■4 mBs M ^ UCSB LVBRKRV P.ng^on SlwLby ///ff/ff/f/ // ■ yr;>rA'^,M//^J^y 4" <■ yf^-'^^j;y^M^'^"^>-^^^- >^. V-/v^7. PRACTICAL MASONRY, BRICKLAYING, AND PLASTERING, BOTH PLAIN AND ORNAMENTAL; CONTAINING A NEW AND COMPLETE SYSTEM OF LINES FOK STONE-CUTTING; FOR THE USE OF WORKMEN ; WITH A.V AMPLE DETAIL OF THE THEORY AND PRACTICE OF CONSTRUCTING ARCHES. DOMES. GROINS, NICHES, STAIRS, COLUMNS, &c. . BOND, FOUXDATIOXS, WALLS, BRIDGES, TUNNELS, LIGHT-HOUSES, &c. OVENS, FURNACES, &c. THE FORMATION OF MORTARS AND CEMENTS; IXCLUDINO, ALSO, P K A C T I C A L TREATISES ON SLATING, PLUMBING, GLAZING, &c. &c. AND A I'LLL DESCRIPTION OF THE VARIOUS MATERIALS EMPLOYED IN ALL THESE ARTS, ILIUSTKATED BY NLMKRIH^i F.NGli WINGS. UY AKTIST^ OF HR'^T-RATE TALENT. LONDON: THOMAS K E L L ^'. P .\ T E R N S T E R R O W. MDCCCXLI. London: J. Rider. Priater, 14, Bartholomew Close. PREFACE. IN submitting the present Volume to the Public, we have to offer our grateful acknowledgments for the very favourable reception which the previous work on Carpentry and Joinery* has met with, and we feel much gratified in having been, in an eminent degree, successful in our endeavours to unfold and elucidate the scientific Principles and Practical Application of those Arts which have the object of employing Wood in the construction of Buildings : we now proceed to deve- lope, in a similar manner, the scientific Frinciples and Practice of the Arts of Con- struction, using other materials, and particularly the important Arts of Masonry and Bricklaying, and also the Ornamental Art of Plastering. Our plan consists in separately treating the Arts of Construction, and elucidat- ing them by grouping together those principal branches which have a natural relation to each other, and which require similar operations, and in which a work- man in the one always has an advantage in knowing the principles of the others ; and we are the more powerfully encouraged to proceed in it, by the knowledge that this plan is as new as it will be found useful, and we trust the Work itself will bear the palm, as well for originality and beauty, as for its practical utility. The nature of our Work will be more fully understood from the following short sketch of its plan. First, we begin with a Treatise on Masonry, in which is given a complete System of Lines for Stone Cutting, in all its branches ; as for instance. Arches, Niches, Domes, Plain and Gothic Groins, Mouldings, &c. Next we treat of the qualities of Building Stones, the nature and composition of * The PRACTICAL CARPENTRY, JOINERY, and CABINET MAKING ; being a new and com- plete System of Lines, for the Use of Workmen; founded on accurate Geometrical and Mechanical Prin- ciples, with their application in Carpentry, — to Roots, Domes, Centring, &c. ; in Joinery, — to Stairs, Hand-rails, Soffits, Niches, &c. ; and in Cabinet-Making, to Furniture, both Plain and Ornamental, fully and clearly explained. This useful and scientific Work is completed in Thirty Numbers, Quarto, Price One Shilling each, or in Six Parts at Five Shillings each, containing Ninety Plates, and upwards of Two Hundred Di.igrams, exe- cuted by Artists of the first-rate Talent. Printed for T. Kelly, price only 30s. in boards. IV PREFACE. Mortars and Cements, and the principles of constructing Foundations, Walls, Bridges, Domes, Tunnels, Light-houses, &c. Secondly, a Treatise on Bricklaying is introduced, showing the nature and qualities of Bricks, Tiles, &c. The Theory of Brick-bond and the construc- tion of Arches, Groins, &c. ; also the best methods of building Ovens, Furnaces, and Fire-places in general, &c. Thirdly, a Treatise on Plastering, describing the composition of the mate- rials, and their application in both Plain and Ornamental work, with specimens of Ornaments, in the various styles that have been adopted in that department at various periods. Fourthly, of Slating, in which the various qualities of Slates are fully ex- plained, and also the most perfect method of applying them as a covering for buildings. Fifthly, of Plumbing, Painting, and Glazing, with a full description of the qualities of the materials, and the most approved methods of applying them : the whole forming a valuable mass of practical information peculiarly calculated to direct and assist the workmen in all these branches of the Building Art. A Glossary of the peculiar Technical Terms applicable to each Department, is placed at the close of each division, in which an explanation is given of those objects which require it, and references to where they are treated of in the body of the work, by which means a greater facility will be obtained in consulting the AVork. The examples in the Plates are engraved in the best style, and are chiefly selected from the most approved works, already executed by the following dis- tinguished Architects and Civil Engineers, viz. Messrs. Wyattville, Soane, Rennie, Telford, Brunei, Perronet, &c. &c., as we are persuaded that such designs will be found superior to any of our own. Our sole object and endeavours in the pro- secution of these Works, have been to combine Theory with actual Practice, and to render both familiar and easy. CONTENTS. BOOK I. — MASONRY. PAGE Intkoduction. — Masonry practically considered. The application of the Art in ancient times, compared with the modern use I Chapter I. — Of the Description of Arches. Parabolic Arch ; Elliptical Arch ; method of drawing the joints ; to draw a tangent to a semi-elliptic Arch, the axis major being horizontal. Of the Cyclograph S Chapter IL — Stone Cutting. To form a plane surface, 4. Winding Surfaces, 5. Angles formed by plane surfaces, 5. Of the construction of semi-circular right arch, 6. Of the forms pro- duced by the intersection of Arches, 6. Elliptical Arch, with splayed jambs, 7. To find the joints of an oblique Arch, 7. To find the joints of an oblique circular Arch, 8. Oblique Arch, 9. A semi-circular arched Passage, between two semi-circular arched Vaults, 10. An Archway revealed and splayed, &c -. 11 Of spherical Vaults, or Domes and Niches 12 Of ribbed Groined Vaults. Raking Mouldings 13 Of the Materials employed in Masonry 14 Of Mortars and Cements 21 Chapter III. — Of the Construction of Foundations 30 Chapter IV. — Of the Construction of Walls 33 Of Wharf, Dock, and Revetment Walls 35 Chapter V. — Of the Construction of Bridges, &c 38 Theory of Bridges 42 Illustration of the Principles of Bridges 47 Chapter VI. — Of the Construction of Domes, Groins, and Spires 31 Theory of Domes 54 Of Groined Vaulting 55 Of the Construction of Spires 58 Chapter VII. — Of the Construction of Light-houses 59 The Eddystone Light-house 60 The Bell Rock Light-house 61 Chapter VIII. — Ornamental Masonry 63 Appendix to Ornamental Masonry 77 Description of Plates 77 Chapter IX. — Valuation of Masons' Work 82 Explanation of Terms, and Description of Tools used in Masonry 83 BOOK II.— BRICKLAYING. Introduction. — Nature and Properties of various kinds of Bricks 88 Chapter I. — On the Nature and Properties of Brick-bond > 96 On English and Flemish Bond 96 Chapter II. — On the Construction of Walls 100 Choice of Materials for the Foundations of Walls 101 Prison Walls 103 Chapter III. — On the Construction of Arches for Cylindrical Vaults 104 Chapter IV. — On the Construction of Vaults for Warehouses and Cellars 108 Introductory Principles and Observations 108 The Principles of Brick Vaulting, as in common Groins Ill The Principles of Brick Vaulting, as in the London Docks 112 The Principles of Brick Vaulting, as in St. Catherine's Docks 113 b VI CONTENTS. PACE Chapter IV. — The Principles of Brick Vaulting, as under the Hall of Christ's Hospital 116 Principles of Brick Vaulting, similar to that described by Mr. Tappen 119 Chapter V. — On the Construction of Brick Niches 120 On the Construction of Tunnels and Drains 121 Description of the Tunnel at the Regent's Canal 123 Tunnel under the Thames from Rotherhithe to Wapping 125 Various other Designs for the sections of Tunnels, Sewers, Culverts, and Drains .. 129 Chapter VII. — On the Construction of Ovens, Boiler Fire-places, and of the setting of Coppers . . 131 Of Boiler Fire-places 133 On the Method of fixing a Copper Boiler for Brewing 136 Chapter VIII. — Setting Retorts, as particularly applicable to Gas Works 137 Method of setting a Bench of five Retorts 139 On Fire Bricks, &c 1 •! 1 Coke Oven Plan 141 Improved Method of setting five Retors in an Oven 142 Safety Plugs 144 Retort Furnaces 145 Chimnies for Gas Works 147 Chapter IX. — On Furnaces for the Fusion of Metal 149 On the Proportions of Air Furnaces . . . , 156 On the Nature and Properties of Reverberating Furnaces 158 On the Method of Constructing a Watch Dial Plate and Enameler's Furnace 159 On the Properties and Construction of Blast Furnaces 160 On the Construction of Fire-places for Warming Rooms in Dwelling Houses 163 Chapter X. — An Explanation of the Terms and Description of Tools used in Bricklaying 166 BOOK III.— PLASTERING. Introduction 171 Chapter I. — Of the Gothic style of Ornament 174 Of the Elizabethan style of Ornament 175 Of the old English style of Ornament 175 Of the Roman style of Ornament 176 Of the Grecian style of Ornament 176 Of the French style of Ornament , 177 Chapter II. — Of the Materials and Compositions used in Internal Finishing 178 Manner of forming Columns or Pilasters in Scagliola 183 Chapter III. — Of External Compositions 184 Roman Cement 184 Terra Cotta, and various Methods of using it 185 Mastic ; manner of using it for various purposes 187 Chapter IV. — Operations and Modes of performing them - ' 189 Plain and Ornamental Cornices 192 Plain Straight Cornices 1 92 Circular and Ellintical Cornices 193 • * Mouldings belonging to Groined Ceilings, commonly called Ribs 194 Intersections which terminate either on Corbels, or on the Capitals of Columns .... 1 95 Enriched or Ornamented Cornices 196 Grecian Cornices 196 Roman Cornices 196 Gothic Cornices • • 197 CONTENTS. Vll PACB Chapter IV. — French Cornices 197 Working Ornament by hand 197 Modelling 198 Moulding Ornaments 199 Moulding in Plaster 20t) Casting in Plaster ~00 Fixing Ornaments 200 Chapter V. — Description of the Plates of Ornament belonging to Plastering 201 Chapter VI. — An Explanation of the Terms and Description of the Tools used in Plastering 203 BOOK IV.— SLATING. Description of Slates and their Qualities 205 Description of the various parts of Slates 206 Various Methods of combining them considered 207 The best Method of fastening and laying them 208 Explanation of the Principles and Practice of Slating 212 The kind of Slates to be used 214. Comparison in weight of the sundry Coverings employed on Roofs 216 The Slaters' Tools 217 Valuation of Slaters' Work 217 Explanation of the Terms used in Slating 218 BOOK v.— PLUMBING, PAINTING, AND GLAZING. Chapter I. — Plumbery or Plumbing 219 On the Properties of Lead 219 On casting Sheet Lead 219 On casting Lead Pipes 220 Laying of Sheet Lead 221 On various Pumps 222 Terms used in Plumbing, and Description of Tools 223 CHAriER II. — House Painting 224 The economical application of Paint 224 Nature and Properties of White Lead 224 Of Linseed Oil and Spirits of Turpentine 225 Of various Dryers < 235 Putty 226 The best Modes of executing Painting 226 Of Painting Stucco 227 On the Colours used in Painting 228 On Painting in Distemper 228 Graining 2?9 Chapter III. — Glazikg. On the Antiquity of Glass 229 The nature of Modern Glazing ^ •• . 229 Glazing in Lead Work 230 On the various kinds of Glass used in Glazing 230 On valuing Glaziers' Work * 231 On the Instruments for Cutting Glass 2 J 1 Charges for Cleaning Windows 232 On the mode of Measuring Glaziers' Work 232 DIRECTIONS TO THE BINDER FOR PLACING THE PLATES. N B. The same Plates being referred to from different Pages, we recommend placing the whole together at the end of the Volume ; but where this method is not adopted, the Plates will be most convenient opposite the Pages, as below. MASONRY. Plates Page I. Description of Arches ~ II. Cyclograph 3 III. Stone-Cutting 4 IV. Construction of Arches, &c 6 V. Construction of Arches, &c 7 VI. Construction of Arches, S;c 7 VII. Construction of Arches, &c 8 VIII. Construction of Arches, &c. .... 10 rX. Construction of Arches, &c 10 X. Construction of Arches, &c 11 XI. Spherical Vaults or Domes .... 12 XII. Ribbed Groins 13 XIII. Raking Mouldings 14 XIV. Antient Walls 33 XV. Wharf, Dock, and Sea Walls . . 36 XVI. Bridges 41 XVII. London Bridge 51 XVIII. Bridge of NeuiUy 48 XIX. Bridge across the Severn 49 XX. Bridge over the Menai Strait . . 50 XXI. Domes 51 ■ XXII. Construction of Spires 58 XXIII. Light-House 60 XXIV. King's College Chapel,Cambridge 57 XXV. Mouldings 76 XXVI. Balustrades and Parapet 77 XXVII. Chimney Shafts 78 XXVIII. Gothic Arch and Chimney Shaft 79 XXIX. Windows 80 XXIX. a. Design for a Grecian Chimney- Piece 81 XXIX. 6, Chimney Piece in the Grecian style 81 XXIX. c, Gothic Mural Monument, &c. 81 XXIX. d, Design for a Monument in the Grecian Style 82 BRICKLAYING. Plates Page XXIX. e. On Brick-bond 96 XXIX. /, Plan of Cold Bath Fields Prison 103 XXIX. g, Description of Arches 105 XXIX. h, Window and Door, with Details, &c 107 XXIX. i, Gothic Window, &c 107 XXIX. i, The Principles of Brick Vault- ing, &c Ill XXIX. /, The Principles of Ditto 112 XXIX. ffi. The Principles of Ditto .... 113 XXIX. n. The Principles of Ditto 114 XXIX, 0, The Principles of Ditto .... 116 XXIX. p, The Principles of Ditto 119 XXX. Tunnel under the Thames .... 129 XXXI. Tunnelling 129 XXXII. Tunnels, Sewers, and Drains .. 129 XXXIII. Design for Coal Oven, &c 131 XXXIV. Boiler Fire Places 133 XXXV. On fi.King Copper Boilers 136 XXXVI. Retorts 139 XXXVII. Air Furnaces for Metallurgy .. 154 XXXVIIL Blast and Air Furnaces 159 XXXIX. Fire Place and Pump 165 PLASTERING. XL. Gothic Style of Ornament .... 201 XLI. Gothic Style of Ornament 201 XLII. Elizabethan Ditto 201 XLIII. Roman Ditto 201 XLIV. French Ditto 202 XLV. Slating 212 The Publisher respectfully recommends to each Subscriber the following highly useful and necessary Addenda :— THE PRACTICAL BUILDER'S PERPETUAL PRICE-BOOK ; Being a Sequel to " THE NEW PRACTICAL M.A50NRY AND CARPENTRY," elucidating the Principles of correctly ascertaining the average Value of the differeut Artificer's Works employed in Building ; with the particular Customs of Mea. suring and Valuing in the various parts of the United Kingdom ; comprehending, also, the Substance of every Clause in thi the Building Act. Intended as a Key to, or Illustration of, these Works, and will be found highly useful to the Gentleman, the Surveyor, and the Architect, as well as to all Persons anywise concerned in the Art of Building. The Addenda is completed in Eleven Numbers or Two Parts, in Quarto, illustrated with suitable Plates. It is also printed sefa- rtuly, in Octaoo size,/or the convenience qftlte Practical Builder, Surveyor, If c, price Eight Shillings, sewed. PRACTICAL MASONRY, BRICKLAYING, &c, BOOK I. 31 AS O N R Y. INTRODUCTION. Art. 1. lYxASONRY, practically considered, is the art of shaping and uniting Stones for the various purposes of Building. It, therefore, includes the cutting or hewing of stones into the particular forms required, and the union of them by level and perpendicular joints, con- nected by the aid of cement, or by iron cramps and lead. The operations of Masonry require much practical dexterity, with some skill in Geometry and Mechanics. In treating on this subject, it will be necessary to divide it into several branches ; but first, we may notice that, though necessity was its parent, nevertheless the fluctuations of this Art have marked the rise and fall of the Empires. 2. In Egypt, Greece, and Italy, among the greater works of masonry, are included some of almost incredible magnitude, formed of materials of the most imperishable nature. These countries seem to have been favoured with every thing which could contribute to their beinc eternized ; for they abounded in the finest granites, porphyries, and marbles, which rendered their structures magnificent, independently of their size, or of peculiar contrivance in arrangement. 3. The older specimens of masonry of Britain, in point of geometrical skill and mechanical arrangement, are inferior to none : the magnificent structure at Cambridge, called King's College Chapel, is the most celebrated, and was justly styled by Lord Orford, " a work that alone will be sufficient to ennoble any age ;" and it has, from time to time, received the homage of those who are best qualified to appreciate its merits. It is to be regretted, however, that in it, as in most of the old works in this country, too little regard was given to the selection of durable materials. Modern masonry is chiefly directed to somewhat different objects ; Bridges, Docks, Light- houses, &c., works requiring an equal degree of skill, and if not productive of equal magni- ficence are infinitely superior in utility. S PRACTICAL MASONRY. CHAPTER I. OF THE DESCRIPTION OF ARCHES. 4. Arcues are of various kinds, and, generally, receive their names from the curve which is formed by the intrados or soffit line. Thus we have circular arches, eUiptical arches, and parabolic arches ; when the intrados is a circle, an ellipse, or a parabola. Sometunes they receive their names from the style of architecture, as Gothic Arches, Persian Arches, &c. and some arches have particular names, as a segment of a circular arch is called a Scheme Arch, &c. The joints of the stones in an arch are generally made perpendicular to the curve of the intrados or soffit line. 5. To describe a Parabolic Arch, the span and height of the arch being given. Method 1. — Plate I, Figures 1 and 2. — Let AB be the span: bisect AB in the point C, and draw CD perpendicular to AB. Make CD equal to the height of the arch. Produce CD to E ; making DE equal DC, join EA, EB. Divide EA into any number of equal parts, Al, A2, A3, &c. ; and, EB into the equal parts El, E2, E3, &c. Join the corresponding points 1,1; 2, 2 ; 3, 3 ; &c., and the intersections of the several lines will form the parabola required. Figure 1 is adapted to a segment, where the rise of the arch is considerable. Fig. 2 is adapted to the head of an aperture, where the radius of curvature of the arch is very great, or where the deflection of the curve from a straight line is but small. 6. Method 2. — Fig. 3. — AB and CD being as before, draw DE parallel to AB, and AE parallel to CD. Divide AC into any number of equal parts, and AE into the same number. From the points 1, 2, 3, &c., in AE, draw lines to D, intersecting perpendiculars to A, drawn from the points 1, 2, 3, &c., in AC. Through the points of intersection draw the curve AD. In the same manner draw the curve BD. 7. To determine the joints of the arch -stones, or to draw a straight line perpendicular to the curve from a given point h, (fig. 3,) as a joint. In the curve take any other point, as B, at pleasure, and join BA. Bisect Bh in e, and draw eg perpendicular to AB, intersecting the curve in the intermediate point /. Make fg equal to fe; join hg, and draw hi perpendicular to hg; then hi will be the joint required. 8. Or, draw ah parallel to AB, to meet DC in a; and make D6 equal to Da; then join h b, and draw hi perpendicular to hb, and it is the joint. Figure 1 and 3. The same methods apply to figure 2. ARCHES, &C. 3 A Practical Method of describing the Curve of an Elliptical Arch, from centres, and of drawing the joints. 9. Let AB {figure 4,) be the springing-line. Bisect AB in C, and draw CD perpendicular to AB, and make CD equal to the height or rise of the arch. Draw DE and AE, respectively parallel to AB and CD. Divide AC and AE each into three equal parts. Produce DC to g, and make Cg equal to CD. Draw lines from the points of division in AE to the point D, to intersect other lines in ef, drawn from g through the points of division in AC ; then, e and / will be points in the curve. Bisect /D by a perpendicular, meeting D^- produced in h, and join hf, intersecting AC in k. Bisect ef by a perpendicular, meeting fh in i. Draw i q parallel to AB. From i, with the radius if, describe the axe fq. Join qA, and produce g'A to meet the asc fq : join the point of meeting, and the point i intersecting AB in I. From h, with the radius hT>, describe an arc T)f; from i, with the radius if, describe an arc fe ; and from I, with the radius le, describe the arc eA. By transferring the places of the centres to the other side, the half, DB, of the semi-elliptic arc, ADB, may be described. To draw a Tangent to a Semi-elliptic Arch, the axis-major being horizontal. 10. With the radius AC, (figure 5,) and D as a centre, cross AB in the points u, v, called the focii. Let * be a point in the curve: join su and sv. Draw si, bisecting the angle usv, and st will be the joint required. In the same manner any other joint, qr, wiU be found. Or, by finding the position of the centres, and that of the lines for describing the curve, as in jig. 4, the joints may be drawn, as g'r from li, st from i. Figure 6 is a semi-circular arch, with the joints marked out. Figure 7 a semi-elliptic arch, with the joints also marked out, and the centres for drawing them as before. , The Cyclograph. 11. For drawing arcs of circles, the Cyclograph is a most useful instrument, and may also be applied, in various cases, in drawing mouldings and flat curves, for the arches of Bridges, &c. Figure 1, of the plate II, represents the instrument, which is used by inserting points, as at A and C, at the springing of the arch, and adjusting the point of the pin or pencil, which is inserted in a tube, at B, to the height of the arch or curve, then fixing the joint by means of one of the larger screws to the right-hand side of the pencil. Figure 1, No. 1, is a view of the instrument turned upon its edge, showing the tube and pencil fixed in the joint. Figure 2, exhibits the legs without the brass-work. 4i PRACTICAL MASONRY. Figure 3, No. 1, the biass-work, with the tube in the joint. No. 2, is a side view of figure 3, No. 1. Figure 4, No. 2, exhibits the joint when the pieces are separated. No. 1, and No. 3, sec- tions oi figure 4, and No. 2. Figure 5, the upper brass-plate, with a circular slit in it for the screw, which fixes the leg to move in, when the angle of the instrument is altered to adjust it, and it is by tightening the screws passing through the slit in the plate that the instrument is fixed. Figure 6 is a section of the joint and tube to a larger scale, with a steel drawing-pen inserted instead of a pencil ; it is fastened by means of a screw at the side of a tube. Figure 7 and 8 represent the screws. CHAPTER II. STONE-CUTTING. 12. Stone-cutting may be equally well done by various methods ; the most certain consists in formino- as many plane surfaces to the stone as may be necessary, in such manner that these surfaces may include the intended form, with the least waste of stone, or in the most conve- nient way for applying the moulds. Upon the plane surfaces thus prepared, the proper moulds are to be applied, and the stone worked to them. It will generally happen, that the bed of the stone will be one of the first plane surfaces, and the arrangement should always be made, so that there may be as little re-working as possible. 13. But, before we proceed to explain methods of forming stones to the particular shapes required for arches, vaults, &c., it may be remarked, that the young mason should be extremely careful to avoid making the beds of stones concave or hollow. For, if this be done in any case where the stones have to bear much pressure, they will flush, or break off in flakes at the joints and entirely disfigure the work. It is better that they should be slightly convex. In the construction of piers and columns, where perfectness of form is at least as much regarded as strength, this maxim should be carefully attended to. Nothing can be more offensive to the eye than a flushed joint, since it not only deforms, but also gives the idea of want of strength. 14. To form a perfectly Plane Surface, (see fig. 1, plate III,) the stone-cutter should com- mence by making a narrow part of it straight, with a chisel or point, along close to one edge, AB, of the stone; this narrow portion, formed to coincide with a rule or straight-edge, is called a draught. Another draught, AC, should be made along another edge, from one of the extremities, as A, of the first ; and then a third draught, BC, being made in a diagonal direc- STONE CUTTING. 5 tion, so as to meet the other two, and form a triangle; the three draughts will be all in one plane. Run a fourth draught, AD, in the direction of the other diagonal from the point A, in which the first two meet, and at the crossing to coincide with the first diagonal draught at E ; and then reduce the intermediate parts between the draughts, so that the whole of the surface /5 may coincide with the straight-edge, or be in a plane with the draughts. Sometimes two other draughts are formed along the edges, BD and DC. It enables the workman to reduce the surface to a plane, with less risk of breaking the edge of the stone within the parts required perfect ; and also to examine its accuracy by means of two parallel sticks placed along the opposite draughts, by which the smallest degree of wmding can be detected. 15. To form a regidarly Winding Surface, let draughts be formed along the edges in one plane, as for forming a plane surface, and from these draughts work the other sides so as to be square to the draught-lines; then set off A a (Jig. 2,) on the arris equal to the quantity of winding, and draw a B and a C for the draught-lines. If the lines be, cf, dg, be drawn parallel to Aa, and eh,fi, g k, parallel to AC. The draughts being cut at these lines, so that the straight-edge applies from b to h, c to i, and from d to k, and the surface be reduced so that a straight-edge applied parallel to the plane, AaB, may every where coincide with the surface, and also with the cross-draughts, then the surface will be of the form required. 16. If the side CD of the stone be shorter than AB, then the line aB {fig. 3,) must be divided into 'equal parts, and the lines be, ef, dg, drawn parallel to Ao; next divide the line CD into the same number of equal parts in h,i,k, and join eh,fi, gh, instead of drawing them parallel to AC. The draughts being sunk till the straight-edge applies from b to //, e to i, &c., and then the surface finished, so that the straight-edge will apply in a direction parallel to the plane AaB, it will be of the required form. n. Of t/ie Angles formed by Plane Surfaces. — The angle made by two planes, which meet one another in an arris, is measured or ascertained by applying a bevel in a plane perpendicular to the arris ; and if two lines be drawn at right angles to that arris, the one in the one plane, and the other in the other, the bevel being applied so that its legs are on the hues square from the arris, it will be set to the angle formed by the planes. This may be illustrated by drawing two lines, AB and CD, upon a piece of paste-board, at right angles to one another, crossing at the point E, and let the paste-board be cut half through, according to t'.ie line CD, so that it may turn upon that line as a joint, then to whatever angle AEB, (fig. 4,) the parts may be turned, the lines EA and EB will be always in the same plane. Also, a line FB, drawn from any point B, in the Une EB, to any point F, in the line EA, will be always in the same plane. From this self-evident property of planes, it is easy to determine the angle formed by any two planes, when two plans, or one plan and the section or developement of the surfaces, are given. c 6 PRACTICAL MASONRY. 18. Let ACB {fig. 5,) be the plan of part of a pvramitl, and CD the elevation of the arris, or line formed by the meeting of the planes in respect to the line CE ; CE being the hne cor- responding to the place of the arris upon the plan. Draw DE perpendicular to DC, cutting CE in the point E, and through E draw AB per- pendicular to CE. With the radius ED and centre E, cross CE in F ; and join AF and BF, then the angle AFB is the angle formed by the planes of the pyramid. In this manner the angles formed by any plane surfaces may be found from drawings. Of the Construction of a Se??ii-circular Right Arch. 19. Let ABCD {Jig. 4, plate IV,) be the plan of the arch. Divide the opening into two equal parts by the perpendicular EF ; from E, with a radius equal half the span of the arch, describe the semi-circle AFB, which is the intrados ; and, from the same point E, with tlie radius of the extrados, or back of the arch, describe the semi-circle GHI. Divide the arch GHI, of the extrados, into five equal parts, and draw the lines k o, Ip, mq, nr, to the centre E, for the joints, which will form the heads of the arch-stones ; the arch-stones being all of the same form, they may be executed without making a mould for each stone, by having the head of the arch-stone and thickness of the wall only, in the following manner : Choose a stone of sufficient length to answer for the thickness of the wall, and of breadth and depth proper for the other dimensions. Reduce the side intended for the intrados to a plane surface, on which draw the two parallel hnes ab, cd, {fig. 1,) distant from each other the space between the joints of the intrados; then square one end, as, ac to abed, and parallel to a c draw bd, at a distance equal to the thickness of the wall. Squai'e the other end of the stone, and on the head apply the mould p q m 1, {fig. 4,) so that its extremities p q may coincide with c a, (fig. 1,) when a])plied to one head, and with bd when applied to the other ; then hollow out the intrados, and cut the joints or beds according to the traces, as exhibited at figure 2. Figure 3 exhibits a stone entirely finished, and all the others are formed after the same manner ; but, instead of forming the heads on the stones themselves, a bevel, such as Shewn in fig. 4, koA, may be used with advantage. The upper part of fig. 4 represents an arch-stone, accompanied with the moulds of each side, which will explain the application more particularly ; and the middle part of figure 4 shows the arch complete, with all the stones supporting one another. Of the Forms produced by the Intersection of Arches. 20. Whatever may be the form of an arch, the figure, which will be produced by a plane cutting it in an oblique direction, may be determined by means of the method of ordinates, which we propose to describe in this place, in order that the mason may know how the curves of an arch may, in any case, be derived from one another CONSTRUCTION OF ARCHES, &C 7 Let MFL {fig. G, j^lute III,) be the section of an arch, and BADC its plan, and let it be cut by a plane perpendicular to the plan, and in any direction CA, then the form of the arch, as shown on the surface of the section, may be found thus : Take any number of points, as, /, e, d, in the curve, and from each point draw a line parallel to the direction of the arch to meet the line of section CA, as in the points 6, 5, 4. From each of these points raise a line perpendicular to CA ; and on these perpendiculars set ofF from the line CA, the height of the corresponding points in the arch above the springing-line ML. As, make EG equal to NF; ^k equal g d, &c. ; and, through the points G,K,?, A, C, draw a curve, which is the form of half the arch required, and the other half will be of the same figure. 21. The line of intersection of two arches is detennined in the same manner, when they are formed so that the intersection is in a plane : and, to make the intersection in a plane, let BD {fig. 6,) be the line of intersection, and from each of the points 1, 2, 3, in this line draw a line in the direction, or parallel to the sides, of each arch ; and make the corresponding points, a, b, c, in these arches of the same height above their respective springing-lines. The whole of the figure shows the plan and sections of a plain groin, with the joints of the stones inserted in the plan. T/ie Elliptical Arch, with Splayed Jambs. 22. To find the angles of the joints formed by the front and intrados of an Elliptical Arch, erected on splayed jambs. Figure 1, on plate V, is the plan of the Imposts, or Jambs. Figure 2, the Elevation. The plan of the impost ABCDE is the first bed; /^/«JA, the second; Imnop, the third. qrstu, the fourth ; vwxijx, the fifth : The other beds are the same in reverse order. The breadth of all these beds is the same as that of the arch itself. The lengths hK, wP, sV, xZ, of tile front lines of the moulds of the beds are respectively equal to the lines HF, NL, SQ, XV, on the face of the arch. And also, hg, nm, sr, xw, on the fronts of the moulds equal to the corresponding distances HG, NM, SR, XW, on the face of the arch. The distances kf, p I, u q, a V, are each equal to the perpendicular part AE, of the impost. To find the Joints of an Oblique Arch in Masonry. 23. Let ABC {Plate VI, fig. 1,) be the intrados, and DEF be the extrados, of the arch. Draw DK, AL, CM, FN, perpendicular to the base DF, of the arch. Make the angle DFG equal to the angle which the wall makes with the jambs of the arch, and draw KN, at a dis- tance from GF, equal to the thickness of the wall ; then the plan of the wall is represented by GFNK ; the abutment on one side, or springing base, is represented by GHLK, and that on the other side by FIMN. Let J be the centre of the given arch. 8 PRACTICAL MASONRY. Divide ABC, the intrados of the arch, into as many equal parts as the arch-stones are in number. Through the points 1, 2, 3, &c., draw hnes \ q, 2r,3s, Sec, cutting the one side KN of the wall at q, r, s, Sec, and the other side at n, o, p, &c. In figure 2, draw the straight line AB, and make AB equal to the length of the arch ABC, and let hg, gh, hi, be equal to the distances, 1, 2, 3, &c., on the arc ABC. Draw the perpen- diculars ACE, gin, hlo, &c. Make AC equal to AH, figure \; gk equal to k n, figure 1 ; hi to lo, figure \; im equal to mp, figure 1 ; and so on : then through the points C,k,l,m, &c., to D draw the curve line CD. Likewise make AE, g n, h o, ip, &c., respectively equal to K\j,kq,ms, &c., {fig- 1,); then, through all the points ^,n,o,p, &c., to F, draw the curve EF, which will complete the whole developement of the soffit of the arch. The parts CA «E, klon, Impo, &c., are the heads, or exact forms, of the ends of the stones of the arch, and therefore the moulds of the ends of the arch-stones must be made to corres- pond to these figures. To find the bevels of the joints of the stones. — Let q,s, u, {fig. 1,) be the points of division on the line of the intrados, next to the crown of the arch. From the centre J, and through the points q, s, u, &c., draw the lines Jr, J t, J v, &c., then qr, st,uv, &c., will represent the joints of the arch. From the points q, s, u, &c., draw q a, sd, ug, &c., parallel to AH, cutting GF in the points a,d,g, &c. ; and, from the points r,t,v, &c., draw re, tf, vi, &c., parallel to AH, cutting GF in the points c,f, i, &c. Draw be, ef hi, &c., parallel to DF. Then, to find the bed of the stone answering to the joint q r, draw the straight line abc. No. 1, and make ab equal to ba, figure 1. Draw ae perpendicular to ac, and make ae equal to qr, figure 1 ; and make ac, No. 1, equal to GK or HI, &c. In No. 1, draw cd parallel to b e, and e d parallel to a c ; then will the figure be formed of the bed of the stone. In the same manner we may form No. 2, to the joint s t ; and No. 3, to the joint u v ; and so on. Nos. 1, 2, 3, 4, 5, &c., are the forms of the moulds for the beds of the right-hand arch-stones ; and Nos. 1, 2, 3, &c., reversed on the right-hand, are the moulds for the beds of the arch-stones on the left-hand: viz. No. 1, and No. 1, are the two bed-moulds next to, and on each side of, the crown ; No. 2, and No. 2, are the second equi-distant bed-moulds from the crown. In working the stones, the beds ought to be numbered the same as the moulds, in order that the arch-stones may be readily applied together. The stone-cutters usually first work one of the beds, and mark the form of the mould upon the bed of the stone ; and so cut the rest from it. To find the Joints of an Oblique Circular Arch. 24. Let ABNO {figure 1, plate VII,) be the face of an oblique arch, of which rtmn is the plan ; AMrn», OQsn, the imposts ; rm and sn being the lines of the jambs. OBLIQUE ARCHES. 9 Suppose the obliquity of the arch to be given, with the number of stones requisite for its construction, the figure of the stones may be obtained by the following construction : — Find the centre C, of the span rs, which join with the points of division in the arch, by the straight hnes CB, CN, &c. At the point C, in rs, make the angle rCD equal to the given obliquity; in CD take any point, as P, and from P, draw PE, meeting rC perpendicularly in E : Upon EC describe the semi-circle Ea6cC, cutting the joints produced in the points a, b,c: with the distances Ea, E6, Ec, describe arcs meeting EC in the points a',b', c'; join Pa', Fb', and Pc', then will Par, V b' r, and Per, be the angles of the faces of the stones to which they are referred. Again, to find the angle of the bed: upon PC describe the semi-cu-cle Pa"b" c"C; and, from C, with the distances Ca,Cb,Cc, cut the semi-circle in a" b" c" ; join Fa",Pb", and Pc", then PC a", PC b", and PC c", will be the angles of the bed. 25. In this case the angles may be determined by Calculation. — In the triangle PCE we have given the angle at C equal to the obliquity, and the side CP any magnitude at pleasure ; hence the sides PE and EC can be found : then, in the triangle ECc, we have given the angle at C, and the side EC to find Ea equal to Eo' ; lastly, in the triangle EPa' we have given the sides PE, Ea', to find the angle Pa'E, which is the angle made by the face of the stone and its bed. The general formula is cot. req. ang. =:cot. obliquity x sin. 180°Xn> ', where w is the number of stones in the arch, and ?w any multiplier in the natural series, 1, 2, 3, &c. The angl/ formed by two contiguous boundaries of the bed is found exactly as the last. The formula is cos. reg. ang. = cos. obliquity x cos. ^. As a particular example, suppose the obliquity to be 73°, and the' number of stones 11, the respective angles will be exhibited in the following Tabid : — Divisiuns of (he Arch. Face Angles. Bed Angles. 1 2 3 4 5 16°„ 21' „ 49tV" 32 „ 4^ „ 38A 49 „ 5 „ 27A 65 „ 27 „ 16,*r 81 „ 49 „ 5-rV 85%, 4',, 37" 80 „ 36 „ 52 76 „ 59 „ 53 74 „ 27 „ 31 73 ., 9 „ 46 73°,, 42',, 29" 75 „ 45 „ 41 78 „ 57 „ 42 83 „ ^1 „ 25 87 „ SG „ 55 The angles for the remaining divisions being the supplements to those in the table, it is imnecessary to give them here. To apply the formulae to a numerical Example, we will take the first division in the table — Formula first : Formula second : 'Cot. 73° Log. —1.485339 Sin. 16°,, 21',, 49.^" 9.449836 [Cot. 85 „ 4 „ 37 8.935165 rCot. 7.3° Log. —1.465935 jCos. 16°,, 21',, 49 ,v" 9.982042 CCos. 73 „ 42 „ 29 .. 9.447977 10 PRACTICAL MASONRY. One of the stones, when finished, will appear as in figure 2 ; where PDE and QRC are the two angles requisite in its construction ; PDE being the angle of the iace, and QRC the an{{le of the bed. Oblique Arch. 26. Let ABCD, (fig. 1, plate VIII,) be the plan, parallel to which draw DC, (fig. 2,) on which, as a diameter, describe the semi-circle DFC ; divide the arc DFC into as many equal parts as the proposed number of stones to be in the arch, which, in this instance, is five. Draw the joints of the face tending to the centre E ; draw also the horizontals and perpen- diculars of the intrados marked by dotted lines in the figure. To form the arch-stones.— The plan of the jamb HBCL, enlarged to the line KI, will make a bed for a stone for the springing-course, and work the four adjacent sides each so as to be at right angles to IIIKL. Apply the mould MNOP (fig. 2,) to the two ends, so that MN may coincide with KL and IH ; the stone being thus gauged, make the upper and under beds parallel to each other. The stone, being now brought to the square, as seen at fig. o, apply the mould CNORQC, (fig. 2,) so that NO may coincide with be, and CN with ab. Draw dg, eh, and ap, parallel to the arris hi, then work off the joint dghe and the intrados aehpa, and the fiirst arch-stone will be finished. Having made the upper surface of the second stone, as in fig. 4, apply to it the mould STUV, (fig. 1,) forming the parallelogram abed, (fig. 4.) Then work off the four adjacent sides to a right angle with it, also gauge the stone to its depth, and work off the lower hori- zontal surface ; apply the mould of the head to the ends of the stone, as in working the first arch-stone, and draw the lines parallel to the arris a d, then work the joints and the intrados as before, and the stone will be finished. The key-stone, exhibited m figure 5, 'is wrought in the same manner, and the whole arch, as completed, is represented by figure 6. A Semi-circular Arched Pas.mge, hehveen Tivo Semi-circtilar Arched Vmdls. 21. To form the curve of intersection, and cut the itones for this arch. — Let AB (pi. IX.) be the thickness of the wall through which the passage is to be made, BC and A t the two semi-circular arches ; EL the opening of the passage ; by which its arch GHc is described. Divide the arch into any number of parts, at pleasure, and through the points of division draw the lines Ut, K^, wN, which, with the semi-circular arches, will form mixt angles, that serve to give the heads of the stones the proper projection, for intersecting the semi-circular vaults. To mark in the plan, the meeting of the passage with the semi-circular vaults, let fall the perpendiculars CO, SI, QR, &c., which, by their intersecting or meeting the lines RT, IV, OF, &c., will give the points R, I, O, &c., through which trace the curves POR and EFL. ARCHED GATEWAYS. 11 To trace one of the first stones; square the bed and one side of a stone, take the thickness of the wall AB, wliich set off on the arris of the stone, and, at each end of this line draw two others on the bed, square to the arris ; and with a bevel take the mixt angle ZAN, then dress the two heads by this bevel, applied square to the bed ; on the under bed set off G b, and trace a line parallel to the arris, and on the side set off bw, then work the soffit by the curve Gw, and cut the joints square to the curve of the sofiSt ; that is, the joint of the semi-circular vault by the mixt angle ANr, and that of the passage by the bevel Mm)m. Proceed with the other stones in the same manner, excepting that the bevel wQC is used to cut the sweep of the second stones, and the bevel sj} v for the key. The rest is so plain as to require no explanation. An Archway revealed and splayed, and the Splay arched with a Segment, in order to give room for Gates to ojien when they are made to the height of the front Arch. 28. The elevation {pi. X, figure 1,) will give a correct idea of an arch of this kind. A is the impost, BB the reveal, C the splayed recess. Let ABDC, {figure 2,) be the plan, h.e the depth of the impost, efg the reveal, ^C the splay. Describe the arch of the gate-head A'E B', and that of the reveal a e' b; and, at the extremities C and D of the splay, draw the perpendiculars CF' and DG', in which find the points F and G in the following manner: Describe the arch of the splay I'K', {fig. 3,) make I'L' equal to gC, {fig. 2.) ; perpendicular to I'L' draw L'K'; make M'F' and N'G' each equal to L' K', and through the points FG trace the arc F'G', as flat as may be necessary for the gates to swing open. The most complicated joint in this gate is OP, formed by the arc of the reveal and that of the splay. To draw the joint-mould for this: from the point //, ( /?^. 2,) draw A Q' perpen- dicular to AB, meeting O' P' in Q'. Draw I' S' perpendicular to I' L', and Q' S' and P' T' parallel to 1' L' : join T' S' intersecting the arc in U' ; draw U' V parallel to P'T', meeting the joint-line O'P' in V, and V is the point in which the stone will form an angle. Draw the line of the impost ah, and the reveal bed {fig- 2.); draw U'W perpendicular to I'L', make hi, on the splay of the jamb, equal to I'W, and draw ik parallel to AB. Make kl equal to O'V, mn equal to O'P', join dl, In, and abcdln will be the form of the joint; and all the joints which are cut in this forked angle are found in the same manner. For the mould of the second joint. — Make m p equal to XY, and join dp. To cut one of the first stones. — With the head-mould, B'O'P T, prepare an arch-stone, as No. 1, whose length is equal to am on the plan; apply the mould of the plan, lAefgCK, on the under-bed, and, on the upper-bed, the joint-mould, s abcdlnx. On the soffit of No. 1, draw ab, to mark the thickness of the impost, and, on the rear or tail of the stone. J 2 PUACTICAL MASONRY. draw erf, representing N'P' on the elevation. Then, to hollow out the concave surface of the reveal, witli a curved bevel h' I', {fig. 3,) draw the curves e f, gh. No. 1. By the lines, be, cd, dk, dress that side which will be terminated by k h, making use of the curved templet cut by b'l', {fig. 3,) which apply, from time to time, till the forked-joint is formed, and the whole of the superfluous stone being cut away, it will appear in the form of No. 2, The second stone. No. 3, is traced in the same manner. Of Spherical Vaults or Domes, and Niches. 29. The joints of a Spherical Vault, or Dome, are of two kinds ; the horizontal ones are portions of conic surfaces, and the vertical joints are planes tending to the centre. Figure 1, plate XI, represents the plan and section of a spherical dome, with the joint-lines of the stones; and, where the number of rings of stone are more numerous the construction is the same, and the moulds are found in the same manner. The first operation consists in dividing the plan and section into the proper number of stones, and drawing the joints; the points through which they pass being transferred from the plan to the section by the faint dotted lines shown in the figure. The next operation is to find the moulds for the springing-course ; the size of the stone is included in the lines 1-2-3-4 on the section; and, if the stone be worked as for a cylinder to be placed round the plan, so as to coincide with the joint-line ac, it will be prepared for apply- ing tlie mould A.-\A-ba; and the line Z;^, {fig. 3,) of the upper-bed should be drawn by a mould cut to a circular arc of the radius bp, {fig. 1,) the arc of the under-bed is the same as the plan of the wall, and the concave surface may be worked from the under-bed to a bevel, having its leg curved to the same curvature as the dome. The next stone {fig. 4,) is included in the lines, 5-6-7-8, of the section; and, in like manner, is to be svorked as part of a cylinder, and the mould ab-\i-\2-d in the section being applied to its vertical joints, the boundaries of the conical and spherical surfaces will be found, and the angle bad will be the bevel to work the spheric surface. Lastly, the key-stone is included by the lines 9-10-11-12; and, work a square stone to the size 11-12, and thickness 9-12; then describe a circle to the diameter 11-12, on the upper surface, and to the diameter dq, on the lower surface; to these draughts work the conical surface forming the bed, as shown in fig. 5, and the concave surface to a mould dUq, which completes the set. With foreign authors, it is usual to find the forms of flexible moulds for the beds, cmlk, and hefg, we do not think them necessary; but as they are easily found, we describe the readiest and most accurate method of obtaining them. Take the radius of the dome CB, and centre C, {fig. 2,) and describe an arc ch; then, draw a fine bC, cutting the arc in a; set off from a, on the arc on each side, the length of the arc a c on the plan, which will give the points m, c ; GROINED VAULTS. 13 and, from C, draw lines through m and c; also, make ab {Jig. 2.) equal to a Zi in the section, and from C describe an arc through b, then will chml be the development of the bed. In like manner h efg is the development of the upper-bed, marked with letters corresponding to those of the parts whence the measures are taken in the plan and section. 30. Spherical Niches are constructed in the same manner; the niche being considered a portion of a dome, and is usually half a dome. 31. When a Dome has an elliptical base, the same method may be followed, but the division into arch-stones should be made so that the opposite stones may be exactly in corresponding parts of the curve of the plan ; for then, four stones of each ring may be worked by the same moulds. Of Ribbed Groin Vaults. 