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FIFTEENTH EDITION LONDON CROSBY LOCKWOOD AND SON 7, STATIONERS' HALL COURT, LUDGATE HILL 1900 COA/S TA /f/o PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES. ADVERTISEMENT. When the fifth edition of this treatise appeared in 1865, by way of making room for the closely-printed Appendix of Notes and the Index which were then added, not to increase the size of the volume ^* Notes on Concrete/^ by Lieut.-Col. Sir William Denison, Royal Engineers, and Governor of Madras, with re- marks by Major- Gen. Sir William Reid^ of the same branch of the service, were omitted. Both these gentle- men, whose great professional experience entitles any opinion of theirs to much respect, deprecate the use of concrete in situations exposed to the alternate action of water and air in a climate like ours, and adduce the decayed state of the river-walls at Woolwich and Chatham, as communicated by General Sir C. Pasley, R.E., resulting from severe frost and rapid thaw, as evidence in confirmation. On the other hand, the concrete blocks at Dover Harbour, and in the break- water at Cherbourg, are shown to have answered per- fectly. The betoUy or rough rubble masonry, executed with cement or mortar by the Romans and during the middle ages, was, no doubt, very superior to our modern concrete, and though, on the whole, concrete has been found to answer admirably in some situations, in others it has failed ns conspicuously. In Mr. Dobson's trea- IBC-il ADVERTISEMENT. tise on Foundations and Concrete Work," which forms one of the volumes of this series, the reader will find an account of such beton works recently executed in the harbour of Algiers, which cannot fail to interest him. These few words were necessary to account for re- inserting Sir William Denison's ''^ Notes on Concrete," in the preliminary portion of the present volume, as some purchasers have expressed disftppointment at tht^ir exclusion from the former edition. PREFACE. The object the author of the following treatise had proposed to himself has been to put into as condensed a form as was consistent with the nature of the subject the knowledge and information dispersed through a numerous collection of authors who have treated there- upon. They are mostly in foreign languages ; for it is much to be regretted that our own scientific authorities have not thought it worth their while to occupy them- selves with this highly important branch of practical chemistry. The author has endeavoured, as conscientiously as possible, to avoid any questionable theory, or to quote as practical results any cases of whose correctness reasonable doubts might be entertained. There are, it is true, some theories propounded, some practices recommended, which are in direct contradiction to those usually received in England. They have not, however, been so advanced, unless the long experience of the most distinguished foreign engineers has war- ranted him in believing that our own practice is based entirely upon prejudice. We are, whether for good or for evil, essentially a practical nation — we have a dislike to theory, almost to analysis — we examine reluctantly any habit we have long followed. As in politics, so vi PREFACE. we are even in building. Our forefathers made mortar in one way, as perfect as their knowledge admitted, and doubtlessly that way was all that was practically necessary to secure the results then sought for — so we continue without examination in the track they beat for us. Our requirenxonts are^ hcwever, very different. Railroads, and the constructions they necessitate, have modified very materially the science of construction. In England, especially of late years, works have been executed which so immeasurably surpass in boldness anything which had been previously attempted, that we may be justified in expressing our surprise that so few attempts have been made to ascertain the real nature of the materials dealt with. Is it not to this neglect that we may attribute the numerous failures we read of? Some of these failures have been so remarkable, and some recent business transactions have displayed so singular an inattention to the nature and properties of lime, that the author deems it his right to provoke a discussion upon the subject, trusting that abler heads and hands will complete what he has so imperfectly begun. This branch of chemical knowledge has been so entirely ^^revolutionised" of late, so much uncer- tainty still remains to overshadow it, that it would be worse than folly to make any assertion which would lead to a belief that even the very fundamental prin- ciples were not, even now, susceptible of modification. That which is to be desired above all things is to rouse the professions of engineers and architects from the apathy with which they treat such subjects as the one before us — the very alpha and omega of their business. There is, however, something so invidious in attacking PREFACE. vii openly a generally received opinion, as the author has done with respect to the mode of making* mortar prac- tised in this country, page 66 and subsequently, that he throws him.s(y'lf upon the consideration of his pro- fessional bret)iren, in the hope that they will excuse his boldness on the score of his sincere desire to advance the true interests of science. At the same time the author would beg to protest very energetically against the " rule-of- thumb " methods which prevail in England in the manipulation of mor- tars. Architects and engineers, it is true, prescribe certain proportions of lime and sand to be employed ; but in practice " the foreman of the pug-mill," as the labourers call the person entrusted with this work, is the only authority, and he mixes the ingredients pre- cisely as it suits his fancy. In reality, mortar-making is a branch of practical chemistry — on a large scale, it is true — one which does not admit of the care and exactness of the laboratory. But the safety of a building often depends upon the perfection with which this operation is executed, and a certain arc^ount of scientific acquirements is necessary to insure that per- fection. JFor more than twenty-five years the author has been employed in building operations ; but in the whole course of his experience he never saw in any construction, in England, a measure used to ascertain the proportions of the ingredients employed for making mortar. We have seen of late years far too many accidents happen, too many absurdities committed, not to render it necessary to protest loudly against the carelessness with which the use of limes is regarded. One of the most important works executed of late years in London Vlii PREFACE. was built upon concrete made of stone lime, to which iron filings were added at a most tremendous and useless expense. Another large work was described in the specification to be executed with hydraulic lime ; and the engineer allowed common Medway stone lime to be used, although it is very far from being what is properly called an hydraulic lime. We have known viaducts with piers 100 feet high executed with chalk lime ; they have fallen, and been rebuilt with the hydraulic lime which only ought to have been em - ployed ; and we hear of pozzolana being used still in sea works. Surely, therefore, any examination of the nature of the materials to be used, which will here- after prevent a repetition of such mistakes, must be of service. The different scientific associations connected with building would confer a great boon upon the public if they would undertake a series of investigations upon the still undecided questions connected with the chemistry of their respective professions, and also if they would make a statistical statement of our mineral wealth, as far at least as building materials are con- cerned. We require a series of observations upon the geological and geographical distribution of the rocks able to furnish hydraulic limes. A synopsis of the building stones is also a desideratum ; for the Parlia- mentary report upon the subject was very far indeed from being a satisfactory solution of its difficulties. Such an inquiry should be undertaken under the auspices of the united bodies of the engineers and arcliitects. CONTENTS. I. Cursory view of the progress of discovery in the science connected with limes, &c 1 II. Chemical theory of the action of limes, and their classifica- tion 8 III. On the chemical nature and geological position of the stones which furnish the different sorts of lime . . .15 IV. On the calcination of limestones 24 V. On the artificial hydraulic limes 39 VI. On the slacking of limes , . . . . . . 46 VII. On the sands and other ingredients used in conjunction with lime to make mortar . • . . .53 VIII. On the makinsj of mortars . • . , . . . 66 IX. On concretes . . 71 X. On cements 78 XI. On the various cements composed of numerous extraneous ingredients 89 XII. On plastering 97 XIII. On stuccos , . . . 107 XIV. On the saltpetreing of limes, cements, and plasters , .112 Appendix *••«...* » 12] LIST OF iTJTHOES CONSULTED, AND OFTEN COPIED LITERALLY. Vitruvius — Be Architectiira. Plinius — Historia Natiiralis. St. Angustinus — Civitas Dei. Philosophical Magazine. Higgins on Calcareous Cements. Knapp's Applied Chemistry (Translation). Gmelin's Hand-Eook of Chemis- try. Bischoff's Chemical and Theoreti- cal Geology. Quarterly Journal of Chemical Society. Reports of Communications to Royal Institution. Transactions of Royal Institute of British Architects. Brande's Manual of Chemistry. Ure's Dictionary of the Arts and Sciences. Parnell's Applied Chemistry. Pasley on Limes and Cements. Smeaton's Account of Building Eddy stone Lighthouse. Godwin's Paper on Concretes. Trans. Brit. Arch. Blondel — Cours d'Arcnitecture, Rondelet — L'Art de Batir. Sganzin — Cours de Construction. Vicat — Recherches sur la Chaux. Translated by Col. Smith, of the Madras Engineers. Hassenfraz — L'Art de Calciner la Pierre Calcaire. Treussart — Memoires sur lea Chaux et Ciments. Claudel — Formules et Tables a rUsage de I'lngenieur. Petot — Recherches sur la Chau- fournerie. Pelouze et Fremy — Abrege de Chimie. Dumas — La Chimie appliquee aux Arts. Bert hi er — Traite des Essais par la Voie Seche. Encyclopedic Roret — L'Art du Chaufuurnier. Les Annalcs des Mines. Les Annales des Ponts et Chaus- sees. Les Annales du Genie Militaire. Les Comptes-Rendus de I'Aca demie des Sciences. La Bibliotheque Universelle de Geneve. Les Annales de Chimie et de Physique. Brard, Mineralogie appKqa^e aux Arts. Kuhlman, Eiperiences Chimiques ei Agnmomiques. NOTES ON CONCRETE. BY LIEUT.-COL. SIR WILLIAM DENISON, ROYAL ENGINEERS The very general employment of the mixture of lime and gravel, commonly known by the name of concrete, in all founda- tions where, from the nature of the soil, precautions against partial settlements appear necessary, and the great probability of an extension of its use, in situations where the materials of which it is composed are easily and cheaply procured, must of course render it a subject of great interest to the engineer. The paper which conveys information on this subject is an essay by Mr. G. Godwin. In this essay many instances are brought forward of the employment by the ancients of a mixture analogous to concrete, both for foundations and for walls. Several cases are also mentioned in which, of late years, it has been used advantageously for foundations by some of the most distinguished architects and civil engineers. In these latter instances, the pro- portion of the ingredients varies from one of lime and two of gravel, to one of lime and twelve of gravel ; the lime being in most cases Dorking lime, and the gravel Thames ballast.* The proportion, however, most commonly used now, in and about London, is one of lime to se\en of ballast, though, from experiments made at the building of the Westminster new IBridewell, it would appear that one of lime to eight of ballast made the most perfect concretion. Concrete compounded solely of lime and screened stones will never assume a consistence at all equal to that of which sand forms a part. The north wing of Buckingham Palace affords an instance * It is a question for consideration, whether a great variety of sizes in the mateiials used would not form the most solid as well as the hardest wall. The walls of the fortress of Ciudad Rodrigo, in Spain, are of concrete. The marks of the boards, which retained the semi-fluid matter in their construc- tion, are everywhere perfectly visible ; and besides sand and gravel there are everywhere large quantities of round boulder stones in the wall, from four to six inches in diameter, procured from the ground around the city, which 18 everywhere covered with them. — Major-Gen. Sir IV. Eeidy R.E, NOTES ON CONCRETE. of this. It was first erected on a mass of concrete composed oi lime and stones, and when subsequent alterations made it neces- sary to take down the building, and remove the foundation, this was found not to have concreted into a mass. Mr. Godwin states, as the result of several experiments, tliat two parts of stones and one of sand, with sufficient lime (dependent upon the quality of the material) to mcoke good mortar with the latter, formed the best concrete. As the quality of the concrete depends therefore on the goodness of the mortar composed of th6 lime and sand, and as this must vary with the quality of the lime, no fixed proportions can of course be laid down which will suit every case. The proportions must be determined by experiment, but in no case should the quantity of sand be less than double that of the lime. The best mode of compounding the concrete is to thoroughly mix the lime, previously ground, with the ballast in a dry state ; sufficient water being then thrown over it to effect a perfect mixture, it should be turned over at least twice with fchovels, and then wheeled away instantly for use. In some cases, where a gr^at quantity of concrete has to be used, it has been found advisable to employ a pug-mill to mix the ingredients ; in every case it should be used hot.* With regard to the quantity of water that should be employed in forming concrete, there is some difference of opinion ; but as it is usually desirable that the mass should set as rapidly as possible, it is not advisable to use more water than is necessary to bring about a perfect mixture of the ingredients. A great change of bulk takes place in the ingredients of concrete when mixed to- gether. A cubic yard of ballast, with the due proportion of lime and water, will not make a cubic yard of concrete. Mr. Godwin, from several experiments made with Thames ballast, concludes that the diminution is about one-fifth. To form a cubical yard therefore of concrete, the proportion of lime being one-eighth of the quantity of ballast, it requires about thirty cubic feet of ballast, and three and three-quarters cubic feet of ground lime, with suffi- cient water to effect the admixture. An expansion takes place in the concrete during the slaking of the lime, of which an important use has been made in the under- pinning of walls. The extent of this expansion has been found to * It is stated that the setting of ordinary lime results from the absorption of carbonic acid gas from the atmosphere. That the limes of mortars become sooner or later carbonates is most certain, but there is no proof that tnis 13 the cause of their cohesion ; indeed, there is every reason to doubt it. It is more probable that new attractive properties are acquired at the moment that hydrates of lime are formed from calcined lime and water, when in close union with silex, alumina, and some other substances, and that the properties first acquired at that time do not cease immediately, but continue, if undis- turbed, for ages. — Major-Gen, Sir W, Eeid, E.E, NOTES ON CONCRETE. xiii amount to about three- eighths of an inch to every foot in height, and the size thus gained the concrete never loses. The examples from which the above rules are deduced are principally of buildings erected in or about London ; the lime used IS chiefly from Dorking, and the ballast from the Thames. It is very desirable that a more extended collection of facts should be made, that the proportions of the materials, when other limes and gravels are used, should be stated, in order that some certain rules may be laid down by which the employment of concrete may be regulated under the various circumstances which continuall}^ pre- sent themselves in practice. The Dorking and Hailing limes are slightly hydraulic. Will common limes, such as chalk and common stone-lime, answer for forming foundations of concrete, where the soil, although damp, i* not exposed to running water ? Is it possible, even with hydraulic lime, to form a mass of concrete in running water? * If common lime will not answer, may it not be made efficient by a slight mixture of cement P These, and questions similar to these, are of great interest ,* and facts which elucidate them will be valuable contributions to the stock of knowledge on this subject. Description of the Method adopted by Mr. Taylor, for Underpinning zaith Concrete the Storehouses in Chatham Dock-yard. One of the large storehouses in Chatham dock-yard having for some time exhibited serious defects in its walls, the attention of the Admiralty was directed to it in the year 1834, and Mr. Taylor, the civil engineer and architect, was directed to report upon the best mode of obviating the evil. Upon investigation, the foundation of the storehouse (a building 540 feet in length, and 50 in breadth) was found to be in a very bad state ; the front wall, nearest the river, had originally been built upon piles, while the rear wall was laid upon an upper stratum of five or six inch plank, supported by two rows of transverse and * As all limes are soluble, more or less, in fresh water, this seems very doubtful. Any attempt to check a spring, or stop the course of running water with fresh concrete, will certainly fail. An instance of this was seen at Chatham, in constructing a dock : in the floor of the dock were several springs, which, in spite of every attempt to check them with concrete, continually made their way to the surface, and in every case it was found that the lime had been washed away from the mass, leaving only the gravel and sand behind. Eventually it was found necessary to carry away the water in an iron pipe, and discharge it into the drain outside the dock. Mr. Godwin states, that the dock at Woolwich failed from using separate moulded masses of concrete, instead of employing it as one whole. In this case, had separate masses been used, and laid in cement, the work might have been carried on, though it might perhaps have failed eventually, from the solubility of thi lime in fresh water affecting the blocks.— W. D. iiv NOTES ON CONCRETE. long'itudinal oak sleepers lying on the surface of the ground, which in this case was of a variable consistence, containing: flints bedded in a sort of clay, quite pervious to the water, which at high tide rose some height upon the foundation. The sleepers and heads of the piles at the front of the building, thus exposed to alternate moisture and dryness, were in a state of rapid decay ; in some places they were even reduced to a powder ; and it was possible for a man to move under the walls in the space previously occupied by the timber. In the rear, the case was pretty much the same ; the sleepers were universally in a state of decay, but in some places were much further advanced towards decomposition than in others. The state of the storehouse requiring immediate attention, it was resolved to attempt to underpin the walls. This the patentee for the new description of concrete, or artificial stone, undertook to do, having adopted a plan proposed by Mr. Taylor, for forcing the soft concrete against the under part of the wall ; and he proceeded to execute his contract in the following manner. I must premise, that the storehouse was vaulted underneath, and that the piers, or cross walls, required as mudi underpinning as any other part of the building. The walls were laid open to their bottom, both inside and outside the building: in the front, the heads of the piles and the sleepers were removed for a depth of about four feet below the bottom of the wall, and for lengths of about five feet at one time. In the rear, all the planks and sleepers were removed for the same distance. A mass of concrete, composed of one-eighth of Hailing lime (re- duced to a powder by grinding, and in a perfectly caustic state), and seven- eighths of Thames ballast, mixed up with so much boiling water as to reduce the whole to a pasty consistence, was then thrown from a height of about fifteen feet underneath the wall : it was allowed to project about a foot on each side, where it was confined by planks, and after being roughly levelled, it was well rammed, to give it as much consistence as possible. This mass was raised about three feet, or to within one foot of the bottom of the wall ; it was then carefully levelled, and covered with haK- inch slates. A kind of framework was then placed on the slates, consisting of two cross-plates of iron, placed perpendicularly to the direction of the wall, about one foot wide, and long enough to pro- ject about one foot on each side of the wall. To these were fixed two frames parallel to the wall, about foui feet long, each carrying two sockets for screws. Within these frames were placed two movable planks, long enough to pass just free between the cross-plates, and wide enough to fit nearly the space between the slates and the bottom of the wall. U|)on these planks were sockets for the heads of the two screws, by which the planks were pushed forward, or withdrawr at pleasure. NOTES ON CONCRETE. XV Wlien the apparatus was fixed, and the movable planks ready on both sides of the wall, about two barrowfuls of concrete, mixed as stated, were thrown in from above ; the workmen below then commenced turning the screws on each side simultaneously, moving the two planks towards the centre of the wall, and forcing the concrete before them into all the vacant spaces, and against the bottom of the wall. "When the plank was forced forward as far as it would go, by the strength of two men to each screw, the con- crete was allowed to rest for about five or ten minutes, by which time it had set hard enough to stand by itself, and its expansion in the act of setting completed what the pressure of the screws might have left undone. The planks were then withdrawn, another charge thrown in on each side, and compressed as before, and this was continued till the whole space between the frames was filled with concrete. The screws were then removed, the boards and frames unbolted and taken out, and lastly, the side-plates were withdrawn, leaving an interval of about three-quarters of an inch between each mass of concrete, which space was afterwards filled in with grout. The above description is given from notes taken at the time. The proportion of lime to gravel is as one to six ; and such is the efficiency of the concrete in the mode in which it was applied, that no settlement has taken place since the work was completed. Again, circumstances have caused me, since the foregoing was written, to pay particular attention to the application that has been made of late years of concrete, or artificial stone, to the various purposes of construction 5 and I shall now briefly state the experiments that I have made or witnessed on this subject, and the conclusions that may be fairly deduced from the results of these experiments. The first experiment was made with the view of ascertaining whether a mass of concrete made with Aberthaw lime would resist the chemical action of water : for this purpose a small block, which had been prepared for nearly two years, was immersed for some time in distilled water, and upon applying the proper test to the water, it was found to have combined with a portion of the lime in the block. Having mentioned this circumstance to Sir M. J'araday, he suggested that it was probable the block contained a (][uantity of lime in an uncombined state ; and recommended that it should be placed in a running stream for some time, in order to wash it thoroughly : this was accordingly done, by suspending the block for two months under a hulk in the river, after which, having again soaked it in distilled water for a week, hardly any trace of lime could be detected in the water by the application of the most delicate tests. This experiment then appears to prove that concrete, composed of proper materials (hydraulic lime and XVI NOTES ON CONCRETE. gravel), does not suffer by the chemical action of water. Experi- ment No. 2 was made in order to ascertain the strength of a block of concrete 2 ft. 6 in. long, 1 ft. 6 in. broad, and 1 ft. deep, which had been made for two years, and would have been used as a stretcher in the river wall at Woolwich. A shackle was placed round the centre of the block, and two others at the extremities, at the distance of 11 1 inches each from the centre : a force being applied to the two end shackles by means of the hydraulic press, the block broke in the centre, under a strain of 4 tons 11 cwt. I did not prosecute the experiment upon the strength of this mate- rial any further, having sent down some blocks to Gen. Sir C. Pasley, H.E., who had investigated the same subject, and the results of the experiments are as follows : — Three stones, each 3 feet long, 18 inches wide, and 15 inches deep, were supported upon props 27 inches apart weights being then applied to the centre of each, the first broke with 6,285 lbs., the second with 5,141 lbs., and the third with 2,930 lbs. This last had probably some flaw j taking therefore the mean of the two first only, the result will be 5,713 lbs. A piece of York paving, 7^ inches deep, 13 inches wide, and the same distance (27 inches) between the supports, broke with a weight of 13,512 lbs. The value of the constant S, in these two cases, deduced from the formula S=~^^ will be for concrete 9*5, and for York paving 124*7, being about in the proportion of 1 to 13. The experiments I have had the opportunity of witnessing, and which offer by far the most instructive results, have been the practical application of concrete to the construction of river walls at Woolwich and Chatham. In one instance, at Woolwich, it has been applied in mass, the wall having been constructed in the same manner as the Brighton sea-wall : in both the other in- stances at Woolwich and Chatham, the concrete was formed into blocks, which were allowed ample time to set and harden before they were built into the face of the wall. At Woolwich the river-wall is for the most part founded upon piles ; its height above the piles is about 24 feet, the thickness at iDottom 9 feet, at top 5 feet, with a slope or batter in front of 3 feet in 22 : the face of this wall is composed of the above-mentioned blocks, which are laid in cement, in courses 1 ft. 6 in. in height, the