 0.0590 
 
 0.0984 
 0.0590 
 0.0O00 
 
 Quickness of Set of various Hydraulic Mortars axd Cements, 
 Compared with the resistance acquired after a year's immersion. 
 
 NAMES. 
 
 Natural cement obtained from an argillaceous lime- 
 stone at Belle-ville, on the banks of the Loire 
 (Nievre) 
 
 Hydrate of lime, prepared from a sandy lime-stone 
 containing clay, calcined in contact with charcoal.. 
 
 Cement, containing loo parts of rich lime, ami 800 
 parts of an artificial pouzzolana, prepared by 
 slightly calcining a red effervescing clay, in frag- 
 ments. .' 
 
 Mortar, composed of It hi parts of the eminentlv 
 hydraulic lime of Chavance (Nievre), and 150 
 parts of the sand of the Loire 
 
 Natural cement, prepared from an argillaceous lime- 
 stone, found at Aaaigny, near Savigny (Nievre). . . 
 
 Mortar composed of 100 parts of eminently hydraulic 
 lime of Kertotot (Nievre), and 150 pacta Loire 
 
 ■and 
 
 Mortar, composed of 100 parts of eminently hydraulic 
 lime, prepared from a sandy lime-stone containing 
 clay, and loo pan sof Loire sand 
 
 Hydrate of eminently hydraulic lime, very poor, ob- 
 tained in the domain of Pont, near the rivulet of 
 on the banks of the Loire t \'ic\ rci 
 
 Mortar, composed of 100 parts of the eminently hy- 
 draulic lime of \ itry (Nievre), and 150 parts of 
 
 Loire sand 
 
 Mortar, composed of loo parts of the hydrate of 
 moderately hydraulic lime, from Garnat, on the 
 
 Loire, anil 150 part- of Loire sand 
 
 Cement, composed of loo parts of the hydrate of rich 
 lime, and 300 parts of the areneof Sancerre, on 
 
 the bank- of the Loire 
 
 ■ t" bo parts hydrate of very rich lime, and 
 
 ; - of the arene of Petreau (uironde) 
 
 Cement, of loo parts hydrate of very rich lime, and 
 
 .'ton part- of the ater.e of llerry, on the Loire. . . . 
 Hydrate of hydraulic lime, obtained from the lime- 
 stone of ('he vanes, near DecJse (Nievre) 
 
 Depression 
 
 produced 
 Time of set. by the blow 
 of the prov- 
 ing needle. 
 
 Observations. 
 
 Davs. 
 
 15.IK) 
 
 Inches. 
 0.1889 
 
 0.1771 
 
 11. 00 
 
 0.1181 
 
 9.00 
 
 0.11J3 
 
 8.00 
 
 0.004.3 
 
 C.CHI 
 
 0.0787 
 
 7.00 
 
 0.0433 
 
 8.1 K) 
 
 oastf 
 
 6.00 
 
 0.33C6 
 
 6.0<) 
 
 03288 
 
 1O0 
 
 
 i;.oo 
 
 0.2590 
 
 MQ 
 
 0.2 1-15 
 
 Note— The object of these compari-on- (which have been selected from experiments made with 
 great care), i- to show, that the time of sel is not always an exact indication of the future hardness 
 acquired by the immerged compounds. 
 
2 18 
 
 UThNDlX. 
 
 1 ABLE No. IX. 
 
 1\ >l]M'ORT OK UIAI'Tl.R I 
 
 Quickness ov Skt of various Cements, compared with the proportions, 
 
 and the hardness acquired after a year's, immersion. 
 
 
 Lime slaked by immersion, 
 and measured in powder, 
 
 
 
 
 Depressions 
 produced by 
 
 the blow of a 
 •.teel point 
 
 falling from a 
 
 : RF.R 
 
 not compressed. 
 
 
 Artificial 
 
 Time of set. 
 
 ; a Rs>. 
 
 
 
 pouzzolana. 
 
 
 Yen rich | Moderately 
 
 
 
 
 constant 
 
 
 quality. ! hydraulic 
 
 
 
 
 -hU 
 
 
 
 
 
 Pav.. 
 
 
 1 
 
 2.7" 
 
 1.00 
 
 1.00 
 
 19.00 
 
 047*2 
 
 2 
 
 2.00 
 
 1.06 
 
 1.06 
 
 16.66 
 
 04102 
 
 3 
 
 1.50 
 
 1.00 
 
 1.08 
 
 18.00 
 
 0.1988 
 
 4 
 
 1.00 
 
 1.00 
 
 1.66 
 
 8.00 
 
 0.) • 
 
 5 
 
 0.50 
 
 1.00 
 
 1.00 
 
 9.00 
 
 0.1' 
 
 1 
 
 2 7<> 
 
 
 2.66 
 
 B.66 
 
 0.1 . 
 
 f 
 
 2.06 
 
 
 2.06 
 
 
 0.123 
 
 3 
 
 1.50 
 
 .... 
 
 2.00 
 
 700 
 
 ■ 
 
 4 
 
 [.00 
 
 
 2.06 
 
 B.66 
 
 o.om>i 
 
 5 
 
 0..VI 
 
 
 2.00 
 
 17«hi 
 
 6.149 
 
 1 
 
 
 2.76 
 
 1.66 
 
 |j66 
 
 644M 
 
 I 
 
 
 2.00 
 
 1.00 
 
 l.HO 
 
 16.66 
 
 0.1. 
 
 9 
 
 
 1.56 
 
 1.00 
 
 l.OII 
 
 12.00 
 
 0.11 
 
 4 
 
 
 1.00 
 
 1.06 
 
 1.66 
 
 
 0.1616 
 
 5 
 
 .... 
 
 0.50 
 
 1.00 
 
 1.66 
 
 12.00 
 
 0.1913 
 
 1 
 
 
 2-76 
 
 
 2.66 
 
 1246 
 
 0.1401 
 
 2 
 
 .... 
 
 2.00 
 
 
 2.66 
 
 [246 
 
 0.1 
 
 3 
 
 .... 
 
 1.60 
 
 .... 
 
 2.66 
 
 1 040 
 
 o.l. 
 
 4 
 
 
 1.00 
 
 
 2.66 
 
 B40 
 
 0.123 
 
 5 
 
 .... 
 
 H .Ml 
 
 
 2.00 
 
 10.00 
 
 0.1] 
 
 The object of tliiN Table is to demonatrate,that the lime of M u ■ sufficiently 
 
 end indication of the future lienliif— of inun er g ed mortars and ben we 
 
 confine our comparison tu couipounds wmtaJning tlie same elements, in various 
 proportions. 
 
APPENDIX. 
 
 249 
 
 TABLE No. X. 
 
 IN SUPPORT OF CHXPTER XI. 
 
 The absolute Resistances of Mortars, compared with those of the 
 Hydrates of Lime constituting their gangues. 
 
 Lime in t 
 
 aste 
 
 
 obtained by 
 
 
 
 ■d 
 
 
 
 
 r. 
 
 
 
 
 a 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 >> 
 
 c 
 
 z 
 a 
 
 a 
 
 
 
 
 
 
 
 
 
 — -i 
 
 B 
 
 
 
 
 ti 
 
 
 
 
 
 
 
 Absolute 
 resistancea 
 
 
 = 2 
 
 si 
 
 SB 
 
 Oo i c = 
 
 MORTARS 
 
 OF 
 
 EMINENTLY 
 
 HVDR.M I JC 
 
 LIME. 
 
 MORTARS 
 
 OF 
 
 MODERATELY 
 
 A.VD 
 
 FEERLY 
 
 HYDRA t'LIC 
 
 LIMB. 
 
 Mortars 
 
 OF 
 
 RICH AND 
 
 VERV RICH 
 
 LIME. 
 
 Mortar of eminently hydraulic lime from Labour-"| 
 garde (Tarn et Garonne), composed of arbitrary - 
 proportions, -23 months old '.) 
 
 Ditto, compounded in the proportions corresponding 
 to the marimiim resistance 
 
 Mortar of eminently hydraulic lime from Montelimart 
 (Drome), compounded in arbitrary proportions, one 
 year old 
 
 Mortar of eminently hydraulic lime from Vivier 
 ( Ardeche), compounded the same, 1 year old 
 
 Mortar of eminently hydraulic lime from Baraigne 
 (Lot), compounded in the proportions corresponds 
 to the imiiiiilMii resistance, and 14 months old 
 
 Mortar of moderately hydraulic lime from Saint Cere 
 (Lot), compounded in arbitrary proportions, and 
 1 year old 
 
 Mortars of the feebly hydraulic lime of Cabessut at 
 Cahors, prepared in arbitrary proportions, and 28 
 
 old 
 
 2d 
 3d 
 
 months old 
 
 Mortars of the common rich lime of Souillac (Lot), 
 compounded in arbitrary proportions, 22 months old 
 
 Another 
 
 Mortars of the very rich lime of Lanzac (Lot), com- 
 posed of proportions corresponding with the maximum 
 
 resistance, 6 years old 
 
 Another 
 
 Another 
 
 1.50 
 
 1.50 
 
 1.50 
 
 1.80 
 1.50 
 
 1.50 
 1.50 
 
 1.50 
 
 1.50 
 1.5(1 
 
 0-50 
 1 .30 
 1.70 
 
 lbs. lbs. 
 70.45 123.8 
 73.30 140.0 
 
 73.30 165.40 
 
 ;k;.G4 i2<;.54 
 
 66.61 263.8!) 
 
 85.12 7H.71 
 
 108.75 34.16 
 oil. 21 53.23 
 
 111.02 39.85 
 46.25 49.07 
 
 155.86 64.90 
 122.41 6U32 
 
 134.50 85.40 
 
 Mortars compared with reference to size of the Sand made use of. 
 
 
 Proportions. 
 
 
 Absolute 
 resistances 
 per square 
 
 Lime 
 
 Fine 
 
 Coarse 
 
 Small 
 
 in paste. 
 
 sand. 
 
 sand. 
 
 gravel. 
 
 
 
 
 
 
 lbs. 
 
 1.00 
 
 1.80 
 
 
 
 165.40 
 
 1.00 
 
 
 1.80 
 
 
 134.50 
 
 1.00 
 
 
 
 L80 
 
 
 1.00 
 
 O.fXI 
 
 0.90 
 
 
 148.i>2 
 
 1.00 
 
 1.80 
 
 
 
 2»lf.89 
 
 1.00 
 
 
 1.80 
 
 
 177-20 
 
 1.00 
 
 
 
 l.HO 
 
 135.50 
 
 1.00 
 
 OlSO 
 
 040 
 
 
 222.04 
 
 LOO 
 
 1.80 
 
 
 
 84.68 
 
 LOO 
 
 
 1.80 
 
 
 65.47 
 
 LOO 
 
 
 
 i.80 
 
 48.IW 
 
 1.00 
 
 OlSO 
 
 OlSO 
 
 
 10&89 
 
 L00 
 
 2.i «> 
 
 
 
 41.00 
 
 1.00 
 
 
 B.00 
 
 
 54.6.'. 
 
 LOO 
 
 
 
 2.00 
 
 51.24 
 
 I.iip 
 
 1.00 
 
 i.do 
 
 
 47.32 
 
 Mortars of the eminently hydraulic lime of Labour-' 
 garde (Tarn et Garonne), 23 months old "1 
 
 Mortars of the eminently hydraulic lime of Baraigne 1 
 (Lot), 14 months old "J 
 
 Mortars of the moderately hydraulic lime of St. Cere' 
 (Lot), 1 year old .'...'. 'i 
 
 Mortars of the very rich lime of Lanzac (Lot)i --'.' 
 month- old , 
 
 Note — It must be recollected, that each result is the mean of many experiments, made with all the 
 exactness which this kind of investigation is capable of. 
 

 \\'\'\ SDIX. 
 
 1 ABLE So. XI. 
 
 1\ SUPPORT uF i BJlPTKR Al. 
 
 Mortars iakhn from varioi is BciLonros compared with Mo: 
 
 M WTFACTLRED FOR Exi'LRIMTNT. with the saiTK- LilVRs. 
 
 Absolute 
 
 of the 
 
 ; mortars 
 
 per square 
 
 inch. 
 
 Mortars of thk eminrvtly 
 HvDR.M'Lir Lime of 
 
 Mo.YTELINART. 
 Prepared by the ordinary proce**. 
 
 No. 1. Taken from a private 
 dwelling-house in Mo'iletimart. 
 compounded with fine sand in 
 pood pr oportions, 1:> yean old. 
 Taken from an ancient 
 toaer at Montelimart, com- 
 pounded iike the above, 110 
 fan old 
 
 No! .X Manufactured at souillar 
 for experiment, with tolerably 
 fine granitic sand, 12] months 
 old.. 
 
 Mortars of the emivf.vtly 
 HVDSULK Lima OF 
 Yiv 
 Manufactured hjp the ordinary proce**. 
 
 No. L Taken from the wall of 
 the rampart at Viviers, com- 
 posed with moderately fine 
 sand in pood prop irtions, age 
 unknown, but presumed to be 
 not less thai 
 
 No. 2. Prepared at SooJUac for 
 experiment, with moi 
 fine pranitic sand, 12 I 
 old 
 
 MoRTIRS OF THK moderately 
 Hvdrailic Lime of 
 Cab 
 Prr}« :uy process. 
 
 No. 1. Taken from the interior 
 of a private mansion at t ahors. 
 The mortar poor, the lime 1^ - 
 inp been drowned i 
 
 
 
 The same, situated be- 
 t nasi two bricks; had under- 
 gone a very rapid desirration . 
 
 The 'same, ha\ ing dried 
 in the ordinary wav: lx iter ma- 
 nufactured than the preceding 
 
 No. 4. The same, from the 
 foundations of th. same build- 
 inp. havinp underpone slow 
 desiccation. 
 
 No. '.. Taken from the bridpe of 
 Yalenlrc at C ahors, comprised 
 of coarse sand and pravel in 
 good proportions, 4m' year* old 
 
 lbs. 
 
 l-KU- 
 
 i3.fi; 
 
 Moarajts of the very rich 
 
 Limf. or I 
 Prejiared by tnc ■ •rautary proce**. 
 
 No. 1. Tiken from a private 
 house in Lanzac. The mortar 
 from the cornice, rati-. I 
 than rich, compounded with 
 tolerably fine pranitic sand. 
 
 tO \ears 
 
 The same, another frag- 
 ment 
 
 The same, another frag- 
 ment 
 
 The same, another frag- 
 ment 
 
 No. .". T.:ken from a < 
 composed like the pin 
 but poorer. At-. 
 ■ 
 
 ! 
 ■> :th the sarne sand, 
 and . i 
 
 Mortars of the vbrv bich 
 
 Limb of Lovpiac \Lot>. 
 Prepa r ed by the ordinary proce**. 
 
 No. 1. Taken from a private 
 mansion at Loup'ar. The 
 mortar rather poor tha • 
 composed with 
 pranitic sand. 17 years old 
 
 a fio,n the 
 of Loupiac. rather meagre than 
 rich, composed with pit sand. 
 ears old 
 
 less meapre 
 
 than tn* above 
 
 No. 4 Prepared at souillac for 
 
 experiment. with pranitic sand. 
 
 Age *> montht 
 
 Absolute 
 ■ rtan 
 
 Mortals of the model 
 
 ■ACXIC LlM I 
 
 BMH — (mwfimiarf). 
 Prepared by the ordinary proem. 
 
 Prepared at Souiilac for 
 -iment, wi h I 
 . :ir sand, 2o mvmth> 
 
 coarse 
 1 and pravel, 22 months 
 
 
 
 The same, with coarse 
 and fine sand mixed, 22 months 
 
 lbs. 
 
 17-<«3 
 
 21.77 
 16J7 
 
 ♦4.41 
 
APPENDIX. 
 
 251 
 
 TABLE No. XII. 
 
 I\ SI PPORT OF CHAPTERS XI. AM) XII. 
 
 Mortars compared in regard to their Proportions, and the Process 
 of Slaking made use of. 
 
 Proportions. 
 
 ABSOLUTE RESISTANCE OF THE .MORTARS, PER SnfARE IX< H. 
 
 Prepared from common rich lime, 
 after 20 months. 
 
 Prepared from eminently hydraulic lime, 
 after 14 month's. 
 
 ~ 7. S 
 
 1 ■ r 
 _• = = 
 
 = £ . 
 I S3 
 
 u &■ 
 
 Exposed to the air. 
 
 Buried under 
 ground. 
 
 Exposed to the air. 
 
 Buried under 
 ground. 
 
 o 
 
 I 
 
 s 
 
 O I 
 
 S 
 
 O 
 
 I S 
 
 O 
 
 I S 
 
 
 
 Dm. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. lbs. 
 
 lbs. 
 
 lbs. lbs. 
 
 100 
 
 
 103.19 
 
 54.i it 
 
 64.05 
 
 
 
 
 66.04 
 
 5940 44.55 
 
 149.17 
 
 141.63 125.26! 
 