32. The simple groined vault, with ribs, is the most difficult to construct ; for the ribs of the other kinds of Gothic vaults are all of the same curvature, and meet, at equal angles, on the pillars or corbels from whence they spring. Let ABCD, {fig. 1, plate XII,) be the plan of the first division of a ribbed-groined ceiling ; and fig. 2 the section through GH ; fig. 3 the angle rib ; fig. 4 the plan of the top of the corbel or capital on which the ribs meet ; and fig. 5 the key-stone. The conditions to be attended to in the construction, are, that the plan of the ribs must meet within a circle on the top of the capital or corbel ; and, that the angle-ribs shall be traced to correspond with the body -ribs ; to obtain these conditions, the plain part of the pannels of the ceiling must deviate a little from the true groin, but this is a less evil than any which can be taken to remedy it. Imagine the angle-rib BI, (fig. 1,) to turn on the centre, B, till it be parallel to BA; then, if BE (fig. 3,) be the form of the body-ribs, BI will be that of the angle ones ; and is traced from BE, in the manner shown by the lines. The stones of the ribs are generally long enough to correspond with two stones of the pannels ; but, in some cases, the stones of the pannel are made to bond into the rib, at every second or third stone of the rib ; and the joints of the ribs are always strengthened by dowel?, or plugs, two to each joint. The plan of the key-stone is an octagon, (fig. 5,) and the under part is shown below, with the section between. All the intersections are covered with roses, or bosses ; these are now commonly modelled and cast in Roman cement ; but in former ages they were carved in stone. Of Raking Mouldings. 33. Raking Mouldings frequently occur in Masonry; hence we give the following designs, which will be sufficient to explain the method of forming them to mitre in a proper manner. E l-t PRACTICAL MASONRY. Figure 1, plate XIII, is a complete design of a cornice, having part of the ogee level, and part inclined, as happens in a building, with a pediment in the front : a, b, c, d, e, is the mould- ing at the angle of the break, or projection of the pediment, with this moulding given, we have to find the right section of the inclined ogee in the pediment. Let af and e e be the two parallel lines which terminate the breadth of the raking or inclined moulding ; and let a k and el he the parallel lines tenninating the breadth of the moulding which is level. At a convenient place draw 2> t parallel to the edge a h of the level ogee ; and in the given moulding, a,b,c,d,e, take any number of points, b, c, d, and draw bg, c/i, di, parallel to af, or ee; also draw ap, bq, cr, ds, and ct, perpendicular to ak, or el, meeting pt m the points q, r, s : also, at any convenient distance from af, draw p' t' parallel thereto, and transfer the distances p q, qr, rs,st, to p'q', q'r', r's', and s'i', and draw p'A, q'B, r'C, s'D, fE, perpen- diculars to t'p', or af, meeting the lines af, bg, ch, di, ee, in the points A, B, C, D, and E, and a curve, being drawn through these points, will be the right section of the raking-moulding. To find the section through the mitre of the two inclined sides, where they meet at the top of the pediment, draw t"p" perpendicular to t" e, and transfer the distances ts, sr, rq, qp, to t" s", s"r", r"q", q"p". Draw «"d, r" c, q"h, 2)"a; perpendicular to f'j}", also draw /a, qh, he, id, perpendicular to t" e. Then the curve through the points abode will be the common section of the two raking-mouldings, as required. Figure 2 is a reverse ogee, which is traced on the same principle as the ogee, figure 1. CHAPTER II. OF THE MATERIALS EMPLOYED IN MASONRY. Si. BuiLDiNG-STONE is a dense coherent body of considerable hardness and durability, generally of a brittle nature, and it possesses these qualities in various degrees, according to the nature of the matter it is formed of, or the manner in which its parts are joined to one another. The texture of stones is either slaty or granulated, or it is of a mixed nature. 35. Building stones are generally composed of two or more of the chemical earths called siHca, alumina, hme, and magnesia, with small quantities of some of the metals combined with acids, water, and sometimes with the fixed alkalies ; some other chemical elements are some- times found in building-stones, but not often in sufficient quantity to affect the nature of the stones. 36. Slaty stones consist of thin plates, or layers, cohering more or less strongly together ; when the layers are of considerable size, and cohere so slightly that they may be easily sepa* MATERIALS. 15 rated, the stones are called Slates. The layers are always nearly parallel to the quarry-beds of the stone, and they should always be horizontal, or as nearly so as possible, in a building,- otherwise the action of the weather will cause them to separate, and fall off in flakes. Sand- stones generally have a slaty texture, and the direction of the layers may often be discovered by their different shades of colour, when they will not readily separate ; in others, the layers may be distinguished by the position of minute scales of shining mica, which always lie parallel to them. In most stones, the direction of the layers may be ascertained by the facility with which the stone yields to the tool in that direction, but a considerable degree of practice is necessary to acquire so nice a discrimination of resistance, and good workmen only attain it. 37. Among slaty stones those are the most durable in which the slaty structure is least distinct, and the texture uniform. When the parts do not perfectly cohere, they are soon injured by frost, and they are wholly unfit for places alternately wet and dry. 38. Granulated stones consist of distinct concretions resembling grains, either all of the same, or of different minerals, cohering together. When the texture is uniform, and the grains or concretions are small, stones of this kind are always strong and durable, if the con- cretions themselves be so. Granulated stones are sometimes open and porous, but when they are uniformly so, they seldom suffer materially by frost, because their uniform porosity allows the expansive force of the congealing-water to be distributed in every direction. 39. Stones of a compound structure, that is, partly laminated and ])artly granular, have, more or less, of the characters of the two classes before described ; for it may be observed, in coarse-grained granite, that the laminated structure of some of its parts, render it very liable to shiver away by the effect of the weather. 40. All the kinds of stone, in the quarry, are found divided by vertical or inclined seams, cr joints, which are sometimes so close that they cannot be distinguished till the stones be wrought, but they often separate under the tool at such seams ; and it is not safe to employ stone to resist any considerable cross-strains, on account of the difficulty of knowing where those seams are. 41. The qualities requisite for building-stones for bridges, or water-works, are, hardness, tenacity, and compactness, with the property of resisting the decomposing effects of water, and of the atmosphere. Besides, the strength necessary to support the weight in such buildings, they must also often have to resist the impetus of floating bodies, and particularly of large masses of ice. Those stones which are the hardest, are not precisely those which have the most tenacity or toughness, of this we have a familiar illustration in comparing common lime- stone and glass ; the latter, though much harder, is far more easily broken than the former. 42. The causes that accelerate the decay and destruction of stone in buildings are nearly the same with those which occasion the destruction or wear of rocks on the surface of the globe ; they may be classed into two kinds : those of decomposition, and those of disunion of parts. In the former, a chemical change is effected in the stone itself; in the latter, a mecha- nical division and separation of its parts. IG PRACTICAL MASONRY. 43. Decomposition takes place, when the stone contains parts that are, more or less, soluble in water, or which enter into combination with the oxygen of the air or acids in water. Iron, in different states of oxydation, and in different proportions, enters into the composition of almost all stones, and is frequently an important agent in their decomposition. When stones contain pure iron, it rusts or oxydates, and expands so as to burst the parts asunder. The iron absorbing oxygen and carbonic acid from the air, the presence of moistures accelerates this kind of decomposition and it is always still further hastened by increase of temperature. According to the observations of Kirwan, stones, containing iron, which does not contain its full doze of oxygen, are of a black, a brown, or a bluish colour ; arid, in some instances, when united with clay and magnesian earth, they are of a gray or greenish gray ; the former, as the iron draws oxygen from the air, changes to purple, red, orange, and, finally, pale yellow ; the latter kind becomes, at first, blue, then purple, then red, &c. But stones, containing iron, combined with its full doze of oxygen, are generally very durable : such are red porphyry, jaspers, &c. Stones, containing manganese, lime, alumina, carbon, or bitumen, in particular states, are subject of decomposition, from the affinities of one or other of these bodies ; but nothing very decisive is, or perhaps can be, known, respecting such changes, unless the com- ponent parts be determined with some certainty. 44. Disintegration is the separation of the parts of stones by mechanical action , the chief cause is, the congelation of water in the minute pores and fissures of stones, which bursts them open, or separates small parts according as the structure is slaty, or irregularly granulated. The south sides of buildings, in northern climates, are most subject to fail from this cause; for the surface is often thawed, and filled with wet, in the sunny part of the day, and frozen again at night. This repeated operation of freezing is also very injurious to sea-walls, the piers of bridges, and other works exposed alternately to water and frost. 45. Granite is a compound sihceous rock, which varies much in the proportion of its constituent parts, and its degrees of hardness ; compared with most other rocks, granite may be considered as a durable building-stone ; but those granites that contain much white felspar, and only a small portion of quartz, like the greater part of tlie granites of Cornwall and De- vonshire, are liable to decomposition and disintegration much sooner than many of the Scotch granites, in which the quartz is more abundantly, and more equally disseminated, and the grain finer. In the selection of gi-anite, in Cornwall and Devonshire, the preference is given to that which can be procured in the largest blocks, and worked with the greatest ease, and for common purposes, it may answer very well ; but, for the piers and arches of bridges, the harder granite will be found much more durable, such as the Aberdeen now using for London Bridge. In Cornwall, many of the granite rocks are in a state of rapid disintegration and decay, the felspar in that granite contains a portion of potass, and to this its more rapid de- composition may be principally ascribed, hence the stones should be carefully selected. The Naval Hospital of Plymouth is built of Cornish or Devonshire granite, which appears to liave MATERIALS. 17 been selected with care, for it has been erected about seventy years, and exhibits no symptoms of decay, except some slight ones in the columns forming the colonnade in front of each building. Cornish granite was used for the Waterloo Bridge, and shows some tendency to fret away in the piers ; the new Londoa Bridge is of Aberdeen granite. Kind of Granite. Weight of a cubic foot. ^'^7" '» "■*' bear with " safety on a square foot. Cornish Granite 166 lbs. .. 114,000 lbs. Peterhead Do — .. 149,000 Aberdeen Blue Do 164 .. 196,000 46. Lime-Stones are very different in external appearance ; the most crystalline marble as well as chalk and calcareous sand-stone being composed of lime. Of marbles there are an almost infinite variety, indeed every variety of lime-stone that admits of a good polish is deno- minated marble. Though lime is, in a certain degree, soluble in water and carbonic acid, yet, in its most indurated state, as in crystalline marble, the action of the atmosphere produces little change in the course of many centuries ; but, when exposed to the constant action of water, the decomposition is more rapid. Those marbles which are the most uniform in their texture, which possess the greatest degree of specific gravity and hardness, and which will receive the highest polish, are those which will prove the most durable. The common coloured, and the softer kinds, are very generally used for building-stones in all lime-stone districts ; and the prin- cipal varieties are here described. 47. The Portland and Bath stones (called Roe stone^ are lime-stones, and very extensively employed in architecture ; they can be worked with great ease, and have a light and beautiful appearance, but are porous and possess no great durability, hence they should not be employed where there is much carved or ornamental work, for the fine chiselling is soon effaced by the action of the atmosphere ; on the other hand, on account of the ease and cheapness with which they can be carved, they are much used by our Enghsh architects, who appear to .have little regard for futurity.* Portland as well as Bath Stone varies much in its quahty; but we think greater attention was paid to its selection in the construction of St. Paul's Cathedral, than in many of the modern edifices built of this stone, though we have observed many stones in the upper part of the building mouldering away ; yet, on the whole, it is less injured by the weather than Somerset- House. In buildings constructed of this stone, we may frequently observe some of the stones nearly black, and others presenting a white clean surface. The black stones are those which » The Chapel of Henry Vll. afTords a lamentable proof of the inattention of the architect to the choice of the stone. All the beautiful ornameotal work of the exterior had mouldered away in the comparatively short period of three hundred years; it has recently been cased with a new front of Bath stone, in which the larviiig has been farthfully copied, but, fiom Ine nature of the stone, we may predict that its duration will not be longer than that of the original. Probably the arcnitect was bunted by contract, which precluded the use of a more durable bat more costly stone. P 18 PRACTICAL MASONRY. are most compact and durable, and preserve their coating of smoke; the wliite stones are decomposing and constantly presenting a fresh surface, as if they had been recently scraped. This effect is strikingly exhibited in the columns of Somerset-House. 4-8. Bath Stone, Ketton Stone, and Painswick Stone, are all varieties of the same kind of stone, procured at those different places, as well as from several others in their neighbourhood. The stone is so much softer than that from Portland, that it may be cut with a carpenter's saw, and it may be moulded and carved more in the manner of wood than of stone, nevertheless it is quite as durable as Portland stone, and fitted for similar works, excepting where strength or wear is required. The Painswick variety is perhaps the closest and best for London use, as it works with very little waste; the Ketton seems to be the most durable, but none of theso varieties are hard enough for steps, stairs, or other works liable to wear, or requiring strength 49. The strength and weight of the different varieties of Limestone are as under — Kinds of Lime-Stone. Weight of a cubic foot. ^"f "''^ " «'" bear with ° safely ou ;i square foot. White Statuary Marble 172^ lbs. . . 83,000 lbs. Veined White Marble 1 70 . . 1 74.000 Variegated Red Devonshire Marble — .. 129,000 Portland Stone 132 .. 30,000 Bath Stone 1231 .. 17,000 50. Argillaceous Stones, or those which contain in their composition a considerable portion of clay, are generally found to contain also a large portion of iron. This metal appears to have a greater affinity for argil, or clay, than for any other earth ; and is sometimes combined with argillaceous stones in the proportion of one-fourth of the whole mass. The iron is fre- quently in the state of black ox^de, and in this state rapidly combines with a larger portion of oxygen, when exposed to the atmosphere, and thus occasions the surface of the stone to swell and shiver away. Stones of this kind, in their native beds, some hundred feet under the surface, are so extremely hard that they resist the point of the pick, and can be removed only by blasting ; yet, when the same stone is exposed for some months to the air, it becomes soft, and shivers into small pieces. It rarely happens that builders or engineers have sufficient mineralogical science to enable them to anticipate the changes which will be effected by air and moisture on the materials they select ; and the loss which this ignorance has occasioned in the construction of many public works is well known. 51. The most important of the argillaceous stones is the common Whin-Stone, called basalt bv geologists ; this stone is found in many parts of England, and also in Scotland, where whole villages are built of it, even where sand-stone could have been easily procured, as in the neighbourhood of Kelso. "Whin-stone, when broken, is generally of a blue colour, of close grain, and remarkably hard ; in its natural beds it is in irregular masses ; too clumsy, and too MATERIALS. 19 hard for the finer works of masonry ; the best for architectural purposes is found in loose blocks in the beds of rivers, and places of a like nature, where it has been long exposed to the wea- ther, for some varieties of whin-stone decompose by exposure in the manner of other argil- laceous stones, (art. 50.) and are said to become rotten. By exposure, a thin coatin'^ forms on the surface of whin-stone ; and it is said to be more durable when the coat is frequenfly cleaned off. The more hard and durable kinds are valuable for road materials. Whin-stone and indeed all argillaceous stones, attract moisture, and in consequence assume a darker colour in damp weather ; when the atmosphere is damp, walls of this stone condense the vapour till it runs down in streams, hence it is not generally adapted for houses. The weight of a cubic foot of whin-stone varies from 170 to 192 lbs. ; and, according to experiment, it appears that 280,000 lbs. may be supported by a superficial foot with safety. 52. Of Sand-stones there are two kinds, which are very common, viz. the siliceous and the argillaceous ; — of these the siUceous is the best, and perhaps the most abundant. Sand-stone is common to most counties of England, as well as Scotland. The quarries of siUceous sand-stone about the cities of Glasgow and Edinburgh afford very superior kinds, which contribute in no small degree to the elegance of the buildings in these places ; the supe- riority, however, is in material only, as the taste with which some towns built of brick have been laid out and executed, is not inferior to that displayed by the architects of the north. In the parish of Sproustone, near Kelso, is a sand-stone quarry, belonging to the Dowager Duchess of Roxburgh, of immense value. The stone is of a beautiful silver grey, which, when exposed to the weather, soon becomes of a smokey hue. It is remarkably fine grained, indeed, so fine, that it is unfit for the purpose of whetting an edged instrument. Most part of Kelso is built of it, as well as the whole of the bridges in its vicinity. Although not a haul stone, it is very durable, and the seam is so deep and long that stones of large dimensions can be procured from it. There are also many other excellent beds of sand-stone in the course of the Tweed, but that which we have just mentioned is perhaps the best. A little farther up, on the lands of Dry- burgh, the property of the Earl of Buchan, there is plenty of sand-stone ; it is of a deep red colour, and much indented by cross scars and seams ; it is not, therefore, so generally useful as some other at no great distance from it. In the body of this stone there are many small pieces of a softer texture, and a deeper red, that do much injury to it as a durable mate- rial. The celebrated statue of Sir William Wallace, the defender of Scottish liberty, is cut out of a mass of this stone ; but the sculptor, Mr. John Smith, of Damick, has shown his skill m selecting the piece which he has used, as it appears too hard to vield to the ravages of time and of weather. On the banks of the Tiviot, in the parish of Roxburgh, there is a bed of sand-stone, of excellent quality, fit for almost any purpose to which it may be applied. This has been used to a great extent, by the proprietor, Sir George Douglas, of Springwood Park, but has not been 20 PRACTICAL MASONRY. biou'^lit into general use. It is of a white yellow colour, and rises from the bed in masses sufficiently large for every purpose of masonry. In the old buildings, in the neighbourhood, there is a species of sand-stone of a beautiful yellow and uncommonly soft ; but where the I)uilders found it cannot now be ascertained, as no vestige of a seam remains wherein the stone is of such a deep and beautiful colour. Should such be discovered, it will be of immense value to the proprietor, from its beauty, which would bring plenty of purchasers : but we conclude that it is of a nature not adapted to resist the weather, and that, in process of time, by being exposed to wetness and drought, it becomes of that soft state we find it in among the ruins of old buildings. A little farther up, on the precipitous banks of the Tiviot, there are extensive beds of yellow sand-stone ; but, from their situation, they cannot be wrought with success. In Dumfriesshire are great quarries of sand-stone, both of a red and white colour, exceed- ingly good ; the towns of Dumfries and Maxwelton are built chiefly of the red kind. The masses here are very small, and prevent the masons exhibiting their skill, to any great extent, in cutting figures, and other architectural ornaments. If we mistake not, there are numerous and excellent beds of this stone about the town of Kirkcudbright, and the surrounding country : but that which is found abundantly in Ayrshire, on account of its white colour and durable nature, is to be preferred to any that we have yet mentioned, Sproustone only excepted. The quarries in the other parts of Scotland, being nearly of the same nature with those already described, and this remark applying also to the quarries of sand-stone in England, we need not enter into farther notice of it ; since its utility, as a building material, is very gene- rally known. A kind of argillaceous sand-stone is much used in London, for rough pavhig and steps, under the name of Yorkshire Stone; it is a very strong and durable stone, and wears well; but there is an objection to its use for internal work, owing to its absorbing damp rapidly, which renders it cold and uncomfortable for flooring. 53. The strength and the weight of a cubic foot of the diflerent varieties of sand-stone are as under : — „...„, -^ ,,,.,,, ,■ e . Pressure it will bear with Kmds of Saud-Stone Weight of a cubic foot. ^^^^j^ ^^ ^ ^^^^^.^ ^^^ Dundee Stone 163 lbs. 119,000 lbs. Bromley-fall Stone 1 57 . . 1 09,000 Yorkshire Paving Stone 157 .. 102,000 Craigleith Stone 1 54 . . 98,000 Collalo Stone 152 .. 82,000 MORTARS AND CEMENTS. 21 OF MORTARS AND CEMENTS, 54. In the construction of works in Masonry, we generally employ some kind of cementitious matter for connecting the stones together, and rendering them firm and compact. "SVhen the works are to be exposed to the action of v/ater immediately after being built, this cementitious matter must be of such a nature, that it will harden under water. Hence it is, that we have occasion for two kinds of mortar, one that will set and harden under water, called by Smeaton a water-mortar, or cement ; and common mortar for ordinary buildings. oo. Common Mortar, it is almost superfluous to say, is a preparation of lime and sand, mixed with water, which serves to unite the stones, in the building of walls, &c., and on the proper or improper manner in which such mortar is prepared and used, depends the durability and security of buildings ; we shall, therefore, here introduce many particulars on this head, discovered by Smeaton, Dr. Higgins, &c., but which, not being generally known, have never been introduced into general practice. 56. Limestone, marble, chalk, or shells, may be used to burn for lime for common mortar, all these substances being composed chiefly of lime and carbonic acid ; and if a piece of one of them be slowly burnt or calcined, so as to expel the whole, or nearly the whole, of its carbonic acid, it loses about 44 per cent, of its weight ; and when a small quantity of water is added to the calcined matter, it swells, gives out heat, and falls into a finely-divided powder, called slacked lime. The bulk of the powder is about double that of the limestone. If this powder be rapidly formed into a stiflf paste with water, it sets or solidifies as a hydrate oi lime, and ultimately hardens by the absorption of carbonic acid from the air. This constitutes common building-mortar. Hydrate of lime consists of 100 parts of lime, and 31 parts of water. Common limestone consists of carbonate of lime, with very little of any other substance; it produces a white lime, which slacks freely when well burnt ; it dissolves in diluted muriatic acid, with only a small portion of residue, and never contains more than a trace of iron. It diflfers much in external characters, as chalk, marble, common compact limestone, &c. These limestones do not form cements to set in water, without the addition of other kinds of cementing matter; hence they are usually employed only for common mortar. The hardest marble and the softest chalk make equally good lime when well burnt ; but chalk-lime will slack when not perfectly burnt, and, therefore, seldom has a sufficient quantity of fire ; whereas stone-lime must have sufficient to make it slack. It was also observed by Dr. Higgins, that stone-lime does not re-absorb carbonic acid so rapidly as chalk-lime Lime, made from common limestones, sustains very little injury from being kept after it has been formed into mortar, provided the air be effectually excluded ; indeed, Alberti mentions G 22 PRACTICAL MASONRY. an instance of some which had been covered up in a ditch for a very long time, and yet was found to be of an excellent quality. 57. Sand. — To employ lime alone in the composition of mortar would render it expensive, besides, it would be of inferior quality. The material commonly used to mix with lime is sand, and this sand should be of a hard nature, not very fine, but angular, and having a consider- able degree of affinity for lime, also the more irregular it is in size the better. It should be free from any mixture of soft or earthy matter, if it can be procured without. The reason is obvious; for mortar, composed of soft sand, cannot be harder than that sand. Sea-sand makes good mortar, particularly water-mortar. Very hard-burnt brick, or tile, reduced to a coarse powder, also makes an excellent substance to mix with lime, for many purposes. The best proportion of sand, for common mortar, is easily ascertained by trial ; enough should be added to render the mortar rather short than tough under the trowel. The propor- tion varies from 4 parts of sand to 1 of lime, to 1 j parts of sand to 1 of lime, by measure, the proportion differing according to the coarseness of the sand, the nature of the limestone, and the precautions used in burning it ; all set proportions being universally adhered to only by those who are utterly ignorant of the subject. In many situations, it is impossible to procure good sand, except at an enormous expense. .58. Making Mortar. — The instructions given by Dr. Iliggins for making stucco-mortar, apply only when a very superior kind is wanted ; but the same general principles ought to be followed even with the commonest kinds of mortar. We will, therefore, insert them in this place. Of Sand, the following kinds are to be preferred ; first, drift-sand, or pit-sand, which con- sists chiefly of hard quartose flat-faced grains, with sharp angles ; secondly, that which is the freest, or may be most easily freed by washing, from clay, salts, and calcareous, gypseous, or other grains less hard and durable than quartz ; thirdly, that which contains the smallest quan- tity of pyrites, or heavy metallic-matter, inseparable by washing ; and fnurthly, that which suffers the smallest diminution of its bulk in washing. Where a coarse and fine sand of this kind, and corresponding in the size of their grains with the coarse and fine sands hereafter described, cannot be easily procured, let such sand of the foregoing quality be chosen as may be sorted and cleansed in the following manner : — Let the sand be sifted in streaming clear water, through a sieve which shall give passage to all such grains as do not exceed one-sixteenth of an inch in diameter ; and let the stream of water, and the sifting, be regulated so that all the sand which is much finer than the Lynn-sand, commonly used in the London glass-houses, together with clay, and every other matter sneci- fically lighter than sand, may be washed away with the stream ; whilst the purer and coarser sand, which passes through the sieve, subsides in a convenient receptacle, and the coarse rubbish and rubble remain on the sieve to be rejected. MORTARS AND CEMENTS. 23 Let the sand, which thus subsides in the receptacle, be washed in clean streaming water through a finer sieve, so as to be further cleansed, and sorted into two parcels ; a coarser, which will remain in the sieve, which is to give passage to such grains of sand only as are less than one-thirtieth of an inch in diameter, and which is to be saved apart under the name of coarse sand; and a finer, which will pass through the sieve and subside in the water, and which is to be saved apart under the name oi fine sand. Let the coarse and the fine sand be dried separately, either in the sun, or on a clean iron plate, set on a convenient surface, in the manner of a sand-hea'v. Let stone-lime be chosen, which heats the most in slaking, and slakes the quickest when duly watered ; that which is the freshest made and closest kept ; that which dissolves in distilled vinegar with the least effervescence, and leaves the smallest residue insoluble, and in the residue the smallest quantity of clay, gypsum, or martial matter. Let the lime, chosen according to these rules, be put in a brass-wired sieve, to the quantity of fourteen pounds. Let the sieve be finer than either of the foregoing ; the finer the better it will be : let the hme be slaked, by plunging it into a butt filled with soft-water, and raising it out quickly, and suffering it to heat and fume ; and, by repeating this plunging and raising alternately, and agitating the lime until it be made to pass through the sieve into the water ; and let the part of the lime which does not easily pass through the sieve be rejected : and let fresh portions of the lime be thus used, until as many ounces of lime have passed through the sieve as there are quarts of water in the butt. Let the water, thus impregnated, stand in the butt closely covered until it becomes clear, and through wooden cocks, placed at different heights in the butt, let the clear liquor be drawn off, as fast and as low as the lime subsides, for use. This clear liquor is called lime- tcater. The freer the water is from saline matter, the better will be the cementing liquor made with it. Let fifty-six pounds of the aforesaid chosen lime be slaked, by gradually sprinkhng the lime-water on it, and especially on the unslaked pieces, in a close clean place. Let the slaked part be immediately sifted through the last mentioned fine brass-wired sieve : let the lime which passes be used instantly, or kept in air-tight vessels ; and let the part of the lime which does not pass through the seive be rejected. This finer and richer part of the lime, which passes through the sieve, may be called purified lime. Let bone-ash be prepared in the usual manner, by grinding the whitest burnt bones ; but let it be sifted, so as to be much finer than the bone-ash commonly sold for making cupels. The best materials for making the cement being thus prepared, take fifly-six pounds of the coarse sand, and forty-two pounds of the fine sand ; mix them on a large plank of hard wood placed horizontally ; then spread the sand so that it may stand to the height of six inches, with a flat surface on the plank, wet it with the lime-water, and let any superfluous quantity of the liquor, which the sand in the condition described cannot retain, flow away off the plank. To 24 PRACTICAL MASONRY. the wetted sand add fourteen pounds of the purified lime, in several successive portions: mixino- and beating tliem up together, in the mean time, with the instruments generally used in making fine mortar : then add fourteen pounds of the bone-ash, in successive portions, mixing and beating all together. Tlie ouicker and the more perfectly these materials are mixed and beaten together, and the sooner the cement thus formed is used, the better it will be. This may be called coarse-grained cement, which is to be applied in building, pointing, plastering, stuccoing, or other work, as mortar and stucco generally are ; with this difference chiefly, that, as this cement is shorter than mortar, or common stucco, and dries sooner, it ought to be worked expeditiously in all cases; and, in stuccoing, it ought to be laid on by sliding the trowel upwards on it. The materials used along with this cement in building, or the ground on which it is to be laid in stuccoing, ought to be well wetted with the lime-water in the instant of laying on the cement. The lime-water is also to be used when it is necessary to moisten the cement, or when a liquid is required to facilitate the floating of the cement. When such cement is required to be of a still finer texture, take ninety-eight pounds of the fine sand, wet it with the lime-water, and mix it with the purified lime and the bone-ash, in the juantities and in the manner above described ; with this difference only, that fifteen pounds jf lime, or thereabouts, are to be used instead of fourteen pounds, if the greater part of -he sand be as fine as Lynn sand. This may be called fine-grained cement. It is used in living the last coating, or the finish, to any work intended to imitate the finer-grained stones or stucco. But it may be applied to all the uses of the coarse-grained cement, and in the same manner. When, for any of the foregoing purposes of pointing, building, &c., a cement is required much cheaper and coarse-grained than either of the foregoing, then much coarser clean sand than the foregoing coarse sand, or well-washed fine rubble, is to be provided. Of this coarse iand, or rubble, take fifty-six pounds, of the foregoing coarse sand twenty-eight pounds, and of the fine sand fourteen pounds ; and, after mixing these, and wetting them with the cementing-liquor, in the foregoing manner, add fourteen pounds, or somewhat less, of the purified lime, and then fourteen pounds, or somewhat less, of the bone-ash, mixing them toge- ther in the manner already described. When the cement is required to be white, white sand, white lime, and the whitest bone-ash, are to be chosen. Gray sand, and gray bone-ash formed of half-burnt bones, are to be chosen to make cement gray ; and any other colour of the cement is obtained, either by choosing coloured sand, or by the admixture of the necessary quantity of coloured talc in powder, or of coloured, vitreous, or metallic, powders or other durable colouring ingredients, commonly used in paint. This cement, whether the coarse or fine-grained, is applicable in forming artificial stone, by making alternate layers of the cement and of flint, hard stone, or bricks, in moulds of the !igure of the intended stone, and by exposing the masses so formed to the open air, to hardeti. MORTARS AND CEMENTS. 25 When such cement is required for water-fences, two-thirds of the prescribed quantity of bone-ashes are to be omitted ; and, in the place thereof, an equal measure of powdered terras is to be used ; and, if the sand employed be not of the coarsest sort, more terras must be added, so that the terras shall be one-sixth part of the weight of the sand. When such a cement is required of the finest grain, or in a fluid form, so that it may be applied with a brush, flint-powder, or the powder of any quartzose or hard earthy substance, may be used in the place of sand ; but in a quantity smaller, in proportion as the flint or other powder is finer ; so that the flint-powder, or other such powder, shall not be more than six times the weight of the lime, nor less than four times its weight. The greater the quantity of lime within these limits, the more will the cement be liable to crack by quick drying, and, vice versa. Where the above described sand cannot be conveniently procured, or where the sand cannot be conveniently washed and sorted, that sand which most resembles the mixture of coarse and fine sand above prescribed, may be used as directed, provided due attention be paid to the quantity of the lime, which is to be greater as the quality is finer, and, vice versd. Where sand cannot be easily procured, any durable stony body, or baked earth, grossly powdered, and sorted nearly to the sizes above prescribed for sand, may be used in the place of sand, measure for measure, but not weight for weight, unless such gross powder be speci- fically as heavy as sand. Sand may be cleansed from every softer, lighter, and less durable, matter, and from that part of the sand which is too fine, by various methods preferable in certain circumstances, to that which has been already described. Water may be found naturally free from fixable gas, selenite, or clay ; such water may, with- out any great inconvenience, be used in the place of the lime-water ; and water approaching this state will not require so much lime as above prescribed to make the lime-water ; and a Hme-water sufficiently useful may be made by various methods of mixing lime and water in the described proportions, or nearly so. When stone-lime cannot be procured, chalk-lime, or shell-lime, which best resembles stone- lime, in the foregoing characters of lime, may be used in the manner described, excepting that fourteen pounds and a half of chalk-lime will be required in the place of fourteen pounds of stone-lime. The proportion of lime, as prescribed above, may be increased without incon- venience, when the cement or stucco is to be applied where it is not liable to dry quickly ; and, in the contrary case, this proportion may be diminished. The defect of lime, in quantity or quality, may be very advantageously supplied, by causing a considerable quantity of lime-water to soak into the work, in successive portions, and at distant intervals of time ; so that the calcareous matter of the lime-water, and the matter attracted from the open air, may fill and strengthen the work. H 26 ■ PRACtlCAL MASONRY. The powder of almost every well-dried or burnt animal substance may be used instead of bone-ash ; and several earthy powders, especially the micaceous and the metallic ; and the elixated ashes of divers vegetables, whose earth will not burn to lime, as well as the ashes of mineral fuel, which are of the calcareous kind, but will not burn to lime, will answer the ends of bone-ash in some degree. The quantity of bone-ash described may be lessened without injuring the cement ; in those circumstances especially which admit the quantity of lime to be lessened, and in those wherein the cement is not liable to dry quickly. The art of remedying the defects of lime may be advantageously practised to supply the deficiency of bone-ash, especially in building, and in making artificial stone with this cement. As the preceding method of making mortar differs, in many particulars, from the common process, it may be useful to inquire into the causes on which this difference is founded. When the sand contains much clay, the workmen find that the best mortar they can make must contain about one-half lime ; and hence they lay it down as certain, that the best mortar is made by the composition of half sand and half lime. But with sand requiring so great a proportion of lime as this, it will be impossible to make good cement ; for it is universally allowed that the hardness of mortar depends on the crystal- lization of the litne round the other materials which are mixed with it ; and thus uniting the whole mass into one solid substance. But, if a portion of the materials used be clay, or any other friable substar.ce, it must be evident that, as these friable substances are not changed in one single particular, by the process of being mixed up with lime and water, the mortar, of which they form a proportion, will consequently be, more or less, of a friable nature, in pro- portion to the quantity of friable substances used in the composition of the mortar. On the other hand, if mortar be composed of lime and good sand only, as the sand is a stony sub- stance, and not in the least friable, and as the lime, by perfect crystallization, becomes likewise of a stony nature, it must follow, that a mass of mortar, composed of these two stony sub- stances, will itself be a hard, solid, unfriable, substance. This may account for one of the essential variations in the preceding method from that in common use, and point out the neces- sity of never using, in the place of sand, which is a durable stony body, the scrapings of roads, old mortar, and other rubbish, from antient buildings, which are frequently made use of, as all of them consist, move or less, of muddy, soft, and minutely divided particles. Another essential point is the nature and quality of the lime. Now, experience proves that, when lime has been long kept in heaps, or untight casks, it is reduced to the state of chalk, and becomes every day less capable of being made into good mortar ; because, as the goodness or durability of the mortar depends on the crystallization of the lime, and, as experiments have proved, that lime, when reduced to this chalk-like state, is always incapable of perfect crystal- lization, it must follow that, as lime in this state never becomes crystallized, the mortar of MOUTARS AND CEMENTS. 27 which it forms the most indispensable part, will necessarily be veiy imperfect ; that is to say, it will never become a solid stony substance ; a circumstance absolutely required in the formation of good durable mortar. These are the two principal ingredients in the formation of mortar; but, as water is also necessary, it may be useful to point out that which is the fittest for this purpose ; the best is rain-water^ river-water the second, land-water next, and spring-water last. The ruins of the antient Roman buildings are found to cohere so strongly, as to have caused an opinion that their constructors were acquainted with some kind of mortar, which, in com- parison with ours, might justly be called cement: and that, to our want of knowledge of the materials they used, is owing the great inferiority of modern buildings in their durability. But a proper attention to the above particulars would soon sHow that the durability of the antient edifices depended on the manner of preparing their mortar more than on the nature of the materials used. The following observations will, we think, prove this beyond a possibility of doubt : Lime, which has been slaked and mixed with sand, becomes hard and consistent when dry, by a process similar to that which produces natural stalactites in caverns. These are always formed by water dropping from the I'oof. But, when the small drop of water comes to be exposed to the air, the calcareous matter contained in it begins to attract carbonic acid from the atmosphere. In proportion as it does so, it also begins to separate from the water, and to re-assume its native form of lime-stone or marble. When the calcareous matter is perfectly crystallized in this manner, it is to all intents and purposes hme-stone or marble of the same consistence as before. If lime, in a caustic state, be mixed with water, part of the lime will be dissolved, and will also begin to crystallize. The water which parted with the crystallized lime will then begin to act upon the remainder, which it could not dissolve before ; and thus the process will continue, either till the lime be all reduced to an effete, or crystalline state, or something hinders the action of the water upon it. It is this crystallization which is observed by the workmen when a heap of lime is mixed with water, and left for some time to macerate. A hard crust is formed upon the surface, which is ignorantly called froslling, though it takes place in summer as well as in winter. If, therefore, the hardness of the lime, or its becoming a cement, depends entirely on the formation of its crystals, it is evident that the perfection of the cement must depend on the perfection of the crystals, and the hardness of the matters which are entangled among them. The additional substances used in making of mortar, such as sand, brick-dust, or the like, serve only for a purpose similar to what is answered by sticks put into a vessel full of any saline solution ; namely, to afford the crystals an opportunity of fastening themselves upon it. If, therefore, the matter interposed between the crystals of the lime is of a friable brittle nature, such as brick-dust or chalk, the mortar will be of a weak and imperfect kind ; but, when the particles are hard, angular, and very difficult to be broken, such as those of river or pit-sand, the mortar turns out exceedingly good and strong. That the crystallization may be the more perfect, a large quantity of water sboiud 28 PRACTICAL MASONRY. be used, the ingredients be perfectly mixed together, and the drying be as slow as possible. An attention to these particulars, and to the quality of bricks and stones, would make the buildings of the moderns equally durable with those of the antients. In the old Roman works, the great thickness of the walls necessarily required a vast length of time to dry. The middle of them was composed of pebbles thrown in at random, and which, evidently, had thin mortar poured in among them. Thus a great quantity of the lime would be dissolved, and the crystal- lization performed in the most perfect manner. The indefatigable pains and perseverance, for which the Romans were so remarkable in all their undertakings, leave no room to doubt that they would take care to have the ingredients mixed together as well as possible. The conse- quence of all this is, that the buildings formed in this manner are all as firm as if cut out of a solid rock ; the mortar being equally hard, if not more so, than the stones themselves. 59. Water-Mortars or Cements. — The cementing materials are either found ready com- bined in certain kinds of stone, as in the case of Roman cement ; or the effect is produced by mixture, as when we mix the lime of poor lime-stones with Dutch terras. The natural com- bination is, however, by far the best ; and it is only in cases where the other can be obtained at a much less expense, that we advise it to be resorted to ; but, for such cases, we propose to describe the best compositions now known. GO. Roman Cement is made from the kind of stones called clay-balls.* The best stone contains about 60 per cent, of carbonate of lime, and 8 or 10 per cent, of protoxide of iron, the rest being silex and alumine nearly in equal parts. The inferior stones contain peroxide of iron, and often soluble earthy and alkaline salts. Stone of the best kind is pro- cured on the coast of the Isle of Sheppy, and from the alum-shale on the coast of Yorkshire, near Whitby. Stone of an inferior quality is procured near Harwich, and other places on the coast of England, and at Boulogne, in France. The stone is, after being broken to a proper size, slowly calcined in kilns or ovens, and then it is ground to a fine powder, of a light snufF- colour, when the stone is good ; and of a deeper, approaching to a burnt-umber brown, when the quality is inferior. The powder should be kept perfectly dry till it is to be used ; and, in order to use it, mix it with not less than an equal portion, by measure, of dry, clean, and sharp, river-sand ; then add as much clear water as will form it into a stiff paste, but not more ; and the whole that is so mixed must be used before it begins to set, which, with good cement, happens in about fifteen minutes from the time of adding the water ; but, in cements very fit for building, the setting may not be commenced in less than half or three-quarters of an hour. When the setting begins, all the moisture on the surface disappears, and the cement feels dry and warm to the touch, and hardens ; the hardening continues for some months, and is increased by frequent wetting the work, in cases where it has not to be exposed to water immediately on its being set. A coat of this cement is impervious to water, and it is therefore most extensively used for lining cisterns, tanks, reservoirs, &c. • They arc by some called teptaria, from being generally divided by thin eepta of carbonate of lime ; and by other, tudns helinnnfii MORTARS AND CEMENIS. 