'■ af'swwK'^iB-fgagawBMtwwHwiijapWHiawHf ^6 THE Imerican house-carpenter : A TREATISE UPON ARCHITECTURE, • CORNICES AND MOULDINGS FRAMING, DOORS, WINDOWS, AND STAIRS TOGETHER WITH THE MOST IMVORTAKT PRINCIPLES OF PRACTICAL GEOMETRY. BY R. G. HATFIELD, ARCHITECT. FIFTH EDITION, WITH ADDITIONS, JUustrateD bp more t{)dn V^x^t i)un^reti 2inarc-;biua3 NEW YORK: JOHN WILEY, 16V BROADWAY 1 8 52. X .A Entered, according to Act of Congress, in tiie year 1844, by R. G. HATFIELD, in tlift Clerk's Office of the District Court of the Southern District of New York. R, CRAIGHEAD, PRINTER, 53 Vesey Street, X Y f\ ^ J PREFACE. This book is intended for carpenters — for masters, journeymen and apprentices. It has long been the complaint of this class that architectural books, in- tended for their instruction, are of a price so high as to be placed beyond their reach. This is owing, in a great measure, to the costliness of the plates with which they are illustrated : an imnecessary expense, as illustrations upon wood, printed on good paper, answer every useful purpose. Wood engravings, too, can be distributed among the letter- press ; an advantage which plates but partially possess, and one of great importance to the reader. Considerations of this kind induced the author to undertake the preparation of this volume. The sub- ject matter has been gleaned from works of the first authority, and subjected to the most careful examina- tion. The explanations have all been written out from the figures themselves, and not taken from any other work ; and the figures have all been drawn ex- pressly for this book. In doing this, the utmost care has been taken to make every thing as plain as the nature of the case would admit. IV PREFACE. The attention of the reader is particularly directed to the following new inventions, viz : an easy method of describing the curves of mouldings through three given points ; a rule to determine the projection of eave cornices ; a new method of proportioning a cor- nice to a larger given one ; a way to determine the lengths and bevils of rafters for hip-roofs ; a way to proportion the rise to the tread in stairs ; to determine the true position of butt-joints in hand-rails ; to find the bevils for splayed-work ; a general rule for scrolls, &c. Many problems in geometry, also, have been simplified, and new ones introduced. Much labour has been bestowed upon the section on stairs, in which the subject of hand-rjiiling is presented, in many re- spects, in a new, and, it is hoped, more practical form than in previous treatises on that subject. The author has endeavoured to present a fund of useful information to the American house-carpenter that would enable him to excel in his vocation ; how far he has been successful in that object, the book itself must determine. PREFACE TO THE FIFTH EDITION. Since the first edition of this work was pubUshed, I have received numerous testimonials of its excellent practical value, from the very best sources, viz. from the workmen themselves who have used it, and who have profited by it. As a convenient manual for reference in respect to every question relating either to the simpler operations of Carpentry or the more intricate and abstruse problems of Geometry, those who have tried it assure me that they have been greatly assisted in using it. And, indeed, to the true workman, there is, in the study of the subjects of which this volume treats, a continual source of profitable and pleasurable interest. Gentlemen, in numerous instances have placed it in the hands of their sons, who have manifested a taste for practical studies ; and have also procured it for the use of the workmen upon their estates, as a guide in their mechanical operations. I was not, then, mistaken in my impressions, that a work of this kind was wanted ; and this evidence of its usefulness rewards me in a measure for the pains taken in its preparation. R. G. H. New York, Oct. 1, 1852. TABLE OF CONTENTS. INTRODUCTION. Articles necessary for drawing, To prepare the paper, Art. •2 5 To use the set-square, Directions for drawing, Art. 11 13 SECT. I.— PRACTICAL GEOMETRY. DEFINITIONS. Lines, - - . . 17 Angles, - - - 23 Angular point, . - - 27 Polygons, - - - 28 The circle, - - - 47 The cone, ... 56 Conic sections, - - - 58 The ellipsis, - - - 61 The cylinder, . - . 68 PROBLEMS. To bisect a line, - - 71 To erect a perpendicular, - 72 To let fall a perpendicular, 73 To erect ditto on end of line, 74 Six, eight and ten rule, - 74 To square end of board, - 74 To square foundations, &c., 74 To let fall a perpendicular near the end of a line, - 75 To make equal angles, - 76 To bisect an angle, - . 77 To .risect a right angle, 78 To draw parallel lines, - 79 To divide a line into equal parts, ... - 80 To find the centre of a circle, 81 To draw tangent to circle, 82 Do. without using centre, 83 To find the point of contact, 84 To draw a circle through three given points, - - 85 To find a fourth point in circle, 86 To describe a segment of a circle by a set-triangle, - 87 Do. by intersection of lines, 88 To curve an angle, - 89 To inscribe a circle within a given triangle, - - 90 To make triangle about circle, 91 To find the length of a cir- cumference, - - 92 To describe a triangle, hexa- gon, &c., ... 93 To draw an octagon, - 94 To eight-square a rail, &c., 94 To describe any polygon in a circle, ... 95 To draw equilateral triangle, 96 To draw a square by com- passes, - - - 97 To draw any polygon on a given line, ... 98 To form a triangle of required size, . . - . 99 To copy any right-lined figure, 100 To make a parallelogram equal to a triangle, - 101 To find the area of a triangle, 101 To make one parallelogram equal another, - - 102 To make one square equal to two others, - - - 103 To find the length of a rafter, 103 Vlll CONTENTS. Art. To find the length of a brace, 103 To ascertain the pitch of a roof, - - - - 103 To ascertain the rake of a step-ladder, - - - 103 To describe one circle equal to two others, - - 104 To make one polygon equal to two or more, - - 104 To make a square equal to a rectangle, - - 105 To make a square equal to a triangle, - - - 106 To find a third proportional, 107 To find a fourth proportional, 108 To proportion one ellipsis to another, - - - 108 To divide a line as another, 109 To find a mean proportional, 110 Definitions of confc sections, 111 To find the axes of an ellipti- cal section, - - - 112 To find the axes and base of the parabola, - - 113 To find the height, base and axes of the hyperbola, - 114 To find foci of ellipsis, - 115 To describe an ellipsis with a string, - - - 115 To describe an ellipsis with a trammel, - - 116 To construct a trammel, - 116 To describe an ellipsis by or- dinates, - - - 117 To trace a curve through given points, - - - 117 To describe an ellipsis by in- tersection of lines, - 118 120 121 122 128 124 125 126 127 128 Art. Do. from conjugate diameters, 118 Do. by intersecting arcs, - 119 To describe an oval by com- passes, - - - Do. in the proportion, 7x9, 5x7, &c., - To draw a tangent to an el- lipsis, To find the point of contact. To find a conjugate to the given diameter. To find the axes from given diameters, - - - To find axes proportionate to given ones, To describe a parabola by in- tersection of lines, - To describe hyperbola by do., DEMONSTRATIONS. Definitions, axioms, &;c.. ISO. 139 Addition of angles, - 140 Equal triangles, - - 141 Angles at base of isoceles tri- angle equal, - - 142 Parallelograms divided equal- ly by diagonal, - - 143 Equal parallelograms, - 144 Parallelogram equal triangles, 146 To make triangle equal poly- gon, - - . . 147 Opposite angles equal, • - 148 Angles of triangle equal two riglit angles, - - - 149 Corollaries from do., 150. 155 Ani^le in semi-circle a rijrht angle, - . - 156 Hecatomb problem, - - 157 SECT. II.— ARCHITECTURE. HISTORY. Antiquity of its origin, - 159 Its cultivation among the an- cients, - - - 160 Among the Greeks, - - 161 Among the Romans, - 162 Ruin caused by Gollis and Vandals, - - - I'^S Of the Gothic, . - 164 Of the Lombard, - - 165 CONTENTS. IX Art. Of the Byzantine and Oriental, 166 Moorish, Arabian and Modern Gothic, - - - 167 Of the English, - - 168 Revival of the art in the sixth century, - - - 169 The art improved in the 14th and 15th centuries, - 170 Roman styles cultivated, 171 STYLES. Origin of different styles, 172 Stylobate and pedestal, - 173 Definitions of an order, - 174 Of the several parts of an order, - - 175. 185 To proportion an order, - 186 The Grecian orders, - 187 Origin of the Doric, - - 188 Intercolumniation, - - 189 Adaptation, - - - 190 Origin of the Ionic, - 191 Characteristics, - - 192 Intercolumniation, - - 193 Adaptation, - - - 194 To describe the volute, - 195 Origin of the Corinthian, - 196 Adaptation, - - - 197 Persians, - - - - 199 Caryatides, - - - 200 The Roman orders, - - 202 Ah. Extent of Roman structures, 203 Roman styles copied from Grecian, - - . 208 Origin of the Tuscan, - 204 Adaptation, - - . 205 Characteristics of the Egypt- ian, .... 206 Extent of Egyptian structures, 206 Adaptation, - - . 207 Appropriateness of design, 208. 211 Durable structures, - - 212 Plans of dwellings, &c., 213 Directions for designing, 213, 214 PRINCIPLES. Origin of the art, - - 215 Arrangement and design, - 216 Ventilation and cleanliness, 217 Stability, - - - 218 Ornaments, - - - 219 Scientific knowledge neces- sary, - - - 220 The foundation, - - 221 The column, - . - 222 The wall, - - - 223 The lintel, - - - 224 The arch, - - . 225 The vault, - - - 226 The dome, - - - 227 The roof, - - - 228 SECT. HI.— MOULDINGS, CORNICES, &c. MOULDINGS, &C. Elementary forms, - - 229 Characteristics, - - 230 Grecian and Roman, - - 231 Profile, - - - 332 To describe the torus and scotia, - - - - 233 To describe the echinus, 234 To describe the cavetto, 235 To describe the cyma-recta, 236 To describe the cyma-reversa, 237 Roman mouldings, - 238 Modern mouldings, - - 239 Antse caps, - - - 240 CORNICES. Designs, - . - - 241 To proportion an eave cornice, 242 Do. from a smaller given one, - - - - 243 Do. from a larger given one, . - - . 244 To find shape of angle-bracket, 245 To find form of raking cornice, 246 CONTENTS. SECT. IV.— FRAMING. Art. Laws of pressure, - - 248 Parallelogram of forces, - 248 To measure the pressure on rafters, - - - 249 Do. on tie-beams, - 250 The effect of position, - 251 The composition of forces, 252 Best position for a strut, - 253 Nature of ties and struts, - 254 To distinguish ties from struts, 255 Lattice-work framing, - 256 Direction of pressure in raft- ers, - - - - 257 Oblique thrust of lean-to roofs, 258 Pressure on floor-beams, - 259 Kinds of pressure, - - 260 Resistance t» compression, 261 Area of post, - - 261 Resistance to tension, - 262 Area of suspending piece, 262 Resistance to cross-strains, 263 Area of bearing timbers, 263 Area of stiffest beam, - 264 Bearers narrow and deep, 265 Principles of framing, - 266 FLOORS. Single-joisted, - - 267 To find area of floor-timbers, 268 Dimensions of trimmers, &c., 269 Strutting between beams, 270 Cros8-furring and deafening, 271 Double floors, - - - 272 Dimensions of binding-joists, 273 Do. of bridging.joists, 274 Do. of ceiling-joists, - 275 Framed floors, - - - 276 Dimensions of girders, - 277 Girders sawn and bolted, - 278 Trussed girders, - * 279 Floors in general, - - 280 PARTITIONS. Nature of their construction, 281 Designs for partitions, - 282 Superfluous timber, - - 282 Improved method, - - 283 Weight of partitioning, - 284 ROOFS. Lateral strains, Pressure on roofs, Weight of covering, •Definitions, Relative size of timbers, Art 285 286 286 287 288 To find the area of a king- post, 289 Of a queen-post, - - 290 Of a tie-beam, - - - 291 Of a rafter, - - - 292 Of a straining-beam, - 294 Of braces, - - - 295 Of purlins, - - - 296 Of common rafters, - 297 To avoid shrinkage, - - 298 Roof with a built-rib, - 299 Badly-constructed roofs, - 300 To find the length and bevils in hip-roofs, - - 301 To find the backing of a hip- rafter, ... - 302 DOMES. With horizontal ties, - 303 Ribbed dome, - - - 304 Area of the ribs, - - 305 Curve of equilibrium, - 30^^ To describe a cubic parabola, 307 Small domes for stairways, 308 To find the curves of the ribs, 309 To find the shape of the cover- ing for spherical domes, 310 Do. when laid horizontally, 311 To find an angle-rib, - - 312 BRIDGES. Wooden bridge with tie-beam, 313 Do. without a tie-beam, 314 Do. with a built-rib, 315 Table of least rise in bridges, 315 Rule for built- ribs, - - 315 Pressure on arches, - 316 To form bent-ribs, - - 317 Elasticity of timber, - 317 To construct a framed rib, 318 Width of roadway, &c., - 319 Stone abutments and piers, 320 Piers constructed of piles, 321 CONTENTS. XI Art. Piles in ancient bridges, 321 Centring for stone bridges, 322 Pressure of arch-stones, - 322 Centre without a tie at the base, - - - 323 Construction of centres, - 324 General directions, - 325 Lowering centres, - - 326 Relative size of timbers, - 327 Short rule for do. - - 328 Joints between arch-stones, 329 Do. in elliptical arch, - 330 Do. in parabolic arch, - 331 JOINTS. Art. Scarfing, or splicing, 332. 334 To proportion the parts, - 335 Joints in beams and posts, - 336 Joints in floor-timbers, - 337 Timber weakened by framing, 338 Joints for rafters and braces, 339 Evil of shrinking avoided, - 340 Proper joint for collar-beam, 341 Pins, nails, bolts and straps, 342 Dimensions of straps, - 342 To prevent the rusting of straps, . - . . 342 SECT, v.— DOORS, WINDOWS, (fee. DOORS Dimensions of doors, - - 343 To proportion height to width, 344 Width of stiles, rails and panels, . . . 345 Example of trimming, - 346 Elevation of a door and trim- mings, - - - 347 General directions for hang- ing doors, - - - 348 WINDOWS. To determine the size, - 349 To find dimensions of frame, 350 To proportion box to flap shutter, - - - 351 To proportion and arrange windows, - - - 352 Circular-headed windows, 353 To find the form of the soffit, 354 Do. in a circular wall, - 355 SECT. VI.— STAIRS. Their position, - - - 356 Principles of the pitch-board, 357 To proportion the rise to the tread, - - - 358 The angle of ascent, - - 359 Length of steps, - - 360 To construct a pitch-board, 361 To lay-out the string, - 362 Section of step, - - 363 PLATFORM STAIRS. To construct the cylinder, - 364 To cut the lower edge of do., 365 To place the balusters, - 366 To find the moulds for the rail, - - - - 367 Elucidation of this method, 368 Two other examples, 369, 370 To apply the mould to the plank, - - - 371 To bore for the balusters, - 372 Face-mould for moulded rail, 373 To apply this mould to plank, 374 To ascertain thickness of stuff, 375 WINDING STAIRS- Flyers and winders, - 376 To construct winding stairs, 377 Xll CONTENTS. Art. Timbers to support winding stairs, ... - 378 To find falling-mould of rail, 379 To find face-mould of do., 380 Position of butt-joint, - 380 To ascertain thickness of stufl:; - - . - 381 To apply the mould to plank, 383 Elucidation of the butt-joint, 384 Quarter-circle stairs, - 385 Falling-mould for do., , - 386 Face-mould for do., - 387 Elucidation of this method, 388 To bevil edge of plank, - 389 To apply moulds without be- villing plank, - -. 390 AH. To find bevils for splayed- work, - - - 391 Another method for face- moulds, - - - 892 To apply face-mould to plank, 394 To apply falling-mould, . 395 SCROLLS. General rule, - - 396 To describe scroll for rail, 398 For curtail-step, - - 399 Balusters under scroll, - 400 Falling-mould for scroll, - 401 Face-mould for do., - 402 Round rails over winders, - 403 To find form of newel-cap, 404 SECT. VII.— SHADOWS. Inclination of line of shadow, 497 Shadows on mouldings, 408 Shadow of a shelf, - - 409 Of a shelf of varying width, 410 Of do. with oblique end, 411 Of an inclined shelf, - 412 Of do. inclined in section, 413 Of do. having a curved edge, 414 Of do. curved in elevation, 415 Shadow on cylindrical wall, 416 Do. on inclined wall, - 417 Shadow of a beam, - - 418 Shadow in a recess, - 419 Do. with wall inclined, - 420 Shadow in a fireplace, . 421 Shadow of window lintel, - 422 Shadow of step-nosing, - 423 Of a pedestal upon steps, - 424 Of square abacus on column, 425 Of circular abacus on do. 426 On the capital of a column, 427 Of column and entablature, 428 Shadows on Tuscan cornice, 429 Reflected light, - - 430 APPENDIX. Page. Glossary of Architectural Terms, - - ' - - 3 Table of Squares, Cubes and Roots, - - • - 14 Rules for extending the use of the foregoing table, - - 21 Rule for finding the roots of whole numbers with decimals, - 23 Rules for the reduction of Decimals, - - - 23 Table of Areas and Circumferences of Circles, - - - 25 Rules for extending the use of the foregoing table, - - 28 Table showing the Capacity of Wells, Cisterns, &c., - -29 Rules for finding the Areas, &;c., of Polygons, - - 30 Table of Weights of Materials, - - - - - 31 INTRODUCTION. Art. 1. — A knowledge of the properties and principles of lines can best be acquired by practice. Although the various problems throughout this work may be understood by inspection, yet they will be impressed upon the mind with much greater force, if they are actually performed with pencil and paper by the student. Science is acquired by study — art by practice : he, therefore, who would have any thing more than a theoretical, (which must of necessity be a superficial,) knowledge of Carpentry, will attend to the following directions, provide himself with the articles here specified, and perform all the operations described in the follow- ing pages. Many of the problems may appear, at the first read- ing, somewhat confused and intricate ; but by making one line at a time, according to the explanations, the student will not only succeed in copying the figures correctly, but by ordinary attention will learn the principles upon which they are based, £ind thus be able to make them available in any unexpected case to which they may apply. 2. — The following articles are necessary for drawing, viz : a drawing-board, paper, drawing-pins or mouth-glue, a sponge, a T-square, a set-square, two straight-edges, or flat rulers, a lead pencil, a piece of india-rubber, a cake of india-ink, a set of draw- ing-instruments, and a scale of equal parts. 3. — ^The size of the drawing-board must be regulated accord- ing to the size of the drawings which are to be made upon it. Yet for ordinary practice, in learning to draw, a board about 16 I 4 AMERICAN HOUSE CARPENTER. by 20 inches, and one inch thick, will be found large enough, and more convenient than a larger one. This board should be well-seasoned, perfectly square at the corners, and without clamps on the ends. A board is better without clamps, because the little service they are supposed to render by preventing the board from warping, is overbalanced by the consideration that the shrinking of the panel leaves the ends of the clamps project- ing beyond the edge of the board, and thus interfering with the proper working of the stock of the T-square. When the stufi is well-seasoned, the warping of the board will be but trifling ; and by exposing the rounding side to the fire, or to the sun, it may be brought back to its proper shape. 4. — For mere line drawings, the paper need not commonly be what is called drawing-paper ; as this is rather costly, and will, where much is used, make quite an item of expense. Cartridge-paper, as it is called, of about 20 by 26 inches, and of as good a quality nearly as drawing-paper, can be bought for about 50 cts. a quire, or 2 pence a sheet ; and each sjieet may be cut in halves, or even quarters, for practising. If the drawing is to be much used, as working drawings generally are, cartridge- paper is much better than the other kind. 5. — A drawing-pin is a small brass button, having a steel pin projecting from the under side. By having one of these at each corner, the paper can be fixed to the board ; but this can be done in a much better manner with mouth-glue. The pins will pre- vent the paper from changing its position on the board ; but, more than this, the glue keeps the paper perfectly tight and smooth, thus making it so much the more pleasant to work on. To attach the paper with mouth-glue, lay it with the bottom side up, on the board ; and with a straight-edge and penknife, cut oflf the rough and uneven edge. With a sponge moderately wet, rub all the surface of the paper, except a strip around the edge about half an inch wide. As soon as the glistening of the water disappears, turn the sheet over, and place it upon the INTRODUCTION. 3 board just where you wish it glued. Commence upon one of the longest sides, and proceed thus : lay a flat ruler upon the paper, parallel to the edge, and within a quarter of an inch of it With a knife, or any thing similar, turn up the edge of the papei against the edge of the ruler, and put one end of the cake o1 mouth-glue between your lips to dampen it. Then holding it upright, rub it against and along the entire edge of the paper that is turned up against the ruler, bearing moderately against the edge of the ruler, which must be held firmly with the left hand. Moisten the glue as often as it becomes dry, until a sufficiency of it is rubbed on the edge of the paper. Take away the ruler, restore the turned-up edge to the level of the board, and lay upon it a strip of pretty stiff paper. By rubbing upon this, not very hard but pretty rapidly, with the thumb nail of the right hand, so as to cause a gentle friction, and heat to be imparted to the glue that is on the edge of the paper, you will make it adhere to the board. The other edges in succession must be treated in the same manner. Some short distances along one or more of the edges, may afterwards be found loose : if so, the glue must again be applied, and the paper rubbed until it adheres. The board must then be laid away in a warm or dry place ; and in a short time, the sur- face of the paper will be drawn out, perfectly tight and smooth, and ready for use. The paper dries best when the board is laid level. When the drawing is finished, lay a straight-edge upon the paper, and cut it from the board, leaving the glued strip still attached. This may afterwards be taken off by wetting it freely with the sponge ; which will soak the glue, and loosen the paper. Do this as soon as the drawing is taken off, in order that the board may be dry when it is wanted for use again. Care must be taken that, in applying the glue, the edge of the paper does not become damper than the rest : if it should, the paper must be laid aside to dry, (to use at another time,) and another sheet be used in its place. 4 AMERICAN HOUSE CARPENTER. Sometimes, especially when the drawing board is new, the paper will not stick very readily ; but by persevering, this diffi- culty may be overcome. In the place of the mouth-glue, a strong solution of gum-arabic may be used, and on some accounts is to be preferred ; for the edges of the paper need not be kept dry, and it adheres more readily. Dissolve the gum in a sufficiency of warm water to make it of the consistency of linseed oil. It must be applied to the paper with a brush, when the edge is turned up against the ruler, as was described for the mouth-glue. If two drawing-boards are used, one may be in use while the other is laid away to dry ; and as they may be cheaply made, it is advisable to have two. The drawing-board having a frame around it, commonly called a panel-board, may afford rather more facility in attaching the paper when this is of the size to suit ; yet it has objections which overbalance that con sideration. 