 1(MI 
 
 so 
 
 44.41 
 
 34.16 
 
 41.28 
 
 2.7" 
 
 3.13 
 
 3.56 
 
 90.53 
 
 85.4" 79.71 
 
 161.13 
 
 153.72 
 
 131.66 
 
 100 
 
 60 
 
 3741 
 
 35.58 
 
 41.28 
 
 347 
 
 2.84 
 
 4.27 
 
 95.65 
 
 92.52 
 
 163.97 
 
 14840 
 
 137.21 
 
 too 
 
 7" 
 
 34.16 
 
 38,74 
 
 38.43 
 
 2.42 
 
 3.7O 
 
 3.56 
 
 120J3 10846 
 
 162.83 14:1.45 
 
 131.66' 
 
 too 
 
 
 41.28 
 
 4048 
 
 48.70 
 
 2.7" 
 
 346 
 
 6.12 
 
 157.71 
 
 148.02 9545 
 
 1G4.54 
 
 155.15 
 
 13340 
 
 100 
 
 no 
 
 42.70 
 
 42.7" 
 
 44.41 
 
 2.27 
 
 3.42 
 
 4-41 
 
 16947 
 
 15647 H7.43 
 
 169.81 
 
 141.63 
 
 136.64 
 
 too 
 
 too 
 
 
 4640 
 
 48163 
 
 813 
 
 3.27 
 
 4 27 
 
 174 28 
 
 18948 153.7s 
 
 17".8" 162.26 
 
 13849 
 
 
 110 
 
 
 46.40 
 
 42.7" 
 
 247 
 
 
 4.41 
 
 179.35 162.26 149.45 
 
 171.37 161.13 
 
 145.18 
 
 100 
 
 I2ii 
 
 39.85 
 
 55.51 
 
 48.3!) 
 
 2.42 
 
 2.7" 
 
 640 
 
 18447 17346 145.18 
 
 175.93 161.7" 
 
 146.61 
 
 100 
 
 ISO 
 
 41.2;: 
 
 58.07 
 
 51.24 
 
 2.27 
 
 844 
 
 4.27 
 
 191.87:179.35 165.11 
 
 175.".-: 
 
 153.01 
 
 148.02 
 
 100 
 
 140 
 
 41.2:: 
 
 66.33 
 
 ' , ; 
 
 2.27 
 
 3.42 
 
 4.13 
 
 211.80,196.43 1G2.42 
 
 174.22 
 
 160.84 
 
 157.99 
 
 
 150 
 
 3SL8S 
 
 63.76 
 
 58.07 
 
 2.42 
 
 4.41 
 
 4.13 
 
 239.13 20243 175.36 
 
 177.1 1 
 
 177.SO 148.02 
 
 100 
 
 ioo 
 
 4l.2;i 
 
 67.61 
 
 63.76 
 
 2.27 
 
 3.7" 
 
 5.41 
 
 243.24 236.28 199.2/ 
 
 174.51 15647 13643 
 
 100 
 
 17" 
 
 44.41 
 
 68.32 
 
 6440 
 
 2.42 
 
 3.70 
 
 5.41 
 
 25641 256.21 213.51 
 
 171.37 15647 13042 
 
 100 
 
 180 
 
 44.12 
 
 75.15 
 
 68.32 
 
 2.13 
 
 3.42 
 
 4.98 
 
 263.75 253J6 21046 
 
 17040 172.23 159.42 
 
 ioo 
 
 190 
 
 45.5.-) 
 
 81.13 
 
 81.98 
 
 1.71 
 
 5.41 
 
 5.12 
 
 261.62 24148 193.58 
 
 167.1:7 16349 145.13 
 
 too 
 
 - 
 
 48.39 
 
 78.28 
 
 78.57 
 
 1.14 
 
 5.12 
 
 5.41 
 
 24044 238.42 172.23 
 
 17040 16245 146.61 
 
 100 
 
 2lii 
 
 47-82 
 
 81.13 
 
 81.98 
 
 1-71 
 
 5.12 
 
 5.55 
 
 222.62 21940 16346 
 
 174.22 160.84 
 
 135.22 
 
 ino 
 
 B0 
 
 51.24 
 
 81.98 
 
 8648 
 
 1.56 
 
 4.41 
 
 5.41 
 
 213.51 I2O243 15P.42 
 
 177-64 
 
 142.34 
 
 136.64 
 
 100 
 
 230 
 
 51-24 
 
 7a 16 
 
 H5.4" 
 
 146 
 
 5.12 
 
 5.41 
 
 20447 172.23 150.88 
 
 189.17 
 
 145.89 131.66 
 
 1INI 
 
 
 51.24 
 
 75.15 
 
 i 
 
 l.:*; 
 
 3.42 
 
 5.55 
 
 198.14 176.5" 142.34 
 
 17943 
 
 146.61 
 
 13847 
 
 100 
 
 
 
 . 15.47 
 
 71-74 
 
 1.56 
 
 4.41 
 
 5.41 
 
 
 
 
 
 
 ioo 
 
 
 4748 
 
 
 
 1.42 
 
 643 
 
 7.54 
 
 
 
 
 
 
 
 100 
 
 170 
 
 
 
 
 I.2II 
 
 6.83 
 
 7.2.: 
 
 
 
 
 
 
 
 ioo 
 
 280 
 
 41.2:: 
 
 6446 
 
 8843 
 
 1.14 
 
 4.41 
 
 6.12 
 
 
 
 
 
 .... 
 
 
 ioo 
 
 290 
 
 
 55.51 
 
 
 1.28 
 
 2.7" 
 
 4.13 
 
 
 
 
 
 .... 
 
 
 Note.— The letter* O, I, S, indicate that the lime used wa« prepared by the Ordinary mode of 
 drtlnfc by Immersion, or by the Spontaneous method. 
 
jr t -j 
 
 APPENDIX. 
 
 TABLE XIII. 
 
 IN -IPPORT OF CHAPTERS XI. AND XII. 
 
 Mortars of rich Lime, fifteen months old, compared in regard to the 
 influence of manipulation. 
 
 PROPORTIONS. 
 
 Rich lime 
 slaked by 
 immersion, 
 and measur- 
 ed in paste. 
 
 Common 
 
 granitic 
 
 sand. 
 
 Absolute resistance of the mon-: 
 square inch. 
 
 Exposed to the air. I Buried under ground. 
 
 Remixed 
 
 Mixed in the with addi- 
 ordinary Itional water 
 manner. during five 
 months. 
 
 lbs. 
 
 hi 
 
 89..Q6 
 
 Remixed 
 Mixed in the with addi- 
 ordinary tional water 
 manner. during five 
 months. 
 
 lbs. 
 
 lbs. 
 
 - 
 
 Each of these results is the 
 mear. I menu, 
 
 made with thegreatest care, 
 and differing little from 
 one an 
 
 The mortars remixed, were 
 not operated on da: 
 from time to time, at in- 
 tervals of from 7 to 8 days. 
 
 The mortars buried under 
 ground were left in the 
 open air foT 2 n 
 nous to being subjected to 
 experiment. 
 
 Mortars, compared with reference to the consistency given to the mixture 
 
 of Lime and Sand. 
 
 PROPORTION?. 
 
 Eminently 
 
 hydraulic 
 
 lim'e.inpaste 
 
 obtained by 
 
 the ordinary 
 
 xtimtion. 
 
 Granitic 
 
 sand. 
 
 ISO 
 IM 
 
 Absolute resistance of the mortars at the age of 14 
 months, per square inch. 
 
 Exposed to the air. 
 
 Buried under ground. 
 
 Knead- 
 ed .-:.ff. 
 
 Knead- 
 ed nft. 
 
 lbs. 
 
 lbs. lbs. 
 
 7&B6 
 
 Knead- 
 ed stiff. 
 
 lbs. 
 
 Knead- 
 ed nft 
 
 Obsrrtatioss. 
 
 Hes 
 
 lfO.ll 
 
 lbs. 
 
 Each of the-, 
 
 | mean of a number of ex- 
 periments 
 
 Mortars, compared in regard to the influence of desiccation. 
 
 PROPORTION-. 
 
 -lance of the I 
 when ±.> montl - ire inch- 
 
 on. and • 
 m parte. 
 
 Whf .; first pi: 
 
 Comm^gnmitic afjer manu/act, 
 
 [tempera! art 
 Karenhcit *. 
 
 OCSEIO 
 
 Hydraulic \ u ,, 
 tine i '•" 
 
 Kceblv hv- \ , tt . 
 drauBc lime I " 
 
 Common 
 rich lime 
 
 uo 
 
 
 lbs. 
 44.12 
 
 lbs. 
 
 Each of these I 
 mean of a nuniN t 
 
 • The nmncntnc Mated m the original is l.V. «hie)i I hare reduced on the supposition that it is meant 
 to refer to tlu t eiitigrade thermometer ; IAm : Reaumur's scale would ome-pond to VC : of 
 
 licit, very ncarlv.— Tr. 
 
APPENDIX". 
 
 253 
 
 TABLE Xo. XIV. 
 
 IN SUPPORT OF CHAPTER XIV. 
 
 The absolute Resistance of VARIOUS Mortars, compared in regard 
 to the effect of condensation. 
 
 Ingredients. 
 
 Absolute resistance of 
 
 the mortars, per square 
 
 inch, at the age of 12 
 
 months. 
 
 Mortars buried un- 
 der ground 
 
 lbs. 
 32.74 
 37 31 
 17081 
 232.29 
 143.48 
 21&53 
 225.46 
 93.94 
 13.68 
 81 .92 
 133.23 
 :.4.r.'. 
 8S.11 
 95.65 
 80ti7 
 
 Various Mortars and Cements, compared in regard to their specific 
 gravity, and porosity. 
 
 NAMES. 
 
 Specific 
 
 gravity. 
 
 Weight of the 
 
 water absorb- 
 ed by imbibi- 
 tion, percubic 
 foot- 
 
 Various mortars of hydraulic lime, and quartzose, or calcareous sand, 
 subjected to condensation 
 
 Various mortars of hydraulic lime, and sand, or calcareous powders, 
 not compressed, but kneaded still. 
 
 Various mortars of hydraulic lime, and quartzose or calcareous sands, . 
 mixed thin 
 
 Various cements taken from ancient aqueducts. 
 
 2.031 
 I 
 
 1.960 
 1.945 
 
 1.028 
 1.885 
 1.873 
 
 1.8.54 
 
 1.789 
 
 1.753 
 
 1.747 
 
 1.692 
 1.689 
 
 1.317 
 1.279 
 
 1.987 
 
 1.940 
 1.760 
 1.609 
 
 1.516 
 1.472 
 
 1.409 
 
 1.384 
 
 i.;u:i 
 
 1.342 
 
 lbs. 
 
 io.no 
 
 111.74 
 12.12 
 12.WJ 
 12.24 
 12.24 
 13.55 
 12.18 
 14.03 
 15.68 
 1. "■.."».". 
 17-12 
 1 , ..Vi 
 23.3<; 
 22419 
 24.3U 
 !'-74 
 19.18 
 I9i99 
 IO80 
 22.1 '5 
 21.55 
 24.il 1 .) 
 20.1I3 
 18.90 
 23.(10 
 
 Norm, — Ii remlta from thtse companions, that the ccinent< are in general more permeable, than well 
 manufactured mortars of lime and sand. 
 
 *I 
 
254 
 
 AFrF.NPIX. 
 
 TABLE No. XV. 
 
 IN SUPPORT OF CHAPTER XVI. 
 
 Characters, Composition, and ABSoiXTe Resistances of some Roman Mortars 
 
 from the South of France. 
 
 MORTARS FROM LARGE OR M \S- 
 MVE MASONRY. 
 
 FROM THE ANCIENT VESCNA. 
 
 No. 1. Taken from the Amphitheatre. 
 
 2. Taken from the Baths. 
 
 3. Taken from the Tow tn •: 
 
 FROM CAHORS. 
 
 Xa 1. Taken from an ancient theatre. 
 P. Tin 
 
 2. From a temple. 
 
 3. From a Roman canal. 
 
 FROM NISMES. 
 
 No. 1. Taken from the Amphitheatre. 
 
 2. From the Temple of Diana. 
 
 3. From the Tour Magne (Turns 
 Magna). 
 
 NAMES. 
 
 Substances reduced p]w substances' 
 to imp^nable pow- ; ^^ in ^ | 
 der, and formn „,.»_;» i 
 
 principal m./ mamx. 
 
 dirty white, compos- 
 ed of lime only. 
 
 M atrix grey . form- 
 ed from a grey lime 
 only. 
 
 FROM THE AfiVEDrCT OF GARD. 
 
 No.l. Taken from the masonry. 
 P. Ditto. 
 
 FROM VIENVr. 
 
 No. 1. Taken from the Amp? 
 
 •J. From the drains (" egouts"). 
 
 FROM VXELLODIXIM. 
 
 (At Caj*iri,>. 
 No. 1. Taken from thick masonry. 
 
 MORTARS FROM \NC1ENTAQUE- 
 DICTS. REVETMENTS, FLOORS 
 
 OR PAVEMENT-. 
 
 FROM THE ANCIEN'T VSSl'XA. 
 
 No. 1. Taken from the aqueduct of the 
 baths. 
 
 FROM CAHORS. 
 
 No.l. Taken from the aqueduct of the 
 baths. 
 
 2. From the plastering of an ancient lime, and red brick in 
 gate, impalpable powder. 
 
 3. From a basin. 
 
 Composition of the Mortars. 
 
 lialHk 
 
 Observations. 
 
 The matrix red: Quartzose gravel. The mortar rich. l. 
 formedof while lime, from thesizeofapea coarsely amalgamat- 2. 
 and a verv small to that of a walnut, ed, in it a multitude 3. 
 quantity of red pout- of lumps of lime 
 
 zolana in impalpable -ible. 
 
 powder. 
 
 Matrix of a dim- Quartzose gravel. The mortar rich. 1. 
 white, formed of a from the sue of a better worked than 1'. 
 lime of the same pin's head, to that of the preceding, 
 colour. a hazel nut. taining no pouuo- 3. 
 
 .lana. 
 
 The matrix some- Quartzose and cal- 1 The mortar rich 1. 
 times grey, some- careous gravel, from land very badly mix- 2. 
 times red, formed of the size of a pea, to ed. a multitude of 3. 
 a white lime, and of that of a biggish ha- .lumps of white lime 
 
 
 . 53.5U 
 
 .1'iyjs 
 
 . 52J8 
 - 75L56 
 
 .16EL38 
 
 a small quantity of 
 red pouzzolana in 
 impalpable powder. 
 
 Matrix earthy, pre- 
 pared from lime and 
 a terreous sand. 
 
 zelnut. 
 
 were visible in it. 
 
 Quartzose gravel, of The mortar poor, 1. •- 87-82 
 the pretty nearly ill - mixed, full of 1". . . 45JE» 
 uniform size of a pea. lumps of white lime. 
 
 Matrix tolerably Quartzose gravel The mortars rich. 1. 
 homogeneous, of a of every dimension, tolerably wellrnixed. 2. 
 
 from that of a pea, to 
 a good sized hazel 
 nut. 
 
 Quartzose gravel of The mortar rich 
 every dimension. badlx worked, full of 
 lumps of lime. 
 
 The matrix red- Fragments of red The mortar verv 
 dish, formed of a brick of the size of a rich, badlv mixed", 
 white lime, and red|walnut, in small filled with" a multi- 
 brickdust in impal- quantity. iude of lumps at 
 
 pable powder. i white lime. 
 
 Matrix reddish, 
 composed of a white 
 
 FROM >M9MRS. 
 
 No. 1. Taken from the galkrics of the 
 Amphilh' 
 
 FROM THE AQfEDlTT OF GARD. 
 
 No.1. Taken from the revetment of the 
 aqueduct. 
 1'. The same. 
 
 from mm 
 
 N'n.l. Taken from an ancient mansion 
 
 2. Tii: 
 
 3. Pla ■■• 
 
 FR"v 
 
 No. 1. Taken from a '; 
 
 25-d2 
 
 i. .. esji' 
 
 A small quantity I The mortar rich, 1. ..115-86 
 of fragments of red mixedin a middling 2. . . 29.(4 
 the size of degree, filled with 3. .. <&64 
 a hazel nut. portions of lime of 
 
 a dirtv white. 
 
 The matrix grey, rragmentsofchar- The mor , al 
 composed of a whit. ■ ., pea. ralllv veii maA ^ 
 
 lime, and charcoal 
 powder. 
 
 The matrix whit- 
 ish , composed of 
 lime onlv. 
 
 Fragments of yel- The mortar verv l. .. 434B 
 low and red brick of rich. r. .11845 
 
 the size of a walnut. 
 
 Matrix reddish, ,_ Fragments of red 
 composed of lime, bnck a* big as a ha 
 
 and red bnck b 
 
 The matrix red 
 -cd of 
 lime, and red brick in 
 impalpable powder. 
 
 The mortars I 
 rably well amaUra- 2. 
 
 Fragm. 1 TV mortar tole- 
 
 bnck as big as a rably well mixed. 
 
 . 55.nfi 
 . 78-85 
 
 
APPENDIX. 
 
 255 
 
 TABLE No. XVI. 
 
 IN SUPPORT OF CHAPTER XVII. 
 
 Comparison of the Resistances of various Compounds, in regard 
 to Proportions, and the Size of the Bodies imbedded in the Sub- 
 stance constituting the Matrix. 
 
 1 
 
 
 
 
 
 Absolute 
 
 
 Number 
 of the 
 bricks. 
 
 Common 
 sand. 
 
 Coarse 
 sand. 
 
 Gravel. 
 
 Clay. 
 
 resistance 
 
 of the 
 bricks, per 
 
 squareinch 
 
 OBSERVATION'S. 
 
 
 
 
 
 lbs. aver. 
 
 
 1 
 
 
 
 
 1.00 
 
 58.07 
 
 
 2 
 
 1.00 
 
 . . 
 
 . . 
 