29 61. Roman Cement may be used alone, but it does not become so hard and durable, as when it has a proper quantity of good sand mixed with it. A mixture of Roman cement and common mortar should never be made, for their setting properties depend on different combinations, and which interfere with each other when acting in the same mass ; and the best mortar and best Icement may be both rendered worthless by mixture. In using cement, the more expeditious the workman is in his operations the better ; and when once setting has commenced, the work should be no further disturbed. If the setting take place too rapidly for the nature of the work, let the cement, in powder, be spread out so as to expose a large surface to the air in a dry place; in this manner the time of setting may be extended according to the time the powder is exposed, and though the quality of the cement is injured by the process, it is not so much destroyed as by working the cement after its being partially set. 62. Puszolana Mortar. — An excellent mortar for water-works is formed by combining the lime of poor lime-stones with the earth, called puzzolana, which is procured in Italy. The lime-stones adapted for this purpose are the blue lias of Somersetshire, the clunch of Sussex, and the hard gray chalk of Surrey. Smeaton used the lime of the lias procured at Aberthaw, in Wales, for the Eddystone light-house ; the proportions as under — Kind of Mortar. Lime in Powder. Puzzolana. CIcaD Sand. No. I. Eddystone Mortar 2 bushels. 2 bushels. 2. Stone Do. 2 1 I bushel. 3. Do. 2d sort 2 1 2 4. Face Mortar 2 1 3 5. Do. 2d sort 2 \ 3 6. Backing Mortar 2 i 3 — — Smeaton remarks, that mortar, of the proportions of No. 1, will, in twelve months, acquire the hardness of Portland stone, when under water ; and the others will, in time, acquire a stony hardness, if the materials have been thoroughly mixed and well beaten together. An article, called British puzzolana, has lately been manufactm-ed, but it does not possess the same pro- perties as the foreign kind ; and, indeed is rather a substitute for sand than for the true puzzolana. 63. Terras Mortar, is also very good for water-works ; it is composed of an earthy material called terras, found near Andernach, in the department of the Rhine and Moselle, which is mixed with any lime of a nature similar to the blue lias. Terras is much used by the Dutch for their sea and canal works, and it has the singular property of forming stalactitical excres- cences at the joints of the work. Smeaton employed it in the following proportions, according to the nature of the work, No. 1 . being the best quahty : — 30 PRACTICAL MASONRY. Kind of Mortar. Lime in Powder. Terras. Ciran Sand. No. 1. Terras JNIortar ...... 2 bushels. 1 bushel. ii. Do. 2cl kind 2 1 1 bushel. 3. Do. Sdkind 2 1 2 4. Do. 4th kind 2 1 .S 5. Backing INIortar 2 | ;3 The customary allowance of beating for terras-mortar is a day's work of a man for every bushel of terras. 64. When neither Roman cement, puzzolana, nor terras, can be procured, except at great expense, then we may have recourse to calcined iron-ore, scales from smith's forges, calcined basalt, clay, and other substances, containing a considerable proportion of protoxide of iron. Lime may also be improved by peculiar treatment in burning, for it appears that even common chalk-lime acquires a setting property resembling that of the lias-lime, bv being long exposed to a certain degree of heat. G5. All limes fit for water-cements require to be ground to powder, and the finer the better. If these limes be slacked, the setting property is partially destroyed ; and it is important that no more mortar should be made up at once than can be used within a few hours. CHAPTER III. OF THE CONSTRUCTION OF FOUNDATIONS. 66. A SUBSTANTIAL foundation is of the first importance in masonry, as without it no work can be durable ; and yet its construction is usually intrusted to the carpenter and bricklayer : the former for piling the inferior, soft, or marshy grounds ; and the latter for raising the wall with little or no masonry to the level of the ground. Planking consists in bedding strong boards of oak or fir, of the whole length and breadth of the foundation : those of oak not less than three inches, and of fir five, in thickness ; and they are sometimes scorched all over, previously to being laid down; but many dilapidationii having been occasioned by the decay of planks, the use of them has, by judicious architects, been lately abandoned ; and large stones, set in cement, used instead. 67. Piling is had recourse to, where the magnitude of the superstructure requires that a more solid stratum of earth should be pierced for its support. The piles, which are forced into the CONSTRUCTION OF FOUNDATIONS. 31 earth, are made of fir, oak, &c., usually about nine or ten inches square. Their length is ascertained by boring the ground the ends of the piles are cased or shoed with pointed iron, and the tops surrounded with a hoop of the same metal. The machine for driving these piles consists of a frame of wood, braced by strong pieces of timber, and secured by ledgers and feet; with a cast-iron wheel at the top, about eighteen inqhes in diameter, and fluted on the outside for a rope, or chain, to move in. This rope, or chain, is attached to the axis of a heavy iron beater, called the ram, which, for general use, weighs about five or seven hundred weight. This ram slides sometimes in grooves, in the upright frame, and often on the frame of the upright. A ladder is attached for adjusting the chain, and oiling the machine. It is worked by twenty or more men, each taking hold of a rope for that purpose, and thus raising the beater up and down in the frame. When many piles are to be driven, double sets of men to work the beater alternately will be necessary. The piles are driven as near together as may be considered proper to support the building, and the tops sawn off level, and the intervals filled up, by the Romans with charred substances, and by us with chalk, stone, and rubble ; and the tops planked over to receive the stone-work. In works exposed to water, the base is encircled by plank-piling ; these piles are all grooved on their opposite sides ; and, when driven close to each other, a tongue is forced between to bind the whole together, so as to produce a close chain of wooden piling, from one end of the foundation to the other. 68. Some architects have not deemed either planking or piling eligible for foundations, within infirm or swampy grounds ; and have, therefore, had recourse to a cradle of oak, or fir, in quartering, strongly framed and braced together in bays, and in lengths of from five to ten feet, and of widths proportionate to the weight of the superstructure : these frames are again covered over by cross-pieces, or joists, and the whole bedded firmly on the ground, and filled up flush with brick or stone, bedded in water-cement. (See art. 59, &c.) The foundation of brick or stone walls, laid on this, has been found safer than planking ; because, if the quarters of the cradle should decay, the connected work between would still remain united, and conse- quently the sinking of the building would be regular, though not altogether prevented. 69. The foundations of Bridges are generally laid dry at the piers, by the water's being, for a time, turned into a new course, or by erecting a cofler-dam. A coffer-dam consists of a double chain of piles, driven into the ground, at a sufficient distance from the intended pier, to admit the work's being conveniently proceeded in ; when the piles ai-e all firmly fixed in the earth, strong horizontal beams are framed and bolted to them with braces to stiffen tjie inter- mediate parts ; they are then finally planked inside and out, so as to form a complete case. The void between each casing is then filled with loam or clay, so that very little water can percolate, and what does get in is removed by pumping. A more ingenious method has, how- ever been practised. It consists of forming a strong grating of timber, covered with planks, 32 PRACTICAL MASONUY. which at once forms a floating-raft, and the floor upon which the stone pier is to be erected the pier built on the raft is composed of stones, amply secured, and rendered, by cement, water-tight ; and the whole is so arranged as to float upon the water till it has advanced in height ; so that, if sunk, it should be above low-water mark, or higher, as found expedient. This levity is obtained either by attaching the raft by ropes to vessels, or by the pier's being worked with vacuities sufficient to render it specifically lighter than an equal bulk of water. The pier is sunk either by letting the water into the vacuities, or by loosening the ropes ; but the bed of the river should be previously prepared for its reception, by drcdging-machines. Should the bottom of the ground prove not to be level, the pier must be raised by pumping the water out, or by means of the machines in the vessels, and the ground then satisfactorily levelled. In the erection of Westminster Bridge, M. Labelye erected the piers in caissons, or water- tight boxes ; the bulk of the box, though loaded with the pier, producing a mass specifically lighter than an equal bulk of water : after each pier had been erected, the sides of the box served again for boxes of other piers ; the pier was sunk, and raised as above. Similar caissons were likewise used in erecting Blackfriars' Bridge. Till of late years the foundation of bridges was erected in the following manner : The piles were driven into the bottom of the river, in the site of the intended pier, and then cut oflT a little below lov.'-water mark ; the interstices being filled with stone and strong cement ; on these piles a grafing of timber was laid, boarded with thick boarding, and thus was formed the floor for the intended pier. The work was then continued, at low-water This is a very simple method, requiring no machine beyond a pile-driving engine. The foundations of the piers of London Bridge, as appeared from that which was removed, when the two small arches were converted into one, was composed of a quadruple row of piles, driven in close together on the exterior site of the pier, and forming a case to receive the stone and cement. So soon as the exterior piles were taken away, the force of the water cleared away the remainder, so that it could not be ascertained whether there were piles in the heart of the pier. To protect the piers of this bridge, sterlings were constructed round them. A sterling consists of an enclosure of piles driven close together into the bed of the river, and secured by horizontal pieces of timber, bolted by iron to the tops of the piles ; and the void within, to the piling of the pier, filled with chalk, gravel, stone, &c., so as to form a complete defence to the internal piling, upon which the stone piers are erected. CONSTRUCTION OF WALLS. 33 CHAPTER IV OF THE CONSTRUCTION OF AVALLS. TO. The antients used several modes of constructing Walls, in which more or less masonry was always introduced. They had their recticular or reticulated walls, and also the inceriain : of these, the recticuiative kind {plate XIV, fig. 2,) was esteemed the most handsome ; but the joints are so ordered, that, in all parts, the courses have a regular position ; whereas, in the incertain, (Jig. 1,) the materials rest irregularly one upon another; and are interwoven together, so that they are much stronger than the reticulated, though not so handsome. In the kind of wall represented in Jig. 1, the courses are neither level, nor the upright joints ranged regu- larly or perpendicularly to each other in the alternate courses, nor in any other respect corres- pondently, but uncertainly, according to the size of the stone employed. Stones are so arranged in ordinary rubble walls, in which all that is regarded is, that the upright joints, in two ad- joining courses, do not coincide. Walls, of both sorts, were formed of very small pieces, with a sufficient quantity of good mortar, which added greatly to their solidity. To saturate, or fill up, a wall with mortar, is a practice which ought to be had recourse to in most cases, where small stones, or bricks, admit of it. It consists in mixing fresh Hme with water, and pouring it, while hot, among the masonry in the body of the wall. The walls called by the Greeks Isodomum, {fig. 4,) are those in which all the courses are of an equal thickness ; and Pseudo-isodomtim, {fig. 3,) those when they are unequal. Both these walls are firm, in proportion to the compactness of the mass, and the solid nature of the stones, so that they do not absorb the moistness of the mortar too rapidly ; and, being situated in regular and level courses, the mortar is prevented from falling, and thus the whole thickness of the wall is united. 71. In the kind of wall called emplection by the Greeks, {fig. 6,) the faces were built with dressed stones, with the other sides left as they came from the quarry ; and the two faces were secured by occasional bond-stones. This kind of building admits of great expedition, as the artificer can easily raise a case, or shell, for the two faces of the work, and fill the intermediate space with rubble-work and mortar. Walls of this kind, consequently, consist of three parts, with very imperfect connection ; two being the faces, and the other a rubble core in the middle : but the great works of the Greeks were not thus built, for, in them, the whole intermediate space between the two faces was constructed in the same manner as the faces themselves (fig. 5) ; and they, besides, occasionally introduced diatonos, or single pieces. A, A, extending K 34 PRACTICAL MASONRY. from one face to the other, to strengthen and bind the wall. These different methods of uniting the several parts of the masonry of a wall, should be well considered by all persons who are intrusted with works requiring great strength and durability. The existing examples of Roman emplection, with partial cores of rubble-work, or brick, sufficiently prove its durability when united by excellent mortar ; of the Greek method, wliich was worked throughout the whole thickness of the wall, in the same manner as the facings or fronts, their temples, now existing, testify the solidity. 72. The stone in the walls of modern buildings is sometimes used for ornament, or covering of the brick-work, but is generally combined with solidity. In London, the thickness of walls is regulated by a specific Act of Parliament ; but, to prevent dilapidation, it is often necessary to strengthen the walls beyond what the law requires, as this law was framed only as a pro- tection from fire, and was only for brick-walls. The thicknesses of walls should be regulated according to the nature of the materials, and the magnitude of the edifice. Walls entirely of hewn stone may be made one-fifth thinner than those of brick ; and brick-walls, in the base- ment and ground-stories of buildings of the first-rate, should have the facing-stones rusticated, to prevent their splitting ; a circumstance which has been too much disregarded by our present builders. 73. A wall should be reduced in thickness as it rises, for the same reason that a column is diminished ; and if the wall be a part of a house, it should be reduced in a still greater degree, since the load, wliich is to be supported by it at different parts of its height, is usually much varied, by the weight of the floors, and of the contents of the apartments; such walls are reduced by internal offsets, the external face of the wall having only a slight inclination, called battering, of about an inch in a height of 10 feet. The obliquity of the external surface of a wall may, however, become objectionable, by promoting the growth of moss and weeds. In building a wall, the first precaution that is required, is to dig deep enough to ascertain the nature of the ground ; tile next, to lay a sufficiently extensive and firm foundation ; and it has been very properly recommended that where walls are wanted, the ground should be well examined before the foundations of a house be laid, in order to ascertain the qualities of the different strata which are to support them. 74. The disposition of the stones, or bricks, is of much importance ; the strength of a wall or to\^er is obviously greatest when all the surfaces are either horizontal or vertical ; for if they be oblique, they must have a tendency to slide away laterally, and the wall must be very liable to crack : hence the reticulated walls, sometimes employed by the antients, of which all the joints were oblique, possessed but little durability {art. 70). If the materials be put together without regular joints, the parts in contact tend to separate the walls by their action on each other; occasionally, as in the case of piers, or quays, this circumstance may be of some advantage in opposing external pressure, and uncoursed or rubble-work may be used ; but no wall, composed of different kinds of masonry, is so strong as when wholly of one kind. CONSTRUCTION OF WALLS. 3o It is not unusual to make the external face of an inclosing wall of hewn stone, and the internal part of the wall of rubble-work ; but these settle unequally, and where the walls support much weight dangerous cracks and bulges take place. The walls of St. Peter's Church at Rome show some serious defects arising from this cause. 75. It is not of much advantage in walls to use stones which have a greater length than three times their thickness; otherwise, from the difficulty of bedding them equally, they are liable to break in the wall ; hence proper crossing of the joints with stones that are not so long as to have the risk of breaking, is a better method. . In the angles and piers of a building, it is most necessary to attend to strength, both by bond and good-sized stones. 76. We have given the pressure which stones will bear with safety, and it will be useful to add the pressure actually borne by the principal supports of some of the most celebrated buildings in Europe. NAMES OF THE BUILDINGS. Pressure on each superficial foot. The pillars of the Gothic church of All Saints at Angers 86,000 lbs. The pillars of the dome of the Pantheon at Paris, the lower part of which are of Bagneux stone- - - 60,000 — The pillars which support the tower of the Church of St. Mary at Rome 60,000 — The columns supporting the roof of the Basilica of St. Paul at Rome — 41,000 — The pillar in the centre of the Chapel-house at Elgin, which is of red- sandstone *0,000 — The piers which support the dome of St. Paul's in London . 39,000 — The piers which support the dome of St, Peter's at Rome 33,000 — The pillars supporting the dome of the Invalids at Paris 30,500 — The pressure on the key-stone of the Bridge of Neuilly (see jilate XIX, fig. 1) has been estimated at 1 8,000 — The Bagneux stone should not, it appears from experiment, be loaded beyond the above, even on the supposition that the force is vertical, and in the axis of each pillar ; hence, any irregularity in these respects renders the construction hazardous ; and we are not surprised to find that the stones split, and exhibited manifest signs of being overloaded. Of Wharf, Dock, and Revetment Walls, S^'c. 11. Walls have frequently to be built to resist the pressure of fluids, or of earth acting against their sides, and sometimes to resist the force of the waves of the sea ; they require, therefore, to be most firmly built, and of a form and massiveness adapted to the object. In all these species of walls, it is the stress of earth against them that has chiefly to be considered, except in the case of sea-walls. 36 PRACTICAL. MASONRY. 78. Tlie most simple kind of wall is a rectangular one {fig. 1, plate W .) ; but an equ,.l degree of strength, with less material, is obtained by giving it an exterior slope, as fig. 2. For fortification, ^'auban used to make this exterior slope r of the height, but the joints perish, and mosses grow on and destroy walls having so much slope, hence later engineers make it less, i of the height is commonly used, but -f or -vs is, in our opinion, quite sufficient. To gain an equivalent in strength, we would adopt the countersloping form. Jig. 3, or its equi- valent, Jig. 4. In some instances, the bulk of the wall has been increased, by leaving spaces in the work to be filled in with rubble, gravel, &c., as in Jig. 5 ; and in others, sloping walls have been built as in Jg. G ; and the latest change is to make the walls curved, as in Jig. 7. The latter are very appropriate for docks and basins, but are not so fit for dry works. 79. The strength of any of these walls is materially increased by adding counterforts on the side next the earth, of a breadth about equal to the mean thickness of the wall, and about three times that thickness apart, (Jg. 8,) and their thickness about three-quarters of their breadth. The strength of the wall should be such, that, were it deprived of counterforts, it would be sufficient to resist the pressure of the earth. SO. In order to consider the strength of walls to support earth, &c., it should be understood that the bank of earth itself may be sloped so that it will stand, and let this slope be ac (.Af?- Ij plate XV.) ; it is called the natural slope of the earth; and the angle it forms with the horizon is called the angle of repose. Now it is evident, that the triangular prism of earth sustained is abc; but, within that triangle, there will be found another, dab, which, though it be less in weight, has more force to overturn the wall, because it is a more acute wedge ; the line da then is the line of fracture, and it has been shown' by Mr. Tredgold, that, when the forces are found in a horizontal direction, the pressure on a foot in length, tending to overturn the wall, is — A'S „ , . „ PSc- -^ c'-\ and, Its enect, — — • Where h is the height of the wall in feet, s the weight ot a cubic foot of the earth, and c' the square of the cotangent of half the angle of repose of the earth. 81. In treating of the resistance of walls, we shall omit the effect of the coherence of the mortar, and of the earth, because a wall generally has the whole stress upon it before the mortar be set, or the earth has become compact ; and, also, when a wall oversets, it cannot be sustained by a mere arris, but the angle would crush and shorten the leverage the weight of the wall acts with, the amount of this shortening mav be estimated at -5: of the leverage of the wall at the base. Now, in all walls, the height h in feet, multiplied by t, the mean thickness in feet, and by MI, the weight of a cubic foot of the masonry, will give the weight of a foot in length ; that is, /(/(<; = the weight; and the leverage is equal to the distance nt therefore, — — ^ = the resistance of the wall, and making it equal to the pressure of the earth, or -^^ — = -^- ; we have t — he ^ /_£_. \/ 6 urn CONSTRUCTION OF WALLS. 37 82. For rectangular stone walls, {fig. 1,) to support common earth, n = |;w=I30;*=96 lbs., and c'=-'5Q\ therefore, tzz'Sh, or the thickness of the wall in feet should be three-tenths of its height in feet. 83. For sloping walls, (fig. 2,) with a slope of ^ih , then n = .6043, and t being the mean thickness, the conditions being in other respects the same as the last, t = "ST h. 84. If the wall have ofiFsets at the back, (fig. 4,) it will be proper to make the weight of the mass, a b ef, of equal weight to a rectangular wall, found by art. 82 ; but a sloping back has much more stress upon it. 85. In a sloping wall, (fig. G,) if the slope ge he m times the mean thickness of the wall, then n = "*"; and t = he \ / ; — r-Ts ; and, when the slope is equal to the mean thickness, 2 \' 5 «c (nt + 1 ) for common earth and stone walls, we have < = '215 A, or the thickness of the wall, measured horizontally, should be "215 times its height. 86. A wall ought to be so constructed that the resultant of the pressures should every where fall within the thickness of the wall ; and a careful investigation of this problem will show that a curved wall of a particular form is the best possible. If a plain wall be not of sufficient thickness to admit the curve to be drawn within it, there will be a tendency to bulge at one-third of the height from the base ; hence, for all sloping walls, we should give the preference to the curved forms. (See fig. 7, 9, and 10.) 87. Where walls have to resist the pressure of water, or other fluid matter not materially heavier, the general rule becomes t — h */ "' := ^'V/ '~~~' For a common stone rectangular wall, (fig. 1,) w = 130 lbs., and « = i, therefore t — "44 // ; or the height of the wall multiplied by "44, is equal to the proper thickness. 88. If the wall has a slope of one-sixth, (as fig. 2,) then the mean thickness should be four- tenths of the height. 89. The preceding rules are so easily applied, that we have not added tables ; but, in prefer- ence, describe some of the most important works of this kind that have been executed. In revetment walls, for fortification, the celebrated Vauban always used an exterior slope of \, and made the wall 5t feet at the top, and the back vertical. He made diminished counterforts at from 15 to IS feet apart; for a wall ten feet high the counterfort had a length of 4 feet, and a breadth of 3 feet at the root and 2 feet at the tail ; and for every additional foot in height he added 3"6 inches to the length, and '8 in. to the breadth of the counterforts. The exterior slope is less in later works. 90. Of Dock-walls, there are many examples, chiefly of the curved form, which was first used by Jessop, for the West-India Docks. The height of the walls of which are 29 feet ; the face- curve is described by a radius of 72 feet, from a centre level with the top of the wall, (see fig. 9,) the thickness of the wall is 6 feet, and uniform, and the counterforts 3 ft. by 3 ft., and I. 38 PRACTICAL MASONRY. 18 feet apart. As the slope is, in this case, very nearly the same as the thickness of the vail. the rule {art. 85) ought to apply, which gives G*2 feet for the mean thickness. Where less than the mean thickness is sufficient for resisting the wear and tear at the top of the wall, there will be considerable advantage in increasing the thickness of the base, as has been done by Mr. Walker, at the entrance-basin of the East-India Docks (see fig. 10) ; the wall of which is 22 feet high, 1\ feet at the base, and 3| feet at the top ; the counterfortt^ 2} feet wide, H feet at the top, and 1\ feet at the bottom, the backs of them being vertical. 91. As an example of a sea-wall, we have given the section of one built at Liverpool in 1806 {fig. 11); the height is 30 feet; the base 15 feet, and top 1\ feet, with a front slope of one in 12 ; the counterforts are 15 feet wide, and 36 feet from centre to centre. But, for a wall to defend any place from the force of the ocean, a long slope, in form resembling the sea- beach, only rising more rapidly, should be made. The section of the celebrated Breakwater, at Plymouth, is shown, {fig. 12, plate XV,) but it is a straight-lined figure, and wants a connected surface next the Channel, to render it an effective means of resisting the force of the waves. It is formed by dropping large masses of stone, H to 2 tons in weight, in such a manner as to obtain the figure shown in the section. There was 4,233 feet in length finished in 1825. 92. In order to secure walls, by completely uniting the masses of stone together, dove-tailing, dowels of hard stone, or of cast-iron, cramps run in with lead, and various other methods are used; of these, the best is locking the stones by dovetail-joints, {plate XWW, fig. Z,) and fiUing them with cement (see urt. 60). CHAPTER V. OF THE CONSTRUCTION OF BRIDGES, &c. 93. The construction of Bridges is an art of immense importance ; as it largely contributes towards the improvement of that system of internal communication which diffuses the benefits of industry and trade throughout the British Empire. In the theory of the construction of bridges, mathematical science, in all its dignity, is exer- cised, and to the enlightened mechanical mind, it has, therefore, always been a favourite sub- ject. To him especially who delights in ranging the delightful truths of geometry, and in employing the higher powers of analysis, and who feels, as he contemplates them, that enthu- siastic emotion which poets and philosophers alone can know. There are few operations of art to which the man of science can apply his speculative principles more successfully than to the CONSTRUCTION OF BRIDGES, &C. 39 building of bridges ; theory, however, did not at one period keep pace with practice, but now, through recent improvements, science will have a potent influence in directing the operations of the mechanic, and the carpenter and builder will lean, with full confidence, on the deductions of the mathematician. The construction of bridges is a subject in itself highly interesting; from the difficulty attending their erection, and the ingenuity displayed, both have much power over a contempla- tive mind, and in common ones excite astonishment. ^Vhat, indeed, can be more striking than to see a huge mass of ponderous stones, suspended, by the mutual balance of its parts, over the mightiest river in the world ? and, so far has the intrepidity of the engineer carried him, that bridges are thrown over arms of the soa ; and here, also, has success been complete. The boldness of form and grandeur of effect is not a greater source of astonishment than the neat- ness and elegance of the structures. Holding at nought the danger attending their labour, the workmen must show their skill in preparing, placing, and embellishing, their materials, as if ornament, more than utility, were the object of their wishes: but, generally, it will be found that, while ornament is obtained, utility is the main object of the design, and that the stones are so artfully constructed and laid together, that, in combination, they may give mutual sup- port, and the heaviest load may pass over in perfect safety. The construction of a perfect bridge is, however, a very complex operation; it could not be accomplished by a rude and unintelligent people ; and we find, in the history of bridges, that the erection of arches did not always correspond with the progress of other arts, even where an advantageous intercourse subsisted- 94. The SIMPLEST bridge is obviously that which is composed of a single tree, thrown across a small stream, whose width is not too great for the length of the tree ; but, when this is the case, a higher effort of inventive power is necessarj', and this is also soon supplied by stretching another tree from the opposite side, and fastening them together in the middle, by some means or other, such as twisting the branches. This sort of bridge must frequently occur by chance. Mr. Park found such in the interior of Africa. 95. The next step is not much more complex ; for the process of twining ropes of fibrous bark or leathern thongs is very simple ; and we have only to connect together and stretch as many as may be necessary, from one tree to another, on the opposite banks of the stream, and cover them so as to answer the purpose required. Bridges of this kind have been constructed in South-America and in India, and the principle has been improved upon in Britain by using chains of iron instead of rope or leather ; the first bridge of the kind was thrown across the Tees at Winston, and the most splendid is that which has been erected, by Telford, over the Straits of Menai for the mail-road to Holyhead, the span of the bridge being .'560 feet; and the abutments and towers for fixing the chains are fine specimens of masonry. (See plate XX.) A suspension bridge of this kind has just been completed over the Thames at Hammer- smith. The suspension towers are 400 feet apart, built of hewn stone, and designed as archways 40 PRACTICAL MASONRY. of the Tuscan order, the towers are 22 feet thick, and of the breadth of the bridge, and rise 48 feet above the roadway ; they have the singular and evident defect of having no passage for foot passengers. The retaining piers on the shores are built of brick and stone firmly cemented together, with tunnels for the chains to pass through. 96. The next mode of forming bridges is to construct piers of stone, at such a distance from each other, as to admit a beam of timber, or a long single stone, to stretch over the width of the stream. This, if the water be shallow, is a very simple operation ; for the piers may be built of rough stone without mortar, and such a process would soon present itself to a rude people. But, if the stream be at all times rapid and deep, and the piers built of hewn stone laid with mortar, we may infer that the people who formed such a structure were well acquainted with the useful arts ; for it is clear that the stones must previously have been quarried and hewn, and before a proper foundation for the pier could be had, the union and experience of various arts were required : hence, then, we conclude that the society in which a work of this sort, of any considerable magnitude, is accomplished, is far advanced in civilization, and has the command of much well-regulated labour. 97. With respect to the mode, now commonly adopted, of constructing arches between piers of stone, the Chinese pretend that they erected bridges in this manner many centuries before arches were known in Europe, or to the inhabitants of any part of the western world : but, when we consider the many specious claims that this empire has held forth for the high anti- quity of its improvements and inventions, we may perhaps feel but little disposed to credit the assertion. In Egypt and in India, countries of the highest antiquity, and which have produced many useful inventions, both in science and in art, the construction of the arch appears not to have been known ; for the temples of the one, and the tombs of the other, were produced by cutting matter away in the manner of sculpture : and further, in the antient works of Persia and Phoe- nicia no trace of an arch can be found. The Greeks created a school of architecture and sculpture, and carried their knowledge very far in these departments, yet even they have but an obscure claim to the knowledge of the arch. It is, at least, certain that they never used it externally in their temples, much less in the construction of bridges. It is to the Romans, then, that we are indebted for this useful application of a great prin- ciple in architecture ; but there is no certainty as to the time when it was first practised. It is asserted, by some, that the Romans derived their knowledge of the arch from the Etruscans ; but, if this were admitted, the first knowledge of the art is at least very intimately connected with Greece, for we believe it is not disputed that the Etruscans were a colony of Dorians. But, however doubtful may be the claim to the invention of the arch, we know, from history, that the Romans were the first to apply it to useful purposes ; the oldest known example being the Cloacas jNIaxima of Rome, and it was soon afterwards used in forming aqueducts for convev- CONSTRUCTION OF BRIDGES, &C. 41 ing water to cities, erecting bridges over rivers, vaulting temples, and the like, and in erecting monuments to record the exploits of their heroes. 98. Having thus described the rude bridges of uncivilized nations, and shown that the Romans were the first to perfect and bring the arch into common use, we shall pass over the description of most of the massy structures of this kind that have been reared in other coun- tries, and confine ourselves chiefly to those which are conspicuous in our own kingdom, be- ginning with the old bridge of London. This bridge was originally begun in the year 1176, by a priest, called Peter, curate of St. Mary Colechurch, a celebrated architect of those times, and occupied thirty-three years in building : but this period will not appear surprising, when it is considered that it was built over a river in which the tide rises, twice every day, from 13 to 18 feet. The bridge at first consisted of twenty aixhes, and houses were erected on each side of the roadway ; but, in 1758, the middle pier was taken down, and the two adjacent arches were converted into one, the span of which was seventy-two feet ; its breadth forty-five feet, and the houses along each side of it were removed. The remaining arches were very narrow, and the piers inconveniently large, being from fifteen to twenty-five feet in thickness. The passage over the bridge was very commo- dious, but in other respects there was nothing to recommend it, and the fall of water under it, from the obstruction of the piers and sterlings, with the difficulty of preserving the bases of the piers from failure, rendered it necessary to build a new bridge. 99. The foundation-stone of Westminster Bridge was laid on the 24th of January, 1739, by the Earl of Pembroke (a nobleman distinguished by his taste in architecture), ^^'estminste^ Bridge is 1220 feet in length, and 44 feet in width, having a commodious foot-path, seven feet broad, on each side. It consists of thirteen large, and two small arches, fourteen intermediate piers, and two abutments. (See plate XVI.) The length of each abutment is 76 feet ; the opening of the smaller arches is 25 feet each ; the span of the first of the larger arches, at each end, is 52 feet ; of the next, oQ feet ; and so on progressively, increasing four feet at a time, to the centre arch, of which the span is 76 feet. The piers of the middle arch are each 17 feet thick, containing 3000 cubic feet, or nearly 200 tons of solid stone. The others decrease equally one foot on each side; every pier terminating with a saliant right-angle against the stream. The arches are semi-circular, and spring from about the height of two feet above low-water mark, leaving a free water-way of 870 feet. The size and disposition of the mate- rials are such, that there is no false bearing, nor a false joint in the whole structure, but they are not of a durable kind. The foundations were laid by means of caissons, (see art. 68,) and one of the piers sunk, owing to being undermined by removing sand out of the river. The bridge was opened for passengers in 1750, and cost ^^2 18,800. The engineer was M. I,a- belye, and Mr. James King directed the execution. 100. About ten years after Westminster Bridge was completed, another was begun, at a mile lower down the river, known by the name of Blackfriars' Bridge ; designed by M 42 PRACTICAL MASONRY Mr. Robert Mylne : it consists of nine arches, of an elliptical form, of which the middle one is one hundred feet in span, and the breadth across the bridge is forty-three feet six inches. (See plate XVI.) The whole length of the bridge, from shore to shore, is 995 feet, the breadth of the carriage-way is 28 feet, and that of the foot-path, seven feet, on each side. The centre arch is 100 feet span, and the four arches on either side decrease gradually towards the shore, being 98, 2Z, 83, and 70 feet respectively, leaving a water-way of 788 feet. The upper surface of the bridge forms the segment of a very large circle, guarded on each side by an elegant open stone balustrade. Over each pier \& an open recess, or balcony, supported by two Ionic columns, with pilasters, which rest on a circular projection from the pier above the high-water mark. Each extremity of the bridge is rounded off to the right and left in the form of the quadrant of a circle, which renders the access commodious and agreeable. The arches being elliptical, and of wider span than those of Westminster, the bridge, of course, has a lighter appearance, but the Ionic columns are not in good taste ; nevertheless it is a work of very great merit, and will stand a comparison with any other constructed in the same age. It was finished in \0\ years, and cost ^£152,840. It will be an advantage, before we proceed further with the description of bridges, to give the most important points of the theory of the art, in order that the reader may see its applica- tion more clearly. Tlieory of Bridges. 101. In the Theory of Bridges we have first to examine the nature of equilibrium and sta- bility; as, by a proper knowledge of, and attention to, this important subject, the beauty and strength of bridges are to be secured. The celebrated Dr. Hook proposed, as a proper form for an arch, the curve into which a rope or chain would arrange itself, if suspended at the two extremities by pins or nails fixed in a wall ; this curve is commonly called the catenarian curve, the properties of which have been investigated by different mathematicians. 102. If a chain, or string of beads, equal in size and weight, be suspended at its extremities by two pins or nails, it will form itself into the curve line called the catenary. Suppose that this curve could be turned steadily round, without change of form, till it obtained a position in which the lowest point became the highest in the same plane ; then all the beads in the arch would, by gravity and equal pressure, retain the same position ; and, consequently, the arch formed will be the catenary. This arch, however, would support no weight, a mere breath being sufficient to destroy the equipoise. 103. But, if we suppose the beads, in place of being small globes or spheres, to become pieces of a cubical form, equal in height to the diameter of the globes, and retaining the same position, the stability of the arch would be considerable, hence we see that depth of arch gives stability. The arch is now formed of a mass of truncated wedges, arranged so that the cate- THEORY OF BRIDGES. 43 iiarian curve passes through their centres, and it is for this case the proper curve of equilibrium ; therefore, when the stones are all of the same weight and size, this cur^e is the only one proper for arches ; but, arches not being in any case in practice of this equable form and weight, but must have their haunches filled up, a level or slightly inclined roadway, and parapets, we must investigate the effect of other dispositions of the weight. 104. Suppose it be required to determine the form of an arco, of a given span and height, proper to carry a road-way of a given fonii. Let the proposed span be marked horizontally, on a vertical plane of any substance that may answer the purpose ; bisect the span by a perpendicular directed downwards, and equal to the given height of the centre of the arch-stones ; from the extremities of the span suspend a rope or chain, so that its middle pouit may be a Uttle below the point marking the intended height of the arch ; divide the span into any number of equal parts, and at the points of division raise perpendiculars cutting the suspended chain in particular points; from these points suspend pieces of chain, so adjusted that their ends may meet the Hne of road-way : and it may be observed that, as those which hang near the haunch bring it down, the crown will rise to its proper position. If the sum of the small chains has, to the large one suspended from the extremities of the span, the same ratio that the material to be filled into the haunches has to the whole weight of the arch-stones, this will be the exact form of the middle of the arch required to support the given road-way ; and, by setting off the depth of the arch equally on each side of this line, it gives the curve of the under side of the arch. 105. The curve of equilibrium is, therefore, an imaginary line, and ought to pass through the centre of the arch-stones, and not form the soffit, as the early authors on this subject have stated ; for if the curve of equilibrium touches the intrados of an arch of any kind, the com- pression at the surface must be at least four times as great as if it remained in the middle of the arch-stones, and still greater than this, if it pass ever so little out of the ring of the arch-stones in any part of the arch, for then the arch cannot stand, except by the cohesion of the mortar, which ought not to be depended on. The passage of the curve of equilibrium through the middle of each block is all that is neces- sary to insure the stability of a bridge of moderate dimensions and of sound materials, and the strength of an arch is not increased, like that of a frame of carpentry, or of a beam to support a weight by an increase of its depth in preference to any other of its dimensions ; but a greater depth gives it a power of effectually resisting a greater extraneous force from the presence of any occasional load on any part of the structure, but the magnitude of such a load is seldom very considerable, in proportion to the weight of the bridge ; the breadth of the arch increases with its weight, and must be arranged for convenience of passage, and the depth will be sufB- cient when the stress on each square foot cannot possibly exceed one-eighth part of the pressure which would crush the material used for the arch-stones, or that load the material bears with safety. (See art. 45, 48, and o5.) 44 PRACTICAL MASONRY. lOG. The pressure increases from the crown towards the abutments, and may be found for any point by drawing a line parallel to a tangent to the curve of equilibrium at that point in this manner. On a vertical line, {fig. 3, plate XIX,) take any length c 6 by a scale of equal parts, and from c draw a line parallel to the tangent to the arch at the springing, and from b draw a horizontal line, these will meet in the point a, then as ab-.ad:: pressure at the crown : the pressure at the point where the tangent is drawn. Also if ac be parallel to the tangent at the abutment, then cb : ab:: weight of the semi- arch : pressure on the arch-stones at the crown. 107. The joints ought to be perpendicular to the curve of equilibrium, for if the pressure at each joint be not exactly perpendicular to the joints of the arch-stones, it cannot be resisted without friction, and the parts may slide on each other if they be oblique to the curve : this, however, is an event not likely to occur in practice. But when the curve, representing the general pressure on any joint, passes beyond the limits of the arch-stones, the joints will open at their opposite ends, unless they be held by a very firm cement, and the structure may wholly fall, and if it continue to stand it will be in another form. 108. Having given these principles for the form, stability, and strength of an arch, it only remains to consider the effect of the arch on piers, or abutments. A pier must be considered as an increase in the weight of an arch of sufficient magnitude to cause the curve of equilibrium to fall within its base. Let the centre of the abutting joint be b, (fig. 6. pi. XIX,) and draw be a tangent to the curve of equilibrium at that point, and ba, a horizontal line, and ad a vertical line from a point d as far within the base of the pier as half the depth of the arch- stones ; then as ac : cd : : weight of semi-arch : weight of the pier, and this condition is essen- tial to the stability of the arch. lO'J. If it be an abutment, the joints should be perpendicular to the line bd, in order that they may have no tendency to slide ; and the resistance of abutments is generally much in- creased by prolonging the side walls (called wing-walls). 1 10. The practical application is rendered much easier by means of algebraic formulae. Let IV — the weight of a foot in breadth of the arch ; h — tlie whole height of the abutments or pier from its base ; = the mean thickness of the abutment or pier, the thickness at the base should be greater by half the depth of the avch-stones ; X — the height from the base to the springing ; a = the angle the tangent of the curve forms with the horizon at the springing ; s — the weight of a cubic foot of the stone-work of the pier. Then Ids zz the weight of the abutment or pier, and txian a ■=. ae\ (pi. X.IX, fig. 6;) hence txtan a:x - txtan a:: io:hts - '"^"""'^'"""^ consequently <= \ / JEl 4- txtana V ltsy,lan a — -; and, sufficiently accurate for practice, Z^^/ — ^ _1_ ian a THEORY OF BRIDGES. 45 111. Also if y = the pressure a square foot of stone bears with safety (art. 45-53), or one- eighth of the force which will crush the stone ; d its depth in feet ; and w the whole weight of the semi-arch one foot in thickness, then, j^^ — df; or fj^^ = ti = the depth of the arch at the crown, and f-r-^ ^z. d — the depth at the abutment; when the arch is of the proper figure. In the description of the plates we will show the application of these equations ; and now proceed to give a brief view of the fall of water under the arches of a bridge, it beino- necessary to pay some attention to this, in designing the edifice. 