headers and stretchers in the course being each 2 ft. 6 in. long, the former having a bed of 2 feet, while the latter have only 1 foot J behind the facing the rough concrete is thrown in to com- plete the thickness of the wall and counter-forts. Both the blocks and the rough concrete are composed of lime and gravel, in the roportion of 1 to 7, and brought to the proper consistence with oiling water; but the blocks are, or ought to be, made with NOTES ON CONCRETE. Aberthaw lime, while Dorking lime is used for the rest of the work. The blocks are cast in moulds, and are submitted to pres - Bure while setting : a coating of finer stuJ^ is given to the face for the sake of appearance. The whole of the wall is built by tide work, and in the lower part therefore the backing of rough con- crete has hardly time to set before it is covered by the tide ; the water, however, in this instance, appears to affect the surface of the mass only, the interior, at the depth of a few inches, being generally speaking dry, and of a moderate degree of hardness when examined after the retirement of the tide. During the summer the action of the water from day to day upon the facing of the river- wall was not perceptible ; the surface still remained moderately hard occasionally portions of the fine facing separated from the rest of the block, owing, it was said, sometimes to want of care in the original construction, sometimes to injuries caused by boats or vessels striking the wall : in these cases, however, a new facing of cement was applied, and before the winter the general appearance of the wall was to a certain extent satisfactory. During the hard frost, however, evidences of failure began to show themselves ; and as soon as the thaw allowed a thorough in- spection of the face of the wall to be made, it was found that hardly a single block had escaped without some damage ; in many instances the whole face had peeled ofiE to the depth of half an inch ,* and at one spot, where a drain discharged itself into the river from a height of about six or eight feet, the back action of the water after its fall had worn away the lower courses to the depth of some inches : these were the evidences of the action of frost and water combined upon the best constructed wall at Woolwich. At Chatham they were of the same character, but the damage done to the wall was much greater. The portion of river-wall at Woolwich which was built with rough concrete had been severely injured by the common action of the water before the frost ; and the latter has only caused the destruction of the face to proceed with greater rapidity. Since the frost I have examined the walls of a school near Blackheath, which was built with concrete some years ago : 1 found that at the ground line, where the drip of the water had acted, the concrete was soft, and yielded easily to any force applied, while the walls above were very fairly hard, and seemed to have stood very well. These then are the facts I have to submit ; and I think they afford sufficient grounds for asserting, that in climates like ours, in situations exposed to the alternate action of water and air, concrete cannot be advantageously used as a building material, the apparent economy, caused by the cheapness of the material employed, being more than compensated for by the frequency of repairs. From the circumstance that at Chatham some of the blocks remain to a xviii NOTES ON CONCRETE. certain extent uninjured, whilst others close to them, and exposeC to exactly the same action, are completely decomposed, one would be tempted to infer that proper caution had not been used in the selection of the lime of which the latter were composed ; and that had Aberthaw lime been used throughout, the damage would not have been near so great. But even in this case, although the frost might not have produced so much effect upon the work, and should concrete be considered perfectly impervious to chemical action, yet the want of tenacity, or of power to resist a very trifling force, renders it peculiarly inapplicable to situations where, as in wharf- walls, it will be exposed to damage from the collision of vessels and floating bodies, in addition to the constant mechanical action of the water. Where, however, it is protected from these causes of destruction, as in foundations, its value is unquestionable; and even in the backing of retaining walls, revetments, &c., it may in many cases be advantageously applied, taking care to allow it time to set before any great pressure is thrown upon the wall. The specific gravity of concrete is from 120 to 130, about the same an that of brickwork, W. DENISONf LiEUJT.-CoL. ON LIMES, CALCAREOUS CEMEiNTS, MORTARS, STUCCOS, AND CONCRETES. CHAPTER L CURSORY VIEW OF THE PROGRESS OF DISCOVERY IN THE SCIENCE CONNECTED V^ITH LIMES, ETC. The use of some cementing material to bind together the small stones or other materials employed in the construction of walls^ and also for the purpose of giving them a smooth surface adapted to receive polychromic or other decoration, dates from a very high antiquity. It is, however, probable that it was subsequently to the discovery of the art of brickmaking, that the ancients arrived at that of burning lime. Indeed, the use of moistened clay, which was found to have a certain ductility, and to harden also in drying, was likely to have preceded that of lime, as a cement; for the quali- ties and the mode of obtaining the latter were of a nature to require long study and great experience. The Assyrians and Babylonians appear to have em- ployed either moistened clay, or the bitumen so plenti- fully supplied by the springs in their country. Some doubt, however, exists as to whether these people did ever really use mortar. Captain Mignan sometimes 2 ON LIMES^ CALCAREOUS CEMENTS, talks of bricks which were cemented together with a coarse layer of lime. ^^At others/' he says, that "be- tween the brickwork at irregular distances a layer o{ white substance is perceptible, varying from in. to 1 in. in thickness, not unlike burnt gypsum or the sul- phate of lime. From the peculiarly mollified state of the bricks I apprehend this white powder is nothing more than common earth, which has undergone this change by the influence of the air on the clay compos- ing the bricks/' The Egyptians, however, used mortar in the con- struction of their pyramids ; and Mr. Cresy has given an analysis of that employed in the construction of the pyramid of Cheops, which shows that they possessed nearly as much practical knowledge of the subject as we do at the present day. (Theoi'y and Practice of Engineering, pages 7 17 and 718.) Sir Gardner Wilkinson also mentions that the inte- riors of some of the pyramids were stuccoed, but he does not give any description by which we might even guess at the nature of the materials employed. The Greeks, at a very early period of their civihza- tion, used compositions, of which lime was the base, to cover the walls constructed of unburnt bricks. Accord- ing to Plinius and Vitruvius, the palace of Croesus, the Mausoleum, and the palace of Attains were protected, or ornamented, in this manner. According to Strabo, the walls of Tyre were built of stone set with gypsum, a very common material apparently in Asia Minor, and the centre of the old Assyrian civilization. In Italy the first people who employed mortar in their buildings were the Etruscans. Gori, in his Mu- 8€um Etruscuniy mentions that in the tombs found neai MORTARS^ STUCCOS5 AND CONCRETES. 3 their ancient cities^ such as Iguvium, Clusium^ Volterra^ the constructions were made with mortar. Near Vol- terra also^ in 1 739, a cistern, entirely built and lined with that materia], was discovered. A branch of this nation, known under the name of Tyrrhenians, were considered by the Greeks to have invented, or at least considerably improved, the art of masonry. The most ancient authors, such as Homer, Hesiod, Herodotus, and Thacydides, speak of them under that name, and call their walls by the word tyrsis,^^ instead of " tei- chos,^^ the one used by the more modern authors. The word ^^tyrsis^^ is supposed to have had the same signification in the Etruscan language; and the towers erected for the purpose of fortification were also called " tyrseis by the Greeks. The Romans, as is well known, derived all their knowledge of the arts either from the Etruscans or the Greeks. They added little to the general stock of knowledge as to the use of limes, but Vitruvius is the first author upon the subject whose works have descended to us. The text of this remarkable man^s work shows that the ancients, although they adopted a difi'erent scientific phraseology from that in fashion in the 18th century, knew as much of the laws regulat- ing this branch of chemistry as the moderns of that time. For all practical purposes Vitruvius is even now as safe a guide as most of the authors who treated the subject subsequently; at least until we arrive at the researches of M. Vicat. (See Viti^uviuSy book ii., ch. 5.) Plinius and St. Augustin treat occasionally about limes and cements ; the former, principally to complain of the malpractices of the builders ; the latter, to seek metaphysical comparisons. On the revival of litera^ 4 ON LIMES, CALCAREOUS CEMENTS, ture, after the Cimmerian darkness of the middle ages, which it is now so much the fashion to admire, the authors who treated upon the art of building, such as Alberti, Palladio, Barbaro, Philibert de POrme, Sca- mozzi, Savot, Bullet, and Blondel, did little more than follow in the traces of Vitruvius. There was a differ- ence of opinion, it is true, as to the quality of sand which it was most advisable to use : some new limes, some puzzolanos, terrass, and ashes, were employed to give to certain other limes the faculty of setting under water : but until about the middle of the last century no advance seems to have been made towards ascer- taining the principles which regulate this branch of chemistry. It is, indeed, worthy of remark, that the more useful arts appear to be carefully studied until the practical results they are capable of producing are ascertained: then the rules draw^n from such results are received implicitly for a long period, and any attempt to ascer- tain the laws which regulate them is regarded as use- less. We, the human race, appear to attain empirical knowledge quickly; scientific knowledge arrives at a much later period. So it was with limes : so it is with the casting and puddling of iron — a subject equally, if not more, interesting. The first serious attempt made to ascertain the causes which gave some limes the power of setting under w^ater, and which modified their rates of harden- ing, was made by the father of civil engineering in England, John Smeaton, in 1756. Being at that time engaged in the construction of the Eddystone Light- house, he found it necessary to have a cement capable of hardening at once in the water ; he therefore began MORTARS, STUCCOS, AND CONCRETES. 5 a series of experiments, which are detailed in his account of the building of that work 5 book iii., chap. 3. The results he arrived at were very remarkable, not only for their practical utility, but also as an illustration of the ease with which a very acute observer may stop short on this side of the attainment of a great truth. Smeaton found that the commonly received opinion that the hardest stones gave the best limes, was only true as far as regarded each quality considered by itself. That is to say, that of limes not fit to be used as "water cements,^^ those made of the hardest stones were the best for certain uses in the air; but that whether obtained from the hardest marble, or the soft- est chalk, such limes were equally useless when em- ployed under water. He found that all the limes which could set under water were obtained from the calcination of such limestones as contained a large por- tion of clay in their composition. His experiments led him to use, for the important w^ork of the light- house, a cement compounded of blue lias lime from Aberthaw, and of puzzolano brought from Civita Vec- chia, near Rome. Even at the present day it would be difficult to employ a better material than this, except- ing that the price would ensure a preference to the Roman cement, then unknown. But Smeaton, after giving a table showing that all the water limes were obtained from limestones containing clay in chemical combination, in proportions varying from -fy to -—-^ goes on to say, "that it remains a curious question, which I must leave to the learned naturalist and chemist, why an intermediate mixture of clay in the composition of limestone of any kind, either hard or soft; should render it capable of setting in water in a 6 ON LIMES^ CALCAREOUS CEMENTS, manner no pure lime, I have yet seen, from any kind of stone whatsoever, has been capable of doing. It is easy to add clay in any proportion to a pure lime, but it produces no such effect : it is easy to add brick dust, either finely or coarsely powdered, to such lime in any proportion also; but this seems unattended witli any other eflfect than what arises from other bodies become porous and spongy, and therefore absorbent of water as already hinted, and excepting what may reasonably be attributed to the irony particles that red brick-dust may contain. In short, I have as yet found no treatment of pure calcareous lime that rendered it more fit to set in water than it is by nature, except what is to be derived from the admixture of trass, puzzolano, and some ferruginous substance of a similar nature.^^ The stress Smeaton laid upon the presence of the ferruginous substance, led many chemists to attribute the hydraulicity of limes to the presence of the oxide of iron. Guyton de Morveau and Bergmann, finding the oxide of manganese in the hydraulic limes they analyzed, regarded it as producing the effect in ques- tion. Their researches were nearly contemporaneous with those of Smeaton. Thirty years afterwards, De Saussure observed that the lime of the Chamouni set under water, though entirely without manganese ; and he, therefore, like Smeaton, attributed this faculty to the presence of clay. In 1813, Colets Descotils, on analyzing the compact marl of Senonches, which yields on calcination a lime capable of setting rapidly under water, found in it nearly one quarter of silex, which led nim to the conclusion that the cause of the phenomenon consisted in the presence of a large quantity of siliceous matter, disseminated in very fine particles in the tissue of the stone itself. MORTARS^ STUCCOS, AND CONCRETES. 7 To continue the quotation from Vicat : " The opinion of Descotils did not weaken or invalidate that of De Saussure, since clay contains generally more silex than alumina; and the two chemists agreed^ moreover^ in considering the oxide of manganese^ if not as a useless element^ at least as one which was not essential. This was the state of the question in 1813; and it was with the intention of putting an end to all doubts upon the subject that I decided at that epoch to proceed syn- thetically, and to compose hydraulic limes entirely, by burning different mixtures of common lime, slacked spontaneously, with clay: the success surpassed my hopes. All the clays, rich and soft to the touch, gave the same results; my experiments were repeated in Paris, in 1817? with the limes of Cleyes and of Champigny, and the clay from Vauvres ; further expe- riments, by Mr. St. Leger, in England, and by M. Raucourt de Charleville, in Russia, confirmed the results previously obtained.^^ The subsequent researches of the most eminent chemists and engineers must be considered to have confirmed the theoretical opinion which guided Vicat in his experiments, with a few recent but important rectifications of detail. Berthier, Dumas, Hassenfraz, Treussart, Thenard, Gay Lussac, Petot, Sganzin, Girard, Parandier, Minard, Kuhlmann, in France — John of Berlin, and Fuchs of Munich — Pasley, Ansted, and Way, in our own country ' — as well as most of the scientific authors who have treated upon the subject throughout the globe — have arrived at nearly the same conclusions as Vicat with respect to the causes which influence the different actions of lime. 8 On LIMJIS, CALCAllEOUS CEMENTS, The following condensed statement of the usually received theory may, therefore, be taken as represent- ing the actual state of this branch of chemical and engineering science. CHAPTER II. CHEMICAL THEORY OF THE ACTION OF LIMES, AND THEIR CLASSIFICATION. Pure lime, or calcium, as regarded in chemistry, is a metallic oxide, having strong alkaline properties. It is caustic, and turns green the vegetable blues. Its specific gravity, according to Kirwan, is 2*3 ; accord- ing to Berzelius, its atomic weight is 20*5 ; according to Dumas, it is 20. It is very difficult of fusion, but greatly assists the fusion of other earthy bodies. At an ordinary temperature, pure water can dissolve y-fT^ of its own weight of lime; but, when boiling, it dis- solves less. Dr. Dalton states that water at the fol- lowing degrees of the centigrade scale will dissolve the following proportions of lime, and of its hydrate ; viz., At 15° 5 centigrade it dissolves of lime, and ^5^-^ of the hydrate. 50° 0 T^f-^ jy y^-jj „ 100° 0 p „ Tiro »» 'ws'S »» The pure metallic base never occurs in nature, nor does pure lime, its protoxide. If the pure lime were exposed for a period, however short, it would absorb the water and carbonic acid gas of the atmosphere. We therefore find it in the state of the bi-carbonatC; MORTARS^ STUCCOSj AND CONCRETES. 9 the carbonate and suhcarbonate^ of lime^ in which it is very extensively diffused. The lime of commerce is obtained by the calcination of these carbonates, and the process consists in driving off by heat the carbonic acid gas which is in combination. The minerals which contain the carbonate of lime, and which are designated under the generic name of limestones/^ or " calcareous stones/^ are of very vari- ous natures. They are mostly composed of carbonate of lime, of magnesia, of oxide of iron, of manganese, of silica, and of alumina, combined in variable propor- tions; and they are also found with a mechanical admixture of clay (either bituminous or not), of quartzose sand, and of numerous other substances. The name of limestone is more especially applied to such of the above mixtures as contain at least one half of their weight of carbonate of lime. Mineral- ogists distinguish the subdivisions by the names of the ^^argillaceous, magnesian, sandy, ferruginous, bitu- minous, fetid,^^ &c. These subdivisions, again, are often characterized by varieties of form and contex- ture, which are known specifically under the names of '''^lamellar, sacchroid, granular, compact, oolitic, chalky, pulverulent, pseudomorphic, concreted,^^ &c., &c. This liomenclature is important ; for every descrip- tion of limestone yields a lime of different quality, dis- tinct in colour and weight, in its avidity for water, and especially in the degree of hardness it is capable of assuming when made into mortar. But the physical and mechanical nature of a stone are far from being certain guides as to the quality of the lime it can yield. A chemical analysis of a hand sample also frequently gives different results from those obtained in mactice. 10 OiV LIMES, CALCAREOUS CEMENTS, Experience alone should be the final guide of the engineer or of the builder. The carbonate of lime occurs in nearly all the geolo- gical formations, but it is scarce in the primary ones. In the transition rocks it is more abundant; and it constitutes the great mass of the secondary and tertiary formations. It is worked largely, either for the pur- pose of obtaining building stones, or for burning for lime. The calcareous rocks of the primary formations, and of the early transition series, furnish the greater number of stones which are worked under the name of marbles. The secondary and tertiary calcareous rocks contain the mixtures of clay and other ingredients which render them the most adapted to furnish limes. After a calcination sufficient to disengage the car- bonic acid gas, the limestone will be found to have diminished considerably in weight, and the resulting material possesses the property of absorbing water, either with or without a disengagement of heat. It cracks and falls to pieces whilst thus combining with the water, or slacking, as the workmen call the process of passing into the state of a hydrate of lime. The principal characteristics of the hydrate of lime are that it is white and pulverulent; much less caustic than quick lime. It parts easily with the first portions of its water of combination if exposed to fire, or even to mere friction ; but it requires a very high degree of heat to cause it to part with the whole of the water. There is still a great degree of uncertainty as to the chemical action of the hydrates. Generally speaking, they are considered not to absorb oxygen ; but Treus- fiart supposes that they do so, and that they undergo important modifications in consequence. The quantity MORTARS^ STUCCOS5 AND CEMENTS. 11 of water that limes solidify in passing to the state of hydrates, is also a question upon which much doubt exists amongst chemists. Berzelius supposed that the hydrates were formed of water and the metallic oxides, in such proportions as that the quantity of oxygen contained in the water should be equal to the oxygen contained in the oxide. Thus/ the hydrate of lime absorbs carbonic acid gas from the air, or even (m\^h the best limes) from water, if immersed therein; and after a period, varying with the nature of the limestones from which it is prepared, it solidifies with an imper- fect crystallization. Whilst passing into this state, 100 parts of pure lime, which contain 28*16 parts of oxygen, Berzelius supposes to combine with 32*1 parts of water which contain also 28*3 of oxygen. Thenard, however^ does not admit this law to hold in all cases ; and cer- tainly some of Treussart's experiments would induce us to hesitate before we admit it. The hydrates, under the action of the voltaic pile, assume the same action as the oxides. Bodies capable of decomposing water, always acts upon them, even upon such as heat does not affect; acids also decompose the hydrates when these are produced from the oxides of mineral bases. If, for the purposes of classification, we observe the phenomena which attend the slacking and harden- ing, or, to use the workman^s phrase, the setting of lime, w^e find that they may be ranged in the following order. The lime in these experiments is supposed to be perfectly fresh, and is to be immersed in a small l;asket, in perfectly pure water, for the space of five or six seconds only. It is then to be allowed to dry, 01 at least the loose uncombined water is allowed to 12 ON LIMES, CALCAREOUS CEMENTS, run off, and the contents of the basket are then emptiet? into a stone or iron mortar. 1. The lime hisses, crackles, swells, gives off a large quantity of very hot vapour, and falls into powder instantly : or, 2. The lime remains inert for a period of variable duration, but which does not exceed five or six minutes; after which the phenomena above described declare themselves energetically : or, 3. The lime, again, remains inert for five or six minutes, or the period of its inactivity may extend to a quarter of an hour. It then begins to give off vapour and to crack, without decrepitating to any great extent. The steam formed is less abundant, and the evolution of heat is less than in the two former cases : or, 4. The phenomena only commence an hour after the immersion of the lime, and sometimes even after a lapse of time still more considerable. The lime cracks, without decrepitation, it gives off little steam or heat : or, 5. The phenomena commence at epochs which are very variable, and in fact hardly perceptible; the heat given off is only distinguishable by the touch; the lime does not fall easily into powder, and at times it does not do so at all. Before the effervescence has entirely disappeared, the slacking of the lime should be completed. As Boon as the cracking and falling to pieces begin, water should be poured into the vase, not upon the lime, but by the side, so that it may flow freely to the bottom, from whence it would be absorbed by the portions of the lime in a sufficiently advanced state of chemical A'^tion to require it. The compost should be frequently MORTARS, STUCCOS, AND CONCRETES. 13 ,> 71 2-5 7 3 4 8 Breteuil . Black >> 47 11 23 7 Kaiserlautern 49 15 30 13 Mont Blanc Scoriae 23 1 2 1 45 24 » 18 1 14 1 61 9 It 9 1 10 8 56 3 Rives . . >» 29 18 2 44 4 On comparing these results with those obtained from the analysis of the puzzolano and trass, we perceive at once a very remarkable difference in the proportion of the ingredients, as we also find that the scoriae and the slag differ from one another. The slag, when the fur- naces are well managed, contains but little iron; the scoriee contain so much that they are at the present day almost invariably worked over again in the most economically managed iron works, producing, it is true, very inferior iron. When ground into powder, the scoriae and slags, which contain a large proportion of the mineral oxides, make very good mortars if mixed with middlingly or perfectly hydraulic limes. With the former it is not advisable to use them in positions where the mortars M^ould be exposed to the action of running water ; with the latter they may be used to replace sand, sometimes with advantage. (See Appendix C, page 125.) Coal cinders, according to Weigleb, Dolomieu, and Panzerberg, contain usually 44 parts of silica, 17 of alumina^ 5 of lime, and 34 of oxide of iron. When MORTARS^ STUCCOS^ AND CONCRETES. 63 properly mixed, they appear to render the rich limes moderately hydraulic. Great care requires to be exer- cised in their manipulation to proportion the quantity of water used, for they absorb it with such avidity that, unless there be a large quantity present, they abstract it from the hydrate of lime, and render the crystalliza- tion of the latter imperfect. Workmen characterise this action by saying that the lime becomes short; in fact, its coherent powers are much diminished. If, however, the necessary precautions be taken, coal cinders may be usefully employed for works out of the water. Wood cinders are often objectionable in consequence of the excess of alkali they contain : if this be removed by washing, they may occasionally be useful in the absence of other materials capable of communicating hydraulic properties. Peat ashes have never been tried in any scientific manner ; but there does not appear to be any reason why they should not be as useful as those of wood. In page 36 we already noticed the use of the clinkers which fall through the fire-bars of the limekilns. Their hydraulic properties appear to arise from the mixture of the lime in a very minute state with the silicate of alu- mina of the cinders. In Belgium they are very largely and very successfully used for canal and river works under the name of " cendree de Tournay.