6. — A T-square of mahogany, at once simple in its construc- tion, and affording all necessary service, may be thus made. Let the stock or handle be seven inches long, two and a quarter inches wide, and three-eighths of an inch thick: the blade, twenty inches long, (exclusive of the stock,) two inches wide, and one-eighth of an inch thick. In joining the blade to the stock, a very firm and simple joint may be made by dovetailing it — as shown at Fig. 1. Fig. L INTRODUCTION. 7. — The set-square is in the form of a right-angled triangle ; and is commonly made of mahogany, one-eighth of an inch in thickness. The size that is most convenient for general use, is six inches and three inches respectively for the sides which con • tain the right angle ; although a particular length for the sides is by no means necessary. Care should be taken to have the square corner exactly true. This, as also the T-square and rulers, should have a hole bored through them, by which to hang them upon a nail when not in use. 8. — One of the rulers may be about twenty inches long, and the other six inches. The pencil ought to be hard enough to retain a fine point, and yet not so hard as to leave ineffaceable marks. It should be used lightly, so that the extra marks that are not needed when the drawing is inked, may be easily rubbed off with the rubber. The best kind of india-ink is that which will easily rub off upon the plate ; and, w^hen the cake is rub- bed against the teeth, will be free from grit. 9. — The drawing-instruments may be purchased of mathe- matical instrument makers at various prices : from one to one hundred dollars a set. In choosing a set, remember that the lowest price articles are not always the cheapest. A set, com- prising a sufficient number of instruments for ordinary use, well made and fitted in a mahogany box, may be purchased at Pike and Son's, (Broadway, near Maiden-lane, N. Y.,) for three or four dollars. The compasses in this set have a needle point, which is much preferable to a common point. 10.— The best scale of equal parts for carpenters' use, is one that has one-eighth, three-sixteenths, one-fourth, three-eighths, one-half, five-eighths, three-fourths, and seven-eighths of an inch, and one inch, severally divided into twelfths, instead ot being divided, as they usually are, into tenths. By this, if it be required to proportion a drawing so that every foot of the object represented will upon the paper measure one-fourth of an mch, use that part of the scale which is divided into one-fourths of an " AMERICAN HOUSE-CARPENTER. inch, taking for every foot one of those divisions, and for every inch one of the subdivisions into twelfths ; and proceed in like manner in proportioning a drawing to any of the other divisions of the scale. An instrument in the form of a semi-circle, called a protractor, and used for laying down and measuring angles, is of much service to surveyors, but not much to carpenters. ll.-In drawing p^allel lines, when they are to be parallel to either side of the board, use the T-square ; but when it is required to draw lines parallel to a line which is drawn in a direction oblique to either side of the board, the set-square must be used. Let a 6, {Fig. 2,) be a line, parallel to which it is Fiff. 2. desired to draw one or more lines. Place any edge, as c d, of the set-square even with said line ; then place the ruler, g h, against one of the other sides, as c e, and hold it firmly;' slide the set-square along the edge of the ruler as far as it is desired, as at/ ; and a line drawn by the edge, if, will be parallel to a b. 12.— To draw a line, as k I, {Fig. 3,) perpendicular to another, as a b, set the shortest edge of the set-square at the line, a b; place the ruler against the longest side, (the hypothenuse of the right-angled triangle ;) hold the ruler firmly, and slide the set- square along until the side, e d touches the point, k; then the line, I k, drawn by it, will be perpendicular to a b. In like INTRODUCTION. manner, the drawing of other problems may be facilitated, as will be d' tcovered in using the instruments. Fig. 3. 13. — In drawing a problem, proceed, with the pencil sharpened » a point, to lay down the several lines until the whole figure is completed; observing to let the lines cross each other at the several angles, instead of merely meeting. By this, the length of every line will be clearly defined. With a drop or two of water, rub one end of the cake of ink upon a plate or saucer, imtil a sujSiciency adheres to it. Be careful to dry the cake of ink ; because if it is left wet, it will crack and crumble in pieces. With an inferior camePs-hair pencil, add a little water to the ink that was rubbed on the plate, and mix it well. It should be diluted sufiiciently to flow freely from the pen, and yet be thick enough to make a black line. With the hair pencil, place a little of the ink between the nibs of the drawing-pen, and screw the nibs together until the pen makes a fine line. Beginning with the curved lines, proceed to ink all the lines of the figure ; being careful now to make every line of its requisite length. If they are a trifle too short or too long, the drawing will have a ragged appearance ; and this is opposed to that neatness and accuracy which is indispensable to a good drawing. When the ink is dry, efiace the pencil-marks with the india-rubber. If 8 AMERICAN HOUSE-CARPENTER. the pencil is used lightly, they will all rub off, leaving those lines only that were inked. 14. — In problems, all auxiliary lines are drawn light ; while the lines given and those sought, in order to be distinguished at a glance, are made much heavier. The heavy lines are made so, by passing over them a second time, having the nibs of the pen separated far enough to make the lines as heavy as desired. If the heavy lines are made before the drawing is cleaned with the rubber, they will not appear so black and neat ; because the india-rubber takes away part of the ink. If the drawing is a ground-plan or elevation of a house, the shade-lines, as they are termed, should not be put in until the drawing is shaded; as there is danger of the heavy lines spreading, when the brush, in shading or coloring, passes over them. If the lines are inked with common writing-ink, they will, however fine they may be made, be subject to the same evil ; for which reason, india-ink is the only kind to be used. THE AMERICAN HOUSE-CARPENTER. SECTION I.— PRACTICAL GEOMETRY. DEFINITIONS. 15. — Geometry treats of the properties of magnitudes. 16. — A -point has neither length, breadth, nor thickness. 17. —A line has length only. 18. — Superficies has length and breadth only. 19. — A plane is a surface, perfectly straight and even in every direction ; as the face of a panel when not warped nor winding. 20. — A solid has length, breadth and thickness. 21. — A right ^ or straight^ line is the shortest that can be drawn between two points. 22. — Parallel lines are equi-distant throughout their length. 23. — An angle is the inclination of two lines towards one another. i^Fig. 4.) Fig. 4. Fig. 5. Fig. & 2 10 AMERICAN HOUSE-CARPENTER. 24. — A right angle has one line perpendicular to the other. {Fig. 5.) 25. — An oblique angle is either greater or less than a right angle. [Fig- 4 and 6.) 26. — An acute angle is less than a right angle. [Fig. 4.) 27. — An obtuse angle is greater than a right angle. [Fig. 6.) When an angle is denoted by three letters, the middle one, in the order they stand, denotes the angular point, and the other two the sides containing the angle ; thus, let a 6 c, [Fig. 4,) be the angle, then b will be the angular point, and a b and b c will be the two sides containing that angle. 28. — A triangle is a superficies having three sides and angles. [Fig. 7, 8, 9 and 10.) Fig. 7. Fig. & 29. — An equi-lateral triangle has its three sides equal. {Pig. 7.) 30. — An isoceles triangle has only two sides equal. [Fig. 8.) 31. — A scalene triangle has all its sides unequal. [Fig. 9) Fix. 9. Fig. 10. 32. — A right-angled triangle has one right angle. [Fig. 10.) 33. — An acute-angled triangle has all its cingles acute. [Fig. 7 and 8.) 34. — An obtuse-angled triangle has one obtuse angle. [Fig. 9.) 35. — \ quadrangle has four sides and four angles. [Fig, 11 to 16.) PRACTICAL GEOMETRY. 11 Fig. 11. Fig. 12. 36. — A parallelogram is a quadrangle having its opposite sides parallel. {Fig. 11 to 14.) 37. — A rectangle is a parallelogram, its angles being right angles. {Fig. 11 and 12.) 38. — A square is a rectangle having equal sides. {Fig. 11.) 39. — A rhombus is an equi-lateral parallelogram having ob- lique angles. {Fig. 13.) Fig. 13. Fig. 14. 40. — A rhomboid is a parallelogram having oblique angles. (Fig. 14.) 41. — A trapezoid is a quadrangle having only two of its sides parallel. {Fig. 15.) Fig. 15. Fig. 16. 42. — A trapezium is a quadrangle which has no two of its sides parallel. {Fig. 16.) 43. — A polygon is a figure bounded by right lines. 44. — A regular polygon has its sides and angles equal. 45. — An irregular polygon has its sides and angles unequal, 46. — A trigon is a polygon of three sides, {Fig. 7 to 10 ;) a tetragon has four sides, {Fig. 11 to 16 ;) a pentagon has 12 AMERICAN HOUSE-CARPENTER. five, {Fig, 17 ;) a hexagon six, {Fig. 18 ;) a heptagon seven, {Fig. 19 ;) an octagon eight, {Fig. 20 ;) a nonagon nine ; a decagon ten ; an undecagon eleven ; and a dodecagon twelve sides. Fig. 17. Fig. 18. Fig. 19. Fig. 20. 47. — A circle is a figure bounded by a curved line, called the circumference ; which is every where equi-distant from a cer- tain point within, called its centre. The circumference is also called the periphery/, and sometimes the circle. 48. — The radius of a circle is a right line drawn from the centre to any point in the circumference, {a 6, Fig. 21.) All the radii of a circle are equal. Fi-. 21. 49. — The diameter is a right line passing through the centre, and terminating at two opposite points in the circumference. Hence it is twice the length of the radius, (c d, Fig. 21.) 50. — An arc of a circle is a part of the circumference, (c b or bed, Fig. 21.) 51. — A chord is a right line joining the extremities of an arc (6 d, Fig. 21.) PRACTICAL GEOMETRY. 13 52. — ^A segment is any part of a circle bounded by an arc and its chord. {A, Fig. 21.) 53. — A sector is any part of a circle bounded by an arc and two radii, drawn to its extremities, (i?, Fig, 21.) 54. — A quadrant^ or quarter of a circle, is a sector having a quarter of the circumference for its arc. (C, Fig. 21.) 55. — A tangent is a right line, which in passing a curve, touches, without cutting it. [f g^ Fig. 21.) 56. — A cone is a solid figure standing upon a circular base diminishing in straight lines to a point at the top, called its vertex. {Fig. 22.) Fig. 22. 57.— The axis of a cone is a right line passmg through it, from the vertex to the centre of the circle at the base. 58. — An ellipsis is described if a cone be cut by a plane, not parallel to its base, passing quite through the curved surface, (a 6, Fig. 23.) 59. — A parabola is described if a cone be cut by a plane, parallel to a plane touching the curved surface, (c rf, Fig. 23 — c d being parallel to / g.) 60. — An hyperbola is described if a cone be cut by a plane, parallel to any plane within the cone that passes through its vertex, (e A, Fig. 23.) 61. — Foci are the points at which the pins are placed in de- scribing an ellipse. (See Art. 115, and/,/, Fig, 24.) 14 AMERICAN HOUSE-CARPENTER. 62. — The transverse axis is the longest diameter of the ellipsis, [a b, Fig. 24.) 63. — The conjugate axis is the shortest diameter of the ellipsis ; and is, therefore, at right angles to the transverse axis. (c d, Fig. 24.) 64. — The parameter is a right line passing through the focus of an ellipsis, at right angles to the transverse axis, and termina- ted by the curve, {g h and g t, Fig. 24.) 65. — A diameter of an ellipsis is any right line passing through the centre, and terminated by the curve, {k I, or m n, Fig. 24.) 66. — A diameter is conjugate to another when it is parallel to a tangent drawn at the extremity of that other — thus, the diame- ter, m n, {Fig. 24,) being parallel to the tangent, o p, is therefore conjugate to the diameter, k I. 67. — A double ordinate is any right line, crossing a diameter of an ellipsis, and drawn parallel to a tangent at the extremity of that diameter, {i t, Fig. 24.) 68. — A cylinder is a solid generated by the revolution of a right-angled parallelogram, or rectangle, about one of its sides ; and consequently the ends of ^Lie :ylinder are equal circles. (Fig. 25.) PRACTICAL GEOMETRY. 15 Fig. 25. Fig. 26. 69. — The axis of a cylinder is a right line passing through it, from the centres of the two circles which form the ends. 70. — A segment of a cylinder is comprehended under three planes, and the curved surface of the cylinder. Two of these are segments of circles : the other plane is a parallelogram, called by way of distinction, the plane of the segment. The circular segments are called, the ends of the cylinder. {Fig. 26.) PROBLEMS. RIGHT LINES AND ANGLES. Tl. — To bisect a line. Upon the ends of the hne, a 6, {Fig. ^5) as centres, with any distance for radius greater than hall a b, describe arcs cutting each other in c and d ; draw the line, c d, and the point, e, where it cuts a b, will be the middle of the line, a b. In practice, a line is generally divided with the compasses, or dividers ; but this problem is useful where it is desired to draw, at the middle of another line, one at right angles to it. (See Art. 85.) d a Fig. 28. 72, — To erect a perpendicular* From the point, a, {Fig* 28,) PRACTICAL GEOMETRY. ir set oflf any distance, as a 6, and the same distance from a to c ; upon c, as a centre, with any distance for radius greater than c a, describe an arc at d ; upon 6, with the same radius, describe another at d ; join d and a, and the Une, d a, will be the per- pendicular required. This, and the three following problems, are more easily per- formed by the use of the set-square — (see Art. 12.) Yet they are useful when the operation is so large that a set-square cannot be used. Fig. 29. 73. — To let fall a 'perpendicular. Let a, [Fig. 29,) be the point, above the line, h c, from which the perpendicular is re- quired to fall. Upon a, with any radius greater than a d, de- scribe an arc, cutting 6 c at e and/; upon the points, e and/, with any radius greater than e d, describe arcs, cutting each other at g ; join a and g, and the line, a d, will be the perpen- dicular required. Fig. 30. 74. — To erect a perpendicular at the end of a line. Let a, (Fig. 30,) at the end of the line, c a, be the point at which the perpendicular is to be erected. Take any point, as 6, above the 3 18 AMERICAN HOUSE-CARPENTER. line, c a, and with the radius, b a, describe the arc, d a e, through d and Z>, draw the hue, d e ; join e and a, then e a will be the perpendicular required. The principle here made use of, is a very important one ; and is applied in many other cases — (see Art. 81, 6, and Art. 84. For proof of its correctness, see Art. 156.) 74, a. — A second method. Let &, {Fig. 31,) at the end of th* line, a b, be the point at which it is required to erect a perpen- dicular. Upon 6, with any radius less than b a, describe the arc, c e d ; upon c, with the same radius, describe the small arc at e, and upon e, another at d ; upon e and d, with the same or any other radius greater than half e d, describe arcs intersecting at / ; join/ and 6, and the line,/ 6, will be the perpendicular required. d Fig. 32. 74^ 5. — A third method. Let b, {Fig. 32,) be the given point at which it is required to erect a perpendicular. Upon b, with any radius less than b a, describe the quadrant, d ef; upon d, with the same radius, describe an arc at e, and upon e, another at c ; PRACTICAL GEOMETRY. 19 through d and e, draw d c, cutting the arc in c ; join c and 6, then c h will be the perpendicular required. This problem can be solved by the six^ eight and ten rule, as it is called ; which is founded upon the same principle as the problems at Art. 103, 104 ; and is applied as follows. Let a c?, [Fig. 30,) equal eight, and a e, six ; then, \i d e equals ten, the angle, e a c?, is a right angle. Because the square of six and that of eight, added together, equal the square of ten. thus : 6 X 6 = 36, ai*d 8 X 8 = 64 ; 36 + 64 = 100, and 10 x 10 - 100. Any sizes, taken in the same proportion, as six, eight and ten, will produce the same effect : as 3, 4 and .5, or 12, 16 and 20. (See note to Art. 103.) By the process shown at Fig. 30, the end of a board may be squared without a carpenters'-square. All that is necessary is a pair of compasses and a ruler. Let c a be the edge of the board, and a the point at which it is required to be squared. Take the point, 6, as near as possible at an angle of forty-five degrees, or on ami^re-line, from a, and at about the middle of the board. This is not necessary to the working of the problem, nor does it affect its accuracy, but the result is more easily obtained. Stretch the compasses from h to a, and then bring the leg at a around to d ; draw a line from c?, through 6, out indefinitely ; take the dis- tance, d b, and place it from b to e ; join e and a ; then e a will be at right angles to c a. In squaring the foundation of a build- ing, or laying-out a garden, a rod and chalk-line may be used instead of compasses and ruler. 75. — To let fall a perpendicular near the end of a line. Let e, {Fig. 30,) be the point above the line, c a, from which the perpendicular is required to fall. From e, draw any line, as e c?, obliquely to the line, c a ; bisect e d at b ; upon 6, with the radius, b e, describe the arc, e a d ; join e and a ; then e a will be the perpendicular required. 76. — To make an angle, (as e df Fig. 33,) eqnal to a given angle, (as b a c.) From the angular point, a, with any radius describe the arc, be; and with the same radius, on the line, d e, 20 AMERICAN HOUSE-CARPENTER. and from the point, c?, describe the arc,/^; take the distance, b c, and upon g, describe the small arc at/; join /and d ; and the angle, e df, will be equal to the angle, b a c. If the given line upon which the angle is to be made, is situa- ted parallel to the similar line of the given angle, this may be performed more readily with the set-square. (See Art. 11.) Fig. 34. 77. — To bisect an angle. Let a b c, {Fig. 34,) be the angle to be bisected. Upon b, with any radius, describe the arc, a c ; upon a and c, with a radius greater than half a c, describe arcs cutting each other at d ; join b and d ; and b d will bisect the angle, a 6 c, as was required. This problem is frequently made use of in solving other pro- blems ; it should therefore be well impressed upon the memory. Fig. 35. 78. — To trisect a right angle. Upon a, {Fig. 35,) with any tadius, describe the arc, b c ; upon b and c, with the same radius, describe arcs cutting the arc, 6 c, at c? and e ; from d and e, draw lines to a, and they will trisect the angle as was required. The truth of this is made evident by the following operation. Divide a circle into quadrants : also, take the radius in the divi- ders, and space off the circumference. This will divide the circumference into just six parts. A semi-circumference, there- PRACTICAL GEOMETRY. ^tl fore, is equal to three, and a quadrant to one and a half of those parts. The radius, therefore, is equal to f of a quadrant ; and this is equal to a right angle. Fig. 3G. 79. — Through a given pointy to draw a line parallel to a given line. Let a, {Fig. 36,) be the given point, and b c the given line. Upon any point, as CARPB:NTER. a line to the centre d ; bisect a d at e ; ^ipon e, with the radius, e a, describe the arc, afd;fis the point of contact required. If/ and d were joined, the line would form right angles with the tangent, b c. (See A/^t. 156.) b Fig. 44. 85. — Through any three points not in a straight line, to draw a circle. Let a, h and c, [Fig. 44,) be the three given points. Upon a and b, with any radius greater than half a b, describe arcs intersecting at d and e ; upon b and c, with any radius greater than half b c, describe arcs intersecting at /and g ; through d and e, draw a right line, also another through /and g ; upon the intersection, A, with the radius, h a, describe the cn*cie, ah c, and it will be the one required. Fig. 45. PRACTICAL GEOMETRY. 26 86. — Three points not in a straight line being given, to find a fourth that shall, with the three, lie in the circumference of a circle. Let a b c, {Fig. 45,) be the given points. Connect them with right lines, forming the triangle, a c b ; bisect the angle, cb a, {Art. 77,) with the line, b d ; also bisect c ain e, and erect e d, perpendicular to a c, cutting b d in d ; then d is i\iQ fourth point required. A fifth point may be found, as at/, by assuming a, d and b, as the three given points, and proceeding as before. So, also, any number of points may be found ; simply by using any three already found. This problem will be serviceable in obtaining short pieces of very flat sweeps. (See Art. 311.) 87. — To describe a segment of a circle by a sei-triaiigle. Let a b, {Fig. 46,) be the chord, and c d the height of the seg- ment. Secure two straight-edges, or rulers, in the position, c e and cf by nailing them together at c, and afiixing a brace from e to/; put in pins at a and b ; move the angular point, c, in the direction, a c b ; keeping the edges of the triangle hard against the pins, a and b ; a pencil held at c will describe the arc, a c b. If the angle formed by the rulers at c be a right angle, the segment described will be a semi-circle. This problem is useful in describing centres for brick arches, when they are required to be rather flat. Also, for the head hanging- stile of a window- frame, where a brick arch, instead of a stone lintel, is to be placed over it. g 1 1 h s :^^rr 1^^:^; 3 (2 3 Fig. 47. 4 26 AMERICAN HOUSE-CARPENTER. 88. — To describe the segment of a circle hy intersection of lines. Let a b, {Fig. AT,) be the chord, and c d the height of the segment. Through c, draw ef parallel to a b ; draw 6 /at right angles to c b ; make c e equal to c /; draw a g and b h, at right angles to a b ; divide c e, c f d a, d b, a g and b h, each into a like number of equal parts, as four ; draw the lines, 1 1, 2 2, &c., and from the points, o, o and o, draw lines to c ; at the intersection of these lines, trace the curve, a cb, which will be the segment required. In very large work, or in laying out ornamented gardens, &c., this will be found useful ; and where the centre of the proposed arc of a circle is inaccessible, it will be invaluable. (To trace the curve, see note at Art. 117.) Fig. 48. 89. — In a given angle, to describe a tanged curve. Let a b c, {Fig. 48,) be the given angle, and 1 in the line, a b, and 5 in the line, b c, the termination of the curve. Divide 1 b and b 5 into a like number of equal parts, as at 1, 2, 3, 4 and 5 ; join 1 and 1, 2 and 2, 3 and 3, &c. ; and a regular curve will be formed that will be tangical to the line, a b, at the point, 1, and to 6 c at 5. This is of much use in stair-building, in easing the angles formed between the wall-string and base of the hall, also between the front string and level facia, and in many other instances. The curve is not circular, but of the form of the parabola, {Fig. 93 ;) yet in large angles the difference is not perceptible. This problem can be applied to describing segments of circles for door- PRACTICAL GEOMETRY. 