 1.16 
 
 18.93 
 
 
 3 
 
 1.00 
 
 
 
 0.96 
 
 14.94 
 
 
 4 
 
 1.00 
 
 
 
 0.76 
 
 12.95 
 
 Bricks Nos. 12, 13, 14, 15, 
 
 5 
 
 1.00 
 
 •• 
 
 
 0.56 
 
 11.67 
 
 and 16, were incapable of 
 
 C 
 
 1.00 
 
 •■ 
 
 
 0.36 
 
 8.96 
 
 supporting the very light 
 
 
 
 
 
 
 
 box into which the sand is 
 poured. 
 
 7 
 
 .... 
 
 1.00 
 
 
 1.16 
 
 4.55 
 
 8 
 
 
 1.00 
 
 
 0.96 
 
 3.56 
 
 
 9 
 
 
 1.00 
 
 
 0-76 
 
 3.27 
 
 
 10 
 
 
 1.00 
 
 
 0.56 
 
 0.43 
 
 
 11 
 
 .... 
 
 1.00 
 
 
 0.36 
 
 0.00 
 
 
 12 
 
 .... 
 
 
 1.00 
 
 1.16 
 
 
 13 
 
 
 
 1.00 
 
 0.96 
 
 .... 
 
 
 14 
 
 .... 
 
 
 1.00 
 
 0.76 
 
 .... 
 
 
 15 
 
 .... 
 
 
 1.00 
 
 0.56 
 
 .... 
 
 
 1G 
 
 .... 
 
 
 1.00 
 
 0.36 
 
 
 
 
 
 
 
 
 Plaster 
 
 
 
 
 
 
 of 
 
 
 
 
 
 
 
 Paris. 
 
 
 
 1 
 
 
 
 
 1.00 
 
 209.10 
 
 2 
 
 1.50 
 
 . . 
 
 
 2.00 
 
 120.0!) 
 
 
 3 
 
 1.50 
 
 
 
 1.00 
 
 K4.97 
 
 
 4 
 
 • ■ 
 
 1..-.II 
 
 , t 
 
 -.Mm 
 
 108.80 
 
 5 
 
 .... 
 
 1.50 
 
 
 1.00 
 
 59.64 
 
 
 6 
 
 .... 
 
 
 1.50 
 
 2.00 
 
 88.1 ;•_> 
 
 7 
 
 
 
 1.50 
 
 1.00 
 
 39.57 
 
 
 'r 2 
 

 APPENDIX. 
 
 TABLE No. XVII.— 
 referred to in notes, to article 3"9. and appendix xxxi. 
 
 Analyses of various old Mortars. 
 
 From a Dutch tomb 
 at Masulipatam . . 
 
 Ditto, ditto, another 
 specimen 
 
 Ditto, ditto, another 
 
 From a Mahometan 
 tomb 
 
 From a tomb on the 
 road from I 
 patam to Hydera- 
 bad '. .. 
 
 1-07 
 
 2.13 
 
 8. 
 
 9. 
 
 10. 
 
 11. 
 
 IS. 
 
 13. 
 
 11. 
 
 1.-.. 
 It 
 17- 
 
 [Another specimen 
 from the same . . . 
 
 Another do. from do. 
 
 Another do. from do. 
 
 From another tomb . . 
 
 From the same 
 
 From the Pagoda at 
 Tripatty 
 
 :tto. another 
 
 HMD 
 
 From a tomb at Gol- 
 condah, near Hy- 
 derabad 
 
 From a Roman tower 
 near Boulogne .... 
 
 Decayed plaster .... 
 
 Ditto, ditto, another 
 
 1.90 
 
 2.13 
 2.12 
 
 us 
 
 1.48 
 
 .Plastering from 
 public building in 
 .lipatam . 
 
 l.-o 
 
 Years. 
 120 
 
 120 
 
 120 
 
 200 
 
 200 
 200 
 
 200 
 150 
 Utf 
 
 400 
 
 400 
 
 200 
 
 1800 
 recent, 
 ditto. 
 
 4 b 
 
 53.2 
 
 7C.0 
 2G.0 
 
 115.9 
 
 38.5 101.0 
 
 I 160.0 
 153.0 
 
 17-0 
 85.0 
 
 997 
 
 110.9 
 
 110.4 
 
 19.7 
 
 IC.4 
 
 17" 
 
 174 
 13.8 
 
 33.9 
 
 29-1 
 17-1 
 15.G 
 
 G0.1 
 
 73.0 
 80.0 
 
 18&0 
 
 171-2 
 
 199.3 
 
 J06.5 
 12.n G4.5 
 
 l<t.2 
 10.3 
 
 30.0 
 50.0 
 
 11.9 CO.O 
 
 ',- 
 
 20.0 
 20.0 
 
 10.0 
 45.0 
 
 39.5 - 
 
 
 J." 
 
 ■ . 
 
 5.G 
 
 SjO 
 
 I I 
 
 7-3 200 
 
 8-0 300 
 
 OBSERVATIONS. 
 
 Sj8 
 
 350 
 400 
 
 7-C 
 
 3-4 
 
 - : 
 
 .. 1.18 
 
 l.f 
 
 11.1 
 
 60 
 80 
 
 100 
 
 100 
 
 ;■ 
 
 The insoluble 
 > m»n«r is of a 
 
 tuft. 
 
 BJ UN 
 
 4.4 1M 
 
 ni;,s> =L1 
 
 IIm 
 
 ble. 
 
1NDE X 
 
 A. 
 
 Page 
 
 Aberthaw lime, contents of, note 22 
 
 lime-stone, properties of, note 70 
 
 nature of its residuum, note 151 
 
 Absorption of carbonic acid of the atmosphere by lime ex- 
 posed to the air, art. 70 — 74 30, 31 
 
 of water by the Grecian pavements, art. 271 117 
 
 by rich lime, quantities of 168 
 
 experiments on the absorption of carbonic acid by mortars 172 
 the opinion that oxygen is absorbed by pouzzolanas during 
 
 the process of calcination not sufficiently established ... 183 
 absorbent property possessed by clays calcined in con- 
 tact with the air, after cooling 188, 189 
 
 Achard, M., theory of the solidification of mortars, art. 285... 121 
 Acids, action of, on the materials used in the composition of 
 
 mortar, art. 135 — 140 54,55 
 
 See Carbonic acid, Muriatic acid, Nitric acid, Sulphuric acid. 
 Adherence and cohesion, examination of the theory of, art. 
 
 290—314 126—139 
 
 experiments to ascertain the cause of cohesion in pastes, 
 
 note 127 
 
 definition of" adherence," art. 293 128 
 
 Age required for mortars to resist the effects of frost, art. 
 
 250, 251 104 
 
 " Aggregates," four remarkable cases presented by the theory 
 
 of, art. 295 129 
 
 probable theoretical consequences of the first case, art. 
 
 296 129 
 
 of the second, art. 302 131 
 
 of the third, art. 304 131 
 
 of the fourth, art. 306 131 
 
 Air, deterioration of lime by the action of, art. 60 27 
 
 influence of the contact of, in the manufacture of pouzzo- 
 lanas, art. 152 61.183 
 
258 INDIA. 
 
 Page 
 Air. — Mortars, or cements, capable of acquiring great hardness 
 
 in the open air, art. 1G3 do 
 
 of mortars constantly exposed to the air and weather, 
 
 art. 207—237 84—07 
 
 what limes are benefited or injured by such exposure, 
 
 art. 225 J>2 
 
 Air-furnace, description of, note 186 
 
 " Albaria Opera" of the Romans, notice of 175 
 
 Alberti, L. B., on the use of oil in ancient mortars, note 121 
 
 on the preservation of lime 109 
 
 Alcohol, effect of, in a paste of slaked rich lime, note 127 
 
 Alexandria, in Piedmont, manufacture of prisms at 207, 208 
 
 Alumina, nature of, note b 1 
 
 action of lime on, in the humid way 184 
 
 Antique mortars, reason for their superior durability, note b. Go 
 compared with those of medium age and 
 
 modern mortars, art. 2G8 — 283 114—123 
 
 result of M. John's analysis of 12-1, 12.3 
 
 analysis of various specimens, note 174, 1 75 
 
 hardness of, 202, 225 
 
 ►See Egypt, Greece, Romans. 
 
 Aqua fortis cement, composition of, art. 160 G3 
 
 comparison of various artificial pouzzolanas with the 
 Italian pouzzolana, Audenack tarras and aquafortis 
 
 cement 2 42 
 
 Aqueducts, mortar used by the Romans for the lining of, art. 
 
 277 110 
 
 Aqueous vapour. See Vapour. 
 
 Architecture, notice of Greek and Roman writers on, art. 
 
 272 118 
 
 Arencs, nature of, art. 101), 110 Ml 
 
 clay of, how acted upon by muriatic acid, art. L«M 55 
 
 deprive lime-water of its causticity, art. 141 5G 
 
 account of the use of as pouzzolanas 177 
 
 mixed with lime, form a good mortar for repairing sub- 
 aqueous works 177 
 
 in their natural state, act as pouzzolanas with rich limes 178 
 Sec 0'irard. 
 Argillaceous particles in fine sands, injurious effects of, art 
 
 214 80, 203 
 
 lime-stones, difficulty of calcining argillaceous 
 
 lime-stones by slow beat, art. 41 17 
 
 extensive use of, art. '2GG 1 18 
 
INDEX. 259 
 
 Page 
 
 Argillaceous lime-stones, kilns for the burning of 159, 160 
 
 substances, proportions of cements prepared 
 
 from 242 
 
 Artificial hydraulic lime. See Hydraulic lime. 
 Artificial marble. See Marble. 
 Artificial pouzzolanas. See Pouzzolanas. 
 
 Artificial products analogous to pouzzolanas, art. 124 49 
 
 Artificial stone. See Stone. 
 
 Arts, use that may be made of the hydrates of lime in, art. 99 42 
 
 Atmosphere. See Air, Carbonic acid. 
 
 Audenack tarras. See Tar r as. 
 
 Avril, M., discovery of the hydraulic properties of psammites 
 
 by 177 
 
 B. 
 
 Ballast, used in the manufacture of " concrete," note 100 
 
 Bastile, result of an analysis of mortars found at the destruc- 
 tion of, art. 285 124 
 
 Baye cement, analysis of 222 
 
 Beating, when useless, art. 99 4L 
 
 when it should be employed repeatedly, note f. 71 
 
 when a "beton" may be beaten up afresh, art. 199 .. .... 79 
 
 influence of, on the resistance of mortars in general, art. 
 
 233—200 106— 110 
 
 may be applied to mortar contained in a mould, art. 254, p. 106 
 
 how applied with effect, art. 255 106 
 
 different effects of, on various mortars, art. 256 107, 108 
 
 process of, used by the Romans, art. 277 119 
 
 Belidor, simplification of the box proposed by, art. 192 76 
 
 Berthier, M.,his method of analysing lime-stone 143 
 
 experiments by 150 
 
 his objections to the theory of Guy ton Morveau, art. 286, p. 125 
 his explanation of the solidification of hydraulic cements, 
 
 art. 813 137 
 
 " Beton," composition of, note b 20. art. 16.3, p. 67 
 
 extensive use of, in France, art. 46 20. 161, 162 
 
 hydraulic mortars may be employed in masses of, art. 
 
 1C0 42. 198 
 
 how its immersion is carried on, art. 193 76 
 
 should not be beaten when immersed, art. 196 77 
 
 ought not to be used while warm, art. 197 78 
 
 when it may be beaten up afresh, art. 199 79 
 
260 r.Nnf \. 
 
 "Betcn," sometimes supplanted by masonry, art. 200 
 
 Lyonese method of making 
 
 Bezoarah, notice of a mineral brought from, note 222 
 
 an excellent cement from, note 222 
 
 Biscuit, porous, experiment with broken fragments of, mixed 
 
 with lime, note 69 
 
 Black, Dr., his theory of the solidification of mortars, art. 28-3, p. 124 
 
 Bone-ash, deprives lime-water of its causticity, note .30 
 
 Boulogne stone, analysis of 291 
 
 Box. — Simplification of the box proposed by Belidor, art. 192, p. 70 
 Brard, M., method proposed by, to distinguish substances 
 
 liable to be affected by frost 210—218 
 
 Breccia, meaning of the term, note d 10 
 
 Bricks, number of, stuck together by Roman cement and pro- 
 jecting at right angles from the side of a wall, note Ill 
 
 employed unburnt in building by the Egyptians, art. 270, p. 117 
 fragments of, used by the Romans in their mortars, art. 
 
 270 119 
 
 always apparent in them, art. 279 121 
 
 experiments on, moistened with the solutions of the sub- 
 carbonate of potash 189, 190 
 
 value of M. Brard's process to discover if they are likely 
 
 to be affected by frost 218 
 
 Brick-work constructed with Parker's and Mulgrave's ce- 
 ments, the superficial weight it will bear, note f. 123 
 
 Bridge of Charles X. at Lyons, methods of fabrication and 
 
 immersion of mortar, for the foundations of 197 
 
 Bridges, effect observed under the arches of, note e 38 
 
 process of the Romans in laying the foundations of, art. 
 
 274 119 
 
 artificial hydraulic lime used for the foundations of, art. 
 
 46 ., 20. 161, lea 
 
 Bruyere, M., experiments upon artificial pouzzolanas 187 
 
 Builders, guide for, in the choice of lime-stone, art. 4 3 
 
 opinions of, as to the efficacy of oxide of iron, in- 
 validated by facts 183 
 
 Burgundy Canal, materials used in the works connected with, 
 
 art. 200 113, 156 
 
 Burning. See Calcination. 
 
 '• Burnt stucco," explanation of the term 226 
 
 C. 
 
 reoua incrustation;, observations upon some 224 
 
1NM A 201 
 
 Page 
 
 Calcareous minerals and the limes they furnish, art. 1 — 24. 1 — 12 
 
 tests to discover, art. 1 1 
 
 what proportion of clay in, renders them unfit 
 
 to he converted into lime, art. 201 Ill 
 
 history of. 142, 14JJ 
 
 analysis of. 140 
 
 sands, nature of, art. 105 44 
 
 See Sands. 
 Calcination of lime-stone in the large way, art. 2-3. 45, p. 13 — 19 
 conditions to render it as easy as possible, art. 20 — 31, p. 13 — 15 
 
 different kilns made use of, art. 32 — 38 15, 10 
 
 time required for, art. 40 17 
 
 average quantity of combustibles required for the com- 
 bustion of a cubic metre of lime, art. 40 17 
 
 difficult calcination of argillaceous lime-stones by slow 
 
 heat, art. -41 17 
 
 irregular action of the coal-kiln by slow heat, art. 41, 
 
 42 17, 18. 159 
 
 influence of a slight calcination in the manufacture of 
 
 artificial pouzzolanas, art. 161 61 
 
 effects of, on compound lime-stones 150 — 152 
 
 influence of aqueous vapour on 1.33 
 
 fact relative to calcination in a close vessel 153 
 
 consequence of the imperfect burning of lime-stones ; 
 
 contradictory experiments on the subject 154 
 
 experiments upon the different quantities of combustibles 
 
 used in 157 
 
 improvement which takes place in the burning of lime 
 with coal, by very slight modifications in the manage- 
 ment of the fire and the distribution of the combustible. 158 
 by kilns with alternating fires for the burning of argilla- 
 ceous lime-stone ; manner of using them 159 
 
 reverberatory furnace proposed for the calcination of 
 
 pouzzolanas 180 
 
 Calcined sulphate of lime. See Plaster of Paris. 
 
 Canals, the artificial limes used in, art. 46 20 
 
 materials used in works connected with, art. 200.... 113. 101 
 
 kilns employed to burn lime for 157, 158 
 
 " Cancan " importance of this class of Indian calcareous mi- 
 nerals, note 12 
 
 Carbonate of lime, dissolved by water containing carbonic 
 
 acid, note e 38 
 
 of magnesia, extensive beds of, found in the south of India 147 
 
- - INDhX. 
 
 I 
 
 Carbonate of magnesia, found to be valuable as a cement 147 
 
 analysis of 148 
 
 its use as a stucco 148 
 
 experiments upon, after calcination... 149 
 
 effects of different processes on. 153. 1J I 
 
 Carbonic acid, nature of, note a 1 
 
 r<. -absorbed by lime exposed to tbe air, art. 7<» 30 
 
 time required for this, in rich and hydraulic limes, art. 70. 30 
 
 proportion of, in lime, art. 70 SO 
 
 its effects on hydrates of lime, art. 82 — 86 35 — 38 
 
 in the atmosphere, increases the hardness of certain 
 
 bodies, art. 86, par. 2 38 
 
 augments the hardness of hydraulic limes, art. 86, par. 4. 38 
 the solidification of mortars attributed to the slow and 
 successive action of the carbonic acid of the at- 
 mosphere, art. 285 124 
 
 this opinion controverted, art. 285, 286 1 25 
 
 defended, as to mortars which do not " set," note 125 
 
 experiments on the absorption of, by mortars 172 
 
 table of the depth of penetration of, into different mor- 
 tars, after exposure to the air for various periods 173 
 
 proportion of, in small pieces of hydrate of lime exposed 
 
 to the air for 8 years 174 
 
 quantity of, in various old cements 175 
 
 in cement between 3 and 4,000 years old, note 175 
 
 Caskets and snuff-boxes made by the Italians, of the same 
 
 material as the ancient Roman cement, art. 278 120 
 
 Casts. See Moulding. 
 