^^ Vicat classes the different materials named and de- scribed above still further, according to the energy of their action upon the limes with which they are mixed. He calls "very energetic^' any substance which, after being mingled with lime slacked in the usual manner, and brought to the consistence of a stiff paste, produces 64 ON LIMES, CALCAREOUS CEMENT, a mortar capable of setting from the first to the third day; of acquiring after the lapse of twelve months a degree of hardness equal to that of a good brick; and of giving a dry powder if sawn with a tooth saw after that time. Simply energetic/^ any substance w^hich will deter- mine the setting from the fourth to the eighth day ; and which is capable of acquiring after twelve months the consistence of a soft stone, and of giving a damp powder under the tooth saw. Slightly energetic/^ when the setting only takes place between the tenth and the twentieth day ; the con- sistency of hard soap would be acquired after twelve months, and the mortar would then clog the tooth saw. " Inert/^ when the materials, if mixed with rich limes, exert no influence upon their action under water. In all these cases the mortars are to be immersed im- mediately. It is, moreover, to be observed that the degree of hardness attained is the only invariable cha- racteristic, for the time of setting varies very consider- ably. Having established these differences, Vicat ranges the common sands amongst the materials he classifies as ^^inert/^ The arenes and grauwacke rocks yield materials which are but slightly energetic. The puz- zolanos, whether natural or artificial, are classed occa- sionally as being simply energetic or very energetic, as the case may be. Experience, however, shows that the artificial puzzolanos should only be ranged in the first class. These different actions appear to be owing to the affinity of the several materials for the lime. Vicat found, in fact, that, if treated by acids and by lime MORTARS^ STUCCOS^ AND CONCRETES. 65 water, they were distinguished from one another as follows : — the inert materials resisted the action of acids, unless when calcareous sand was operated upon, and were totally without influence, even upon boiling lime water. The slightly energetic materials yielded in a trifling degree to the acids, and took up a small pro- portion of the lime from the lime water. The ener- getic, and very energetic, materials were powerfully affected by the acids, and took up a very notable por- tion of the lime in solution. The same author gives, as the result of forty years' experience, the following tables of the materials it is advisable to mix together to obtain the best results in the respective cases mentioned. He supposes that the architect or engineer has under hand the four descrip- tions of lime, and the different substances to be mixed with them; and that in the first case he desires to obtain a mortar capable of attaining a great degree of hardness under water, under ground, or in places where there is a constant humidity ; in the second case, where it is desired to obtain a mortar able to set rapidly in the open air, to resist rain, and the changes of the weather. He recommends, then, to mix vrith CASE THE FIRST. Rich limes. IModerately hydraulic. Hydraulic. Eminently hydraulic. The very ener- getic puzzola- nos, either na- tural or arti- ficial. The simply ener- getic puzzolanos. The very energetic ditto, mixed with half sand or other inert matter. The energetic are- nas, or grauwacke rocks. The slightly ener- getic puzzolanos. The energetic ditto, with half sand or inert m.atters. The slightly ener- getic arenes, &c. The inert matters such as sand, &c. Slag, scoriae, &c. 86 ON LIMES, CALCAREOUS CEMENTS^ CASE THE SECOND Rich limes. Moderately hydraulic. Hydraulic. Eminently hydraulic. No ingredient can attain the object. No ingredient can perfectly attain the object. Any description of sand ; pounded quartz. Dust of pounded hmestone and other inert mat- ters. Any description of sand ; pounded quartz. Dust of pounded hmestone and other inert mat- ters. General Treussart, however^ does not agree with Vicat in supposing that the chalk, or rather the rich limes, cannot be rendered capable of setting by the mixture of puzzolanos ; and, indeed, the experience of almost all builders would lead us to believe that Vicat has, in this case, been carried away by the love of theory. Gauthey, in his work upon the construction of bridges, however, seems rather to lean to Vicat's opinion ; which is confirmed, it must be added, by the experience of the engineers of Toulon and Marseilles. CHAPTER VIII. ON THE MAKING OF MORTARS. The making of mortar comprehends the slacking of the lime and the mixture of the ingredients worked up with it. As we have already seen, both the former px^ocess and the nature of the latter differ, according to the nature of the lime to be dealt with. It is, however, a universal rule, in contradiction to the slovenly prac- tice of London builders, that all limes, of what nature soever, should be reduced to a paste before being mixed with the other ingredients. MORTARS^ STUCCOS^ AND CONCRETiSS. 67 People who have not studied the action of the hy- drates in a scientific and consecutive manner^ oppose the introduction of the previous manipulation of the lime on the score of the extra expense^ and on the pre- tence that the lime loses in strength thereby. As to the objection of the expense^ that must of course be estimated by the importance of the works. The second objection is to be met by observing that the rich limes require to be for a long time exposed to the air to en- able them to take up the carbonic acid gas; and that, therefore, so far from losing, they gain by exposure; and, moreover, the hydraulic limes being very difficult to slack, it is necessary that all their particles should be put in contact with the water. If the lime be not pre- viously reduced into the state of a perfect hydrate, it is always exposed to blister, and to disintegrate, in a man- ner depending upon the comminution of its particles before being employed: for it is evident that if the lime be ground, the more inactive particles are in a more favourable condition for the absorption of the water. The degree of consistence of this paste should vary with the nature of the extraneous materials. It should be stiff whenever it is intended to form a gauge for sub- stances whose particles are hard and palpable, and which are capable of preserving sensible distances from one another. It should be more liquid when the sub- stances to be mixed with it are pulverulent, of impal- pable and fine grains, presenting an homogeneous appearance, and in which it is impossible to distinguish the separate elements, such as the puzzolanos, &c. To secure a proper state of the hydrate, it is of very great importance, however, not to use too much water in 68 ON LIMES^ CALCARfiOtrS CEMENTS^ slacking the lime. So much should be used, and only so much, as is necessary to cause the quick lime to fall to powder. It is also equally important not to mix up into the state of paste more lime than is imme- mediately required to be used ; for although, upon being reworked, the hydrates, which had began to solidify, give off the water they had rendered latent as it were, yet a portion of their force must evidently be lost by their doing so in proportion to the degree of advance- ment of the process. In France, whenever great care is required in the fabrication of the mortars, the lime is worked up into a paste in a mill, consisting of two vertical stones working in a trough. The lime, after going through this operation, is then mingled with the sand in a pug- mill, or by hand, upon a floor. If the dimensions of the construction should be such as to justify the ex- pense, it should be made a necessary condition that mechanical means be employed, for even with the greatest possible care the mixture by hand is never perfectly efl'ected. The quantities of sand to be used vary, as might be expected, according to the nature of the limes, and also of the sand itself. Within certain limits, if the limes do not gain by the mixture, at least their effect is not sensibly diminished. Thus we find that, for the rich limes, the resistance is rather increased if the sand be in the proportions varying from 50 to 240 per cent, of the paste measured in bulk in the state of a firm paste. Beyond that point the resistance de- creases. The resistance of hydraulic limes increases, if the ^and be mixed in the proportion of 50 to 180 per cent; MORTARS^ STUCCOS, AND CONCRETES. G9 of the paste; from thence it decreases. The much greater proportion of sand the rich limes are able to support^ may perhaps account for the partiality of the builders in their favour. If it be required to mix common lime and puzzo- lanos, the best proportions^ according to General Treussart^ are 1 of lime in powder to 2^- of puzzolano ; 1 of lime to 2 of trass ; or 1 of lime to 1 of sand^ and 1 of puzzolano or trass. The best hydraulic limes^ as we have seen^ lose much of their qualities if long exposed to the air ; it is there- fore advisable to work them only for the time absolutely necessary to ensure, firstly, their perfect reduction to the state of hydrates ; and, secondly, the intimate mix- ture of the lime and sand. The rich limes, however, as we have before said, inasmuch as they absorb the carbonic acid gas with difficulty, gain by being exposed for a longer period to the contact of the atmosphere. As far as such a proceeding is consistent with economy, it is advisable, then, to protract the operation of their manipulation as much as possible ; it is even advisable to work up large quantities of such mortar beforehand, rendering it fit for use by a second manipulation. Some of Vicat^s experiments show that all limes lose two-fifths of their strength if mixed with too much water. It is then better to wet the materials to be used, and to employ a stiff mortar, than to follow the course usually adopted by masons and bricklayers of using very soft fluid mortar. The system of grouting is more than questionable in its results; the lime sus- pended in it is nearly destroyed, the extra quantity of water is but an addition to the difficulties of setting opposed to the mortar already in place. 70 ON LIMES^ CALCAREOUS CEMENTS^ There are conditions of the atmospheric state which affect the goodness of the mortars^ about whose action the best authorities are not decided. For instance^ those made in summer are always worse than those made in winter. It has been supposed by some that this fact IS accounted for by the too rapid desiccation of the mortar; and Vicat even asserts that they lose four- fifths of their strength if allowed to dry very rapidly. He recommends, in consequence^, that the masonry be watered during the summer months, in all construc- tions of importance, to guard against this danger. Probably the hydrates are not in a favourable condi- tion to absorb the carbonic acid gas, if they be allowed to dry rapidly; the presence of the water being neces- sary for the combination of the lime and the carbon. The freedom of the water from carbonic acid gas in solution is also a necessary condition of the successful use of the hydraulic limes. Their success depends, to a certain extent, upon the slow, gradual manner in which they take up that gas from the atmosphere, and crystallize about the nuclei offered to their action. Some engineers prescribe that the water should be deprived of such impurities by boiling, and although the precaution be rather exaggerated, it is certainly of a useful tendency. As the lime reduced into a paste does but fill up the voids of the materials it is mixed with, there is neces- sarily a very considerable diminution of bulk upon the quantities of the respective substances taken sepa- rately. The exact amount of this diminution varies, of course, with the limes or sand employed ; but as a general rule it may be taken at about three-fourths of their collective volumes. To state this in a convenient MORTARS, STUCCOS, AND CONCRETES. 71 formula; if a = the bulk of the lime, 6 = the bulk of the sand; then {a+b) x 0*75 = the bulk of the mortar they will produce. The position in which a mortar of any description is to be used, also modifies the proportions of sand which it is desirable to mix with it. Underground, in the water, and in damp positions, less sand should be employed than in the open air, where it is exposed to the changes of the atmosphere. It is often a matter of importance to know the powers of resistance of mortars ; but, as they diflfer within a very large range, it is not easy to state them very pre- cisely. The best experiments, however, show that we may safely calculate, for all practical purposes, upon a resistance of 14 lbs. avoirdupois per inch superficial, to a force acting in a direction to tear asunder by an effort of longitudinal traction; of 42lt)s. to a crushing force; and of 5^tbs. per inch superficial to a force tending to make the particles slide upon one another. It would not be safe to expose new works to greater efforts than those which could be included within the above limits. CHAPTER IX. ON CONCRETES. The term " concrete^^ is usually applied to a species of rough masonry of small materials, consisting of gravel or broken stone mixed with a lime, either pre- viously worked into a mortar or not, as the nature of the lime may require. It is principally used for the purpose of distributing the v/eight of a large heavy 72 ON LIMES, CALCAREOUS CEMENTS, construction over the greatest surface possible ; or for the backing of coursed masonry, in cases where walls are required of great thickness. Properly speaking, it would be better to apply the word concrete to this sort of masonry, when executed in the manner usually adopted in our country, by slacking the lime upon and in immediate contact with the gravel. When the lime has been previously worked into a paste, the French word " beton might be applied, for the sake of dis- tinguishing the two processes. The use of this beton, or concrete, is very ancient, for it is known to have been employed by the Romans ; and Smeaton expressly states that he derived the idea of using it, as a backing for river works, from an in- spection of the ruins of Corfe Castle, in Dorsetshire. In the middle ages it was very commonly used, as may be proved by an inspection of the ruins of feudal forti- fications. General Pasley was, therefore, mistaken in awarding the merit of the introduction of this system to Sir Robert Smirke. Of course, the quality of a concrete must depend upon the nature of the materials to be employed. The situations in which it is to be used are mostly those in which there is a great amount of humidity, and in which from the facts that, firstly, the concrete is in large masses; and secondly, that it is covered up as soon as executed, it is necessary to employ only such materials as are susceptible of a rapid setting and continued pro- gression in their powers of resistance. In the former parts of this treatise, we have seen that the limes which unite the above conditions are the hydraulic limes, obtained either from the argillaceous, or the magnesio- argillaceous, carbonates of limes. In their absence, MORTARS, STUCCOS, AND CONCRETES. 73 some ingredients of the nature of the puzzolanos, burnt clay, slag^ or cinders must be used. But it should always be borne in mind^ that these mixtures arc but very imperfect imitations of the natural produc- tions ; they should never be used if the hydraulic limes can be obtained, even at an increased price ; and, as was before said of the hydraulic limes, those obtained from the calcination of the limestone itself are prefer- a1)le to those made artificially. In almost every work upon the art of construction, we meet with descriptions of modes of making concrete. It is, however, very discouraging to observe that, in spite of all that may be said, the majority of architects and engineers treat the subject with such utter indif- ference that the old imperfect systems are still retained, and the conduct of these works is left almost invariably to some rule-of-thumb workman, who only knows that he has been accustomed to make concrete in a certain manner, without knowing any one of the principles which regulate the action of the materials he works with. We thus find that the greater part of the con- crete made in and near London, where the building art ought to be the most advanced, is made simply by turning over the ground stone lime — a very moderately hydraulic one, by the way — amongst the gravel. It is then put into barrows, and shot down from a stage. Such a mode of proceeding is rapid and economical ; but it is eminently unscientific, leading, doubtlessly, to the waste of material we so often witness, for the prac- tice is to make the concrete about one-third thicker than would be at all necessary if the process of making it were more perfect. Unfortunately, in England, we do everything in such a desperate hurry, especially 74 ON LIMES, CALCAREOUS CEMENTS, since railroads have been constructed, that we cannot afford the time necessary for a perfect execution of the works. Failures are consequently frequent, the waste of materials enormous; and, of course, between the two, the expense is out of all proportion to what it ought to be. It cannot be too often repeated that the first condi- tion necessary to obtain a good concrete, or beton, is that the lime be brought to the state of a perfect hy- drate before being mixed with the nuclsei which it is intended to surround. It should, therefore, be reduced to the state of a thick paste, and made into a mortar before it is mingled with the gravel. Instead of being thrown down from a height, and left to arrange itself as it best may, it should be wheeled in on a level, and beaten with a rammer ; for we find that, when thrown thus from a height, the materials separate, and the bot- tom parts of a thick bed of concrete are without their proper proportion of lime. The advantage of making the lime into a mortar previously is, that it fills in a much more perfect manner the intervals of the gravel or stones ; and, in fact, renders the concrete what it is meant to be, an imperfect species of rubble masonry. For water-works required to set rapidly, an excellent concrete may be made by a mixture of hydraulic limes, puzzolanos, and sand. The proportions found to yield the best results are given by Treussart, as follows : viz., 30 parts of hydraulic lime, very energetic, measured in bulk, and before being slacked. 30 „ of trass of Andernach. 30 ,, of sand. 20 „ of gravel. 40 „ of broken stone, a hard limesion^h MORTARS^ STUCCOS^ AND CONCRETES. 7^ The above proportions diminished one-fifth in volume after manipulation : the mortar was made first, the stones and gravel added thereto. When the puzzolano of Italy is used, the proportions, for the same descrip- tion of work, become (measured in bulk, as before) — 33 parts of energetic hydraulic lime, measured before slacking. 45 „ of puzzolano. 22 ,, of sand. 60 ,, of broken stone and gravel. The first of these concretes should be employed im- mediately it is made ; the second requires to be ex- posed about twelve hours before it is put in place. When burnt clay or pounded bricks are used, the proportions should be the same as with the trass ; but, as we have seen before, the use of this material is not to be recommended in the sea water. If rich limes be used instead of hydraulic, the dose of the natural or artificial puzzolanos must be increased, and that of the stone and gravel diminished. In positions where sufficient time can be allowed for a concrete or beton to set, (if made simply of lime, sand, and gravel,) the expense of the puzzolanos should be avoided. A very excellent concrete for either sea or river works is made by a mixture of a mortar made of three parts of fine sand to one of hydraulic lime un- slacked, with equal quantities of gravel or broken stone: the proportions of the last may often be augmented to 14- to 1 of the mortar without inconvenience. No water should be mixed with the mortar and gravel dur- ing their manipulation; the mortar itself, if possible, should be prepared in a pug-mill, and mixed with the gravel by being frequentlv turned over on a platform. 76 ON LIMES, CALCAREOUS CEMENTS, Every precaution should be taken to prevent the dif- ferent ingredients from being mingled with clay or other earths. The concrete thus made should be spread in layers from 10 in. to 1 ft. in thickness, and well rammed, until the mortar begins to flush up at the top. A course once commenced should never be allowed to be interrupted until completed throughout the whole of its length. When the work is executed in water, other precautions require to be taken, not only for the pur- pose of compressing the concrete, but also to prevent the lime from being washed away. These must, of course, vary with the circumstances of each particular case; but we must always remember that works of this kind, executed under water, are far inferior to those executed in the open air. When works are left to the care of mere workmen, as they too often are with ourselves, a very absurd mode of making concrete is often adopted where there is much water to be contended with. The lime is mixed with the gravel, without being previously slacked, and left to absorb the water necessary for its passing to a hydrate how it may. Such a course is unphiloso- phical and dangerous in the highest degree, and cannot too carefully be guarded against. In fact, the object to be attained, of securing a carbonate of lime by the equal and regular action of the hydrate, is thereby ren- dered impossible. It is much more than probable that many of the particles of lime can in these cases only obtain the water necessary for their solidification by absorption from the others around them. They must begin their action after the others have ceased; and as the process of crystallization in all cases requires a new MOHtARS^ STUCdOS^ AND CONCRETES* 77 molecular arrangement, often accompanied by an ex- pansion, there is little reason to doubt that if the lime be in large quantities, it must disintegrate the mass. Vicat executed the beton for the bridge of Souillac on the Dordogne in the following proportions in volume: — 26 parts of hydraulic lime in paste. 39 of granitic sand. 66 „ of gravel. This mixture diminished in volume in the proportion of 1*31 to I'OO. But the diminution in volume differs of course with the limes, or the sands used in the dif- ferent localities. Broken limestone appears to add very much to the qualities of concretes, betons, and mortars. Very pro- bably this may be attributed to the affinity between the molecules of the already formed carbonate of lime, and that which is in process of formation ; the new crystals may group themselves more easily about bodies whose form is similar to the one they are themselves to as- sume. Or possibly there may be a tendency in the chemical elements to arrive at a state of equilibrium ; and the carbonate of lime may, therefore, be supposed to part with a certain portion of its carbonic acid gas. Many attempts have been made to produce with con- crete a species of artificial blocks — amongst others, by Mr. Ranger. These do not appear to have answered in practice; but we may safely assert that, if the mor- tars had been properly mixed in the first place, and if the concrete, when in the mould, had been properly rammed, and then allowed to dry very gradually, there is no reason why the attempts to make artificial stone should fail. One great cause of failure of this kind of artificial stone always has been, that the blocks are 7H ON LIMES^ CALCAREOUS CEMENTS^ exposed too soon after fabrication. They dry rapidly, unevenly, and consequently crack in every possible direction, and thus offer great facilities for the action of the frost upon any water they may contain. The resistance of beton or concrete should never be regarded as being superior to those already given for limes^ if the superstructure be commenced upon them immediately. In both cases the resistances are found to increase with comparative rapidity during the first six or seven months. It would be advisable, therefore, to leave concretes undisturbed during that space of time if it were possible. At Cherbourg Breakwater and at Dover Pier, Port- land cement has latterly been largely and successfully used for the purpose of making immense artificial blocks. At Cherbourg the blocks are constructed upon the sheltered side of the Breakwater, with coursed rubble stone bedded in a mortar of granitic sand and Portland cement, and they are subsequently floated upon rafts over the positions where they are to be im- merged. At Dover the cement was used to make a species of concrete, which was poured into a mould and allowed to harden before being placed in the body of the masonry in the ordinary way. (See Appendix D, page 126.) CHAPTER X. ON CEMENTS. A PECULIAR class of the argillaceous limestones yields on calcination a species of lime capable of setting under water with considerable rapidity, of acquiring a great degree of hardness within a very short space of time^ MORTARS, STUCCOS, AND CONCRETES. and of being employed without the admixture of any foreign substance. The name of " cements has been (somewhat absurdly) conferred in an especial manner upon this class of materials, although, properly speak- ing, the word is generic, and should include all sub- stances capable of cementing together small materials. The first discoverer of this kind of cement was Mr. Parker, of London, who in the year 1796 took out a patent for the manufacture of what he called Roman cement, from the septaria nodules of the London clay formation, found in the Island of Sheppy. His process consisted in calcining the stone, previously broken into small fragments, to a point equal to the commencement of vitrification, and then reducing it to powder by some mechanical operation. Parker appears to have thought that a very high degree of heat was necessary to the success of the operation ; but we shall have occasion to observe hereafter that the point of calcination has not the same influence on these cements which it has upon the ordinary limes. Subsequently Mr. Frost discovered that the sep- taria of Harwich, on the coast of Essex, produced a cement of the same nature. Mr. Atkinson introduced another made from the nodules of the argillaceous lime- stones of the secondary formations of Yorkshire. On the coast of France a similar material was found in 1802, at Boulogne. M. Lacordaire discovered it also at Pouilly, in the ancient province of Burgundy; MM. Lame and Clayperon found it in Russia. It occurs in the Isle of Wight, in the Bay of Weymouth, and doubt- lessly is to be met with in all the marl beds intercalated between the principal stages of the limestone forma- tions, and very frequently in the tertiary clays, in the 60 ON LlMJlSS^ CALCAREOUS CEMENTS^ form of detached nodules, of a dark-coloured argillace* ous limestone traversed by veins filled with calcareous spar. The colour is sometimes blue, especially when the nodules are obtained from the lias; sometimes brown, or a deep red, in the tertiary formations, owing to the presence of the oxide of iron in very consider- able quantities. The mineralogical composition of the stones from which the cement is made differs very much ; but the characteristic type may be said to consist of above 30 and below 60 per cent, of clay and other extraneous matter in combination with the carbonate of lirhe. The Sheppy stone usually contains 55 parts of lime, 38 of clay, and 7 of iron ; the Yorkshire stone contains 34 parts of clay, 62 of carbonate of lime, and 4 per cent, of iron ; the Harwich stone contains 47 parts of clay, 49 of carbonate of lime, and 3 of oxide of iron. But the most careful analyses made by Berthier are as fol- lows. The stones experimented upon were — column 1, the Shepi)y stone ; column 2, the septaria of the coast near Boulogne ; column 3^ a stone from Matala in Sweden ; column 4, a stone from the neighbourhood of Argenteuil, near Paris. Carbonate of lime . . 