2T heads, window-heads, &c., to rather better advantage than Art, 87. For instance, let a b, {Fig. 49,) be the width of the open- ing, and c d the height of the arc. Extend c d^ and make d e equal to t, d ; join a and e, also e and b ; and proceed as direct- ed at Arf 89. Vv:. 90. — fo describe a circle within any given triangle^ so that the sides of the triangle shall be tangical. Let a b c, [i'^ig- 50,) be the given tiiangle. Bisect the angles, a and 6, according to Art. 77 ; upon d, the point of intersection of the bisecting lines, with the radius d e, describe ihe required circle. 91. — About a given circle, to describe an equi-lateral tri- angle. Let a d b c, {Fig. 51 ,) be the given circle. Draw the diameter, c d ; upon d, with the radius of the given circle, de- scribe the arc, a e b ; join a and b ; drsiW f g, at right angles to d c ; make/c and c g, each equal to a b ; from/, through a, draw / h, also from gj through 6, draw g h; thenfg h will be the triangle required. 28 AMERICAN HOUSE-CARPENTER. g P 92. — To find a right line nearly equal to the circumference of a circle. Let ah c d^ [Fig. 52,) be the given circle. Draw the diameter, a c ; on this erect a.n equi-lateral triangle, a e c, according to Art. 96 ; draw gf parallel to a c ; extend e c to/, also e ato g ; then ^/ will be nearly the length of the semi- circle, a d c ; and twice g f will nearly equal the circumference of the circle, ab c d^as was required. Lines drawn Irom e, through any points in the circle, as o, o and 0, top, p and/>, will divide gf in the same way as the semi- circle, a d c, is div^ioed. So, any portion of a circle may be transferred to a straight line Tni> i : \ very useful problem, and should be well studied ; as it is frequently used to solve problems on stairs, domes, <5lc. Fig. 53. 92, a. — Another method. Let a bf c, {Pig. 53,) be the given circle. Draw the diameter, a c ; from d, the centre, and at right angles to a c, draw d b ; join b and c ; bisect be at e; from rf, through e, draw df; then e/ added to three times the diameter, PRACTICAL GEOMETRY. 29 will equal the circumference of the circle within the 4^1)0 part of its length. POLYGONS, &c. 93. — Within a given circle^ to inscribe an equi-lateral tri- angUy hexagon or dodecagon. Let abed, {Fig. 54,) be the Ti., given circle. Draw the diaaieter, b d ; upon 6, with the radius v»f the given circle, dcFcribe the arc, a e c ; join a and c, also a eind d, and c and d — and the triangle is completed. For the I;e*xagon : from a, also from c, through e, draw the lines, a f and eg; join a and b, b and c, c and/, (fcc, and the hexagon is completed. The dodecagon may be formed by bisecting the sides of the hexagon. Each side of a regular hexagon is exactly equal to the radius of the circle that circumscribes the figure. For the radius is equal to a chord of an arc of 60 degrees ; and, as every circle is supposed to be divided into 360 degrees, there is just 6 times 60, vxr 6 arcs of 60 degrees, in the whole circumference. A line c'rawn from each angle of the hexagon to the centre, (as in the figure,) divides it into six equal, equi-lateral triangles. 30 AMERICAN HOUSE-CARPENTER. 94. — Within a square to inscribe an octagon. Let a b c d, {Fig. 55,) be the given square. Draw the diagonals, a d and 6c; upon a, 6, c and c?, with a e for radius, describe arcs cut- ting the sides of the square at 1, 2, 3, 4, 5, 6, 7 and 8 ; join 1 and 2, 3 and 4, 5 and 6, (fcc, and the figure is completed. In order to eight-square a hand-rail, or any piece that is to be afterwards rounded, draw the diagonals, a d and b c, upon the end of it, after it has been squared-up. Set a gauge to the dis- tance, a e, and run it upon the whole length of the stuff, from each corner both ways. This will show how much is to be chamfered oif, in order to make the piece octagonal. Fif?. 56. Fig. 57. 95. — Within a given circle to inscribe any regular polygon. Let a b c 2, [Fig. 56, 57 and 58,) be given circley. Draw the diameter, a c ; upon this, erect an equi-lateral triangle, a e c, according to Art. 96 ; divide a c into as many equ.^'. parts as the polygon is to have sides, as at 1, 2, 3, 4, (fee. ; ficii e, through each even number, as 2, 4, 6, &c., draw lines cuttmg the circle in the points, 2, 4, (fee. ; from these points and at right angles to a c, draw lines to the opposite part of the circle ; this will give the remaining points for the polygon, as b, /, (fee. In forming a hexagon, the sides of the triangle erected upon a c, (as at Fig. 57,) mark the points, b and/. 96. — Upon a given line to construct an equi-lateral triangle. Let a bj {Fig. 59,) be the given line. Upon a and b, with a b PRACTICAL GEOMETRY. 31 for radius, describe arcs intersecting at c ; join a and c, also c and b ; then a cb will be the triangle required. Fig. 60 97. — To describe an equi-latei^al j^ectangle, or square. Let a b, {Fig. 60,) be the length of a side of the proposed square. Upon a and b, with a b for radius, describe the arcs, a d and be; bisect the arc, a e, in / ; upon e, with e f for radius, describe the arc, c f d ; join a and c, c and d^ d and b ; then a c db will be the square required. Fig- 61. Fig. 62. Fig. 63. 98. — Upon a given line to describe any regular polygon. Let a 6, {Fig. 61, 62 and 63,) be given lines, equal to a side of the required figure. From 6, draw b c, at right angles to a 6 ; upon a and b, with a b for radius, describe the arcs, a c d and 32 AMERICAN HOUSE-CARPENrER. f eh ] divide a c into as many equal parts as the polygon is to have sides, and extend those divisions from c towards d ; from the second point of division counting from c towards a, as 3, {Fig, 61,) 4, {Fig. 62,) and 5, {Fig. 63,) draw a line to b ; take the distance from said point of division to a, and set it from b to e ; join e and a ; upon the intersection, o, with the radius, a. describe the circle, a f d b ; then radiating lines, drawn from b through the even numbers on the arc, a c?, will cut the circle at the several angles of the required figure. [n the hexagon, {Fig. 62,) the divisions on the arc, a d, are not necessary ; for the point, o, is at the intersection of the arcs, a d and/ 6, the points, /and d, are determined by the intersec- tion of those arcs with the circle, and the points above, g and A, can be found by drawing lines from a and b, through the centre, 0. In polygons of a greater number of sides than the hexagon, the intersection, o, comes above the arcs ; in such case, therefore, the lines, a e and h 5, {Fig. 63,) have to be extended before they will intersect. Fiff. 64. 99. — To construct a triangle whose sides shall be severally equal to three given lines. Let a, h and c, {Fig. 64,) be the given lines. Draw the line, d e, and make it equal to c ; upon e, wit}i b for radius, describe an arc at/; upon c?, with a for radius, describe an arc intersecting the other at/; join d and/, also/ and e ; then dfe will be the triangle required. Fig. 65. Fig. 66. PRACTICAL GEOMETRY. S3 100. — To construct a figure equal to a given^ right-lined figure. Let abed, {Fig. 65,) be the given figure. Make ef, {Fig. 66,) equal to c d ; upon /, with d a for radius, describe an arc at g ; upon e, with c a for radius, describe an arc intersecting the other at g ; join g and e ; upon / and g, with d b and a b for radius, describe arcs intersecting at h ; join g and A, also h and/; then Fig. 66 will every way equal Fig. 65. So, right-lined figures of any number of sides may be copied, oy first dividing them into triangles, and then proceeding as above. The shape of the floor of any room, or of any piece of land, (fee, may be accurately laid out by this problem, at a scale upon paper ; and the contents in square feet be ascertained by the next. 101. — To make a parallelogram equal to a given triangle. Let ab c, {Fig. 67,) be the given triangle. From a, draw a rf, at right angles to be; bisect a d in e ; through e, draw fg^ parallel to b c ; from b and c, draw b f and c g, parallel to d e ; then bfgc will be a parallelogram containing a surface exactly equal to that of the triangle, a b c. Unless the parallelogram is required to be a rectangle, the lines, b f and c g, need not be drawn parallel to d e. If a rhomboid is desired, they may be drawn at an oblique angle, provided they be parallel to one another. To ascertain the area of a triangle, multiply the base, b c, by half the perpendicular height, da. In doing this, it matters not which side is taken for base. A ^/ ^^ e ^^ C i Fig. 68. 5 34 AMERICAN HOUSE-CARPENTER. 102. — A parallelogram being given, to construct another equal to it, and having a side equal to a given line. Let A^ {Fig. 68,) be the given parallelogram, and B the given line Produce the sides of the parallelogram, as at a, 6, c and d ; make e d equal to B ; through c?, draw c /, parallel to g b ; through e, draw the diagonal, c a ; from a, draw a /, parallel to e d then C will be equal to A. (See Art. 144.) A a ^"V,^, B Fig 69. 103. — To make a square equal to two or fjtore given squares. Let A and B, {Fig. 69,) be two given squares. Place them so as to form a right angle, as at a ; join b and c ; then the square, C, formed upon the line, b c, will be equal in extent to the squares, A and B, added together. Again : if a b, {Fig. 70,) be equal to the side of a given square, c a, placed at right angles to a b, be the side of another given square, and c d, placed at right angles to PRACTICAL GEOMETRY. 35 c 6, be the side of a third given square ; then the square, A, formed upon the line, d 6, will be equal to the three given squares. (See Art. 157.) The usefulness and importance of this problem are proverbial. To ascertain the length of braces and of rafters in framing, the length of stair-strings, &c., are some of the purposes to which it may be applied in carpentry. (See note to Art. 74, b.) If the length of any two sides of a right-angled triangle is known, that of the third can be ascertained. Because the square of the hypothenuse is equal to the united squares of the two sides that contain the right angle. (1.) — The two sides containing the right angle being known, to find the hypothenuse. Rule. — Square each given side, add the squares together, and from the product extract the square- root : this will be the answer. For instance, suppose it were required to find the length of a rafter for a house, 34 feet wide,— the ridge of the roof to be 9 feet high, above the level of the wall-plates. Then 17 feet, half of the span, is one, and 9 feet, the height, is the other of the sides that contain the right angle. Proceed as directed by the rule : 17 17 9 9 119 17 - 81 = square of 9. 289 = square of 17. 289 - = square of 17. 370 Product. 1 ) 370 ( 19-235 + = square-root of 370 ; equal 19 feet, 2; in. 1 1 nearly : which would be the required — length of the rafter. 29 ) 270 9 261 382)- -900 2 764 3843 ) 13600 3 11529 38465)- 207100 192325 (By reference to the table of square-roots in the appendix, the root ot almost any number may be found ready calculated.) 36 AMERICAN HOUSE-CARPENTER. Ag^ir : suppose it be required, in a frame building, to find the length of a brace, having a run of three feet each way from the poixit oi" the right angle. The length of the sides containing the right angle will be each 3 feet : then, as before — 3 3 9 = square of one side. 3 times 3=9 = square of the other side. ] 8 Product : the square-root of which is 4*2426 -f ft., or 4 feet, 2 inches and :ths. full. (2.) — The hypothenuse and one side being known, to find the other £ide. Rnle. — Subtract the square of the given side from the square of tlie hypothenuse, and the square-root of the product will be the answer. Suppose it were required to ascertain the greatest perpendicular height a roof of a given span may have, when pieces of timber of a given length are to be used as rafters. Let the span be 20 feet, and the rafters of 3x4 hemlock joist. These come about 13 feet long. The known hypothenuse, then, is 13 feet, and the known side, 10 feet — that being half the span of the building. 13 13 39 13 169 = square of hypothenuse. 10 times 10 = 100 = square of the given side. 69 Product : the square-root of which is 8 •3066 + feet, or 8 feet, 3 inches and ^ths. full. This will be the greatest perpendicular height, as required. Again : suppose that in a story of 8 feet, from floor to floor, a step-ladder is re- quijed, the strings of which are to be of plank, 12 feet lone ; and it is desirable to know the greatest run such a length of string will aflford. In this case, the two given sides are — hypothenuse 12, perpendicular 8 feet. 12 times 12 ^ 144 = square of hypothenuse. 8 times 8 = 64 = square of perpendicular. 80 Product : the square-root of which is 8*9442 -f feet, or 8 feet, 11 inches and i^gths. — the answer, as re' 118. — To describe an ellipsis by intersection of lines. Let PRACTICAL GEOMETRY. 45 a b and c d, {Fig. 83,) be given axes. Through c, draw f g, parallel to a b ; from a and b, draw a / and b g, at right angles to ab ; divide f a, g b, a e and e 6, each into a like number of equal parts, as at 1, 2, 3 and o, o, o ; from 1, 2 and 3, draw lines tocy through o, o and o, draw lines from c?, intersecting those drawn to c ; then a curve, traced through the points, i, i, i, will be that of an ellipsis. Where neither trammel nor string is at hand, this, perhaps, is the most ready method of drawing an ellipsis. The divisions should be small, where accuracy is desirable. By this method, an ellipsis may be traced without the axes, provided that a diame- ter and its conjugate be given. Thus, a b and c d, {Fig- 84,) are conjugate diameters : f g is drawn parallel to a 6, instead of being at right angles to c d ; also, / a and g b are drawn paraUel to c dj instead of being at right angles to a b. 119. — To describe an ellipsis by intersecting arcs. Let a h 46 AMERICAN HOUSE-CARPENTER. and c d, {Fig. 85,) be given axes. Between one of the foci, / and/, and the centre, e, mark any number of points, at random, as 1, 2 and 3 ; upon /and/, with b 1 for radius, describe arcs at ^) ^5 §" ^^^ S ; upon/ and/ with a 1 for radius, describe arcs inter- secting the others at^,^,^ and g ; then these points of intersection will be in the curve of the ellipsis. The other points, h and i, are found in like manner, viz : h is found by taking h 2 for one radius, and a 2 for the other ; i is found by taking b 3 for one radius, and a 3 for the other, always using the foci for centres. Then by tracing a curve through the points, c, g, h, i, 6, &c., the ellipse will be completed. This problem is founded upon the same principle as that of the string. This is obvious, when we reflect that the length of the string is equal to the transverse axis, added to the distance between the foci. See Fig. 80; in Avhich c/ equals a e, the half of the transverse axis. /I '\ ^\ ^^ i ^ ^ i/ "/ g Fiff. 8G. 120. — To describe a figure nearly in the shape of an ellip- sis^ by a pair of compasses. Let a b and c d, {Fig. 86,) be given axes. From c, draw c e, parallel to ab ; from a, draw a e, parallel to c d; join e and c?; bisect e a in/; join / and c, inter- secting e dini; bisect i cin o ; from o, draw og, at right angles to i c, meeting c d extended to g ; join i and g, cutting the trans- verse axis in r ; make h j equal to h g, and h k equal to h r ; from J, through r and A:, draw j m and j n; also, from g, through k, araw g I; upon g and j, with g c for radius, describe the PRACTICAL GEOMETRY. 47 arcs, i I and m n ; upon r and k, with r a for radius, describe the arcs, m i and I n ; this will complete the figure. When the axes are proportioned to one another as 2 to 3, the extremities, c and d, of the shortest axis, will be the centres for describing the arcs, ^ Zand m ?i; and the intersection of e d with the transverse axis, will be the centre for describing the arc, m i, &c. As the elliptic curve is continually changing its course from that of a circle, a true ellipsis cannot be described with a pair of compasses. The above, therefore, is only an ^ipproximation. 121. — To draw an oval in the jjroportion^ seven by nine. Let c c?, {Fig. 87,) be the given conjugate axis. Bisect c d in o, and through o, draw a b, at right angles to c d ; bisect c o in e ; upon 0, with o e for radius, describe the circle, e f g- h ; from e, through h and/, draw ej and e i; also, from g, through h and/, draw g k and g I ; upon g, with g c for radius, describe the arc, kl ; upon e, with e d for radius, describe the arc, j i ; upon h and / with h k for radius, describe the arcs, j k and I i; this will complete the figure. This is a very near approximation to an ellipsis ; and perhaps no method can be found, by which a well-shaped oval can be drawn with greater facility. By a little variation in the process, ovals of different proportions may be obtained. If quarter of the trans- verse axis is taken for the radius of the circle, efg A, one will be drawn in the proportion, five by seven. 46 AMERICAN HOUSE-CARPENTER. 122. — To draw a tangent to an ellipsis. Let abed, {Fig. 88j) be the given ellipsis, and d the point of contact. Find the foci, [Art. 115,)/ and/, and from them, through d, draw/e and f d ; bisect the angle, [Art. 77,) e d o, with the line, 5 r ; then s r will be the tangent required. c Fig. 89. 123. — An ellipsis with a tangent given, to detect the point of contact, hetagbf, {Fig. 89,) be the given ellipsis and tan- gent. Through the centre, e, draw a h, parallel to the tangent j any where between e and/, draw c d, parallel to ab ; bisect c d in ; through o and e, dmwfg; then g will be the point of con- tact required. 124. — A diameter of an ellipsis given, to find its conjugate. Let a b, {Fig. 89,) be the given diameter. Find the line,/^, by the last problem; then/^ will be the diameter required. PRACTICAL GEOMETRY. 49 125. — An]/ diameter and its conjugate being given, to as- certain the two axes, a7id thence to describe the ellipsis. Let a b and c d, {Fig. 90,) be the given diameters, conjugate to one another. Through c, draw e /, parallel to a b ; from c, draw c g, at right angles to ef; make c g equal to a h or h b ; join g and h ; upon g, with g c for radius, describe the arc, i k c j ; upon A, with the same radius, describe the arc, I n ; through the int*"rsections, I and n, draw n o, cutting the tangent, ef, in o ; upon 0, with o gfov radius, describe the semi-circle, eig f ; join e and^, also g and/, cutting the arc, i c j, in k and t ; from e, through h, draw e 7?i, also from/, through A, draw//? ; from A; and ^, draw k r and ^ 5, parallel to^ A, cutting e ni in r, and/p in s ; make A ni equal to A r, and h p equal to h s ; then r m and 5 /> will be the axes required, by which the ellipsis may be drawn in the usual way. 126. — To describe an ellipsis, whose axes shall be propor- tionate to the axes of a larger or smaller given one. Let a cbd, {Fig. 91,) be the given ellipsis and axes, and i j the trans- verse axis of a proposed smaller one. Join a and c ; trom i, Iraw i e, parallel to a c ; make o f equal to oe ; then e/ will be 5C AMERICAN HOUSE-CARPENTER. the conjugate axis required, and will bear the same proportion to ij, asc d does to a b. (See Art. 108.) 2 3 m 3 2 Fi-. 92. 127. — To describe a parabola by intersection of lines. Lee m Ij {Fig. 92,) be the axis and height, (see Fig. 79,) and d dy & double ordinate and base of the proposed parabola. Through / draw a a, parallel to d d ; through d and d, draw d a and d a, parallel to ni I ; divide a d and d m^ each into a like number of equal parts ; from each point of division in d m, draw the lines, 1 1, 2 2, (fee, parallel Xoml; from each point of division in d a, draw lines to I ; then a curve traced through the points of intersection, o, o and o, will be that of a parabola. 127, a. — Another method. Let rn, I, {Fig. 93,) be the axis and height, and d d the base. Extend m I, and make I a equal to m I /join a and d, and a and d ; divide a d and a d. each into a like number of equal parts, as at 1, 2, 3, &c. ; join 1 and 1, 2 and 2, &c., and the parabola will be completed. PRACTICAL GEOMETRY. 51 iff T 3/ V a/ V 1/ V m Fig. 93. j>l2.. 141. — Proposition. Triangles that have two of their sides and the angle contained between them respectively equal, have also their third sides and the two remaining angles equal ; and consequently one triangle will every way equal the other. Let a b c, {Fig, 99,) and d efhe two given triangles, having the angle at a equal to the angle at d, the side, a b, equal to the side, d e, and the side, a c, equal to the side, df; then the third side of one, b c, is equal to the third side of the other, ef; the angle at b is equal to the angle at e, and the angle at c is equal to the angle at/. For, if one triangle be applied to the other, the three points, b, a, c, coinciding with the three points, e, d, /, the line, b c, must coincide with the line, e f; the angle at b with the angle at e ; the angle at c with the angle at/; and the triangle, 6 a c, be every way equal to the triangle, e df. 142. — Proposition. The two angles at the base of an isoceles triangle are equal. Let ab c, {Fig. 100,) be an isoceles triangle, of which the sides, a b and a c, are equal. Bisect the angle, {Art, 56 AMERICAN HOUSE-CARPENTER. 77,) b a Cjhy the line, a d. Then the line, b a, being equal to the line, a c ; the line, a d, of the triangle, A, being equal to the line, a d, of the triangle, B, being conmion to each ; the angle, b a dj being equal to the angle, d a c ; the line, b d, must, accord- ing to ArL 141, be equal to the line, dc ; and the angle at b must be equal to the angle at c. B Fi?. Mi. 143. — Proposition. A diagonal crossing a parallelogram di- vides it into two equal triangles. Let abed, [Fig. 101,) be a given parallelogram, and 6 c, a line crossing it diagonally. Then, as a c is equal to b cZ, and a b to c d, the angle at a to the angle at d, the triangle. A, must, according to Art. 141, be equal to the triangle, B. a /, A ^^^ ^^f C /^ ^^ D B I'l-. 10- 144. — Proposition. Let a h c d^ (^Vo-- 102,) be a given pa- rallelogram, and 6 c a dingoiial. At any distance between a b and c c?, draw e/, parallel to a b ; through the point, g, the intersection of the lines, b c and ef, draw h «, parallel to b d. In every paral- lelogram thus divided, the parallelogram, J, is equal to the paral- lelogram, B. According to xirt. 143, the triangle, a 6 c, is equal to the triangle, bed; the triangle, C, to the triangle, D ; and E to F ; this being the case, take D and F from the triangle, bed. and C and E from the triangle, a b c, and what remains PRACTICAL GEOMETRY. 57 in one must be equal to what remains in the other ; therefore, the parallelogram, A, is equal to the parallelogram, B. Fig. 103. 