 Cements. — An excellent water-cement, note t 11 
 
 commonly used in England unslaked, note 22 
 
 contents of various, note 22 
 
 directions for producing a cement similar to the Roman, 
 
 note d 23 
 
 matters improperly so called by builders how obtained, 
 
 art. 157 01 
 
 composition of aquafortis cement, art. 160 63 
 
 the goodness of, not always indicated by the rapidity of 
 
 the "set,"' art. 205 82 
 
 an excess of rich or slightly hydraulic lime in a cement 
 
 retards its •• set," par. 1 83 
 
 what mo unction " arc best calculated to hasten 
 
 the r. 2 83 
 
 continuance of the progress of certain cements, par. 3... 83 
 
INDEX. 263 
 
 Page 
 Cements — the relations in respect to " hardness " deduced from 
 
 comparison of the three modes of slaking, how modi- 
 fied by time, par. 5 83 
 
 subject to the constant influence of a damp soil, art. 238 
 
 —242 98—101 
 
 intended for under-ground masonry, how they are to be 
 
 used, art. 242 99 
 
 method of augmenting their " adherence," art. 242 99 
 
 of the vicissitudes to which they may be exposed, and 
 
 the consequences, art. 243 — 252 102 — 105 
 
 of rich lime with " inert " sands, become decomposed in 
 
 the water, art. 247 103 
 
 of rich limes, resist frosts but imperfectly, art. 248 103 
 
 cause of the speedy decay of, in India, note 103 
 
 Of natural cements, art. 261 — 267 Ill — 113 
 
 when calcareous minerals furnish a natural cement, art. 
 
 261 Ill 
 
 difference in the "set" of, art. 262 Ill 
 
 defects in, art. 262 Ill 
 
 adhesion of such as dry in the open air, note Ill 
 
 proof of the excellence of Roman cement, note Ill 
 
 great consumption of, in London, art. 263 112 
 
 recently found in Russia and France, art. 2G4 112 
 
 cements known 2,000 years ago, art. 268 115 
 
 how employed by the Egyptians, art. 269 116 
 
 by the Greeks, art. 271 117 
 
 by the Romans, art. 277 119, 120 
 
 table extracted from the analysis of various cements, 
 showing the relative proportions of lime, sand, and 
 
 carbonic acid contained by them, note 137 
 
 analysis of the Baye cement 222 
 
 of a cement used in the Madras Presidency, note 222 
 
 comparison of the qualities of hydraulic cements with 
 the behaviour of their ingredients, in regard to mu- 
 riatic acid 240, 241 
 
 See Hydraulic lime, Lime, Mortars, Pouzzolanas, Stucco, 
 Water cements. 
 Chalk mortars, injurious to keep them in a damp state, note g. 95 
 Chaptal, Count, discovery of the unequal manner in which 
 
 pouzzolanas behave in respect to sulphuric acid — 179, 180 
 result of his experiments on the ochreous clays of Lan- 
 
 guedoc 182 
 
 " Chaux carbonatee sacchaioide," nature of, note e 2 
 
INl'fcX. 
 
 • 
 
 Chemical affinity, opinion that it may act a part in the soli- 
 dification of good mortars, art. 2>'.0 125 
 
 this opinion controverted, art. 280 125 
 
 its importance in hardening mortars, note 13*2 
 
 has no effect in the setting of plaster of Paris, and other 
 
 cements, note 1 32, 133 
 
 opinion that lime in cements of natural or artificial pouz- 
 zolanas, as well as in cements formed with the uncal- 
 cined psammites and arenes, enters into chemical com- 
 bination with these substances, art. 314 13<5. 185 
 
 this opinion confirmed by experiments, note 138, 139 
 
 and by the observations of General Treussart, note 131) 
 
 Chemical analyses, mode of reducing the results of, into tech- 
 nical language, note 210, 211 
 
 Chemical combination. See Chemical affinity. 
 
 Chemical comparison of various old mortars 21') 
 
 Chemical constitution of the various limes, art. 21 9 
 
 I ..ical equivalent, note c 14 
 
 Chemical methods of recognizing the ingredients of mortars, 
 
 art. 141— 143 50, 57 
 
 of appreciating the qualities of lime-stone 143 
 
 Cheops, Pyramid of, the mortar found there similar to the 
 
 present, art. 208 114 
 
 analysis of it 114—110, note; l'o,;wtc; 222—224 
 
 Chill, effect of, in slaking lime, art. 59 27 
 
 Chunam, Madras, mode of preparing this stucco, note x 170 
 
 Cinders of coal and turf, sometimes form an "energetic" 
 
 pouzzolana, art. 158 03 
 
 but they are sometimes "inert," art. 158 03 
 
 Cisterns, mortar used by the Romans for the lining of, art. 
 
 -'77 119 
 
 Clays. — Basis of plastic clays, note b 1 
 
 kind for preparing artificial lime, art. 51 22 
 
 nature and classification of, art. 113 — 117 47, 48 
 
 notice of a useful clay, note a 53 
 
 action of muriatic acid on, art. 138 ■'»■'> 
 
 deprive lime-water of its causticity, art. 141 50 
 
 will produce "a very energetic"' pouzzolana, art. 153, 
 
 and note 01 
 
 what proportion of, in calcareous minerals, prevents them 
 
 from being converted into lime by calcination, art.2Gl,p. Ill 
 criterion to discover the proper proportions of, in lime- 
 stone 144 
 
INPF.X. ( ;5 
 
 Ways. — A mistake that clays are more easily acted upon by acids 
 when in their natural state, than after any degree of 
 calcination 100 
 
 result of experiments on ochreous clays 182 
 
 phenomenon observed in clays calcined in powder on me- 
 tallic plates heated to redness 103 
 
 effect produced by mixing clay and lime, when each is in 
 a state of pulp jg^ 
 
 on the conversion of, into artificial pouzzolanas 187 
 
 experiment to prove that clays calcined in contact with 
 the air do not absorb any gas .187 
 
 when calcined in a close vessel, not acted upon by acids to 
 the same degree as those calcined in the air 188 
 
 when calcined in contact with the air possess, after cooling, 
 an absorbent property 188 igg 
 
 research into the influence of the admixture of pure pot-' 
 ash or soda with the clays previous to their calcination, 
 in reference to the energy of the artificial pouzzolanas 
 P roduced 189, 190 
 
 table of facts observed in reference to cements prepared 
 from two kinds of clay, calcined in different ways 189 
 
 experiments with bricks of, moistened with solutions of the 
 sub-carbonate of potash 109 190 
 
 fatal influence of, in mortars exposed to the weather .... 203 
 
 account of various experiments with Rajahmundry 
 c ' a y 226 228 
 
 comparison of the action of muriatic acid upon clays 
 
 taken in different conditions 039 
 
 Coal, bulk of, burnt to produce a given quantity of lime, 
 
 art ' 44 18 
 
 refuse of the combustion of, used as an ingredient in 
 
 mortar, art. 124 50 
 
 Coal-dust, its use in cements, note k , 154 
 
 Coating used to guard the cement of the Eddystone light- 
 house, note k 
 
 Cohesion of pastes, experiments to ascertain the cause of, note. 127 
 See Adherence. 
 
 Colours of the various limes, art. 19 0. 143 
 
 of the Roman mortars, art. 276 1 1 9 
 
 results of experiments as to the colour of limes, note e. 14G 
 a clearer colour produced by the ordinary mode of extinc- 
 tion in certain cases Kj9 
 
 effects of different modes of extinction 109 
 
_>«;.; inm.x. 
 
 Pafir 
 
 Combination of materials necessary to produce mortars or 
 cements capable of acquiring great hardness in damp 
 
 situations, art. 109 04 
 
 of calcareous mortars and cements subjected to the 
 constant influence of a damp soil, art. 238 — 242 ... 98 — 101 
 Combustibles. See Fuel. 
 
 Compositions for the protection of stucco from the weather.... 212 
 Compounds, comparison of the resistances of various com- 
 pounds in regard to proportions and the size of the 
 bodies imbedded in the substance constituting the 
 
 matrix 256 
 
 terete," meaning of the term, note b 20 
 
 general use of in England as a substratum for dangerous 
 
 soils, note 100 
 
 nature and preparation of, note 1 00 
 
 composition of the " concrete" used in and near London, 
 
 note 100 
 
 notice of Mr. Godwin's Essay on, note 100 
 
 Condensation, the absolute resistance of various mortars 
 
 compared in regard to the effect of -JoS 
 
 Consistency of paste of hydraulic lime when immersed, art. 11 6 
 
 of good mortar, note c 35 
 
 importance of a good consistency, whether in mortars 
 
 or cements, art. 182 72 
 
 effects of too thin a consistency on mortar when exposed 
 
 to the air, note 75 
 
 the degree of, requisite in any material that it may be 
 
 beaten with effect, art. 255 Jot; 
 
 comparison of the relative resistances of various hydrau- 
 lic mortars and cements, immerged in various states of 
 
 consistency -_> j ( ; 
 
 mortars compared with regard to the consistency given to 
 
 the mixture of lime and sand 259 
 
 • dlization of metallic mirrors after solidification, note m. 133 
 Crystals, found in ancient Egyptian mortar, note 114, 1 15 
 
 D. 
 
 Dalton, Dr., his opinion that a current of aqueous vapour ac- 
 celerates the reduction of limestone into lime 152, 153 
 
 this confirmed by an experiment of M. Gay-Lussac, not* 1 -5:5 
 
 successful application of this principle by Lord Stanhope 1"*:'. 
 
INDEX. 067 
 
 Damp. — Process of extinction for mortars exposed to a damp 
 
 soil, art. 240 gg 
 
 effect produced by removal on cements from a damp 
 
 situation to a dry one t 212 
 
 Darcet, M., result of his analysis of mortars found on the 
 
 demolition of the Bastile, art. 285 124 
 
 Dead lime, how distinguished from the unburnt limes, noteb. 14 
 
 Desiccation, rapid, bad effects of, upon mortars, art. 234 95 
 
 remedy for, art. 234, p. 295, note g 9G 
 
 what mortars best adapted to resist, note <*. 9G 
 influence of slow desiccation on mortars, lon<r 
 
 known in Italy 207 
 
 how applied in the fabrication of artificial stones 207 
 
 experiments on 208 
 
 mortars compared in regard to the influence of... 252 
 process for accelerating, adopted by the Romans, 
 
 art. 277 120 
 
 Deterioration of lime by the action of the air, art. 60 27 
 
 of mortars by the vicissitudes of the weather, art. 243 
 
 25 1 102—105 
 
 explanation of the deterioration of some water cements 
 
 and mortars 199 
 
 observations upon certain cases of deterioration of cements 
 
 removed from a damp situation to a dry one 212 
 
 of the vertical plasters of pouzzolanas in Italy 213 
 
 hydraulic mortars and cements compared with respect to 
 
 the deterioration which they undergo at their surfaces. 247 
 
 Dolomites, useful as cements, note t \\ 
 
 Doue, methods used at, for slaking hydraulic lime on a lar<^e 
 
 scale ] 70 
 
 Dross, and slag, from large furnaces, afford but " feebly 
 
 energetic " pouzzolana, art. 159 G3 
 
 Drowned mortar, cause of the bad qualities of 205 
 
 Drying, precautions in respect to, art. 2:29, 230 93, 94 
 
 See Desiccation, 
 
 Dutch Tarras, account of the nature and properties of, note 
 
 178—180 
 See Tarras. 
 
 E. 
 
 Earthenware, pounded, used as an ingredient in cements, 
 
 art. 121 oO 
 
26* ixpkx. 
 
 Page 
 
 Economy in ornamental constructions by the use of hvdraulic 
 
 limes, art. 259 109, 110 
 
 Eddystone Lighthouse, coating used to guard the cement of, 
 
 note k 77 
 
 Eggs, whites of, used in India, in the manufacture of stucco, 
 
 note x 170 
 
 Egypt, the most ancient use of lime in buildings there, art. 268, p. 1 1 4 
 the mortar in the pyramid of Cheops similar to the pre- 
 sent, art. 2G8 114 
 
 analysis of it, note 114 — 110 
 
 a composition of rich lime and coarsely pounded gypsum, 
 
 note 115 
 
 mortar employed in, greatly superior in durability to that 
 
 of the Romans, art. 269 11G 
 
 ancient mode of employing cements in, art. 2G9 11G 
 
 method of building with bricks in, art. 270 117 
 
 " Energetic" — Application of the terms " very energetic," 
 
 " energetic," and " feebly energetic," to substances 
 
 used in the formation of mortar, art. 127 — 132 52, 53 
 
 properties of substances so distinguished par. 2, 3 57 
 
 Equivalent, chemical, note c 14 
 
 Experiments, account of the manner in which the experiments 
 
 that form the basis of the tables were made 234 — 23G 
 
 Extinction, order of pre-eminence of the three modes of, for 
 
 hydrates of lime, art. 95 40 
 
 choice of the process of, art. 173 — 177 69 — 71 
 
 of the processes of, for different limes, art. 174 70 
 
 spontaneous, influence of, art. 177 70 
 
 important caution respecting, note e 71 
 
 order of the three processes, for mortars exposed to the 
 
 air and weather, art. 222 91 
 
 process of, for mortars exposed to a damp soil, art. 240... 98 
 
 value of M. Lafaye's process 168 
 
 effects on colour by different modes of 169 
 
 by immersion, not a difficult operation 170 
 
 method employed by MM. Ollivier 170 
 
 difference between the lirst and third modes of 196 
 
 See Expansion, Immersion, Slaking, Vapour. 
 
 F. 
 Faraday, Dr., experiment by, note 153 
 
INDEX. 2C9 
 
 felspar, nature of, note c 4.; 
 
 Fishponds, mortar used by tlie Romans for the lining of, 
 
 art. 277 no 
 
 analysis of mortar from an ancient fish-pond near Gre- 
 noble 22-4 
 
 Fleuret, M., examination of his process of slaking 107 
 
 Forge-scales, powdered, used as an ingredient in mortar, note 50 
 
 Fossil sands, nature of, art. 107 — 100 45, 4« 
 
 See Sand. 
 Foundations, artificial, hydraulic lime used for, in France, art. 
 
 46 20 
 
 the use of " concrete " in, highly advantageous, note 100 
 
 process of the Romans in laying, art. 274 lift 
 
 Frost. — Combination of materials necessary to produce mortars 
 
 or cements capable of resisting severe frosts, art. 1G3... 05 
 all cements of rich limes resist frosts but imperfectly, 
 
 art. 248 103 
 
 how the action of, may be weakened or avoided, art. 248. 103 
 proportion of ingredients in mortars which renders them 
 
 liable to the attacks of frost, par. 1 — 3 104 
 
 age required to enable mortars to resist the effects of, 
 
 art. 250, 251 104 
 
 effects of, upon mortars and cements, and difficulty of 
 
 explaining them 213 — 2 1 5 
 
 usual mode of experiment 210 
 
 method proposed by M. Brard to distinguish substances 
 
 liable to be affected by frost 210 
 
 application of that method to various mortars 216, 217 
 
 M. Brard's process useful in establishing the relative 
 
 qualities of cements or mortars 218 
 
 Fuel, diminished consumption of, by M. Lacordaire's method 
 
 of preparing hydraulic lime 15(J 
 
 proportions of, required for different kilns 157, 158 
 
 Furnace, reverberatory, defects of 186, 187 
 
 description of an air furnace, note 18G 
 
 G. 
 
 Gas. See Vapour. 
 
 Gay-Lussac, M., experiment respecting the effect of aqueous 
 
 vapour in the burning of lime-stone, note 153 
 
 Geode, meaning of the term, note h 2 
 
 Girard, M., remarks upon his " Notice sur des nouveaux 
 
 Mortiers hydrauliques " 228 
 
 *K 
 
•271) IMHA. 
 
 Pkge 
 
 Girard, M., his opinions respecting hydraulic mortars com- 
 posed with arenaceous sands, controverted 228— SSI 
 
 Godwin, Mr., notice of his essay on " Concrete," note 100 
 
 Gravel, how the voids in are filled up, note 87 
 
 to ascertain proportions for mixing, note 88 
 
 Greece. — Cements applied hy the Greeks to various uses un- 
 known to the Egyptians, art. 271 117 
 
 excellence of their terraced roofs and walls, art. 271 117 
 
 perfection of their artificial pavements, which quickly ab- 
 sorbed all the water with which they were washed, art. 
 
 271 11" 
 
 Grey-wacke. See Psammites. 
 
 " Grossiere calcaire,'" nature of; the houses at Paris built with 
 
 this material, note f. 2 
 
 Grouting, Col. Raucourt"s liquid mortar for, note 109 
 
 Mr. Smeaton's, note 101) 
 
 Guyton-Morveau, inference to be drawn from his experiments 
 as to the effect of chemical affinity in the solidification 
 
 of mortars, art. 286 125 
 
 Gypsum, finely pounded, and mixed with a composition of 
 rich lime, the material of the ancient Egyptian mortar, 
 
 note 1 '•» 
 
 a new cement composed of gypsum and a solution of sul- 
 phate of potash 191 
 
 II. 
 
 Hardness of mortars, variation in, art. 81 30 
 
 augmented by the carbonic acid in the atmosphere, art. 86, 
 
 par. 4 38 
 
 how influenced by the method of extinction, art. 95 40 
 
 combination necessary to produce mortars or cements ca- 
 pable of acquiring great hardness in the water, under 
 
 ground, or in damp situations, art. L62 C4 
 
 ditto to acquire hardness in the open air, and to resist rain, 
 
 heat, and severe frosts, art. 1G3 0"> 
 
 various proportions leading to the greatest degree of, 
 
 art. 166, 17G 07. 70 
 
 relative degrees of, in different mortars, art. 213 88 
 
 mortars which do not " set " much improved in, by re- 
 union with carbonic acid, note rt5 
 
 substances capable of acquiring considerable hardness with 
 one fluid, are altogether void of it. with another, note... 127 
 
INDEX. o 7 , 
 
 Hardness of ancient mortars o o !Sff 
 
 remarkable instance of the time which mortar of rich lime 
 
 requires to harden Oo<) 
 
 comparison of the hardness and absolute resistance of 
 compounds resulting from the union of water with 
 
 various limes O «o 
 
 quickness of "set" of various cements, compared with 
 the proportions and the hardness acquired after a year's 
 
 immersion ,,,., 
 
 See SoUdiJieat'ton. 
 