0-690 0-639 0-661 0-651 0-002 0-019 Oxide of iron .... 0-037 0 075 0-022 0 060 „ manganese . . 0-012 0-070 0-180 0-150 ] 0-140 0-066 0-048 [ 0-295 0-060 0-013 0-066 J 0-060 1-000 0-978 0-978 1-060 Waste or error . 0 022 0 022 0-060 deduct. Total .... 1-000 1-000 1-000 1-000 1 J MORTARS^ STUCCOS, AND CONCRETES. 81 The cement stones are burnt in conical kilns with ranning fires^ and, in England at least, with coke or coal. The mode of burning requires a considerable degree of attention, for experience has demonstrated that Parker was mistaken in supposing that a com- mencement of vitrification was necessary. On the con- trary, the practice of manufacturers at the present day is rather to under-burn the cement, with the object of economizing the expense of grinding. This material differs in this respect also from the ordinary limes, that the precise point of calcination does not appear to affect its qualities. Before being burnt, the stone is of a fine close grain, of a peculiar pasty appearance ; the surfaces of fracture are rather greasy to the touch, and somewhat warmer than the surface of the stone. Examined with the microscope it exhibits many sparkling points, which may be either crystals of carbonate of lime, or of some of the other constituents. It sticks easily to the tongue ; it does not strike fire ; its dust, when scraped with the point of a knife, is a greyish white for the most part, especially when derived from the blue lias formation. It effervesces with nitrous acid, and gives off nitrous acid gas. During calcination the cement stone loses about one-third of its weight, and the colour becomes of a brown tinge, differing with the stones from which the cement is obtained. When burnt it becomes soft to the touch, and leaves upon the fingers a very fine dust; and it sticks very decidedly to the tongue. When withdrawn from the kiln in blocks, the cement absorbs water with so much difficulty that General Pasley was almost justified in stating that it could not do so. As he remarks, ^' it miglit be preserved in this 82 ON LIMES, CALCAREOUS CEMENTS, state for a long time in a dry room ; but calcined cement being of no use until it is pulverized, this is always done at the mill of the manufacturer, to save the necessity of every purchaser providing himself with an apparatus for grinding it." It is usually put into casks well closed when thus ground, and may in that state be preserved for a very long time ; but contact with the atmosphere rapidly deteriorates its quality. The cement powder absorbs humidity and carbonic acid gas from the atmosphere ; it then passes gra- dually into the state of a subcarbonate ; but a second burning, carried to a lower degree than that employed for the first calcination, restores its useful properties. It is to be observed, and the fact is of sufficient im- portance to warrant repetition, that though all cements and limes tend to reassume a state of carbonization similar to that in which they existed in the stones from whence they were extracted, they only do so to a very imperfect degree. The proverb that lime at a hun- dred years is but a child, is perfectly true. Cements, on the contrary, harden very rapidly ; but we have no instances of their acquiring the strength of the original stone. M. Petot mentions that, in his experiments upon the calcination of the cement stones, he found that when it had been carried to the point of driving off all the car- bonic acid gas, the powder it gave was perfectly inert. This should be borne in mind in making any new expe- riments on this class of limestones ; and at any rate it constitutes a very remarkable difference between it and those which produce the common lime. The same dis- tinguished engineer also found that cement mortar was capable of being revived after the lapse of a consider- MORTARS^ STUCCOS^ AND CONCRETES. 83 able time. We may remark^ in passings that his researches form the best text-book upon the subject of the calcination both of limes and cements. There does not appear to be any definite rule in the London trade respecting the size of the casks^ or the na- ture of the means by which the cement is transported. This is of little importance as long as it is intended to use it in the immediate neighbourhood of the source of sup- ply. When, however^ the cement has to be transported to a great distance, it should never be packed in barrels of more than 6 cwt. each, and the greatest precautions should be adopted to prevent the contact of the atmo- sphere in any manner whatever. The specific gravity of the natural stone is usuall^r about 2*16 ; that of the calcined stone in block is about 1*58 ; that of the powder, very loosely packed, is about 0*85 to rOO. The best cement is, however, that which is the lightest, and it should be ground very fine. The size of the sieve required to be used by the French en- gineers is No. 2 of their wire gauge, and 185 meshes to the square of 4 inches of a side ; which seems a very reasonable dimension. The use of these natural cements requires a great degree of skill and attention on the part of the work- man. If it be not brought to a proper consistence — if too much or too little water be used — if it be not imme- diately employed as soon as made — it solidifies une-. qually, cracks, and adheres badly to the materials The care requisite for its successful application con- stitutes, in fact, the great objection to the use of cement. It is always dangerous to be obliged to rely on the skill or integrity of workmen, who either do not understand the necessity of taking pains with their 84 ON LIMES, CALCAREOUS CEMENTS, work, or who, from being paid by the piece, have an interest in slurring it over. A small quantity of water only is necessary to work up cements to their greatest point of resistance, which General Treussart found to be the most successfully attained when the water was employed in the propor- tion of one-third of the cement in volume. It is necessary to beat up the cement very frequently ; in- deed, the more it is turned over before the setting com- mences, the harder it becomes. No more should be prepared than can be immediately employed, for with- out this precaution it will set in a very short time. The time of setting varies with the nature of the water used, and the quantity of sand present. With sea-water the time is longer than with fresh, and the sand retards the process of setting considerably. When the cement is new, however, the time of set- ting, if it be used pure, should never exceed half an hour, a quarter of an hour being the normal period. It often happens, however, that the best cement vill harden in an interval not exceeding five or six minutes; under water the interval becomes one hour at most. When mixed with sand in proportions varying from ^ to 1, 1^, and 2, to 1 of cement, the time of setting becomes from 1 h. 2 min. to 1 h. 18 min. in the air; under water the time becomes proportionally longer. It may even, under sea-water, and if the mixture be also made therewith, extend, for the mixtures with large proportions of sand, to 24 hours. Pure cement has much greater powers of resistance than when it is mixed with sand in any proportion whatever—in this again differing from the limes. The resistance to rupture after ^bout 20 days' exposure to MORTARS, STUCCOS, AND CONCRETES. 85 the air, is about 54 lbs. per inch square when the cement is used pure ; if the sand be in the proportion of 4- to 1 of cement, the same resistance falls to 371bs. ; if it be in equal proportions, it falls to 27 lbs. Doubt- lessly, these resistances are less than we often meet with, but it is not safe in practice to count upon a greater strength than they indicate. Rondelet's rule, that the resistance to crushing is three times that offered to traction, does not seem to be quite correct in this case^ for it would make the resistance of pure cement only equal to 162lbs. per inch superficial; but, again, it would not be safe to take a higher degree of strength as the basis of any series of calculations for practical purposes. Moreover, the permanent load in any large works should never be more than one-sixth of that required to produce rupture ; and, if small materials be employed, the resistance should be calculated at only one-fifteenth of that indicated by theoretical conclusions of the above nature. Cement adheres very strongly to iron, to granite, and to bilcks, in a proportion following an inverse direction to the manner in which they have been just named. When re-burnt, after having lost its strength by expo- sure to the air, the resistance is not more than one- fourth of that of the fresh cement from the stone. The resistance to an effort tending to make stones slide upon their beds when joined by pure cement, may be considered equal to 9lbs. per square inch upon the average; but it often arrives at 181bs. per inch. From these considerations, it would appear that the best mode of using the natural cements is to employ them without sand in all works under water, or where a great crushing M^eight is to be brought upon them at 86 ON LIMES, CALCAREOUS CEMENTS, once. For foundations in damp situations^ where rapidity of execution is desired, they may be mixed with 2 parts of sand to 3 of cement; the same proportions are suitable for cornices, or coatings ex- posed to the weather. 3 parts of sand to 2 of cement make a good mixture for perpendicular faces ; but care must be taken that the cement be used so as not to allow of the formation of fissures, or the frost will destroy it. Many of the failures of the coatings executed upon brickwork are to be attributed to the neglect of pro- per precautions against the action of the atmosphere. It is important that the brickwork to be covered be thoroughly dry before the coating is added, or the expansion of the water it contains will blow off the latter. The cheap and disgraceful system of colour- ing, instead of painting, also leads to many failures in the employment of this very useful class of materials. In England, owing to the cheapness of the so-called Roman cement, whether specifically distinguished as Atkinson^s, the Medina, or merely called Roman, almost all the works executed in water at the present day are executed with it. But there are reasons to make us doubt whether we do not in this case adopt a system which is at least open to objection. Cement is so con- venient, that engineers and architects neglect to study the qualities of lime; and some very unfortunate acci- dents have arisen from that neglect. For instance; the author has seen, in one of the government dockyards, the whole of the backing of a graving dock executed in cement, v/hen there were large works in the immediate vicinity for the manufacture of the blue lias lime — a most shameful waste of the money of the nation. All the MORTARS, STUCCOS, AND CONCRETES. 8? profession may recollect a sad accident, which cost the lives of several men, and which arose from building columns in cement on bases in mortar. With respect to these cases we may observe that Roman cement is a most admirable material where great rapidity of setting is required; but it should only be used under such cir- cumstances, for good hydraulic limes in time attain a degree of resistance sufficiently great for all practical purposes, and at a much less expense. To use a hard, quick-setting material upon a yielding base, is a degree of ignorance totally unaccountable on the part of any professional man of average discernment. In fine, the uses of these cements are many and various; we, in our country, are rather inclined to abuse them. There are many sorts of artificial cement employed which are obtained either from the over-calcination of the hydraulic limes (all of them possessing the faculty of acquiring a more rapid setting, and a greater degree of hardness when so burnt), such as the Portland cement before mentioned ; or from the mixture of burnt clays with the rich limes. In some parts of the conti- nent, where the natural cement stones do not exist, the latter are much used, and they yield a very tolerable substitute for the articles they replace. They are not exposed to the inconvenience which attends the over- calcined limes, of swelling in setting; but they are far from attaining the hardness of either the natural ce- ments or the overburnt artificial ones. Their use is principally confined to a mixture with the slow-setting limes when they are employed in damp situations, and in these cases they succeed remarkably welL The cess- pools and water tanks throughout the interior of Nor- mandy are lined with a mortar made in this manner, 88 ON LIMES, CALCAREOUS CEMENTS, and they resist perfectly; but this description of ce- ment is never used if the natural cements can be ob- tained at a reasonable price. It is to be observed, that although the Portland cement is occasionally exposed to the before-mentioned inconvenience of expanding whilst setting, it has other qualities of a very remarkable nature. It becomes, in equal times, after the first setting (which, by the way, is very irregular), much harder than the Roman cements. It will admit of a much larger quantity of sand for every purpose I and, moreover, as it does not absorb the hu- midity of the atmosphere with the same facility it con- sequently resists the action of frost more successfully, and is less exposed to discoloration by the formation of vegetation. In some parts of France, especially in the ancient Lorraine, limestone beds are worked which yield a species of lime intermediate between the Roman ce- ments and the eminently hydraulic limes. The best of these occur at Flavigny, and Richard Menil, near Nancy, where they are principally used for making floors of one piece, and of a smooth uniform surface. The colour of the stone is of a darkish brown, of a great tenacity, and very compact; its specific gravity is 2*62. The lime it produces is of a yellowish grey, and it sets very rapidly in water. Mixed v/ith the clean gravel of the Moselle, in the proportions of 4-^ to 1 of cement, the volume of the mixture diminishes one-fourth; it is tlien spread upon the form prepared to receive it, and w^ell beaten. There must be many beds of such lime- stone in our own country^ as in the neighbourhood of Rugby^ Bath^ Aberdare^ &c. ; and^ if they were properly sought for, they might add materially to our facilities for building. We require a carefu) geological survey MOHTARSj STUCCOS^ AND CONCRETES. 89 of England to ascertain the riches we possess of this nature. A commencement was made by the parlia- mentary commission for the choice of the building stones for the Houses of Parliament; but it did not extend its inquiries to the other branches of this very important part of practical science. CHAPTER XL ON THE VARIOUS CEMENTS COMPOSED OF NUMEROUS EXTRANEOUS INGREDIENTS. There exists also an infinite number of processes for making cements able to harden under water^ and to acquire a great degree of resistance. Their success is of course very various ; nor can it well be otherwise, for as all these mixtures depend for their success upon the care and skill observed in their manipulation^ they must be exposed to all the accidents which attend the processes of human industry. The following are some of the artificial cements alluded to ; but the list might be extended indefinitely without including all the varieties. They may be separated into two grand divisions^ the bituminous and the oleaginous. Both of the classes are of constant use in the arts of building ; and they furnish materials of very great importance, either for the coating of works for ornamental purposes, or for protecting them against the action of water. The bituminous cements are used either for the pur- pose of supplying the absence of large flagging for Btreet paving, or for covering the extrados of arches, 90 ox LIMES, CALCAREOUS CEMENTS, in order to prevent the percolation of water from the upper structure. In many situations they are very successful, when employed for street paving; but, gene- rally speaking, we in England have no occasion for such substitutes for stone. Such is not the case in France, however ; and it might be economical to use these cements in some of our own inland towns, where the cost of land carriage renders the stone flagging very expensive. For covering arches, these cements are, moreover, very much to be recommended. In all new masonry, with whatever care executed, there are always movements which fissure the coatings executed in limes or natural cements. These again are subject to unequal shrinkage and contractions, which produce crevices; and, from these united causes, it is very rare to find that such coatings are impermeable. The bituminous cements are more elastic; it often happens in their case that small crevices solder themselves, so to speak ; and, if any serious repairs are required to be done, it is much easier to execute them than it is when the works are executed with limes. The best bituminous cements are obtained from the natural asphalt, which is met w4th in large quantities on the shores of the Dead Sea; in Albania; in Trini- dad; at Lobsann and Bekelbronn, in the department of the Bas Rhin ;^^ in the department of the Puy de Dome; near Seyssel, in the department of the ^^Ain;^^ at Gaugeac, in that of the Landes ; and would, in all probability, be found near Castleton, in Derbyshire, if carefully sought for. There are two sorts used in commerce, the pure and the impure. The first does not contain extraneous matter in any great degree; the second contains a MORTARS^ STUCCOS, AND CONCRETES. 91 variable proportion of carbonate of lime, and is, there- fore, better adapted to such works as are exposed to the effects of the sun. The purer asphalt melts in such positions, but it is better adapted for subterranean works. The best bitumen, or asphalt, for the words are very illogically confounded in commerce, is free from water. Its specific gravity is 1*10 to 1'15 at the ordinary tem- perature; it is solid, but highly ductile, for it drawls easily into threads ; its fracture is black, slightly bril- liant. Put into warm water, it should float upon the surface, and in that operation it should not deposit any sand. It dissolves completely in the oil of petroleum and the essence of turpentine; and the dissolution, w^hicli should be of a bistre or dark-brown colour, after being filtered, should not be found to have contained more than seven per cent, of earthy matters. In com- merce, much fraud takes place by mixing coal tar and pitch; but these materials, though very valuable by themselves, destroy the superior qualities of the mineral asphalts. It is also highly important to secure the purity of the asphalt from sulphur, or the sulphates of iron. Even so small a proportion as 0*5 (or ^) per cent, would materially diminish its value. When the asphalt is to be used, the solid bitumin- ous stone is thrown into a quantity of mineral pitch, in a state of ebullition ; for if it were put into the caldron alone, it would calcine without melting. If any sand or earthy impurities be present, they should be removed at this stage of the process. The calcareous matters are mixed with the melting bitumen in proportions varying with its nature; and the mixture is applied by means of large spatules, or trowels. Colonel Emy found 92 ON LIMES, CALCARfiOUS CEMENTS, the following proportions to be the best for the asphalt of Gaugeac, and they may be taken with tolerable safety, as being the most suitable for all the members of this class of cements, when used as a coating for arches, pints (wine measure) of pure mineral pitch. 11 lbs. avoirdupois of Gaugeac bitumen. 17 pints of powdered stone dust, wood ashes, or minion. It is advisable to lay this cement upon a bed of con- crete, or mortar ; and as much as possible in slabs of 2 ft. 6 in. to 3 ft. in width. It should be evenly spread and compressed by a trowel, well rubbed and reduced to a uniform close surface. When all the bubbles have been expelled, a fine sand is sprinkled over the surface, and worked in with the trowel, observing never to fill the crevices formed by the air-bubbles with sand, but only with asphalt. The thickness necessary for coating any arches is not more than from three-fifths to half an inch 3 the quantity of the cement thus employed to cover a yard square is about 4^ lbs. For street paving, it is absolutely necessary to em- ploy under the asphalt a bed of concrete of hydraulic lime and gravel; the upper surface being rendered smooth by a coating of hydraulic mortar. The thick- ness of the asphalt should be increased to three-fifths of an inch ; and it is advisable to add a small quantity of pure quick lime to the bitumen in ebullition, to pre- vent the asphalt from becoming soft under the influ- ence of the sun^s heat. The surface upon which the asphalt is to be employed should be perfectly dry; and it should be applied as hot as possible. All the natural asphalts are not of the same quality in so far as their MORTARS^ STUCCOS, AND CONCRETES. 93 elasticity is concerned. If, therefore, any of them are found to be too brittle, that defect should be remedied by mixing a quantity of the mineral pitch or petro- leum ; but on no account by the mixture of coal tar or vegetable pitch. The coal tars, or vegetable pitch, although they be not so desirable as the natural bitumens for building purposes, may in many cases become very valuable substitutes for them. They are not so supple, the stone powder to be mingled with them requires to be pre- pared with greater care ; and it would appear that they are not so durable as the natural productions of a cor- responding class. But they make very good coatings for vaults, or for walls exposed to the dampness of the earth; and many situations occur in which their use must be more economical than that of the materials they are to replace. For foot pavings, however, they do not answer at all. The mode of using them is to mix powdered cal- careous stone, in variable proportions, with the pitch or tar in a state of ebullition. Care must be taken that the stone be thoroughly dry; for if it were wet, it would render the cement porous, from the effect of the vapour trying to escape. The burning, or degree of heat, must also be so regulated that the stone be not converted into quick lime, which takes place with com- parative facility owing to its highly comminuted state. The proportions of powder are from 6 to 7 of the pik^h in volume, but these require to be ascertained by direct experiment in every distinct case. All the other de- tails of the use of these cements are precisely the same as in the case of the natural asphalts, excepting that it is advisable to use them in greater thicknesses. H 94 ON LIMES, CALCAREOUS CEMENTS, The cements used for mosaic works are sometimes of the bituminous character. As applied on the continent, they are of three sorts. The first, which serves to set the large tesserse in forming floors, is composed of pitch mixed with a black earth ; the second, which serves to set stones of middling dimensions, is made of the cal- careous stone of Tivoli, and of oil; it is properly an oleaginous cement; the third, which is used for the more delicate mosaics of pieces of glass, is made of lime, pounded bricks, gum andragan, and the white of eggs. The French plumbers unite the glazed pottery tubes they employ for the distribution of water, with a hot cement made of resin, wax, and lime ; or with a cold cement composed of quick lime, cheese, milk, and the white of eggs. The list of these mixtures is, as we observed before, interminable ; but their use is not of sufficient importance to require a detailed notice. The oleaginous cements were formerly very much used in London under the name of mastic, for the pur- pose of the ornamental decorations of the Quadrant, and of King William Street in the City. They produce a very fine, close-grained, even surface, and if painted in the beginning, and repainted every three or four years, they retain their beauty for a very long period. Their use has, however, very much diminished of late, owing to the expense, and the difficulty of the manipu- lation. Indeed, there are no reasons which should induce us to prefer these materials to the hydraulic cements obtained from the septaria, in face of the great diff'erence in their prices. The best mastics used are known in commerce under the names of Hamelin^s mastic, in England; and the mastic de Dhil, in France. The composition of both MORTARS^ STUCCOS^ AND CONCRETES. 