145. — Proposition. Parallelograms standing upon the same base and between the same parallels, are equal. Let ah c d and ef cd^ {Fig. 1()3,) be given parallelograms, standing upon the same base, c d, and between the same parallels, a f and c d. Then, ah and e/ being equal to c c/, are equal to one another: h e being added to both a h and e f^ a e equals h f ; the line, a c. being equal to h d, and a e to hf, and the angle, c a e, being equal, {Art. 135,) to the angle, d h f, the triangle, a e c, must be equal, {Art. 141,) to the triangle, hfd; these two triangles being equal, take the same amount, the triangle, beg, from each, and what remains in one, a h g c, must be equal to what remains in the other, efdg; these two quadrangles being equal, add the same amount, the triangle, c g d, to each, and they must still be equal ; therefore, the parallelogram, ah c d, is equal to the paral- lelogram, efcd. 146. — Corollary. Hence, if a parallelogram and triangle stand upon the same base and between the same parallels, the parallelo- gram will be equal to double the triangle. Thus, the paral- lelogram, a dj {Fig. 103,) is double, {Art. 143,) the triangle, c e d. 147. — Proposition. Let a h c d, {Fig. 104,) be a given quad- rangle with the diagonal, a d. From h, draw b e, parallel to a d; extend cdto e ; join a and e ; then the triangle, CARPENTER. tlie Other stories be placed perpendicularly over and under them ; and be careful to provide for head-room. To ascertain this, when it is doubtful, it is well to draw a vertical section of the whole stairs ; but in ordinary cases, this is not necessary. To dispose the windows properly, the middle Avindow of each story should be exactly in the middle of the front ; but the pier between the two windows which light the parlour, should be in the centre of that room ; because when chandeliers or any similar ornaments, hang from the centre-pieces of the parlour ceilings, it is important, ill order to give the better effect, that the pier-glasses at the front and rear, be in a range with them. If both these objects cannot be attained, an approximation to each must be attempted. The piers should in no case be less in width than the window open- ings, else the blinds or shutters when thrown open will interfere with one another; in general practice, it is well to make the out- side piers f of the width of one of the middle piers. When this is desirable, deduct the amount of the three openings from the width of the front, and the remainder will be the amount of the width of all tlie piers ; divide this by 10, and the product will be -^- of a middle pier; and then, if the parlour arrangements do not interfere, give twice this amount to each corner pier, and three times the same amount to each of the middle piers. PRINCIPLES OF ARCHITECTURE. 215. — In the construction of the first habitations of men, frail and rude as they must have been, the first and principal object was, doubtless, utility — a mere shelter from sun and rain. But as successive storms shattered the poor tenement, man was taught by experience the necessity of building with an idea to durability. And when in his walks abroad, the symmetry, proportion and beauty of nature met his admiring gaze, contrasting so strangely with the misshapen and disproportioned work of his own hands, he was led to make gradual changes ; till his abode was rendered ARCHITECTURE. 97 not only commodious and durable, but pleasant in its appearance ; and building became a fine-art, having utility for its basis. 2] 6. — In all designs for buildings of importance, utility, dura- bility and beauty, the first great principles of architecture, should be pre-eminent. In order that the edifice be useful, commodious and comfortable, the arrangement of the apartments should be such as to fit them for their several destinations ; for pubUc as- semblies, oratory, state, visitors, retiring, eating, reading, sleeping, bathing, dressing, (fee. — these should each have its own peculiar form and situation. To accomplish this, and at the same time to make their relative situation agreeable and pleasant, producing regularity and harmony, require in some instances much skill and sound judgment. Convenience and regularity are very import- ant, and each should have due attention ; yet when both cannot be obtained, the latter should in most cases give place to the for- mer. A building that is neither convenient nor regular, whatever other good qualities it may possess, will be sure of disappro- bation. 217. — The utmost importance should be attached to such ar- rangements as are calculated to promote health : among these, ven- tilation is by no means the least. For this purpose, the ceilings of the apartments should have a respectable height ; and the sky- light, or any part of the roof that can be made moveable, should be arranged with cord and puUies, so as to be easily raised and lowered. Small openings near the ceiling, that may be closed at pleasure, should be made in the partitions that separate the rooms from the passages — especially for those rooms which are used for sleeping apartments. All the apartments should be so arranged as to secure their being easily kept dry and clean. In dwellings, suitable apartments should be fitted up for bathings with all the necessary apparatus for conveying the water. 218. — To insure stability in an edifice, it should be designed upon well-known geometrical principles : such as science has de- monstrated to be necessary and sufficient for firmness and dura- 13 P8 AMERICAN HOUSE-CARPENTER. bility. It is well, also, that it have the appearance of stability as well as the reality ; for should it seem tottering and unsafe, the sensation of fear, rather than those of admiration and pleasure, will be excited in the beholder. To secure certainty and accu- racy in the application of those principles, a knowledge of the strength and other properties of the materials used, is indispensa- ble ; and in order that the whole design be so made as to be capable of execution, a practical knowledge of the requisite mechanical operations is quite important. 219. — The elegance of an architectural design, although chiefly depending upon a just proportion and harmony of the parts, will be promoted by the introduction of ornaments — provided this be judiciously performed. For enrichments should not only be of a proper character to suit the style of the building, but should also have their true position, and be bestowed in proper quantity. The most common fault, and one which is prominent in Roman archi- tecture, is an excess of em-ichment : an error which is carefully to be guarded against. But those who take the Grecian models for their standard, will not be liable to go to that extreme. In ornamenting a cornice, or any other assemblage of mouldings, at least every alternate member should be left plain ; and those that are near the eye should be more finished than those which are dis- tant. Although the characteristics of good architecture are utili- ty and elegance, in connection with durability, yet some buildings are designed expressly for use, and others again for ornament : in the former, utility, and in the latter, beauty, should be the gov- erning principle. 220. — The builder should be intimately acquainted with the principles upon which the essential, elementary parts of a build- ing are founded. A scientific knowledge of these will insure certainty and security, and enable the mechanic to erect the most extensive and lofty edifices with confidence. The more important parts are the foundation, the column, the wall, the lintel, the arch, the vault, the dome and the roof. A separate description of the ARCHITECTURE. 99 peculiarities of each, would seem to be necessary ; and cannot perhaps be better expressed than in the following language of a modern writer on this subject. 221. — "In laying the Foundation of any building, it is ne- cessary to dig to a certain depth in the earth, to secure a solid basis, below the reach of frost and common accidents. The most solid basis is rock, or gravel which has not been moved. Next to these are clay and sand, provided no other excavations have been made in the immediate neighbourhood. From this basis a stone wall is carried up to the surface of the ground, and constitutes the foundation. Where it is intended that the super- structure shall press unequally, as at its piers, chimneys, or columns, it is sometimes of use to occupy the space betv/een the points of pressure by an inverted arch. This distributes the pressure equally, and prevents the foundation from springing be- tween the different points. In loose or muddy situations, it is always unsafe to build, unless we can reach the solid bottoiu below. In salt marshes and flats, this is done by depositing tim- bers, or driving wooden piles into the earth, and raising walls upon them. The preservative quality of the salt will keep these timbers unimpaired for a great length of time, and makes the foundation equally secure with one of brick or stone. 222. — The simplest member in any building, though by no means an essential one to all, is the Column, ox pillar. This is a perpendicular part, commonly of equal breadth and thickness, not intended for the purpose of enclosure, but simply for tlie sup- port of some part of the superstructure. The principal force which a column has to resist, is that of perpendicular pressure. In its shape, the shaft of a column should not be exactly cylin- drical, but, since the lower part must support the weight of the superior part, in addition to the weight Avhich presses equally on the whole column, the thickness should gradually decrease from bottom to top. The outline of columns should be a little curved, so as to represent a portion of a very long spheroid, or paraboloid, 100 AMERICAN HOUSE-CARPENTER. rather than of a cone. This figure is the joint result of two cal- culations, independent of beauty of appearance, " One of these is, that the form best adapted for stability of base is that of a cone; the other is, that the figure, which would be of equal strength throughout for supporting a superincumbent weight, would be generated by the revolution of two parabolas round the axis of the column, the vertices of the curves being at its ex- tremities. The swell of the shafts of columns was called the en- tasis by the ancients. It has been lately found, that the columns of the Parthenon, at Athens, which have been commonly sup- posed straight, deviate about an inch from a straight line, and that their greatest swell is at about one third of their height. Columns in the antique orders are usually made to diminish one sixth or one seventh of their diameter, and sometimes even one fourth. The Gothic pillar is commonly of equal thickness throughout. 223. — The Wall, another elementary part of a building, may be considered as the lateral continuation of the column, answer- ing the purpose both of enclosure and support. A wall must diminish as it rises, for the same reasons, and in the same propor- tion, as the column. It must diminish still more rapidly if it ex- tends through several stories, supporting weights at different heights. A wall, to possess the greatest strength, must also con- sist of pieces, the upper and lower surfaces of which are horizon- tal and regular, not rounded nor oblique. The walls of most of the ancient structures which have stood to the present time, are constructed in this manner, and frequently have their stones bound together with bolts and cramps of iron. The same method is adopted in such modern structures as are intended to possess great strength and durability, and, in some cases, the stones are even dove-tailed together, as in the light-houses at Eddystone and Bell Rock, But many of our modern stone walls, for the sake of cheapness, have only one face of the stones squared, the inner ^alf of the wall being completed with brick ; so that they can, ARCHITECTURE. 101. in reality, be considered only as brick walls faced with stone. Such walls are said to be liable to become convex outwardly, from the difference in the shrinking of the cement. Rubble walls are made of rough, irregular stones, laid in mortar. The stones should be broken, if possible, so as to produce horizontal surfaces. The coffer walls of the ancient Romans were made by enclosing successive portions of the intended wall in a box, and filling it with stones, sand, and mortar, promiscuously. This kind of structure must have been extremely insecure. The Pantheon, and various other Roman buildings, are surrounded with a double brick wall, having its vacancy filled up with loose bricks and cement. The whole has gradually consolidated into a mass of great firmness. The reticulated walls of the Romans, having bricks with oblique surfaces, would, at the present day, be thought highly unphilosophical. Indeed, they could not long have stood, had it not been for the great strength of their cement. Modern brick walls are laid with great precision, and depend for firmness more upon their position than upon the strength of their cement. The bricks being laid in horizontal courses, and continually overlaying each other, or breaking joints^ the whole mass is strongly inter- woven, and bound together. Wooden walls, composed of timbers covered with boards, are a common, but more perishable kind. They require to be constantly covered with a coating of a foreign substance, as paint or plaster, to preserve them from spontaneous decomposition. In some parts of France, and elsewhere, a kind of wall is made of earth, rendered compact by ramming it in moulds or cases. This method is called building in pise^ and is much more durable than the nature of the material would lead us to suppose. Walls of all kinds are greatly strengthened by angles and curves, also by projections, such as pilasters, chimneys and buttresses. These projections serve to increase the breadth of the foundation, and are always to be made use of in large buildings, and in walls of considerable length. 102 AMERICAN HOUSE-CARPENTER. 224. — The Lintel, or heam^ extends in a right line over a vacant space, from one column or wall to another. The strength of the lintel will be greater in proportion as its transverse vertical diameter exceeds the horizontal, the strength being always as the square of the depth. The floor is the lateral continuation or connection of beams by means of a covering of boards. 225. — The Arch is a transverse member of a building, an- swering the same purpose as the lintel, but vastly exceeding it in strength. The arch, unlike the lintel, may consist of any num- ber of constituent pieces, without impairing its strength. It is, however, necessary that all the pieces should possess a uniform shape, — the shape of a portion of a wedge, — and that the joints, formed by the contact of their surfaces, should point towards a common centre. In this case, no one portion of the arch can be displaced or forced inward ; and the arch cannot be broken by any force which is not sufficient to crush the materials of which it is made. In arches made of common bricks, the sides of which are parallel, any one of the bricks might be forced inward, were it not for the adhesion of the cement. Any two of the bricks, however, by the disposition of their mortar, cannot collective- ly be forced inward. An arch of the proper form, when com- plete, is rendered stronger, instead of weaker, by the pressure of a considerable weight, provided this pressure be uniform. While building, however, it requires to be supported by a centring of the shape of its internal surface, until it is complete. The upper stone of an arch is called the key-stone, but is not more essential than any other. In regard to the shape of the arch, its most simple form is that of tlie semi-circle. It is, however, very fre- quently a smaller arc of a circle, and, still more frequently, a por- tion of an ellipse. The simplest theory of an arch supporting itself only, is that of Dr. Hooke. The arch, when it has only its own weight to bear, may be considered as the inversion of a chain, suspended at each end. The chain hangs in such a form, that the weight of each link or portion is held in equilibrium by ARCHITECTURE. 103 the result of two forces acting at its extremities ; and these forces, or tensions, are produced, the one by the weight of the portion of the chain below the Unk, the other by the same weight increased by that of the link itself, both of them acting originally in a ver- tical direction. Now, supposing the chain inverted, so as to con- stitute an arch of the same form and weight, the relative situa- tions of the forces will be the same, only they will act in contrary directions, so that they are compounded in a similar manner, and balance each other on the same conditions. The arch thus formed is denominated a catenary arch. In common cases, it differs but little from a circular arch of the extent of about one third of a whole circle, and rising from the abut- ments with an obliquity of about 30 degrees from a perpendicu- lar. But though the catenary arch is the best form for support- ing its own weight, and also all additional weight which presses in a vertical direction, it is not the best form to resist lateral pressure, or pressure like that of fluids, acting equally in all direc- tions. Thus the arches of bridges and similar structures, when covered with loose stones and earth, are pressed sideways, as well as vertically, in the same manner as if they supported a Aveight of fluid. In this case, it is necessary that the arch should arise more perpendicularly from the abutment, and that its general figure should be that of the longitudinal segment of an ellipse. In small arches, in common buildings, where the disturbing force is not great, it is of little consequence what is the shape of the curve. The outlines may even be perfectly straight, as in the tier of bricks which we frequently see over a window. This is, strictly speaking, a real arch, provided the surfaces of the bricks tend towards a common centre. It is the weakest kind of arch, and a part of it is necessarily superfluous, since no greater portion can act in supporting a weight above it, than can be included be- tween two curved or arched lines. Besides the arches already mentioned, various others are in use. The acute or lancet arch, much used in Gothic architecture, is 104 AMERICAN HOUSE-CARPENTER. described usually from two centres outside the arch. It is a strong arch for supporting vertical pressure. The rampant arch is one in which the two ends spring from unequal heights. The horse-shoe or Moorish arch is described from one or more centres placed above the base line. In this arch, the lower parts are in danger of being forced inward. The ogee arch is concavo-con- vex, and therefore fit only for ornament. In describing arches, the upper surface is called the extrados^ and llie inner, the in- trados. The springing lines are those where the intrados meets the abutments, or supporting walls. The span is the distance from one springing line to the other. The wedge-shaped stones, which form an arch, are sometimes called voiissoirs, the upper- most being the key-stone. The part of a pier from which an arch springs is called the impost^ and the curve formed by the upper side of the voussoirs, the archivolt. It is necessary that the walls, abutments and piers, on which arches are supported, should be so firm as to resist the lateral thrust^ as well as vertical pressure, of the arch. It will at once be seen, that the lateral or side way pressure of an arch is very considerable, when we recol- lect that every stone, or portion of the arch, is a wedge, a part of whose force acts to separate the abutments. For want of atten- tion to this circumstance, important mistakes have been committed, the strength of buildings materially impaired, and their ruin ac- celerated. In some cases, the w^ant of lateral firmness in the walls is compensated by a bar of iron stretched across the span of the arch, and connecting the abutments, like the tie-beam of a roof. This is the case in the cathedral of Milan and some other Gothic buildings. In an arcade, or continuation of arches, it is only necessary that the outer supports of the terminal arches should be strong enough to resist horizontal pressure. In the intermediate arches, the lat- eral force of each arch is counteracted by the opposing lateral force of the one contiguous to it. In bridges, however, where individual arches are liable to be destroyed by accident, it is desi- ARCHITECTURE. 105 rable that each of the piers should possess sufficient horizontal strength to resist the lateral pressure of the adjoining arches. 226. — The Vault is the lateral continuation of an arch, serving to cover an area or passage, and bearing the same relation to the arch that the wall does to the column. A simple vault is con- structed on the principles of the arch, and distributes its pressure equally along the walls or abutments. A complex or groined vault is made by two vaults intersecting each other, in whicji case the pressure is thrown upon springing points, and is greatly increased at those points. The groined vault is common in Gothic architecture. 227. — The Dome, sometimes called cupola^ is a concave cover- ing to a building, or part of it, and may be either a segment of a sphere, of a spheroid, or of any similar figure. When built of stone, it is a very strong kind of structure, even more so than the arch, since the tendency of each part to fall is counteracted, not only by those above and below it, but also by those on each side. It is only necessary that the constituent pieces should have a common form, and that this form should be somewliat iilve ihe frustum of a pyramid, so that, when placed in its situation, its four angles may point toward the centre, or axis, of the dome. During the erection of a dome, it is not necessary that it should be supported by a centring, until complete, as is done in the arch. Each circle of stones, when laid, is capable of supporting itself without aid from those above it. It follows that the dome may be left open at top, without a key-stone, and yet be perfectly secure in this respect, being the reverse of the arch. The dome of the Pantheon, at Rome, has been alwa^^s open at top, and yet has stood unimpaired for nearly 2000 years. The upper circle of stones, though apparently the weakest, is nevertheless often made to support the additional weight of a lantern or tower above it. In several of the largest cathedrals, there are two domes, one within the other, which contribute their joint support to the lan- tern, which rests upon the top. In these buildings, the dome 14 106 AMERICAN HOUSE-CARPENTER. rests upon a circular wall, which is supported, in its turn, by arches upon massive pillars or piers. This construction is called •building upon pendentives^ and gives open space and room for passage beneath the dome. The remarks which have been made ill regard to the abutments of the arch, apply equally to the walls immediately supporting a dome. They must be of sufficient thickness and solidity to resist the lateral pressure of the dome, which is very great. The walls of the Roman Pantheon are of ^leat depth and solidity. In order that a dome in itself should be perfectly secure, its lower parts must not be too nearly vertical, since, in this case, they partake of the nature of perpendicular vrails, and are acted upon by the spreading force of the parts above them. The dome of St. Paul's church, in London, and some others of similar construction, are bound with chains or hoops of iron, to prevent them from spreading at bottom. Domes which are made of wood depend, in part, for their strength, on their in- ternal carpentry. The Halle du Bled, in Paris, had originally a wooden dome more than 200 feet in diameter, and only one foot in thickness. This has since been replaced by a dome of iron. (See Art. 303.) 