112. It is known that, if the same quantity of water, that flows in an open extended channel, have to pass through a space any way contracted, it rises above the general level ; and, conse- quently, has the velocity of its current increased. The piers of a bridge form obstacles in the way of running waters, and in proportion as they contract the channel, the water will rise above the usual level, and the rapidity of the current be increased ; but the investigation of the law of increase, agreeing to a given contraction, would occupy too much room for our present purpose, and would, also, be too refined a speculation for this work ; we shall, therefore, present two tables which may be of considerable use to men of practice, as the effect of different contrac- tions is brought at once under his view. We do not pretend to say, that the tables are complete, yet they will be found to answer many useful purposes ; and, in order that they might be as perfect as possible, we have given one for the velocity, and the other for the rise the obstruction will produce in the level of the river's surface, for a space equal to the breadth of the bridge. The depth has to be attended to, in discovering the velocity ; but we will not enter into these delicate circumstances, as the data cannot always be obtained with similar exactness. 113. We shall now give an example to show the use of the tables. Suppose it were required to build a bridge over a river, 100 feet wide, and velocity three feet per second ; but the abutments and piers together reduce the water-way to 75 feet, that is, diminishing the original width by one-fourth. Look in the upper table, opposite to 3 feet, and under the obstruction J, and 135 will be the head found; this is about 1*6 inch, and therefore is not objectionable ; and, by the lower table, the velocity under the arch will be 4*2 feet per second ; which the bottom should be capable of bearing. The effects of accidents to which rivers are liable may be discovered by the second table. — By inspection, it will be seen that, when the velocity is 10 feet per second, or above it, the power of the inundation is sufficient to carry away every thing before it, except the hardest primitive rocks, while firmly united in their natural beds. The numbers in the latter part of the table therefore show that, in fact, such contractions are impracticable. 46 PRACTICAL MASONRY. 114.. — The Rise of Water produced bij Obstructions to a Current, when they are jorMed to divide the Stream, as Piers with Pointed Sterlings, ^c. VELOCITY. DESCRIPTIUN OF RIVERS. OllSTRlICTIONS. 1 Per Second. Per Hour. Tlie Current usu- ally termed. The Bottom which just hears the ellect of such Rise. I TO i 1 i I 4 T 1 2 5 J r 4 1 Ft. In. Miles. Head of Water produced at the Obstruction, in Feet |or3 t Dull, 5 Oaze and ) ( Mud, J •0003 •0004 •0004 •0006 •001 •0014 •0033 •0067 •0162 4orO I ■f- Gliding, Soft Clay, •0011 •0014 •0017 •0023 •004 •0058 •0133 •0267 •0647 1 ilorf Smooth, Sand, ■0045 •0056 •0069 •0091 •015 •0231 •0532 •1069 •259 2 2| 5 Uniform \ I Tenors, ) Gravel, •0182 •0225 0276 •0364 •060 •0924 •2128 •4276 1-036 3 I '-12 ( Ordinary ( r Pebbles, ^ ) Shivers, ( •0409 •0507 •0621 •0819 •135 •2079 •4788 •9621 2-SSl 4 2A- r Freshes, ^ rExtraor- ) and ( C Shingle, .' Boulders 1 •0728 •0902 •1104 •1456 •240 •3696 •8412 r7ioi 4-144 5 3i-. < dinary t Floods, and Soft r Schistus,-' •1137 •1410 •1725 •2275 •375 •5775 P3200 2^672 6-475 6 4t't Rapids, r Torrents ) ^Stratified } \ Rocks, 5 r Indurat- ) •1638 •2030 •2484 •3276 •540 •8316 1^9152 3-848 9^324 10 6-?T ] and S (Cataracts) L Kocks, ) •4550 •5640 •6901 •9100 V500 2-3100 5-32 10^69 25-9 VELOCITY. DESCRIPi'ION UF RIVERS. OBSTRUCTIONS. Per Second. Ft In. Per Hour. Miles. The Current usu- ally termed. The Uottom which just hears such Velocities. Ti I T3 i 1 i * 1 1 T .1 2 i 1 4 Velocity produced at t le Obstruction, ia Feet per Second. iorS lore 1 Dull, Gliding, Smooth, 5 Oaze and? i Mud, 5 Soft Clay, Sand, •28 •56 1-13 •29 •58 1^16 •30 •60 P20 •32 •63 1-26 •33 •70 P40 -394 •787 1-575 •52 1-05 2-1 •7 1-4 2.8 1-05 2-1 4-2 2 2f j Uniform \ ( Tenors, ) Gravel, ^•27 2^33 2^40 2^52 2^80 2^75 4-2 5-6 8 4 5 2tV ( Ordinary ( r Pebbles, 1 ) Shivers, ( 3-40 3-39 3-60 3^78 4-20 4^S25 6-3 8-4 12-6 4 5 2A 3t\ C Freshes, C rExtraor- < dinary t Floods, 1 and ( ^ Shingle, ^ Boulders T and Soft > Schistus, ) 4-54 5 •68 4^66 5^83 4-80 6-00 5^04 6^30 5^60 7^00 6^5 7-875 8-4 10-5 11-2 14-0 16-8 21-0 6 4t-t Rapids, 1 Stratified ?. i Rocks, 5 6^S1 6^99 7.20 7^56 8-40 9-45 12^6 16-S 25-2 10 6t't r Torrents ) < and V (■ Indurat- ) ] ed [ 11^36 11 •ee 12-00 12^60 14^ 15^75 2\- 25-9 42-0 (Cataracts ) C Rocks, ) PRINCIPLES OF BRIDGES. 47 115. The next subject which claims our attention is the Water-breakers, or, what the work- men call Sterlings, being the extremities of the piers which meet and divide the water in its course. The preceding table supposes them to be rounded, or pointed, but if they be square and abrupt, the conti-action produces a greater velocity by one-eighth, and the head is about If times the head for rounded piers, and, consequently, very objectionable in navigable rivers. The opinions of engineers respecting the proper form of this part of a bridge are various, some contending for one form, and some for another ; but, it is obvious that, the form which divides the water with least resistance, and least contracts the water-way, must be the best ; if, at the same time that these advantages are attained, it retains suflScient strength to support the structure. The right-angled isosceles triangle was formerly employed by some bridge-builders as a form the most suitable ; this opinion arises from the consideration of the right-angle being the strongest of all others ; that is, if two bodies meet each other at right-angles, tliey will overcome a greater resistance than they would do at any other inclination. Others contend for a form composed of two arcs, containing each 60°, described from the two angles of the pier, and meeting each other in the line dividing the water: sometimes a semi-ellipse, described on a conjugate equal to the width of the pier, is used; and, not unfrequently, others of the conic sections, or some whimsical figure that pleases the fancy of the architect. Those who adopt the right-angle, erroneously contend that it divides the stream best ; those who use the semi-circle and semi-ellipse, consider that they are the best calculated to resist the shock of a loaded barge, or other floating body, that may come upon them, and that the Gothic arches combine the advantages of both : we have already observed, that the form must be adapted for dividing the stream, and allowing the water to pass most freely ; and it obvi- ously should not be pointed so as to be dangerous to navigation. Illustration of the Principles of Bridges. 116. We commence our illustration of the principles of Bridges with the magnificent edifice which bears the triumphant appellation of Waterloo Bridge ; a work not less pre-eminent among the bridges of all ages and countries than the event which it commemorates is unrivalled in the pages of ancient or modern history. It consists of nine elliptical arches, each of 120 feet span, and 35 feet rise, (see plate XVI,) the piers are 20 feet thick; and the water-way is 1080 feet. The road-way is 28 feet wide, with a foot-pavement of granite, of 7 feet width on each side. The arches and piers are built of large blocks of Cornish granite, with short reversed arches in each pier for the principal ones to abut against. The spandrils over the haunches are filled in with longitudinal walls of brick, with spaces between them, which are covered over with strong pieces of sand-stone to form the road-way upon. These hollow spaces lighten the stress on the bridge considerably ; and are provided with proper outlets to prevent water collecting in them. The arch-stones 48 PRACTICAL MASONRY. were so well worked and truly bedded together, that tlic settlement at the crown did not exceed two inches on removing the centring. The roadway is level, and the cornice is supported at the piers by massive Doric columns ; ihe parapets arc open balustrades, the balusters of Aberdeen granite, but the rest of the apparent parts of the bridge are of Cornish granite, and not of a very good quality. 117. To apply our formula (art. 110) to this case, the weight of a foot in breadth of the semi-arch of the bridge, or w — 11 2,500 lbs. ; the whole height of the abutment, or h — 48 feet ; the height of the point where the curve of equilibrium cuts against the abutment, or ic = 2.2 feet; the tangent of a = 'SS; and the weight of a cubic foot of stone 150 lbs. ; con- sequently, \/ 4Mxi5nx-83 "~ ~^'^ ^^^^' "^^ *'''^ ^® ^s.\e to add half the depth of the arch- stones, which are about 7 feet at the springing, making about 21 feet for the least thickness at the base of the abutment. Hence we see that the piers, being only 20 feet, are not sufficient to resist the push of the arches. The thickness at the base as executed is 30 feet, which is not more than a sufficient allowance for a foundation on piles. 118. To find the proper depth for the arch-stones at the crown we have jc «= 112,500 lbs., tangent of a = "So ; and by (art. 45) the pressure a square foot of Cornish granite will bear is 11-2500 , - 1 1 . • .1 I !> 114,000 lbs. ; whence the depth in feet is ii4oqox-83 ~ ^'~ '^^^ ' "°^^ ^""^ actual depth is 4^ teet; a degree of strength which would be sufficient to resist any change of figui'e, by yielding at the abutment, which does not cause the curve of equilibrium to quit the ring of arch-stones. For it is obvious that the stress is on the back part of the abutment, and if that part be not ren- dered as firm as solid rock, it must be compensated for by increasing the area of the base in proportion to its want of firmness ; otherwise some degree of change may take place. Waterloo Bridge was built under the direction of the late Mr. John Rennie. 119. The Bridge of Neuilly, over the Seine at Paris, which was built by the celebrated French engineer, Perronet, is our next example, and the construction is exhibited in Plate XVIII.* It fs composed of five elliptical arches of 128 feet span, which spring from the low water line ; the piers are only 13i feet ; and the bridge is founded on piles, the platform on which the stone- work commences being 7^ feet below the level of low water. The ends of the piers are circu- lar, and the arches are splayed towards the springing, so as to render the apparent form of the arch a flat segment of a circle, see fig. \, and the section, fig. 3. In each of the abutments there is a small arch for the towing-path ; the road-way over the bridge is level, and the ascent from the sides is effi^cted by inclined roads, as shown by the section, fig. 3. and plan, fig. 2. The width of the carriage-way is 31 feet, and the foot-paths are each (i-Q feet. During the setting of the arch-stones of this bridge, the centre changed its form consider- ably, and its rate of settlement, before the key-stone was inserted, was 3 inches in 24 hours ; hence we have shown its construction in fig. 5, in order that a construction possessing so little • This plate has been erroneously numbered XTX. in some of the numbers first published. PRINCIPLES OF BRIDGES. 49 resistance to change of form may be avoided.* A still more dangerous change took place on removing the centring; and, to observe it, sti-aight lines were traced on the face of the arch before the centring was struck, as shown at ab, be, cd, {jig. 4.) and then: position, in regard to fixed points at the extremities, were ascertained. The lines became curved, as shown by the curved lines by the side of the straight ones on the figure. The joints opened at the back of the arch at the haunches, and they opened at the under-side at the crown, showing that the arch was not properly designed. The radius of curvature at the crown was intended to be 160 feet, but the arches settled so as to render the radius 250 feet ; and the stress on the arch is nearly as the radius. The deptli of the key-stone is 5"3 feet, and the arches are constructed of Saillancourt-stone, which, it has been ascertained by experiment, will bear a pressure of 30,000 lbs. on a square foot with safety. Therefore, the weight of a foot in breadth of the semi-arch being about 61,000 lbs., and ton.a = -44, we have (by ari!. ill) the depth = ^^^i^5!L_ = 4-6 feet; showing that the arch was of depth sufficient for its first form, if the centring and abutments had been sufficient to preserve that form. 120. In the last case, the arches had a manifest tendency to sink at the crown and rise at the haunches, but this is not always the case, as will be known from the example we are now about to describe. William Edwards, a country mason, engaged in 1746 to build a bridge across the mountain-torrent, called the TafF, in Glamorgansture, and he erected one of a light and elegant structure, with three arches ; but soon after the completion a flood occurred, and it failed from want of water-way. Edwards having given security for the bridge remaining a safe means of passage for seven years, he began another of one arch only, the span of which was 140 feet, with a rise of .35 feet, being part of a circular arch of 175 feet diameter. The arch was finished, and the parapets only remained to be done, when, through the haunches being too heavy in proportion to the load at the crown, the crown rose upwards till the haunches fell into the river. Edwards saw the cause of the failure; and, with the true spirit of a Briton, began a thud bridge, of a single arch, of the same dimensions as the second, and formed a series of circular apertures through the spandril parts of the haunches, increasing in diameter towards the abut- ments ; this expedient reduced the weight of these parts, so as to preserve the balance and stability of the structure; it was completed in 1756, and remains a monument of the skill of William Edwards, and one of the finest illustrations of the theory of Bridges. 121. The bridge across the Severn, at Over, near Gloucester, which was designed and executed under the direction of Mr. Telford, the President of the Institution jof Civil Engineers, is the next example. (See plate XIX.) It consists of one elliptical arch of 150 feet span, and 35 feet rise ; it is splayed at the haunches in the manner of the bridge of Neuilly ; the apparent arch being a flat segment of a circle of 246 feet radius, and the water-way is further increased * For the construction of Centring for Bridges, see our Practical Carpentry, art. 182, et seq. O 50 PRACTICAL MASONRY. by two small arches, one through each abutment. The roadway for carriages is 17 feet wnle* and there is a foot-path of 4 feet on each side ; the whole breadth of the bridge being 27 feet, including the parapets. The roadway is supported over the spandrils by longitudinal walls of brick, with covers of stone for the cavities (see fig. 2 and 4.) The depth of the arch, at tJie crown, is 4| feet, and it is constructed of an excellent species of sand-stone from the Forest of Dean. The weight of a foot in breadth of the semi-arch is about 140,000 lbs. ; the tangent of the curve of equilibrium, at the abutment, is "58; and the stone will bear 90,000 lbs. per square foot; therefore, by the rule, {art. 111.) '- — — = 2'7 ft. for the depth, when there is no change of figure to be apprehended, and this is only five-eighths of the actual depth. Tlie abutments are 21f feet, with two walls, 7 feet thick, extending 42 feet from each (see the plan, ^^. 5); these are much more effective than the same quantity of stone-work in a solid mass, besides forming the support of the continuation of the roadway. By the rule, wc easily determine that the mean thickness of a solid pier should be 36" 1 feet, and as much more than an equivalent mass of matter is disposed in a better form for resistance, the bridge pos- sesses that excess of strength which ensures durability. Of the numerous bridges erected under the design anc. direction of Mr. Telford, this is unquestionably the best ; it unites the greatest possible degree of lightness of appearance with an ample provision of strength ; and the span is the greatest that has been executed in stone. 122. The masonry of the Suspension Bridge across the Menai, at Bangor, is our next example, and another of the immense works which Mr. Telford has designed. In common bridges, the stress tends to force the abutments outwards, — in suspension bridges, the tendency is to draw them inwards; and an equivalent degree of firmness of construction is required. From two piers, 579 feet apart, from centre to centre, a roadway is supported by chains of iron over the Menai Straight, which divides Anglesea from Wales (see plate XX, fig. 1). On the Anglesea side, the suspension-piers are connected to the shore by four arches in stone, of 52^ feet span ; and, on the Caernarvonshire side, by three arches of 52| feet span. The weight of the masses of masonry forming these arches balances the weight of the roadway, and the chains are further secured behind the abutments, as indicated in the figure. The roadway is at the height of 102 feet above the level of spring-tides, and, consequently, there is a free space of 560 feet in width, and 102 feet in height, for ships to pass. Fig. 2, shows part of the plan of the roadway to a larger scale ; it consists of two carriage-ways, with a foot-way in the middle between them. Fig. 3, is a plan of the other end of the bridge, with part of the roadway, showing the planking and the archways through the suspension-tower. Thus, by the combi- nation of strong chains of tenacious iron, with ponderous blocks of stone, skilfully arranged according to the principles of masonry, a safe and commodious road is formed for the mails and traffic across the sea, which separated the Isle of Anglesea from Wales. 123. The New London Bridge, now erecting on the western side of the old one, and as near to it as was considered safe, is from the design of the late Mr. John Rennie, and executing CONSTRUCTION OF DOMES, &C. 51 under the direction of his sons, Messrs. John and George Rennie, with some variations. The principal parts are of Scotch granite. The bridge consists of five elliptical arches, (see plate XVII,) the span of the centre one is 150 feet, and the rise 29| feet, above the datum, as the level of the high-water mark of the Trinity-House is called ; the piers adjoining the centre arch are 24 feet each ; the span of the arches next the centre one is 140 feet, with a rise of 2S\ feet above the datum, and piers of 22 feet each. The span of the arches next the abutments is 130 feet, with a rise of 25 feet above the datum, and abutments of 74 feet each. This makes the total length of the water-way 690 feet; the length between the abutments 782 feet; and the total length, including the abutments, 930 feet. The width of the carriage-way is to be 36 feet, and the width of the bridge, to the outsides of the parapets, is 56 feet. CHAPTER VI. OF THE CONSTRUCTION OF DOMES, GROINS, AND SPIRES. 124. The Construction of a Dome is less difficult than that of an arch, because the tendency which each part has to fall, is not only counteracted by the pressure of the parts below, but also by the resistance of those on each side ; hence a dome may be erected, without the expen- sive centring which an arch requires, and it may also be left open at the top, or without any key-stone. Many of the large domes have nevertheless failed, or cracked, so as to create alarm, and generally in consequence of the inadequacy of the supporting walls or piers. The masonry of domes differs from that of arching, in the figure of each voussoir, which must fit the void in a sphere instead of a cylinder. If a dome rises nearly vertical, with its form spherical, and of equal thickness, it should be confined by a chain, or hoop, as soon as the rise reaches to about ^hs of its whole diameter, in order that the lower parts may not be forced out: but, if the masonry be diminished in thickness as it rises, this precaution will not be necessary. 125. The dome of the antient Pantheon, at Rome, built by Agrippa, is the oldest and the finest example. (See plate XXI.) It is the largest vaulted edifice constructed by the antient Romans ; the plan is circular, the interior diameter 142 feet, and it is cylindrical to the height of 72J feet, with a wall 23 feet in thickness ; but the wall has so many large niches and deep recesses, that the mass is not more than equivalent to that of a wall one-third of the thickness ; while the advantage in disposition is evident. The dome itself is internally a hemisphere, with an opening at the top 29 feet in diameter ; the thickness is 4 ft. 10 in. where it joins the platform round the aperture, 5 ft. 2 in. just above the last set-ofF, and 17 feet where it joins 52 PRACTICAL MASONRY. the circular wall which supports it ; but the mass of the dome is diminished by five ranges of deep sunk caissons. The ribs between the caissons are of brick, the pannel part of tufa and pumice stones in small pieces.* The construction of the cylindrical portion is not less judicious, it is of brick and filled in with rubble-stone, but at every four feet in height a bond of brick-work is formed of bricks two inches thick and two feet square ; the discharging arches also consist of two series of these bricks, and the angles and faces of the wall are built of triangular bricks. If we attentively examine the nature of this work we find the supporting part to consist of piers connected by a continued inclosing wall, which gives the greatest degree of strength at the base, at the place where it is required to resist a tendency to overset. The dome consists of ribs and pannels ; the depth of the ribs gives stability, and the pannelled spaces are filled in with as much lightness, both in regard to material and thickness, as was consistent with the proper degree of strength. In this remarkable structure, every artifice which theory indicates is em- ployed ; and the most refined works of the Gothic builders, though so difierent in form, are the same in respect to principles ; the supports in both are piers connected by an inclosing wall ; and the vaultings of deep ribs filled in between with light pannels. The Pantheon has now existed nearly nineteen centuries ; and its fine portico has been admired by architects with more or less of paltry criticism, but the scientific skill necessary to construct such an edifice, in the absence of an example to imitate, is a rare acquirement, not often possessed by above one in an age. On the restoration of the arts in Italy, many attempts were made to imitate the dome of the Pantheon ; but the skill of the architect was, in general, insufiicient to ensure success. 126. Antheniius, a Greek architect, was selected by the Emperor Justinian, for erecting a dome to the church of St. Sophia, at Constantinople, the church itself was to be in the form of a cross, and vaulted with stone ; the dome he attempted to raise on the heads of four piers, of about 115 feet high, and at the same extent from each other, and strengthened by four but- tresses. The buttresses were solid masses of stone, extending, at least, ninety feet from the piers to the north and south, so as to form the side walls of the cross. These effectually secured the piers from the thrust of the two great arches of the nave which supported the dome. But, when the dome was finished, and had stood a few months, as there was no provision against the thrust of the great north and south arches, the two eastern piers, with their buttresses, gave way; and the dome and half-dome fell in. On the death of Anthemius, Isidorus, another Greek, succeeded to the work, and, having filled up some hollows to strengthen the piers on the east side, again began to raise the dome ; but, while one part was building, another part fell in. It was now found that the pillars and walls of the eastern semi-circular end were too much • It is said, that when the wails were I'aiseti to the springing of the dome, the interior was filled with earth to turn the dome upon; and that to induce the people to remove the earth money was strewed among it, a uiound being still pointed out by the commun people of Rome as tlie place to wluie the eartli was removed; but the story is improbable, for tlie sci- entific skill so well developed in the design of the edifice could not have had a difficulty in contriving a centre, and one of earth would have settled so as to he useless. CONSTRUCTION OF DOMES, &C. 53 shattered to give any resistance to the push which was directed against them ; and therefore several clumsy buttresses were erected on the eastern wall of the square which surrounded the Greek cross. These were roofed in, so as to form a kind of cloister, and lean against the piers of the dome, and thus oppose the thrust of the great north and south arches. The dome was now turned for the third time ; and though it was extremely flat, and, except the ribs, roofed with pumice-stone, it was soon found necessary to fill the whole, from top to bottom, with arcades, in three stories, to prevent the dome falling a third time. Thus a dome, which was intended to be a beautiful specimen of architecture, was rendered a mis-shapen mass of de- formity and an example of ignorance, which should warn the architect not rashly to undertake what he has not sufficient science, in a proper manner, to perform. 127. Since that time, domes have been erected in various parts of Europe, and some that display every requisite of beauty and strength, peculiar to this species of building. St. Peter's, at Rome, an elliptical dome, 139 feet in diameter, is a superb specimen, but not without defects, which have shown that its architects knew better how to distribute its supports for grandeur of effect, than for firmness and durability, the dome having many cracks from the unequal settle- ment of its supports. 128. The inner dome of St. Paul's, at London, is also elliptical, and open in the centre ; it is 112 feet in diameter, and still continues perfect. The lantern is supported by a conical vault of brick-work, a figure admirably adapted for supporting an immense load on its summit ; but the outer dome is formed by wooden framing.* 129. The dome of the church of St. Genevieve, including the peristyle on which it rests, is a beautiful specimen as to form and composition. The peristyle is formed by fifty-two columns of the Corinthian order, each about fifty feet high, completely insulated, and standing on a circular pedestal. Above the cornice of the peristyle, the dome arises in a beautiful curved line to the top, on which is formed a pedestal and gauery. But, when the dome was raised, the columns composing the interior began to sink with the weight ; and some of the shafts of the columns decorating the interior, which consisted of four naves, with the lantern and dome over them, began to fracture at the joinings ; this defect was removed by walling up the inter-columniation at the four quarters of the screen, which thus preserved from dilapidation one of the boldest monuments of genius. 130. The following table gives the interior diameter, the height of the top of the dome from the floor of the edifice, and the date of construction, when known, for some of the most cele- brated works of the kind in Europe. • The church of St. Genevieve has three vaults, all in stone, but then it is only 67 feet in diameter, with the vaulU of such improper forms that they will not sustain the weight it was intended to place on them. 54 PRACTICAL MASONRY. Table of the principal Domes, arranged according to their Interior Diameters. NAME OF THE DOME. 1. The dome of the Pantheon 2. The dome of Saint Peter's 3. The dome of Santa Maria delle Fiore 4. The dome of the Temple of Apollo — 5. The dome of Saint Sophia -. — G. The dome of Saint Paul's .--- — 7. The dome of the Baths of Caracalla 8. The dome of the Temple of Diana 9. The dome of the Mosque of Achmet 10. The dome of the Chapel of Medicis — 1 1 . The dome of the Temple of Venus 12. The dome of the Baptistery 13. The dome of the Church of the Invalids 14. The dome of Minena INIedica 15. The dome of the Baths of Diocletian 16. The dome of the Church of Madonna della Salute 17. The dome of the Temple of Mercury 18. The dome of the Church of Saint Genevieve ... 19. The dome of the Superga 20. The dome of the Cathedral of Milan 21 . The dome of the Church at Sienna 22. The dome of the Church of Val de Grace 23. The dome of the Church of Saint Vital 24. The dome of the Church of Saint Marc , 25. The dome of the Church of the Sorbonne 26. Thg^ttome of the Church of Saint Maria PLACE. Rome Rome Florence . Constantinople London Rome Puzzuoli Florence . . Puzzuoli .. Florence ., Paris Rome Rome . . . ; Venice — Paris , Ravenna Venice Paris Ravenna Interior diameter in feet. Hei[;lit of the lop Iroiu tlu- floor iufcet. 142 143 139 330 139 310 120 115 201 112 215 112 116 98 78 92 120 91 199 87 77 86 110 80 173 78 97 74 83 70 133 68 67 190 64 128 57 254 57 148 55 133 55 91 4-4 40 110 m 61 Rate of Erection. B.C. 18 A.D. 1580 1136 537 1710 217 1636 1704 302 1640 1790 1731 1425 1250 1660 547 984 1653 530 Theory of Domes. 131. In domes the same general principle applies as in arches, {art. 105,) the curve of equili- brium, or the resultant of the pressures at any point, should fall within the thickness of the dome or its supports ; otherwise we might as well try to support a weight by a single pillar placed in any other position than in the vertical line immediately under its centre of gravity. GROINED VAULTING 65 132. When tlie weight of the dome is equally distributed over the area, then the curve of equilibrium is a cubic parabola ; and if one-sixth part of the weight supported be multiplied by the diameter, and the result divided by the rise, the quotient is the horizontal thnist tending to separate and overset the supporting wall. 133. When the weight increases from the centre to the circumference in proportion to the distance from the centre, then the curve is a biquadratic parabola, and one-eighth part of the weight should be taken instead of one-sixth part. 134. It also may be proved, that the horizontal thrust of the dome will be wholly counter- acted by a resistance to tension in the circle, equivalent every where to one-sixth of the horizontal thrust ; and, when this strain is amply provided for, either by the bond and substance of the walls at the springing, or by chains of iron, the dome will be secure at whatever height from the ground it may spring, if the vertical walls or pillars be sufficiently so to resist the weight upon them. 135. The plan of a dome is usually a circle, and this is the most perfect figure for the pur- pose ; but any regular polygon may form the base of a dome, whether octagon, decagon, &c- they do not, however, possess the same property of resisting change of figure which belongs to the circular base. 136. If the lateral or horizontal thrust is to be resisted by the weight of the supporting wail or piers, so as to be sufficiently strong without the connection obtained by binding the parts together in a continued circle, then, the rule Cin art. 110) applies to this case, as well as to arches, where the whole weight of the dome divided by the circumference of the supporting wall, or the sum of the breadth of the piers, in feet, is inserted for w, in finding the thickness. 137. In Uke manner, by finding the weight w on each foot of circumference, the depth of the dome may be found, which renders it of sufficient strength, either at the abutments or at the crown, (by art. 106 and 111,) for when the connection of the parts is left out of the calculation, as a proper reserve of strength for duration, the arch and dome are dependent on the same principles. Of Groined Vaulting. 138. A long rectangular space may be covered with a continued arch, called a vault, but so heavy a covering, destitute of variety, had little chance to please the taste of men, who, having seen the finest works of antiquity, were desirous of excelhng them, if possible, particularly in the construction of the peculiar form that had been selected for Christian churches. The plan being a cross, the object was to find a graceful and varied form of covering, in which the pro- found science displayed in the Roman Pantheon should, at least, be equalled : for that work was evidently considered the master-piece of the age. 139. A vault, or continued arch, consisting of deep ribs, with thin pannels between, might first suggest itself; and such a construction has been employed in both vaults and bridges, the 56 PRACTICAL, MASONRY. old Gothic hr'uUe at Durham, called Framwell-gate Bridge, now being altered and widened under the direction of Mr. Bonomi, architect to the county of Durham, is one of the finest examples of the kind. On this subject we have only to remark that, in a bridge, deep ribs expose a much greater surface of stone to decay, and the experience of many ages has shown that a plain soffit is better ; but we see no difficulty in obtaining the advantage which the Gothic brido-e has in real lightness and stability, without exposing more surface to the weather than the common method. When applied as a vault, the continued arch required continued thick walls for abutments, and these were too heavy, expensive, and tasteless for the spirit of the age. 140. Vaults, supported by piers or pillars, were sometimes executed by the antient Romans; but there is a degree of formal clumsy heaviness about them, which is universally felt, and often censured ; the Gothic vault, on the contrary, commences at the base of the pillars which support it, and these being carried perpendicularly to a proper height, bend over and spread to form the ribs of the vaulting ; no interrupting entablature breaks the connection between the pillars and the ribs of the vault ; hence that lightness of effect, with apparent as well as real strength and fitness, which characterize the stone roofs of our cathedrals ; and show that these works were the production of men having a knowledge of what is most profound in the science and practice of building, and a boldness in execution of which classic antiquity furnishes no example ; neither has it descended to our times ; the art has fled, but left for our instruction, — '* Her pemlant roof, her windows* brancliy grace, Pillars of clustcr'd reeils, ami tracery of lace." 141. In a dome, if the part supported be divided into triangular portions, the base of each triande is at the supporting wall; — in a groined vault divided into triangles, the vertex of each ti-iangle is at one of the supporting piers ;— in an arch, instead of triangles, we have parallelo-. grams. But, notwithstanding this diversity in the distribution of the load to be supported, the same general principles apply, for they are but different cases of the same mechanical problem. 142. When the weight of a groined vault is equally distributed over the area it covers, the curve of equilibrium is a semi-cubical parabola ; and the horizontal tln-ust of a part compre- hended between two angle-ribs, is one-third of its weight multiplied by the span of the arch, and the result, divided by its rise, gives the thrust tending to overset the pillar or oier in the direc- tion of the body-rib of the compartment. 143. If the weight be distributed so as to increase in proportion as it approaches the support, then the curve of equilibrium will be a common parabola, and one-fourth of the weight of a compartment should be taken instead of one-third, but in other resoects the horizontal thrust is to be found as in the last article. 144. The parts of the groin which are on opposite sides of the pier balance each other, and it is usual to make the piers only of sufficient magnitude to support the load ; but the piers are so connected, by the side-walls between them, that a failure from a pier being deprived of GROINED VAULTING. 57 due of its arches is scarcely possible. In groins, as in domes, the central part may be removed, or may support a pendant load of considerable weight. 145. The earliest examples of vaulting with stone in this country were executed in the reign of Henry III., consisting of cross-ribs springing from corbels in the side-walls, with the pannels filled in with lighter materials ; and, about the reign of Edward III., cross-springers were in- troduced with more frequent and comphcated intersections, covered with carved orbs and rosettes, and the arches were pointed. To this the style of vaulting, called " fan-work," suc- ceeded ; at first, from its extreme cost and deUcacy, it was confined to tombs, small chapels, and cloisters, but was afterwards applied to roofs of larger buildings. The principal vaulted roofs are collected in the following table. 146. Vaulted roofs constructed in the fourteenth, fifteenth, and sixteenth centuries: — Date. LeDg:th. Breadth. Height. Choir of Lincoln Cathedral 1306 200 ft. 40 ft. 82 ft. Our Lady's Chapel at Ely 1349 100— 46 — Choir of Gloucester Cathedral 1360 140 — 34 — Do.ofYork 1373 135— 45 — Divinity School, Oxford 1480 Chapel of St. George, Windsor 1508 260 — 65 — Do. Henry VII. Westminster 1508 Do. King's CoUege, Cambridge 1516 289— 44i - 81 — Choir at Windsor Cathedral 1525 138— 86 — Chapel of Christ Church, Oxford 1535 SO — This hst, short as it is, will enable many of our readers to refer to existing works — " Where antient art her daedal fancies play'd, Iq the quaint mazes of the crisped roof."— Warton. 147. We alluded to the roof of King's College Chapel in our Introduction, (art. 3,) and we have chosen it as an example of the fan-shaped groin (see plate XXIV). It is 289 feet in length, 44y feet in width, and 81 feet in height ; and divided into rectangles, of which the width is half the width of the body of the chapel ; each rectangular portion of the vault rest- ing on four piers.* Fig. 2, is part of the plan, including four of the supporting piers with the ribs and tracery of the vault in one part, and the form of the stones as they appear on the upper surface of the vault in the other part. Fig. 1, is a section across the chapel, in which one part is from A to B on the plan, the other part from C to D, through the middle of the pier. Fig. 3, is a section of one of the ribs to a larger scale, showing the thickness of the ashler work forming the pannels between the ribs. These ribs are 7' in. deep, and the ashler • In an indenture, tlatid 1513, by which I. Wastell and Henry Severick engaged to finish the raulliog in three yean, these divisions of the vaulting are called "Sctereys," and, on the completion of each severey, they were to hare £100., there are twelve of them. 58 PRACTICAL MASONRY. v'ork of the pannels 4^ in. thick. Great as the merit of the designer is, his n;inie is unknown ; but its successful execution merits an equal degree of praise, and the names of John Woolrich, Henry Severick, and John Wastell, may be handed down to posterity as the most skilful master- masons of their age and nation. Of the Construction of Spires. 148. The spires of churches are pyramidal vaults either straight or convex, and generally a little convex ; they vary from 6 to 9 inches in thickness, according to the quality of the stone, or the size of the spire. The base is sometimes square, but most frequently octagon ; and they are raised from either square or octagon towers. 49. When a spire springs from a square tower, the walls of the tower are gradually in- creased in thickness towards the point from whence the spire rises, and are formed to the shape of its base ; the bond of the work being rendered as perfect as possible, by employing large stones, crossing the joints, and connecting them by cramps run in with lead ; sometimes the ring of stones on which the base of the spire rests is further secured by a chain of iron, bedded in the stone, and run in with lead. The bed-joints of the spire itself must be perpendicular to its slant surfaces, and the vertical joints directed to the centre. In order to illustrate these remarks by examples, we have selected two of the most esteemed spires in England. 150. The spire of Salisbury Cathedral (see plate XXI.) is octagonal, and rises from the centre of the' square tower, four of its sides resting on the walls of the tower, and the other four on arches across at the angles, at the top of the tower ; the wall is five feet in thickness, two of which are occupied by the base of the spire, two by a passage to go round it, and one by the parapet. The wall of the spire gradually diminishes in thickness to about twenty feet above the tower, where it is reduced to nine inches, and is continued of that thickness to the summit. The figure in the plate is one half section, showing the timber-framing within, which is ingeniously contrived, the other half elevation. Externally, the spire is ornamented with ribs up the angles, each of which has two rows of knobs attached to it, and the spire is divided into four nearly equal portions, by bands of tracery, pannels, &c. At the base tliere are four decorated door-ways to the parapet of the tower. The two uppermost divisions, or stories of the tower, and the whole of the spire, are evidently of later erection than the church, or of the lower story of the tower; the stile of architecture is enriched; and in the forms and orna- ments of the pediments, pinnacles, and open parapets, resemble the much-admired crosses raised by King Edward I., and other works erected at the end of the thirteenth century. It seems that the architect of this spire was ambitious to carry its apex higher than any similar building of stone in England ; from the ground to the highest point is 404 feet ; and though it is not of equal altitude to that of St. Stephen's Church at Vienna, which is 4(J5 feet, nor that LIGHT-HOUSES. b9 of Strasburgh, which is 4-56 feet, yet its vast height has rendered it an object of popular wonder, as well as of great curiosity and interest to the architect. To the old tower 387 feet of new foundation was added on the erection of the spire, and several windows were filled uj), and ties of iron inserted. A settlement has taken place on the western side; and it appears that, at the cap-stone of the spire, the decHnation is 24j inches to the south, and IGJ to the west. The date of its erection is the end of the thirteenth century. 151. The spire of Litchfield Cathedral is represented on the same plate, and in a similar manner, one half being a section, the other half elevation. It was finished in the middle of the fifteenth century, and it is a good example of an ornamented spire, but we do not think the insertion of windows appropriate, nor that horizontal bands and mouldings improve a spire ; they seem to owe their effect to fine proportions rising unbroken from the base to the summit ; nevertheless some degree of ornament improves a spire ; and the effect of one perfectly plain, ending in a needle-point, may be seen at the church Mr. Nash built in Langham Place. 152. When a spire is an exact pyramid, its arrises, though straiglit, appear concave to the eye; hence, in construction, they should be slightly convex ; and further, it may be proved that where there is not a perfect coherence of the parts, the figure should be convex to be of equal strength in all its parts. We have treated this subject at greater length than we had intended, because, in our eyes, the beautiful spires of some parts of England add much to the interest and effect of the country. CHAPTER VII OF THE CONSTRUCTION OF LIGHT-HOUSES. 153. A LIGHT-HOUSE is a tower of considerable height, with the means of producing li.Tht in the top part, )r lantern, so as to render it visible to a great distance at sea, to serve as a guide to seamen in steering their vessels in the night-time. 154. Those light-houses which are constructed on the sea-coasts, or on the piers of harbours, present very little difficulty ; a round or octagon tower, with a winding stair, and small rooms for the accommodation of the keeper, being the only essential parts of the masonry. In some instances, it is difficult to procure a solid foundation, and the usual methods of piling, grating, and planking, are resorted to. (See Chap. III.) 155. But the protection of the commerce of Great Britain required that light-houses should be erected on isolated rocks of the ocean; noble works, which no man can regard with indiffer- ence, rearing their heads amidst the tumultuous waves, while the dwellers within trim their lamps in safety, to guide their endangered fellow-creatures through the peril? of the storm. (See 60 PRACTICAL MASONRY. plale XXIII.) To raise a permanent light-house on a rock covered by the sea at high-water, was first attempted at the Eddystone ; two were erected chiefly of timber and destroyed, the one bv a storm, and the other by fire. Mr. Smeaton designed another to be executed in stone, it was erected, and still remains a proud monument of the skill of that celebrated engineer. The Edihj stone Light-house. 156. Mr. Snieaton's first journey to Plymouth, upon the business of the Eddystone light- house, as will be seen from his excellent narrative of the work, was in the month of March. 1756; and, on the 5th of April, the following month, he landed, for the first time, on Eddy- stone-rock. In the course of the ensuing winter, and following spring, arrangements were made for proceeding with the building operations. A large stock of materials had been pro- vided, and various experiments were made by Mr. Smeaton with lime-stone from different parts of the coast, which enabled him to conclude, that a mixture of lime from Aberthaw, in the Bristol channel, and puzzolano earth from Italy, was the proper mortar for this building. (See art. 62.) A stock of oak trenails was provided for fixing the newly-laid stones to the rock, or to the course below, which, with the system of dove-tailing and joggling, (see plate XXIII, fig. 3,) prevented them from being carried away before the mortar took bond, or while the respective courses were in an unfinished stale. Things ^being thus in preparation for the second year's operations, the attending-vessel was moored in her place, near the rock, and the foundation-stone of the building was laid on the 12th of June, 1757 ; and, by much perse- verance, the ninth course, or third entire course above the top of the rock, was completed by the last day of September, with which the season's work was successfully closed. Owing to several disappointments, the commencement of the work at the rock did not take place till the 2d day of July, 1758, when part of the 10th course was landed ; and, by the 8th of August, the 14th course, or solid part of the building, was completed, which brought the work to the entrance-door, or to the height of 12 feet above the top of the rock; and, by the latter end of September, the 24th course, forming the top of the staircase and floor of the first apart- ment, or store-room, was laid. Tlie work being continued till the beginning of the month of October, the outward circle of the 29th course, or the arciied roof of the store-room, was laid. It was not till the latter end of March following, that a favourable opportunity was afforded to Mr. Jessop, the assistant-engineer, for landing at the rock, when he found every thing nearly in the same state in which it had been left in the month of October, excepting one stone of the upper or unfinished course, which the workmen were in the act of laying, when they were oblio^ed hastilv to leave the rock. This stone had been carried away from its having, perhaps, been left too near the outer verge of the building. But it deserves notice, that the wooden centering, for carrying the arch or dome over the store-room, was found in its place, after all the gales of winter, together with a set of wooden triangles, which had been left on the top of LIGHT-HOUSES. 61 the building, and were found, on landing in the spring, to be in good condition, together with a stone which was ready to be laid, and was still found suspended by the tackle. By the middle of the month of June, 1759, in the fourth and last year of the work, the whole of the stones were hewn early in the season, and were ready to ship from the work-yard to the rock. The work commenced this season on the 5th of July, and by the 17th of August following, the balcony and upper course of the cornice was laid, which completed the masonry of the Eddy- stone light-house. The exterior parts of the building which are exposed to the action of the sea are of granite, the interior of Portland stone. Fig. 5, shows the continued chain which is inserted to assist the tendency to spread from the thrust of the floors ; and fig. 4, the cramps and dowels in the other courses. The Bell Rock Light-house. 