95 is kept secret ; but the main principle of their fabrication consists in the mixture of pounded brickdust^ or well- burnt clay^ or stone, with litharge, the red protoxide of lead, and with perhaps some extraneous matters. As the proprietors of these processes object to their being rendered public^ we content ourselves with calling attention to them, and observing, that they are the best of this class of artificial cements. Many substi- tutes have been invented for them^ which have been more or less successful; the following being amongst the most remarkable. A litharge mastic is made by mingling 93 parts of burnt clay, pulverized^ with 7 parts of litharge ground to a very fine powder. It is mixed up for use with a sufficient quantity of very pure linseed oil, to reduce it to the consistence of plaster in a similar state; it is applied like plaster, after the surface has been previ- ously wetted with a sponge filled with oil. This mastic w^as invented by the Baron Thenard, and it has answered tolerably well. At La Rochelle, the officers of the engineers used, In 1826, a mastic which very closely resembled the mastic de Dhil. It was composed of 14 parts in volume of siliceous sand. 14 parts of pulverized calcareous stone. ■xV in weight of litharge (of the united weights of the sand and stone). J- of the total weight of linseed oil. These powders w^ere previously well dried in an oven, for it was found that the affinity of the mixture for the oil depended upon the state of desiccation of the mat- ters, and upon the commencement of a calcination 96 ON LIMES5 CALCAREOUS CEMENTS, which appeared to be produced. The mastic thus pro« duced was mixed with oil in the usual manner, and tne surfaces upon which it was applied were previously soaked with oil. In Paris the military engineers sometimes use a mastic of nearly a similar composition, which is made of 6 parts in weight of cement, 1 of white lead, 1 of litharge, 3 of linseed oil, and ^ of a richer oil, perhaps an animal oil. At times the cement made from burnt clay is used, at others the natural cement ; it has been found also that in some positions the white lead might be advantage- ously replaced by a similar quantity of puzzolano. Vauban recommended a kind of mastic which appears to have answered very well for the lining of cisterns and such works. He took 5 or 6 parts in volume of rich lime, which had been slacked in linseed oil, and he mixed these with 2 parts of good cement passed through a very fine sieve. The mixture was beaten up for about half a day; it was laid aside for a night, and beaten up again during half an hour on the next day. It was then laid on the work to be covered in coats of from |th to ,ith of an inch at a time, the joints being first well raked out and cleaned. After three or four days, a second, and subsequently a third and a fourth coat were added, the lower one being well scored to form a key to the last one to be applied. This is the simplest, and experience has shown it to be one of the best methods of making mastic; but we may repeat that such compositions are but elaborate modes of supply- ing the places of materials which exist already in the more convenient form of the natural cements. (See Appendix E, page 129.) MORTARS^ STUCCOS^ AND CONCRETES. 9? CHAPTER XII. ON PLASTERING. The modes of rendering the insides of dwellings vary in different countries with the materials most com- rnonly found. Wherever the sulphate of lime occurs in large quantities^ it is the material exclusively employed ; when it becomes too dear, a combination of lime with sundry other materials is substituted for it; or cement, either natural or artificial, is used. The sulphate of lime is met with in large formations known under the commercial name of gypsum. It is to oe found, in England, at Alston, in Cumberland ; at Shot- over Hill, in Oxfordshire ; and a variety of the fibrous gypsum occurs in Derbyshire and in Cheshire. In the neighbourhood of Paris, it is met with at Montmartre, Belleville, Charonne, Menilmontant, le Mont Valerien, Triel, Meulan, and Vaux. It is worked in the depart- ments of the Soane and Loire, of the Rhone, of the Marne, the Seine and Oise, and of the Landes; in the Alps and the Lower Pyrenees; it is also found near Marseilles, Grenoble, Mont Blanc, and Mont Cenis ; in Tuscany, Savoy, Spain, and Switzerland. An anhy- drous variety is worked at Bergamo, and Milan, which comes from the neighbourhood of Vulpino. In Ger- many there are also beds of it largely worked for the purpose of dressing the artificial meadows ; and large quantities are also extracted for the same purpose in the British colonies of North America, which are exported principally to the United States. It may be said geo- logically to occur either in contemporary strata of gre^tfe 98 ON LIMES^ CALCAREOUS CEMENTS, thickness (as near Paris) in the tertiary formations; or in the iridescent marls [les marnes irisees) of La Meuse, or the Aveyron ; or in masses of a subsequent date in ti e different secondary rocks. These last masses are constantly in contact with the igneous rocks, and they are very frequently associated with the dolomites, rock- salt, bitumen, and sulphur in a distinct form. The sulphate of lime is insipid, or of a slightly bitter flavour ; it is colourless and indecomposable by heat. It is soluble in water, whether hot or cold, 1000 parts of water at any temperature between 10^ and 100^ of the centigrade scale dissolving 3 parts of plaster. Its specific gravity is 2*3 1 ; it contains in its natural state 20*9 per cent, of water of crystallization, which is given off at a temperature less than 200° of the centigrade scale (392° Fahrenheit). The gypsum from the best quarries is nearly as hard as the calcareous stones ; after its water of crystalliza- tion is driven off, it becomes pulverulent and like flour. If fresh water be presented to it in this state, it com - bines with the normal quantity of water, and reassumes the form of a hydrate, which it had lost by the burning, crystallizing around- the materials presented to it, and recovering its original density and strength to a very great degree. It is this property which has led to its use in buildings : when the plaster is burnt it is de- hydrated ; when gauged, or worked up, the precise quantity of water it had lost is restored to it. The plaster is ^^got^^ from the quarries (either under- ground or open) by picks and wedges ; sometimes with gunpowder. The greater number of the quarries round Paris are underground; and at Montmartre, nearly the whole hill is thus dug out. The stone is broken up MORTARS, STUCCOS, AND CONCRETES. 99 into small blocks, about the size necessary for rubble masonry, before being carried to the kilns. The burning of the plaster stone at Paris, and throughout the continent, is managed in a very slovenly way. The kilns consist simply of three sides of a square enclosed by brick walls, covered with a rough tiled roof, in which spaces are left to allow the escape of the steam. Under this sort of shed (for that is a more correct name than that of a kiln), the plaster is arranged by constructing, firstly, a series of vaults of the largest stones, filling in the haunches as the arches are carried up. Upon these the remaining stones are piled, paying attention only to the fact that the larger ones should be near the fireplace formed by the vaults. These are subsequently filled with faggots, or other firewood, which is then lighted. The flames rise through the spaces left in the stones; they ascend gradually through the mass, and distribute, as equally as may be, the heat in their passage. The time of burning necessarily depends upon the quantity operated upon at once; but care must be taken that it be not continued so long as to over-cal- cine the particles in immediate contact with the fire. As was before said, a degree of heat equal to 200° of the centigrade scale is sufficient to drive off the water ; if exposed to a greater heat, the sulphate of lime appears to lose its power of combining with the water necessary for the process of reassuming the form of a hydrous sulphate. The system of calcination adopted abroad, as might na- turally be expected, leads to a great waste of raw material, owing to the very slovenly way in which it is executed* As much as one-fifth is wasted in many of the kilns. Some of the London manufacturers adopt a mode of 100 ON LIMES5 CALCAREOUS CEMENTS, preparing the plaster, which obviates not only this in- convenience, but also that attending the use of coal, which discolours the plaster very much. It consists of a kiln so arranged that the fuel is never in immediate contact with the stone ; but the chimney from the fire- place passes round and round the kiln, and communi- cates its heat during the whole of its passage, rendering the interior, in fact, an oven. The plaster in this case is burnt contmuously. A system has also been proposed lately in France which appears theoretically superior even to this pro- cess. It is founded on the fact that steam at a verv great degree of heat becomes a gas, very greedy of water, and able to absorb it from any body it may be put into contact with. A jet of steam, heated above 400^ Fahrenheit, is in this system projected upon the plaster stone, which has been broken very small comparatively ; it takes up immediately all the water present, and leaves the plaster in the state of a pure anhydrous sulphate of lime, without waste or discolora- tion. The difficulty of this process lies in making the chamber in which it is carried on, and all the machinery, sufficiently strong to resist the action of so very elastic a gas as steam at that temperature. But the problem has been solved for the drying of gunpowder by a similar use of very high-pressure steam ; there can, then, be no insuperable difficulty in the case of the plaster. The stone which yields the best description of plaster, without any exception, is that found near Paris. Gene- rally speaking, its superior hardness, and rapidity of setting, are attributed to the presence of a small quantity of carbonate of lime, which is supposed to be converted into a pure lime by calcination. But, as Guy Lussac MORTARS^ STUCCOS, AND CONCRETES. 101 observed^ this cannot be the real explanation^ for the degree of calcination of the plaster is never sufficiently higli to affect the carbonate. The degree of hardness of the plaster must then depend entirely upon that of the stone from whence it is obtained; and we generally find, in fact, that such is the case — the hardest stones produce the hardest plaster. A simple manner of ascertaining the quality of a plaster stone is to put into a vase a certain quantity of it in a state of powder, and to pour thereon one half in volume of nitric acid, diluted in three times its own weight of water. This is allowed to repose, and after several hours, the liquid is to be decanted very gently. The deposit is to be washed with pure water several times, being allowed to rest between each of the opera- tions. As soon as the water is pure and tasteless, the mixture or deposit is to be taken out, spread upon a sheet of paper, and dried. Weighed in this state, the loss it has sustained represents the quantity of carbonate of lime present in the stone submitted to the analysis. After the calcination, the plaster is reduced to powder, either by hand or in a mill; in this state it absorbs the humidity of the atmosphere with great avidity, and re- quires to be covered up very carefully, directly it is !^rushed, to secure it from contact therewith. There is also, from this same reason, a considerable danger in transporting plaster in its manufactured state for any great distance. When mixed with water, a species of confused crys- tallization takes place, and the water in combining with the plaster gives off a considerable portion of its latent heat. An augmentation of volume takes place, which is supposed to be owing to the efforts of the crystals to 102 ON LIMES, CALCAREOUS CEMENTS, arrange themselves symmetrically. Unless great atten- tion be paid to this action of the plaster, it is likely to compromise seriously the solidity of the work. Some- times it is obviated by mingling with the plaster sub- stances which may allow the movement of the crystals to take place, without affecting the colour of the mass. Plaster is far from having permanently the tenacity of mortar, which property in the latter, unlike plaster, as it is well known, increases with time. Rondelet found that if two bricks were joined together by means of this material, they united with one-third more force in the commencement than if they had been joined with lime; but that they subsequently lost their force of adherence. A very useful application of plaster was made by Smea- ton in the construction of the Eddystone Lighthouse, where he covered the fresh cement joints with it, to give them the time necessary to harden. In England, where plaster is both bad and expensive, its use is confined to the more costly descriptions of decoration. In France, however, it is largely used for the construction of walls, both internal and external, as well as for rendering them afterwards. If proper precautions be taken to cover the surfaces exposed to the weather, and if it be painted as soon as dry, the plaster is eminently useful in such positions; and re- places very advantageously the natural cements for all common purposes. But it is utterly incapable of resist- ing the action of water. As the proprietors of the French quarries of gypsum have recently made vigorous efforts to introduce that material into our country, and as from its superior qua- lities it ViWl eventually force itself into general use, if burnt near the place of consumption, some instructions MORTARS, STUCCOS, AND CONCRETES. 103 are added as to the manner of employing it which ia generally adopted in Paris and the environs. The coarser kinds of plaster are used for the ordinary works, such as the rendering of walls and partitions ; the finer qualities are reserved for the ceilings, cornices, and other decorative works. A difference is to be ob- served in the quantity of water to be mixed, according to the position and nature of the work to be executed. Thus, for walls, the plaster must be gauged stiff for the first coats, and more fluid for the setting coat. For cornices worked out in the solid, the core is made of stiffly gauged plaster, which is floated with finer mate- rial, and lastly finished off with plaster laid on by hand about the consistence of cream. Practice only can ascertain the precise degree of stiffness to be given, especially as every burning yields a different quality. When walls are to be rendered in plaster, they require to be first jointed, and then wetted with a broom. The surface is then covered with a coat of thinly gauged stuff laid on wdth a broom, or at least worked with the trowel in such a manner as to leave sufficient hold for the next coat. This is gauged stiff, and is laid on with the trowel ; it is floated with a rule, but the face is finished with a hand trowel. Owing to this, and to the fact that the plaster sets too rapidly to allow of great pains being taken with the floating, the surfaces are never so even, nor are the angles so square and true, as with the common system adopted in England. But this mathematical nicety is not really of importance in ordinary w^orks, whilst the rapidity with which the plaster dries constitutes a real and very important re- commendation in its favour. The partitions in Paris are generally made solid, so 104 ON LIMES^ CALCAREOUS CEMENTS, as to prevent sound from passing through them. Thej are executed with quarters of oak or of fir^ according to the nature of the building. Upon the quarters^ laths are nailed every 4 in. apart^ and the interior is filled in with plaster rubble. This is made even and flush with the laths^ and the whole is then rendered like an ordi- nary wall. The ceilings are sometimes executed with close laths, but the usual plan is to nail them about 3 to 3| in. from centre to centre. A sort of flat centering is put under them, and what are called ^^augets'^ are then formed between in plaster, which finish about flush with the under side of the laths, and return up the joists to nearly their total height, forming a sort of channel, which the workmen often finish by drawing a bottle along the sides. The minimum thickness in this case should be about 1 inch ; the ceiling itself is added un- derneath ; the floors are either of wood, or of tiles upon a bed of plaster formed above the joists. The better description of such floors and ceilings are often made, however, with laths spaced 4^^ from centre to centre ; the space between ceiling and floor is then filled up with light plaster rubble, and the upper and under sur- faces are rendered to receive the ceiling and the tiles. Ceilings executed in either of these two last-named manners, cost 1^ time those executed either with laths or flat ^^augets.^' In countries like our own, and in Belgium and the French Flanders, where the price of plaster is very high, it is replaced by the use of a mixture of lime and sand, to which cows^ or calves' hair is added. This mixture is then applied upon close lathing for ceilings and partitions, and in the usual manner upon walls. MORTARS, STUCCOS, AND CONCRETES. 105 The lime generally used for this purpose is the chalk lime, which is slacked with a great deal of water, and runs from an upper basin in the state of a cream into a lower one, where the excess of water is allowed to evaporate. A grating should be placed at the entry of the passage between the two basins, to keep back the core, or any unslacked particles the upper one might contain. The lime run in this manner is made into a mortar with a very fine sand, and the hair is then added. For the first coats coarse hair will be most desirable ; for the finishing coats it should be finer. In well-finished works two coats are given, which are distinguished by the names of the "rendering" and the " floating." A third coat is then added called the setting coat, which is made of the pure lime as it is run from the basin. Ceilings are afterwards covered with a very light coat of plaster, gauged thin, and laid on with a trowel. Such plastering is very cheap ; and *\f proper attention be paid to its execution so as to avoid blisters from the use of unslacked lime ; to fill the cracks which frequently take place in the thicker coats, from the unequal contraction of the lime in setting; and to allow a proper interval for the whole plastering to dry before the painting, or subsequent decoration to be added, is applied; the lime and hair may be safely admitted as a substitute for the natural plaster. The greater rapidity with which the latter dries, the much superior manner in which it takes colour, and the degree of hardness it attains, will, how- ever, secure it the preference, unless very weighty con- siderations of economy opposes its employment. (See Westmacott's Appendix F, page 105.) One great use of the sulphate of lime dehydrized, or of the common plaster is for the purpose of top-dress- 106 ON LIMES^ CALCAREOUS CEMENTS, sing upon the lucerne, trefoil, sanfoin, and other artifi- cial grasses. This method of using it prevails to a very great extent throughout France and the United States; but it is comparatively unknown in England. Some experiments appear to have been already made, but with the English plaster stone in its unburnt state. They did not succeed; it may be owing to the difference of the two stones, or because, as the raw gypsum was used, in so very wet a climate as ours, its useful action was too rapidly exhausted. It would also appear that the gypsum was used as a manure (for which purpose it is comparatively valueless) instead of being simply employed as a top-dressing. In the north-west of France the farmers use the plaster in equal quantities with the seed sown, or 4 cwt. per acre. It is sprinkled gently over the grass crops, and the best time for em- ploying it is immediately before a shower of rain. This dressing requires to be renewed every year, and conse- quently is rather expensive ; but the results it produces are startling, so great is the difference in the weight of the grass crops. The objection on the score of expense ought now to be obviated ; for with the facilities offered by the French Railway Companies, the plaster stone could be obtained in England at a sufficiently low rate to enable manufacturers to supply the plaster itself at a price which would bring it within the reach of farmers. The London manufacturers appear to have been run- ning a race lately in bringing out new combinations of plaster^ the result of which only appears to be, that they obtain artificially and expensively what would be nearly as well obtained by the use of the French plaster stone* Amongst the best of these inventions is, without excep- tion, the Keene's cement, which is capable of bein^ MORTARS, STUCCOS, AND CONCRETES. 10? worked to a very hard and beautiful surface, so hard, indeed, as to be well adapted for floors or skirtings. It is obtained by soaking the plaster in alum water after a first calcination ; it is then put a second time into the kiln, reburnt, and ground. The Keene^s cement is, in fact, a very beautiful plaster. Why the name of cement should be given is, however, a mystery, unless we explain it on the ground that the manufacturers wish to keep up their charter of applying names without rhyme or reason. The Parian cement is also composed of a plaster base, the gypsum being mixed with borax (the borate of soda) in powder, and the mixture is calcined, and is subsequently ground. The result is a very beautiful material; but it is liable to the same objection as the Keene^s cement, namely, the expense. There are numerous other mixtures of the same nature in which the plaster is mixed with one or more of the salts. They can hardly be yet considered as inventions which have fallen into the domain of publi- city; any detailed description might, therefore, be considered as an interference with the rights of the proprietors. (See Appendix G, page 131.) CHAPTER XIII. ON STUCCOS. The name "stucco^^ is given to a species of j^lastering which is subsequently worked to resemble marble. It is generally made of lime mixed with calcareous powder, chalk, plaster, and different other substances, in such a 108 ON LIMES^ CALCAREOUS CEMENTS, manner as to obtain in a short time a solid surface, which may be coloured, painted, and polished with sufficient perfection to allow of its being used instead of the more precious marbles. It is employed in archi- 'iecture to cover columns, pilasters, walls, plinths; to form mouldings, bas-reliefs, and other analogous objects of decoration. Stucco is also sometimes used to protect exterior surfaces exposed to the air or to humidity; but in this case such materials only should be used as are capable of resisting the action of water. As the mate- rials for making stuccos do not exist everywhere in the same manner, their composition must differ in every locality. The principal object is to obtain a material which is capable of acquiring a great degree of hardness, and which is able to receive a polish. To obtain these results, one of the most important conditions is, that the different ingredients be reduced to the greatest pos- sible degree of fineness, and that they possess the power of rapidly solidifying. There are two species of stuccos: those made of limes, and those made of plaster. Of the former it is evident that the best must be those which are classed under the name of cements; but their disagreeable colour prevents their being used, at least for ornamental decoration. They serve, however, to form the foundations on which the more elegant preparations are applied, whenever any danger is to be feared from humidity. The Italians usually execute their stuccos in three coats ; the first is a very coarse one, and forms merely what we would call the " rendering.^^ The materials of the second are much finer, and they contain a larger pro- portion of time ; the surface being thus brought up to a MORTARS^ STUCCOS, AND CONCRETES. 109 very even, close grain. The last coat of stucco is made of rich lime which has been slacked, and run through a very fine sieve, and is usually allowed to stand from four to five months before being used, in order that every particle of it may be reduced to a hydrate. If the lime cannot be kept for so great a length of time, the slacking may be perfected by beating it up very fre- quently. When great perfection is required, it is usual to mingle pounded white Carrara marble, or even gyp- sum or alabaster ; but the latter are only used in situa- tions which are entirely protected from the action of the atmosphere. The powdered marble and the lime in the form of a very damp paste are mixed, in equal quantities, until the whole is perfectly homogeneous. Vitruvius even recommends that the trituration with a trowel be continued, so long as any portion of the mix- ture adheres to the iron, before it be applied. This preparation is then laid very carefully upon the even surface of the second coat of plaster, and well worked with the trowel until the face becomes perfectly polished. It forms a very good imitation of marble of a uniform colour. The different colours are obtained by mixing with the lime such metallic oxides as the case may require ; thus, to obtain blues, two measures of marble powder, one of lime, and a half measure of the oxide, or even the car- bonate of copper, are mixed together. To obtain greens, a quantity of the green enamel is used with a larger proportion of marble powder ; but the mixture is worked up with lime water. Pearl greys are made by mingling ashes with the marble. Browns, by mingling ashes and cement in proportions varying with the tones desired to be obtained. Blacks are I ^ 10 ON LIMES3 CALCAREOUS CEMENTS^ made by using forge ashes containing numerous par- ticles of iron. Calcined ochres are used to make the reds^ as is also litharge^ or the red oxide of lead ; the yellow oxide of lead serves to give that colour. The mixtures thus obtained are subsequently laid on in patches ; and the excellence of the work consists in the taste with which they arc employed to imitate the effects of the natural marbles^ so as to give either the blending or the distinct opposition of colours to be met with therein. When plaster is used instead of lime, it is gauged with lukewarm water in which size has been dissolved, or fish glue, or gum arable, in order to fill up the pores, to give it more consistence, and to render it sus- ceptible of receiving a better polish. This kind of stucco is the one more especially employed when it is required to produce details of great delicacy and per- fection. If it be required to produce divers tints with this material, the colours should be dissolved in the size water before it is used for gauging the plaster. The polishing should never be commenced until the whole of the stucco is perfectly dry. To hasten the desiccation a linen may be applied frequently to the face to absorb the moisture which may have worked through ; but no friction should be allowed until the whole is perfectly dry. The surface is then rubbed with a very fine-grained grit stone, washing and clean- ing it with a sponge in the same manner as a real marble; it is then rubbed with a linen containing moistened tripoli powder and chalk ; and the whole is finished by a rubber of felt imbibed with oil and very fine tripoli powder, which is quite at the end changed for a rubber containing nothing but oil. The thickness MORTARS^ STUCCOS, AND CONCRETES. Ill of the coat of stucco varies from between one-sixth to one-eighth of an inch, for internal works. Scagliola is made by a process of a similar nature to the one thus executed, with perhaps some slight differ- ences in the manner of setting up and drying the coat of plastering which forms its base. There are a greater number of small pieces, splinters, "scagliole^^ of marble in the best descriptions of this work, and it is from them that the process derives its name. MM. Darcet and Thenard applied to the interior of the dome of the Pantheon in Paris an encaustic, for the purpose of rendering the stone fit to receive the paint- ings executed by M. Gros, which answered remarkably well for the plaster under similar circumstances. The surfaces to be covered were firstly dried by large bra- ziers for the purpose of driving out the moisture in the stone, and removing all the air contained in the parts exposed to the heat, so that the stone might be ren- dered more absorbent, and that the encaustic might penetrate further into it. A mixture of 1 part of yellow wax, and 3 parts of oil, in which -Vth of the whole weight of litharge had been mixed before melting, was then applied at a temperature of 212^ Fahr, It was laid on with a brush, in frequent coats, until in fact the stone was so thoroughly impregnated with it that it could absorb no more. The pictures above-mentioned have resisted very well for more than twenty years in an exposed position. Should the above mixture be too expensive, another, consisting of 1 part of oil, containing -j^th of its weight of litharge, and of 2 or 3 parts of rosin, m.ay be substi- tuted. This mixture should be allowed to cool, and be remelted before it is applied ; the walls being previously 112 ON LIMES, CALCAREOUS CEMENTS, well dried^ and the encaustic laid on in five or six coats. Plastering which has been thus treated becomes suffi- ciently hard to resist the nail in a very short time ; and it is effectually protected against any changes of the atmosphere. The action of these oleaginous substances is merely to fill the pores of the plaster, and thus to prevent the action of the moisture. They do not appear to enter into any chemical combination. CHAPTER XIV. ON THE SALTPETREING OF LIMES, CEMENTS, AND PLASTERS. A VERY interesting — and at present, unfortunately, a very little understood — class of phenomena takes place when the materials we have considered are exposed to certain conditions. We find that in damp positions, in new works, walls are often covered with a crystalline substance of a white fleecy appearance, and of a slightly acid flavour, which works its way through any ordinary coat of paint; and, as it absorbs the humidity of the atmosphere in efflorescing, it renders the walls damp on the surface, and carries off the paint in large patches. This process is called by workmen saltpetreing, and is in fact the production of saltpetre from the materials employed in the construction of the walls. The very disagreeable effect it produces upon decorations, either internal or external, renders the research of its cause extremely interesting to the architect or the builder; moreover, its action upon the durability of stone is such, that the study of this singular chemical pheno- menon interests the engineer to an equal extent. MORTARS^ STUCCOS3 AND CONCRETES. 