 Harwich cement, analysis of, note ,,o 
 
 " Hawk," or pallet of plasterers, use of, note f. o,.-, 
 
 Heat of the weather.— Combination of materials necessary to 
 
 produce mortars or cements capable of resisting, art. 1 G3. (>:> 
 
 Higgins, Mr., composition of his patent stucco, note e }}<i 
 
 theory of the solidification of mortars, art. 285 124 
 
 result of his experiment on the calcination of lime-stone, 
 
 " otc] 154 
 
 Hydrated sub-carbonate of lime, how formed, note ij(» 
 
 Hydrates of lime.— Chemical definition of a hydrate, and com- 
 ponent parts of a hydrate of lime, note a 34 
 
 account of, art. 79 — 100 34 40 
 
 influence of water on, art. 80 3l 
 
 influence of the degree of consistency given to the hy- 
 drate in the first instance, art. 81 , M 3 t 
 
 action of the air on, art. 82 — 8G 35—38 
 
 mode of exhibiting this action, art. 82 35 
 
 variation in the hardness acquired by, art. 81 30 
 
 action of water on, art. 87 — 100 33 40 
 
 hydrates of rich limes, not of any great benefit, art. 98... 41 
 use that may be made of the hydrates in the arts, art. 99. 42 
 results from a comparison of the mortars with, art. 208... 85 
 how a hydrate of lime may be obtained, in different condi- 
 tions ,«, 
 
 1 / 1 
 
 analysis of small pieces of, exposed to the air for eight 
 
 • vcars 173, 171 
 
 importance of their density 1^ 
 
 comparison of the hardness and absolute resistance of 
 compounds resulting from the union of water with va- 
 rious limes 29 : 
 
 I the absolute resistances of mortars compared with those 
 
 of the hydrates of lime constituting their gangues 219 
 
 See L'nnc. 
 
 'K 2 
 
272 inpi.x. 
 
 Page 
 
 Hydration, method of analysing magnesian limestones l»y L40 
 
 Hydraulic cements. See Cements, Hydraulic Lime, Lime, 
 
 Mortars. 
 Hydraulic lime, artificial, extensively used in France, art. 40, p. 20 
 employed in the fabrication of the " beton," for the found- 
 ation of bridges, art. 40 20 
 
 two methods of preparing, art. 48 — 51 21, 22 
 
 comparison between the artificial hydraulic limes and the 
 
 water cements used in England, note d 21 — 23 
 
 description of the process of manufacturing followed by 
 
 M. St. Leger at Paris, art. 52—54 22—24 
 
 average price of, art. 55 25 
 
 history of 150 
 
 examples of the use of 101 
 
 details of the manufacture on a large scale, with the 
 
 price of the materials and workmanship 104 — 100 
 
 See Cements, Lime, Mortars. 
 Hydraulic mortars. See Cements, Hydrates, Mortars. 
 Hydro-oxygen blow-pipe, note a 13 
 
 I. 
 
 Immersion of hydraulic lime, mode of, in the small way, for 
 
 experiment, art. 12 
 
 slaking by, art. Gl 27 
 
 sudden, prejudicial to rich and hydraulic limes, art. 75... 31 
 different effects of, on hydrates in the condition of soft 
 
 and stiff paste, art. 90 40 
 
 when it may be used with impunity, art. 97 40 
 
 case of constant immersion, compositions for, art. 102 ... 01 
 calcareous mortars, or cements, intended for, art. 105 — 
 
 200 07—03 
 
 of" beton" how carried on, art. 193 7(j 
 
 method of, proposed by General Trcussart, note 1 77 
 
 See Extinction. 
 
 Incrustations, remarks upon some 224 
 
 India, cause of the speedy decay of mortars and cements in, 
 
 note, p. 103 note, 213 
 
 preventive for, note 103 
 
 nature of the plaster used in 170 
 
 analysis of different old mortars found in 250 
 
 See Carbonate of magnesia, Chunam, Madras, Masiilipatam. 
 
index. 073 
 
 t i • Page 
 
 Induration. See Hardness. 
 
 " Inert," explanation of the term, art. 130 53 
 
 properties of substances so called, par. 1 57 
 
 Ingredients. — Account of the various ingredients which unite 
 
 with lime in the preparation of calcareous mortars, or 
 
 cements, art. 101 — 12G 43_51 
 
 mutual suitableness of, art. 161 — 164 64 66 
 
 qualities of, art. 127—143 52 — 57 
 
 Interlacement, hypothesis of, considered, art. 289 126 
 
 Iron, oxide of, deprives lime-water of its causticity, note c... 56 
 
 its effect on the colour of lime 145 
 
 the presence of, not indispensable in " energetic " pouzzo- 
 
 knas 183 
 
 oxide of, its efficacy invalidated by facts 183 
 
 protoxide and peroxide of, note b 55 
 
 scales of, used as an ingredient in mortar, note 50 
 
 Iron-stone, siftings of, used as an ingredient in mortar, 
 
 note 50 
 
 Italy, the caskets and snuff-boxes made there, of the same 
 
 material as the ancient Roman cement, art. 278 120 
 
 See Romans. 
 
 J. 
 
 Jaghery, meaning of the term, note 84 
 
 See Sugar. 
 John, M., result of his analysis of old mortars, art. 285, 286. 
 
 124, 125 
 remark upon an assertion of, as to the hardening of lime, 
 
 art. 312 136, 137 
 
 his discovery of the impotency of the most caustic lime 
 on quartz 130 
 
 K. 
 
 Kilns, various kinds of, art. 32 l.-> 
 
 irregular action of the coal kiln by slow heat, art. 41,42. 
 
 p. 17, 18, 151) 
 
 best forms of, art. 43 \q 
 
 quantity of coal consumed in, art. 44 13 
 
 adapted to the calcination of artificial pouzzolanas, art. 1 52, p. 6 1 
 account of different kilns, with the quantity of fuel con- 
 sumed by each 157, 158 
 
27 I IND 
 
 Kilns. — Remarks on the coal kilns at Paris 158 
 
 with alternating (ires, tor the- burning of argillaceous lime- 
 stone- IV.' 160 
 
 disadvantages of the flame kilns 186 
 
 description of one p rop osed by the author 159 — 161 
 
 L. 
 
 Lacordaire, M., his successful application of certain experi- 
 ments on limestones, in the works connected with the 
 
 Burgundy Canal, art. 206 113. LS6 
 
 Lafaye, M. de, notice of his process of " extinction" 161 
 
 Le Sage, 11 . account of his phitre cement 220, 221 
 
 compared with the cement of Messrs. Parker and Wyatt 221 
 Lime. — Classification of the different varieties of limes, art. 13. 6 
 
 nature and properties of the u rich '" limes, art. 14 8 
 
 of the " poor " limes, art. 15 7 
 
 of the moderately hydraulic limes, art. 16 7 
 
 of the hydraulic limes, art. 17 8 
 
 of the eminently hydraulic limes, art. 18 8 
 
 of the colours of these limes, art. 19 8 
 
 When lime may be said to M set, v art. 20 1» 
 
 relation between the qualities of limes, and the chemical 
 composition of the stones whence they are derived. 
 
 art. 21 — 24 9—12 
 
 Mib-carbonate of, art. 30 14 
 
 dead-lime, as distinguished from the unburnt limes, note b. 1 4 
 rvations on kilns for the burning of. art. 32. 42 — 44.15 — 18 
 account of the manufactory of artificial lime at Meudon, 
 
 art. 52—54 22-21 
 
 ordinary process of slaking, ar t. 5G 2G 
 
 by immersion, art. Gl 27 
 
 spontaneous method, art. GG -'j 
 
 specific gravity of, when pure, note a 28 
 
 effect of cold water upon rich lime, in effervescence, art. 59 27 
 observation on the effect of mechanical subdivision on, 
 
 note c 
 
 exposed to the air, re-absorbs carbonic acid, art. 70 30 
 
 time required for this in rich and hydraulic limes, art. 70 3o 
 changes which take place in lime slaked by immersion, 
 
 art. 71 — 74 31 
 
 a sudden immersion prejudicial to rich and hydraulic- 
 limes, art. 75 31 
 
INDEX. -27.") 
 
 Page- 
 Lime, mode of preserving, art. 7(J — 7t> '3-2, 33 
 
 properties of certain rich limes, art. 80 37 
 
 of hydraulic limes, art. 8G, par. 3 38 
 
 hydrates of, augmented in hardness by the carbonic acid 
 
 of the atmosphere, art. 00, par. 4 38 
 
 experiment to shew the absorbent power of fresh slaked, 
 
 note f. 42 
 
 when hydraulic lime may be immersed, art. 97 40 
 
 small slabs similar to marble may be made with the 
 
 rich and white limes, art. 99 , 42 
 
 experience the best guide in the choice of limes, art. 134. 54 
 reciprocal suitableness of the various kinds of lime, and 
 
 the ingredients which unite with it in the composition 
 
 of mortars and cements, art. 101 — 104 G4 — 00 
 
 on the mixture of the different limes with the other in- 
 gredients of mortars and cements 07 
 
 what materials have the least affinity for lime, art. 107... 08 
 when it is better to err from a deficiency than an excess 
 
 of lime, and vice versa, art. 170 G8 
 
 a considerable excess proper in common mortars, note b. 08 
 importance of proportions in respect to hardness, art. 171. 
 
 08, 09 
 modifications of, according to the purposes for which the 
 
 mortars or cements are to be applied, art. 172 09 
 
 component parts of the best hydraulic lime, note 09 
 
 process to be applied to the hydraulic, and " eminently " 
 
 hydraulic limes, when the ordinary mode of slaking is 
 
 adopted, art. 185 73 
 
 how to treat eminently hydraulic limes after slaking, note... 73 
 
 discovery of the virtues of Narva lime, note 73 
 
 mistake in using hot lime to accelerate the " set," with a 
 
 view to the greatest induration, art. 197 7<> 
 
 criterion of lime being completely slaked, art. 197 79 
 
 the bad qualities of rich limes corrected by the use of 
 
 sugar, or molasses, note 84 
 
 with what limes the mixture of sand is injurious or 
 
 beneficial, art. 208 85 
 
 what sands should be mixed with certain limes, art. 
 
 209—214 85—89 
 
 each kind of lime behaves, with respect to this or that 
 
 sand, in a manner which is peculiar to it, art. 215 88 
 
 case of the rich limes, art. 210 90 
 
 of the simply hydraulic limes, art. 218 90 
 
■210 IM'IA. 
 
 E*ge 
 J, ilia-. - 1 lie l»t st proportions subordinate to the nature of the 
 
 lime, and the mode of extinction, art. '220 91 
 
 choice of the mode of slaking, art. 221 1)1 
 
 detail of the manufacture of mortars with, art. 223-290... 9 1-84 
 different effect on certain limes when exposed to the 
 
 atmosphere, art. 225 92 
 
 when the quartzose, or calcareous sands, are injurious to 
 
 the hydraulic and eminently hydraulic limes, art. 239. 08 
 deterioration of, hy the mixture of improper substances, 
 
 art. 213 102 
 
 when the mixtures of rich limes and " inert" sands become 
 
 decomposed in water, art. 247 103 
 
 hydraulic, may be employed as an ingredient in cast- 
 ing ornaments in those cases in which the number 
 
 of moulds ceases to be a difficulty, art. 250 100 
 
 how the artificial mixtures of pure lime and clay, in 
 certain proportions, become natural or artificial 
 
 cements, art. 260 • 113 
 
 extensive use of half-burnt lime in the works of the 
 
 Burgundy Canal, art. 206 113 
 
 the earliest use of, to be found in one of the Egyptian 
 
 pyramids, art. 208 114 
 
 mixture of sand with, in ancient mortars, art. 203 113 
 
 opinion of the Romans as to the best lime, art. 274 118 
 
 the properties of hydraulic lime totally unknown to them, 
 
 art. 274 118 
 
 in paste, how employed by the Romans, art. 277 120 
 
 in the Roman cements, scarcely harder than chalk, art. 
 
 278 120 
 
 combines chemically in artificial pouzzolanas, as well 
 as in cements formed with the uncalcined psammites 
 
 and arenes, with these substances, art. 314 138 
 
 this confirmed by experiments, and the opinion of General 
 
 Treussart, note 133, 139 
 
 \arieties in the quality of, known to the ancients 144 
 
 Yitrm ius's account of the qualities of, repeated by modern 
 
 authors 145 
 
 notice of experiments on eighty-three sorts of 145 
 
 remarks on the colour of 145 
 
 various opinions as to the virtues of hydraulic lime de- 
 pending on the presence of manganese 150 — 152 
 
 how rich limes may he made to acquire hydraulic pro- 
 perties, note m 155 
 
INDEX. -277 
 
 Lime. — Table ol the weight of" rich lime" converted into paste 
 
 by different processes 108, 169 
 
 weight of a cubic foot of dry slaked " rich" lime, pre- 
 pared from sea shells, and slaked by immersion, note s. 100 
 difficulty of ascertaining the quantity of, put into mortar, 
 
 when lime slaked by the ordinaryprocess is used 109 
 
 how rich lime may be preserved for ages 109 
 
 instance of lime being kept rich and moist for five 
 
 hundred years 169, 170 
 
 cause of the prejudices against hydraulic lime among the 
 
 workmen 170 
 
 use of unmixed lime in buildings 175 
 
 impotency of the most caustic lime on quartz 180 
 
 inaction of hydraulic lime in the same circumstances 180 
 
 absence of chemical action by the hydraulic limes on 
 
 various kinds of sand 181 
 
 its action in the humid way on silica and alumina when 
 
 isolated 184 
 
 effect produced by mixing clay with, when each is in a 
 
 state of pulp, note 185 
 
 when the " poor" limes may be used with advantage 191 
 
 best method of developing the virtues of hydraulic lime, 
 
 note 1 90 
 
 danger of using it imperfectly slaked 198 
 
 comparison of the qualities of various limes, with the 
 
 chemical composition of the lime-stones furnishing them. 237 
 the mutual suitableness of the various limes, with the 
 
 different ingredients of cements and mortars compared. 213 
 See Cements, Hydrates of lime, Hydraulic lime, Lime- 
 stones, Mortars. 
 Lime-stones, properties, and component parts of, art. 1, 2 .... 1 
 
 tests to discover, art. 1 1 
 
 different varieties of, art. 3 2 
 
 experiments to examine the qualities of, art. — 
 
 12. 23 3-0, 11 
 
 each variety of, furnishes a peculiar kind of lime, 
 
 art. 4 3 
 
 actual trial, the builder's only guide as to the 
 
 qualities of, art. 5 3 
 
 result of a chemical examination of the minerals 
 
 supplying the various kinds of lime, art. 21... p. 9 
 calcination of, in the large way, art. 2j — 4o 
 
 13-119 
 
278 INDEX. 
 
 Lime-stones. — Difference between pore and compound lime- 
 stone, art. 28 13 
 
 how the argillaceous lime-stones become natural cements, 
 
 art. 200 119 
 
 this result observed in Russia by Colonel Kaucourt 113 
 
 successfully applied by If. Lacordaire, in the works con- 
 nected with the Burgundy Canal... US 
 
 nature and formation of 140 — 140 
 
 abundant supply of, distributed throughout England, sole, 
 
 142—144 
 
 chemical methods of appreciating the qualities of 143 
 
 M. Bertliier's mode of analysing 1 13 
 
 test to discover if they contain magnesia, note d 144 
 
 process for ascertaining the quantity of lime in a com- 
 pound of lime and magnesia, ?wtc f. 1 10 
 
 value of magnesian lime-stones for mortars and cements 
 
 147—150 
 
 experiments of M. Berthier and the Author on 150 
 
 effect of a current of aqueous vapour in accelerating the 
 
 reduction of, into lime 152, 153 
 
 various experiments as to the effects of calcination on, 154 — 107 
 comparison of the qualities of various limes with the 
 chemical composition of lime-stones furnishing them... '237 
 
 analysis of, furnishing rich lime 237 
 
 poor lime -2M 
 
 feebly hydraulic lime 237 
 
 hydraulic lime 237 
 
 eminently hydraulic lime 237 
 
 Lime-water, action of, on the arenes, psammites, clays, and 
 
 pouzzolanas, art. 141 66 
 
 how deprived of its causticity, note ",t; 
 
 method of preparing a very strong one. note V>o 
 
 " Litre," capacity of this in English measure, note e 144 
 
 Loamy particles in fine sands, injurious effects of, art. 214 : p. 80. 203 
 Loriot, If. his process for hastening the " set " of a mortar ... '21!» 
 
 opinion of Mr. Smeaton on, note 319 
 
 answers well in the composition of stucco, note 290 
 
 Lumps, minute, found after slaking, treatment of 73. mok : 156 
 
 Lyonese method of preparing mortar, art. 220 03. 10« 
 
 Btidgt. 
 
 M. 
 Madras, account of magnesia found in the Presidency of 1 17 
 
INDEX. -27!) 
 