228. — The Roof is the most common and cheap method of covering buildings, to protect them from rain and other effects of the weather. It is sometimes fiat, but more frequently oblique, in its shape. The flat or platform-roof is the least advantageous for shedding rain, and is seldom used in northern countries. The pent roof, consisting of two oblique sides meeting at top, is the most common form. These roofs are made steepest in cold cli- mates, where they are liable to be loaded with snow. Where the four sides of the roof are all oblique, it is denominated a hipped roof, and where there are two portions to the roof, of different ob- liquity, it is a curb, or ^nansard roof. In modern times, roofs are made almost exclusively of Avood, though frequently covered with incombustible materials. The internal structure or carpen- try of roofs is a subject of considerable mechanical contrivance. ARCHITECTURE. 107 The roof is supported by rafters^ which abut on the walls on each side, Uke the extremities of an arch. If no other timbers existed, except the rafters, they would exert a strong lateral pres- sure on the walls, tending to separate and overthrow them. To counteract this lateral force, a tie-heam^ as it is called, extends across, receiving the ends of tlic rafters, and protecting the wall from their horizontal thrust. To prevent the tie-beam from sagging^ or bending dovv^nward with its own weight, a king- post is erected from this beam, to the upper angle of the rafters, serving to connect the whole, and to suspend the weight of the beam. This is called tritssing. Qiueeii-posts aie : omctimcs added, parallel to the king-post, in iarge roofs ; also various other connecting timbers. In Gothic buildings, where the vauUs do not admit of the use of a tie-beam, the rafters are prevented from spreading, as in an arch, by the strength of the buttresses. In comparing the lateral pressure of a high roof with that of a low one, the length of the tie-beam being the same, it will be seen that a high roof, from its containing most materials, may produce the greatest pressure, as far as weight is concerned. On the other hand, if the weight of both be equal, then the low roof will exert the greater pressure ; and this will increase in propor- tion to the distance of the point at which perpendiculars, drawn from the end of each rafter, would meet. In roofs, as well as in wooden domes and bridges, the materials are subjected to an in- ternal strain, to resist which, the cohesive strength of the niateria! is relied on. On this account, beams should, when possible, be of one piece. Where this cannot be effected, two or more beams are connected together by splicing. Spliced beams are never so strong as whole ones, yet they may be made to approach the same strength, by affixing lateral pieces, or by making the ends overlay each other, and connecting them with bolts and straps of iron. The tendency to separate is also resisted, by letting the two pieces into each other by the process called scarfing. Mortices, in- 108 AMERICAN HOUSE-CARPENTER. tended to truss or suspend one piece by another, should be formed "ipon similar principles. Roofs in the United States, after being boarded, receive a se- condary covering of shingles. When intended to be incombustible, they are covered with slates or earth ern tiles, or with sheets of lead, copper or tinned iron. Slates are preferable to tiles, being lighter, and absorbing less moisture. Metallic sheets are chiefly used for flat roofs, wooden domes, and curved and angular surfaces, which require a flexible material to cover them, or have not a sufficient pitch to shed the rain from slates or shingles. Various artificial compositions are occasionally used to cover roofs, the most com- mon of which are mixtures of tar with lime, and sometimes with sand and gravel." — Ency. Am. (See Art. 285.) NOTE TO ARTICLE 189. Gi'ECiAN DoiJic Orper. When the xcidth to be occupied by the whole front is limited ; to deter- mine tiie dianutLr of ihe colmnn. The relation between the parts may be expressed thus : _ 00 o '^ ~ «:(i + c) + (60 — c) Where a eq'i;il« tii • width in feet occupied by the cohTmns, and their intercolumuiations taken collectively. ni.'.isi'jvJ at tlie base ; b eci'.ials the width of the metope, in miniUes; c equ;tls the width of the trigiypij-- in iuiuuteij; d equals the number of metopes, iX'-A z equals the di;iinet(=r in feet. ExampU. — A ir.mi. of six columns— hexiistyle— 61 feet wide; thi- frieze having one triyjlyph over each intercolumtiirnion, or mono-triij!y;)h. In this case, there hexw.; five intercoluminatious aud two metopes over e:.c!). tiierefore there ai-o 5 X 2=^ 10 metope:?. Let ihe metispe equal 4'2 minutes and (he triglyph op;;.; 2-^. T:ien = 01; Z' = 42; r = W; auJ d=z 10; and the formula above becoiaos, ' - iTi-^-jr^— ^ (GiT^ITo^ - i0^;) + 32= 732"= ^ *"^' ^ ^'"^ ^'^'"'^'' x^^'^\r^(^. Example. — Aii uct-istyit' fror^t, 8 coiunins, 1S4 feel wide, threi- metopes over each inter col urania- lion, 21 in all, nud the metope and triglyph 42 and 28, as bel'orr. Then, ' ^ 21(42 + 2dH-~(6(ri28y = 1^ = '-^^TS o 2 fcct = the d.ameter required. SKCTION III.— MOULDINGS, CORNICES, &c. MOULDINGS. 229. — A moulding is so called, because of its being of the same determinate shape along its whole length, as though the whole of it had been cast in the same mould or form. The regular mouldings, as found in remains of ancient architecture, are eight in number ; and are known by the following names : Annulet, band, cincture, fillet, listel or square. Fip. ]23. Fig. 124. _) Astragal or bead. Fig. 125. ^ Torus or tore. L Fig: 126. Scotia, trochilus or mouth. Ovolo, quarter-round or echinas. Fig. !27. 110 AMERICAN HOUSE-CARPENTER. Cavetto, cove or hollow. Fij-. 128. ^ Cymatium, or cyma-recta. Fig. 129. / Inverted cymatiumj or cyma-reversa Fit^. 130. ) Some of the terms are derived thus : fillet, from the French word Jil, thread. Astragal, from astragalos^ a bone of the heel — or the curvature of the heel. Bead, because this moulding, when properly carved, resembles a string of beads. Torus, or tore, the Greek for rope^ which it resembles, when on the base of a column. Scotia, from shotia, darkness, because of the strong shadow which its depth produces, and Avhich is increased by the projection of the torus above it. Ovolo, from ovum, an egg, which this member resembles, when carved, as in the Ionic capi- tal. Cavetto, from cavus, hollow. Cymatium, from ^"^/ma^o«, a wave. 230. — Neither of these mouldings is peculiar to any one of the orders of architecture, but each one is common to all ; and al- though each has its appropriate use, yet it is by no means con- fined to any certain position in an assemblage of mouldings. The use of the fillet is to bind the parts, as also that of the astra- gal and torus, which resemble ropes. The ovolo and cyma-re- versa are strong at their upper extremities, and are therefore used to support projecting parts above them. The cyma-recta and cavetto, being weak at their upper extremities, are not used as supporters, but are placed uppermost to cover and shelter the other parts. The scotia is introduced in the base of a column, to MOULDINGS, CORNICES, &C. 1 I I separate the upper and lower torus, and to produce a pleasing variety and relief. The form of the bead, and that of the torus, is the same ; tlie reasons for giving distinct names to tliem are. that the torus, in every order, is always considerably larger than the bead, and is placed among the base mouldings, whereas the bead is never placed there, but on the capital or entablature ; the torus, also, is never carved, whereas the bead is ; and while the torus among the Greeks is frequently elliptical in its form, the bead retains its circular shape. While the scotia is the reverse of the torus, the cavetto is the reverse of the ovolo, and the cyma- rectaand cyma-reversa are combinations of the ovolo and cavetto. 231. — The curves of mouldings, in Roman architecture, were most generally composed of parts of circles ; while those of the Greeks were almost always elliptical, or of some one of the conic sections, bat rarely circular, except in the case of the bead, which was always, among both Greeks and Romans, of the form of a semi-circle. Sections of the cone afford a greater variety of forms than those of the sphere ; and perhaps this is one reason why the Grecian architecture so much excels the Roman. The quick turnings of the ovolo and cyma-reversa, in particular, when exposed to a bright sun, cause those narrow, well-defined streaks of light, which give life and splendour to the whole. 232. — A profile is an assemblage of essential parts and mould- ings. That profile produces the happiest effect which is com- posed of but few members, varied in form and size, and arranged so that the plane and the curved surfaces succeed each other al- ternately. 233. — To describe the Grecian torus and scotia. Join the extremities, a and 6, {Fig. 131 ;) and from/, the given projection of the moulding, draw/ o, at right angles to the fillets ; from 6, draw h A, at right angles to a b ; bisect a b in c ; join / and c, and upon c, with the radius, c/ describe the arc, / h, cutting b h in h ; through c, draw d e, parallel with the fillets ; make d c and c e, each equal to b h ; then d e and a b will be conjugate diame- 112 AMERICAN HOUSE-CARPENTER. Fig. 131. ters of the required ellipse. To describe the curve by intersec- tion of lines, proceed as directed at Art. 118 and note; by a trammel, see Art. 125 ; and to find the foci, in order to describe it with a string, see Art. 115. d \ ^ a Fig. 133 234. — Fig. 132 to 139 exhibit various modifications of the Grecian ovolo, sometimes called echinus. Fig. 132 to 136 eire MOULDINGS, CORNICES, &C. 113 Fii:. 134. Vl'r. 135. Fiar.lSe. Fig. 13* ^ b Fig. 138. Fig. 139. elliptical, a b and b c being given tangents to the curve ; parallel to which, the semi-conjugate diameters, a d and d c, are drawn. In Fig. 132 and 133, the lines, a d and d c, are semi-axes, the tangents, a b and b c, being at right angles to each other. To draw the curve, see Art. 118. In Fig. 137, the curve is para- bolical, and is drawn according to Art. 127. In Fig. 138 and 139, the curve is hyperbolical, being described according to Art. 128. The length of the transverse axis, a 6, being taken at pleasure in order to flatten the curve, a b should be made short in propor- tion to a c. 15 114 AMERICAN HOUSE-CARPENTER. Fig. 141. Fig. 140. 235. — To describe the Grecian cavetto, {Fig. 140 and 141,) having the height and projection given, see Art. 118. a I \iw 1^ Wi V c Fiff. 142. Fig. 143. 236. — To describe the Grecian cyma-recta. When the pro- jection is more than the height, as at Fig. 142, make a b equal to the height, and divide ah c d into 4 equal parallelograms ; then proceed cis directed in note to Art. 118. When the projec- tion is less than the height, draw d a, {Fig. 143,) at right angles to a b ; complete the rectangle, abed; divide this into 4 equal rectangles, and proceed according to Art. 118. Fi-. 114 237. — To describe the Grecian cyma-reversa. When the MOULDINGS, CORNICES, &C. 115 projection is more than the height, as at Fig. 144, proceed as di- rected for the last figure ; the curve being the same as that, the position only being changed. When the projection is less than the height, draw a d, {Fig. 145,) at right angles to the fillet ; make a d equal to the projection of the moulding : then proceed as directed for Fig. 142. 238. — Roman mouldings are composed of parts of circles, and have, therefore, less beauty of form than the Grecian. The bead and torus are of the form of the semi-circle, and the scotia, also, in some instances ; but the latter is often composed of two quaxi- rants, having different radii, as at Fig. 1 46 and 147, which re- semble the elliptical curve. The ovolo and cavetto are generally a quadrant, but often less. When they are less, as at Fig. 150, the centre is found thus : join the extremities, a and 6, and bisect ahin c ; from c, and at right angles to a b, draw c d^ cutting a level line drawn from a in d ; then d will be the centre. This moulding projects less than its height. When the projection is more than the height, as at Fig. 152, extend the line from c until Fig. 146. b\s. 14' n Fif. 148. Rf. 14». 116 AMERICAN HOUSE-CARPENTER. Fig. 151. d K :>^ a Fig. 152. Fig. 153. r J : Fig. 154. Fig. 155. rig. 190. Fif. urr MOULDINGS, CORNICES, &C. 117 Fig. 158. Fig. 159. fig. 160. it cuts a perpendicular drawn from a, as at d; and that will be the centre of the curve. In a similar manner, the centres are found for the mouldings ait Fig. 147, 151, 153, 156, 157, 158 and 159. The centres for the curves at Fig. 160 and 161, are found thus : bisect the line, a 6, at c ; upon a, c and b, successively, with a c 01 c b for radius, describe arcs intersecting at d and d ; then those intersections will be the centres. 239. — Fig. 162 to 169 represent mouldings of modern inven- tion. They have been quite extensively and successfully used in inside finishing. Fig. 162 is appropriate for a bed-moulding under a low, projecting shelf, and is frequently used under man- tle-shelves. The tangent, i h, is found thus : bisect the line, a 6, at c, and b c aX d; from d, draw d e, at right angles to e b ; from b, draw b /, parallel to e d ; upon b, with b d for radius, describe the arc, df; divide this arc into 7 equal parts, and set one of the parts from 5, the limit of the projection, to o ; make o h equal to e; from A, through c, draw the tangent, hi; divide b h, h c,ci and i a, each into a like number of equal parts, and draw the in- 118 AMERICAN HOUSE-CARPENTER. Fig. 162. Far 163, Fig. 164. MOULDINGS, CORNICES, &C. 119 Fiff. 165. Fig. 166. Fig 167. Fig. 168, Fig. 169 tersecting lines as directed at Art. 89. If a bolder form is desired, draw the tangent, i A, nearer horizontal, and describe an elliptic curve as shown in Fig. 131, 164, 175 and 176. Fig. 163 is much used on base, or skirting of rooms, and in deep panelling. The curve is found in the same manner as that of Fig. 162. In this case, however, where the moulding has so little projection 120 AMERICAN HOUSE-CARPENTER. in comparison with its height, the point, c, being found as in the last figure, h s may be made equal to s e, instead of o e as in the last figure. Fig. 164. is appropriate for a crown moulding of a cornice. In this figure the height and projection are given ; the direction of the diameter, a 6, drawn through the middle of the diagonal, e /, is taken at pleasure ; and d cis parallel to a e. To find the length of d c, draw b h, at right angles to a b ; upon 0, with o f for radius, describe the arc,/ h, cutting b h in h ; then make o c and o d, each equal to b h* To draw the curve, see note to A?^t. 118. Fig. 165 to 169 are peculiarly distinct from ancient mouldings, being composed principally of straight lines ; the few curves they possess are quite short and quick. H. P. 5 15 125^1 2i 11 9l0i' 10 J Fig. 170. H. P. U 15 Hi 14i 13 iU lU lO.j 10 I Fig. 171. 240.— K^. 170 and 171 are designs for antse caps. The * The manner of ascertaining the length of the conjugate diameter, dc/m this figure, and also in Fig. 131, 175 and 176, is new, and is important in tliis application. Ic is founded upon well-known mathematical principles, viz : All the parallelograms that may- be circumscribed about an ellipsis are equal to one another, and consequeudy any one is equal to the rectangle of the two axes. And again : the sum of the squares of every psdr of conjugate diameters is equal to the sum of the squares of the two axes. MOULDINGS, CORNICES, &C. 121 diameter of the antse is divided into 20 equal parts, and the height and projection of the members, are regulated in accordance with those parts, as denoted under ^Tand P, height and projection. The projection is measured from the middle of the antas. These will be found appropriate for porticos, door- ways, mantle-pieces, door and window trimmings, :it*<5sure will be entirely removed, if the bearings of the rafters, as A, Bj {Fig. 195,) are made horizontal — provided, however, that the rafters and other framing do not bend between the points of support. If a beam or rafter have a natural curve, the convex or rounding edge should be laid uppermost. 259. — A beam laid horizoptaPy supported at each end and uniformly loaded, is subjec* to tJi«' greatest strain at the middle 142 AMERICAN HOUSE-CARPENTER. of its length. The amount of pressure at that point is equal to half of the whole load sustained. The greatest strain coming upon the middle of such a beam, mortices, large knots and othei defects, should be kept as far as possible from that point ; and, in resting a load upon a beam, as a partition upon a floor beam, the weight should be so adjusted that it will bear at or near the ends. (See Art. 282.) 260. — The resistance of tvtnher. When the stress that a given load exerts in any particular direction, has been ascertain- ed, before the proper size of the timber can be determined for the resistance of that pressure, the strength of the kind of timber to be used must be known. The following rules for calculating the resistance of timber, are based upon the supposition that the tim- ber used be of what is called " merchantable" quality — that is. strait-grained, seasoned, and free from large knots, splits, decay, &c. Fig. 196. Fig. 197 Fig. 198. The strength of a })iece of timber, is to be considered in ac* cordance witti the direction in which the strain is applied upon FRAMING. 143 it. When it is compressed in the direction of its length, as in Fig. 196j its strength is termed the resistance to compression. When the force tends to pull it asunder in the direction of its length, (^, Fig. 197",) it is termed the resistance to tension. And when strained by a force tending to break it crosswise, as at Fig. 198, its strength is called the resistance to cross strains. 261. — Resistance to compression. When the height of a piece of timber exceeds about 10 times its diameter if round, or 10 times its thickness if rectangular, it will bend before crushing. The first of the following cases, therefore, refers to such posts as would be crushed if overloaded, and the other two to such as would hend before crushing. In estimating the strength of tim- ber for this kind of resistance, it is provided in the following rules that the pressure be exactly in a line v^^ith the axis of the post. Case 1. — To find the area of a post that will safely bear a given weight — when the height of the post is less than 10 times its least thickness. Ride. — Divide the given weight in pounds by 1000 for pine and 1400 for oak, and the quotient will be the least area of the post in inches. This rule requires that the area of the abutting surface be equal to the result : should there be, there- fore, a tenon on the end of the post, this quotient will be too small. Example. — What should be the least area of a pine post that will safely sustain 48,000 pounds ? 48,000, divided by 1000, gives 48 — the required area in inches. Such a post may be 6x8 inches, and will bear to be of any length within 10 times 6 inches, its least thickness. Case 2. — To find the area of a rectangular post that will safely bear a given weight — when its height is 10 times its least thickness or more. Rule. — Multiply the given weight or pres- sure in pounds by the square of the length in feet ; and multi- ply this product by the decimal, '0015, for oak, '0021, for pitch pine and '0016 for white pine ; then divide this product by the breadth in inches, and the cube-root of the quotient will be the 144 AMERICAN HOUSE-CARPENTER. thickness in inches. Example. — What should be the thickness of a pine post, 8 feet high and 8 inches wide, in order to support a weight of 12 tons, or 26,880 pounds ? The square of the length is 64 feet; this, multiplied by the weight in pounds, gives 1,730,320; this product, multiplied by the decimal, '0016, gives 2768-512 ; and this again, divided by the breadth in inches, gives 346-064 ; by reference to the table of cube-roots in the appendix, the cube-root of this number will be found to be 7 inches large^ — which is the thickness required. The stiffest rectangular post is that in which the sides are as 10 to 6. Case 3.— To find the area of a row?ic?, or cylindrical, post, that will safely hear a given weight — when its height is 10 times its least diameter or more. Rule. — Multiply the given weight or pressure in pounds by 1*7, and the product by -0015 for oak, -0021 for j)itch pine and '0016 for white pine ; then multiply the square- root of this product by the height in feet, and the square-root of the last product will be the diameter required, in inches. Exam- ple. — What should be the diameter of a cylindrical oak post, 8 feet high, in order to support a weight of 12 tons, or 26,880 pounds ? This weight in pounds, multiplied by 1*7, gives 45,696 ; and this, by '0015, gives 68-544 ; the square-root of this product is (by the table in the appendix) 8*28, nearly — which, multiplied by 8, gives 66*24 ; the square-root of this number is 8*14, nearly ; therefore, 8-14 inches is the diameter required. Experiments have shown that the pressure should never be more than 1000 pounds per square inch on a joint in yellow pine — when the end of the grain of one piece is pressed against the side of the grain of the other. 262. — Resistance to tension. A bar of oak of an inch square, pulled in the direction of its length, has been torn asunder by a weight of ... - 11,500 lbs. Of white pine - - - 11,000 Of pitch pine - - - 10,000 FRAMING. 145 Therefore, when the strain is applied in a line with the axis of the piece, the following rule must be observed. To find the area of a piece of timber to resist a given strain in the direction of its length. Rule. — Divide the given weight to be sustained, by the weight that will tear asunder a bar an inch square of the same kind of wood, (as above.) and the product will be the area in inches of a piece that will just sustain the given weight ; but the area should be at least 4 times this, to safely sustain a constant load of the given weight. Example. — What should be the area of a stick of pitch pine timber, which is re- quired to sustain safely a constant load of 60,000 pounds ? 60,000, divided by 10,000, (as above,) gives 6, and this, multiplied by 4, give 24 inches— the answer. 