113 Saltpetre is^ properly speaking, a nitrate of potassa; but, although it is regarded as the sole cause of the ap- pearances we now examine, it is far from being the only substance produced in the particular instances; for the nitrate of soda and the chloride of potassium are often to be met with in connection with the saltpetre itself. Very few chemists appear to pay attention to the fact that nearly all limestones contain a certain quantity of soda and potassa ; or at least in the analyses we meet with in chemical works no mention is made of their presence. General Treussart was, perhaps, the first to publish any hint upon the subject, when he stated that the artificial cements differed from those obtained from the septaria nodules, inasmuch as the latter contained a small dose of one or the other of those metallic oxides. But his discovery appears to have led no further than to securing a better method of making the articles he sought, and its influence upon the solution of the ques- tion before us was quite neglected. The ancient chemists believed that the production of the saltpetre was to be explained by the combination of the nitrogen present in the walls (arising from a pre- vious combination of the oxygen of the atmosphere with the azote supplied by the decomposition of the animal matters contained in the building materials) with the metallic oxides they might contain. This theory remained unquestioned until M. Longchamp proposed another by which he sought the explanation of the phenomenon of the production of the nitrogen, by supposing that the carbonates of lime and of mag- nesiuj taken in a proper degree of comminution, and properly wetted, could absorb air^i condense it, and 114 ON LIMES^ CALCAREOUS CEMENTS, transform it into nitric acid in the course of time ; ot rather bring it to that state, after condensation, which would cause it to enter into combination with the lime and magnesia, giving rise to the formation of the nitrates of those two substances, and so much the more readily enable it to combine with the potassium, especially if it were present in the form of a carbonate. Under all circumstances, the presence of powerful bases, such as the chalk and magnesia, or the potas- sium, appears to be necessary, and they require to be in a highly comminuted state. Lime in the form of chalk, or a highly porous limestone, is favourable tc the action of the nitrogen. Marbles, and the densest class of limestones, nitrify with great difficulty, hardly at all; and the limes made from them enjoy a corre- sponding immunity from this inconvenience. Thouve- nel appears to believe that these bases only nitrify when in the state of carbonates ; but the extraordinary facility with which the sulphates of lime give rise to the forma- tion of the saltpetre is not of a nature to persuade us of the universality of the law. And, indeed, there are some cases to be noticed hereafter, in which it would appear that, so far from its being necessary that the lime be a carbonate, the nitrification ceases when it be- comes so in an eminent degree, or is at least much retarded. Whichever theory we adopt to account for the pre- sence of the nitrogen, there appear to be certain con- ditions which facilitate the production of the saltpetre. Firstly, a degree of humidity, about equal to that of garden earth, is very favourable to it. At 32° of Fah- renheit, the nitrification does not take place; between i)0° and 70° it is the most abundant. In Sweden, light MORTARS^ STUCCOS^ AND CONCRETES. 115 is considered rather to retard it, and an exposition to- wards the north is always sought for ; but that does not appear so much to be owing to the absence of strong sunshine, as to the evaporating effects of the north winds, which are eagerly desired in the artificial nitre factories. Light, in fact, would rather appear to be without influence in its action than otherwise. The most favourable conditions for the formation of the nitre, indeed, are united in cellars, and other underground constructions ; and it was from them that the French chemists, during the war, extracted the saltpetre neces- sary for their gunpowder manufactures ; especially from the demolition of cellars executed with plaster instead of mortar. The richest of these materials contain some times as much as from 5 to 7 per cent, of saltpetre. The nitrification takes place very freely when sea water and sea sand have been used, so much as to render them totally unfit for works requiring any per- fection of execution. Dumas asserts that there is a very considerable quantity of nitre in the sea salt; if so, it may explain the injurious action of the sea water. Brande, it is true, does not mention nitre as being pre- sent in the sea salt ; but he states that the earthy muriates are so in the proportions of between 5 and 28 per thousand, the sulphates between 6 and 32^ per thousand. The efflorescence upon works executed with sea water is, however, very distinctly and decidedly a nitrate of soda ; and, as it occurs in much greater abundance wherever it is used, notwithstanding Brande^s silence, we may safely assume, that some portion at least of the nitre is furnished by it. It seems hardly reasonable, in fact, to attribute the presence of the nitre entirely to the decomposition of 116 ON LIMES^ CALCAREOUS CEMENTS^ the animal matters contained in the building materials. These in many cases are submitted at times to such a degree of heat as would arrest the process of decom- position ; but, in the case of bricks, we find the nitrifi- cation to take place almost immediately upon their being exposed to the air. It is difficult, also, to explain in this manner the constant formation of new crystals of the nitrate of potassa, which goes on in the caves of Ceylon, and of La Roche Guyon, in France. In the artificial nitre works, it is true that the nitre is obtained by mixing calcareous earths with decaying animal matter; but the latter requires to be present in such large pro- portions, that we hesitate before we can receive it as being the only source from whence the materials used in building derive the quantities necessary. We are forced to seek the explanation of the phenomenon in the action of the chemical bases upon the constituent elements of the atmosphere. It is known, says Dumas, that the azote and the oxygen combine together under the form of nitric acid, by the aid of the electric fluid, and under the influence of water. The presence of such energetic bases as lime and magnesia may, per- haps, be equivalent to that of the electricity; especially as the porosity of the materials enables them to act upon smaller quantities at a time. The practical bearings of this interesting chemical question, upon the professions of the engineer and architect, are as follows : — Firstly. Sea w^ater, or sea sand, should never be used in making up mortar, or plaster, which is likely to re- quire painting, or any sort of decoration, such as paper- ing, stuccoing, &c. For outside works, the use of sea sand which has been well washed in fresh water, and MORTARS, STtrCdOS, AND CONCRETES. 117 exposed for at least six months, may be admitted, but it is still likely to cause a nitrification ; and as the con- ditions of temperature internally are more favourable to that action than externally, it is most likely to mani- fest itself in that direction. There is always a danger attending the use of sea sand ; if it can be replaced, it should therefore be so, even at an increased expense. For such works as sea walls, lock chambers, quay walls, &c., it is not of so much importance that the nitrification be avoided, provided always that the stones used be of such a nature as to resist the destructive tendency of the process. Many of the oolites are not so able to resist, such as the Portland stone, the Caen, and the Bath stone. They should not, then, either be used in conjunction with mortar made with either sea sand or sea water; nor should they, in any case, be exposed to the latter. The purer crystalUne lime- stones, and the granites, resist this cause of chemical decomposition much better, and should be employed in such positions in preference. It is, however, to be ob- served that there are some kinds of oolite, such as the Ranville stone, near Caen, the Roach beds of the Port- land, which are as little affected by the sea water as the stones just mentioned. Secondly. When it is absolutely necessary to use such materials as we know to be exposed to the incon- venience of nitrification, it is advisable to take early precautions with the view of preventing the action of the atmosphere upon the chemical ingredients. We see that in whatever manner the bases absorb the nitro- gen, whether from the decomposition of the animal matter, or from the condensation of the gases, that the absorption could not take place unless the atmosphere \18 ON LIMES, CALCAREOUS CEMENTS, were in contact with the internal structure. If, then, we protect the interior in some manner by a coat of paint, or an encaustic, for instance, we shall probably stop the action of the nitrification. It is thus, doubt- lessly, that we may account for the fact that if the Roman cement be painted as soon as it is dry, it does not assume the action in question ; but if it be left for any length of time unpainted, it becomes useless to attempt to execute such work. The atmosphere has entered the pores of the cement 3 the nitrates will cause any coat of paint to fall off. Such a precaution can, however, only be successful when the body of the work is not of a nature to furnish its own nitrogen, if such an expression be allowable ; or when it is in such positions, and of such dimensions, as not to derive it from any other quarter. If, for instance, a wall be built of bricks made from the alluvial mud of the embouchures of rivers, no precautions can prevent the saltpetre from forming. Engineers or architects, then, who have any decorative works to execute in places where such materials only are used, must detach them from the walls. If the wall be thin and the coat of encaustic penetrate very deeply into the plastering, it may happen that the saltpetreing may take place entirely on the outside ; but this is a mere chance, that is to say, it is an action we can neither explain nor control; one, therefore, no prudent man would calculate upon. In very thick walls we often find that the salt- petreing does not take place on both sides, only on the weather (or exposed) side. Possibly this may be ex- plained by supposing that the limes in the interior have had time to become more perfect carbonates be- fore the air can have found its vray through the pores. MORTARS, STUCCOS, AND CONCRETES. 119 But if the process once begin with such thick walls it never leaves off, at least within any reasonable time. The workmen in London have a practice which may some day serve as a guide to more scientific examina- tions upon the subject. It consists, whenever they use Portland stone in elevation, in covering it with a wash made of pounded stone-dust and sand, which is rubbed off upon cleaning down the work. Th!s very simple precaution serves temporarily to protect the stone against the formation of the saltpetre. But it is to be observed that the precaution alluded to is not effectual to stop the process of the saltpetreing, otherwise than temporarily, although it diminishes its force afterwards. The process is resumed, but in a weaker degree, as soon as the coating is removed. The most reasonable mode of accounting for the action of this wash is by supposing that it affords a protection to the stone, by closing up its pores, during the time it is passing from the state of a subcarbonate to a perfect carbonate of lime, or from a protocarbonate to a percarbonate ; for a very distinct change takes place in the chemical nature of limestones of every description upon exposure. These precautions are unfortunately very doubtful in their results ; at every moment we are exposed to see the materials which contain soda and potassa take up the action of saltpetreing. Many noble frescos have perished in this manner ; many of the finest buildings have been ruined by the decomposition it superinduces in the stones of which they are built. The study of the mode of its action becomes therefore highly important ; but it is to be feared that it will continue to be treated with the neglect which has hitherto been the lot of the whole science of chemistry applied to the arts of building. 120 ON LIMES, CALCAREOUS CEMENTS, ETC. It happens, unfortunately, that very few architects oi engineers are chemists ; few chemists are aware of the nature of the questions it concerns us so deeply to have solved. M. Kuhlman^s researches upon the subject immediately before us — viz., the nitrification of building materials — are, it is true, of the greatest interest, and have done much to elucidate the more obscure parts of its theory; but neither he, nor the various French or German chemists, nor our own countrymen who have lately devoted so much time and attention to the phenomena connected with the use of lime, have succeeded in over- coming the practical difficulties which are superinduced by the nitrification. Subsequently to the Exhibition of 1851, the whole of this branch of applied chemistry has been brought more distinctly under the notice of the scientific world ; and it is to be hoped that shortly the obscurity in which it is still involved will be dispelled. In the meantime, however, professional men, architects, and engineers would do well to study for themselves, with more attention than it is to be feared they usually do, the practical applications of the important materials to which it has thus been attempted to call attention. GEORGE R. BURNELL APPENDIX A. (Page 22.) In England, wliere tlie rule of thumb " prevails so extensively, it is the general practice to receive the blue lias lime as a good and a satisfactory hydraulic lime in all cases, and without any regard to the positions in the series that the beds of that formation may occupy. It is, however, necessary to remark, that every bed of the blue lias limestone contains a different proportion of the silicate of alumina, in combination with the carbonate of lime ; and that, therefore, the powers of setting under water must be very different in the limes obtained from them. Even at the base of the Liasic series, the differences that occur are as grea t as between about 8 per cent, of the silicate of alumina and 90 per cent, of car- bonate of lime, and 64 per cent, of the former ingredient to 34 per cent, of the latter. The first of these would yield only a moderately hydraulic lime ; the latter would yield, on the contrary, a most energetic cement, if burnt and ground. The peculiar properties of the blue lias limes have been established upon the results that have followed the conversion of the middle beds of the series, which con- tain from 16 to 20 per cent, of the silicate of alumina. It would be, of course, easy to distinguish the best qualities of blue lias lime, as in fact it is easy to predicate the nature of any description of that material. Thus the lumps of burnt limestone should be rather large, and they should present on all sides a conchoidal fracture ; the lime should swell but little in slacking, and it should not give out much heat, nor yield to the effect of the water before about two to five minutes. A lime of this description requires to be slacked before being mixed with the sand, for uso in a building ; but as the London builders have a fancy for the employment of lime " hot,'^as they call it, it is safer to employ the blue lias lime, after being ground. The best descriptions of bluo lias lime that enter into the consumption of the London market, are obtained from Warwickshire, Leicestershire, Dorsetshire, the neighbourhood of Bath, Aberdare, Rugby, &c. ; but they are all of them of very variable composition, and they require to be used with great precaution ; at least until the precise nature of the beds has been ascertained. 122 APPENDIX. APPENDIX p. (Page 45.) Since this book was written time has enabled experience ro pronounce upon many of the processes and the materials that are employed in the preparation of limes and cements ; and amongst these it has decidedly settled the question as to the superior qualities of the Portland cement, both as regards durability and as to the powers of resistance that it may attain in comparison with the natural cements, or the best hydraulic limes. There have not been introduced, in the pro- cess of preparing the Portland cement, any modifications ; or have the rules observed with regard to the burning of the mixture of the chalk and clay, of which the cement is composed, been in any way altered, excepting, of course, some trifling modifications which have borne upon the working details of the fabrication. The use of the cement has, however, spread greatly ; it is employed in enormous quantities, both for hydraulic works and for those that are not exposed to the peculiar danger that attends the use of the cements, or artificial hydraulic limes, in sea or ordinary river water; it is employed, in fact, wherever the conditions of the buildings are such as to require great powers of resistance to external forces ; and in all these cases it has been found to be far superior to the natural materials of the same class ; so much so, in fact, as to have entirely superseded their use, wherever the freight, or the conditions under which the natural cement stones or hydraulic limes occur, allow any thing like an equality of price. It therefore appears to be necessary to enter more into the theory and practice of the manufacture of the Port- land cement than had previously been done in the earlier editions of this work. The Portland cement, as manufactured in the neighbourhood of London, is made by a mixture of the chalk and clay of the alluvial formations of the lower parts of the Thames and Medway ; the chalk being derived from the upper members of that formation, oi from the chalk with flints, and the mud being principally derived from the deposition of the tidal waters that have swept along the shores that are bounded by the chalk cliffs. These ingredients are ground with a great quantity of water under edge rollers, and tliey escape through species of sieves in the requisite proportions, to flow off into large backs or reservoirs, where they part with a great proportion of the water used for their levigation. Of course there can be little certainty as to the proportions of the chalk and clay that are thus mixed, as they may, both of them, vary much in their chemical composition ; but as a general rule the manu- facturers endeavour to secure a mixture in which the carbonate of lime should be present in about the proportions of 60 per cent, of the whole mass, the silicate of alumina in the proportion of 34 per cent.^ and the rest would be composed of various ingredients that APPENDIX. 123 are found in tlie alluvial mud. After the mixture lias been allowed to settle in the backs, it is dug out in the plastic state, and is then submitted to a species of dessication ; it is put into the kilns in the state of a hard paste, and is there subject to a great heat, such as is capable of producing a pyrogenic compound of the silicate of alumina and lime. As was said in the text, great care is required in the management of the kilns, in order to secure, as nearly as possible, an equal degree of calcination in all the materials that enter into the charge ; but the principle that the manufacturers aim at in this operation, is to give, as much as possible, a uniform degree of heat to every particle of the mixture, as they are thus enabled to calculate upon the setting qualities and the various physical con- ditions of the cements. There are three qualities that frequently characterise the products of a kiln — the under burnt, the properly burnt, and the over burnt ; and it is upon the judicious mixture of these that the success of the operation of the burniag must depend. The Portland cement is ground under millstones, placed so as to revolve horizontally, and it escapes from these stones through a sieve, to be spread out on a floor, where a species of cooling and of air slacking is allowed to take place, which is found to be very beneficial to the future stability of the works into the composition of which the cement enters. The specific gravity of the Portland cement, ground in this manner, may be taken at about 1*200, water being 1 -000, and it is believed that this weight is a favourable condition ; in fact, the consumers of Portland cement seek this q[uality of weight to such an extent that an ingenious system of fraud, which consists of mixing that article with the slag of the iron works, has lately been practised to a considerable extent. The cement, after being ground, is passed through a sieve that has 46 holes to the square inch, and is packed in casks which are kept carefully water-tight. The usual conditions of setting that are imposed by hydraulic engineers are, that when gauged neat — > that is, without the mixture of any sand — the cement shall set, in the open air, within the space of not less than two hours, so that it should be able to support the weight of a Yicat's needle, loaded with the weight of 3J lbs. : the cement that sets in less time than the above is rejected in all cases where the engineers attach importance to the quality of this material. Blocks of the cement mixed with sand, in the proportion of 6 of cement to 10 of sharp sea sand, carefully sifted, are prepared for trial by the authorities of the Cherbourg breakwater, and they are immersed in sea water that is kept cool, and is renewed every day for the space of 120 hours J the size of the blocks is made 8 inches long, by 4 inches wide, by l-^ij of an inch in thickness, and two nicks, or depres- sions, forming collars, are made in the middle of the blocks, which reduce the section of them to the square of 1^ inch on a side ; the test weight, that is rigorously enforced for these blocks, la o6 lbs. per inch superficial of the sectional area, or about 144 lbs. 124 APPENDIX. on the total sarface. The Metropolitan Board of Works, however^ impose the resistance of 500 lbs. on the square inch sei'^n days after being made in an iron mould ; but in this case the neck is cast, not cut out, and the blocks are immersed in soft, not in salt, water. Both of these conditions seem to be necessary for securing the best qualities of Portland cement. Of course the attainment of these conditions involves a great deal of expense, and there cannot be a doubt but that great economy would result from the use of a natural material that would present the same composition as the chalk and clay, that are mixed with so much labour, and dried at so great an outla}^ The attention of manufacturers has long been turned to this point, and the makers of blue lias lime have, amongst others, tried to introduce the method of burning that lime to a high point, and mixing it with the burnt clay associated with the limestone in the same formation. But there appear to be difficulties attending the composition of this mixture that entail great risks in the use of the resulting material ; and the mixture of chalk and clay, before burning, has been found hitherto to be the most adapted to secure the degree of hardness, the weight, and the time of setting required. So that the blue lias cements, the Boulogne cements, &c., have generally failed to satisfy the requirements of hydraulic engineers ; though they may answer tolerably well for the ordinary processes of building. The same thing ma}^, it is believed by the author, be asserted with respect to the cement made by Colonel Scott, of the Boyal Engineers, that seems to be well adapted to obtaining a cheap substitute for Portland cement, provided the peculiar hydraulic properties of the latter are not called into play ; but which would in all probability fail, if exposed to the continuous action of moisture, especially when charged with the salts of the ocean. The Scott's cement is made, in fact, by exposing the fresh burnt lime, heated to redness, to the fumes of sulphur that is burnt in pots under the