157. The Bell Rock light-house is nearly of the same form as the Eddystone, with some improvements in the mode of constructing the upper parts of the work. Fig. 1, plate XXIII, is an elevation ; and fig. 2, a section of the Bell Rock light-house. The Bell Rock itself is a sunken reef of sand-stone, the highest part only being uncovered at ordinary ebb-tides. The nearest land to the Bell Rock is the town of Arbroath, from which it lies in a south-eastern direction, about 1 1 miles distant. The dimensions of the part of the rock which become dry in spring-tides are, about 400 feet in length, and 250 in breadth ; at flood-tides, the whole rock is from 10 to 12 feet under water, and it presents a very rugged surface. In regard to the depth of the sea near the Bell Rock, it appears that, at the distance of about 100 yards, in a low state of the tide, the water varies from two to three fathoms in depth. Between the rock and the opposite shore of Fife the greatest depth is 23 fathoms ; but on the south-east, or sea- ward side, it increases suddenly to 23 fathoms. The observations made upon the currents at the rock are curious. Although a mere spot on the surface of the ocean, it produces all the remarkable phenomena of in-shore and ofi'-shore tides, which are noticeable on the projecting coasts of the mainland, or among the Scottish islands. Mr. Stevenson first landed on the rock in the summer of 1800 ; and became satisfied of the practicability of erecting a stone light-house on this fatal reef, upon principles similar to those employed by Smeaton in the construction of the Eddystone one, and reported to that effect to the Commissioners of Northern Light-houses, who also consulted Mr. Rennie on the subject; and the work was commenced in 1807. From the insidated and distant situation of this rock, the first object was to moor the tender for the exhibition of a temporary light, and for the convenient residence of the artificers. A vessel was also provided for carrying workmen between the shore and the rock. Quarries were opened near Aberdeen for supplying granite for the outward courses of the building, and at Kingoodie, near Dundee, for supplying sand-stone for the interior. The principal establish- R 62 PRACTICAL MASONRY. ment on shore was Hxed at Arbroath, where a large enclosure was procured for the preparation of the stones, connected with barracks for the accommodation of the artificers. By strenuous and unremitting exertions the beacon-house was erected, and the foundations of the building prepared by the middle of the month of July, in the second season of the work. The foun- dation had the appearance of a great circular platform of compact red sand-stone, measuring 42 feet in diameter, surrounded by an irregular margin of rock, rising from 18 inches to 5 feet. In the work-yard at Arbroath, where the materials were prepared, the first and second courses of the light-house now lay ready for being shipped for the rock. Each stone was accurately marked, so that its relative position in the building on the rock could at once be recognised. The stones were cut of a dove-tail form, on a plan similar to those of the Eddystone light- house. The foundation-stone at the Bell Rock was laid by Mr. Stevenson with masonic ceremony, on the 10th of July, 1808; and, by the latter end of September, the works were brought to a conclusion for the season. The building, being now on a level with the highest part of the margin of the foundation-pit, or about 5 feet 6 inches above the lower bed of the foundation-stone, is computed at 388 tons of stone, consisting of 400 blocks, connected by 738 oaken trenails, and 1215 pairs of oaken wedges. The number of hours of low-water work upon the rock this season was 265, of which number only 80 were employed in building. In the spring of the year 1809, the operations re-commenced. Every thing was found to have withstood the eftects of the winter's storms, all the courses which had been laid, and the beacon itself, now in the third year from its erection, remaining quite entire; and with that season was completed the 24th course, reckoning above the first entire one, and the 26th above the rock. This finished the solid part of the building, and terminated the height of the out- ward casing of granite, which is 31 feet 6 inches above the rock, or site of the foundation- stone, and about 17 feet above high-water, at spring-tides. The first circumstance attended to in commencing the building operations of 1810 was to fix upon the proper position of the entrance-door of the light-house. In this Mr. Stevenson was assisted by carefully observing the range of the sea upon the solid part of the building, and by tracing the growth of fuci and confervas on the walls. The heaviest sea being in this manner determined to be from the north-east, the door was consequently laid off towards the south-west. This and other preli- minary steps having been taken, the first cargo of stones was brought to the rock about the middle of May ; and, from the very complete and systematic arrangement of the works, the building operations were brought to a close during the month of August, without any material obstacle having been experienced. This greatly increased facility in building, was ascribed partly to the experience acquired by practice in former seasons, in landing and raising the materials. Plate XXIII, contains an elevation and section of the light-house, to which we refer our readers. Having already noticed the manner of attaching the lower courses of the stones, which was similar to that resorted to at the Eddystone, we shall now advert to the plan followed for the upper or habitable part. At the stone staircase, leading from the door to the first floor, the ORNAMENTAL MASONRY. 63 wall is of the medium thickness of about 7 feet, and gradually diminishes upwards, till, under the cornice of the building, it is only 18 inches. The stones of the walls of the several apartments are connected at the ends with dove-tail joints instead of square joggles, as in the solid and in the stair-case ; while the bed-joints are fairly imbedded in each other by means of a girth raised upon the one stone, and sunk into the other. The floors are also constructed in a manner which adds much to the bond or union of the fabric. Instead of being arched, which would give a tendency or pressure outwards on the walls, the floors are formed of long stones, radiating from the centre of the respective apartments, and at the same time forming a course of the outward walls of the building. These floor-stones are also joggled sideways, and, upon the whole, form a complete girth at each story. In this manner, the pressure of the floors is rendered perpendicular, while the side-joggles resemble the groove and feather in carpentry. In the strangers'-room, or library, the roof takes an arched form, but the curve is cut only upon the interior ends of the stones of the cornice, the several courses of which it is composed being all laid upon level beds. On the 2d of February, 1811, it was lighted for the first time. The light is clear and power- ful, and may be seen, when the sky is clear, very distinctly at eight leagues distance. The light is alternately red and white. " Far in the bosom of the deep, O'er the wide shelves my watch I keep — A ruddy gem of changeful light, Bound on the dusky brow of night ; The seaman scuds, my lustre hails. And seems to sti'ike his timorous sails." — Sir \V. Scott. CHAPTER VIII. ORNAMENTAL MASONRY. 158. Ornamental Masonry includes the construction of columns and the parts connected with them, stairs, chimney-pieces, and monuments. 159. Of columns. — These comprise, generally, a conoidal shaft, with a diminution towards their upper diameter, which is, generally, about one-sixth less than the lower diameter. The proportions of columns, among the Egyptians, varied but little ; the columns of this people, in their large temples, were only about four and a half diameters in height. Those of Greece vary considerably ; the Doric from 4|- to t>J- diameters ; those of the Parthenon, at Athens, are little more than five. In the best Roman examples, the proportion of the Doric was increased to seven diameters. The columns of all the Grecian remains are fluted. The Doric (34 PRACTICAL MASONRY. shafts liave for their flutes very flat segments of circles, finished to an arris : but someiinies flutings of the semi-elliptical shape were adopted. The genius of an architect is generally displayed in the application of columns. The Greeks surrounded their public walks with them ; and in their porticos carried this kind of splendour to its highest pitch. To construct a temple, in the Greek manner, required the greatest taste and judgment, combined with a perfect know- led 80 PRACTICAL MASONRY. ffi. a, to the points c, u, t, in which they recede the most. The triangular parts xvr, qrv, qnu, mnu, mlt, alt, are portions of a convex surface. The spaces between the concentric arcs re present concave surfaces. 239. Fig. 4, a Gothic window in three compartments. In this the muUions of the head-work intersect each other. To form such a window, the extreme breadth over the fillets is divided into three equal parts, and vertical lines are drawn through the points of division ; these vertical lines are the bisecting lines of the breadths of the fillets, and are prolonged until they meet the base line of the large arch which springs from the jambs of the window. Then whatever be the radius of the two side-arches springing from the jambs, the same radius must be used for the corresponding parts of the arches which terminate the upper extre- mities of the compartments ; hence, whatever be the form of the extreme side-arches, the rami- fications of the muUions will have arches of the same form : all the corresponding parts of these arches may therefore be wrought by the same moulds. 1 he two middle ramifications intersect each other, and form symmetrical quadrilaterals with the adjacent ramifications, formintr the heads of the extreme compartments. In each of these quadrilaterals, the opposite eyes and i)oints are all symmetrical with regard to the vertical lines bisecting the breadth of the fillets. Each of the three arches over each compartment is described in the same manner as shown for fig. 3 The eyes and points in each of the quadrilaterals must be formed by the eye. In all these the straight line which bisects each of the points, must always be in a direction of the radius of curvature of the various arcs described. The moulding over the head, which returns upon the face of the wall, is termed the hood or label-moulding. Fig. 5, is a section of the label to a larger scale. Fig. G, is an enlarged section through one of the munnions. In this the curves, both within and without, are equal and similar, and both sides are symmetrical, as regards their lines of symmetry, which are vertical. The two notches, one upon each side, are taken out, in order to receive the glass-frame, which being inserted, the frame is fixed with cement, by which the complete surface of the hollow and the straight part perpendicular to the glass is symmetrically formed to the same section, as the part on the outside of the glass-frame. The transome of this window is plain, but it may be ornamented in the same manner as the heads of the three vertical compartments; but with this difference, that each head ought to be similar to the arches which spring from the jambs, and not to those which spring from the munnions. When the ornaments of any head consist of three eyes, the head is called a trefoil-head ; and when it consists of five eyes, it is called a cinquef oil-head ; figures 7 and 8 are profiles of different forms for labels. 240. Plate XXIX containing Grecian and Roman windows {art. 192). Fig. I, the elevation of a window, with an architrave and sill surrounding the aperture. The architrave has a break upon each side immediately under the lintel, as was frequently done in Greek and Roman archi- APPENDIX TO ORNAMENTAL MASONRY. 81 tecture. The sill of the window is something broader than the architrave. The sills of ancient buildings have no relation to those of common buildings, which are generally of one thickness in tlieir height, and usually about 2j inches, when the aperture is without an architrave, or without any other ornament on the three remaining sides. Windows of this description are appropriate to buildings of one story, slightly decorated in the other parts. The elevation of the window here given is in imitation of that in the temple of Erectheus, at Athens. 241. Fig. 2, the elevation of a window, surrounded with an architrave on the two vertical sides and over the head ; the two vertical sides of the architrave are flanked with plain pilasters, and the horizontal part of the architrave is surmounted by a frieze and cornice, of which each extremity is supported by a console. The breadth of the sill is equal to that of the architrave. The profile of the ornaments, which shows the end elevation of the cornice and the side of the console, is exhibited at Jig. 3. Such forms of windows may be apphed to the principal stories of buildings. 242. Fig. 4, elevation, consisting of the dressings of a window, of which the upper part is a regular entablature, surmounted with a pediment. The architrave round the three sides, and the sill, being very nearly similar to those in fig. 1, as well as the aperture, which is wider at the bottom than at the top. These trapezoidal apertures were used both by the Greeks and Romans ; but not in imitation of those which are to be found among the Egyptians : for, as it has already been observed that, in the remaining antiquities of Egypt, the jambs of all apertures are vertical, and are therefore parallel to each other ; and consequently, because the sills and soffits are level, the apertures of Egyptian buildings are rectangular. The simple ornament, however, which forms a kind of architrave, is wider at the bottom than at the top. 243. Fig. 5, exhibits the dressings of an arched window, the ornaments consist of pilasters, one on each side of the aperture, supporting an archivolt, concentric with the semi-circular head of the window. Though the ornaments of this window are Roman, the combination is Gothic. 244. Plates XXIX. a, XXIX. i. — Decorations for chimney-pieces. In these ornaments, for want of original precedents, we are under the necessity of applying such ornaments to the aper- tures of fire-places, as we might suppose that the ancients would have done, had they used such recesses in their walls for the warming of rooms. 245. Plates XXIX. c, XXIX. d. — Designs for monuments. Plate XXIX. c, is a design for a monument in the florid style of Gothic architecture. In the Grecian style of architecture, the fillets and faces of architraves are, in ancient and modern works, parallel to the face of the building ; but, in Gothic architecture, the architrave is neither parallel nor perpendicular to the face, but at an angle generally inclined at lo5 degrees. In the design before us, though truly Gothic, may be traced the features of genuine Greek architecture, with the exception of the architrave, and the ornaments which surround the arch. The sill, instead of being plain, is decorated with Gothic mouldings, and support pilasters, which, instead of being plain, are oma- Y 82 PRACTICAL MASONRY. merited with panels, terminating with eyes and points, as usual in this species of architecture. The pilasters support a frieze and cornice. The frieze is decorated with square pateras of various forms. It must, however, be observed here, that the pilasters have no apparent break at the top, but are joined together by a part extending over the head of the architrave in the same plane with the styles and heads. The cornice on the top is surmounted with a tablet filled with diagonal panels, and the panels are surrounded with points and eyes. The cornice which terminates this tablet has a sharp- pointed pediment in the centre. One peculiarity in Gothic architrave mouldings is, that the outer mouldings are frequently carried perpendicularly, and mitre with a corresponding horizontal part, and thus forming three sides of a rectangle ; and the adjacent mouldings in the middle parts of the architrave are carried from the spring round upon each jamb, and meet together over the centre of the aperture, and thus form a Gothic arch. The mouldings of the architrave, which form the three sides of a rectangle, and the Gothic curves, contain triangular spaces called spandrils, which are generally filled with quatrefoil-arcs and small panels upon each side. The under side of the arch is often decorated with cusp-panels. In this example, besides the cusp-panels, the inner margin termi- nates in eyes and points. Plate XXIX. (/, is a design of a monument in the Grecian style of architecture, which, from a dcree of neatness and plainness, exhibits a striking contrast when compared with the Gothic. CHAPTER IX. VALUATION OF MASONS' WORK. 246. To all the distinct parts of Masons' work, a certain value is assigned for the labour and expense of erection and execution. Masons' work is generally measured with two rods, about five feet long, each divided into feet, halves and quarters of feet, and sometimes inches; but the common rule is generally applied to measure the smaller fractions. Stone-work, exceeding two inches in thickness, is valued by cubic feet ; if less than two inches, it is valued as slabs, by the superficial feet. All kinds of ornamental work, as groovings, flutings, joints, rebats, throatings, copings, &c., are valued by the running foot. The dimensions are put down in a book. It often happens that there are several pieces of the same size, and these are marked down, as well as the nature ot the stone, and the species of labour required for working it. VALUATION OF MASONS* WORK. 83 Thus every portion of material and labour is accurately ascertained. After thb has been done, a loose sheet of paper is ruled into as many columns as there are species of work, which is written over the head of each ; as, begiming with cube of Portland-stone, is placed in the column under that head ; and the same for piain-work, sunk-work, moulded-work, and each species of running-work, separately. They are cast up at the bottom of each column, and from them made out into bills, beginning with cubes, then superficies ; and, lastly, ornamental- work. For measuring, cubing, squaring, valuing, and finishing the account, surveyors are allowed two and a half per cent, on the gross amount. 247. Plain-work consists merely in the cleaning up of its surface, and all is measured which is seen. 248. Sunlc-work is that which has been partly chiselled away, as the tops of window-cills, &c. 249. Moulded-work is that which is formed into various forms on the edges, as cornices, architraves, &c. The dimensions of moulded-work are ascertained by girting the whole round with a piece of tape, over and into all its several parts ; the length of the tape will give the width of the moulded-work, and then taking its length, and squaring them together, the super- ficial quantity of moulded-work will be given. A distinct valuation is attached to each kind of labour ; and, as this varies in different places, it would be of little use to insert any here. In London, however, the prices are uniform for each separate kind. CHAPTER X. AN EXPLANATION OF TERMS, AND DESCRIPTION OF TOOLS, USED IN MASONRY. Abutment. — A term used in masonry, which implies one of the props at the springing of an arch, which is supported by an abutment at each end. The abutments of a bridge mean the walls adjoining to the land, which support the ends of the extreme arches or roadway. Aperture. — An opening through a wall, &c. which has, generally, four straight sides, form- ing a rectangle ; of these four sides, two are perpendicular to the horizon, and the other two parallel to it ; the vertical stones are called jambs. The lower horizontal stone is called the cill, and the upper one the head or lintel. Sometimes, instead of a lintel, an arch is introduced, in order to support the incumbent wall. If the head be an arch, the aperture is called an arcade. Apertures may be entirely cylindrical ; but these are not very frequent. Arch. — Part of a building suspended over a hollow, between abutments at the extremities, and concave towards the area, over which the arch is suspended. 84 PRACTICAL MASOXRY. Archivolt, is the architrave round an arch, formed into mouldings concentric with the in- trados upon the upper sides of the arch-stones in the face of the work ; by the archivolt is also understood the whole set of arch-stones that appear in the face of the work. Ashlar. — A term applied to common or fiee-stones, as they come out of the quarry. By ashlar is also meant the facing of squared stones on the front of a building. If the work be so smoothed as to take out the marks of the tools by which the stones were first cut, it is called plane-ashlar : if figured, it may be tooled ashlar, or random tooled, or chiselled, or boasted, oi pointed. If the stones project from the joints, it is said to be rusticated. Banker. — The stone bench on which work is cut and squared. Banquet. — The raised foot-way adjoining to the parapet on the sides of a bridge. Battardeau. — See Coffer-dam. Batter. — The leaning part of the upper part of the face of a wall, which so inclines as to make the plumb-line fall within the solid. Beds of a Stone. — The parallel surfaces which intersect the face of the woik in lines parallel to the horizon, and meet two and two in every pair of adjacent stones. In arching, the beds were formerly called sumtnerings ; but now, with more propriety, radio- tions or radiated joints. Bond. — That regular connexion, in lapping the stones upon one another, when carrying up the work, which forms an inseparable mass of building. Butment. — See Jbutment. Caisson. — A chest of strong timber in which the piers of a bridge are built, by sinking it, as the work advances, till it comes in contact with the bed of the river, and then the sides are dis- engaged, being constructed for that purpose. Centres. — The frame of timber-work for supporting arches during their erection. Coffer-dam, or Battardeau. — A case of piling, without a bottom, constructed for inclosing and building the piers of a bridge. A cofter-dam may be either single or double, the epace between being filled with clay or chalk, closely rammed. Drag. — A thin plate of steel indented on the edge, like the teeth of a saw, and used in working soft stone, which has no grit, for finishing the surface. Drift. — The horizontal force of an arch, by which it tends to overset the piers. Extrados of an Arch. — The exterior or convex curve, or the top of the arch-stones. This term is opposed to the Intrados, or concave side. Extrados of a Bridge. — The curve of the road-way. Fence-Wall. — A wall used to prevent the encroachment of men or animals. Footings. — Projecting courses of stone, without the naked superincumbent part, and which are laid in order to rest a wall firmly on its base. Headers. — Stones disposed with their length horizontally, in the thickness of the wall Jettee. The border made around the stilts under a pier. EXPLANATION OF TERMS, &C. USED IN MASONRY. 85 Impost or Springing. — The upper part or parts of a wall employed for springing an arch. Intrados. — The concave surface, or soffit, of an arch. Joggled Joints.— The method of indenting the stones, so as to prevent the one from being pushed away from the other by lateral force. Key-Stones. — A term frequently used for bond-stones. Key-Stone. — The middle voussoir of an arch, over the centre. Key-Stone of an Arch. — The stone at the summit of the arch, put in last for wedging and closing the arch. Level. — Horizontal, or parallel to the horizon; or, a straight line perpendicular to a plumb-line. Naked, of a Wall. — The vertical or battering surface, whence all projectures arise. Off-set. — The upper surface of a lower part of a wall, left by reducing the thickness of the superincumbent part upon one side or the other, or both. Parapets. — The breast-walls erected on the sides of the extrados of the bridge, for prevent- ing passengers from falling over. Paving. — A floor, or surface of stone, for walking upon. Piers in Houses. — The walls between apertures, or between an aperture and the corner. PiEKS of a Bridge. — The insulated parts between the apertures, for supporting the arches and road-way. Piles. — Timbers driven into the bed of a river, or the fuundation of a building for support- ing a structure. Pitch of an Arch.— The height from the summit of the arch to the chord extended be- tween the springing-points. Push of an Arch. — The same as Drift ; which see. Quarry. — The place whence stones are raised. Random Courses, in Paving. — Unequal courses, without any regard to the arrangement of the joints. Shoot of an Arch. — The same as Drift ; which see. Span. — The span of an arch is the extension between the two springings. Sterlings. — A case made about a pier of stilts, or piles, in order to secure it. See the following article. Stilts. — A set of piles driven into the bed of a river, at small distances, with a surrounding case of piling driven closely together, and the interstices filled with stones, in order to form a foundation for building the pier upon. Stretchers. — Those stones which have their length disposed horizontally in the length ol the wall. Through Stones. — A term employed, in some countries, for bond-stones. Thrust. — The same as Drift ; which see. z 86 PRACTICAL MASONRY. Tools used by Masons. — Tlie masons Level, Plumb-Rule, Square, Bevel, Trowel, Hod, and Compasses. The Saw used by masons is without teeth, and stretched in a frame nearly resembling the joiner's saw-frame. It is made from four to six feet, or more, in length, according to the size of the slabs which arc intended to be cut by it. To facilitate the process of cutting slabs into slips and scantlings, a portion of sharp silicious sand is placed upon an inclined plane, with a small barrel of water at the top, furnished with a spigot, which is left sufficiently loose to allow the water to exude drop by drop ; and thus, by running over the sand, carries with it a portion of sand into the kerf of the stone. The workman sits at one side of the stone, and draws the saw to and fro, horizontally, taking a range of about twelve inches each time before he returns. By this means, calcareous stones of the hardest kinds may be cut into slabs of any thickness, with scarcely any loss of substance. But, as this method of sawing stone is slow and expensive, mills have been erected in various parts of Great Britain, by which the same process is performed at a much cheaper rate, and in some of these mills every species of mould- ing upon stone is produced. Masons make use of many chisels, of different sizes, but all resembling, or nearly resem- bling, each other in form. They are usually made of iron and steel welded together ; but, when made entirely of steel, which is more elastic than iron, they will naturally produce a greater effect with any given impulse. The form of masons' chisels is that of a wedge, the cutting-edge being the extremity of the vertical angle. They are made about eight or nine inches long. When the cutting-edge is broader than the portion held in the hand, the lower part is expanded in the form of a dove-tail. When the cutting-edge is smaller than the handle, the lower end is sloped down in the form of a pyramid. In finishing off stone, smooth and neat, great care should be taken that the arris is not splintered, which would certainly occur, if the edge of the chisel were directed outwards in making the blow : but, if it be directed inwards, so as to overhang a little, and form an angle of about forty-five degrees, there is little danger of splintering the arris in chipping. Of the two kinds of chisels which are the most frequently made use of, the tool is the largest ; that is to say, in the breadth of its cutting-edge ; it is used for working the surface of stone into narrow furrows, or channels, at regular distances ; this operation is called tooling, and the surface is said to be tooled. The Point is the smallest kind of chisel used by masons, being never more than a quarter of an inch broad on its cutting-edge. It is used for reducing the irregularity of the surface of any rough stone. The Straight-Edge is similar to the instrument among carpenters of the same name ; it being a thin board, planed straight upon one edge, to point out cross-windings and other mequalities of surface, and thus direct the workmen in the use of the chisel. EXPLANATION OF TERMS, &C. TSED IN MASONRY. 87 The Mallet used by the mason differs from that of any other artisan. It is similar to a dome in contour, excepting a portion of the broadest part, which is rather cyhndrical. The handle is rather short, being only just long enough to be firmly grasped in the hand. It is employed for giving percussive force to chisels, by striking them with any part of the cylindrical surface of the mallet. The Hammer used by masons is generally furnished with a point or an edge like a chisel. Both kinds are used for dividing stones, and likewise for producing those narrow marks or fur- rows left upon hewn-stone work which is not ground on the face. Vault. — A mass of stones so combined as to support each other over a hollow. Under Bed of a Stone. — The lower surface, generally placed horizontally. Upper Bed of a Stone. — The upper surface, generally placed horizontally. VoussoiRs. — The arch-stones in the face or faces of an arch ; the middle one is called the ket/stone. Wall. — An erection of stone, generally perpendicular to the horizon ; but sometimes batter- ing, in order to give stability. Walls are of various descriptions, and, on some occasions, they are denominated from the nature of the plan, whatever may be the form of the profile ; and thus, generally speaking, a wall may either be straight or curved. A straight wall is that in which the two edges of its plan (supposed to be horizontal) is a straight line ; and a curved wall is that of which the two edges of its plan (supposing these edges contained in a horizontal plane) are curves. Walls are also denominated from the form of their surface. A plan^ wall is a straight wall, in which the sides of the vertical section are straight lines, either perpendicular to the horizon or battering. A cylindrical wall is a wall of which the plan is a curve, and of which the vertical sections are right lines perpendicular to the horizon. However, in order that a wall may be called a cylin- drical wall, it is only necessary that one side may be a cylindrical surface. A conical wall is that of which the plan is a curve, and the rising line of the profile a battering right-line. 88 PRACTICAL BRICKLAYING. BOOK II BRICKLAYING INTRODUCTION. 250. JcSrICKLAYING is the art of Building with Brick, or of uniting them, by cement or mortar, into various forms for particular purposes. 251. Before we enter into the descriptive and technical explanations of this useful art, it will be advantageous to investigate the nature and properties of the various kinds of bricks that have been made, not only in this counti7, but also in those countries where the genial tempe- rature of the climate permitted the use of bricks manufactured in a more simple manner than can possibly be adopted in this country, where alternate frost and thaw are prevalent. Bricks may not improperly be considered as a kind of artificial stone : but, before we enter into a description of the various kinds that are produced by the process of burning, or partial vitrification, it will be proper to notice the nature of those that, in warm cHmates, are made sufficiently durable by being dried in the %un. As clay is the material that has at all times been used for making bricks, some of its peculiar properties require to be noticed in this place, in order to show the propriety of certain operations that are necessary in the manufacture of that most necessary article. Alumina is one of the primitive earths, and constitutes the plastic principle of all clays, loams, and boles, on account of its being obtained in the greatest degree of purity from alum. It has obtained the name of Alumina; and it should be here understood, that the various proper- ties which we find in clays, cannot arise from any variation in the quaUty of the Alumina which constitutes the base of all clays, but from the admixture of silicia, iron, lime, mica, feltspar, &c., which, being combined or mixed with them in various proportions, renders them peculiarly valuable for certain purposes, when tliev are properly selected and prepared by the processes peculiar to certain manufactures. If we carefully observe the various strata of clay, as they lie in their natural beds, we shall find that all of them permit water to percolate through them with great facility, both ascending and descending, and hence springs are by no means uncommon where clay abounds : but if clay of that plastic kind, suitable for the manufacture of bricks and various kinds of pottery, be dug from its native bed, and exposed to the action of the atmosphere, and also to the degree of temperature producing frost, it will be disintegrated in a considerable degree, and rendered, by INTRODUCTION. 89 such minute division of its substance, more fit for the operation of mixing with other sub- stances or materials necessary in certain cases, and which will be hereafter described. When clay has been treated in the manner above described, it must be moistened sufficiently with water, and be well beaten or wrought together without any admixture of other materials ; and if it be also well compressed together, it will attain such a degree of solidity by compression as will render it capable of resisting the passage of water through it in a considerable degree : its filtering or percolating properties being by these means very nearly destroyed. It is in this state that it should be used as a covering to arches forming the vaults in front of houses, to prevent the water from passing through the brick-work, and thereby destroying any articles usually deposited therein. If clay be tempered in this manner, and when it has obtained a certain degree of dryness, and it be firmly compressed in a mould either by absolute weight or percussion, and if it be afterwards well dried in the air, with the addition of the heat of the sun, bricks so made will be found sufficiently hard to resist the effects of great pressure ; hence walls may be constructed in warm climates that will be found very durable. It is stated by ancient authors upon this subject, that such bricks were seldom used until they had been submitted to the process of drying for two years at least. Vitruvius, in describing the nature and properties of semi-dried bricks, states that such could not be used by the Romans within the city, for the laws did not permit any walls in public places to be made thicker than one foot and a half; whereas sun-dried bricks of that thickness would not support more than one story. When Augustus boasted that he found Rome of brick, and left it of marble, it is evident that he must have meant sun-dried bricks ; for it is well known that the temple of Peace, the Pantheon, and many other buildings, were constructed of bricks, hardened by the process of burning. Tlie use of bricks is of the greatest antiquity; the cement used in the earliest periods being a kind of bitumen. In this manner the city of Nineveh was built by Nimrod, and the justly celebrated walls of Babylon, estimated by the Greeks as worthy to be numbered among the wonders of the world, were erected of the same materials. The method of making unburnt bricks, by the Egyptians of modern times, appears to be the same that was adopted in the oldest time ; namely, that of mixing straw with tempered clay, in order to prevent the mass from cracking. This is proved by examining the remains of a pyramid formed of these bricks, the name of which is stated by Pocoke to be " Klouber-el menshich." The remains of this immense structure were found to be 150 feet hish. 252. Having so far explained the nature of sun-dried bricks, we shall now call the attention of our readers to that of kind of bricks that are hardened by the action of fire. In most cases, fine pure clay is found to make the most durable bricks, provided proper care be taken to temper the clay well, and also that they be well dried and sufficiently burned. Many of the £a 90 PRACTICAL BRICKLAYING. bricks or tiles made by the Romans while in this country arc still in existence : a portion or fragment of an arch may be seen at Leicester, composed of Roman tiles, which retain their original hardness ; and those appear to be made of clay, containing a large portion of the oxyde of iron, the colour being red. They have evidently been burned, and most hkely with wood as fuel, coal being most probably either unknown, or very little used at that period. This red kind of brick is very generally known over England, as most of our clays are, more or less, combined or impre"nated with oxyde of iron ; that being the material that imparts the red colour to earths when burned. Bricks of this description are usually burned in kilns, in which case the fire completely sur- rounds them, and the equality of heat that can be obtained by these means produces a greater equality in the articles so burned, than can be obtained by burning in clumps, which is the method that is most frequently adopted around London. 253. The bricks of the antients were of various forms and sizes, and their triangular bricks were peculiarly adapted to certain figures, but modern bricks, of English make, are commonly of one form, 9 inches long, by 4| broad, and 2\ deep. 254'. Bricks, near the metropolis, are made of a species of clay or loamy earth, either pure or with various mixtures ; they are shaped in a mould, and, after some drying in the sun or air, are burnt to an uncertain degree of hardness. The more pure the earth of which they are formed, the harder and firmer the bricks will be. The bricks generally known to our modern builders are of several sorts : that is to say. Marls, of two qualities, Gray-StocJcs, and Place- Bricks, besides two or three foreign kinds, occasionally imported. Bricks vary in quality, according to the quality of the material of which they are composed, the manner in which the clay is tempered, and the diffusion of the heat while burning. The finest kind of Marls, called Firsts, are those usually selected for arches over doors and windows : those less fine, called Seconds, are commonly used for the fronts of buildings. The Gray-Stocks are of the next quahty, and are generally of good earth, well-wrought, with little mixture, sound, and durable. Place-Bricks are too frequently poor and brittle, badly burnt, and of very irregular colour. Burrs or Clinkers are such as are so much overburnt as to vitrify, and run too or three together. Red Stocks and the Red Bricks, called also, from their use. Cutting Bricks, owe their colour to the nature of the clay of which they are made, containing much oxyde of iron ; this is always used tolerably pure, and the bricks of the better kind are called by some Claij Bricks, because they are supposed to be made of nothing else. 255. Many of the clays near London are so largely mixed with gravel, that it is found neces- sary to have recourse to the process of washing, and for this pui-pose, clay-mills are used, in which the clay when dug is placed, and plenty of water being poured upon it, the mass is agitated and separated in a circular trough, and when the gravel has subsided to the bottom, the fluid is permitted to run off into pits where the superfluous water drains from it; and when INTRODUCTION. 91 it has obtained sufficient consistency, the materials necessary to be mixed with it are then laid upon the surface, and mixed with it by the manual operation of tempering. In many parts of tlie country, clay mixed in certain proportions with cow-dung, small coals, saw-dust, and other combustible materials, is used as fuel, when made up into balls and dried in the sun or air ; and when masses of these are laid together and kindled, they are found to consume, and offer a very convenient mode of using the refuse of coal and other materials. The principle of making bricks near the metropolis is so analogous to this method of preparing fuel, that we have thought it right to call the attention of our readers to the subject, in order that the circumstances of burning bricks in clamps may be better understood. The very great consumption of coals in London, and its environs, produces an immense quantity of cinders and ashes, which are collected, and when sifted to separate the cinders or breeze (as they are technically called) from the ashes or soil, they are sold to the brick-makers to mix with their clay, and also to burn their bricks with. About one-fourth or one-sixth, as the case may be, of the soil or ashes, is usually mixed with the clay for making the common gray-stock, and also the j)lace-bricks, and the mixture is in such a plastic state as to enable the workman to fill his mould, by merely letting it fall with some degree of force into it, and the superfluous part is removed with a wooden straight-edge, and so little is it compressed that it will readily drop out of the mould, upon either hand-board used to remove it upon. In this state it is laid upon others, that have attained some degree of dryness, and thus rendered fit to be placed in the clamp to be burned. A little consideration will shew that bricks so made are very similar to the clay-balls above named; that is to say, they are combined with materials calculated to burn themselves, in a great degree, when properly kindled : for if the ashes or soil, as it is technically called, be carefully examined, it will be found to contain a large portion of the small coals that have fallen through the grates, and which has never been submitted to the action of combustion at all, aiul also a large portion of very minute cinders, quite capable of supporting combustion, and thereby assisting to burn, or partially vitrify, the mass of which they form so large a part. 256. While treating of this department of brick-making, it may be well to call attention to the imperfect mode of moulding them, which is owing entirely to the very wet state in wliich the clay is used ; for, in consequence of this circumstance, a shrinking takes place to such an extent, as to render it almost certain, that if the mass be bound in the least degree as it lays to dry, it will materially separate, and become cracked befoi'e it is carried to the clamp ; whereas if the mass, when properly mixed, was used much drier, and forced into the mould by mecha- nical means, the bricks so formed would be much more solid and ponderous, and when burned, would be found to be without cracks, and, consequently, more durable and valuable in every respect. In packing bricks so made into the clamp, it is found necessary to lay a course of bricks already burned at the bottom, in a very open manner, so that the spaces between may form flues 92 PRACTICAL BUICKLAYING. or passages for the air ; ami then upon these the first layer or course of unburned bricts are laid, having on them a layer of breeze, four or five inches thick ; other courses are laid on these, diminishing the quantity of breeze, or cinders, until a very thin sprinkling is laid between the upper courses, which is generally found sufficient for the purpose. When a clamp of bricks are burned in this way, it will be found that, for want of sufficient means to regulate the draught, some of them are completely vitrifyed, while others have received so small a degree of heat, tliat tlicy are very little harder than dried clay; while those wliich have received a due degree of heat will be found generally of a clean, sound, and good shape. Those that are fairly burned, are selected and sold under the name of Graij-stocks ; while those that are very slightly burned are selected for Place-bricks, being very frequently and improperly used on the inside part of walls. Place-bricks are usually redder than stocks, and much more soft and crumbly. Those that are partially vitrifyed lose their shape, and are sold under the name of Burrs. This sort of bricks lose their colour, and become, in many instances, little better than a mass of scoria : for in some cases, owing to particular circumstances, large portions of the clamp will be so com- pletely vitrifyed that it is impossible to separate the bricks from each other, and hence very considerable loss is experienced by the manufacturer. 257. The Gray Stocks, being made of a good earth, well wrought, and soundly burned, are com- monly used in the fronts of common buildings, for in the best brick-work the best marls are used; the Place Bricks, for the reasons given above, are therefore weaker and more brittle, and are introduced where they cannot be seen, and where little stress is laid upon them: the Red Bricks, of both kinds, are made of a particular earth, well wrought, and little injured by mixtures ; and they are used in fine work, in ornaments over windows, and in paving. These are frequently cut or ground down to a perfect evenness, and sometimes set in putty instead of mortar ; and thus set they make a very beautiful appearance. These are the kinds of bricks commonly used by us in building, and their difference is owing to variety in the materials. The Place Bricks and Gray Stocks are made in the neighbourhood of London, wherever there is a brick-work ; the two kinds of red brick, depending upon a par- ticular kind of earth, can be made only where that is to be had ; they are furnished from several places within fifteen or twenty miles of London. 258. We have already observed, that tliere are two or three other kinds of brick to be named, which are imported from other countries ; and there is also one of the red sort of cut- ting brick that is of our own manufacture, which, for its excellence, deserves to be particularly mentioned ; this is the Hedgerly Brick : it is made at a village of that name, of the famous earth called Hedgerly loam, well-known to the glass-makers and chymists. The loam is of a yellow- reddish colour, and very harsh to the touch, containing a great quantity of sand ; its particular excellence is, that it will bear the greatest violence of fire without injury : the chymists coat and lute their furnaces with this, and the ovens at glass-houses are also repaired or lined with it. INTRODLCTION. 93 where it stands all the fury of their heat without damage. It is brought into London for this purpose, under the name of Windsor loam, the village being near Windsor, and is sold at a high price. The bricks made of this are of the finest red that can be imagined. They are called Fire- Bricks, because of their enduring the fire ; and are used about furnaces and ovens in the same way as the earth. The foreign bricks above mentioned are the Dutch and Flemish Bricks and Clinkers : these are all nearly of a kind, and are often confounded together ; they are very hard, and of a dirty brimstone colour ; some of them not much unlike our Gray Stocks, others yellower. The Dutch are generally the best baked, and Flemish the yellowest. A§ to the Clinkers, they are the most baked of all, and are generally warped by the heat. These bricks are used for pecu- liar purposes ; the Dutch and Flemish for paving yards, stables, and the like ; and the clinkers for ovens. The fine red cutting English Bricks are twice, or more than twice, the price of the best Gray Stocks ; the Red Stocks half as dear again as the gray; and the Place Bricks, as they are much worse, so they are much cheaper, than any of the others. The Gray Stocks and Place Bricks are employed in the better and worse kinds of plain work ; the red stocks, as well as the gray, are used sometimes in this business, and sometimes for arches, and other more ornamental pieces : the fine red cutting bricks are used for ruled and gauged work, and sometimes for paving ; but the red stones are more frequently employed when a red kind is required for this purpose. 