 Page 
 Madras, mode of preparing the "chunam" there, note x 1 7<» 
 
 analysis of a cement used in, note 222 
 
 Magnesia found in old mortars, note GG 
 
 test to discover in lime-stone, note d 14-1 
 
 account of the Madras magnesia 147 
 
 combines with water and forms a hydrate, note 147 
 
 experiment with, as to its acquisition of weight by im- 
 mersion, and its tendency to "set" note 117 
 
 Magnesian lime-stones, properties of, note v 8 
 
 method of analysing by hydration 14G 
 
 extensive beds of, found in India, and their use 147 — 140 
 
 Malcolmson, Dr., analysis of a mortar brought by him from 
 
 the pyramid of Cheops.. 114 — 11 6, note; 11 5, note; 222 — 224 
 
 Manganese, nature of, note c 1 
 
 various opinions as to the virtues of hydraulic lime, de- 
 pending on the presence of 150 — 152 
 
 its oxide an ingredient in the manufacture of artificial 
 
 hydraulic limes 1G3 
 
 Manipulation, the secret of good, art. 231 94 
 
 mortars of rich lime, fifteen months old, compared, in re- 
 gard to the influence of 252 
 
 Manufacture of artificial hydraulic lime, art. 48 — 52. 
 
 p. 21, 22. 1G4— 1GG 
 See Hydraulic lime. 
 
 of artificial pouzzolanas, art. 144 — 1G0 58 — G3. note a. G4 
 
 of mortars or cements intended for immersion, art. 178 — 
 
 100 71—75 
 
 of mortars exposed to the air and weather, art. 223 — 
 
 230 91—04 
 
 of prisms at Alexandria in Piedmont 207, 208 
 
 of stuccoes. See Stuccoes. 
 Marble, small slabs of, may be imitated with the rich and 
 
 white limes, art. 99 42 
 
 opinion of the Romans that it furnished the finest lime, 
 
 art. 274 118 
 
 Martin, Mr., account of his new cement 191 
 
 Masonry, when used instead of the " beton," art. 200 BO 
 
 precaution respecting the soaking of materials used in ... 206 
 how cements should be employed in under-ground, 
 
 masonry, 242 0!) 
 
 Masons, their opinion as to lime which slakes to dryness 107 
 
 Mastics, rich, used to repair damaged pouzzolanas 213 
 
 Masulipatam, notice of a water-lime found there, note 12 
 
280 IMjLX. 
 
 Ma^ulipatam, experiment with hydraulic and rich limes of, 
 
 in the manufacture of cement, note a 64 
 
 Matrix for mortars, in what it consists, art. 165 67 
 
 M its, recommended to retard the drying of mortar, note g. ... 96 
 Mechanical agency of the particles in the solidification of 
 
 mortar, considered, art. 288 12(3 
 
 Medal. — The author presented with a gold medal by the society 
 
 of" Encouragement,*' for his discoveries, art. 260 110 
 
 Meudon, account of the manufactory of artificial lime at, art. 
 
 5-2—54 -22—24 
 
 Mica, nature of, note c 46 
 
 often mistaken for talc, note c 46 
 
 Middle ages, mortars of the, compared with those of the 
 
 ancients, art. 280 122 
 
 Milk, used in India in the manufacture of stucco, note x 176 
 
 Mill-works, a good mortar for repairing 177 
 
 Minerals, calcareous, and the limes they furnish 1 — 12 
 
 tests to discover, art. 1 1 
 
 " Minion," meaning of the term, note 50 
 
 used as an ingredient in mortar, note 50 
 
 Mirrors, metallic, crystallization of, after solidification, note m. 130 
 Molasses, used to correct the bad qualities of rich limes, note... 84 
 Molecular and successive motion applied to solve the phe- 
 nomenon of the solidification of mortars, art. 308 133 
 
 Mortars, test to exhibit the action of the air on, mote d 35 
 
 when hydraulic mortars in the condition of hydrates can 
 
 be employed, art. 100 42 
 
 materials added to lime in the formation of, art. 
 
 101—126 43 — 51 
 
 best proportion of lime or other cementing matter in, 
 
 how ascertained, note 45 
 
 various action of the substances combined with lime, to 
 
 form calcareous cements, art. 125 50, 51 
 
 qualities of the materials combined with lime in the 
 
 fabrication of, art. 127 — 143 52 — 57 
 
 reciprocal suitableness of the various kinds of lime, and 
 the ingredients which unite with it, in the composi- 
 tion of mortars and cements, art. 161 — 164 64 — G6 
 
 comparative table relating to 243 
 
 combination of materials necessary to obtain mortars or 
 cements capable of acquiring groat hardness in the 
 water, or under-ground, or in situations constantly 
 damp, art. 162 «>4 
 
INDEX. 281 
 
 Page 
 
 Mortars. — Ditto in the open air, and to resist rain, heat, and 
 
 severe frosts, art. 163 6"> 
 
 reason for the superior durability of old mortars, note b. (>•"> 
 
 contain silica and magnesia, note 66 
 
 the most durable common mortars manufactured from 
 
 hydraulic limes, note GG 
 
 on the mixtures of the different limes with sand, and the 
 
 other ingredients of mortars and cements <»7 
 
 of calcareous mortars or cements intended for immer- 
 sion, art. 165. — 206 67 — 83 
 
 choice of proportions, art. 166 — 172 67 — 69 
 
 choice of the process of extinction, art. 173 — 177 ... 69 — 71 
 of the manipulation or manufacture, art. 178 — 190 ...71 — 75 
 
 of the using or immersion, art. 191 — 200 75 — 80 
 
 action of water upon the parts of the mortars and cements 
 
 in immediate contact with it, art. 201 — 204 80, 81 
 
 influence of time, art. 205, 206 82, 83 
 
 a considerable excess of lime proper in common mortars, 
 
 note b 68 
 
 the best hydraulic mortar, according to Col. Raucourt, 
 
 note 69 
 
 beatings, useful in hydraulic mortar, composed of lime 
 
 and tarras, note f. 71 
 
 should be of a good clayey consistency, art. 182 72 
 
 test to prove the completeness of the extinction, art. 185, p. 73 
 in what case the lumps after slaking should be bruised 
 
 and reduced to powder, note h 7.J 
 
 directions respecting mortar or cement intended for imme- 
 diate immersion, art. 189 7.", 
 
 when rammers are to be used instead of beaters, art. 190, p. 75 
 importance of the manner in which the beton is immersed, 
 
 art. 191 7<; 
 
 box proposed by Belidor, the best, art. 192 70 
 
 how the immersion of the " beton " is carried on, art. 193.. 76 
 
 directions when there is a flowing stream, art. 194 77 
 
 General Treussart's method of immersion, note 1 77 
 
 objections to the use of hot lime, and the immersion of 
 
 the "beton" while warm, art. 197, 198 78, 79 
 
 directions when the immersion of a certain quantity of 
 
 "beton" has been postponed, art. 199 79 
 
 when mortars or cements are used in a "dry way," art. 
 200 HO 
 
282 INDEX. 
 
 p • 
 Mortars. — Difference in the strength of hydraulic mortar when 
 
 made with sea-water, note B1 
 
 the goodness of not always indicated by the rapidity 
 
 of its "set," art. 205 8_> 
 
 an excess of ricli or slightly hydraulic lime in a cement 
 
 retards its "set," par. 1 83 
 
 what modes of extinction are best calculated to hasten 
 
 the " set," par. 2 83 
 
 progress of the induration of certain cements, par. 3. 83 
 
 the relations, in respect to hardness, deduced from a com- 
 parison of the three modes of slaking, how modified by 
 
 time, par. 5 83 
 
 the use of mortars of rich lime should be prohibited in 
 
 works of any importance, art. 207 84 
 
 an excellent mortar made in the East Indies, note 81 
 
 when sugar or molasses may be employed, note )'. t 
 
 results of a comparison of the mortars with the hydrates, 
 
 art. 208 85 
 
 on the mixture of the different kinds of sand, art. 209 — 
 
 214 8.3—80 
 
 when fine sand produces excellent mortars, art. 214 8!) 
 
 on the resistance of mortars made from different limes, 
 
 art. 21G— 220 00, 01 
 
 on the time required for "souring," art. 223 — 226 02, 03 
 
 effects of along continued trituration, art. 224. 220; p. 02, 03 
 of the atmospheric influence on the ingredients of mor- 
 tars, art. 225—227 02, 03 
 
 Lyonese method of preparing, art. 22G 93 
 
 how far the treatment of mortars for immersion applies 
 
 to those exposed to the air, art. 228 03 
 
 should always be prepared under cover, art. 229 0:5 
 
 mode of treating a very stiff mortar, art. 231 1 
 
 precept in which the secret of good manipulation is con- 
 densed, art. 231 !»1 
 
 the bricklayers' practice in respect to, art. 231 04 
 
 application of mortar in building, art. 232 01 
 
 effect on mortars exposed to a rapid desiccation, art. 234, p. 95 
 how to prevent this when building takes place in hot wea- 
 ther, art. 234 !>."» 
 
 chalk mortar injured by being kept too long in a very 
 
 damp state, note g 95 
 
 method <>f retarding the desiccation of mortar, note <j — 00 
 
INDIA. OS3 
 
 Mortars. — What mortars are best adapted to resist the effect of 
 
 drying too soon, note £ < (( ; 
 
 mortar a hundred years old still in its infancy, art. 23,3... 06 
 
 good mortars of rich lime seldom found, except in very 
 old buildings, art. 235 9 ( ; 
 
 effect of the atmosphere upon certain mortars exposed 
 to the air in small bulk, art. 236 90 
 
 atmospheric vicissitudes in climates not subject to frost 
 increase the hardness of mortars, note h 9(j 
 
 of calcareous mortars and cements subject to the influ- 
 ence of a damp soil, art. 238—242 98 101 
 
 manufactured in the same way as mortars exposed to the 
 weather, with certain exceptions, art. 238 98 
 
 resistance of different kinds of mortar when various pro- 
 cesses are employed, art. 241 99 
 
 of the vicissitudes to which cements and mortars may be 
 exposed, and the consequences, art. 243 — 252 ... 102 105 
 
 some mortars which solidify in the water crumble in a dry 
 and warm air, art. 243 jqo 
 
 formed from the hydraulic or eminently hydraulic limes 
 solidified in a damp soil, behave equally well in the 
 open air and in water, art. 244 102 
 
 when these have hardened in the open air the induration 
 will continue in water or a damp soil, art. 24G 102, 103 
 
 formed by the simple mixtures of rich lime with " inert " 
 sands, become decomposed in water, art. 247 103 
 
 cause of the speedy decay of mortars in India, note 103 
 
 indications of the resistance of mortars to the effects of 
 winter in France, art. 249, 250 103, 104 
 
 age required for certain mortars to enable them to with- 
 stand the frost, art. 250, 251 10 j 
 
 maximum limit of sand proper for mortars of rich limes 
 used under the covered parts of buildings, art. 252 ... 105 
 
 influence of "beating" on the resistance of mortars in 
 general, art. 253 — 200 \qq jj ( ) 
 
 may be moulded into any form or shape, art. 253 106 
 
 how it will take the appearance of stone, art. 253 106 
 
 when contained in a mould, may be beaten or rammed in 
 the manner of "pise," art. 254 106 
 
 different effects of the process of beating, art. 25G...107, 108 
 
 casts made of, retain their hardness in the roughest wea- 
 ther, and are often taken for stone, art. 257 10): 
 
 difficulty of discovering a means of hastening the "set" 
 
•jv j INDEX. 
 
 of a mortar, without injuring it-> future qualities, art. 
 
 258 
 
 Mortars. — Loriot's process insufficient, art. 258 1<>!> 
 
 Col. Raucourt's liquid mortar for grouting, note ]<»:» 
 
 Mr. Smeaton's grouting, note 1 B 
 
 hydraulic lime may be employed in preparing artificial 
 
 stones bearing mouldings, vases, &c, art. 259 100 
 
 antique, compared with those of medium age and modern 
 
 mortars, art. 268—283 U4— 123 
 
 used in the pyramid of Cheops in Egypt, similar to the 
 
 present, art. 2C8 114 
 
 analysis of the mortar, note 114 
 
 the use of cements known two thousand years ago, art. 
 
 •268 11*> 
 
 superior durability of the Egyptian cements to the 
 
 Roman, art. 269 115. 1 1<; 
 
 application of cements in Greece, art. 271 117 
 
 by the Romans, art. 272.273. 117—119 
 
 nature of their mortars and cements, and to w hat purposes 
 
 applied, with an analysis of them, art. 272 — 283, p. 117 — 123 
 
 prepared with oil by the ancients, note 121 
 
 on the theory of 124 — 139 
 
 improved in hardness by reunion with carbonic acid, 
 
 note 123 
 
 extent of our knowledge of, art. 287 126 
 
 table showing the relative proportions of lime, sand, and 
 
 carbonic acid in different mortars, note 133 
 
 various purposes to which mortars made with hydraulic 
 
 limes have been applied 161 — 1 1 (3 
 
 rapidity of absorption of carbonic acid by 172, 173 
 
 composed of rich lime and a reddish, argillaceous pit- 
 sand, much used in repairing mill-works 177 
 
 notice of the contradictions exhibited in different memoirs 
 
 relating to mortars and pouzzolanas 191 — 193 
 
 table of twenty compositions of water-mortar suited t,p 
 
 different situations and circumstances 193 
 
 different views of the constitution of cement and mortars. 196 
 methods of fabrication and immersion adopted in the foun- 
 dations of the bridge of Charles X. at Lyons 197 
 
 explanation of the deterioration of some water-cements 
 
 and mortars 1 99 
 
 experiments of If. Petot on 200 
 
 cases of exception with regard to the influence of time on. 201 
 
ini>j:x. 285 
 . 
 .Mortars. — Experiments with mortars made of lime and cal- 
 careous sand 201 20° 
 
 unanimous opinion respecting mortars and cements mixed 
 
 "thin" 204 
 
 causes of the bad qualities of a mortar which has been 
 
 drowned 20 I 
 
 observations on the mixing of, note 204 205 
 
 influence of slow desiccation of, long known in Italy 207 
 
 experiments on the desiccation of 208 
 
 mortar eighty years old, found quite fresh 209 
 
 mortars of rich lime in a damp soil, harden after six or 
 
 seven hundred years 200 
 
 table of the constituent parts of ancient mortars 210 
 
 effects of frost on mortars and stuccoes 213 218 
 
 durability of mortars taken from ancient bridges..... 225 
 
 opinions of ftff. Girard on hydraulic mortars composed 
 
 with arenaceous sands controverted 228—231 
 
 comparison intended to show the mutual suitableness of 
 the various limes, with the different ingredients of ce- 
 ments and mortars 243 
 
 hydraulic mortars and cements compared with regard to 
 
 the process of slaking made use of 244, 245 
 
 comparison of the relative resistances of hydraulic mor- 
 tars and cements, immerged in various states of con- 
 sistency 2 1 (> 
 
 hydraulic mortars and cements compared with reference 
 to the deterioration which they undergo at their sur- 
 faces 217 
 
 cpiickness of " set " of various hydraulic mortars and 
 cements, compared with the resistance acquired after a 
 
 year's immersion 247 
 
 ditto of various cements, compared with the proportions 
 
 and hardness acquired after a year's immersion 248 
 
 the absolute resistance of mortars compared with those 
 
 of the hydrates of lime constituting their gangues 21!) 
 
 mortars compared with reference to the size of the- sand 
 
 made use of. 210 
 
 taken from various buildings compared with mortars 
 
 manufactured for experiment, with the same limes 2,0 
 
 compared in regard to their proportions, and the process 
 
 of slaking made use of 251 
 
 of rich lime, fifteen months old, compared in regard to 
 
 the influence of manipulation 253 
 
 •l 
 
IN M V 
 
 Mortars, compared with reference to the consistency siren 
 
 to the mixture of lime anil sand 256 
 
 in regard to the influence of desiccation 252 
 
 the absolute resistance of various mortars compared in 
 
 regard to the effect of condensation 253 
 
 various mortars and cements compared in regard to their 
 
 specific gravity and porosity 253 
 
 characters, composition and absolute resistances of some 
 
 Roman mortars from the South of France 254 
 
 comparison of the resistance of various compounds in re- 
 gard to proportions and the size of the bodies im- 
 bedded in the substance constituting the matrix 255 
 
 analyses of various old mortars 250 
 
 See Cements, Hydraulic lime, Lime, Pouzzolanas, Stucco, 
 Watt r cements. 
 Moulding, mortars may be made to take every possible form 
 
 in, art. 253 100 
 
 contained in a mould may be beaten or rammed in 
 
 the manner of "pise," art. 254 106 
 
 mortar of hydraulic lime may be employed in, art. 259, p. 1"!» 
 
 Mulgrave's cement, result of experiments on, nute f. 123 
 
 Muriatic acid, its action upon sands, art. 135 54 
 
 on the clay of arenes, art. 130 55 
 
 on the schistose psammites, art. 137 55 
 
 on clays, art. 138 55 
 
 comparison of its action upon clays taken in different 
 
 cond i tions 239 
 
 ditto of the qualities of hydraulic cements with the be- 
 haviour of their ingredients in regard to 210. 211 
 
 V 
 
 Narva lime, how the virtues of were discovered, note 73 
 
 Natural cements, art. 201—207 111—113 
 
 See ( Mortars, Pouzzolanas. 
 
 Needle, used for trying the hardness of mortars and cements.. 184 
 Nitric acid, action of. on sands, art. 135 "> 1 
 
 o. 
 
 Obernai lime, remarks on the burning d 17 
 
 Oil, mixed with ancient mortars, nok 121 
 
 u id in India, in ..he making of plaster 170 
 
INDEX. 287 
 
 Pacrp 
 Oil, and wax, form a good composition for protecting valuable 
 
 work 212 
 
 Old mortars. See Antique mortars. 
 