grate. In this manner a description of sub-sulphate of lime is formed, that has the properties of setting with great rapidity and hardness, but which the author believes would be found to yield to the effects of the chlorides that are contained in the sea water, if not also to the long continued action of the causes of decay in the cement if used in open air. Scott's cement appears to be an admirable material for the execution of brickwork that is to be protected from the damp by a coat- ing of cement, or for the execution of the internal rendering coats of buildings, that require to be quickly dry ; but there is little about the process of making these cements that should warrant the belief that they can acquire any hydraulic pro- perties by it ; on the contrary, the formation of the sulphate of lime is a permanent source of danger to the stability of the resulting compounds when they are required to 6et under ^ea APPENDIX. water, as we have had occasion to remark with respect to the artificial cements that were used at La Rochelle, and other places on the French coast. Colonel Scott's process contributes, at any rate, to the rapidity of setting, and to the hardness of the mode- rately hydraulic limes. It is questionable whether it would produce a great effect upon the more energetic materials of that class ; and it would certainly do harm if applied to the calcination of the natural or the artificial cements. Such as it is, however. Colonel Scott has the merit of having placed at the command of the builder a valuable process for improving the ordinary limes of the country, for all the purposes of internal decoration, or for the execution of works that are usually performed in limes of the qualities that are known under the names of chalk or of grey-stone limes. The use of Scott's cement for the purpose of making concrete will be noticed hereafter more in detail, when the appli- cations of that material, which has been sadly neglected of late, are considered. APPENDIX C. (Page 62.) The peculiar properties of the scoriae of iron forges seem to have inspired the manufacturers of that metal with the idea that they might derive a profit from this refuse of their manu- facture, by its application to the preparation of cements and hydraulic limes for concrete, or for the execution of the rubble masonry inserted under the foundations of public buildings. At least, attempts have been made lately to introduce the scoriae of iron furnaces and of the puddling mills, with the view either of increasing the resistance of the limes and cements, or of increasing their weight, in case they should not be of the precise character that is required of the limes in question in this respect. But it appears that, in all the cases hitherto tried, the scoriae contain the silicate of alumina, and the iron, in the form that might be converted into the mixture of the lime and sand, in an entirely inert state ; and thus, that their presence does but add to the difficulty that attends the setting of the limes and cements with which they are associated, by interposing a fresh substance that would hinder the completion of the induration. Perhaps the introduction of this substance, which must be heavy in the ground state, may be of service in cases where it is desired to increase the weight of the cement or lime used; but this can be only by reason of the mechanical mixture of an ingredient that would itself be quite indifferent to the processes going on around it, and it cannot add anything to the qualities of the other materials to which it is presented. The same remark may be extended to K i26 APPENDIX. the whole class of the so-called metallic cements; they contain^ in fact, those materials that might be of service, generally speak- ing, in that state that renders them unfit for entering into fresh combinations, especially when they are derived from processes of manufacture that require the intervention of great heat. The effect of this heat seems to be to render the combinations of the alumina, potass, iron, &c., stable, and such as cannot be broken up for the formation of new compounds with the lime with which they are associated. APPETOIX D. (Page 78.) There has been a considerable amount of interest attached of late to the attempts made by M. Coignet to introduce what he calls the heton agglomeH^ and by Colonel Scott, of the Koyal Engineers, to introduce the use of concrete made l3y his cements and shingle, for the purposes of building ; and the results that these two gentlemen have attained are sufficiently remarkable to merit our attention on the present occasion. Colonel Scott has executed in this manner the shells of buildings that are formed of a waggon-head shape, and that are fourteen feet at least in their clear span, and he used for the purpose a mixture of one part of his cement to ten parts of sand j the walls that had to carry the roof, that was made in the same material, being only nine inches thick. M. Coignet has executed many thousand francs' worth of work in the heion agglomere in the sewers of Paris ; he has built entirely in that material the church of Vesniet, near Paris, and he has applied it to the execution ef railway and common bridges of fifty feet span, at least ; so that it can no longer be considered that the experiment is upon trial. In fact, the results that have been attained at the Dover, Alderney, Cherbourg, Marseilles, Algiers, &c., works, had long since proved that concrete was susceptible of being used in building operations like any ordinary stone, and all that M. Coignet has done in this case has been to demonstrate the fact in a striking manner. The difference between M. Coignet's system and Colonel Scott's, consists in the former gentleman employing every description of lime in the preparation of the hStoriy which he takes every pre- caution to have slacked with just the proper quantity of water to ensure the hydration of the lime, and then carefully to triturate the mass, and to compress the ingredients in moulds by a system of ramming. The best materials that are thus produced are com- posed of a mixture of the slow-setting artificial cements, with a good hydraulic lime and a proper proportion of sand ; and great skill is required in so apportioning the lime and cement, that the APPENDIX. 127 powers of the resulting mass should present everywiiere the same powers of resistance to the weights or forces they may have to resist. Of course, there can be no difficulty in varying the propor- tions of the lime and cement to produce this result, though M.Coignet neglected this precaution in the building of Vesniet church ; nor can there be any difficulty in observing the precau- tions that are required to provide for the contraction and expansion of the masonry in a monolithic bridge, such as that gentleman has executed. Well and judiciously used, there can be no reason why Coignet's agglomerated heton should not be employed for the execution of ordinary descriptions of masonry ; or, indeed, why that description of works should not be performed with any description of common h6ton (using that word in the sense of a mixture of lime, sand, and shingle) rammed in a mould. The same thing may be said of Colonel Scott's concrete, and, indeed, of any other description of that material ; but it seems to be better in all cases to mix the lime or cement with sand first, to bring it into the state of mortar, and then to present to it the materials round which it is intended to crystallise. Colonel Scott has, however, had sufficient influence with the War Office to per- suade them to make an application on a large scale of this concrete, made in the usual manner, to the huts and stables of the camp at Aldershot, hitherto with markedly successful results, both with regard to the durability and the economy of the constructions to which this system is applied. The theory is, that a masonry so prepared, being a rough rubble masonry without any bond, ought to be executed of the thickness of one-third more than ordinary brickwork ; but this must in all cases be regulated by the weight that is brought upon the bearing section, and the weights given in the text, page 71, ought in no instance to be exceeded, in the early days of the experiment at any rate. The failure of Mr. Kanger, and of many others, in their attempts to employ concrete as a materia] of construction, can, therefore, only be considered as proving that they did not understand the theory of limes ; yet the College of Surgeons, and the shops in Pall Mall, that Mr. Ranger executed, stand to this day as a proof that^ when well prepared^ the concrete made in ordinary style is capable of supporting the action of the London atmosphere successfully. Concrete might be very advantageously employed in the backing of quay or river walls, or in the execution of rubble masonry for the purposes that Colonel Scott has applied his cement to. The quay walls of Havre are, in fact, backed with a kind of masonry of this description ; and a remarkably large and successful instance of the use of concrete, made in part with Portland cement, exists in the facings and bai.k- ings of the basins of the Victoria Docks, London, executed under the directions of Mr. G. P. Bidder, C.E. The different descriptions of limes and cements used in England would, no doubt, require to be treated in a different manner than they are usually done, in ordei 128 APPENDIX. to secure the equality of their setting j but it is precisely to th© attainment of this condition that the efforts of the people em- ploying those materials ought to be directed. Well selected blue lias lime, or grey-stone lime, mixed with pounded brick dust, would do as well for the execution of concrete, for the ordinary conditions of exposure to the weather, as even the cements of Colonel Scott, or any other manufacturer. For exposure in sea water there appear to be some causes at work that would render necessar}^ the employment of Portland or Eoman cement; buf: even in this case the success of the application of the concrete blocks at Dover Harbour and the Cherbourg breakwater, shows that the resources which that material offers to engineers and architects are neglected, either in consequence of ignorance of the theory of limes, or of want of boldness in trying experi- ments on the part of the professional men, more than in consequence of the nature of the material. The admirable manner in which the works of concrete executed by Koman and mediaeval archi- tects have stood the effects of time, must alwa3^s excite our surprise that the use of that material should have been so long neglected, and the building arts deprived of the advantages it offers for the execution of monolithic structures, or those made by the agglomeration of small materials. There has been a great deal of attention also called of late to the invention of Mr. Ransome, which was noticed in the original edition of this work, and which has subsequently received con- siderable improvements at his hands. This invention consists, as most persons interested in these matters are aware, of a mixture of the silicate of soda with sand, so as to produce a material susceptible of being moulded, which is then immersed in a bath of the chloride of calcium, and subsequently washed thoroughly, so as to remove the salts that would effloresce upon the surface of the material. The theory upon which this process is based is perfect, and the double decomposition of the silicate of soda and the chloride of calcium, is such as must produce the silicate of lime, that would act as the cementing material to the sand, leaving the chloride of sodium to be washed off ; but this salt is accompanied with other impurities which are eliminated in the process of con- version, and the greatest care is required to ensure the freedom of the mixture from the effects of such foreign ingredients. Mr. Ransome has hitherto succeeded in effectually destroying the appearance of the salt ; but the danger of the manufacture from this cause will always attend it, and thus render it a process that will be entirely a matter of confidence between the employer and the manufacturer. In Mr. Eansome's hands, or in those of the people that he may bring up, there can be little ground for hesi- tation in the use of this material for all the purposes of internal decoration, or even for external decoration in cases where the salt has been effectually withdrawn j in careless hands there must be APPENDIX. 129 considerable danger of the efflorescence of salts, which may com- promise the painted decoration that may be applied to the material 80 produced. As the colour of the mixture can be regulated to any tone by the intervention of the metallic oxides, there is, perhaps, little danger to be feared from this source; but there would always remain a considerable amount of doubt as to the application of the patent concrete stone, on the score of the dis- agreeable effects produced by the efflorescence of the salts. The bath of the chloride of calcium, in which the mixture of sand and silicate of soda is immersed, it may be important to add, is kept at a point of ebullition by means of the passage of a steam-pipe through it ; the washing out the salt is effected by a stream of cold water j the mixture of the silicate of soda and the sand is effected by the use of a pug-mill. APPENDIX E. (Page 96.) The kind of rendering that is so much used in India under the name of CJmnam^ appears to merit a passing notice on the present occasion. There are some principles brought into play in the setting of this form of lime that are indirectly connected with the action of the oleaginous cements, so that it may be as well to dwell upon them. There are several kinds of this chunam^ according to the locality where it is employed, and to the uses to which it is proposed to be applied. In the interior of the country it is said to be prepared most usually from hutikar nodules — calcareous concretionary masses, from the size of a bean to blocks of some hundreds weight, which are found imbedded imrseme in almost every portion of the alluvial soil of the great plains of India. These nodules consist mainly of carbonate of lime, mixed with a little clay in impalpable powder. This, when burned, is mixed with coarse or fine siliceous sand, and tempered thoroughly with water, to which most generally (but not always) a coarse syrup or molasses from the native sugar is added in small quantity . The only real use of the molasses appears to be to retard the too rapid drying of the fresh laid chunam in the torrid climate of India. On the sea coast shells are burned, and mixed with sand, which is treated in the same manner. The practice is to boil with the syrup, called locally jaggree, some description of fruits, but these do not appear to have much influence on the setting of the lime ; and immediately upon application, is added a portion of short tow, if it be desired to employ the chunam as a stucco. The kind that is habitually used as a material for rendering walls is obtained by 130 APPENDIX. the calcination of the purest limestone, or shells. That is beaten up with jaggree^ mixed with water ; and this kind of chunam be- comes very hard, so as to bear, in fact, a polish. In the patient hands of the Hindoo labourers the use of this material, no doubt, produces excellent results ; but as the whole process of manufacture employed in the preparation of chunam is, in fact, founded upon the retardation of the setting and the careful manipulation of the material in place, there can be little reason to regard this applica- tion as anything more than a local one, that is to be accounted for by the want of limestone in mass over great areas, and by the low price of labour, in India. APPENDIX F. (Page 105.) A discovery, by a Mr. Westmacott, has lately formed the object of a patent, and it has been taken up by a house in London of some considerable influence, with a view to augmenting the resistance of the rendering coats that are executed in lime, by the mixture of pounded limestone witli that material, and sand. This is, in fact, nothing more than the application of the principle mentioned in the text, p. 77, where the tendency of the lime to crystallise around a gangue of the same nature as itself, is referred to, and the inference is drawn that the presentation of the crys- tallised forms of carbonate of lime would be favourable to the solidification of the mass " of concretes, hetons, or mortars." It is to be observed that ^Ir. Westmacott mixes with the chalk lime that he employs, considerable quantities of pounded chalk, or of some other equally common description of stone that has a base of carbonate of lime, and thus he obtains a mixture that is capable of setting with greater rapidity, and consequently with less chance of dis- colouration of the surface ; but here all the advantage of Mr. Westmacott's process ceases. The mixture of the pounded lime- stone does but add to the strength of the resulting material, inas- much as it presents to that body a substance that is already sety^ and that is capable of assisting in the process of the conversion of the hydrate of lime into the carbonate of that base ; but this must be at the expense of the power to carry sand, and the whole economy of the process must depend upon the relative values of *he sand, or of the pounded limestones in the precise localities where the materials are employed. The advantage of the process is simply that which would follow from the improvement which would be effected in the conditions of the crystallisation of the lime ; it in nowise alters those condition,'?, or introduces a new principle, of what manner soever. APPENDIX. 131 APPENDIX G. (Page 107.) The patents by which Keene's cement and the Parian cement were protected have lately lapsed by time, and the consequence has been that the lime-burners, being at liberty to apply the processes on which they are founded, have been stimulated by the competition of the trade to improve the manufacture of one of these articles. Hence the manufacture of the Keene'fi cement, in particular, has been very much advanced, and the use of that material now can be safely recommended wherever it may be necessary to employ a hard cement, which it would be necessary to paint immediately after its application. The princi- pal objection to the use of this material was, that its liability to the efflorescence of the salts, that threw off the paint and left large blotches on the walls ; this has been remedied by neutral- ising the acid with which the sulphate of lime is treated. It does not appear that the manufacture of the Parian or Martin's cemente has been sensibly improved of late, and the use of these plasters, as they ought to be called, is tlierefore attended with the same amount of risk that they were previously exposed to, which was far less than was the case with Keene's cement; yet the improve- ment of the latter has enabled that material to be substituted very largely for its rivals. There are some curious conditions attending the use of Keene's cement with respect to the rendering coat that is laid upon the wall, which yet require to be experi- mentally settled. It would succeed admirably wherever it is de- sired to have a hard and non-absorbent surface for walls, as in the case of hospitals, or for skirtings, floors, angle staves, &c., or wher- ever it is necessary to paint the surface at once. The specific gravity of the Keene's cement is very low, a bushel of it only weighing about 70 or 75 lbs. at the utmost ; whereas Portland cement weiahs from 100 to 110 lbs. per bushel. INDEX. Aidershot, use of Scott's cement for build- ing huts, &c., at, 127. Alumina, influence of, on the setting of hydiaulic limes, 22. Alumiaa, silicate of, its importance as a constituent of hydi-auiic limes, 19. Appendices, 121. Arenes described, 65. Aitificial hydi'aulic limes, experunents to form, 16. Asphalte described, 90. Assyrians, cement used by the, 1, Atmosphere, influence of the, on mortar, 70. Babylonians, cement used by the, 1. Basaltic rocks, experiments on, 61. Bergmann on hydi'aulic hmes, 6. Berthier's analyses of puzzolancs, 60; analyses of scoriae and slags, 62 ; ana- lyses of cement stones, 80; experi- ments on tlie composition of hydi-aulic lines, 17 Berzelius on hydrate of lime, 10. Beton gglomere, Coignet's, 126 ; work executed with, 126. Beton, difference between concrete and, 70, Beton used by Vicat for the bridge of Souillac, 77, see also Concretes. Biiumen described, 90. Bituminous cements : asphaite, som-ces of, 90 ; described, 91 ; method of using, 92 ; method of using for coating arches, 92 ; meUiod of using for paving, 92 ; mixture of, 91 ; use of, 90 ; coal tais, 93 ; method of using coal tars, 93. Bl ue lias lime, variation in the quality of, obtained from different series, 121 ; best, where obtained, 121. Bricks, cement from, 06. Bulk, increase of the, in slacking limes, 48 ; loss of, in making mortar, 70. Calcination of limestones, process of, 25. Cements, 78; bituminous, 89; from bricks, 56 ; failui-e of ditto, 56 ; experiments oa the cause of failui'e, 57; effect of the mixture of scoriae with, 125. Cements— French, 88 ; Keene's, 107, 131 ; for mosaic work, 94 ; metallic, vahie of, 126; oleaginous, 94; Parian, 107, 131 ; Parker's Koman, 79 ; Portland, 88, 122 ; manufacture of ditto, 42, 122 ; Roman, 79 ; causes of Uie failure of Roman, 86 ; Roman cement stones, 81 ; analyses uf ditto, 80; calcination of ditto, 81; spe- cific gravity of ditto, 83 ; proper use of Roman cement, 86 ; resistance of ditto, 84; time of setting ditto, 83; use of ditto, 83; use of ditto, 83 ; use of ditto for foundations, 86 ; artificial Roman 87 ; Scott's, 124 ; Vicat's classification of the materials used for, 64; West- macott's, 130. Cendi'ee de Toui-nay, use of, 63. Chalk, hydraulic properties communi- cated to, by alum, 50. Cherbouig, use of Portland cement in blocks at, 78. Chunam, manufacture 0 , 129 ; use of in India, 130. Clinkers, liydi-aulic properties of, 63. Coal, objections to, as fuel for burning limestones, 29. Coal cinders, analysis of, 62 ; value of, as an ingredient 01 cement, 63. Coignet's beton agglomere, 126 ; wo^^ executed with, 126; value of, 127. Coke, use of, as fuel for burning lime- stones, 29. Colom- of limestones as a test of quality, 27. Concretes : action of water on, 128 ; addi- tion of broken limestone to improve tlie qualities of, 77 ; antiquity of, 72; at- tempts to produce blocks of, /or build- ing pm-poses, 77 ; beton used by Vicat for the bridge of Souillac, 77 ; cause of its failure as a material of construction, 127 ; defined, 71 ; difference between beton and, 72 ; excellence of Roman, 128 ; for sea or river works, 75 ; proper 134 INDEX. state of the lime for making, 74 ; quick Betting, proportions for, 74 ; resistance of, 78 ; uses of. 71 ; usual method of making, in London, 73. Construction of limekilns, 37. Cylindi ical lunekilns, 30. ve Saussure on hydraulic limes, 6. Descotils on hydraulic limes, 6. Dover pier, use of blocks of Portland cement in constructing, 78. Eg)rptians, use of mortar by the, 2. Encaustic, for using as a ground foi" painting on stone, 111. Etruscans, use of mortar by the, 2. Fossiliferous limestones, unequal setting of, 23. Fuel for burning limestones, influence of, on the quality of lime produced, 39. Geological distribution of limestones, 21. Geological formations explained, 20. Greeks, use of cement by the, 2. Gypsum, soui'ces of, 97 ; described, 98 ; calcination of, 99 ; method of procuring, 99 ; preparation of, 101 ; qualities of, 102; to find the quality of, 111; uses of, 103 ; use of, for manui*e, 106. Havre, quay walls of, 127. Hydrate of lime, characteristics of, 10; defined, 13 ; properties of, 14 Hydraulic cements, Smeaton's experi- ments on, 4. Hj'^draulic limes, acting constituent of, 6 ; Berthier's method of analysing lime- stones to ascertain their value as, 24 ; endeavours to form artificial, 17 ; ex- periments to discover to what consti- tuent they owe their power of setting in water, 16 ; geological position of limestones for forming, 22 : method of slacking, 47 ; increase in bulk by slack- ing, 48 ; reworking evils of, 49 ; meUiod of slacking in London, 51. Hydi-aulic limes, superiority of natural to artificial, 45, 73. Hydraulic limes from the ashes of lime- kilns, 37. Hydraulic limes, artificial, 39 ; advan- tage of using an alkaline solution with, 44; blue has cement, 43; inferiority of, to natural, 45 ; manufacture of, at Mendon, 41 ; methods of preparing, 40; variation in the quality of lias lime obtained from different series, 121 ; Portland cement, manufactm-e of, 42 ; proportions for, 41 ; superiority of, to puzzolanos, 40. Iron, oxide of, its properties as an ingre- dient of hydraulic limes, 17. Italian method of using stuccoa, 109. Keene's cement, 107; improve.iient of, 131 ; weight of per biLshel, 13; , Kilns, lime, described, 30; arrangement of, 31 ; attempts to employ the waste heat of, 36 ; rules on the construction of, 37; running, objections to, 33; management of running, 34 ; with- drawing lime from running, 34 ; use of the ashes of, 36. Kuhlmann's experiments on the use of alkalies with artificial hydi'aulic limes, 44. Lille's, R. de, experiments on artificial cement obtained from bricks, 56. Lime, blue lias, variation in the quality u^. i;i. Li J' e, • arbonate of, 9. Lime from oyster shells, 37. Lime, hydi-ate of, its characteristics, 10. Lime, hydraulic, acting ingredient of, 6. Lime, importance of slacking separately, in making mortar, 66 ; loss of weight by calcination, 10 ; method of slacking, 47, 51 ; pure composition of, 8; sulphate of, 97 ; superiority of that burnt in conamon, to that of running kilns, 35. Limekilns described, 30; construction of, 37 ; running, 33. Limes, absorption of, by water, 52 ; clas- sification of, 11; conversion of, into mortar, 51. Limes, hydraulic, experiments on, 6. Limes pi'oduced by limestones of varying composition, 16. Limes, properties of, 14 ; re-carbonisation of, 51 ; slacking of, 46 ; object of slack- ing, 46; Roman method of slacking, 46 ; method of slacking hydraulic, 47 , method recommended by Vicat, 47; increase in bulk by slacking, 48; re- working of, 49 ; attempts to explain the cause of phenomena connected with the setting of, 49 ; Smeaton's ex- periments on liydi'aulic, 6. Limestone, addition of broken, to con- crete, 77; Berthier's method of ana- lysing, 24. Limestone, calcination of, 24 ; process of, 25 ; change of colour during, 27 ; effects of being over or under burnt, 28 ; fuel for, 29 ; objections to coal fuel, 29 : kilns for, 30 ; arrangement of kilns, 31 ; heat to be obtained, 32; time necessaiy for, 32; method of ascertaining, if com- pleted, 33 ; running kilns, 33 ; loss of weight by, 37 ; diminution in bulk, 37 ; influence of fuel on the quality of lime, 38. Limestone, composition of, 9 ; division of, 9 ; form of table for making observa- tions on, 23 ; geological distribution of, 21 ; geological position of, for hydraulic, 22; limes produced from, of varying composition, 15 ; unequal slacking of lime from those containing fossils, 23 ; where found, 10. Magnesia, experiments to detennine th« proportion of, iu hydi'aulic limes, 18. INDEX 135 Manure, use of plaster for, 105. Martin's cements, 131. Mastics described, 94; composition of, 95 ; Thenard's, 95 ; Vauban's, 96 ; uses of, 94. Mendon, manufacture of artificial hy- draulic limes at, 41. Mortar, antiquity of, 1 ; resistance of, 71 ; solidification of, in the interior of large masses of masonry, 52 ; use of, by tJie Eg3rptians, 2 ; use of, by the Etruscans, 2. Mortars, making of, 66; atmospheric influence on, 70 ; best proportions for puzzolanos, 69; gi'eatest proportion of sand for hydraulic limes, 69 ; hydi'aulic limes should be only mixed in the quantities required, 69 ; importance of slacking lime separately. 