259. As the colour of bricks is an object of considerable importance, some being greatly preferable to others, we shall here observe, that in London and its environs, the gray stock for external is preferred, except for very superior buildings, and there the best Marls are always used. The gray colour of the stock brick is partly produced by an external coating of a peculiar kind of sand obtained in the river Thames, about and below Blackwall. This is brought up the river in barges, and carted to the different brick-works, where it is spread out in the air to dry. Previous to the mass of tempered clay being dropped into the mould, it is well rolled about in a quantity of this sand which forms an external coating, and when the mass leaves the mould, it is laid upon a board covered with the sand, and the upper surface is also covered with it by a sieve. In this way two purposes are effected ; namely, colour is given to the external surface of the brick, and, by being covered with sand, which becomes imbedded, it is in a better state to be handled or moved to the place where it is to be dried. It must be admitted, that much of the London clay is very impure, and from an admLsture with gravel, is very unfit for the purpose of making good sound bricks ; but it is also evident, that the present mode of making them in so moist a state, is bad in principle and highly pre- judicial in the practice. It has been suggested to make bricks with tempered clay and ashes in a much drier state, and l)y great compression force the materials into the mould, by which means they would obtain greater solidity and compactness previous to being dried. 94 PRACTICAL BRICKLAIING. Several patents have been obtained for applying machinery to this purpose, but, in using a plastic material, like tempered clay, so much difficulty was experienced in feeding the moulds, and separating the superfluous quantity of clay from the surface of the mould, so as to leave a well-formed mass therein, that they have all been given up and abandoned. Much difficulty was also experienced in protruding or delivering the compressed clay from the mould ; for this could only be effected by a piston that exactly fitted the mould internally, and when so adjusted, it was found to continue in that state but a very short time, having to act continually against sand, gravel, and pebbles of all shapes and forms, which very soon destroyed those parts of the machinery where considerable accuracy was most requisite. We must, in justice to the inventors of the various machines, declare that a more legitimate object for improvement does not offer itself to the attention of the mechanist or engineer than the one under consideration, and it is much to be lamented that success did not crown the efforts of those who made the attempt ; for, having seen some of the bricks burned that were so com- pressed, we have no hesitation in saying, they were by far the best, both for shape, soundness, and hardness, that we had ever seen. ~G0. The Red Cutting Brick, or fine red, is the finest of all bricks. In some places they are not at all acquainted with this ; in others, they confound it with the red stock, and use that for it ; though, where the fine red brick is to be had pure and perfectly made, the difference is five to three in the sale price between that and the red stock. The Red and Gray Stock are frequently put in gauged arches, and one as well as the other set in putty instead of mortar : this is an expensive work, but it answers in beauty for the regu- larity of the disposition and fineness of the joints, and has a very pleasing eflfect. The fine Red Brick is used in arches ruled and set in putty in the same manner ; and, as it is much more beautiful, is somewhat more costly. This kind is also the most beautiful of all in cornices, ruled in the same manner, and set in putty. The Gray Stocks of an inferior kind are also used in brick walls, 261. The Place Bricks are used in paving dry, or laid in mortar, and they are put down flat or edgeways. If they are laid flat, thirty-two of them pave a square yard ; but, if they are placed edgeways, it takes twice that number : in the front work of walls the Place Bricks should never be admitted, even in the meanest building. That consideration, therefore, only takes place in the other kinds : and the fine Cutting Bricks come so very dear this way, that few people will be brought to think of them ; so that it lies, in a great measure, between the Gray Stocks and Red Stocks. Of these the gray are most used ; and this not only because they are cheaper, but, in most cases where judgment is preferred to fancy, they will have the pre- ference. We see many very beautiful pieces of workmanship in Red Brick ; but this should not tempt the judicious architect to admit them into the front walls of buildings. In the first place, the colour itself is fiery and disagreeable to the eye ; and, in summer, it has an appearance of heat that is INTRODUCTION. 95 very disagreeable ; for this reason it is most improper in the country, though the oftenest used there, from the difficulty of getting gray. But a farther consideration is, tliat, in the fronts of most important buildings, there is more or less stone-work ; now, as there should be as much conformity as can be attained between the general nakedness of the wall and those several ornaments which project from it, the nearer they are of a colour, the better they always range together; and if we cast our eyes upon two houses, the one of red and the other of gray brick, where there is a little stone-work, we shall not be a moment in doubt which to prefer. There is something harsh in the transition from the red brick to stone, and it seems altogether unnatural ; in the other, the Gray Stocks come so near the colour of stone, that the change is less violent, and they sort better together. Hence, also, the Gray Stocks are to be considered as best coloured when they have least of the yellow cast ; for the nearer they come to the colour of stone, when they are to be used together with it, it is certainly the better. Where there is no stone-work, there generally is wood ; and this, being painted white, as is commonly the prac- tice, has yet a more violent contrast with red brick than the stone-work : the transition is more sudden in this than in the other ; but, on the other hand, in the mixture of gray bricks and white paint, the colour of the brick being soft, there is no violent change. The Gray Stocks are now made, of prime quality, in the neighbourhood of London. The late Duke of Norfolk had the bricks brought from his estate, in that county, for building the front of his house, in St. James's-square ; but the event shews that his Grace might have been better supplied near at hand, as to colour, with equal hardness. The greatest advantage that a Gray Stock, which is the standard brick, can have, is in its sound body and pale colour ; so that the pruicipal thing the brick-maker ought to have in view, for the improvement of his profession, is the seeking for earth that will burn pale, and that will have a good body, and to see it has sufficient working. The judicious builder will always examine his bricks in this light, and be ready to pay that price which is merited by their goodness. The utility and common practice of building all our edifices of brick, both in London and the country, arises from motives too obvious to need a definition; since it is generally considered to be much the cheapest, as well as the most eligible substance that can be invented for the purpose, both in point of beauty and duration, and inferior to nothing but wrought stone. 96 PKACTICAL BRICKLWING. CHAPTER I. ON THE NATURE AND PROPERTIES OF BRICK BOND. 262, Bricks are laid in a varied, but regular, form of connection, or Bond, as exhibited in Plate XXIX, c. The mode of laying them for a 9-inch walling, shown m fgurc 1, being denominated English Bond; and figure 2, Flemish Bond, Figure u is English Bond, in a brick and a half, or 14-inch walling ; and figure 4, Flemish Bond, in the same. Figure 5 represents another method of disposing Flemish Bond in a 14-inch wall. Figure G, English Bond, in an IS-inch, or two brick thick, wall; and figure 7, English Bond, in a two and half brick thick wall. Figures 8, 9, 10, 11, represent courses, in square pairs, of Flemish Bond. In each pair, if one be the lower course, the other will be the upper course. The bricks, having their lengths in the thickness of the wall, are termed Headers, and those which have their lengths in the length of the wall are Stretchers, By a Course, in walling, is meant the bricks contained between two planes parallel to the horizon, and terminated by the faces of the wall. The thickness is that of one brick with mortar. The mass formed by bricks laid in a radiated position, for arches or vaults, is also denominated a Course. The disposition of bricks in a wall, of which every alternate course consists of headers, and of which every course between every two nearest courses of headers consist of stretchers, con- stitutes English Bond. The disposition of bricks in a wall, (except at the quoins,) of which every alternate brick in the same course is a header, and of which every brick between every two nearest headers is a stretcher, constitutes Flemish Bond. 265. It is, therefore, to be understood that English Bond is a continuation of one kind throughout, in the same course or horizontal layer, and consists of alternate courses of headers and stretchers, as shown in the plate ; the headers serving to bind the wall together, in a lon- gitudinal direction, or lengthwise, and the stretchers to prevent the wall splitting crossways, or in a transverse direction. Of these evils the first is of the worst kind, and therefore the most to be feared. A respectable writer on this subject has said, that the old English mode of brick-work affords the best security against such accidents ; as work of this kind, wheresoever it is so much under- mined as to cause a fracture, is not subject to such accidents, but separates, if at all, by break- ing through the solid brick, just as if the wall were composed of one piece. NATURE AND PROPERTIES OF BRICK BOND. "07 The antient brick-wovk of the Romans was of this kind of bond, but the existing specimens of it are very thick, and have three, or sometimes more, courses of brick, laid at certain inter- vals of the height, stretchers on stretchers, and headers on headers, opposite the return wall, and sometimes at certain distances in the length, forming piers, that bind the wall together in a transverse direction ; the intervals between these piers were filled up, and formed panels of rubble or reticulated work (articles 70 and 71); consequently, great substance, with strength, were economically obtained. 264. It will, also, be understood that Flemish Bond consists in placing, in the same court-e, alternate headers and stretchers, a disposition considered as decidedly inferior in every thir.cr but appearance, and even in this the difference is trifling; yet, to obtain it, strength is sacri- ficed, and bricks of two qualities are fabricated for the purpose ; a firm brick often rubbed and laid in what the workmen term a putty-joint for the exterior, and an inferior brick for the interior, substance of the wall ; but, as these did not correspond in thickness, the exterior and interior surface of the wall would not be otherwise connected together than by an outside heading-brick, here and there continued of its wliole length ; but, as the work does not admit of this at all times, from the want of agreement in the exterior and interior courses, these headers can be introduced only where such a correspondence takes place, which, sometimes, may not occur for a considerable space. Walls of this kind consist of two faces of four-inch work, with very little to connect them together, and what is still worse the interior face often consists of bad brick, little better than rubbish. The practice of Flemish Bond has, notwithstanding, continued from the time of William and ]Mary, when it was introduced, with many other Dutch fashions, and our workmen are so infatuated with it, that there is now scarcely an instance of the old English Bond to be seen. The frequent splitting of walls into two thicknesses has been attributed to the Flemish Bond alone, and various methods have been adopted for its prevention. Some have laid laths or slips of hoop-iron, occasionally, in the horizontal joints between the two courses; others have laid diagonal courses of bricks at certain heights from each other ; but the effect of the last method is questionable, as, in the diagonal course, by their not being continued to the outside, the bricks are much broken where the strength is required. Other methods of uniting complete Bond with Flemish facings have been described, but they have been found equally unsuccessful. In fgures 2 and 4, {Plate LXXXV,) the interior bricks are represented as disposed with intention to unite these two particulars ; the Flemish facings being on one side of the wall only ; but this, at least, falls short of the strength ob- tained by English Bond. Another evil attending this disposition of the bricks is, the difficulty of its execution, as the adjustment of the bricks in one course must depend on the course beneath, which must be seen or recollected by the workman ; the first is difficult from the joints of the under-course being covered with mortnr, to bed the bricks of the succeeding course; 2c 9S PRACTICAL PRICKLAi'ING. and, for the workman to carry in his mind the arrangement of the preceding course can hardly be expected from him ; yet, unless it be attended to, the joints will be frequently brought to correspond, dividing the wall into several thicknesses, and thus rendering it subject to splitting, or separation. But, in the English Bond, the outside of the last course points out how the next is to be laid, so that the workman cannot mistake. The outer appearance is all that can be urged in favoui* of Flemish Bond, and many are of opinion that, were the English mode executed with the same attention and neatness that is bestowed on the Flemish, it would be considered as equally handsome ; and its adoption, in preference, has been strenuously recommended. In forming English Bond, the following rules are to be observed : 1st, Each course is to be formed of headers and stretchers alternately. 2d, Every brick in the same course must be laid in the same direction : but, in no instance, is a brick to be placed with its whole length along the side of another, so that their extremities may coincide two and two ; but to be so situated that the end of one may reach to the middle of the others which lie contiguous to it, excepting the outside of the stretching-course, where three-quarter bricks necessarily occur at the ends, to prevent a continued upright-joint in the face-work. 3d, A wall, which crosses at a right-angle with another, will have all the bricks of the same level course in the same parallel direction, which completely bonds the angles, as shown bv figures 1, 3, and 6. 265. The great principle in the practice of brick-work lies in the proclivity or certain motion of absolute gravity, caused by a quantity or multiplicity of substance being added or fixed in resistible matter, and which, therefore, naturally tends downwards, according to the weight and power impressed. In bricklaying, this prochvity, chiefly by the yielding mixture of the matter of which mortar is composed, and cannot be exactly calculated, because the weight of a brick, or any other substance, laid in mortar, will naturally decline according to its sub- stance or quality; particular care should, therefore, be taken, that the material be of one regular and equal quality all through the building ; and, likewise, that the same force should be used to one brick as another ; that is to say, the stroke of the trowel : a thing or point in prac- tice of much more consequence than is generally imagined ; for, if a brick be actuated by a blow, this will be a much greater pressure upon it than the weight of twenty bricks. It is, also, especially to be remarked, that the many bad effects arising from mortar not being of a proper quality should make masters very cautious in the preparation of it, as well as the certain quan- tity of materials of which it is composed, so that the whole structure may be of equal density, as nearly as can be effected. Here we may notice a particular which often causes a bulging in large flank-walls, especially when they are not properly set off on both sides ; that is, the irregular method of laying bricks too high on the front edge : this, and building the walls too high on one side, without continuing NATUUE AND PROPERTIES OF BRICK BOND. 99 the other, often causes the defects. >Jot\vithstanding, of the two evils, this is the least; and bricks should incline rather to the middle of the wall, that one half of the wall may act as a «hore to the other. But even this method, carried too far, will be more injurious than beneficial, because the full width of the wall, in this case, does not take its absolute weight, and the gravity «s removed from its first line of direction, which, in all walls, should be perpendicular and united ; and it is farther to be considered that, as the walls will have a superincumbent weight to bear, adequate to their full strength, a disjunctive digression is made from the right line of direction; the conjunctive strength becomes divided; and, instead of a whole or united support from the wall, its strength is separated in the middle, and takes two lateral bearings of gravity ; each insufficient for the purpose ; therefore, like a man overloaded either upon his head or shoulders, naturally bends and stoops to the force impressed ; in which mutable state the grievances above noticed usually occur. 2GG. Another great defect is frequently seen in the fronts of houses, in some of the principal ornaments of Brick-work, as, arches over windows, &c., and which is too often caused by a want of experience in rubbing the bricks ; which is the most difficult part of the branch, and ought to be very well considered : the faults alluded to, are the bulging or convexity in which the faces of arches are often found, after the houses are finished, and sometimes loose in the key or centre bond. The first of these defects, which appears to be caused by too much weight, is, in reality, no more than a fault in the practice of rubbing the bricks too much off on the insides ; for it should be a standing maxim (if you expect them to appear straight under their proper weight) to make them the exact gauge on the inside, that they bear upon the front edges ; by which means their geometrical bearings are united, and all tend to one centre of gravity. The latter observation, of camber arches not being skewed enough, is an egregious fault ; because it takes greatly from the beauty of the arch, as well as its significancy. The proper method of skewing all camber arches should be one-third of their height. For instance, if an arch is nine inches high, it should skew three inches ; one of twelve inches, four ; one of fifteen inches, five; and so of all the numbers between those. Observe, in dividing the arch, that the quantity consists of an odd number : by so doing, you will have proper bond ; and the key-bond in the middle of the arches ; in which state it must always be, both for strength and beauty. Likewise observe, that arches are all drawn from one centre ; the real point of camber arches 's got from the above proportion. First, divide the height of the arch in three parts ; one is the dimensions for the skewing ; a line drawn from that through the point at the bottom, to the perpendicular of the middle arch, gives the centre to which all the rest must be drawn. 200 PKACTICAL BUlCr.LAYlNG. CHAPTER IT. ON THE CONSTRUCTION OF WALLS. ^67. FOUNDATIONS. — If a projected building is to have celiarj), or under-ground kitchens, there will commonly be found a sufficient bottom, without any extra process, for a good solid foundation. When this is not the case, the remedies are to dig deeper, or to drive in large stones with the rammer, or by laying in thick pieces of oak, crossing the direction of the wall, and planks of the same timber, wider than the intended wall, and running in the same direction with it. The last are to be spiked firmly to the cross-pieces, to prevent their sliding, the ground having been previously well rammed under them. The mode of ascertaining if the ground be solid is by the rammer ; if, by striking the ground with this tool, it shake, it must be pierced with a borer, such as is used by well-diggers ; and, havinff found how deep the firm ground is below the surface, you must proceed to remove the loose or soft part, taking care to leave it in the form of steps, if it be tapering, that the stones may have a solid bearing, and not be subject to slide, which would be likely to happen if the ground were dug in the form of an 'Inclined plane. If the ground prove variable, and be hard and soft at different places, the best way is to (m-n inverted arches from one hard bearing to another, by bringing up the piers, which carry llie principal weight of the building, to the intended height and thickness, and then turning the arches, as shown in figure 18, {Plate XXIX, e.) In this case, it is clear that the piers cannot sink without carrying the arches, and consequently the ground on which they he, with them. This practice is excellent, and has been very successful in such cases, and should, therefore, be general, wherever required. When the hard ground is to be found under apertures only, build your piers on these places, and turn arches from one to the other. In the construction of the arches, some attention must be paid to the breadth of the insisting pier, whether it will cover the arch or not; for, suppose the middle of the piers to rest over the middle of the summit of the arches, then the narrower the piers, the more curvature the supporting arch ought to have at the apex. When arches of suspension are used, the intrados ought to be clear, so that the arch may have the full effect: but, as already noticed, it will also be requisite here that the ground on which the piers are erected be uniformly hard ; for it is better that it should be uniform, though not so hard as might be wished, than to have it unequally so : because, in the first case, the piers would de- scend uniformly, and the building remain uninjured ; but, in the second, a vertical fracture would take place, and endanger the whole structure. CONSTRUCTION OF WALLS. 101 368. WALLS, &c.— The foundation being properly prepared, the choice of materials is to be considered. In places much exposed to the weather, the hardest and best bricks must be used, and the softer reserved for in-door work, or for situations less exposed. In slaking lime, use as much water only as will reduce it to a powder, and only about a bushel of lime at a time, covering it over with sand, in order to prevent the gas from escaping. This is a better mode than slaking the whole at one time, there being less surface exposed to the air : for, in thus suf- fering the gas to escape, we lose that virtue of the hme which constitutes its hardening quaHty. Before the mortar is used, it should be beaten three or four times over, so as to incorporate the lime and sand, and to reduce all knobs or knots of lime that may have passed the sieve. This very much improves the smoothness of the lime, and, by admitting air into its pores, will make the mortar stronger : as little water is to be used in this process as possible. Whenever mortar is suffered to stand any time before used, it should be beaten again, so as to give it tenacity, and prevent labour to the bricklayer. In dry hot summer-weather use your mortar soft ; in winter, rather stiff. In laying bricks in dry weather, by wetting the bricks, or by causing water to be thrown over them before they are used, will greatly add to the strength and durability of the work. Few workmen are sufficiently aware of the advantage of wetting bricks before they are used ; but experience has shown that works in which this practice has been followed have been much more durable than others wherein it has been neglected. It is particularly serviceable where work is carried up thin, and in putting in grates, furnaces, &c. In the winter season, as soon as frosty weather sets in, cover your wall with straw or boards ; the first is best, if well secured ; as it protects the top of the wall, in some measure, from frost, which is very prejudicial, particularly when it succeeds much rain ; for the rain penetrates to the heart of the wall, and the frost, by converting the water into ice, expands it, and causes the mortar to assume a short and crumbly nature, and altogether destroys its tenacity, before it has acquired a sufficient hardness to resist it. In working up a wall, it is proper not to work more than four or five feet at a time ; for, as all walls shrink immediately after building, the part which is first brought up will remain com- paratively stationary ; and, when the adjoining part is raised to the same height, a shrinkmg m the latter will take place in a much greater degree than in the former, which will separate from the latter, causing a crack, which will become more evident as the work proceeds. In carrying up any particular part, each side should be sloped off, to receive the bond of the adjoining work on the right and left. Nothing but absolute necessity can justify carrying the work higher, in any particular part, than one scaffold ; for, wherever it is so done, the workman should bo answerable for all the evil that may arise from it. 269. The distinctions of Bond have already been shown, and we shall now detail them more particularly ; again referring to Plate XXIX, e, in which the arrangement of bricks, in depths of different thicknesses, so to form English Bond, is shown in figures 1, 3, 6, and 7. 3d 702 PRACTICAL BRICKLAYING. The bond of a ivall of nine inches is represented by fig. 1 . In order to prevent two upright or vertical joints from running over each other, at the end of the first stretcher from the corner, place the return corner-stretcher, which is a header, in the face of the wall in which the stretcher is in below, and occupies half its length ; a quarter-brick is placed on its side, forming together 6J inches, and leave a lap of 2J inches for the next header, which lies with its middle upon the middle of the header below, and forms a continuation of the bond. The three-quarter brick, or brick-bat, is called a closer. Another way of effecting this is, by laying a three-quarter bat at the corner of the stretching- course ; for, when the corner-header conies to be laid over it, a lap of 2J inches will be left at the end of the stretchers below for the next header ; which, when laid, its middle will come over the joint below the stretcher, and in this manner form the bond. In a fourteen-inch or brick-and-half wall, (fig. 3,) the stretching-course upon one side, is so laid that the middle of the breadth of the bricks, upon the opposite side, falls alternately upon the middle of the stretchers and upon the joints between the stretchers. In a two-brick wall, (Jig. G,) every alternate header, in the heading-course, is only half a brick thick on both sides, which breaks the joints in the core of the wall. In a two-brick and a half wall, (Jig. 7,) the bricks are laid as shown in figure 6. Flemish Bond, for a nine-inch wall, is represented m figure 2, wherein two stretchers lie between two headers, the length of the headers and the breadth of the stretchers extending the whole thickness of the wall. In brick-and-half Flemish bond, (fig. 4,) one side being laid as in figure 2, and the opposite side, with a half-header, opposite to the middle of the stretcher, and the middle of the stretcher opposite the middle of the end of the header. Figure 5 exhibits another arrangement of Flemish Bond, wherein the bricks are disposed alike on both sides of the wall, the tail of the headers being placed contiguous to each other, so as to form square spaces in the core of the wall for half-bricks. The Face of an upright-wall, English Bond, is represented by figure 19, and that of I'lemish Bond, by figure 20. 270. Brick-nogging is a mode of constructing a wall with a row of posts or quarters, dis- posed at from eighteen inches to three feet apart, with brick-work filling up the intervals. In this mode the wall is, generally, either of the thickness or breadth of a brick, and the wood- work projects on both sides with the faces of the brick-work about three-quarter's of an inch, in order to make a proper allowance for the irregularity of the splitting of the lath. Thin pieces of timber, called nogging-pieces, laid horizotaliy from post to post, are so disposed as to form brick-work between every two posts or quarters, into several compartments in the height of the story ; each piece being inserted between two courses of brick, with its edges flush with the wall. 271. Cornices. — In respect of brick cornices, many pleasing combinations may be made; thus, fig. 21 shows the rudiments of a Doric entablature ; and fig. 22, that of a dentil cornice. CONSTRUCTION OF WALLS. 103 272. As the building of high brick-walls in situations where the ground is infirm, or where sound ground is covered with deposited soil, so as to be executed at the cheapest rate with superior strength and durability, is of the greatest importance to those who may have occasion to erect such walls ; we shall, therefore, make no apology in laying before our readers the follow- ing description, though particularly applicable to the surrounding walls of Coldbath-Fields Prison, including the Female Penitentiary, may be generally applied to all others under the like circumstances. Fig. 1, Plate XXIX, exhibits a general plan of Coldbath-Fields Prison, ABCD is the sur- rounding wall of the old prison, e,f,g,h,i,k,l,m,'&, the surrounding wall of the intended Penitentiary, which was built upon ground over which was deposited a soil, varying from twenty to six feet in depth. The small circles exhibit the plans of the piers upon which circular buttresses or counterforts were erected to strengthen the wall, at a distance from each other, varying from 28 to 36 feet, according to circumstances. Fig. 2, a portion of the new and old walls, a, b, c, d, being the elevation of the new part, exhibiting the foundation and the super- incumbent wall. This portion of the new wall exhibits six piers. Over every second pier a circular buttress, projecting from both faces of the wall, was erected ; the part of the ele- vation, fig. 2, exhibits three of these buttresses, g, h, c, i, (Jig. 2.) exhibits a portion of the prison-wall with one of the buttresses. The plans of both parts of this elevation is exhibited at/g. 3; the plan of the buttresses of the old wall being rectangular, whereas that of the new wall is circular. Fig. 4, exhibits the elevation to a large scale of a portion of the new wall, containing one buttress and a part of another, with one aperture and part of another, in order to show the brick-work in the foundation, and superincumbent part of the wall, to the greatest advantage, as also the use of the invert and insistant arches. The plan of this is shown below, at Jig. 5. The following attestation, delivered to the president and members of the institution of civil engineers, by a gentleman who was cormected with the building of the walls here referred to, will show the great advantage of such a mode of construction. 273. " A piled and sleepered foundation (unless it had been of oak) must soon have perished, and the expence of such a foundation would have been greater than the whole of the wall and coping taken together. The advantage of invert and insistant arches, in a work of this kind, is a more efficient footing than stone landings, and the latter gives a longitudinal connection to the work, which is particularly desirable to consolidate it in that direction. " The circular piers give the greatest lateral stability with the least quantity of work, present- ing a convenient form towards a public way, and secure from escapes on the prison-side by avoiding angles. This disadvantage, of piers placed on one side, arises from the equilibrium being destroyed, in all cases that have been examined of this kind. The wall inclines towards the side on which the piers are placed. By this method, shown on the drawing, we are enabled 101 PRACTICAL BRICKLAYING. to lay foundations at considerable depths, without adding much additional weight, and thereby a permanent foundation by using only imperishable materials. Another advantage obtained by this method arose from having occasion to raise the ground in some places fourteen feet ; with these large apertures the ground settles uniformly, without pressing unequally against either side of the wall, and thereby preserving its vertical position. " The motives which directed this plan were two : viz. the failui'e of piles and sleepers in some foundations that had been taken up, about three years since, within the prison-walls ; and secondly, economy : for, if pile and sleeper foundations had been adopted, the expense would liave been increased at least one-third. It would be superfluous to go into the detail of exe- cution ; suffice it to say, that, with good materials and workmanship, a work upon this prin- ciple ■would possess a durability equal to the most expensive mode of execution." CHAPTER III. * ON THE CONSTRUCTION OF ARCHES FOR CYLINDRICAL VAULTS. 274. An Arch, in brick-work, is a mass of bricks so arranged, that, in the profile, or right section, the under line or intrados is generally a curve, which is always concave towards the aperture, and the joints between the bricks radiate towards a centre, in such a manner that each joint ought always to be perpendicular to the curve. In order to form a rectangular aperture, the under-Iine, which terminates the head of the right section, is a straight line. In such a case, the joints must still radiate to a centre in the middle of the breadth of the aperture; but these joints cannot be perpendicular to the soffit, as was the case when the intrados or soffit was a curved surface. An arch does not always imply a mass of bricks or stones supported at the extremities, and terminating upon a concave surface over a hollow. The principle of a brick or stone arch arises from the radiating directions of the joints, which, in fact, divides the arch or vault into separate bricks, in the form of the frustum of a wedge, of which the lesser ends form the intrados of the arch. It is easy to see that none of these bricks, thus separated by the radiating joints, can descend, for the aperture through which any brick has to pass being narrower at tlie bottom than at the top, will not admit of the wide end of the wedge to pass through it, nor even to descend to any distance, however small. Hence a mass of bricks or stones, connected by radiating surfaces, will support each other, even though the intrados may be a plane surface ; what is called the curve of equilibrium being within the solid mass. Arches are therefore of several kinds, when the profiles are circular, as straight arches, semi-circular arches, and segmental arches ; which are also called scheme arches. ARCHES FOR CYLINDRICAL VAULTS. 105 The springings of a semi-civcular arch are in a plane parallel to the horizon ; the springings of a scheme arch are in two planes, each being at right-angles to the tangent plane to the in- trados at the commencement of the curve. The springings which are neither parallel nor perpendicular to the horizon, are called, in the technical language of the bricklayer, skew-backs. Straight arches must have skew-backs, as well as scheme-arches. 275. Fig. 1.', exhibits the right section or profile of an arch for the head of an aperture, which forms the intrados of a straight arch ; the manner in which these joints are drawn will be shown in the following description (see Jig. 17). Upon the width, AB, of the aperture as a base, describe an equilateral triangle, and from the vertex, C, with a radius equal to the thickness of a brick, describe a small circle. Draw DE, the extrados of the arch, at such a distance from the intrados as is equal to the breadth of the arch, which, in this example, is equal to the height of four courses of bricks in the face of the wall, and draw the skew-backs, AB and DE, one at each extremity of the arch. Draw a line parallel to one of the skew-backs, (which ought to be a tangent to the small circle,) cutting the intrados in F, and draw the straight Une CF. Find the point G in the same manner, and draw GC, and so on to the middle, when the operation will be complete. Fig. 14, is the profile of the head of an aperture with a part of each jamb, the head being a scheme-arch. It is contained between two concentric circles and the springing-lines, which are portions of the radii of these circles. Fig. 15, is a semi-circular arch. 276. Fig. 16, a semi-elliptic arch, struck from two centres, A and B, having the longer axis in a position parallel to the horizon. The method of describing elliptic arches is as follows (see Plate XXIX. g.) Let AB be the span of the arch, and CD its height, from the middle of AB, and perpendicular thereto. Draw A a- and Da: respectively parallel to CD and CA, and divide Ax and AC each into three equal parts, by the two intermediate points, 1, 2. Make Cz equal to CD, and from the points 1, 2, in Ax, draw straight lines to the point D, intersecting straight lines drawn from the points 1, 2, in AC, in the points y and n. Make the angle Dtih equal to the angle wDC, and prolong DC to meet nh in h. Join yn, or suppose yn to be joined, and bisect 1/nhy a. perpendicular meeting nh in i. Join yi, intersecting AB in k, and let nh inter- sect AB in /. In CB, make C r equal to C I, and from h, through r, draw h u. In k r, make liq equal to hi, and in CB, make Cs equal to Ck. Join qs, and prolong qs to t. From the centre h, with the radius AD, describe the arc nu, and from the centres i and q, describe the arcs ny and tit, and from the centres k and s describe the arcs y A and , &c., per- pendicular to kg, and make the lengths of the right lines, x \,y%z 3, &c., equal to the lengths nc, od,pe, &c., and through the points 1, 2,o....g, draw the curve 1, 2, 3..../T, which will be the section required. Fig. 1, No. 2, is an elevation corresponding to the narrow side of a severy. CHAPTER V. ON THE CONSTRUCTION OF BRICK NICHES. 293. A Niche is a recess in a wall, either for ornament, or for the purpose of containmg a sJatue. The surfaces of niches are generally concave. The most elegant are those which are formed 1'y cylindrical and spherical surfaces, the back being formed by the cylindrical surface, and the canopy, or head, by the spherical surface. The portion used of the cylindric surface is either that which would be terminated by a diametrical plane, or which would be a less portion of the surface terminated by a plane parallel to the axis, the terminating plane being the face of the wall. The axis of the cylindric back is vertical, and the centre of the sphere is in the upper extremity of the axis of the cylinder, and the spherical and cylindrical surfaces meet each other in a great circle of the sphere contained in a plane perpendicular to the axis of the cylinder. The bottom of the niche is generally horizontal, sometimes in the plane of the floor, but more commonly raised above the plane of the floor. The niche, figure 2, plate XXIX. ^, is taken from that in the front of the green-house, Ken- sington-Gardens, which is one of the best-executed pieces of brick-work in this country. Numbers 2 and 3 exhibit the bond of the courses laid according to the Flemish manner ; No. 4 exhibits a vertical section through the centre of the spherical surface, and perpendicular to the face of the wall. sot. The practice of constructing a niche in brick-work is the most difiicult part of the profession, on account of the very thin size which the bricks are obliged to be reduced down to the inner circle, as they cannot extend beyond the thickness of one brick in the arch sur- rounding the crown, it being usual, as well as much the neatest method, to make all the courses radiate. TUNNELS AND DRAINS. 121 The most familiar way to reduce this method to practice, is to draw the front, back, &c., and make a templet of paste-board. After the arch has been divided into the number of bricks, observe that one templet for every radiating course will answer the front, and one for the side of the brick. At the top of the straight part, from which the niche takes its spring, make a circle, 8 or 9 inches diameter, and cut this, as well as the former, out of pasteboard, and divide it into the same number of parts as the outward circle terminating in the front of the wall. From this will be found the width of the front-templet at the bottom. The reason of introducing this inner circle is to cut off the thin ends at their conjunction, as they would otherwise require to ter- minate in straight hnes in the centre of the niche, and therefore the bricks would be formed into such very acute angles, that they would be liable to break off in working them ; it being impos- sible to make the thin ends stand at a thickness less than half an inch. Within the inner circle, the bricks must be laid so that their longest dimensions may be horizontal and parallel to the plane of the front from which the niche recedes. It will be neces- sary to have one templet made convex, in order to try the faces of the bricks, as well as to set them after being properly shaped. The stone upon which the faces of the bricks are rubbed, must be cut at one end in the exact form of the niche, or otherwise it will be impossible to face them as they ought to be. The level of the flat sides of the bricks will be obtained by dividing the back into an equal number of equal parts as in the front, and the radiating lines must be all struck from the centre. From the circle of the front and the face of the niche set a bevel, which will answer to the sides of the whole, always taking care that the bricks hold their full gauge at the back ; for if this circumstance is neglected, much trouble will attend the execution. Works of this nature require a good price, in proportion to the great skill and attention required in the execution. The portion of brick-work, which shows a semi-circle in the front, is called by the name of Trompilion ; this is made up of several courses, of which the fronts of the bricks must be all curved, so that, when placed and fixed, they must form the true spherical surface in which it was intended that the niche should form. CHAPTER Vr. ON THE CONSTRUCTION OF TUNNELS AND DRAINS. General Observations. 295. A Tunnel is an excavation made under ground, terminating at each extremity in the surface of the earth, for the purpose of giving passage for some moveable thing or things. 2i 122 PRACTICAL BRICKLAYING. Such a communfcation would either be found convenient or necessary, where some intervening object would render the conveyance dangerous or extremely expensive, or even, in some cases, impossible. By means of a tunnel, a stream of water may be conducted from a given entrance on one side of a hill to a given outlet on the other ; or a passage of communication between the opposite shores of a deep river, without interrupting its navigation, may be effected. If the object of the tunnel be to conduct vessels by means of water, it is evident that the bed of the fluid must be nearly in a horizontal plane, and if it be required to effect the passage in the least time, its direction ought to be in a right line. This mode of communication would also be found necessary in conducting a roadway through a hill, which would otherwise be found insurmountable. The figure of the section of such an aperture will depend greatly upon the soil through which it is cut ; but whatever be the form of the right section through any particular point, the same figure must invariably continue, unless the quality of the substance is found to vary. In this case, the figure of the section must be such as will meet every contingency. The sides of the aperture ought always to be lined with brick or stone, and the top ought to be arched. If the soil be sand, a tunnel cannot be constructed so as to support the superincumbent mass ; and therefore, in this case, such a conveyance, though ever so desirable, ought never to be at- tempted. If the soil be clay or solid earth, the figure of the right section of the tunnel must be of such a form all round that the mutual pressure upon the parts may balance one another ; or by making allowance for the convenience of practical operations, the figure ought to be as near as possible to the curve of equilibrium for the support of such a surrounding mass. If the substance be rock through which a tunnel is to be cut, it will not be necessary to form an arch all round, the bottom may be paved in the usual manner, and the sides which form walls may be built upon the solid rock. In executing a tunnel, it is evident that no more of the ground should be cut away than is absolutely necessary to effect a part of sufficient length for the operation of walling and arching, and thus the building and the excavation must be carried on alternately at regular intervals. The lengths excavated at a time before the brick-work is built must depend upon the nature of the ground, and may be from 3 or 4, to 7 or 8, feet, in the fine of direction of the tunnel, observing the quality of the ground with the utmost circumspection, so as not to endanger its falling by taking away too much at a time. Instead of making one continued arch all round the tunnel, and in order to save the mate- rials, the bottoms are most frequently constructed in the figure of an inverted arch, being a segment considerably less than a semi-circle. The sides and top, however, ought to be carried round from one extremity of the pavement, or inverted arch, to the other extremity, in such a curve as will be most suitable to the surrounding pressure of the earth, observing to form a commodious aperture for passage. With regard to the supporting of the earth at the crown in the most sufficient manner, it will depend upon the nature of the soil, and upon the circum- TUNNELS AND DRAINS. 123 stances attending the execution of the work. This will be best understood by a reference to particular examples : in general, however, this may be done by horizontal bars placed in the direction of the tunnel, having their remote ends inserted a foot or more in the solid earth, and their other ends supported by the portion of the arch last constructed, or by means of upright shores from the pavement. In these constructions, it is necessary that the joints should be as close as possible ; there- fore, in order to effect this with brick materials, as all the opposite faces of a brick are in parallel planes, the joints cannot radiate as they ought to do ; hence the opposite sides of any number of courses built with bricks closely-jointed, would also be comprised between parallel planes, and consequently such a position of bricks could never form an arch. In order, however, to render the use of common bricks practicable, the arch would require to have a very great radius of curvature, and only a few courses (their number depending upon that cur- vature) built at a time between two courses of wedged-bricks made for the purpose ; these wedged-bricks must be so constructed as to have their sides, which comprise the intenals for the common bricks, in parallel planes. The figure of the arch would thus become a polygon of a great number of sides, the general effect of the intrados could not therefore be distinguished from a curved surface. The skew-backs at the extremities of the pavement may be made of hard stone, so as to answer to the radiations of the brick-work upon each side. Description of the Tunnel at the Regent's Canal. 296. Plate XXlX.g, figures 4 and 5, exhibits a section of this tunnel, from a drawing by Mr. Provis, who received a premium of one hundred guineas from the company appointed to direct the work. By inspecting/^. 