263. — Resistance to cross strains. To find the scantling of a piece of timber to sustain a given weight, when such piece is supported at the ends in a horizontal position. Case 1. — When the breadth is given. Rule. — Multiply the square of the length in feet by the weight in pounds, and this product by the decimal, '009, for oak, 'Oil for white pine and '016 for pitch pine ; divide the product by the breadth in inches, and the cube-root of the quotient will be the depth required in inches. Example. — What should be the depth of a beam of white pine^ having a bearing of 24 feet and a breadth of 6 inches, in order to support 900 pounds ? The square of 24 is 576, and this, multiplied by 900, gives 518-400; and this again, by -Oil, gives 5702-400 ; this, divided by 6, gives 950*400 ; the cube-root of which is 9*83 inches — the depth required. Case 2. — When the depth is given. Rule. — Multiply the square of the length in feet by the weight in pounds, and multi- ply this product by the decimal, -009, for oak, -Oil for white pine and '016 for pitch pine ; divide the last product by the cube of the depth in inches, and the quotient will be the breadth in inches required. Exarnple. — What should be the breadth of a beam of oak, having a bearing of 1 6 feet and a depth of 12 inches, in 19 146 AMERICAN HOUSE-CARPENTER. order to support a weight of 4000 pounds? The square of 16 is 256, which, multiplied by 4000, gives 1,024,000 ; this, multiplied by '009, gives 9216 ; and this again, divided by 1728, the cube of 12, gives 5-g inches — which is the breadth required. Case 3. — When the breadth bears a certain proportion to the depth. When neither the breadth nor depth is given, it will be best to fix on some proportion which the breadth should have to the depth ; for instance, suppose it be convenient to make the breadth to the depth as 0*6 is to 1, then the rule would become as follows : Rule. — Multiply the weight in pounds by the decimal, •009, for oak, 'Oil for white pine and '016 for pitch pine; divide the product by 0*6, and extract the square-root ; multiply this root by the length in feet, and extract the square-root a second time, v/hich will be the depth in inches required. The breadth is equal to the depth multiplied by the decimal, 0*6. It is obvious that any other proportion of tiie breadth and depth may be ob- tained by merely changing the decimal, 0'6, in the rule. Exam- ple. — What should be the depth and breadth of a beam of pitch pine, having a proportion to one another as 06 to 1, and a bearing of 22 feet, in order to sustain a ton weight, or 2240 pounds !■ This, multiplied by '016, gives 35*84, which, divided by 0-G, gives 59'73 ; the square-root of this is 7'7, which, multiplied by 22, the length, gives 169*4 ; the square-root of this is 13 — which is the depth required. Then 13, multiplied by 0'6, gives 7*8 inches — the required breadth. Case 4. — When the beam is inclined, as A B, Fig. 193. Rule. — Multiply together the weight in pounds, the length of the beam in feet, the horizontal distance, A c. between the supports, in feet, and the decimal, '0095 for oak, -Oil for white pine, and •016 for pitch pine ; divide this product by 0*6, and the fourth root of the quotient will give the depth in inches. The breadth is equal to the depth multiplied by the decimal, 0*6. Example. — What should be the size of an oak beam, the sides to bear a pro- portion to ci.e another as 0*6 to 1, in order to support a ton weight FRAMING. 147 or 2240 pounds, the beam being inclined so that, its length being 20 feet, its horizontal distance between the points of support will be 16 feet? 2240, multiplied by 20, gives 44,800, which, multi- plied by 16, gives 716,800 ; and this again, by the decimal, -009, gives 6451-2 ; this last, divided by 0-6, gives 10,752, the fourth root of which is 1018, nearly ; and this, multiplied by 0*6, gives 6*1 ; therefore, the size of the beam should be 10*18 inches by 6-1 inches. Fig. 199. 264. — To ascertain the scantling of the stiffest beam that can he cut from a cj/linder. Let d a c b, [Fig- 199,) be the sec- tion, and e the centre, of a given cylinder. Draw the diameter, a b ; upon a and 6, with the radius of the section, describe the arcs, d e and e c ; join d and «, a and c, c and h. and h and d ; then the rectangle, d a cb^ will be a section of the beam required. 265. — The greater the depth of a beam in proportion to the thickness, the greater the strength. But when the difference be- tween the depth and the breadth is great, the beam must be stayed, (as at Fig. 202,) to prevent its falling over and breaking sideways. Their shrinking is another objection to deep beams ; but where these evils can be remedied, the advantage of increas- ing the depth is considerable. The following rule is, to find the strongest form for a beam out of a given quantity of timber. Rule. — Multiply the length in feet by the decimal, 0*6, and divide the given area in inches by the product ; and the square of the quotient will give the depth in inches. Example. — What is the strongest form for a beam whose given area of section is 48 148 AMERICAN HOUSE-CARPENTER. ii'icheSj and length of bearing 20 feet ? The length m feet, 20. multiplied by the decimal, 0*6, gives 12; the given area in inches, 48, divided by 12, gives a quotient of 4, the square of which is 16 — this is the depth in inches ; and the breadth must be c inches. A beam 1(3 inches by 3 would bear twice as much as a square beam of the same area of section; which shows how im- portant it is to make beams deep and thin. In many old build- in[;s, and even in new ones, in country places, the very reverse of this has been practised ; the principal beams being oftener laid on the broad side than on the narrower one. 266. — Systems of Framing. In the various parts of framing known as floors, partitions, roofs, bridges, &c., each has a specific object ; and, in all designs for such constructions, this object should be kept clearly in view ; the various parts being so dis- posed as to serve the design with the least quantity of material. The simplest form is the best, not only because it is the most economical, but for many other reasons. The great number of joints, in a complex design, render the construction liable to de- rangement by multiplied compressions, shrinkage, and, in conse- quence, highly increased oblique strains ; by which its stability and durability are greatly lessened. FLOORS. 267. — Floors have been constructed in various ways, and are known as smgle-joisted, double., and framed. In a single- joisted floor, the timbers, or fioor-joists, are disposed as is shown in Fig. 200. Where strength is the principal object, this manner of disposing the fioor-joists is far preferable ; as experiments have proved that, with the same quantity of material, single-joisted floors are much stronger than either double or framed floors. To obtain the greatest strength, the joists should be thin and deep. 268. — To find the depth of a joist, the length of hearing and thickness being given, when the distance from centres is FRAMING. 149 Fig. 20a 12 inches. Rule. — Divide the square of the length in feet, by the breadth in inches ; and the cube-root of the quotient, multi- pUed by 2-2 for pine, or 2*3 for oak, will give the depth in inches. Example. — What should be the depth of floor-joists, having a bearing of 12 feet and a thickness of 3 inches, when said joists are of pine and placed 12 inches from centres ? The square of 12 is 144, which, divided by 3, gives 48 ; the cube-root of this number is 3*63, which, multiplied by 2-2, gives 7*986 inches, the depth required ; or 8 inches will be found near enough for practice. 269. — Where chimneys, flues, stairs, , are halved, and nailed to the tie, c d, and the sill, ef. The braces in a trussed partition should be placed, so as to form, as near as possible, an angle of 40 degrees with the horizon. In partitions that are intended to support only their own weight, the principal timbers may be 3x4 inches for a 20 feet span, 3ix5 for 30 feet, and 4x6 for 40. The thickness of the fiUing-in stuff may be regulated according to what is said at Art. 271, in regard to the width of furring for plastering. The FRAMING. 159 filling-in pieces should be stiffened at about every three feec by- short struts between. All superfluous timber, besides being an unnecessary load upon the points of support, tends to injure the stability of the plaster- ing ; for, as the strength of the plastering depends, in a great mea- sure, upon its clinch, formed by pressing the mortar through the space between the laths, the narrower the surface, therefore, upon which the laths are nailed, the less will be the quantity of plas- tering unclinched, and hence its greater security from fractures. For this reason, the principal timbers of the partition should have their edges reduced, by chamfering off the corners. cr (^ '/ ■/ K ^ di El ^ !^ feJ Fiff. 2U8. 283. — When the principal timbers of a partition require to be large for the purpose of greater strength, it is a good plan to omit the upright filling-in pieces, and in their stead, to place a few hori- zontal pieces ; in order, upon these and the principal timbers, to nail upright battens at the pi-oper distances for lathing, as in Fig. :208. A partition thus constructed requires a little more space than others ; but it has the advantage of insuring greater stability to the plastering, and also of preventing to a good degree the con- versation of one room from being heard in the other. When a partition is required to support, in addition to its own weight, that of a floor or some other burden resting upon it, the dimensionK. oi 160 AMERICAN HOUSE-CARPENTER. the timbers ma^ be ascertained, by applying the principles which regulate the laws of pressure and those of the resistance of tim- ber, as explained at the lirst part of this section. The following data, however, may assist in calculating the amount of pressure upon partitions: 284.— The weight of a square, (tliat is, a hundred square feet,) of partitioning maybe estimated at from 1500 to 2000 lbs.; a square of single-joisted flooring, at from 1200 to 2000 lbs. ; a square of framed flooring, at from 2700 to 4500 lbs.: and the weight of a square of deafenings (as described at the latter part of Art. 271,) at about 1500 lbs. When a floor is supported at two opposite extremiti(?s, and by a partition introduced midway, one-half of the weight of the whole floor will then be supported by the partition. As the settling of partitions and floors, which is so disastrous to plastering, is fre- quently owing to the shrinking of the timber and to ill-made joints, it is very important that the timber be seasoned and the work well executed. ROOFS.* 285. — In ancient buildings, the Norman and the Gothic, the walls and buttresses were erected so massive and firm, that it was customary to construct their roofs without a tie-beam; the walls being abundantly capable of resisting the lateral pressure exerted by the rafters. But in modern buildings, the walls are so slightly built as to be incapable of resisting scarcely any oblique pressure ; and hence the necessity of constructing the roof so that all oblique and lateral strains may be removed; as, also, that instead of having a tendency to separate the walls, the roof may contri- bute to bind and steady them. 286. — In estimating the pressures upon any certain roof, for the purpose of ascertaining the proper sizes for the timbers, calcula- tion must be made for the pressure exerted by the wind, and, if * See also Art. 228. FRAMING. 161 in a cold climatej for the weight of snow, in addition to the weight of the materials of which the roof is composed. The force of wind may be calculated at 40 lbs. on a square foot. The weight of snow will be of course according to the depth it acquires. {See weio-Jit of materials, in Appendix.) In a severe climate, roofs ought to be constructed steeper than in a milder one ; in order that the snow may have a tendency to slide off before it becomes of sufficient weight to endanger the safety of the roof. The inclina- tion should be regulated in accordance with the qualities of the material with which the roof is to be covered. The following table may be useful in determining the inclination, and in estimating the weight of the various kinds of covering : MATERIAL. INCLINATION. WEIGHT UPON A SQUARE FOOT. Tin, Rise 1 inch to a foot. f to l\ lbs. Copper, ;; 1 " 1 to 1^ " Lead, " 2 inches ** 4 to 7 " Zinc, '• 3 " " li to 2 " Short pine shingles, '• 5 " " lito2^ " Loner cypress shingles. a Q u 4 to 5 " Slate, u (3 u a 5 to 9 " The weight of the covering, as above estimated, is that of the material only, added to the weight of whatever is used to fix it to the roof, such as nails, 196, which, multi- plied by 38, gives 74 18 ; this, divided by 216, the cube of 6, gives FRAMING. 165 34 IS, which, multiplied by 0-155, gives 5*34. The size of the rafter should, therefore, be 6x5|. 294. — To find the dimensions of a straining-beam. In or der that this beam may be the strongest possible, its depth should be to its thickness as 10 is to 7. Rule. — Multiply the square-root of the span in feet^ by the length of the straining-beam in feet, and extract the sqi^ere-root of the product. Multiply this root by ()'9 for pine, which will give the depth in inches To find the thickness, multiply the depth by the decimal, 0"7. Example. — What should be the dimensions of a pine straining-beam, 12 feet long, for a span of 38 feet ? The square-root of the span is 6*164, which, multiplied by 12, gives 73*968 ; the square-root of this is nearly 8*60, which, multiplied by 0*9, gives 7*74 — the depth. This, multiplied by 0*7, gives 5*418 — the thickness. Therefore, the beam should be 5|x7|, or 5|x8. 295. — To find the dim^ensions of stmts and braces. Rule. — Multiply the square-root of the length supported in feet, by the length of the brace or strut in feet ; and the square-root of the product, multiplied by 0*8 for pine, will give the depth in inches ; and the depth, multiplied by the decimal, 0*6, will give the thick- ness in inches. Example. — In Fig. 210, the part supported by the brace or strut, a, is equal to half the length of the principal rafter, or 7 feet ; and the length of the brace is 6 feet : what should be the size of a pine brace ? The square-root of 7 is 2*65, which, multiplied by 6, gives 15-9 ; the square-root of this is 3'99, which, multiplied by 0*8, gives 3*192 — the depth. This, multi- plied by 0*6, gives 1*9152, the thickness. Therefore, the brace should be 2x3 inches. It is customary to make the principal rafters, tie-beam, posts and braces, all of the same thickness, that the whole truss may be of the same thickness throughout. 296. — To find the dim,ensions of purlins. Rule. — Multiply the cube of the length of the purlin in feet, by the distance the purlins are apart in feet ; and the fourth root of the product for pine will give the depth in inches ; or multiply by 1*04 to obtain 166 AMERICAN HOUSE-CARPENTER. the depth for oak ; and the depth, multiplied by the decimal, 0*6, will give the thickness. Example. — What should be the dimen- sions of pine purlins, 9 feet long and 6 feet apart ? The cube of 9 is 729, which, multiplied by 6, gives 4374; the fourth root of this is 8-13 — the required depth. This, multiplied by 0-6, gives 4*87S — the thickness. A proper size for them would be about 5x8 inches. Purlins should be long enough to extend over two, three or more trusses. 297. — To find the dbnensions of co9nmon rafters. The fol- lowing rule is for slate roofs, having the rafters placed 12 inches apart. Shingle roofs may have rafters placed 2 feet apart. The dimensions of rafters for other kinds of covering may be found by reference to the table at Art. 286. and the laws of pressure at the first part of this section. Rule. — Divide the length of bearing in feet, by the cube-root of the breadth in inches ; and the quotient, multiplied by 0-72 for pine, or 0'74 for oak, will give the depth in inches. Exaiiiple. — What should be the depth of a pine rafter, 7 feet long and 2 inches thick ? 7 feet, divided by 1*26, the cube- foot of 2, gives 5*55, which, multiplied by 0'72, gives nearly 4 inches — the depth required. 298. — If, instead of framing the principal rafters and straining- beam into the king ;md the queen posts, they be permitted to abut against each other, and the king and the queen posts be made in halves, notched on and bolted, or strapped to each other and to the tie-beam, much of the ill effects of shrinking in the heads of the king and the queen posts will be avoided. (See Art. 339 and 340.) FRAMING. 167 299. — Fig. 213 shows a method of constructing a truss having a huilt-rih in the place of principal rafters. The proper form for the curve is that of a parabola, {Art. 127.) This curve, when as flat as is described in the figure, approximates so near to that of the circle, that the latter may be used in its stead. The height, a 6, is just half of a c, the curve to pass through the middle of the rib. The rib is composed of two series of abutting pieces, bolted together. These pieces should be as long as the dimen- sions of the timber will admit, in order that there may be but few joints. The suspending pieces are in halves, notched and bolted to the tie-beam and rib, and a purlin is framed upon the upper end of each. A truss of this construction needs, for ordinary roofs, no diagonal braces between the suspending pieces, but if extra strength is required the braces may be added. The best place for the suspending pieces is at the joints of the rib. A rib of this kind will be sufliciently strong, if the area of its section contain about one-fourth more timber, than is required for that of a strain- ing-beam for a roof of the same size. The proportion of the depth to the thickness should be about as 10 is to 7. Fig. 214. 300. — Some writers have given designs for roofs similar to Fig. 214, having the tie-beam omitted for the accommodation of an arch in the ceiling. This and all similar designs are seriously objectionable, and should always be avoided ; as the small height gained by the omission of the tie-beam can never compensate for the powerful lateral strains, which are exerted by the oblique posi- tion of the supports, tending to separate the walls. Where an arch 168 AMERICAN HOUSE-CARPENTER. is required in the ceiling, the best plan is to carry up the walls as high as the top of the arch. Then, by using a horizontal tie- beam, the oblique strains will be entirely removed. Many a pub- lic building in this place and vicinity, has been all but ruined by the settling of the roof, consequent upon a defective plan in the formation of the truss in this respect. . It is very necessary, there- fore, that the horizontal tie-beam be used, except where the walls are made so strong and firm by abutments, or other support, as to prevent a possibility of their separating. FliT. 2iJ. 301. — Fig' 215 is a meihod of obtaining the proper lengths and bevils for rafters in a hip-roof, a b and b c are walls at the angle of the building : & e is the seat of the hip-rafter and g f of a. jack or cripple rafter. Draw e h, at right angles to b e, and make it equal to the rise of the roof; join b and h, and h b will be the length of the hip-rafter. Through e, draw d i, at right angles to 6 c; upon 6, with the radius, b A, describe the arc, h i, cutting d i'mi ; join b and i, and extend gf to meet biin j ; then gj will FRAMING. 169 be the length of the jack-rafter. The length of each jack-rafter is found in the same manner — by extending its seat to cut the line, b i. From/, draw fk, at right angles tofg, also//, at right angles to be; make/ A: equal to /Z by the arc, I k, or make g- k equal to gj by the arc, J k ; then the angle atj will be the top- bevil of the jack-rafters, and the one at k will be the down-bevil.^ 302. — To find the backing of the hip-rafter. At any con- venient place in b e, {Fig.. 215,) as o, draw m n^ at right angles to be; from o, tangical to b A, describe a semi-circle, cutting b e in 5 ; join ni and s and n and s ; then these lines will form at 5 the proper angle for beviling the top of the hip-rafter. DOMES.t Fig. 216. Fig. 217. ♦ The lengths and bevils of rafters for roof-valleys can also be found by the abov? process t See also Art. 227 22 170 AMERICAN HOUSE-CARPENTER. 303. — The most usual form for domes is that of the sphere, the base being circular. When the interior dome does not rise too high, a horizontal tie may be thrown across, by which any de- gree of strength required may be obtained. Fig. 216 shows a section, and Fig. 217 the plan, of a dome of this kind, a h being the tie-beam in both. Two trusses of this kind, [Fig. 216,) pa- rallel to each other, are to be placed one on each side of the open- ing in the top of the dome. Upon these the whole framework is to depend for support, and their strength must be calculated accord- ingly. (See the first part of this section, and Art. 286.) If the dome is large and of importance, two other trusses may be intro- duced at right angles to the foregoing, the tie-beams being pre- served in one continuous length by framing them high enough to pass over the others. Fiff. 918. Fig. 219. 304. — When the interior dome rises too high to admit of a level FRAMING. 171 tie-beam, the framing may be composed of a succession of ribs standing upon a continuous circular curb of timber, as seen at Fig. 218 and 219,— the latter being a plan and the former a sec- tion. This curb must be well secured, as it serves in the place of a tie-beam to resist the lateral thrust of the ribs. In small domes, these ribs may be easily cut from wide plank ; but, where an extensive structure is required, they must be built in two thicknesses so as to break joints, in the same manner as is descri- bed for a roof at Art. 299. They should be placed at about two feet apart at the base, and strutted as at a in Fig. 218. 305. — The scantling of each thickness of the rib may be as follows : For domes of 24 feet diameter, 1x8 inches. " '• 36 " lixlO " " ' 60 '' 2x13 " " " 90 " 2|xl3 " " " 108 " 3x13 " 306. — Although the outer and the inner surfaces of a dome may be finished to any curve tliat may be desired, yet the framing should be constructed of such a form, as to insure that the curve of eqiiilibriiun will pass through the middle of the depth of the framing. The nature of this curve is such that, if an arch or dome be constructed in accordance with it, no one part of the structure will be less capable than another of resisting the strains and pressures to whicli the v/hole fabric may be exposed. Tiie curve of equilibrium for an arched vault or a roof, where the load is equally diffused over the whole surface, is that of a parabola, [Art. 127' ;) for a dome, having no Icudern^ tower or cupola above it, a aihic parabola, {Fig. 220 ;) and for one having a tower, &c., above it, a curve approaching that of an hyperbola must be adopted, as the greatest strength is required at its upper parts. If the curve of a dome be circular, (as in the vertical section. Fig. 218,) ihe pressure will have a tendency to burst the dome outwards at -bout one-third of its height. Therefore, when this form is used 172 AMERICAN HOUSE-CARPENTER. in the construction of an extensive dome, an iron band should be placed around the framework at that height ; and whatever may- be the form of the curve, a band or tie of some kind is necessary around or across the base. If the framing be of a form less convex than the curve of equilibrium, the weight will have a tendency to crush the ribs in- wards, but this pressure may be effectually overcome by strutting between the ribs ; and hence it is important that the struts be so placed as to form continuous horizontal circles. ^ / / J / Oj / / A a j I h uo. 307. — To describe a cubic parabola. Let a b, {Fig. 220,) be the base and b c the height. Bisect a b at d, and divide a d into 100 equal parts; of these give d e 26, ef lSi,f g 14|, g h 12^, h i lOf, ij 9i, and the balance, 8|, to ; a; divide b c into 8 equcil parts, and, from the points of division, draw lines parallel to a 6, to meet perpendiculars from the several points of division in a b, at the points, o, o, o, ifcc. Then a curve traced through these points will be the one required. 308.— Small domes to light stairways, &c., are frequently made elliptical in both plan and section ; and as no two of the ribs in one quarter of the dome are alike in form, a method for obtaining the curves is necessary. 309.