 Ollivier, MM. account of their method of extinction 170 
 
 Ombos, nature of the ancient mortar found there, art. 268 ... 115 
 
 Ornamental constructions, economy in, art. 259 109, 110 
 
 Oxide of iron, opinions as to the efficacy of, invalidated by 
 
 facts |83 
 
 Oxide of manganese, opinion of certain chemists on the 
 
 efficacy of, in lime and mortar K;:j 
 
 P. 
 
 Paint. — A plaster or red paint laid over their mortars by the 
 
 Romans, art. 277 120 
 
 Paris, material with which the houses there are built, note f... 2 
 
 Parker's cement, analysis of, note 22 
 
 result of experiments on, note f. 128 
 
 notice of Messrs. Parker and Wyatt's patent for a " water 
 
 cement, " afterwards called " Roman cement " 220 
 
 a similar cement made by M. Lesage 220 
 
 Pasley, Col., his water-cement, note t 11 
 
 notice of his experiments with carbonate of magnesia ... 147 
 
 with coal-dust as an ingredient in cements, note k 154 
 
 Paste. — Effects of water on soft and stiff pastes, art. 96 40 
 
 how it should be made to avoid shrinkage, note g 41 
 
 quality of, to which the lime should be brought, art. 
 
 179—183 71,72 
 
 when employed by the Romans, art. 277 120 
 
 experiments to ascertain the cause of the cohesion of, 
 
 note 127 
 
 effects of alcohol on a paste of slaked rich lime, note. ... 127 
 Pavements, Grecian, quickly absorbed the water with which 
 
 they were washed, art. 271 117 
 
 Peat, advantage of using, in the burning of lime 159 
 
 Peroxide of iron, nature of, note b 55 
 
 Pestle, when it may be used with advantage, art. 187 74 
 
 Petot, M., notice of his experiments on the relations which 
 exist between the solubilities of lime joined with land 
 
 and the proportions of the mixtures, art 309 134 
 
 experiments on the deterioration of some w.ver-c ements 
 and mortars - 1 99, 200 
 
1NKKV 
 
 Phenomenon observed in mortars and cements in immediate 
 
 contact with water, art. 201—204 80, 81 
 
 Phila, nature of the ancient mortar found in the island of, art. 
 
 288 1*8 
 
 Phosphate of lime deprives lime-water of its causticity, note. 98 
 Piers, pouzzolana employed by the Romans in the construc- 
 tion of, art. 274 lift 
 
 nature of the n beton " used for the piers of bridges and 
 
 the weight borne by it 1C> 1 , 183 
 
 "Pise," nature of this mode of building, note 108 
 
 Plaster used in India, how made 1 7G 
 
 Plaster of Paris, used to guard the cement of the Eddystone 
 
 light-house, note k 77 
 
 experiments upon the solidification of. 226 
 
 Plinv, his account of ancient mortars, art. 280 122 
 
 Pointing, mortar composed of sand and hydraulic lime, used 
 
 for 1G2 
 
 Polish. — Manner of polishing stucco in India, note x 17(J 
 
 Porosity. — Various mortars and cements compared with re- 
 gard to their specific gravity and porosity 253 
 
 Portland stone, the superficial weight it will bear, note f. 123 
 
 Potash, on the mixture of, with clays previous to their cal- 
 cination, in the fabrication of artificial pouzzolanas. 
 
 189, 190 
 
 Pot-shards, used as an ingredient in mortar, art. 124 J»> 
 
 Pouzzolanas. — History and properties of the natural pouzzo- 
 lanas, or volcanic and pseudo-volcanic products, art. 
 
 118—123 4ft, 49 
 
 preparation of, for use, note 4!» 
 
 constituent parts of, note 49 
 
 substances comprised under the name of artificial pouz- 
 zolanas, art. 124 49 
 
 action of acids upon, art. 139 65 
 
 the artificial pouzzolanas exhibit the same phenomena as 
 
 the natural ones, art. 140 66 
 
 deprive lime-water of its causticity, art. 141 68 
 
 manufacture of, art. 144 — 1G0. oft — G3 
 
 first method, art. 148 59 
 
 second method, art. 149 GO 
 
 not materially injured by moisture, note o9 
 
 experiment with hydraulic and rich limes of Masulipatam, 
 
 note a G4 
 
 proportions of lime required by, art. 168 Gft 
 
INDEX. 
 
 Page 
 Pouzzolanas, quick setting of mortars formed of, advan- 
 tageous, note 82 
 
 the Romans unable to do without it in the construction 
 
 of piers or jetties, art. 274 118 
 
 strength of cements formed from, note f 123 
 
 experiments on artificial pouzzolanas, with a view to as- 
 certain the chemical properties of the lime in, note. 138, 139 
 the psammites in their natural state act as pouzzolanas 
 
 with rich lime 173 
 
 Vitruvius's account of the properties of 178, 179 
 
 unequal manner in which some of the pouzzolanas of 
 
 Italy behave with sulphuric acid 179 
 
 tile-dust, the most ancient of the known artificial pouz- 
 zolanas 132 
 
 the presence of iron not indispensable in "energetic" 
 
 pouzzolanas 183 
 
 influence of the contact of the air in the manufacture of, 183 
 
 absorption of oxygen by, not sufficiently established 183 
 
 investigation of the action of the separate constituents of, 
 
 when mixed with rich lime 184, 185 
 
 reverberatory furnace proposed for the calcination of .... 186 
 experiments of M. Bruyere upon artificial pouzzolanas, 187 
 
 repeated on a large scale by fif. St. Leger 187 
 
 experiments with clays in the production of. 187 — 189 
 
 table of experiments on two pouzzolanas mixed with rich 
 
 lime , 190 
 
 explanation of the contradictions exhibited by various 
 
 writers on 191 
 
 comparison of various artificial pouzzolanas with the 
 Italian pouzzolana, Audenack tarras, and aquafortis 
 
 cement 242 
 
 Prinsep, Mr., notice of his catalogue of Indian calcareous 
 
 minerals, note 12 
 
 Prisms, advantage of moulding the hydrates in this form, 
 
 art. 98 11 
 
 manufacture of, in Italy 207, 208 
 
 Proportions used in the manufacture of hydraulic lime, art. 
 
 51 M 
 
 how to ascertain the best proportion of lime or other ce- 
 menting matter in mortar, note '•"> 
 
 choice of, in making mortars or cements intended for im- 
 mersion, art. 1GG — 172 U7— 89 
 
•290 INDEX. 
 
 Paye 
 
 Proportional exceptions offered by the poor limes in rela- 
 tion to 194 
 
 quickness of "set" of various cements compared with 
 the proportions and the hardness acquired after a year's 
 
 immersion 248 
 
 mortars compared in regard to their proportions and the 
 
 process of slaking made use of 231 
 
 Protoxide of iron, note b 55 
 
 Psammites, nature of, art. Ill, 112 40, 47 
 
 how acted upon by muriatic acid, art. 13 55 
 
 deprive lime-water of its causticity, art. 141 50 
 
 when the hydraulic properties of, first discovered 177 
 
 in their natural state, act as pouzzolanas with rich lime... 178 
 
 Pseudo-morphous, meaning of the term, note g 2 
 
 Pseudo-volcanic products. See Pouzzolanas. 
 
 Puddling, hydraulic mortars may be employed in, art. 100 42 
 
 Pumps, use of, during the process of immersion, art. 195 77 
 
 Pyramids of Egypt, the mortar employed in, similar to the 
 
 present, art. 208, and note 114, 115 
 
 See Egypt. 
 
 Q 
 
 Quartz, influence of, upon the cohesion of lime, art. 309, and 
 
 note 13-J 
 
 impotency of the most caustic lime on 180 
 
 Quick-lime, phenomena produced by throwing it into water, 
 
 art. 56 - G 
 
 when only plunged into water for a few seconds, art. 01... 27 
 effect produced on, by the action of the atmosphere, art. 00, p. 29 
 
 experiment for the preservation of, on a large scale 171 
 
 R. 
 
 Rain. — Combination of materials necessary to produce mortars 
 
 or cements capable of resisting rain, art. 103 05 
 
 Kajalnnundry clay, account »1" various experiments with, 220 — 228 
 
 Hammers of cast-iron, use of, art. 187. 190 74, 75 
 
 when ramming may be employed, art. 254 100 
 
 Raucourt, Colonel, precaution as to the drying of prisms, 
 
 note I". *■ 
 
 test to discover the consistency of a good mortar, note c. 35 
 "ii the best hydraulic lime and mortar, note 88 
 
INDEX. 291 
 
 Page 
 
 Raucourt, Colonel, how he discovered the virtues of the Nana 
 
 lime, note 73 
 
 on the effect of exposing mortars to the air, and the 
 addition of water, note 75 
 
 his process for estimating the voids in a mass of stones, 
 gravel, or sand, note 8"3 
 
 plan for determining the proportions in which gravel, 
 stones, and sands ought to he mixed, note 88 
 
 remedy for retarding the desiccation of mortar, note g. ... 96 
 
 his opinion of the effect of the atmosphere on mortars, 
 note h '** ' 
 
 his liquid mortar for grouting, note 10!) 
 
 results observed by, in burning artificial hydraulic lime- 
 stones in Russia, art. 260 113 
 
 ex periment on rich limes, note m 155 
 
 on calcined clays in Russia 183 
 
 description of an air-furnace, note 186 
 
 his composition for protecting valuable work 212 
 
 Resistance, in different mortars, art. 210—219, p. 90, and art. 
 
 24.1 W 
 
 influence of beating on the resistance of mortars in general, 
 art. 253— 200 100—110 
 
 variation of the limits of absolute resistance of mortars of 
 lime and sand, art. 281 122 
 
 absolute amount to be reckoned on in certain mortars, art. 
 2152, 283 123 
 
 of mortars composed of lime and calcareous sand 202 
 
 comparison of the hardness and absolute resistance of 
 compounds, resulting from the union of water with 
 various limes 238 
 
 of the relative resistances of various hydraulic mortars and 
 cements, immerged in various states of consistency ••• 246 
 
 compared with the quickness of " set " of various hy- 
 draulic mortars and cements 247 
 
 the absolute resistances of mortars, compared with those 
 of the hydrates of lime, constituting their gangues ... 241) 
 
 of various mortars, compared in regard to the effect of 
 condensation 203 
 
 of Roman mortars 25 I 
 
 of various compounds, in regard to proportions and the 
 size of the bodies imbedded in the substance consti- 
 tuting the matrix 
 
292 IM»K\. 
 
 Reverberatory furnace, defects of 186. I I 
 
 Roman cement, directions l'or producing a cement similar to, 
 
 noted 22 
 
 proof of the excellence of, note Ill 
 
 a natural cement, art. 263 1 IS 
 
 great consumption of, in London, art. 203 112 
 
 how its use will be restricted, art. 2G3 112 
 
 no artificial composition made in France equal to it in 
 
 point of hardness, art. 264 112 
 
 mortars, — composition, and absolute resistances of. '1~> I 
 
 Romans, inferiority of the cements in their works on the Nile 
 
 to those of the Egyptians, art. 260 116 
 
 a fte r wa rds instructed by their writers on architecture, 
 
 art. 272 118 
 
 their opinion as to the production of lime of the finest 
 
 quality, art. 274 118 
 
 the properties of hydraulic lime unknown to them, art. 274, 
 
 p. 118 
 unable to execute works under water without pouzzolana. 118 
 
 all their mortars exposed to the air, alike, art. 27o 119 
 
 how their hydraulic mortars differ from ours, art. 276 ... 1 19 
 these usually intended to prevent the infiltration of water, 
 
 and for what purposes used, art. 277 Ill) 
 
 their use of a plaster, or red paint, and of lime in paste, 
 
 for lining, art. 277 120 
 
 excellencies of their hydraulic cement, art. 278 120 
 
 the caskets and snuff-boxes of the modern Italians made 
 
 of the same material, art. 278 12o 
 
 the supposition that they possessed a secret for the fabri- 
 cation of mortar controverted, art. 279, 280 121, 122 
 
 oil mixed up with their mortar, note \*1\ 
 
 comparison of their mortars with those of the middle 
 
 ages, art. 280 122 
 
 notice of their " Albaria Opera" .. 17.} 
 
 pounded brick employed by, instead of pouzzolana 179 
 
 nature of the sand used by •J(»2 
 
 table of the constituent parts of certain Roman mortars 210 
 
 Kubble, coarse, how used with sand, note 87 
 
 proportions required to fill up the voids in, note 87 
 
 and for mixing, note 88 
 
 Russian cements, the best, note 7:'' 
 
 natural cements recently found in Russia, art. 264 112 
 
INDEX. 293 
 
 S. 
 
 Page 
 Sand, different kinds of, and how produced, art. 102 — 110. 43 — 40 
 
 specific gravity of siliceous or quartzose sand, notch 44 
 
 method of ascertaining its density, note b 4 1 
 
 the sands characterized as " inert" substances, art. 13*2... 53 
 
 when acted upon by the acids, art. 135 54 
 
 mixtures of the different limes with, art. 167 68 
 
 proportions of lime required by the quartzose or calcareous 
 
 sands, art. 169 63 
 
 what hydrates mixed with pure sand obtain the greatest 
 
 hardness, art. 208 85 
 
 to what limes it is injurious or serviceable, art. 208 85 
 
 how sands were chosen by the ancient builders, art. 209... 86 
 
 no " inert" sand can form a good mortar, art. 209 86 
 
 influence of the size of, art. 210—214 86—89 
 
 of sands suited to particular limes, art. 211 — 214 87,88 
 
 the object of mixing sands, note 87 
 
 process of Col. Raucourt, note 87 
 
 how the voids in are filled up, note 87 
 
 process for determining the proportions in which sand 
 
 should be mixed, note 88 
 
 in fine powder, in certain cases produces good mortar, 
 
 art. 214 89 
 
 the quartzose powders may be also advantageously em- 
 ployed, art. 214 80 
 
 the intervention of loamy or argillaceous particles in fine 
 
 sands robs them of their qualities, art. 214 89 
 
 proportions of, to be added to rich limes, art. 216, 217... 90 
 
 to simply hydraulic limes, art. 218, 219 90 
 
 when injurious to the hydraulic and eminently hydraulic 
 
 limes, art. 239 98 
 
 proportions of, as mixed with different limes, art. 241 ... 99 
 requisite in mortars, to enable them to resist the effects 
 
 of winter, par. 1 — 3 104 
 
 maximum limit of, necessary for mortars used in covered 
 
 parts of buildings, art. 252 105 
 
 a reddish fine sand found in some ancient mortars, art. 268, p. 1 15 
 none discovered in mortar brought from the pyramid 
 
 of Cheops, note 116 
 
 always found in the Roman mortars, art. 279 121 
 
 absence of chemical action by the hydraulic limes on va- 
 rious kinds of sand 1^1 
 
294 INDEX. 
 
 IV 
 
 Sand. — Experiment upon the influence oi calcareous sand in 
 
 comparison with the granitic 201 
 
 ancient examples in favour of the principles laid down re- 
 garding the influence of the coarseness of the grain in 
 
 sands 202 
 
 what sand used by the Romans 202 
 
 fatal instance of the employment of sand impregnated 
 
 with argillaceous particles '201$ 
 
 mortars compared with reference to the size of the sand 
 
 made use of 249 
 
 Saw. — Use of the Spring-saw, art. 127 — 129 52 
 
 Scales. See Forge scales. 
 
 Schist, explanation of the ter m, note c - !< I 
 
 Sea-water, superior strength of hydraulic mortar made with, 
 
 note 1 
 
 " Set " of hydraulic limes, how measured, art. 20 9 
 
 quickness of, how influenced, art. 95, p. 40, and art. 15)7, p. 7» 
 rapidity of, not always an indication of the goodness of a 
 
 cement, art. 205 82 
 
 defects of mortars of hydraulic limes which set quickly, 
 
 note 82 
 
 a quick " set " advantageous in mortars formed of pouz- 
 
 zolanas, note 82 
 
 an excess of rich or slightly hydraulic lime in a cement 
 
 retards its " set," par. 1 H3 
 
 what modes of " extinction " are calculated to hasten it, 
 
 par. 2 83 
 
 difficulty of hastening, without injuring the future quali- 
 ties of the mortar, art. 258 100 
 
 difference of time in the " set " of natural cements, 
 
 art. 202 HI 
 
 M. Loriot's process for hastening 219 
 
 quickness of " set " of various hydraulic mortars and 
 cements compared with the resistance after a year's im- 
 mersion 217 
 
 of various cements, compared with the proportions, and 
 
 the hardness acquired after a year's immersion 248 
 
 Shells.— Excellent quality of mortar made of calcined shells 
 
 and sugar, note 84 
 
 Sheppy cement, an analysis of, note 22 
 
 Shrinkage in the hydrates of rich limes, art. 98, 99 11 
 
 how this may be diminished, note ll 
 
 Silica found in old mortars, note <;,; 
 
indkx. -295 
 
 Silica, action of lime on, in the humid way 184 
 
 forms a good hydraulic cement with rich lime 184 
 
 Silicate of lime, nature of, note 206 
 
 Skeleton vault of bricks, when used 161 
 
 Slag, smithy, used as an ingredient in mortar, art. 124 50 
 
 foundry, — mixed with the cement employed in the new 
 
 docks at Sunderland, note 50 
 
 mode of application in this case, note 50 
 
 and dross from large furnaces, give but " feebly ener- 
 getic" pouzzolana, art- 159 03 
 
 Slaking of lime, phenomena exhibited by, art. 4 
 
 expansion occasioned by, note q 7 
 
 ordinary process, art. 50 ... 20 
 
 how abused, art. 57 20 
 
 expansion of the different kinds of lime by, art. 58 20 
 
 effect of cold water upon rich lime in effervescence, art. 
 