4, it will be perceived that the curvature of the bottom, top, and sides, are struck from four centres ; the thickness of the bottom is 1 \ bricks in length, and all the other parts two bricks. The bricks are of the common sort, with the exception of one course in eight in the bottom and sides, and one course in six in the arch at the top. These bricks which separate the common bricks radiate in such a manner, as to leave the sides of the intervals between every two of them in parallel planes, so that each interval may contain the number of common bricks between the parallel plane surfaces of the radiating ones : these radi- ating bricks were all made for the express purpose. As common bricks have their sides in parallel planes, and as it is of the greatest consequence that the joints of mortar should be as thin as possible, particularly on the lower part adjacent to the convex surface, forming the ceil- ing or soffit of the arch, which has to sustain the greatest pressure, these radiating bricks are absolutely necessary to prevent the joints from departing too much from the radiating lines. In executing a tunnel, it is essential that no more of the ground should be cut away than is absolutely necessary; having excavated the first length, the leading frames must be already pre- 124 PRACTICAL BRICKLAYING. pared similar to those sliown m Jig. 5; they may be made of li-inch deal; then having correctly obtained the level of the bottom of the tunnel, and the central range or line of direction which is intended to pass from one extremity of the tunnel to the other, lay the first course of brick- work at the bottom by means of this line, with two or three courses on each side of it, in order to give it a firm support as at I, Jig. 5. Upon these courses set up the leading frame at each end, the centre of the under-curve of which must coincide with the line of direction on tlie top of the middle course of bricks. Having placed the leading frames in their proper positions, secure them to their places as exhibited in Jig. 5 ; then execute the brick-work of the bottom on each side of the central or directing courses, making the joints between the bricks with as tliin a substance of mortar as possible, not forgetting to put in the courses of wedged or ra- diating bricks at their proper distances from each other; and upon the margins at E, E, ^g. 4, lay the skew-backs, which may be made either of bricks or stones, and upon the skew-backs carry up the curved sides or walls as high as the tops of the leading frames, ob- serving, as before, to insert the wedged course of bricks in their proper places, and if any space should remain between the natural ground and the brick-work, fill the vacuity up with solid earth, well condensed by ramming it, or otherwise the space must be wrought up with solid brick-work. In the course of these operations, the next thing to be done is to set the centre for the arch at the top. It must consist of two single ribs without any attached covering, and may be of any common construction, so as to be of the proper curve and sufficiently strong. As the brick- layers must stand below the arch, in order to turn it, instead of being above it, the covering of the centre must consist of single straight pieces of wood, about three inches square, and must be laid loose on the circular ribs by one at a time as the courses proceed, till the work arrives as high as the supporting bars F, F, &c., which must be taken out one at a time, as the brick- work approaches them, taking care all the way to stop up firmly every vacuity that may be between the top of the brick-wovk of the arch and the soil immediately above it. The arch is at last keyed in with wedged-bricks, which must be driven upwards very tight. When the first length is completed, the leading frames and centre are moved out of the way, m order that the miners may proceed to excavate the next length, which, when done, the bricklayers proceed again as before, with this difference, that only one leading frame is required for the next and each succeeding length ; as the brick-work, already executed, will answer all the purposes of a second leading frame. Fig. 4, shows the arch as completely finished ; and Jig. 5, exhibits a section of the hollow as excavated for one of the single lengths, at one interval of time, before the brick-work is built ; the length thus excavated at once must depend upon the nature of the ground, and may be from three to eight feet, being careful not to endanger the falling in of the ground by taking too great length at a time. The horizontal bars, to support the superincumbent earth during the excavation and building of the brick-work, are exhibited at F, F, F, &c. The leading frames, TUNNELS AND DRAINS. 125 which direct the shape or figure of the section of the tunnel is exhibited at A, B, C, D, fig. 5. This is the main guide by which the bricklayers are enabled to conduct their work in the process of building : the plumb-line, which directs the position of the leading frames, is exhibited at GH; at I, is shown the courses of brick, in order to support the middle of the leading frames, and on which the line of direction for setting them is drawn ; the supports for the two extremities of the leading frame are shown at J, J. These are to be taken away when the bottom is so far laid as to give sufficient stability for the leading frames. The bars F, F, &c., are fixed by in- serting one end a foot or more into the solid earth, and the other end is supported by the arch last turned, or may be supported by upright shores from the bottom. In fi^. 4, which shows the arch as complete, the radiating bricks are shown at a, b, c, &c. for the inverted arch; at d, e,f, &c. and g, h, i, &c., for the sides ; and at k, I, m, &c. and «, o,j), &c. for the arch at the top. The centre for describing the inverted arch is shown at L ; the centres for describing the side-arches n o, n o, are shown at m, m ; and lastly, that for describing the arch at the top is shown at p. It is obvious that this point must be in the intersection of the two right-lines, mn, mn, in order that the two curves may meet each other without making angles at the points «, n, which would not only destroy but weaken the figure of the tunnel. The beauty and regular gradation of the curve tends greatly to promote the strength and durability of the work. In the construction of tunnels, the whole of the mortar employed should be made of the best water-cement, otherwise it will very soon be brought to a state of decay, and would require to be often repaired; and therefore eventually would become very expensive, a disagreeable cir- cumstance which may be avoided by anticipating it in the outset, and thus providing against it in the execution. Tunnel under the Thames, from Rotherhithe to Wapjring. S97. This bold design, to effect a communication of the opposite shores of this very deep and navigable river, was undertaken by Mr. Brunei, an engineer of eminence, who, undismayed by the failure of some attempts which had been made to accomplish the same end, completed a design for the execution of a tunnel beneath the river Thames. This enterprising design, from the rational hope of remuneration, did not continue long without patronage. A bill to incorporate a company for the execution of the proposition under Mr. Brunei's superintendance received the royal assent, on the 24th June, 1824. Tlie examination of the bed of the river, the selection of the most eligible position, the purchase of property, the preparation of the novel machinery, &c. &c. occupied the rest of the year. The soundings taken along the proposed line across the river, gave 12 feet water at the lowest tides, and 36 at the highest, in the deepest parts. The bed was found to be a stratum of sand, about 3 feet 8 inches thick, laying upon a stratum composed of sand and clay ; thence the top of the excavation was a bed of tenacious clay. The descending order of the strata at the 2k 126 PRACTICAI> BRICKLAYING. lower part of this bed in which the tunnel is executed was as follows : — A bed of stiff blue clay, about 2 feet in thickness ; a bed of silt, 7 feet ; silt mixed with shells, 7 feet ; indurated clay, 3 feei ; silt and gravel-stones, 3 feet. The tunnel was begun early in the year 1825; and the design consists of a square mass of brick-work, 37 feet by 22, comprising the arched passages, each of the width of 16 feet 4 inches. Each carriage-road is 13 feet G inches wide, and the height of each aperture above the road-way 15 feet 6 inches. The extreme sides are 3 feet in thickness, and the arches 2 feet 3 inches. The arched passages are divided by a wall of great strength ; and this division-wall is perforated by a range of arcades, of which a certain number of them, placed at regular intervals, are so wide that vehicles may pass from one carriage-way to the other. The central wall was built solid for the greater security of the work, and afterwards perforated. Under each passage is turned an inverted arch, 2 feet 3 inches in thickness ; the external wall rests upon one extremity of this arch, and half of the middle wall upon the other. Over the invert rests the Macadamized roads, terminating with commodious foot-paths on the sides: all the joints between the bricks are laid with cement. The foundations were all laid upon very strong beech-planks, which seem to have answered the purpose extremely well, since there has been no instance of any sinking or settlement of any kind. It was intended that the foot-passengers should enter the tunnel from either side of the river, by means of a winding-stair placed in a circular shaft. The distance of the two shafts for the passengers was intended to be 1300 feet, the width of the river being 1000 feet, from wharf to wharf; and that the descents for the carriages should be circular. Before the tunnel could be begun, it was necessary to get down to the depth at which the level of the bottom of the en- trance was to commence. For this purpose a cylindrical wall, 40 feet in height, 3 feet in thick- ness, and 50 feet in diameter, was constructed, so that, when sunk, to become the lining of the shaft. This circular wall rested upon a wooden curb shod with cast-iron base, of which the lower edges was formed into an acute angle in the manner of a chisel, and the top was secured by another wooden cuib, which was joined to the bottom one by means of iron rods. The brick-work was built with the utmost care on the surface of the ground immediately over the place which was intended for the shaft. In the upper part of the shaft, a steam-engine of 36-horse power was constructed, with a boiler, fire-place, &c., for the purpose of freeing the bottom of water, and lifting the exca- vated soil. The first brick of the tower was laid on the 2d of March, 1825, by Wm. Smith, Esq., M. P. for Norwich, and on the 1st of April following, the excavation commenced within its enclosure. As they proceeded, this immense structure, with its engine, &c., continued to descend vertically, without accident, for twenty days, through successive strata of gravel, &c., and when it had descended 37 feet from the surface, it rested upon a solid bed of clay. It was there permitted to remain ; but the excavation was continued, and the cylindric-wall under-built to the depth of TUNNELS AND DRAINS. 127 24 feet. At this level the diameter was reduced to 25 feet, and another cylindric-wall inserted, sunK 20 feet more. This lower part was intended as a tank, or receptacle for the drainage-water, into which were carried the suction-pipes of the engine-pump, for the purpose of carrying it off. The total height of the brick-work of this shaft was therefore 40 -f- 24 + 20 = 84 feet, 64 of which are of 50 feet diameter, and 20 of 25 feet. It consumed about 260,000 bricks, and 1200 barrels of cement. The weight of this construction is about 900 tons. The cylindrical cavity is intended eventually as the stair-case for persons on foot. Near it, a little to the southward, will be built the cylindrical shaft of 160 feet diameter, by which carriages are to ascend and descend, so as not to exceed in any part a greater declivity than that of Waterloo-Place, Pali-Mall. Though the principle of sinking this shaft was familiar to every well-digger, and to every miner, yet, from its vast diameter and proportional dimensions, it is considered as the greatest work of the kind ever yet attempted, as it demanded a more than ordinary degree of skill and intrepidity on the part of the engineer, in order to secure the success of the work. At the bottom of this shaft a lateral excavation was made for commencing the tunnel ; and from thence the constant protection and support of the soil, and the great weight of water upon it, was effected by means of a strong iron frame, consisting of several moveable vertical parts, the whole of which was called by Mr. Brunei by the name of a shield, weighing 120 tons, being 37 feet in width, 22 in height, and 8 feet in depth, and containing thirty-six workmen. It consisted of twelve compartments, which were advanced alternately and independently of each other, having each three cells, of which the floors serve constantly as a scaffold for the miners and bricklayers. The front of the shield is placed against the face of the soil to be excavated ; and, by means of moveable boards placed upon it, the workman can, by taking away the board, remove any part of the earth behind at his discretion, and when done, he places the board against the new vertical surface now exposed, and the board by this means becomes in advance of the box, and is kept in its place by props, which have their supports by the face of the brick-work in the rear. When he has thus proceeded with all the boards, it will be evident that an excavation will have been made equal to the area of the front of the shield, and of a certain depth, and that the boards will all be in advance equal to this depth. The box, by means of screws, is forced forward to the boards, and the operation of excavation recommences, and so on, observing that at every time the excavation is made, the brick-work is immediately executed all round close to the shield, and thus the security of the work is preserved. The work proceeded for several months, at the rate of about two feet in twenty-four hours, displacing from 90 to about 100 tons of earth, which were lifted to the surface by the engine. In each foot in length of the tunnel 5,500 bricks were used. On the 2d of Rlarch it had ad- vanced 4T0 feet, w])ich is about one-third of the whole length. About 11,000 bricks, laid in cement, were used every day, and the labour of one hundred men was constantly kept up. 128 PRACTICAL BHICKLAYING. A main from the gas-works is laid along the floor, and conveys the gas to columns placed in the connecting arches as they are formed ; and from these branches both the road-ways are illumi- nated, which produce in the eyes of the spectator, at his entrance, a most extraordinary and beautiful gradation in the perspective succession. The total freedom from water is preserved by drains underneath, which empty themselves into the tank under the engine at the bottom of the shaft. ^98. Though Mr. Brunei has conducted this work with very great ability, by numerous expe- dients to facilitate the progress, and to anticipate the difficulties of this extraordinary undertaking, these qualities were destined to a very severe trial. On the 18th of May, 1827, at a distance of 544 feet from the commencement of the tunnel, in the cyhndric wall of the shaft, the water of the river found its way through a portion of loose earth, and entered the tunnel through tne shield, with a velocity and volume which filled the hollow and the shaft in fifteen minutes. This happened while the workmen were at their duties, but no lives were lost. In this eruption about 1,000 tons of loose soil and rubbish descended into the tunnel. This breach was exa- mined by means of a diving-bell, and repaired by depositing about 15,000 cubic yards of clay, in bags, so as to fill up the cavity complete. The water was then pumped out, and the brick- work surrounding each aperture was found very slightly injured. In the latter part of September the works recommenced ; but, after the length had been extended 52 feet farther, and the dan- gerous part passed, on the 12th of January, 1828, the water of the I'iver broke in and passed through the shield a second time ; the tunnel was filled in less than ten minutes, and the rush of water brought in with it a current of air that put out all the lights : six of the workmen, being unable to extricate themselves, were drowned, the rest escaped. The point at which this eruption happened occurred at the distance of GOO feet from the shaft. This unfortunate eruption has also been perfectly stopped ; and, though the tunnel descends 3 feet in 100, into the excavation, in one part, towards the middle of the river, had approached within 10 feet of the water above it. These events, though much as it must be deplored, as tending to check the progress of the work, yet prove in a manner highly satisfactory, that no event of this nature can offer any impediment which cannot be surmounted. The sympathy which these misfortunes have so justly excited, together with the increased admiration which the overcoming of such difficulties has prodijced, induces a hope that the progress in future will be a national concern, and that the subscribers will be relieved from farther outlay by the munificent hand of government. The whole cost of the tunnel was originally calculated by Mr. Brunei to be ^^160,000 ; but the work has been attended with so many contingencies, independently of the expense incurred by the last accident, the expenditure before was ^157,000., of which about ^38,000. has been laid out in the purchase of premises and machinery, and .^118,500. in the works. The directors state that about j€75,000. will be necessary to complete the tunnel to the north ,em))ankment. TUNNELS AND DRAINS. 129 Plate XXX. fig. 1, exhibits a transverse section of the river Thames, passing longitudinally along the tunnel, and through the substance between the bed of the river and the excavation, with the sections of the shafts for the descending and ascending of carriages and foot-passengers. The plan of the shafts and tunnel are exhibited in fig. 2. Fig. 3, exhibits an elevation of the shield in which three men are represented at work in one of the compartments ; and fig. 4 is an elevation of the side of the shield, and in the longitudinal direction of the tunnel. The whole weight of this shield was 1^0 tons. Fig. 5, a transverse section through the two apertures of the tunnel, and through the summit of one of the arches of the division-wall, showing the representations of a loaded carriage and foot-passengers to and fro. Plate XXXI. fig. 1, exhibits a view of a part of the cylindrical brick-wall, the other part being taken down, in order to show how the curbs which secure the extremities of the brick- work are connected to each other by means of rods made of iron and wood alternately, placed and fixed to the curbs by means of screws. This, as has been explained, was sunk by con- tinually taking away the earth from beneath, and rested at intervals, so that the axis of the cylinder might be perpendicular at each descent. During the time of making any one descent, when a certain portion of the ground was taken away from under the wall, this portion was supported in the middle by blocks and wedged tight to the under side of the curb ; after this was done, another portion of the soil was dug away, and the under side was again supported by %vedges in the same manner, and so on all round, till the excavation was completed ; and then, when the wedges were slackened, and the blocks removed, the mass descended through one step, and this operation was done in every step. Fig. 2, shows a portion of a section of the bed of the river containing a transverse section of the excavation of the tunnel, and elevation of the six compartments of the shield. This sec- tion shows also a profile of the cavity formed by the irruption of the water, the manner in which it was filled by the clay-bags, and how the tarpauling above the clay-bags was kept down, by means of cast-iron kentledge, and, above all, the covering of gravel for securing the whole. Fig. 3 exhibits a section, as in fig. 2, but without the cavity being filled with the clay-bags, in order to show the state of the bed of the river after the irruption more clearly than fig. 2. Various other Designs for the Sections of Tunnels, S~ ucrs. Culverts, and Drains. 299. Fig. 7, plate XXXII, the section of a Tunnel, in which the road-way is sufficiently broad as to admit of carriages to pass each other with ease and without danger. The breadth of the road-way is 2S feet, and that of each of the foot-paths 7 feet, the whole breadth being 42 feet. The entire height between the middle of the head-arch and that of the inverted arch is 21 feet, and the height between the summit of the pavement in the carriage-way and the 2l 130 PRACTICAL BRICKLAYING. summit oi me arcii is 18 feet. Fig. 8, is a design for another tunnel, containing carriage and foot-ways, the whole width at the widest part being 21' feet. Fig. 7, is adapted to those situations in which the surface of the ground is not at a rery great distance from the hollow of the tunnel ; and jig. 8, is adapted to a situation where the pressure by the weight above is very great. Fig. 2, is adapted to a culvert for passing a large body of water, as a mill-dam, or the like. Fig. 1 , section of the brick-work of a common or main sewer. Figures 3 and 5, are the sec tions of smaller sewers or drains. Fig. 4, exhibits the section of a small barrel-drain ; and Jig. 6, shows the section of one of the smallest drains in use. All these designs, excepting ^^. 8, may either be constructed of brick or stone, according as the one or the other is most easily procured. In all cases, the planes of the joints should be perpendicular to the visible surface of the tunnel, whether the material used be brick or stone ; by this means the work will not only be easier to execute, but at the same time it will require fewer materials and will be much stronger, and, consequently, much less expensive than when the joints are placed obliquely to the visible surface of the brick-work adjacent to the aptn-ture or void of the tunnel. Though a uniform figure for the form of the right section of a tunnel is both stronger and more elegant than one that is compounded of the arcs of circles ; yet, if the variation is not very sudden in any place, to execute the whole of an arch of variable curvature, in several or in many portions of circular arcs, having their radii varying gradually from each other, will be very convenient, as such an approximation will not be perceptible in the whole design. It must, however, be observed, that the arcs on each side of every point of junction must have their centres in the same straight line, and that this straight line must pass through the point of junc- tion ; that is to say, the three points, viz. the centres of the two arcs, and the point of junction of the arcs, must be all in the same straight line. If this circumstance is not attended to, the beauty and strength of the work will be greatly deteriorated, as the curvature of the section of the arch will be deficient in point of continuity, and this will produce a very unsightly effect on the eye in the general appearance of the work, by crippling it in sudden gradations. This unpleasant effect must therefore be carefully guarded against, so that nothing but beauty and harmony may result from the execution of the design; and this \\\\\ not only give satisfaction to the workman who executes, and to his employer, but also to the public, who are ultimately to judge of the general effect of the design. CONSTRUCTION OF OVENS, &C. 131 CHAPTER VII. ON THE CONSTRUCTION OF OVENS, BOILER FIRE-PLACES, AND OF THE SETTING OF COPPERS. 300. The section of the roof of the oven, on the old principle, for the use of bakers, was usually of an oval figure, being arched over at top in the figure of an ellipsoid ; the sides and bottom of brick, tiles, and lime, with a door in front ; and at the upper part, an inclosed closet, with an iron gratinif, for the tins to stand on, called the Proving Oven. To heat such ovens, fagots are introduced and burnt to ashes, which are then removed, and the bottom cleaned out. This operation requires some time, during which much of the heat escapes. A still further length of time is required for putting in the bread, and unless much more fuel is expended than is really necessary, in heating an oven upon this principle, it becomes chilled before the loaves are all set in, and they are, therefore, by this means, very much injured. To remedy this inconvenience, many ovens have latterly been built upon a pavement supported upon solid brick-work, with a door of iron, furnished with a damper to carry off the steam as it rises, and heated with fossil coal. On one side is a fire-place or furnace, with grating, ash- hole, and iron-door, similar to that for supporting a copper, with a partition to separate it from the oven, and open at one end. Over this is a middling-sized copper, or boiler, with a cock at the bottom, and on one side of it is placed the proving oven ; the whole being faced with brick and plaster. When this oven is required to be heated, the boiler is filled with water, and the fire being kindled, the flame spreads around the oven, in a circular direction, all over its concavity, and renders it as hot as if heated with wood, without causing dirt or ill smell, while the smoke escapes through an aperture, which may pass into the kitchen-chimney. When the coal is burnt to a cinder, there is no necessity for removing it, as it prevents the oven from cooling while the bread is setting in, and keeps up a regular heat till the door is closed. The advantages of an oven built upon this principle, are too obvious to requii'e comment. Plate XXXIII. exhibits, in detail, the improved plan of an oven, on the new construction. It has been communicated by Mr. Elsam, the Architect, inider whose directions it has been constructed in various public buildings in different parts of the United Kingdom. Figure 1 is the plan of the oven. The fire is put into the furnace, A, and is supported upon wrought-iron bars, which are fixed an inch and a half below the level of the oven, to prevent the cinders from entering it. The outside of the furnace is shut with two cast-iron doors CI, 2, m plan). The ashes fall into the ash-pit beneath, B, (Jig. 2,) the door of which is marked 3, in the elevation (Jig. 3). 132 PRACTICAL BRICKLAYING. While tlie coals are burning, the mouth of the oven is inclosed only by the curved cast-iron door, or blower, B, shown in the section of the oven, {fig. 4,) and elevation, {fig- 10,) and which is so shaped in order to make a proper passage for the smoke to the flue, C. This door, or blowei', is not hung, but is put up and taken away by hand, as may be required. When the oven is sufficiently hot, a man, placed at its mouth, with the iron bar, E, {jig. 5,) slides the cast-iron stopper, D, {fig- 1 and 6,) to the angle, F, where it stops, as shown by the dotted lines ; then going to the mouth of the furnace, he hooks the crooked part, G, of the same iron bar, {Jig. 5,) mto the circular hole of the stopper, H, {fig. 7,) and pulls the fillet, I III I, {fig. 8,) into the frame of the furnace, upon which it fits. This stopper is made to slide, but not in a groove, as the cinders might sometimes prevent its being shut. Figure 8, represents an iron frame, to be fixed round the mouth of tlie inside of the furnace. The opening of the mouth should be one foot two inches wide, and one foot high, and to be made to receive the fillets of the stopper. III. The door, K, {fig. 4,) is fastened to an iron chain, and is raised or let down, at pleasure, by turning the lever, L, {figures 4, 10.) In order to prevent the heat from escaping while the bread is putting in, the mouth of the oven must be made as small as possible. To the handle of the lever is hung an iron pin, with a chain, and over it is a semi-circular iron plate, fastened' to the wall, with five holes drilled in it to receive the pin, which, by this mean, will regulate the height of the door, K, at pleasure. When bread is baking, the curved door, B, not being then wanted, is taken away ; and the two doors of the oven, with the two doors of the furnace, are shut up. At the top of the furnace, M, {fig. 4,) is a small flue, about three inches square, commu- nicating with the flue of the oven. The use of this small flue is to leave a passage for tlie sulphur that may remain in the ashes, and might injure the bread while baking. The connnu- nication of this small flue of the oven is opened or shut by means of an iron slider, N, {fig. 10.) Over the furnace is a niche, {fig. 3,) with a boiler of hot water. It has been observed that, in ovens on this construction, whatever be the dimensions of the fire-place, it is always proper to set the bars eight or ten inches in from the door, by this means a supply of coals will be kept warming before they are pushed forward into the fire. The im- portance of this preparation is known to those who have attended to the effect of every fresh supply of coals to the boilers of steam-engines, as it instantly stops the boiling, unless this pre- caution is attended to. It also prevents, in a great measure, the cold air getting in between the door and frame of the fire-place, which frequently happens, from the difficulty of fitting iron doors to iron frames. Ovens, on the improved construction, will hold, according to their size, as follows : — Eight feet wide, and seven feet deep, eight bushels of bread. Nine feet wide, and seven and a half feet deep, ten bushels. Ten feet wide, and eight and a half feet deep, twelve bushels. BOILER FIRE-PLACES. 133 If required to hold less than eight bushels, or more than twelve, the proportions, of course, must vary accordingly. The oven represented in the plate is eight feet wide and seven deep ; and, therefore, as stated above, it is adapted for eight bushels of bread. The fire-hole, or furnace, exhibited in fi^. I, enters the oven in a diagonal direction with the farthest corner ; the sides of the oven are carried nearly straight, and turned as sharp as possible at the haunch and shoulder, this iorm being supposed better calculated to retain the heat than any other : the flue is immediately over the entrance, as shown in figures 1 and 4. Welsh lumps, or fire-bricks, are used for the fiir- nace. In works of this nature, it is usual to introduce a considerable quantity of old iron hoops, more especiallj' around and over the oven, in order to keep the work together. This pre- caution is advisable on all occasions where great heat is required. In building the oven, one end of the crown is turned with bricks, as shown in the section, jig. 4 ; and the centering, for building the brick-work upon, is formed by filling the void with sand, clay, or rubbish, which must be well trodden down, and formed to the shape or figure of the crown. When the upper work is finished, the sand, clay, or rubbish, which formed the centering, must be dug out by the mouth of the oven. Other particulars will be found in the explanation of the terms used by Bricklayers and Plasterers. Of Boiler Fire-Places. 301. Plate XXXIV. shows the method of constructing a series of kitchen fire-places, for heating boilers, stew-pans, and other culinary apparatus. Fig. 1 represents a section, and fig. 2, a plan of a double-boiler fire-place ; the vertical section is taken through the centre of the grate, as shewn by the dotted line, a, a. In this construction, one boiler is placed immediately over the grate, and the other is placed over the space seen at b ; the space b is made sufficiently capacious to admit a large portion of the heated current of air, the direction of which is shewn by darts, the flue being so con- structed, as to completely envelope the external surface of the two boilers. If the flues were made all the way along their course of equal capacity with the space contained around the grate, it is very clear that when the air became rarified by the combustion of the fuel, it would move in every part with an equal velocity, and the greatest portion of the heat would escape, without being imparted to the vessel and its contents intended to be heated. In order to prevent this, the area of the flue is contracted at c, by which means the heated air is detained much longer under the bottom of the boiler, and impinging upon the surface of the vessel, tends to heat it in the most advantageous manner, it being a well-known fact, that heat is best communicated by ascent ; therefore it will, at all times, be advantageous to detain the heated current as long as possible, while it is covered by the under surface of the boiler. These 2m 134; PRACTICAL BRICKLAYING. reasons, if duly attended to, will, in every case, suggest to the practical bricklayer the most advantageous situation to construct the check or diminished area of the passage for the heated current. In cases where very great economy is requisite, as in steam-engine boilers, &c., the advan- tage of the ascending property of heat is so well understood by engineers, that they make the sides of their boilers project so as to form the upper surface of the enveloping flue, by which means they not only avail themselves of the lateral heat of the current, but also of that most important one before stated, namely, the ascending property. The sides around the grate, shewn at d, d, d, d, d, should rise in a sloping direction, so as to accommodate the space to the rarified state of the air, after it has been heated by the com- bustion of the fuel ; and as these sides will have to sustain the greatest action of the heat, they being many times covered with the ignited fuel, it is absolutely requisite that they should be formed of the best fire-bricks, and set in Stourbridge clay, or fire-loam, mixed with ground- clinkers from smiths' forges, which, when heated, will form a semi-vitrified mass that will bind and unite the whole mass firmly together. In all cases, where it can be admitted, the approach to the narrowed passage of the current should be made to slope gradually upwards, which will assist to contract the current, like a funnel, at the same time that such an effect is greatly assisted by changing the direction of the heated medium. In the construction of every kind of fire-place, where it is intended that the heated air should be made to strike or impinge against any vessel, in order to raise the temperature of its contents, it will be of the greatest importance to have all the brick-work done in the most solid manner possible, as nothing can be more injurious than cracks or openings, which, by being connected with the flues, admit cold air into the heated current, and thereby destroy, in a great mea- sure, the effect intended. To the practical man who is aiming at eminence in his profession, we cannot too much enforce these observations, as they have been practically proved to be of the greatest importance. Before concluding these obsei"vations upon the construction of this class of fire-place, we wish most strenuously to impress upon our practical readers the mistaken and false economy of making fire-grates too small, a practice that most completely defeats the principal object in view, namely, that of saving fuel. A very little reflection will clearly show that where the space for fuel is too small, the want of room to spread the fuel will cause it to lay in such a compact and solid state, that the gaseous parts will be distilled and pass along the flue without being ignited, and by such means, instead of imparting heat by entering into combustion, a precisely contrary effect will be pro- duced. And if, on the other hand, very small portions of fuel are frequently supplied, the opening of the door of the fire-place so repeatedly will permit so much cold air to enter as to essentially diminish the heating of the vessel, and its contents, independently of the great loss of time that will be required to keep up a steady heat. BOILER FIRE-PLACES. 135 There is also another circumstance of great importance, which must be admitted into the consideration of this subject, namely, that where fire-places are made sufficiently large, fuel of a much coarser description can be used, and a very equable and economical heat may be pro- duced; for, in such cases, the cinders and ashes from the common fire-grates, when mixed with a due proportion of small coals, will be not only sufficient for creating a proper heat, but will not require half the attendance that pure coals with a pinched fire-place will do. We have been induced to impress these observations, from a perfect conviction of their prac- tical utility, having frequently observed the great loss that accrues, and serious inconvenience that is sustained by many families who have employed persons to set the ordinary kitchen- copper, which is too frequently executed upon such bad principles, that a great portion of the advantages and convenience of that very useful apparatus is lost to the public. The length of the bars, in most cases, should be about three-fourths of the diameter of the bottom of the boiler, and if they are loose bars, they will be much better than a frame cast with all the bars entire, the space between each bar should be about half an inch. And it should be remem- bered that the flues of these kind of fire-places are as likely as others to be clogged with soot, and therefore it will be very requisite to have loose bricks, or stoppers, placed in proper situa- tions, as shewn at c, Jig. 2, which will give great facility in cleansing such flues, and frequently prevent danger firom fire in buildings where they may be erected. It may be necessary to state, that the same precautions and directions ought to be observed in figures 3,. 4, and 5, as in figures 1 and 2. Figures 3 and 4 represent a section and plan of a hot-plate, which is most generally of cast-iron, resting about an inch on the brick-work all round, and a rim of wrought-iron should be fixed round the external brick-work, to protect it from being broken or otherwise damaged. The bridge of fire-brick ought to be built to within three-quarters of an inch of the plate, leaving that distance between the bridge and the under- part of the plate, for the smoke and heat to pass on the way to the chimney. The dotted lines, in fig. 3, shows the position of the flue and the chimney ; fig. 5 is the plan of the copper-boiler, with the bottom part contracted round the grate. The smoke rises at the opening in the back, passes round the bottom, and then enters the chimney. Fig. 6, is the representation of a charcoal-stove, which is composed of soHd brick-work, except it should so happen that a very large one should be wanted, then the wall may be built hollow and filled up with rubble. The grates are constructed of cast-iron, and placed four inches deep, with a vacuity under to the floor for the ashes to drop, and thence they may be drawn out through the cavity left in the front. Stoves of this description are used for stew-pans, chafing-dishes, &c. A rim of wrought-iron should also be fixed round the brick-work at the top, about 3f inches deep.. The grates are of diflerent sizes, according to the magnitude of the building. 186 PRACTICAL BRICKLAYING. On the Method of fixing a Copper-Boiler for Brewing, 302. Fig. 1, plate XXXV. is a section through the upper vertical line in the middle of the copper ; fig. 2, a horizontal section of the copper taken under the bottom, and may be considered as the plan of the brick-work immediately above the grate. This method offers the least obstruction for the flame to play on both sides of the grate, where it meets on the oppo- site side of the prop at A, and thence rises in a sloping direction towards the back, which is shown by another section, fig. 3; the part at A, being the partition, as shown on the plan, fig. 2. Above the partition. A, the whole of the smoke rushes into a chimney or tube, ascending up the back of the brick-work, and is discharged into the atmosphere at the top. This chimney is shown in the section, fig. 3, ■which is taken at right-angles to fig. 2, as exhibited by the plan, fig. 4, which is the plan of the section, fig. 3. Fig. 5, is a vertical section taken through the axis of the boiler, and through the discharging cock, B and C, shown on the plans. Figures 2 and 4 are two other props, besides the par- tition A, which is also used as a prop. The plan or horizontal section, fig. 2, is that of fig. 1, and the plan or horizontal section, fig. 4, is that of the vertical section, fig. 3 ; fig. 4, being the same as fig. 2, only differing in its position, which is fig. 2, turned at right-angles. Fig. 6, is an elevation of the front, showing the fire-place, and the manner of suspending the door by means of pullics, which is balanced by a weight depending from the remote pulley. The top of the brick-casing round the copper is entirely closed round the circumference, as shown on the three sections at cm, aa, &c. There is a similar ring of brick-work which encom- passes the circumference of the copper, and is also shown on these sections, at bh, bb, &c. This construction is that recommended by Mr. David Booth, a gentleman well known by his numerous publications, and his scientific acquirements on practical and useful subjects. We cannot conclude this department of instructions without again enforcing upon our scien- tific friends the absolute necessity of making the atmospheric air pass through the ignited fuel, and also to take especial care that their work may be made so close and sound as to prevent a circulation of that which is very properly called the pabulum of life and flame ; for one fact should never be lost sight of for an instant, namely, that whatever air is admitted, without being decomposed or used up by the fuel, must of course tend to impart its own temperature to the surrounding objects, and, consequently, rather retard than accelerate the object in view. We are well aware, that however well fire-places of this kind may be constructed, much evil is fre- quently produced by having to join the flue, or carry it into one already formed. In such case, it will generally be well to continue the flue belonging to the boiler fire-place to as great an extent as possible, before it enters the flue already formed, which will assist, in some degree, to obviate a portion of the difficulty ; and where only one of the fire-places is used at the same time, that portion of the flue that leads from the one not in use, should be stopped, to prevent the entrance of air through it at such part. SETTING RETORTS. 137 CHAPTER VIII. SETTING RETORTS, AS PARTICULARLY APPLICABLE TO GAS-WORKS. 303. As Gas, for the purpose of aiFording light, has now become an article of general utility, it may be necessary to give some account of the brick-work, particularly of that very essential part of it, which applies to the setting of the retorts.- Notwithstanding the numerous experiments made, at the principal gas-stations, as to the best shape, and the most economical method of setting retorts, for the purpose of carbonizing coal, yet very little improvement, generally speaking, has been made, in either of these most important points, since the first introduction of gas-Hght. Retorts made of cast-iron ; lumps or tiles, made of fire-clay, have been tried ; and ovens built entirely of fire-bricks, have also been used, with greater or less success. Of these mate- rials, we may merely notice generally, that metal, being an absorbent of heat, and clay a non- absorbent, it hence follows, reasoning a priori, that the former would appear to be decidedly the preferable material for retorts. The practice at the principal gas-works sanctions this opinion. Indeed, metal retorts are now almost universally used. Retorts have been tried of various shapes : cylindrical, oval, semi-circular (or D shaped), parallelopipedal, &c. The form now most generally adopted is cylindrical, 7 feet 6 inches long, and 12 inches internal diameter. But whether that shape be the most profitable to the gas-manufacturer, can only be ascertained by actual experience; the results of experiments being so various, as regards gas matters, in different hands, no certain conclusion can with safety be drawn from them. The only sure criterion therefore to judge by is from making a fair trial. The modes of setting retorts are as multifarious as their shapes. They were first set on what is termed the flue-plan : sometimes one, two, three, and four retorts were set to one fire, which was placed either in front or at the back of the retorts, as room permitted, or as the fancy of the engineer directed. Sometimes two fires were used to heat a bench of three or four retorts. These flues were carried over and under the retorts repeatedly ; and were cer- tainly well calculated to produce an equal distribution of heat throughout the retorts. Mr. Peckston states, that two retorts, set on the flue-plan, to one fire, carbonized at 20 per cent, for fuel only. He does not, however, state directly the quantity of gas produced by this plan, from a chaldron of coals ; but, from the results given by him, of the produce of different kinds of retorts, in a Table, p. 141 of his book on Gas Lighting, we conclude it to have been 10,000 cubic feet, per chaldron, of Bewick and Craster's Walls-end coals. 138 PRACTICAL BRICKLAYING. Retorts, for the destructive distillation of coal, were next set on what is designated the oven-plan. This was the design of Mr. A. Rackhouse. His first experiment was made at one of the gas-works in London, by heating one retort in an oven. It was reported to heat very uniformly, and at little expence. He next set two in one oven, then three, afterwards five, and, lastly, seven. It is proper to observe, that cylindrical metal retorts, set in benches of five retorts each, on the oven-plan, to one fire, is still, by far, the most general mode adopted at the best conducted gas-light establishments. Mr. Stone, engineer to the Ratcliffe Gas Company, took out a patent some years ago for heating retorts by means of a coke-oven. This is still used at Ratcliffe works ; and answers the purpose admirably. There it has th§ peculiar advantage of being managed under his own immediate inspection. It has failed in other liands, but from what cause is not at present very clearly understood. At Ratclifie it has proved successful; and, having examined it carefully, we are far from experiencing any degree of surprise that it should be so. The coke made by this oven is excellently adapted for the blast-furnaces of founderies ; and sells for from 30*. to 32s. per chaldron. One oven heats seven square or parallelopipedal retorts, 6 feet 6 inches long, (they purpose making them a foot longer, which will be a decided improvement,) by two feet broad, and one foot deep, internal diameter. The oven is charged every thirty hours ; and the retorts every four hours. The grand object in view, in setting retorts, and in choosing the best configuration of them, is to be enabled thereby to make the greatest quantity of the best carburetted hydrogen-gas, at the smallest expence, and in the shortest space of time. In order to be able to accomplish this, there are four cardinal points which demand parti- cular attention: 1st, To use as little fuel as possible, in bringing the retorts to a proper deoree of heat, and in keeping it up ; 2d, To distribute and equalize that heat throughout the whole body of the retorts ; 3dly, To protect the retorts from the immediate action of the fire, without prejudice to the economizing of fuel; and 4thly, To dispose of the coal, within the retorts, so as to produce an abundance of good coke and carburetted hydrogen gas, of a suffi- cient specific gravity and illuminating power. It may, perhaps, be sufficient for all practical purposes, to give, in the first place, a descrip- tion of the mode, as presently practised at the principal gas-works, of setting cylindrical metal retorts, in benches of five retorts, to one fire, on the oven-plan ; next a description of Mr. Stone's coke-oven, which is capable of heating seven parallelopipedal retorts, as now in action at the Ratcliffe gas-works ; and, lastly, an improved method of setting fire retorts, in one oven, to one fire. By attending to these several modes, any number of retorts may be set on the same principles. Before entermg on this, it may be proper, however, to explain why five retorts in a bench are preferred to seven. The fact is, the heat is much more easily distributed amongst five than seven retorts. It is no saving of fuel to use seven retorts in an oven, heated by one fire. The con- SETTING RETORTS. 139 nection-pipes of the two undermost retorts, namely, those placed at each side of the furnace, are, from their shape, easily choked up ; and, while one side of these lateral retorts is exposed to an intense heat, the other side is comparatively cool : the consequence is, that the side thus exposed gives way, in a very short space of time, rendering these retorts totally useless, while the same extent of fuel must necessarily be continued to the remaining five, which was necessary to heat the seven, instead of that limited quantity of fuel, for which the furnaces to benches of five retorts are adapted. Indeed, there are some intelligent practical men, who, from motives of pure economy, and in order to distribute the heat equally, recommend, in benches of even three retorts, to use two small well-reg\ilated furnaces under them. Bench of Five Retorts. 