— To find the curves for the ribs of an elliptical dome. Let a 6 c d, [Fig. 221,) be the plan ot a dome, and e f the seat FRAMING. 173 Fig. 2-1 of one of the ribs. Then take e f for the transverse axis and twice the rise, o g, of the dome for the conjugate, and describe, (according to Art. 115, 116, &c.,) the semi-ellipse, e g f, which will be the curve required for the rib, e g f. The other ribs are found in the same manner. b 4 Fig. 222. 310. — To find the shape of the covering for a spherical dome. Let A, (Fig. 222,) be the plan and B the section of a given dome. From a, draw a c, at right angles to a b ; find the stretch-out, {Art, 92,) of o b, and make d c equal to it ; divide the arc, 6, and the line, d c, each into a like number of equal parts, 174 AMERICAN HOUSE-CARPENTER. as 5, (a large number will insure greater accuracy than a small one ;) uponc, through the several points of division in c d^ describe the arcs, o c? o, 1 e 1, 2/ 2, &c. ; make d o equal to half the width of one of the boards, and draw o s, parallel to a c ; join s and a, and from the points of division in the arc, o b, drop perpendicu- lars, meeting a 5 in ij k I ; from these points, draw i 4, j 3, (fee, parallel to a c; make d o, e l,&c., on the lower side of a c, equal to d 0, e 1, &c., on the upper side ; trace a curve through the points, 0, 1, 2, 3, 4, c, on each side o{ d c ; then o c o will be the proper shape for the board. By dividing the circumference of the base. A, into equal parts, and making the bottom, o d o,o{ the board of a size equal to one of those parts, every board may be made of the same size. In the same manner as the above, the shape of the covering for sections of another form may be found, such as an ogee, cove, &c. 311. — Tojiiid the ciirve of the hoards when laid in horizon- tal cottrses. Let ABC, {Fig. 223,) be the section of a given dome, and D B its axis. Divide B C into as many parts as there are to be courses of boards, in the points, 1, 2, 3, Sec. ; through 1 and 2, draw a line to meet the axis extended at a ; then a will be the centre for describing the edges of the board, F. Through 3 and 2, draw 36; then b will be the centre for describing F. Through 4 and 3, draw Ad; then d will be the centre for G B is the centre for the arc, 1 o. If this method is taken to find FRAMING. 175 the centres for the boards at the base of the dome, they would occur so distant as to make it impracticable : the following method is preferable for this purpose. G being the last board obtained by the above method, extend the curve of its inner edge until it meets the axis, D B, in e ; from 3, through e, draw 3 /, meeting the arc, A B, in/; join /and 4, /and 5 and/ and 6, cutting the axis, D B, in s, n and ?n ; from 4, 5 and 6, draw lines parallel to A Cand cutting the axis in c, p and r; make c 4, {Fig, 224,) equal to c 4 in the preyious figure, and c s equal to c 5 also in the previous figure ; then describe the inner edge of the board, H^ according to Art. 87 : the outer edge can be obtained by gauging from the inner edge. In like manner proceed to obtain the next board — taking p .5 for half the chord and p n for the height of the segment. Should the segment be too large to be described easily, reduce it by finding intermediate points in the curve, as at Art. 86. 312. — To find the shape of the angle-rib for a polygonal dome. Let AG H^ {Fig. 225,) be the plan of a given dome, and 176 AMERICAN HOUSE-CARPENTER. O Z> a vertical section taken at the line, e f. From 1, 2, 3, (fee, in the arc, C JD, draw ordinates, parallel to A Z>, to meet/ G ; from the points of intersection on / G^ draw ordinates at right- angles to/ G ; make s 1 equal to o 1, 5 2 equal to 2, &c. ; ^hen GfB^ obtained in this way, will be the angle-rib required. The best position for the sheathing-boards for a dome of this kind is horizontal, but if they are required to be bent from the base to the vertex, their shape may be found in a similar manner to that shown at Fig. 222. BRIDGES. 313. — Yarious plans have been adopted for the construction of bridges, of which perhaps the following are the most useful. Fig. 22G shows a method of constructing wooden bridges, where the banks of the river are higli enough to permit the use of the tie-beam, a b. The upright pieces, c (/, are notched and bolted on ni pairs, for the support of the tie-beam. A bridge of this construction exerts no lateral pressure upon the abutments. This method maybe employed even where the banks of the river are low, by letting the timbers for the roadway rest immediately upon the tie-beam. In this case, the framework above will serve the purpose of a railing. Fig. 226. 314. — Fig. 227 exhibits a wooden bridge without a tie-beam. Where staunch buttresses can be obtained, this method may be recommended ; but if there is any doubt of their stability, it FRAMING. 177 Fig. 227. should not be attempted, as it is evident that such a system of framing is capable of a tremendous lateral thrust. Fig. 22a 315. — Fig. 228 represents a wooden bridge in which a built-rib, (see Art. 299,) is introduced as a chief support. The curve of equilibrium will not differ much from that of a parabola : this, therefore, may be used — especially if the rib is made gradually a little stronger as it approaches the buttresses. As it is desirable that a bridge be kept low, the following table is given to show the least rise that may be given to the rib. Span in feet. Least rise in feet. Span in feet Least rise in feet. 7 1 Span in feet. Least rise in feet. 30 0-5 120 280 24 40 0-8 140 8 300 28 50 1-4 160 10 320 32 60 2 180 11 350 39 70 2i 200 12 380 47 80 3 220 14 400 53 90 4 240 17 100 5 260 20 The rise should never be made less than this, but in all cases 23 L78 AMERICAN HOUSE-CARPENTER. greater if practicable ; as a small rise requires a greater quantity of timber to make the bridge equally strong. The greatest uni- form weight with which a bridge is likely to be loaded is, proba- bly, that of a dense crowd of people. This may be estimated at 120 pounds per square foot, and the framing and gravelled road- way at 180 pounds more ; which amounts to 300 pounds on a square foot. The following rule, based upon this estimate, may be useful in determining the area of the ribs. Rule. — Multiply the width of the bridge by the square of half the span, both in feet ; and divide this product by the rise in feet, multiplied by the number of ribs ; the quotient, multiplied by the decimal, O'OOll, will give the area of each rib in feet. When the road- way is only planked, use the decimal, 0*0007, instead ot O'OOll. Example. — What should be the area of the ribs for a bridge of 200 feet span, to rise 15 feet, and be 30 feet wide, with 3 curved ribs ? The half of the span is 100 and its square is 10,000 ; this, multiplied by 30, gives 300,000, and 15, multi- plied by 3, gives 45 ; then 300,000, divided by 45, gives 6666f , which, multiplied by 0-0011, gives 7*333 feet, or 1056 inches for the area of each rib. Such a rib may be 24 inches thick by 44 inches deep, and composed of 6 pieces, 2 in width and 3 in depth. Fig. 229. 316. — The above rule gives the area of a rib, that would be re- quisite to support the greatest possible uniform load. But in large bridges, a variable load, such as a heavy wagon, is capable of exerting much greater strains ; in such cases, therefore, the rib should be made larger. The greatest concentrated load a FRAMING. 179 bridge will be likely to encounter, may be estimated at from about 20 to 50 thousand pounds, according to the size of the bridge. This is capable of exerting the greatest strain, when placed at about one-third of the span from one of the abutments, as at b. {Fig. 229.) The weakest point of the segment, b g- c, is at g^ the most distant point from the chord line. The pressure exerted at b by the above weigl^t, may be considered to be in the direction of the chord lines, b a and be; then, by constructing the paral- lelogram of forces, e b f d, according to Art. 248, b f will show the pressure in the direction, b c. Then the scantling for the rib may be found by the following rule. Rule. — Multiply the pressure in pounds in the direction, b c. by the decimal, 0*0016, for white pine, 0*0021 for pitch pine, and 0'0015 for oak, and the product by the decimal representing the sine of the angle, g b h, to a radius of unity. Divide this pro- duct by the united breadth in inches of the several ribs, and the cube-root of the quotient, multiplied by the distance, b c, in feet. will give the depth of the rib. Example. — In a bridge of 200 feet span, 15 feet rise, having 3 ribs each 24 inches thick, or 72 inches whole thickness, the pressure in the direction, 6 c, is found to be 166,000 lbs., and the sine of the angle, g b h, is 0*1 — what should be the depth of the rib for white pine? 166,000, mul- tiplied by 0-0016, gives 265*6, which, multiplied by 0*1, gives 26-56 ; this, divided by 72, gives 0-3689. The cube-root of the last sum is 0-717 nearly, and the distance, b c, is 135 feet : then, 0-'^ 17, multiplied by 135, gives 96f inches, the depth required. By this, each rib will require to be 24x97 inches, in order to en- counter without injury the greatest possible load. 317. — In constructing these ribs, if the span be not over 50 feet, each rib may be made in two or three thicknesses of timber, (three thicknesses is preferable,) of convenient lengths bolted together ; but, in larger spems, where the rib will be such as to render it difficult to procure timber of sufficient breadth, they may be constructed by bending the pieces to the proper curv€^ )80 AMERICAN HOUSE-CARPENTER. and bolting them together. In this case, where timber of suffi- cient length to span the opening cannot be obtained, and scarfing is necessary, such joints must be made as will resist both tension and compression, (see Fig. 238.) To ascertain the greatest depth for the pieces which compose the rib, so that the process of bend- ing may not injure their elasticity, multiply the radius of curvature in feet by the decimal, 0*05, and the product will be the depth m inches. Example. — Suppose the curve of the rib to be described with a radius of 100 feet, then what should be the depth ? The radius in feet, 100, multiplied by 0*05, gives a product of 5 inches. White pine or oak timber, 5 inches thick, would freely bend to the above curve ; and, if the required depth of such a rib be 2( inches, it would have to be composed of at least 4 pieces. Pitch pine is not quite so elastic as white pine or oak — its thickness may be found by using the decimal, 0*046, instead of 0'05. Fig. 230. 318. — When the span is over 250 feet, ?l framed rib, formed as in Fig. 230, would be preferable to the foregoing. Of this, the upper and the lower edges are formed as just described, by bend- ing the timber to the proper curve. The pieces that tend to the centre of the curve, called radials^ are notched and bolted on in pairs, and the cross-braces are halved together in the middle, and abut end to end between the radials. The distance between the ribs of a bridge should not exceed about 8 feet. The roadway FRAMING. 18i should be supported by vertical standards bolted to the ribs at about every 10 to 15 feet. At the place where they rest on the ribs, a double, horizontal tie should be notched and bolted on the back of the ribs, and also another on the under side ; and diago- na' braces should be framed between the standards, over the space between the ribs, to prevent lateral motion. The timbers for the roadway may be as light as their situation will admit, as all use- less timber is only an unnecessary load upon the arch. 319. — It is found that if a roadway be 18 feet wide, two car- riages can pass one another without inconvenience. Its width, therefore, should be either 9, 18, 27 or 36 feet, according to the amount of travel. The width of the foot-path should be 2 feet for every person. When a stream of water has a rapid current, as few piers as practicable should be allowed to obstruct its course ; otherwise the bridge will be liable to be swept away by freshets. When the span is not over 300 feet, and the banks of the river are of sufficient height to admit of it, only one arch should be employed. The rise of the arch is limited by the form of the roadway, and by the height of the banks of the river (See Art. 315.) The rise of the roadway should not exceed one in 24 feet, but, as the framing settles about one in 72, the roadway should be framed to rise one in 18, that it may be one in 24 after settling. The commencement of the arch at the abutments — the springs as it is termed, should not be below high-water mark : and the bridge should be placed at right angles with the course of the current. 320. — The best material for the abutments and piers of a bridge, is stone ; and, if possible, stone should be procured for the purpose. The following rule is to determine the extent of the abutments, they being rectangular, and built with stone weighing 120 lbs. to a cubic-foot. Rule. — Multiply the square of the height of the abutment by 160, and divide this product by the weight of a square foot of the arch, and by the rise of the arch ; add unity to the quotient, and extract the square-root. Diminish the square-root by unity, and multiply the root, so diminished, by AMERICAN HOUSE-CARPENTER. half the span of the arch, and by the weight of a square-foot ot the arch. Divide the last product by 120 times the height of the abutment, and the quotient will be the thickness of the abutment. Exain'ple. — Let the height of the abutment from the base to the springing of the arch be 20 feet, half the span 100 feet, the weight of a square foot of the arch, including the greatest possible load upon it, 300 pounds, and the rise of the arch 18 feet — what should be its thickness ? The square of the height of the abutment, 400, multiplied by 100, gives 64,000, and 300 by 18, gives 5400 ; 64,000, divided by .5400, gives a quotient of 11*852, one added to this makes 12*852, the square-root of which is 3*6 ; this, less one, is 2*6 ; this, multiplied by 100, gives 260, and this again by 300, gives 78,000 ; this, divided by 120 times the height of the abut- ment, 2400, gives 32 feet 6 inches, the thickness required. The dimensions of a pier will be found by the same rule. For, although the thrust of an arch may be balanced by an ad- joining arch, when the bridge is finished, and while it remains uninjured ; yet, during the erection, and in the event of one arch being destroyed, the pier should be capable of sustaining the en- tire thrust of the other. 321. — Piers are sometimes constructed of timber, their princi- pal strength depending on piles driven into the earth, but such piers should never be adopted where it is possible to avoid them ; for, being alternately wet and dry, they decay much sooner than the upper parts of the bridge. Spruce and elm are considered good for piles. Where the height from the bottom of the river to the roadway is great, it is a good plan to cut them off at a little below low-water mark, cap them with a horizontal tie, and upon this erect the posts for the support of the roadway. This method cuts oif the part that is continually wet from that which is only occasionally so, and thus affords an opportunity for replacing the upper part. The pieces which are immersed will last a great length of time, especially when of elm ; for it is a well-established fact, that timber is less durable when subject to FRAMING. 183 alternate dryness and moisture, than when it is either continually wet or continually dry. It has been ascertained that the piles under London bridge, after having been driven about 600 years, vere not materially decayed. These piles are chiefly of elm, and vholly immersed. 322. — Centres for stone bridges. Fig- 231 is a design for a centre for a stone bridge where intermediate supports, as piles driven into the bed of the river, are practicable. Its timbers are so distributed as to sustain the weight of the arch-stones as they are being laid, without destroying the original form of the centre ; and also to prevent its destruction or settlement, should any of the piles be swept away. The most usual error in badly-constructed centres is, that the timbers are disposed so as to cause the framing to rise at the crown, during the laying of the arch-stones up the sides. To remedy this evil, some have loaded the crown with heavy stones ; but a centre properly constructed will need no such precaution. Experiments have shown that an arch-stone does not press upon the centring, until its bed is inclined to the horizon at an angle of from 30 to 45 degrees, according to the hardness of the stone, and whether it is laid in mortar or not. For general pur- poses, the point at which the pressure commences, may be con- sidered to be at that joint which forms an angle of 32 degrees with the horizon. At this pumt, the pressure is inconsiderable, 184 AMERICAN HOUSE-CARPENTER. but gradually increases towards the crown. At an angle of 45 degrees, the pressure equals about one-quarter the weight of the stone ; at 67 degrees, half the weight ; and when a vertical line, as a 6, {Fig. 232,) passing through the centre of gravity of Fig. 232. the arch-stone, does not fall within its bed, c d, the pressure may be considered equal to the whole weight of the stone. This will be the case at about 60 degrees, when the depth of the stone is double its breadth- The direction of these pressures is consid- ered in a line with the radius of the curve. The weight upon a centre being known, the pressure may be estimated and the tim- ber calculated accordingly. But it must be remembered that the whole weight is never placed upon the framing at once — as seems to have been the idea had in view by the designers of some cen- tres. In building the arch, it should be commenced at each but- tress at the same time, (as is generally the case,) and each side should progress equally towards the crown. In designing the framing, the effect produced by each successive layer of stone should be considered. The pressure of the stones upon one side should, by the arrangement of the struts, be counterpoised by that of the stones upon the other side. 323. — Over a riv^cr whose stream is rapid, or where it is ne cessary to preserve an uninterrupted passage for the purposes of navigation, the centre must be constructed without intermediate supports, and without a continued horizontal tie at the base ; such a centre is shown at Fig. 233. In laying the stones from the base up to a and c, the pieces, b d and h d, act as ties to prevent any rising at b. After this, while the stones are being laid from a and from c to b, they act as struts : the piece, /^, is added foi 185 Fig. 233. additional security. Upon this plan, with some variation to suit circumstances, centres may be constructed for any span usual in stone-bridge building. 324. — In bridge centres, the principal timbers should abut, and not be intercepted by a suspension or radial piece between. These should be in halves, notched on each side and bolted. The timbers should intersect as little as possible, for the more joints the greater is the settling ; and halving them togetlier is a bad practice, as it destroys nearly one-half the strength of the timber. Ties should be introduced across, especially where many timbers meet ; and as the centre is to serve but a temporary pur- pose, the whole should be designed with a view to employ the timber afterwards for other uses. For this reason, all unneces- sary cutting should be avoided. 325. — Centres should be sufficiently strong to preserve a staunch and steady form during the whole process of building; for any shaking or trembling will have a tendency to prevent the mortar or cement from settijig. For this purpose, also, the cen- tre should be lowered a trifle immediately after the key-stone is laid, in order that the stones may take their bearing before the mortar is set : otherwise the joints will open on the under side. The trusses, in centring, are placed at the distance of from 4 to 6 feet apart according to their strength and the weight of the 24 186 AMERICAN HOUSE-CARPENTER. arch. Between every two trusses, diagonal braces should be h* troduced to prevent lateral motion. 326. — In order that the centre maybe easily lowered, the frames, or trusses, should be placed upon wedge-formed sills ; as is shown at dj {Fig. 233.) These are contrived so as to admit of the settling of the frame by driving the wedge, d, with a maul, or, in large centres, a piece of timber mounted as a battering-ram. The operation of lowering a centre should be very slowly performed, in order that the parts of the arch may take their bearing uni- formly. The wedge pieces, instead of being placed parallel with the truss, are sometimes made sufficiently long and laid through the arch, in a direction at right angles to that shown at Fig. 233. This method obviates the necessity of stationing men beneath the arch during the process of lowering ; and was originally adopted with success soon after the occurrence of an accident, in lower- ing a centre, by which nine men were killed. 327. — To give some idea of the manner of estimating the pressures, in order to select timber of the proper scantling, calcu- late the pressure of the arch-stones from i to b, {Fig. 233,) and suppose half this pressure concentrated at a, and acting in the direction, a f. Then, by reference to the laws of pressure and the resistance of timber at Art. 248, 260, 3. SECTION v.— DOORS, WINDOWS, &^. DOORS. 343. A.mong the several architectural arrangements of an edi- fice, the door is by no means the least in importance ; and, if pro- perly constructed, it is not only an article of use, but also of or- nament, adding materially to the regularity and elegance of the apartments. The dimensions and style of finish of a door, should be in accordance with the size and style of the building, or the apartment for which it is designed. As regards the utility of doors, the principal door to a public building should be of suflii- cient width to admit of a free passage for a crowd of people ; while that of a private apartment will be wide enough, if it per- mit one person to pass without being incommoded. Experience has determined that the least width allowable for this is 2 feet 8 inches ; although doors leading to inferior and unimportant rooms may, if circumstances require it, be as narrow as 2 feet 6 inches ; and doors for closets, where an entrance is seldom required, may be but 2 feet wide. The width of the principal door to a public building may be from 6 to 12 feet, according to the size of the building ; and the width of doors for a dwelling may be from 2 feet 8 inches, to 3 feet 6 inches. If the importance of an apart- ment in a dwelling be such as to require a door of greater width 196 AMERICAN HOUSE-CARPENTER. than 3 feet 6 inches, the opening should be closed with two doors, or a door in two folds ; generally, in such cases, where the opening is from 5 to 8 feet, folding or sliding doors are adopted. As to the height of a door, it should in no case be less than about 6 feet 3 inches ; and generally not less than 6 feet 8 inches. 