66 ; influence of the position in which the mortar is to be used on the ingredients, 71 ; loss of bulk in the material, during the process of making, 70; method of slacking the lime, 67 ; proportion of sand, 68 ; pi-o- portiDn of puzzolanos, 69 ; proportion of water,. 69; quality of water for, 70; tables of ingredients, for different pur- poses, 65. Morveau, G. de, on hydi-aulic limes, 6. Mosaic works, cements for, 94. Nitre, presence of, in sea salt, 115. Oleaginous cements, 94. Oleaginous mastics described, 94 ; com- position of, 95 ; Thenard's mastic, 95.; Vauban's mastic, 96 ; uses of, 94, 96. Oxide of ii'on, properties of, as an element of hydraulic limes, 17. Oyster shells, lime from, 87. Parian cement, 107, 131. Parker's Roman cement, 79. Peat ashes, use of, for cement, 63. Petot's experiments on the calcination o^. cement stones, 82. Pit sand, 54. Plaster, use of, for manure, 105. Plaster, Keene's cement, 107. Plaster, Parian, 107. Plastering described, 102; English sj's- tem, 104 ; French system, 103 ; French ceilings, 104 ; French walls, 103, see also IStuccos Pimii.s, mention of lime and cements by, 3. Portland cement, manufactui-e of, 42, 122 ; specific gravity of, 123 ; tests of the qua- lity of, 123; test of, at Cherbourg, 123; test of quality, required by the Metro- politan Board of Works, 124 ; value of, 122 ; weight of, per bushel, 131 ; at- tempts to form a substitute for, 124; use of blocks of, for building purposes, 78. Puzzolanos described, 59 ; analyses of, 60 ; geological position of sands and clays for forming, 21 ; superiority of .irtiticial hydraulic limes to, 40. Ranger, cause of failui'e in his use ol con- crete, 127. Ranger's ai-tificial stone, 77. Ransome's artificial stone, 128 ; manu* facture of, 128. River sand, 54. River and quay walls, use of concrete for backing, 127. Roman cement, 79; cause of failui'e of, Roman cement, proper use of, 86 ; resis- tance of, 84 ; time of setting, 84 ; use of, 83. Roman cement stones, 81; analyses of, 80; calcination of, 81. Roman concrete, excellence of, 128. Running limekilns, 83. Saltpetre, 163 ; presence in sea salt, 115. Saltpetreing of limes, &c., 112; inquiry into the cause of, 113 ; result of ditto, 116; bearing of the result on the em- ployment of building materials, 116. Sand, importance of, as an ingredient of mortars, 53 ; proportion of, for mortar, 67 ; proportion for hydraulic limes, 69 ; described, 63; of different rocks, 53 ; classes of, 64 ; quality of, 55 ; prepara- tion of, 55. Scagliola, 111. Scoriae described, 61 ; analysis of, 62 ; use of, for cement, 62 ; effect of the mix- ture of with cement,. 125. Scott's cement, properties of, 124 ; use of, for huts, &c., at Aldershot, 127 ; value of, 125 ; difference between Coignet's and Scott's systems, 126. Sea salt, presence of nitre in, 115. Silica, its influence on the setting of hydraulic limes, 22. Silicate of alumina, its importance as an element of hydraulic limes, 19. Slacking limes, 46 ; increase in bulk by, 48 : method of slacking hydraulic i,]£^-, 47; object of, 46; Roman metliod, 46 ; method of slacking hy- draulic limes in London, 51. Slag described, 61; analysis of, 62; use of, for cement, 62. Smeaton's expeiiments on hydi-aulic limes, 4. Smeaton's method of slacking hydi'aulic limes, 48. Specific gravity of pure lime, 8. Stone, artificial, 77, 128. Stones, cement, described, 81 ; analysis of, 80 ; specific gi-avity of, 83. Stuccos described, 108; colouring, 109; Italian method of using, 108 ; polishing, 110; uses of, 107. Sulphate of lime, 98; calcination of, 99; method of procuring, 99 ; where found, 97, see also Gypsum, Tables of ingredients of moilars for dif- ferent purposes, 65. Tlienard's mastic. 95. Trass described, 59. 136 INDEX. Treussart's experiments on hydrate of lime, 11, Tj-eussart's experiments on the composi- tion of hydi-aulic limes, 17. Treussart's experiments on the use of alkalies with artificial hydraulic limes, 44. Tieussart on the change of colour of limestones during burning, 27. Vauban's mastic, 96. Vicat, beton used by, for the bridge )f Souillac, 77 ; classification of the ma- terials used for hydraulic cements, 63 ; experiments on the cement obtained from bricks, 56; experiments on hy- draulic limes, 7 ; experiments on mag- nesia as a constituent of hydi'aulic limes, 18; method of slacking n3'dran- lic limes recommended hy, 48 ; tables ot materials for mortars, 65 Virgin sand, 54. Vitruvius, his value as an authority, 3. Walls, saltpetreing of, 112; inquiry into the cause of, 113 ; result, 116; practical bearing of the result on the employ- ment of building materials, 116. Walls, use of concrete for backing river and quay, 127. Water, absorption of lime by, 52 ; propor- tion of, for mortar, 69 ; quality of, for moitar, 70. Water limes, see Hydraulic Limes Westmacott's cement, 130. Wood as fuel for burning limestones, 29, Wood cinders, use of. for cement, 68. THE END. PRINTtD BY WILLIAM CLOWES AKD SONS, LlAlITED, LONDON AND BECCLES. 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I. contains a complete External Survey of the following buildings with detail drawings to a large scale:— THE TOWN HALL, LIVERPOOL, 7 PLATES— THE PALACE OF IHE PETIT TRIANON, VERSAILLES, 5 PLATES — THE PALACE OF THE GRAND TRIANON, VERSAILLES, 4 PLATES— THE CUSTOM HOUSE, DUBLIN, 4 PLATES — THE ORANGERY, KENSINGTON PALACE, 3 PLATES— THE SENATE HOUSE, CAMBRIDGE, 3 PLATES — THE HOUSE OF PROVIDENCE, Dingle Lane, Liverpool, i Plate — Lodge to the House of Provi- dence, I PLATE— Main Doorway under Colonnade, St. George's Hall, Liverpool, I Plate— Jacobean Oak Chij^iney piece, Hall-i'-th'-Wood Museum, Bolton, i Plate. VOL. II. contains a complete External Survey of the following buildings, with detail drawings to a large scale:— Bank OF ENGLAND, CASTLE STRE -.T, LIVERPOOL, 3 PLATES— BRONZE Internal Doors, St George's Hall, Liverpool, i Plate— St. Paul's Church, Liverpool, 5 plates— the Queen Anne Block, Greenwich Palace, 8 Plates— MORDEN College, i^lackheath, 7 plates— The University Library, Cambridge, 3 Plates— The Screen in the chapel, Lincoln College, O.xford, 2 plates— The palace of the Peiit Trianon, Versailles, Courtyard Details, i Plate— Palazzo Bevilacqua, Verona, i Plate— Porta Nuova, Verona, 3 plates— Speke Hall, Lancashire, 6 Plates— Port.\ Palio, verona, 4 Plates. \]ust Published. MEASURING AND VALUING ARTIFICERS' WORK. A Students Guide containing Directions for taking Dimensions, Abstracting the same, and bringing the Quantities into Bill, with Tables of Constants for Valuation of Labour, and for the Calculation of Areas and Solidities. Originally edited by E. Dobson, Aichitect. With Additions by E. W. Tarn, M.A. Seventh Edition, Revised. Crown 8vo, cloth 7 IS "The most complete treatise on the principles of measuring and valuing artificers' work." 12 CROSBY LOCKWOOD SON'S CATALOGUE. PACKING-CASE TABLES. Showing the number of Super- ficial Feet in boxes or Packing-Cases, from six inches square and upwards. By W. Richardson, Timber Broker. Fourth Edition. Oblong 410, cloth. 3/6 Invaluable labour-saving tables." — Ironmonger, "Will save much labour and calculation." — Grocer. PAINTING. THE IMITATION of WOODS &MARBLE5. As Taught and Practised by A. R. Van der Burg and P. Van der bURG, Directors of the Rotterdam Painting Institution. Royal folio, cloth, 18^ by i2.i in. Illustrated with 24 full-size Coloured Plates; also 12 plain Plates, comprising 154 Figures. Fiftli Edition ..... Ket £i 5s^ List of Plates. I. Various Tools Requirhd for Wood Painting.— 2. 3. Walnut; Preliminary Stages of Graining and Finished Specimen. — 4. Tools Used for Marble Painting and Method of Manipulation.— 5, 6. St. Remi Marble; Earlier Operations and Finished Specimen. — 7. Methods of Sketching Different Grains, Knots, &c.— 8, 9. ash: Preliminary Stages and Finished Speci- men. — 10. Methods of Sketching Marble Grains. — h, 12. Breche Marbles : Preliminary Stages of Working and Finished Specimen.— 13. Maple ; Method of Producing the Different Grains.— 14, 15. Birds-Eye Maple; Preliminary Stages and Finished Specimen.— 16. Methods of sketching the Different Species of White Marble.— 17, 18. White Marble ; Preliminary Stages of Process and Finished Specimen —19. Mahogany; Specimens of Various Grains AND Methods of Manipulation. —20, 21. Mahogany; Earlier Stages and Finished Specimen.— 22, 23, 24. Sienna Marble; Varieties of Grain, Preliminarv Stages and Finished Specimen —25, 26, 27. Juniper Wood; Methods of Pro- ducing Grain, &c. ; Preliminary Stages and Finished Specimen.— 28, 29, 30. Vert de Mer Marble; Varieties of Gr\in and Methods of Working, Unfinished- and Finished Specimens.— 31, 32, 33. Oak ; Varieties of Grain, Tools Employed AND Methods of Manipulation, Preliminary Stages and Finished Specimen.— 34. 35, 36. Waulsort Marble; Varieties of Grain, Unfinished and Finished specimen. " Those who desire to attain skill In the art of painting woods and marble will find advantage, in consulting this book. . . , Some of the Working Men's Clubs should give their young men tie opportunity to study it."— Builder. " Students and novices are fortunate who are able to become the possessors of so noble » work."— 77t« Architea. PAINTING POPULARLY EXPLAINED. By Thomas John Gullick, Painter, and John Timbs, F.S.A. Including Fresco, Oil, Mosaic, Water Colour, Water-Glass, Tempera, Encaustic, Miniature,. Painting on Ivory, Vellum, Pottery, Enamel, Glass, &c. Sixth Edition. Crown 8vo, cloth 5/Q *** Adopted as a Prize Book at South Kensington. " Much may be learned, even by those who fancy they do not require to be taught, from the careful perusal of this unpretending but comprehensive treatise." — Art yoicr}ial. PLASTERING. A Practical Compendium of Plain and Orna- mental Plaster Work. By W. Kemp. Crown 8vo, cloth . . . 2/Q PLUMBING. STEAM AND HOT WATER HEATING. A Modern Work for the Plumber, the Heating Engineer, the Architect, and the Builder. By J. J. Lawler. With 284 Illustrations. 4to, cloth. Net Q.AlQ PLUMBING : A Text-Book to the Practice of the Art or Craft of the Plumber. With Chapters upon House Drainage and Ventilation. By Wm. Paton Buchan. Ninth Edition, with 512 Illustrations. Crown 8vo cloth 3/6 " A text-book which may be safely put into the hands ot every young plumber, and Avhich will al-so be found useful bj' architects and medical professors." — E^iilder. PORTLAND CEMENT FOR U5ERS. By the late Henry Faija, M.Inst.C.E. Fifth Edition. Revised and Enlarged by D. B. Butler, A. M.Inst. C.E. Crown 8vo, cloth 3/0 ARCHITECTURE, BUILDING, DECORATIVE ARTS, &-^c. 13 -QUANTITIES AND MEASUREMENTS. In Bricklayers', Masons', Plasterers', Plumbers', Painters', Paperhangers', Gilders', Smiths', Carpenters' and Joiners' Work. By A. C. Beaton, Surveyor. Crown 8vo, cloth 1/6 *' This book is indispensable to builders and their quantity clerks." — Ejiolish Mccha?iic. REINFORCED CONCRETE. A Handbook for Architects, Engineers and Contractors. By F. D. Warren, Massachusetts Institute of Technology, with Illustrations, 271 pages. Crown 8vo, cloth. Net 1 0/6 Extract from Preface. The book is divided into four parts. Part I. gives a general but concise r^st(]jie oi the subject from a practical standpoint, bringing out some of the difficulties met with in practice and suggesting remedies. Under Part II. is compiled a series of tests justifying the use of various constants and co-efficients in preparing the tables under Part III. Part III. contains a series of Tables from which it is hoped the designer may obtain all necessary information to meet the more coimnon cases in practice. Part IV. treats of the design of trussed roofs frona a practical standpoint. REINFORCED CONCRETE DESIGN. A Graphical Hand- book by John Hawkesworth, C.E. , consisting of a series of Plates showing graphically, by means of plotted curves, the required design for Slabs, Beams and Columns, under various conditions of external loading, together with practical examples explaining the method of using each Plate. With an Appendix containing the requirements of the Building Code of New York City in regard to Reinforced Concrete. 64 Pages. 15 full page Plates. 4to, cloth ISlet 1 2/0 List oi-" Plates.— I. V^alues of Constant (K) for Determining Resisting Moments— II. & III. design of Slabs Under various Conditions (JE Design and Loading— IV. spacing of Square Bars Required to Obtain a Given Area of Metal Cross Section per Foot of Width— V. External Bending Moment in Footing Slabs, due to Superimposed Column of Loads— VI. & vil. Resisting Moment per Inch of Width for Various Depths of Beams or Slabs— VIII. & villa. Conversion v>v Area of Metal Cross Section, expressed in Square Inches per Foot of width, into Total Areas for any Given AVidth, and Showing the Number of Square Bars Required— IX. Location of the Neutral Axis— X. SHE.4.RING Resistance of Various Combinations of Concrete and Steel— XI. Square Colu.mns Designed in accordance avith the New York building Code— XII. & Xlla. Rectangular Columns with Various Unit stresses, and Round Rods Required for a Given Area of Metal Cross Section— XIII. Hooped Columns with Six Longitudinals— XIV. Hooped Columns with Eight Longitudin.als— XV. Complete De:sign of a Reinforced Concrete Structure. APPENDIX. — Preliminary Hypotheses — Rectangular Members under Transverse Loading— T-Beams, with Neutral Axis below the Bottom of the SLAB— Members Subjected to Direct Co.mpression— Hooped Colu.mns— Regul.a- TIONS of the new YORK BUILDING CODE. REINFORCED CONCRETE DIAGRAMS for the Calculation of Girders, Slabs and Columns in Reinforced Concrete. By G. S. Coleman, A.M.Inst.C.E. [In the Press. ROOF CARPENTRY. Practical Lessons in the Framing of Wood Roofs. For the use of Working Carpenters. By Geo. Collings. Crown 8vo, cloth 2/0 SANITARY WORK IN SMALL TOWNS AND VILLAGES. By Charles Slagg, A.M.Inst.C.E. Third Edition, Enlarged. Crown 8vo, cloth 3/0 " There is a great deal of work required to be done in the smaller towns and villages aud this little volume will help those who are wilHng to do it." — Builder. SAW MILLS. Their Arrangement and Management, and the Economical Conversijn of Timber. By M. Powis Bale, M.Inst.C.E. Third Edition, Revised. Crown 8vo, cloth 10/6 " The administration of a large sawing establishment I discussed, and the subject examined from a financial standpoint. Hence the size, shape, order, an disposition of saw mills and the like are gone into in detail, and the course of the timber Is traced from its reception to Its delivery in its converted state. We could not desire a more complete or practical treatise."— iff Mt/i^rr. CROSBY LOCK WOOD SON'S CATALOGUE, SEWAGE, PURIFICATION OF: being a Brief Account of the Scientific Principles of Sewage Purification, and their Practical AppHca- tion. By Sidney Barwise, M.D. (Lond.), B.Sc, M.R.C.S., D.P.H. (Camb.), Fellow of the Sanitary Institute, Medical Officer of Health to the Derbyshire County Council. Second Edition, Revised and Enlarged, with an Appendix on the Analysis of Sewage and Sewage Effluents. With numerous Illustrations and Diagrams. Demy 8vo, cloth .... JVet 10/6 Summary of Contents : — Sewage : its Nature and Composition —The Chemistry of Sewage — Varieties of Sewage and the Changes it Undergoes— River Pollution and its Effects — The Land Treatment of Sewage— Precipi- tation, Precipitants, and Tanks— The Liquefaction of Sewage — Principles INVOLVED IN the OXIDATION OF SEWAGE — ARTIFICIAL PROCESSES OF PURIFICATIOM— Automatic Distributors and special Filters — Particulars of Sewerage and Sewage Disposal Schemes required by Local Government Board— Useful 1L>XXX—Appe7idix : THE APPARATUS REQUIRED FOR SEWAGE ANALYSIS — STANDARD Solutions used in the Method of Sewage analysis— Tables : Estimation of Ammonia —Nitrogen as Nitrates — Incubator Test, Oxygen Absorbed— To Convert Grains per Gallon to Parts per 100,000. SHORING, and its Application. By G, H.Blagrove. Crown 8vo., cloth 1/6 SPECIFICATIONS IN DETAIL. By Frank W. Macey, Architect, Author of *' Conditions of Contract." Second Edition, Revised and Enlarged, containing 644 pp., and 2,000 Illustrations. Ro^^al 8vo, cloth ^et 21/0 General Notes— Specification of Works and List of General Con- ditions-Preliminary Items (including Shoring and House Breaker)— Drainage (including Rain-water Well and Reports)— Excavator (including Concrete Floors, Roofs, Stairs and Walls) — Pavior— Bricklayer (includ- ing Flintwork, River and other Walling. Spring-water wells, Storagh Tanks, fountains, Filters, Terra Cotta and Faience) — Mason— Carpenter, Joiner and Ironmonger (including Fencing and Ptlin^;)— smith and Founder (INCLUDING Heating, Ftre Hydrants, Stable and Cow-house FiTTiNr.s— (Slater (INCLUDING Slate Masoni — Tiler — Stone Tiler — Shingler — Thatcher- Plumber (INCLUDING Hot-water work) — Zincworker — Coppersmith — Plasterer — Gasfitter — Bellhanger —Glazier — Painter — Paperhanger — General Repairs and alterations —Ventilation— Road-making — Electric Light— index. "We strongly advise every student to purchase the volume and carefully study it, w^hile to the older practitioner we w^ould say, have it by you as a most useful work of reference." — Architecturat Association Notes. SPECIFICATIONS FOR PRACTICAL ARCHITECTURE. A Guide to the Architect, Engineer, Surveyor, and Builder. Upon the Basis of the Work by A. Bartholomew, Revised, by F. Rogers. 8vo, cloth 1 5/O One of the books with which every young architect must be equipped."— A rchtiect. STEAM AND HOT WATER HEATING AND VENTILA= TION. A Modern Work on Steam and Hot Water Heating and Ventilation, with Descriptions and Data of all Materials and Appliances used in the Construction of such Apparatus, Rules, Tables, &c. By A. G. King. 400 pages, over 300 illustrations. Demy 8vo., cloth [JustP^ blished. Net 1 2/6 Introduction — Heat — Evolution of Artificial Heating Apparatus — Boiler Surface-^, and Settings— The Chimney Flue— Pipe and Fittings— Valves- Forms OF Radiating surfaces— Locating of kadiaiing Surfaces— Estimating Radiation— Steam-heating Apparatus — Exhaust-Steam Heating— Hot- water Heating — Pressure Systems of hot water Work— hot-Water Appliances- Greenhouse Heating — Vacuum Vapour and Vacuum Exhaust Heating — Miscellaneousheating— Radiator and Pipe Connections-Venti lation— Mechan- ical VEN riLATION AND HOT-BLAST HEATING— STEAM APPLIANCES— DISTRICT HEATING — ^JPE AND BOILER COVERING — TEMPERATURE REGULATION AND HEAT CONTROL — BUSINESS METHODS— MISCELLANEOUS— RULES, TABLES AND USEFUL INFORMATION. SUPERFICIAL MEASUREMENT. Tables calculated from I to 200 inches in length, by i to 108 inches in breadth. A Guide for the use cf Architects, Surveyors, Engineers, Timber Merchants, Builders, &c. By J. Hawkings. Fifth Edition. Crown 8vo, cloth .... 3/6 "These tables will be found of great assistance to all who require to make calculations of superficial measurement."— En/^-tish Mechatiic. ARCHITECTURE, BUILDING, DECORATIVE ARTS, <^c, 15 TECHNICAL GUIDE, MEASURER, AND ESTIMATOR. For Builders and Surveyors. Containing Technical Directions for Measuring Work in all the Building Trades, Complete Specifications for Houses, Roads, and Drains, and an Easy Method of Estimating the parts of a Building collectively. By A. C. Beaton. Tenth Edition. Waistcoat-pocket size. 1 /6 " No builder, architect, surveyor, or valuer should be without his ' Beaton.' " — Building- News. TIMBER IMPORTER'S, TIMBER MERCHANT'S, AND BUILDER'5 STANDARD GUIDE. By R. E. Grandy. Grown 8vo, cloth 2/0 TIMBER MERCHANT'S and BUILDER'S COMPANION. Containing New and Copious Tables of the Reduced Weight and Measure- ment of Deals and Battens, of all sizes, and other Useful Tables for the use of Timber Merchants and Builders. By William Dowsing. Fifth Edition, Revised and Corrected. Crown 8vo, cloth 3/0 '•We are glad to see these admirable tables, which for correctness and simplicity of arrangement leave nothing to be desired." — Timber Trades yournal, TIMBER MERCHANT. Being a Practical Guide for the Use of Building Contractors, Surveyors, Builders, &c , comprising useful Tables for all purposes connected with the Timber Trade, Marks of Wood, Essay on the Strength of Timber, Remarks on the Growth of Timber, &c. By W. Richardson. Second Edition. Fcap. 8vo, cloth .... 3/6 VENTILATION. A Text-Book to the Practice of the Art of Ventilating Buildings. By W. P. Buchan. With 170 illustrations. Crown 8vo, cloth 3/6 VENTILATION, See Steam and Hot Water Heating and Ventilation." VILLA ARCHITECTURE. A Handy Book containing a Series of Designs for Villa Residences in various Styles. With Outline Specifications and Estimates. By C. Wickes, Architect, Author of "The Spires and Towers of England," &c. 61 Plates, 410, half-morocco, gilt edges £1 Us. 6d. WATER AND ITS PURIFICATION. A Handbook for the Use of Local Authorities, Sanitary Officers, and others interested in Water Supply. By S. Rideal, D.Sc. Lond., F.I.C. Second Edition, Revised, with Additions, including numerous Illustrations and Tables. Large Crown 8vo, cloth Net 9/0 W^ATER SUPPLY OF CITIE5 AND TOV^NS. By William Humber, A.M. Inst. C.E., and M. Inst. M.E., Author of "Cast and Wrought Iron Bridge Construction," &c., &c. Illustrated with 50 Double Plates, i Single Plate, Coloured Frontispiece, and upwards of 250 Woodcuts, and containing 400 pp. of Text. Imperial 4to, elegantly and substantially half-bound in morocco .... iVI?^ £6 6s. I. Historical sketch of some of the means that have been adopted for THE Supply of w ater to Cities and Towns— II. Water and the Foreign Matter USUALLY Associated with it— III. Rainfall and Evaporation— IV. Springs and THE Water-bearing Formations of Various Districts— v. measurement and Estimation of the Flow of vvater— VI. On the selection of the Source of Supply— VII. wells— VIII. Reservoirs— IX. The Purification of water— X, Pumps —XI. PUMPING Machinery— XII. Condiuts- XIII. Distribution of Water — XIV. Meters, Service Pipes, and House Fittings— XV. the Law and Economy of Water works— xvi. Constant and intermittent Supply— XVII. Description of plates— Appendices, giving Tables of Rates of Supply, Velocities, &c., &c., together with Specifications of Several Works Illustrated, among which will be FOUND: ABERDEEN, BIDEFORD, CANTERBURY, DUNDEE, HALIFAX, LAMBETH, ROTHERHAM, AND OTHERS. " The most sj'steniatic and valuable work upon water supply hitherto produced in English, or in any other language. Mr. Huniber's work is characterised almost throughout by an ex- haustiveuess much more distinctive of French and German than of English technical treatises." — Engineer. CROSBY LOCK WOOD cfv SON'S CATALOGUE. WATER SUPPLY OF TOWNS AND THE CONSTRUC= TION OF WATER = WORKS. A Practical Treatise for the use of Engineers and Students of Engineering. By W. K. Burton, A.M.Inst. C.E., Consulting Engineer to the Tokyo Waterworks. Third Edition, Revised. Edited by Allan Greenwell, F.G.S., A.M. Inst. C.E. With numerous Plates and Illustrations. Super-royal 8vo, buckram. [J ^ist published £1 5s, I. Introductory— II. Different qualitif.s of Water— hi. Oiwntity of AVater to be Provided— IV. On Ascertaining whether a Prop<)si:d Source of SUPPLY IS Sufficient— V. On Estimating the Stora(;e Capacity Ri:oi:ired to be Provided— VI. Classification of Waterworks— VII. Impounding Reservoirs— VIII. Earthwork Dams— IX. Masonry Dams— X. The Purification of water— XI. •Settling Reservoirs— Xll. Sand Filtration— XIII. Purification of Water by Action OF Iron, Softening of water by Action of Lime, Natural Fii/iration— XIV. service or Clean Water Reservoirs— Water Towers— Stand pipes— XV The Connection of Settling Reservoirs, Filter Beds, and Service Reservoir.s —XVI. PUMPING Machinery— XVII. Flow of Water in Conduits— Pipes and Open Channels — XVIII. Distributing Systems — XIX. Special Provisions for the Extinction of Fires— XX. Pipes for Waterworks— XXI. Prevention of Waste of Water— XXII. Various Appliances used in Connection with Waterworks. Appendix 1. By Prof. John Milne, F.R.S.— Considerations Concerning the Probable Effects of Earthquakes on Waterworks and the special Pre- cautions to be taken in Earthquake Countries. Appendix II. By john De Rijke, C.E. On Sand Dunes and Dune Sands as a Source of water supply. •'We congratulate the author upon the practical conimonsense showii in the preparation of this work. . . . The plates and diagrams have evidently been prepared with j^reat care, and cannot fail to be of jjreat assistance to the student.'" — Builder. WATER SUPPLY, RURAL. ^ A Practical Handbook on the Supply of Water and Construction of Waterworks for Small Country Districts. By Allan Greenwkll, A.M.I.C.E., and W. T. Curry, A.M.I.C.E. Revised Edition. Crown 8vo, cloth -5/0 WATER ENQINEERINQ. A Practical Treatise on the Measurement, Storage, Conveyance, and Utilisation of Water for the Supply of Towns. By C. Slagg, A.M.Inst.C.E 7/6 WOOD-CARVINQ FOR AMATEUR5. With Hints on Design. By A Lady. With lo Plates. New and Cheaper Edition. Crown 8vo, in emblematic wrapper 2/0 " The handicraft of the wood-carver, so well as a book can impart It, may be learnt from • A X^dy's' publication." — Athenteum. WOODWORKING MACHINERY. Its Rise, Progress, and Construction. With Hints on the Management of Saw Mills and the Economical Conversion of Timber. Illustrated with Examples of Recent Designs by leading English, French, and American Engineers. By M. Powis Bale, M.Inst.C.E., M.I.Mech.E. Second Edition, Revised, with large Additions, large crown 8vo, 440 pp., cloth 9/0 " Mr. Bale Is evidently an expert on the subject, and he has collected so much information that his book is all-sufficient for builders and others engaged in the conversion of timber."— bRADBURY, AGNEW, & CO. LD., LONDON AND TONBRIDGE. (429-6-08.) WEALE'S SCIENTIFIC d TECHNICAL SERIES. MATHEMATICS, ARITHMETIC, &c. Geometry, Descriptive. J. F. Heather . . . 2/- Practical Plane Geometry. J. F. Heather. . . 2/- Analytical Geometry. J. Hann & J. R. Young . . 2/- Geometry. Part I. (Euclid, Bks. I.— III.) H. Law 1/6 Part II. (Euclid, Books IV., V., YI., XL, XIL). H. Law 1/6 Geometry, in i vol. (Euclid's Elements) . . . . 2/6 Plane Trigonometry. J. Hank . . . .1/6 Spherical Trigonometry. J. Hann . . . i/- The above 2 vols. , bound together . . . .2/6 Differential Calculus. 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