304. Figure I, plate XXXVI, is a front view of a Bench of five cylindrical metal Retorts, A, A, A, A, A, set on the oven-plan, in a finished state. One of the undermost row of retorts is shown with its lid on, and secured by means of an iron strap and scTe\r,fig. 5. The eyes of the lid in fig. 4, fit on the straps, S, Jig. 6, and the lid is then tightened by means of the screw, Jig. 5. (Figures 4, 5, 6, are drawn a larger size to show this operation more distinctly.) The centre retort has its lid on merely, but not secured, as above described. The others are shown without their lids. For larger works, the beds of the retort-benches are generally supported by an arch of brick-work, marked ^, Jig. 1. It is a sunk floor, 7 feet deep, with a passage to it, for a wheel- barrow, by an inclined plane. In front of the whole row of retort-benches is a floor of iron-plates, supported by iron bearers, as shown at Jig. 3. In this floor there are hatchways, or trap-doors, as at C, C, C, figures 1, 2, and 3, for the purpose of allowing the red-hot coke, when drawn from the retorts, to fall into the sunk-floor. The iron floor, or stage, as it is sometimes called, is made broad enough to admit of scrapers, and other tools, necessary to be used by the stokers, the whole length of the retorts, a, (Jig. 1,) is the door of the fire-place; b, of the ash-pit. The ash-pit doors are furnished with perpendicular slits of about two-thirds their length, and five or six-eighths of an inch broad, for allowing a current of air to pass to the fires. The dimensions of these slits can be decreased by another piece, made with corresponding openin Slaters' work, for galleries, varies, according to the mouldings, from 4s. 6f/. to 5i. 6(/. per foot superficial; skirtings and facings from \s.M. to 2*. per foot. Chimney-pieces, &c. are sold at so much per piece. 391.— EXPLANATION OF THE TERMS USED IN SLATING. Back of a Slate. — The upper side of it. Backer. — A narrow slate put on the back of a broad square-headed slate when the slates begin to get narrow. Bed of a Slate. — The lower side of it. Bond or Lap of a Slate. — The distance between the nail of the under slate, and the lower end of the upper slate. Eave. — The skirt or lower part of the slating hanging over the naked of the wall. Holing. — The piercing of slates for the admission of nails. Margin of a Course. — Those parts of the backs of the slates exposed to the weather. Nails. — Pointed iron, or copper, or zinc, of a pyramidal form, for fastening the slates to the laths or boarding. They are commonly of the description or shape of clout-nails. Patent Slates. — Those which are used without boarding, and screwed to the rafters, with slips of slates, bedded in putty, to cover the joints. Scantle. — A gauge by which slates are regulated to their proper length. Sorting. — Regulating slates to their proper length by means of the scantle. Squaring. — Cutting or paring the sides and bottom of the slates. Tail. — The bottom or lower end of the slate. Trimming. — Cutting or paring the side and bottom edges of a slate, the head of the slate never being cut. PLUMBlNti. - 21U BOOK V. PLUMBING, PAINTING, AND GLAZING. CHAPTER I. PLUMBERY OR TLUMBING. 392. Plumbery comprehends tlic practice of casting and laying sheets of lead, also making and forming pumps, cisterns, reservoirs, water-closets, &c. The ductility of lead enables the plumber to effect his operations by means of tools, few in number, and simple in construction. 393. Lead, the metal in which the plumber chiefly works, is distinguished for durability and malleability. It is a white metal of a considerable blue tinge, very soft and flexible, not very tenacious, and consequently incapable of being drawn into very fine wire, though it is easily extended into thin plates under the hammer. Its specific gravity is 11'35. ; it melts at G12°, in a strong heat it boils and emits noxious fumes. Lead is brittle at the time of congelation. In this state it may be broken into fragments with a hammer. Lead is not much altered by exposure to air or water, though the brightness of its surface, when cut or scraped, very soon goes off. It is probable, that a thin stratum of oxyde is formed on the surface which defends the rest of the metal from corrosion. Every kind of metal becomes more difficult of corrosion or oxydation when its specific gra- vity is increased by condensation, this may be effected either by the hammer or passing it through rollers. Sheet-lead is used in two distinct states by plumbers, the first is that in which it is cast, and in this state it is applied as a covering to the flat-roofs, gutters, and other parts of buildings, also for lining cisterns or reservoirs where water is kept. In architecture, it is tech- nically divided into 5, 5\, 6, 6§, 7, 1\, 8, 87 lbs. cast-lead, by which it is understood that every foot superficial of such cast-sheet lead is to contain one or other of these weights. 394. Large sheets of lead are cast in the following manner : — The lead destined for this use is melted in a large cauldron or furnace, formed mostly of free-stone. At the bottom, a place is sunk lower than the rest in which is placed an iron pot or pan to receive what may remain of the metal after the sheet is run. The furnace is so raised above the area of the floor, as that 220 PLUMBING. tlie iron pot just rests upon it. In using tlie furnace, they heat it with wood, whicli is placed within it and ignited, and then the lead is thrown in at random with the burning fuel to melt. Near the furnace is the table or mould on which the lead is to be cast. This is formed of large pieces of wood well jointed, and bound with bars of iron at the ends. Around it runs a frame or ledge of wood three inches thick, and about two inches high from the table, technically culled the sharps. The ordinary width of the tables is from three to four feet, and their length from eighteen to twenty feet. This table is covered with a stratum of fine sand slightly moistened with water, taking care to use no more than will just make it bind together when closely pressed. The sand in this state is closely compressed by beating it with a mallet, the surface being reduced to a plane by a straight edge of brass or wood. Over the table is a strike or rake of wood which bears and plays on the edges of the frame, by means of a notch cut in either end of it, and is so placed as that, between it and the sand, is a space proportionable to the intended tliickness of the sheet of metal to be cast. Tliis strike is used to drive the metal, while yet liquid, to the extremity of the mould. At the top of the table is a triangular peel or shovel, bearing before on the edge of the table itself, and behind on a kind of tressel, somewhat lower than the table ; its use is in conveying the metal into the mould, and the design of its oblique disposition is, that it may by that means be able to retain the metal, and keep it from running off at the fore-side, where it has no ledge, some of these peels are large enough to hold fifteen hundred weight. ^^^len the apparatus is thus disposed, with a large iron ladle they take the melted lead, coals, and all out of the furnace, and with this, mixed as it is, they fill the iron peel. When full, they take out the coals, and clean the lead with another iron spoon, pierced after the manner of a scummer ; they then hoist up the lower part of the peel by its handle, upon which the liquid matter running off, and spreading itself upon the mould, the plumber conducts and drives it to the extremity of the table by means of the strike, which he passes along the ledges, and thus renders the sheet of an equal thickness. The sheets thus cast, there remains nothing to do, but to planish the edges on both sides, in order to render them smooth and straight. Where it is desirable to increase the durability of lead, as in the cases of being very much exposed to sun or wet, it is now usually rolled between the rollers of a flatting mill. The lami- nation increases the specific gravity of the metal, and makes it resist oxydation much longer. This process is performed most commonly at the furnaces where the ore is reduced, the rollers being of immense dimensions, and requiring great power to drive them. 395. Lead Pipes are universally employed for small watex'-pipes, chiefly from the facility of bending them in any direction, and also the capability of soldering their joints. Although some kinds of water corrode the metal by degrees, this will not produce so much harm as iron under the same circumstances, but would be a most dangerous poison if it was used in sufficient quantities to have any effect at all. PLUMBING. 221 Tlie method now very generally adopted in the manufacture of leaden pipes, is to cast the lead in an iron mould, upon a cylindrical iron rod of the size for the bore of the intended pipe, the lead being three or four times the thickness of the intended pipe ; and in short lengths, which are then drawn through holes in pieces of steel, in the manner of wire drawing, till the pipe is reduced to the intended thickness, and drawn out to the proper length. Another method is to reduce the pipe by repeatedly passing it through the two rollers of a flatting mill, in each of which a number of semi-circular notches or grooves are formed all round, so that the two rollers when put together, have a number of circular cavities between them, which gradually diminish in diameter from one end of the rollers to the other. The pipe is first rolled between the largest of these cavities, then in a smaller one, and so on to the last, which extends the pipe to its proper length, and diminishes its substance to the proper thickness, at the same time, by condensing the metal, hardens it, and makes a very strong tube with very little metal. Mr. John Wilkinson, of Broseley, obtained a patent, in 1790, for the last named method, which he practised on a very extensive scale. Since the expiration of this patent, many manufactories of this article have been established, some employing rollers, and others the draw-bench for extending the pipes. 396. Solder is used for uniting the joints of leaden work, and it should more readily acquire a state of fusion than the metal intended to be soldered thereby, and be of the same colour. The solder generally made use of by the plumber, is called soft solder, and is made of tin and lead, in equal parts, fused together, and run into moulds like a common gridiron ; in this state it is purchased of the manufacturer by the plumber at so much per pound, according to the price of the market. 397. Laying of Sheet Lead. The ground for sheet lead, whether it be of plaster or boards, should be perfectly even, otherwise the work will be bad, unsightly, and liable to crack. The sheets not being more than six feet in width, make it necessary that they should sometimes be joined ; this is performed either by seams or rolls. The seams are formed by bending the two edges of the lead up, and over each other, and then dressing them down close. The rolls are formed by fastening a piece of wood about two inches square under the joints of the lead, and dressing one of the edges of the lead over the roll on the inside, and the other edge over both of them on the outside, and then fastening them down by hammering. Soldering is sometimes used for joining two sheets; but this mode should be rejected on account of its liability to crack when exposed to alternate expansion and contraction, occasioned by heat and cold. All sheet lead should be laid with a current to keep it as dry as possible ; and for this purpose the boarding or ground upon which it is laid, should have a fall of about one quarter of an inch to every foot upon which the lead is laid. 398. Drips on Flats or Gutters are formed also in the preceding manner, and by dressing the joints of the lead as described for rolls. This is used to avoid solder, and keep the work dry. 399. Flashings are pieces of milled lead about eight or nine inches vide, and are fixed round 22'2 PLUMBINCi. the extreme edf^e of a flat or gutter in which lead has been used. One edge is dressed over the lead of the flat or gutter, and the other fastened, either by passing it into the joints of brick work, or fixing it by means of wall-hooks. The pipes used by plumbers vary, in the diameter of their bores, from half an inch to two inches. Socket pipes are those which are used for conveying superfluous water from roofs, Sec, and are usually from three to five inches diameter. These are made of milled lead, in lengths of eight or ten feet, dressed on a cylindrical core of wood, and fastened at the vertical joinings with solder ; the horizontal joints are formed by an astragal moulding in a separate piece of lead, about three inches wide, which laps completely over it, both above and below the joint, and hence it is called a lap-joint. Two broad pieces of lead, called tachs, are attached to tlie back lap joints, and spread out right and left for fastening the pipes to a wall by means of wall hooks. The cistern head, which is fixed to the upper end of rain-water pipes, is either made of sheet lead, or cast in a mould, and fastened by tacks as above described. 400. Pumps. Those supplied to the public by plumbers are usually made by engineers, who have suitable apparatus for boring the barrels, they being made of brass, or metal very similar in its nature. They may be divided into three distinct kinds, namely. Sucking, Lifting, and Forcing Pumps. Forcing pumps are now but little used ; the lifting and sucking pumps being proved by experience to be the best for most domestic purposes. The sucking pump consists of two pipes, the barrel and suction pipe, the latter being smaller in diameter. These are joined by flanches, having leather placed between them to make the joints water-tight. The flanches are united by screw-bolts in the usual manner. The lower end of the suction pipe is spread out, or made funnel- shaped to facilitate the entry of the water, and it frequently has a grating to keep out filth and o-ravel. The working barrel is cylindrical, and as evenly bored as practicable, to give the piston the least possible friction. The Pixion is generally made of wood in the form of a truncated cone, the small end being cut off at the sides so as to form a kind of an arch, by which it is fastened to the iron rod or spindle ; the two ends of the conical part may be hooped with brass, and the larger end of the cone uniformly surrounded with leather to some distance below its base. This leather band should be sufliciently large to render the piston uir tight, without causing unnecessary friction. The Lifting Pump consists, as in the former, of a working barrel, which is closed at both ends. The piston is usually solid, and its rod passes through a collar of leather, or a stuffing box, in the plate, which closes the upper end of the working barrel. The barrel communicates laterally with the suction pipe, and above with the rising main. This pump differs from the pre- ceding only in having two valves, the lower one moveable, and the upper one fixed. In Plate XXXIX. fig. 2, represents an elevation, and figure 3, a vertical section, of a very perfect lifting pump, as now made by Messrs. Bramahs, the celebrated engineers, at Pimlico ; the construction of the various parts as explained by the section, will show the extent of water-%^..y that has been here obtained by the excellent construction and disposition of the valves, and also PLUMBING. 223 the superior means applied in tlie upper part for keeping the piston rod lubricated with oil. Tlie excellent proportions of all the parts, and the judicious combination of the whole, induced us to give the two figures before-named for the benefit of our practical readers, who will here have an opportunity of examining the internal construction engraved from a working drawing, very kindly furnished us by Messrs. Bramah and Sons, for this work. The Forcing Pump consists of a working barrel, a suction pipe, and serving main, or raising pipe. The last is usually in three parts ; the first consisting of one piece, and making part of the working barrel ; the second is joined to it by flanches, forming an elbow with it; and the third is the beginning of tlie main, and is continued to where the water is delivered, where it is furnished with two moveable valves. The perfection of the barrel and piston of this pump is so great as to require neither wadding nor leather ; it is only used where it is found requisite to force water to a considerable height. There are a considerable variety of pumps besides those above described, but none of them are so applicable to domestic purposes or general use, as those we have enumerated. The materials of these pumps are manufactured to almost every required purpose, and thus sold to the plumber, who only puts them together so as to make them produce their desired effects. The different parts of water-closets are made in a similar way, and sold to the plumber, who places the basin, apparatus, traps, socket pipe, cistern, and forcing or lifting pump together, so as to put them in action. Sheet lead is charged by the hundred weight, according to prices arranged at intervals by the Warden and Court of Assistants of the Plumbers' Company. Milled lead is usually charged two shillings per hundred weight more than cast lead. The best method of preserving lead when exposed to the action of the atmosphere and water, is to place iron in close contact with it ; the galvanic effect produced causes the iron to be oxydized, the lead being preserved almost entire while there is iron in contact with it. 401. The tools of the plumber are few in number, and simple in construction. The following enumeration will be deemed sufficient : — Centre Bits, of various sizes. Chalk Line, used in the same manner as a carpenter's. Compasses, are used for striking out circular portions of lead. Cutting Knives, of various sizes ; these are used for dividing sheet lead at the mark left by the chalk line. Dressing and Flatting Tool.— This is made of beech, about eighteen inches long, and two and a half square ; planed smooth on one side, and rounded into an arch on the other. It is used for stretching out and flattening the sheet lead, or dressing it into any required shape. Files, of various sizes. Glasing or Heating Irons, of various sizes ; about twelve inches long, and tapering at both 224 HOUSE PAINTING. ends, the handle end being turned quite round, that it may be held firmly in the hand. The opposite end is spindle shaped. These are used red hot in soldering. Hammer, made of iron, which is rather heavier than those in general use. Ladles, made of iron ; these are of various sizes, and are used for melting solder in. Mallets, similar to the carpenter's, of various sizes. Jack and Trying Plane for finishing the edges of sheet lead. CHAPTER ir. HOUSE PAINTING. 402. House Painting is that economical application of artificial colours, compounded either with oils or water, which is employed in preserving or embellishing houses, ships, furniture, &c. The term economical painting may with propriety be applied to the property which oil and var- nishes possess of preventing the injurious effects of the atmosphere upon wood, iron, and stucco, by interposing an artificial surface or covering composed of materials, which, by the peculiar che- mical changes effected in them, are rendered capable of resisting the decomposing and destroying qualities of the atmosphere, and thereby of preserving various substances from premature decay. It is here intended to use the term more generally, in allusion to the decorative part, as applied to buildings, as well as to its more essential ones, and as it is employed by the architect through- out every part of his work, both externally and internally. The chemical properties of the materials, and the mode of applying them is the same, either in churches, theatres, or any other public or private buildings, or with such slight variations, as will be readily suggested by a judicious workman. We shall now describe the principal pigment used as a base in all house painting, and also the vehicles most commonly used to mix and dilute the colours with. 403. White Lead is the principal ingredient used in house painting, forming the basis of most of the neutral colours. It is obtained by rolling thin sheets of lead into coils, leaving their surfaces about half an inch apart from each other, and then placing them vertically in earthen pots, with a portion of good vinegar at the bottom, in such a way, that when set in a moderate heat, the vapor of the acid oxydates the lead, producing a carbonate of lead, which may be taken off" in white flakes when the sheets of metal are uncoiled. These flakes are then ground in linseed oil, in which state it is sold in the market by the name of white lead. The materials so combined are much better for being kept, and where the best and purest whites are required to be pro- duced, it should be kept in the levigated state for at least two years. The Nottingham white HOUSE PAINTING. 225 lead is most esteemed for whites, without gloss, commonly or technically called flatting or dead white. 404. Linseed Oil is expressed from the seed of flax, by those who manufacture it, in large quantities. It is the principal oil used in house painting. The worst defect of this otI is its natural brown colour, and a tardiness in drying. The goodness of linseed oil, therefore, consists in its near approach to a colourless state, and in its drying soon. It may, however, be used in its simple state, by simply mixing with it some substance which will increase its drying proper- ties. But keeping it for some considerable time, will be found to improve its quahties both for colour and also drying. These effects will be greatly promoted by exposing it to the action of the atmosphere and light, both of which tend to bleach and improve it. This oil may be ren- dered much more capable of drying, by boiling it with certain substances, such as red lead, white vitriol, sugar of lead, umber, and many other substances ; but all of these have a tendency to increase its natural colour, and if carried to a considerable extent, render it very nearly black, owing, in a great degree, to particles of the oil being completely carbonized. 405. Boiled Oil may be prepared by adding to each gallon of linseed oil one pound of litharge, one pound of white vitriol, half a pound of sugar of lead, and a quarter of a pound of umber ; boil them so long as the discolouring the oil will permit, for the oil must not be boiled so long as to produce blackness. When the oil is taken off the fire, it may while hot be strained through flannel, after any indissoluble portion of the ingredients have settled. 406. Oil of Turpentine is an essential oil, distilled fiom crude turpentine, and is techni- cally called by the painters Turps ; it quickly exhales or evaporates in the air, and if mixed with Hnseed, nut, or poppy oils, in flying off, carries with it the more volatile parts of such oils, and causes them to dry much sooner than they otherwise would do. On this account it is very gene- rally used as a dryer to mix with the other oils, for which "purpose it has greatly the advantage over drying oil with regard to colour, as it is perfectly transparent and pellucid. It is used without any other preparation than mixing it, either alone or together with drying oil, along with the other oils and colours ; and it is not subject to any adulteration, except the dissolving crude turpentine or resin in it, which do not greatly injure it for the purposes we are describing. It should, however, be observed, that for all the purposes of painting it will be the better for age ; its valuable quality for drying being greatly increased by that circumstance. 407. Litharge is an oxyde of lead, prepared in the process of refining gold and silver. It is used in making drying oil, in the manner above described. 408. Sugar of Lead is a chemical preparation of lead, made by dissolving it in vinegar, and reducing the salt to a crystalline state. It has a quality of making oils dry w hen mixed with them, and on that account is very frequently used, as well in the manufacture of drying oil, as in the common use of the oils, where it is ground up with them, together with the colours. It is also kept ready ground with oil, and sold in a state ready to mix with colours at any time. 409. White Vitriol, or sulphate of zinc, is commonly used as a dryer. It is found as a 3 M 226 HOUSE PAINTING. mineral substance in various parts of Europe, and may be made artificially by a peculiar appli- cation of sulphuric acid to zinc. It is much used in making drying oils, and also when ground with oil, and mixed with colours, to render the oil drying. 410. Putty is a compound of whiting and linseed oil, but the best is that made with drying oil that has been very much boiled, by the use of which a composition may be formed, that will become sufficiently hard, but will yet be tough, without being so brittle as that which is made of common linseed oil without boiling. In all cases, the oil should be thoroughly mixed with the whiting, and the more it is worked together the better it will be ; and for this purpose, some manufacturers have used a kind of mill to facilitate the operation. 411. The first coatings or layers, if on wood or iron, ought always to be of white lead, the very best that can be obtained, great care being taken to procure that which is thoroughly ground ; but previous to laying the first coat upon fir or deal of any sort, it will be requisite to destroy the effects of the knots. These are, in general, so thoroughly saturated with pure turpentine, as to render it one of the most difficult parts of the house painter's art to conquer ; indeed it may be truly said, to remain at the present time a desideratum. The usual method is to dab them over with a mixture of white lead ground in water, having a portion of red lead mixed therewith, the liquid vehicle being parchment size ; when this is dry, they should be separately painted over with white lead ground in oil, to which some powerful drier has been added, as red lead or litharge, about one-fourth of either being the usual quantity. These preparations should be smoothly finished with the brush, in the direction of the grain of the wood. When the two coats are dry, the parts so treated should be rubbed over with pumice stone to make them equally smooth with the other parts, and then the first coat of paint should be laid on, the colour being rendered sufficiently liquid with linseed oil. The first coat being dry, all the nail-holes and other imperfections should be filled up or stopped with putty, the surface being left per- fectly smooth. The work may then receive a second coat of white lead and oil, somewhat diluted with the essential oil of turpentine, and this should be repeated twice at least, forming three coats in all, but in very fine works a fourth is sometimes added. Where it is intended the work when finished should not be of a perfect white, the last coat should have a small quantity of ivory or lamp black added, to reduce the whiteness in a slight degree, which will produce a very pleasing effect, and will be found very serviceable in preventing the change of colour which frequently takes place from the oil not being of sufficient age. The usual proportion of turpentine to oil is about one-fourth of the former to three of the latter, which will produce a glossy or shining surface ; but where the surface is required to be without gloss, as in all the better sorts of work, and which is technically called flatted, then the colour, whether it be pure white or any compound tint, must be made sufficiently thin with turpentine, and when used in that state, it will dry without any gloss upon the surface, and consequently reflect to the eye of the beholder one uniform flat tint. It may be requisite to obser\e here, that as the colour mixed with a large proportion of oil dries much slower than where HOUSE PAINTING. a large proportion of turpentine is used, little difficulty is experienced in laying it on large sur- faces perfectly even, the one part blending into the other very easily, but, in flatted work, con- siderable management is requisite, as well as considerable activity, on account of the rapid drying of the colour ; and for this purpose, where the sides of very lofty apartments are to be covered in that manner, it is frequently necessary to have two persons employed at the same time, upon nearly the same part. The best mode of proceeding is to begin at the top of the right hand side of the compartment to be flatted, taking care not to cover a larger stripe or portion than can be completely effected before the upper part becomes dry ; and if this be properly accom- plished, the joinings will not be visible ; but where the sides of a room are too lofty for one person to effect the object in time, then two must be employed to ensure success, it being almost impossible to produce a flat tint, where a new portion is joined upon a part already dry, or nearly so. It must also be observed, that two coats in oil, and then two in turpentine, are neces- sary for all new work that is to be well executed. Flatted work, owing to its want of gloss, is more likely to soil by being touched, than work executed in oil ; but its superior delicacy, and also the property it has of retaining its colour, renders it indispensable for all situations where delicacy and durability of colour are necessary. It should, however, be observed, that as a very small portion of oil is used, namely, that only that is necessary to grind the colour with, it is inapplicable to parts that are exposed to the weather, preservation being in that case the prin- cipal object. What has been here stated may suffice as to painting on wood, either on outside or inside works ; the former being seldom executed otherwise than in oil, three or four coats being generally quite sufficient. But as the painting of stuccoed walls (not previously painted) require considerable care, we shall now offer such observations and directions as, if attended to, will render that department easy and certain of attainment. 412. In order to succeed in painting stucco, not only the plastered surface should be tho- roughly dry, but the brick-work upon which it is laid should also be completely free from damp or moisture, which can only be the case where the walls have been erected a sufficient time to permit the mass to attain perfect dryness. Indeed, the greatest part of the mystery of painting stucco, so as to answer the intended purpose of standing and wearing well, consists in attending most scrupulously to these observations, for whoever has observed the expansive power of water, not only in congelation, but also in evaporation, must be well aware, that when it meets with any foreign body obstructing its escape, as oil-painting for instance, it immediately resists it, forming a number of vesicles or particles, containing an acrid lime-water, which forces off the layers of plaster, and frequently causes large defective patches, extremely difficult to be repaired. In those works where persons have an interest in the durability, two years is certainly not too \ona a time to thoroughly dry both the walls and plaster ; but in speculative works, even a few weeks are scarcely allowed, and hence the bad appearance of such works in such a very short period of time after they are executed. 228 HOUSE PAINTING. If these precautions be duly attended to, tlicrc can be no better mode adopted for priming or l.iviii<^ on the first coat on stucco, than by using boiled linseed oil, prepared as above-desciibed, takin" care to lay it on very evenly, so as to leave the surface very smooth, and not more than tlie stucco will absorb. It should then be covered with at least three coats of white lead and oil. takincf care to let two or three days intervene between each coat. If the stucco be intended to be finished of any given tint, as grey, light green, apricot, &c., it u ill then be proper about the third coat of painting, to prepare the ground for the desired tint by a slight advance towards it. Grey is made with white lead, Prussian blue, ivory black, and lake. Sage green, pea and sea "reens, with white, Prussian blue, and fine chrome yellow. Apricot and peach, with lake, white, Chinese vermilion and chrome yellow. Fawn colour, with burnt terra sienna or umber and white. Olive greens, with fine Prussian blue and Oxfordshire ochre. In some cases it may be absolutely necessary to inhabit buildings before the walls are suffi- ciently dry to receive a coating of oil paint ; the colouring in distemper must then be resorted to, which being a covering of water-colour fixed by size, may be washed oft' and completely removed at any time when the walls are considered to be perfectly dry and fit to receive the oil colour. 413. DisTEMPUK. In this kind of painting, the white colour or base most commonly used is the finest whitintT, which is prepared in large quantities by various manufacturers. The colours most commonly mixed with it for producing the various tints are as follows : — Straw colour, may be made with white and masticot or Dutch pink ; fine greys, with white and refiner's verditer ; an inferior grey may be compounded with blue black or bone black, and damp blue or indigo ; pea greens, with French green, Olympian green ; and fawn colour, with burnt terra sienna or burnt umber and white, and so of any intermediate tint. All the colours used in distemper, should either be ground very fine, or washed over so as to ensure the most minute division of their particles. In general, the size made of common glue is used with a proper quantity of water to render the colour liquid, but where the work will afford it, parchment size will be found greatly superior. It will not require less than two coats of any of the foregoing colours, in order to cover the plaster, and bear out with an uniform appearance. When old iilastering has become discoloured by stains, and it be desired to have it painted in distemper, it is then advisable to give the old plaster, when properly cleaned off and prepared, one coat at least of white lead ground in oil, and used with spirits of turpentine, which will generally cover all old stains, and when quite dry will take the water colours very kindly. The above process will also apply to old wainscotings, in cases where temporary painting is only required ; but of course such a method cannot be recommended for durability. In every kind of painting, but particularly in oil-painting, the greatest degree of cleanliness should be rigidly enforced. The brushes and all the utensils should be freed from the portions of paint that will dry upon them from time to time, by scraping and washing, which may be done GLAZING. 229 with a blunt knife and strong soap and water, for if this be not done, the colours will soon become very foul, and the work will in such cases be very inferior. 414. Graining. This is a kind of ornamental painting, lately used to a considerable extent in the decoration of houses. It consists of imitating, by means of painting, various kinds of rare woods, as satin-wood, mahogany, rose-wood, &c., and likewise various species of marble. For this kind of work the painter is furnished with several camels' hair pencils, and with one or more flat hogs' hair brushes. An even ground is first laid of a mixture of white lead, and the colour required, diluted with oil of turpentine. This is left for a day or two to get thoroughly dry. The painter then prepares his palette-board with small quantities of the colour required, and having some boiled oil and turpentine mixed together, tries the effect of the tint by spreading it over a panel, and if it suits, perseveres by doing a single panel at a time. The shades and graining is then produced by dipping the flat hogs' hair brushes in the mixture of oil and turpentine, and drawing it down the newly-laid colours. The other particular appearance required, is produced by means of the camels' hair pencil. When all is fixed and dry, the whole is covered with one or two coats of good oil varnish. This kind of painting is not much dearer than good work in the common way, but it will last ten times as long by being occasionally varnished, without losing any of its freshness. CHAPTER in. GLAZING. 415. On glass very little has been communicated in the works of the ancients. It, indeed, appears, from the ruins of several Grecian buildings, that they had apertures or windows ; and it would seem, from the nature of their construction, they were adapted to receive a frame filled with some transparent substance. In some of the apertures discovered at Pompeii and Hercula- neum, squares of amber were found ; yet, though many of the Roman authors mention glass, it was so rare as to be employed only in the mansions of the opulent. Bede is the first who mentions glass as applied to glazing windows. He likewise informs us that Abbot Benedict was the first who introduced the art of making glass into this kingdom, about the year 609 ; and, from the specimens that now remain, it is evident that not only the making of glass, but the art of staining it, made rapid strides towards perfection in a very short time after. Glazing, as now practised, embraces the cutting of glass, and fixing it into sashes of wood or casements of lead and likewise the ornamenting of windows with stained glass. 3 N 230 GLAZING. Plain coloured glass may frequently be used with a very pleasing effect, and is very little more expensive than good common glass. Coloui'ed glass is charged by the pound ; Claude Lorraine, green, red, &c., at about six or seven shillings, and blues somewhat more. Glazing in lead-work is of the most antient description ; sashes being of modern date. These sashes are formed with a groove or rebate, on the back of their cross and vertical bars, for the reception of the glass, which the glazier cuts to its proper size, and beds in the composition called putty. Putty is made of pounded whiting, beat up, with linseed oil, into a tough tenacious cement. When used for mahogany frames, a little red-ochre is mixed with it to suit the colour of the wood. The beauty of glazing depends principally on the colour of the glass. Glaziers now use chiefly ■what is called croivn glass, which is divided into three kinds, called firsts, seconds, and thirds, according to their qualities, on which its value depends. The glass is bought by the crate, which consists of twelve tables of the best, fifteen of the seconds, and eighteen of the thirds. These tables are each about three feet in diameter. A crate of the best glass is vfilued at about four guineas ; of the seconds, about three ; and the third.s, two guineas. The crown glass manufac- tured at Newcastle and its neighbourhood is esteemed the best : the prices of glass are various. Green-Glass is another sort, much used for common purposes, being not more than half the price of the crown-glass. From many old windows, it appears that this kind of glass was the most antient made use of. Waved Plate-Glass is very thick and strong, presenting an uneven surface, as if indented all over with wires, so as to leave the intermediate spaces in the form of lozenges ; it was for- merly nmch used in counting-houses, &c. to prevent the inconvenience of being overlooked ; but thou'^h it has lately been superseded by ground-glass, it is still to be obtained in London. Ground or Rough Glass is used for the same purpose as the above, and is no other than the common crown-glass, rendered opaque by having its polish taken off", and rubbing it witli sand and water or emery. Plate-Glass is the most beautiful glass made use of, being nearly colourless, and sufficiently thick to admit being polished in the highest degree. The tables of this glass will admit of pieces being taken out of them much lai'ger than can be obtained from any other kind of glass. The British Plate-Glass Company, in Albion-Place, London, is the most celebrated depot for this species. There it is sold by the inch, in proportion to its size, the value increasing accordingly. Though the expense of this glass, by far, exceeds that of any other, yet is now so much pre- ferred, as to be used in many shop-windows in the leading streets. ^ German Sheet is another species of glass much esteemed, and would be superior to the pre- ceding, had it not a disagreeable appearance, from being very wavy or uneven. Bohemian Plate-Glass is similar to the above, only possessing a red tint ; and though much used about thirty years ago, it is now quite rejected. GLAZING. 231 416. Glaziers value their work by feet, inches, and parts, according to the size of the panes, or squares, employed. The charges are regulated by the Master, Wardens, and Court-Assistants of the Company of Glaziers, and at present run thus : — s. d. Best crown, not exceeding 3 feet, per square 3 10 Ditto, ditto 2 ft. 6 in., ditto 3 4 Ditto, ditto 2 ft. ditto 3 2 Ditto, under 2 ft. ditto 3 Seconds of the same dimensions are about ten per cent, cheaper ; and Thirds, of similar dimensions, are 10 per cent, cheaper than the seconds. Green glass is the cheapest, never exceeding eighteen pence per foot. The price of all kinds of bent glass, for circular and other windows, varies accordin'^ to the size, the trouble of obtaining it, and fitting it in. Cottage and some kinds of church windows are glazed in squares, or other figures, in leaden rebates, which are cast and drawn for the purpose, and soldered together at the interstices. This leaden work is of various sizes, according to the strengtii required, and is used instead of the cross bars of sashes. The grooves left in it for the glass have their cheeks sufficiently soft to be pressed down all round to admit the glass, and again raised up, when the glass has been put in, to keep it firm. Sucli windows are strengthened by vertical and cross b.irs of iron, with. bands, which, having been soldered to the lead, are twisted round the iron. In cottage windows the bars, instead of being of iron, are often of wood. 417. Glaziers formerly cut their glass out with an instrument called & grozhig-iron ; but this pro- cess was not only tedious but difficult, and has therefore been entirely superseded by the introduc- tion of the diamond, which is as complete a tool for the purpose as can possibly be required. This instrument consists of a diamond spark, in its natural uwpolished state, fixed in lead, and fastened to a handle of some hard wood by means of a brass ferrule. The handle is about the size of a moderate drawing pencil. The diamond is the principal working tool of the glazier. His other tools are a rule and several small straight edges. The former is divided into thirty-six parts, or inches, and is used for dividing the tables of glass into any required size. The straight edges are merely thin pieces of some hard wood, about two inches wide, and one quarter of an inch thick, and are used for the diamond to work against. Glaziers are likewise furnished with stop- ping knives, which resemble dinner knives, with the blade reduced to about three inches in lenTtii, and ground away on each side of its edges to an apex. They are used for bedding the glass in the rebates, and for spreading and smoothing the putty. A Hacking-out Tool is an old broken knife, ground sharp on its edge, and used for removing old putty out of the rebates, which are to be filled with new squares of glass. The glazier s luimmer is similar to the smaller kinds used by otlier ariifirers. 232 GLAZING. Glaziers are also furnished with a pair of compasses, which has one of its legs formed with a socket to receive the handle of the diamond, for drawing and cutting out any peculiar shapes of glass for fan-lights, &c. Good glazing requires that the glass be cut full into the rebates ; for,'when too small or too large, it is liable to be broken by the least pressure within, or even the wind from without : more- over, the putty should never project beyond the line of wood in the inside, and large squares should be further secured by small sprigs being driven into the rebates of the sash, and covered over with another coat of putty. The business of a glazier includes the cleaning of windows, and this forms no inconsiderable portion of the trade in London; some masters keeping one or two men constantly employed therein. The charge is regulated b'y the number of windows cleaned, and the number of squares in each frame. Windows, exceeding twelve squares, are charged from 6d. to 8d. per dozen, the large squares of French sashes being raised about one-third more. The master-glazier takes upon himself the risk of windows being broken by his men, when employed in cleaning them. In many parts of the United Kingdom it is the custom to measure all the wood-work apper- taining to the sashes, for the quantities of glass contained in the respective squares ; also, the lead-work. And such is the prejudice in favour of the practice in some places, that if any intel- ligent person was to attempt to reason them out of it, he would be considered a most inequitable valuator, and unworthy of being countenanced. Time and concurring circumstances, it is pre- sumed, may, at some period or other, equalize our customs, weights, and measures ; but until that period arrives, the system of valuation must be dependent upon local customs. The net quan- tities of glass, should, in all cases, be measured, except in circular fan-lights and similar works, where the glass should be measured in the widest part ; and because the pieces cut off to make the glass fit the apertures can be considered only as waste glass, the price or allowance for whicii is not embraced in the value charged by the glazier for his glass so consumed. JrL DESCRIPTION or ^VRC'IIES fiy 6 fit, . 1 londim./liMufin/ /ly T/u'' Ar//r 17 I'ulrrnntlri- Kin; tf.ni / /, • ■ f:Tiirrt'H .Jf . PT^ITj CYCI^OOMAFJi. /■■;,/. /. />■u . Juh S /rfJr A so sax tu/.I. fit/.i. le*tJ,'n.hthb'.diei Hf 7hi*fA}iffif. /kt^tu\ffrr/ttir.Stpe, i. i,i35. J|fASO>'KT Pir S F /// n Vi t; £/Ufniir,/ A' /i/ifir L ii,L ■: ni.luk^.1 ririiriiei Jii'if MAS ON RY. TJ. n 2rrj. Jtrrj. _if h v Ti^.2 if Nf2. J\rf3. ]\r!'4. JSTfJ. ]S'.'6. JTfZ 2r2. Jff3. 2^4. 2iyj. Iff6. X'T. ^n^ravei bu V Svmfi J.oTiJon. J^Mshfti hy ThnfXfliif. 27 /^^Oerrws^rJidyw. Jji^ust M7d'35. J'UTK n: nx^o^iw /^WuVm /IwV/.r^. '^'AW/t /'Miiint4*t/rt /,','»■ MAS <>-?>' K V /'/, rni Fia.3 . '-\, \, ■■\i J-hr- 2 iniiiiisilniamiiii )^' . ..II iiiji;]Lirliiiii]:i \ v\ d I Fw.4 2^,1. K C T X J^i/y o. 2^iii. S £nar.n-fti f>vJi Ti^'f^'f /.ondcn.I^J'Ufhfd Iru ni'^AWfi'J~.^afrrrif-f/f/t,m:Ju/lJ'<1-'i .MASOMiV \- / \ / /■ ^ 1 thii Tht'hi.'ii' /'/A,-'/. >JASO>'KY I': A'. Ztt.iniieJ huhJtfli. l.,ii,hm fuMitheiycv.li.l/tSi hilT/le'Jx.n/ti I'iitfr>i,:flrrlt,'ir Srill J', li 3 r Al. VATLTS ov. DOMKS Fill j. PI. XI 1< RIBBED GROIIVS F£.zn. Lotulon.Publu-hed I'l/ThofEdbiJyFata-nosta-.Jiim: ^lufnsl ? /Ki.' Eupnif'tyi ht/£-Titi'iH/ >iASO>RV. P f.ri t t ■> r g p /. ,ulc/U'„hl,..i,.,l ,•),; JoS !,u nufiCdU ruta-nesta-Jii'i,. £naraffil tu JtA^tfSr. AXTIENT W:iiLL5, fi :•■/, /■>,/ / /■'ill 2 T>n :i J^,/ •/ .^^?^mf: . ."■:,:. i C.. - ■ ; " "' ,- i-'-;-{-f' J^l^ J 7^/f fi A'fsjfmrd Mf *' S^Mwu /.rm/^n. /*f/MjArf/ dv '/fir " AWAr, 17, ta^rarji/ty Aftf. jiy? V /'''.■<^. ^^HAKF,]>OCli,A?fI}» SEA WALLS. 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J.,mJ,ii l)ihli.tlu:l h- 77uCs^^i^\(M^v«^^^W^^\\^^v>^>;J^\«4.^^^ sssf^iM :v, \,: ■ •-;;,;-a!r^^^ - ! Fill J. f,^ 7. Loiulon J'iiNi.r/ifJ /ii/ ITu^iKellu J7 ftittrniKftrr Bfltrjynvmltfr 1S.IS3S. ■ '•:^^ s \ X lilhi-Hi I ^ r i 1 • I I / fs ^ LLUIii-L- ■ rjT ^-^^hvKr^H^ .. L_' 1 -,_-._ ^^r^ ^ • tf r -1 Hi :k o .1 .L, .K ii r 1 R. & ? h A V .!■: .s , pj^m zxxiv '1 no. J J-'u/.'i. Fit). 2. Fiti.4. (T' I k^-/ / I! [<((' K'i,.\ ^-r >'(i. PLAT I XXSV J-'iti II riff r> /..li.l.l, IIiI'IkI,.,! Iv n.-Krllv n /-.ilrrii.-.l.-l K.w /l,,'/''l/136 /■:. riinri/ m^^ T^ GAS n-OHKS '^^^•— --- ^T" /iy . 2 . e e f e frf- 't m^ H -n "Tn^ _L J , 1 M[[ L^_l ■ L.,..L ^^TT^-r'-iLbP O ff ;^ XT= ri; I n. ;;. _ZL PSFIP ^ r rr />V ^• J*/./ // i**** |). j'f. -ixnv J'if/ . 3 ■^ ^'^^ IJ-. - >/ J ^ ■ J'_ I X Ft If ■■> /// j / >^ 'J f„f / p^ f'l)/ . 6 . X^'if i:: 1- .f — /''le/ Li . 'fo fitf />*/. A'. ^i.„J I.. ,i- ,,; i, , :, . , i. ::■..■ A.:. 1. ^ /"!./.#: 'D, /•III .>' />v A' il^irzi '- n.i. I ri., '. \' f.,tiJ,i< hiNi..l„.l '■v Th.'-KRv n r.i/^in.:.t,r /\".w r>,;'l~'l"lf ^ ■■■■■i ;■ ^ ^ -w ui I 1 J-v _£racsa .-''\_ So 5^ -J « -<; , — -^ / r'^ 1 ;^ "~^"^;>^^,^_ ' -V-d P -^ ' 1^5^ »^^is^A;^^^ ^y'^' ^aU^iH T" iiiiiiliiililil h'i't/ii<- S'tvh- I'f Crntimi'iit . PLSL Jiq 1 //./ Tui ' Iig..9. fiV/ JO 5^ ^ 5 /^>t»n M' Jltf^*_£olxgtVi h'ndon DiNis/i^,/ A' n..' Kriiv n PaUnwst/r Jim t\t'l'^]fi3-t. £. Tamil sr (•i'//ilr \/\'/i' el' I'/// If //III// TIX/J /■•„/ /'/I/ .'-} /j/turti f'V Atf^M/f.^Kfii/i /,«./.« /•iiMi.,Af./ />v r/i.^KfUv' J/ fiii.m.-.s/.-r A'-ir /J^.'y'M-i /■: T/irtr/f ■' I' I, AN 'I' !•; U (>'(', A'//;:,//"/////// ■'/ '> />-/ /■•;-/ / />' 1 • I •( < ") K TA >.i !•: "^"r'. />-/ / />./ / /■•>', /Jfiiim M- AW'' A',:/-.. /<•/»./.•// /'ii/'/ish,./ M- 7/».''/7//c. ///■. S i , .vv I -x 1 ; . .Kiu/tr/is ,ir-^7fi/<'(/. SHIPWRECK OF THE STIRLING CASTLE, containing a Narrative of the Sutferings of the Crew, and the cruel Murder of Captain Eraser by the Savages. 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