 59 27 
 
 effect of" chill " in, art. 59 27 
 
 what renders lime sluggish in, art. 00 27 
 
 second process of extinction, art. 01 — 03 27 29 
 
 how it ought to be practised in order to reduce rich lime 
 
 well, art. 03 28 
 
 water absorbed by, art. 03 28 
 
 expansion of the various limes by, remarks on, note c. ... 29 
 order of the three processes in reference to the most per- 
 fect division of the limes, art. 08 29 
 
 action of the carbonic acid of the atmosphere upon limes 
 
 differently slaked, art. 70 — 75 30, 31 
 
 method of preserving the different limes before and after 
 
 extinction, art. 76 — 78 32 33 
 
 shrinkage dependent upon, art. 98, and note g 41 
 
 process of, how regulated, art. 173 09 
 
 processes most suitable to certain limes, art. 177, p. 70 ; 
 
 art. 221, 222 \ yl 
 
 a certain sign of complete slaking, art. 197 7l> 
 
 history of the various modes of, with an examination of 
 
 Fleuret's process 107 
 
 methods used at Doue to slake hydraulic lime on a lar«re 
 
 scale 170 
 
 explanation of the influence of the different modes of,194 — 106 
 
 a mode of, approved by trial on a large scale 197 
 
 hydraulic lime should be slaked quickly, note 197 
 
 instance of the danger of imperfect slaking 19li 
 
296 is n ex. 
 
 Page 
 Slaking of lime, explanation of the varied effects of the dif- 
 ferent methods of 203 
 
 hydraulic mortars and cements compared with regard to 
 
 the process of slaking made use of 244, 245 
 
 mortars compared in regard to their proportions and the 
 
 process of slaking used 251 
 
 See Extinction, Immersion. 
 Slow-heat, irregular action of the coal-kiln by, art. 41, 42; 
 
 p. 17, 18 
 Smcaton, Mr., materials used by, as ingredients in mortar, note 50 
 
 remark on the Aberthaw blue lias, note 70 
 
 directions as to beating, note f. 71 
 
 coating used by, to guard the cement of the Eddystone 
 
 light-house, note k 77 
 
 experiments on hydraulic mortars made with fresh and 
 
 sea-water, note $\ 
 
 composition of his " grouting," note 109 
 
 his observations as to the colour of limes, note e 140 
 
 his account of Dutch tan-as, note 173 — 130 
 
 table of twenty compositions of water-mortars 193 
 
 his opinion of M. Loriot's process for hastening the "set" 
 
 of mortars, note 219 
 
 Snuff-boxes. See Caskets. 
 
 Soaking. — Precautions respecting the soaking of materials 
 
 used in masonry 207 
 
 Solidification, of mortars at all times the subject of controversy, 
 
 art. 284 12 1 
 
 discussion of the various hypotheses, art. 284 — 313, p. 124 — 139 
 not a necessary consequence of the chemical combination 
 of two soft or pasty substances, brought into contact 
 
 in the humid way 185 
 
 experiments upon the solidification of the calcined sul- 
 phate of lime 220 
 
 upon the solidification of cements composed of rich lime 
 
 and artificial pouzzolana 22G— 228 
 
 See Hardness. 
 Solids resulting from the simple combination of water and 
 
 lime, art. 79—100 34 — 12 
 
 See Hydrates of lime. 
 
 Solubility of rich lime in water, art. 14 
 
 increased by sugar, note n G 
 
 Souring. — Time required for lime to sour, art. 180 71 
 
 whether benefited by a long souring, art. 223 02 
 
INDEX. -297 
 
 Page 
 
 Specific gravity. — Various mortars compared in regard to their 
 
 specific gravity and porosity 253 
 
 Spontaneous extinction. See Extinction. 
 
 St. Leger, M., description of his process for making artificial 
 
 hydraulic limes, art. 52 — 54 21 24 
 
 experiments on artificial pouzzolanas on a large scale .... 187 
 
 his machine for the fabrication of hydraulic mortars 205 
 
 Stalactites, how formed, note e 3ii 
 
 may be observed under the arches of some bridges, note e. 33 
 Stanhope, Lord, his successful application of a current of 
 
 aqueous vapour in the calcination of lime-stone 153 
 
 Statuary marble, how termed by the French, note e 2 
 
 Stere, its equivalent English measure, note f. 17 
 
 Stink-stone. See Swine-stone. 
 
 Stone, method of giving mortar the appearance of, art, 253, p. 10G 
 casts in bas-relief and in alto-relievo bear a strong re- 
 semblance to common stone, art. 257 108 
 
 mortar of hydraulic lime may be employed in preparing 
 artificial stones bearing mouldings, vases, or ornaments, 
 
 art. 259 109 
 
 resistance of building-stone, art. 281 122 
 
 the assertion that factitious stones of lime and sand can 
 be made as hard as flint, to be received with caution, 
 
 art. 281 122 
 
 the superficial weight borne by Portland stone, note f. ... 123 
 mode of manufacturing artificial stones at Alexandria in 
 
 Piedmont 207 208 
 
 value of M. Brard's process for discovering whether they 
 
 are likely to be affected by frost 218 
 
 Stream. — Advantages of a flowing stream in the process of 
 
 immersion, art. 194 77 
 
 Strength, comparative, of hydraulic mortars made with fresh 
 
 and sea-water, note 81 
 
 Stucco. — The employment of sugar or molasses advan- 
 tageous when buildings are to be stuccoed with rich 
 
 lime, note 84 
 
 composition of Mr. Higgins's patent stucco, note e 89 
 
 rapidity of absorption of carbonic acid by 172, 173 
 
 mode of preparing the Madras chunam, note x 176 
 
 defects in the manufacture of, note e 32 
 
 remedy against the speedy decay of, used in India, note .. 103 
 how stucco should be laid on, when exposed to the vicis- 
 situdes of the weather, note 104 
 
298 index. 
 
 Stucco, Grecian, perfection ot. art. 271 117 
 
 value of the carbonate of magnesia for 148 
 
 mode of preparing If. Martin's new stucco 191 
 
 compositions for the protection of, from the weather 212 
 
 progress of its decay in India, note 213 
 
 If. Loriot's process for hastening the " set," of use in 
 
 the composition of, note 2*20 
 
 explanation of the term "burnt stucco" 228 
 
 Sub-carbonate of lime, art. 30 14 
 
 Sugar increases the solubility of lime in water, note n 6 
 
 used to correct the bad qualities of rich limes, note 84 
 
 employed in stuccoes, note p. 84, and note x. 170 
 
 and in plaster, note 170 
 
 effect of a solution of sugar, on a paste of slaked rich 
 
 lime, note 127 
 
 Suitableness, mutual, of the ingredients with the various 
 limes in relation to the destination of the mortars or 
 cements for the preparation of which they are used, 
 
 art. 161— 104 64— GO 
 
 comparative table relating to 243 
 
 Sulphate of lime, experiment with 226 
 
 Sulphate of potash, a solution of, used with powdered gypsum 
 
 in the preparation of stucco 191 
 
 Sulphuretted hydrogen, nature of, note d 2 
 
 Sulphuric acid, its action on sands, art. 135 54 
 
 on the natural pouzzolanas, art. 139 55 
 
 on the artificial ones, art. 140 56 
 
 concentrated, effect on, by exposure to the air, note 171 
 
 substitute for, note 172 
 
 Sunderland, cement used in the construction of the docks at, 
 
 mate 60 
 
 Swine-stone, properties of, note s p 
 
 T. 
 
 Talc, its similarity to mica, note c 10 
 
 Tar, liquid, used as a wash to protect the hands of masons 
 
 in France from the action of the lime, art. 233 '.<■'> 
 
 coatings of common tar found to be the best remedy 
 against the speedy decay of mortars and cements in 
 
 India, note 108 
 
 Tarras, artificial, remark on, note 68 
 
 nature and properties of Dutch tarras, note 17B — 180 
 
INDEX. 299 
 
 Page 
 
 Tarns, composition of six sorts of 193 
 
 comparison of various artificial pouzzolanas with the 
 Italian pouzzolana, Audenack tarras, and aquafortis 
 
 cement 242 
 
 Tests to discover calcareous minerals, art. 1 1 
 
 the proper calcination of rich lime, note n 6 
 
 of the insoluble residue in rich limes, note o 7 
 
 of a mineral composed of rich lime, art. 23 11 
 
 the carbonising of hydrates of lime, art. 82, and note d. 35 
 
 the consistency of a good mortar, note c ~.... 3.3 
 
 the completeness of "extinction," art. 185 73 
 
 magnesia in limestone, note d 144 
 
 Thames ballast used in the manufacture of " concrete,*' note. 100 
 Theory of calcareous mortars and cements, art. 284 — 314. 
 
 124—139 
 the solidification of mortars always a subject of contro- 
 versy, art. 284 124 
 
 opinions of Black, Higgins, Achard and others, art. 285. 124 
 discovery and experiments of M. John, art. 285, 286. p. 124, 125 
 of adherence and cohesion, with the opinions of Macquer, 
 
 andGirard, art. 290 126, 127 
 
 observations upon this theory, note 127 
 
 opinions of Loriot and Lafaye, art. 291 128 
 
 definition of "adherence," art. 293 128 
 
 four remarkable cases presented by the theory of "aggre- 
 gates," art. 295 129 
 
 probable theoretical consequences of the first case, art. 
 
 296—301 129, 130 
 
 of the second case, art. 302, 303 131 
 
 of the third case, art. 304, 305 131 
 
 of the fourth case.art. 306 131 
 
 facts in support of the theory of aggregates, art. 308 — 133 
 observations on an assertion of M. John's, art. 312. p. 136, 137 
 M. Berthier's explanation of the solidification of hydraulic 
 
 cements, art. 313 138 
 
 the author's opinion as to chemical combination, art. 314. 
 
 p. 138, 139 
 Tile, fragments of, used as an ingredient in mortar, art. 124... 50 
 Tile-dust, the most ancient of the known artificial pouzzo- 
 lanas 182 
 
 Time, influence of, upon mortars and cements, art. 205, 206; p. 82, 83 
 
 cases of exception as to 201 
 
 Toulon, artificial limes employed in the harbour of, art. 46 ... 20 
 
:300 INDEX. 
 
 Treussart, General, on the expansion of limes by risking, note q. 7 
 
 remarks on the burning of Obcrnai lime, note d 17 
 
 on common lime, note c 29 
 
 experiment with a rich slaked lime long soured, and lime 
 
 fresh slaked, note 31) 
 
 on the deterioration of clay, by calcination, when it 
 
 contains lime, note 58 
 
 on artificial tarras, note o!> 
 
 clay recommended by, for the manufacture of pouzzolanas, 
 
 note f. 62 
 
 method of immersion proposed by, note 1 77 
 
 remarks on the solidification of mortars, note 130 
 
 experiment on the mixture of clay and lime, note i\'.'> 
 
 on the mixing of mortar, note 204, 205 
 
 Trituration, injurious effect of, when kept up beyond the time 
 
 necessary for the perfection of the mixture, art. 224... !)2 
 how a long-continued one will be favourable to rich limes, 
 
 art. 22G 93 
 
 Tuff, or tufa, meaning of the term, note e 4H 
 
 Turf, refuse of the combustion of, used as an ingredient in 
 
 mortar, art. 124 50 
 
 Turmeric paper, its use as a test for hydrates 171 
 
 Turpentine, spirits of, effect on slaked rich lime, note ... 127, 128 
 
 U. 
 
 " Using," or immersion, art. 192—200 75 — 80 
 
 See Immersion. 
 
 V. 
 
 Vapour. — A current of aqueous vapour accelerates the reduc- 
 tion of lime-stone into lime, note 152, !•>:• 
 
 this principle successfully applied by Lord Stanhope 163 
 
 properties of the vapour which rises during the process 
 
 of extinction 1G(J, 1G7 
 
 effect of the vapour from lime while slaking, on the 
 
 appetite of the workmen 1G7 
 
 Vicat, M., his opinion of magnesian lime-stones L50 
 
 Virgin sands, nature of, art. 106 4o 
 
 Vitruvius, authority of, as to Greek and Roman architecture, 
 
 art. 273, p. 118; cited art. 274 Ill) 
 
 his rules as to the qualities of lime repeated by mo- 
 dern authors J 15 
 
INDEX. 301 
 
 Page 
 
 Vitruvius, notice of the " Albaria Opera" of the Romans 175 
 
 his account of pouzzolana 178 > 179 
 
 Voids in a mass of stones, gravel, or sand, how to estimate, 
 note 
 
 Volcanic products, substitute for, art. 144 58 
 
 See Pouzzolanas. 
 
 \V. 
 
 87 
 
 122 
 
 34 
 
 Walls of modern houses will bear a comparison with ancient 
 
 ones, art. 280 
 
 Water, importance of the proportion of, in manufacturing mor- 
 tars, art. 80 
 
 its action on the hydrates of lime, art. 87—100 38—42 
 
 containing carbonic acid, dissolves carbonate of lime, note e. 30 
 effects produced by the superficial waters of the earth, note e. 33 
 proportion of absorbed by hydrates of lime, art. 88—93 ; p. 38, 39 
 combination of materials necessary to produce mortars, or 
 cements capable of acquiring great hardness in water, 
 
 art. 1G2 ; 64 
 
 care required in the employment of, in certain cases, art. 
 
 183, p. 72; art. 187, 188 74, 75 
 
 when water should not be added to hydraulic limes, note. 75 
 its action upon the parts of mortars and cements in im- 
 mediate contact with it, art. 201—204 ; p. 80—83, p. 199—201 
 experiments on hydraulic mortar made with fresh and 
 
 Ol 
 
 sea-water, note n 
 
 when it should be added to the lime in paste, art. 230 ... 94 
 a stiff mortar should be continually watered, art. 231 .... 94 
 the masonry to be watered during the hot weather, art. 234, p. 95 
 
 durability of certain mortars in, art. 243—247 102, 103 
 
 Mr. Smeaton's ** grouting" hardens under water, note 109 
 
 quickly absorbed by the Grecian pavements, art. 271 ... 117 
 mortar used by the Romans to prevent the infiltration of, 
 
 art. 277 il ° 
 
 substances possessing considerable tenacity when kneaded 
 
 1 %> 7 
 with, note "' 
 
 on the use of, in making mortar 204—206 
 
 Water-cements and mortars.— Notice of Colonel Pasley's ex- 
 periments on magnesia cement, note t 11 
 
 table of twenty compositions of water mortars 193 
 
 *M 
 
302 INDEX. 
 
 Page 
 Water-cements, and mortars.— Explanation of the deteriora- 
 tion of some water-cements and mortars, with experi- 
 ments of M. Petot 100 
 
 proportions of the mixtures for 243 
 
 Water-lime, notice of one found at Masulipatam, note 12 
 
 Wax. See Oil. 
 
 Weather, compositions for protecting stucco from the effects of, 212 
 
 See Air, Frost, Heat, Rain. 
 White, Mr., result of his experiments on Parker's and Mul- 
 
 grave's cements, note f. 123 
 
 White-wash, mode of preparing, art. 59 27 
 
 Winter, effects of, on mortars in France 104, 105 
 
 See Frost. 
 
 Y. 
 
 Yorkshire cement, analysis of the, note 22 
 
 '.. \\ 'XKlfall, l'nntcr, Angel Court, Skinner Street, London. 
 

 ■ utrA-enr tderdbjy . 
 
 j 'kit kun aMsivars perfect^' . This hibx «.-..- 
 
 
E X P L A X A HON 
 
 OF THE MACHINE FOR TRYING THE HARDNESS OI HYDRAULIC 
 MORTARS OR CEMENTS. 
 
 The average dimension of the different parts of the machine is 
 about an inch each way ; breadth 10 inches, height from the sole to 
 the lifting pulley, -2\\ inches. 
 
 Length of the rod a b, viz. : from a to c, 6 inches, from c to d, 
 for the part enclosed within the cylinder of lead, 1.69 inches, from 
 cl to b, to the adjustment of the point p, o\ inches; section \ inch 
 (nearly); length of lift 3.937 inches. 
 
 To make use of this machine, we commence by setting it up 
 perpendicularly; the rod a b being kept vertical. The cement to 
 be tried is placed underneath this rod, the vessel containing it being 
 v, edged up if necessary : the point of the rod then bears on the 
 surface of the cement. We read off at e, on the edge of the bent 
 index, the number of tenths of an inch marked on the scale. We 
 then lift it by means of the string/ to a given height, (fixed at 
 1.9685 inches for all our experiments,) after which, we release the 
 string suddenly, like the monkey of a pile-driving engine. The 
 point falls and penetrates more or less into the cement. We read 
 off the scale a second time, and by subtraction arrive at the quan- 
 tity of penetration. 
 
 The rod armed with its point weighs 15353.7 grains, or 2 lbs. 
 " OZ. .''. dr. Avoirdupois nearly. 
 
 i-latc U- 
 
■ >ruicnine 
 
 l 
 s or cements . 
 
 Sections ot~\arious pie h are 
 
 represented, the parts regenerated by (he Go 
 
 ■ ■'face - a. e /ractured surface 
 the needle . 
 
 - 
 ■ znJc . « 
 
 Urfacea 
 
 . i a. puxnk . 
 
 a b tUntah surface- b c. surface smoothed 
 
 part 
 a e pmn 
 
 
PI 
 
 
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