344. — The proportion between the width and height of single doors, for a dwelling, should be as 2 is to 5 ; and, for entrance- doors to public buildings, as 1 is to 2. If the width is given and the height required of a door for a dwelling, multiply the width by 5, and divide ttie product by 2 ; but, if the height is given and the width required, divide by 5, and multiply by 2. Where two or more doors of different widths show in the same room, it is well to proportion the dimensions of the more important by the above rule, and make the narrower doors of the same height as the wider ones ; as all the doors in a suit of apartments, except the folding or sliding doors, have the best appearance when of one height. The proportions for folding or sliding doors should be such that the width may be equal to | of the height ; yet this rule needs some qualification : for, if the width of the opening be greater than one-half the width of the room, there will not be a sufficient space left for opening the doors ; also, the height should be about one-tenth greater than that of the adjacent single doors, 345. — Where doors have but two panels in width, let the stiles and muntins be each | of the width ; or, whatever number of panels there may be, let the united widths of the stiles and the muntins, or the whole width of the solid, be equal to | of the width of the door. Thus : in a door, 35 inches wide, containing two panels in width, the stiles should be 5 inches wide ; and in a door, 3 feet 6 inches wide, the stiles should be 6 inches. If a door, 3 feet 6 inches wide, is to have 3 panels in width, the stiles and muntins should be each 4^ inches wide, each panel being 8 inches. The bottom rail and the lock rail ought to be each equal in width to tV of the height of the door ; and the top rail, and all DOORS, WINDOWS, &C. 197 others, of the same width as the stiles. The moulding on the panel should be equal in width to i of the width of the stile. Fig. 250. 346. — Fig. 250 shows an approved method of trimming doors : a is the door stud ; 6, the lath and plaster ; c, the ground ; d, tfie jamb ; e, the stop ; /and g^ architrave casings ; and A, the door stile. It is customary in ordinary work to form the stop for the door by rebating the jamb. But, when the door is thick and heavy, a better plan is to nail on a piece as at e in the figure. This piece can be fitted to the door, and put on after the door is hung ; so, should the door be a trifle winding, this will correct the evil, and the door be made to shut solid. 347. — Fig. 251 is an elevation of a door and trimmings suita- ble for the best rooms of a dwelling. (For trimmings generally, see Sect. III.) The number of panels into which a door should be divided, is adjusted at pleasure 5 yet the present style of finish- ing requires, that the number be as small as a proper regard for strength will admit. In some of our best dwellings, doors have been made having only two upright panels. A few years expe- rience, however, has proved that the omission of the lock rail is at the expense of the strength and durability of the door ; 9 four-panel door, therefore, is the best that can be made. 348. — The doors of a dwelling should all be hung so as to open into the principal rooms ; and, in general, no door should be hung to open into the hall, or passage. As to the proper edge of the door on which to aflix the hinges, no general rule can be assigned 198 AMERICAN HOUSE-CARPENTER. aK liliaiLIfLMl^tl^mmtJi^JiiAiiiiiiyfnffmiiiJi^j^uMiti mM^um i Lf.mmMJL i LJtnii C _ Fig. 251. It may be observed, however, that a bed-room door should be hung so that, when half open, it will screen the bed ; and a door leading from a hall, or passage, to a principal room, should screen the fire. WINDOWS. 349. — A window should be of such dimensions, and in such a position, as to admit a sufficiency of light to that part of the apartment for which it is designed. No definite rule for the size DOORS, WINDOWS, &C. l99 can well be given, that will answer in all cases ; yet, as an ap- proximation, the following has been used for general purposes. Multiply together the length and the breadth in feet of the apart- ment to be lighted, and the product by the height in feet ; then the square-root of this product will show the required number of square feet of glass. 350. — To ascertain the dimensions of window frames, add 4J inches to the width of the glass for their width, and 6^ inches to the height of the glass for their height. These give the dimen- sions, in the clear, of ordinaiy frames for 12-light windows ; the height being taken at the inside edge of the sill. In a brick wall, the width of the opening is 8 inches more than the width of the glass — 4^ for the stiles of the sash, and 3^ for hanging stiles — and the height between the stone sill and lintel is about 10 g inches more than the height of the glass, it being varied according to the thickness of the sill of the frame. 351. — In hanging inside shutters to fold into boxes, it is ne- cessary to have the box shutter about one inch wider than the flap, in order that the flap may not interfere when both are folded into the box. The usual margin shown between the face of the shutter when folded into the box and the quirk of the stop bead, or edge of the casing, is half an inch ; and, in the usual method of letting the whole of the thickness of the butt hinge into the edge of the box shutter, it is necessary to make allowance for the throw of the hinge. This may, in general, be estimated at i of an inch at each hinging ; which being added to the margin, the entire width of the shutters will be 1^ inches more than the width of the frame in the clear. Then, to ascertain the width of the box shutter, add 1^ inches to the width of the frame in the clear, between the pulley stiles ; divide this product by 4, and add half an inch to the quotient ; and the last product will be the re- quired width. For example, suppose the window to have 3 lights in width, 11 inches each. Then, 3 times 11 is 33, and 4^ added for the wood of the sash, gives 37^ 2>7i and 1^ is 39 200 AMERICAN HOUSE CARPENTER. and 39; divided by 4, gives 9| ; to which add half an inch, and the result will be 10^: inches, the width required for the box shutter. 352. — In disposing and proportioning windows for the walls of a building, the rules of architectural taste require that they be of different heights in different stories, but of the same width. The windows of the upper stories should all range perpendicularly over those of the first, or principal, story; and they should be disposed so as to exhibit a balance of parts throughout the front of the building. To aid in this, it is always proper to place the front door in the middle of the front of the building ; and, where the size of the house will admit of it, this plan should be adopted. (See the latter part of Art. 214.) The proportion that the height should bear to the width, may be, in accordance with general usage, as follows : The height of basement windows, 1^ of the width. " " principal-story " 2| " " " second-story " If " « " third-story " 1| « " " fourth-story " If " " " attic-story " the same as the width. But, in determining the height of the windows for the several stories, it is necessary to take into consideration the height of the story in which the window is to be placed. For, in addition to the height from the floor, which is generally required to be from 28 to 30 inches, room is wanted above the head of the window for the window-trimming and the cornice of the room, besides some respectable space which there ought to be between these. 353. — The present style of finish requires the heads of win- dows in general to be horizontal, or square-headed ; yet, it is well to be possessed of information for trimming circular-headed win- dows, as repairs of these are occasionally needed. If the jambs of a door or window be placed at right angles to the face of the wall, the edges of the sojfif, or surface of the head, would be straight, and its length be found by getting the stretch-out of the DOORS, WINDOWS, &C. 201 circle, {Art. 92 ;)but, when the jambs are placed obliquely to the face of the wall, occasioned by the demand for light in an oblique direction, the form of the soffit will be obtained as in the ollowing article : and, when the face of the wall is circular, as in the succeeding one. / Fig. 252. 354. — To find the for ?n of the soffit for circular window- heads^ when the light is received in an oblique direction. Let a b cdj {Fig. 252,) be the ground-plan of a given window, ande/ a, a vertical section taken at right angles to the face of the jambs. From a, through e, draw ag, at right angles to a b ; obtain the stretch-out of efa^ and make e g equal to it ; divide e g and e f a, each into a like number of equal parts, and drop perpen- diculars from the points of division in each ; from the points of intersection, 1, 2, 3, &c., in the line, a d, draw horizontal lines to meet corresponding perpendiculars from eg; then those points of intersection will give the curve line, d g, which will be the one required for the edge of the soffit. The other edge, c A, is found in the same manner. 355. — To find the form of the soffit for circular window- heads^ when the face of the wall is curved. Let abed, {Fig. 253,) be the ground-plan of a given window, and efa.B. vertical section of the head taken at right angles to the face of the jambs. 26 202 AMERICAN HOUSE-CARPENTER. Fi',^ x:53. Proceed as in the foregoing article to obtain the line, d g ; then that will be the curve required for the edge of the soffit ; the other edge being found in the same manner. If the given vertical section be taken in a line with the face of the wall, instead of at right angles to the face of the jambs, place it upon the line, c 6, [Fig. 252 ;) and, having drawn ordinates at right angles to c 6, transfer them to ef a ; in this way, a section at right angles to the jambs can be obtained. SECTION VL— STAIRS. 356. — The stairs is that m»3chtinlciil arrangement in a build- ing by which access is obtained from one story to another. Their position, form and finish, when determined with discriminating taste, add greatly to the comfort and elegance of a structure. As regards their position, the first object should be to have them near the middle of the building, in order that an equally easy access may be obtained from all the rooms and passages. Next in im- portance is light; to obtain which they would seem to be best situated near an outer wall, in which windows might be construc- ted for the purpose ; yet a sky-light, or opening in the roof, would not only provide light, and so secure a central position for the stairs, but may be made, also, to assist materially as an ornament to the building, and, what is of more importance, afford an op- portunity for better ventilation. 357. — It would seem that the length of the raking side of the pitch-board, or the distance from the top of one riser to the top of the next, should be about the same in all cases ; for, whether stairs be intended for large buildings or for small, for public or for pri- vate, the accommodation of men of the same stature is to be con- sulted in every instance. But it is evident that, with the same effort, a longer step can be taken on level than on rising ground ; 204 AMERICAN HOUSE-CARPENTER. and that, although the tread and rise cannot be proportioned merely in accordance with the style and importance of the build- ing, yet this may be done according to the angle at which the flight rises. If it is required to ascend gradually and easy, the length from the top of one rise to that of another, or the hypothe nuse of the pitch-board, may be long ; but, if the flight is steep, the length must be shorter. Upon this data the followiug problem is constructed. 3.58. — To proportion the rise and tread to one another. Make the line, a b, {Fig. 254,) equal to 24 inches ; from b, erect b c, at right angles to a 6, and make b c equal to 12 inches ; join a and c, and the triangle, a b c, will form a scale upon which to graduate the sides of the pitch-board. For example, suppose a very easy stairs is required, and the tread is fixed at 14 inches. Place it from b to/, and from/; draw f g^ at right angles to a b ; then the length oi f g will be found to be .5 inches, which is a proper rise for 14 inches tread, and the angle, f b g^ will show the degree of inclination at which the flight will ascend. But, in a majority of instances, the height of a story is fixed, while the length of tread, or the space that the stairs occupy on the lower floor, is optional. The height of a story being determined, the height of each rise will of course depend upon the number into which the whole height is divided ; the angle of ascent being more easy if the number be great, than if it be smaller. By dividing STAIRS. 205 the whole height of a story into a certain number of rises, sup- pose the length of each is found to be 6 inches. Place this length from h to A, and draw h i, parallel to a b ; then h i, or b j will be the proper tread for that rise, and J b i will show the angle of as- cent. On the other hand, if the angle of ascent be given, as a b l^ {b I being lOJ inches, the proper length of run for a step- ladder,) drop the perpendicular, I /;, from I Xo k ; then I kb will be the proper proportion for the sides of a pitch-board for that run. 359. — The angle of ascent will vary according to circum- stances. The following treads will determine about the right in- clination for the different classes of buildings specified. In public edifices, tread about 14 inches. In first-class dwellings " 12^ " In second-class " "11 " In third-class " and cottages " 9 " Step-ladders to ascend to scuttles, (fee, should have from 10 to 11 inches run on the rake of the string. (See notes at Ai^t. 103.) 360. — The length of the steps is regulated according to the ex- tent and importance of the building in which they are placed, varying from 3 to 12 feet, and sometimes longer. Where two per- sons are expected to pass each other conveniently, the shortest length that will admit of it is 3 feet ; still, in crowded cities where land is so valuable, the space allowed for passages being very small, they are frequently executed at 2 J feet. 361. — To find the dimensions of the pitch-board. The first thing in commencing to build a stairs, is to make the /^zVcA-board ; this is done in the following manner. Obtain very accurately, in feet and inches, the perpendicular height of the story in which the stairs are to be placed. This must be taken from the top ot the floor in the lower stoiy to the top of the floor in the upper story. Then, to obtain the number of rises, the height in inches thus obtained must be divided by 5, 6, 7, 8, or 9, according to the quality and style of the building in which the stairs are to be 206 AMERICAN HOUSE-CARPENTER. built. For instance, suppose the building to be a first-class dwelling, and the height ascertained is 13 feet 4 inches, or 160 inches. The proper rise for a stairs in a house of this class is about 6 inches. Then, 160 divided by 6, gives 26f inches. This being nearer 27 than 26, the number of risers, should be 27. Then divide the height, 160 inches, by 27, and the quotient will give the height of one rise. On performing this operation, the quotient will be found to be 5 inches, | and ~ of an inch. Then, if the space for the extension of the stairs is not limited, the tread can be found as at Art. 358. But, if the contrary is the case, the whole distance given for the treads must be divided by the number of treads required. On account of the upper floor forming a step for the last riser, the number of treads is always one less than the number of risers. Having obtained this rise and tread, the pitch-board may be made in the follow- ing manner. Upon a piece of well-seasoned board about | of an inch thick, having one edge jointed straight and square, lay the corner of a carpenters'-square, as shown at Fig. 255. Make a h Fig. 255. equal to the rise, and h c equal to the tread ; mark along those edges with a knife, and cut it out by the marks, making the edges perfectly square. The grain of the wood must run in the direction indicated in the figure, because, if it shrinks a trifle, the rise and the tread will be equally affected by it. When a pitch-board is first made, the dimensions of the rise and tread should be pre- served in figures, in order that, should the first shrink, a second could be made. 362. — To lay out the string. The space required for timber 2ivr Fitr. 25(j. and plastering under the steps, is about 5 inches for ordinary stairs ; set a gauge, therefore, at 5 inches, and run it on the lower edge of the plank, as a 6, {Fig. 256.) Connnencing at one end, lay the longest side of the pitch-board against the gauge-mark, a 6, as at c, and draw by the edges the lines for the first rise and tread; then place it successively as at d, e and/, until the re- quired number of risers shall be laid down. F7 UJ. Fig. 257. 363. — Fig. 257 represents a section of a step and riser, joined after the most approved method. In this, a represents the end of a block about 2 inches long, two of which are glued in the corner in the length of the step. The cove at b is planed up square, glued in, and stuck after the glue is set. PLATFORM STAIRS. 364. — A platform stairs ascends from one story to another in two or more flights, having platforms between for resting and to cnange their direction. This kind of stairs is the most easily constructed, and is therefore the most common. The cyliu 20n AMERICAN HOUSE-CAIIPENTBE. Fig. 258. der is generally of small diameter, in most cases about 6 inches. It may be worked out of one solid piece, but a better way is to glue together three pieces, as in Fig. 258; in which the piece.^j a, b and c, compose the cylinder, and d and e represent parts of the strings. The strings, after being glued to the cylinder, are secured with screws. The joining at o and r? is the most proper for that kind of joint. 36.5. — 7^0 obtain the form of the lower edge of the cylinder. Find the stretch-out, d e, {Fig. 259,) of the face of the cylinder, a 6 c, according to Art. 92 ; from d and e, draw d f and e g, at right angles to d e ; draw h g, parallel to d e, and make hf and g i, each equal to one rise; from i and/, draw ij and/ A:, paral- lel to h g ; place the tread of the pitch-board at these last lines, and draw by the lower edge the lines, k h and i I ; parallel to tnese, draw m n and o p, at the requisite distance for the dimen- sions of the string : from 5, the centre of the plan, draw s q. parallel to df; divide h qand q g, each into 2 equal parts, as at V and w; from v and w, draw v n and w o, parallel to/ c?; join n and 0, cutting q s m r ; then the angles, u n r and rot, being eased off according to Art. 89, will give the proper curve for the bottom edge of the cylinder. A centre may be found upon which to describe these curves thus : from w, draw u :r, at right angles to mn; from r, draw r a:, at right angles to no ; then x will be the centre for the curve, u r. The centre for the curve, r ^, is found in the same manner. STAIRS. 209 Fig. 259. 366. — To find the position for the balusters. Place the centre of the first baluster, (6. Fig. 260,) 5 its diameter from the face of the riser, c c?, and i its diameter from the end of the step, e d ; and place the centre of the other baluster, a, half the tread from the centre of the first. The centre of the rail must be placed over the centre of the balusters. Their usual length is 2 feet 5 inches, and 2 feet 9 inches, for the short and the long balusters respectively. a- ^ Piir sm. 27 210 AMERICAN HOUSE-CARPENTER. Fig. 261. 367. — To find the face-mould for a round hand-rail to plat- form stairs. Case 1. — When the cylinder is small. In Fig. 261, J and e represent a vertical section of the last two steps of the first flight, and d and i the first two steps of the second flight, of a platform stairs, the line, e /, being the platform ; and a 6 c is the plan of a line passing through the centre of the rail around the cylinder. Through i and d, draw i k, and through J and e, draw 7 k ; from A;, draw k Z, parallel to /e ; from 6, draw h m, parallel tog d; from /, draw I r, parallel to kj ; from n, draw n /, at right angles to jf k : on the line, o b. maki. o t equal to w ^ ; join c and ^ : on ie line, j c, {Fig. 262,) make e c equal to e w at Fig. 261 ; from c, draw c t^ ai nt'ht angles Xoj c, and make c t STAIRS. 21J i I Fig. 262. equal to c ^ at Fig. 261 ; through t, drawp /, parallel ioj c, and make 1 1 equal to ^ / at Fig. 261 : join I and c, and complete the parallelogram, eels; find the points, o, o, o, according to ^rCA RPENTER. h d i- lu. -I'S. bit in the gauge-mark at a. and bore in the direction, a c. To do this easily, make chucks as represented in the figure, the bottom edge, g- h, being parallel to o c, and having a place sawed out, as ef, to receive the rail. These being nailed to the bench, the rail will be held steadily in its proper place for boring vertically. The distance apart that the balusters require to be, on the under side of the rail, is one-half the length of the rake-side of the pitch-board. Fig. 269 STAIRS. 217 373. — To obtain, by the foregoing principles, the face-mould for the twists of a moulded rail upon platform stairs. In Fig. 269, a b c is the plan of a line passing through the centre of the rail around the cylinder as before, and the lines above it are a vertical section of steps, risers and platform, v\^ith the hnes for the rail obtained as in Fig. 261. Set half the width of the rail from b to f and from b to r, and from / and r, draw/ e and r d, parallel to c a At Fig. 270, the centre lines of the s d n e ml ^ /t~~ iHv \ Ic/ i c // { 1 ^^ , g J Fig. 270. rail, k c and c n, are obtained as in the previous examples. Make c i and c j, each equal to c i at Fig. 269, and draw the lines, i m and j g, parallel to c k ; make n e and n d equal to n e and n d at Fig. 269, and draw d o and e I, parallel to n c ; also, through k, draw s g, parallel to n c ; then, in the parallelograms, m s d o and g s e I, find the elliptic curves, d m and e g, according to Art. 118, and they will define the curves. The line, d e, being drawn through n parallel to k c, defines the joint, which is to be cut through the plank vertically. If the rail crosses the platform rather steep, a butt joint will be preferable, to obtain which see Art. 405. 218 AMERICAN HOUSE-CARPENTEJl. 374. — To apply the mould to the plank. The mould obtained according to the last article must be applied to both sides of the plank, as shown at Fig. 271. Before applying the mould, the edge, e/, must be bevilled according to the angle, c t x^dX Fig. 269 ; if the rail is to be canted up, the edge must be bevilled at an obtuse angle with the upper face ; but if it is to be canted down, the angle that the edge makes with the upper face mnst be acute. From the spring of the curve, a, and the end, c, draw vertical lines across the edge of the plank by applying the pitch- board, a b c ; then, in applying the mould to the other side, place the points, a and c, at b and/; and, after marking around it, saw the rail out vertically. After the rail is sawed out, the bottom and the top surfaces must be squared from the sides. 375. — To ascertain the thickness of stuff required for the twists. The thickness of stuff required for the twists of a round rail, as before observed, is the same as that for the straight ; but for a moulded rail, the stuff for the twists must be thicker than that for the straight. In Fig. 269, draw a section of the rail be- tween the lines, d r and e f and as close to the line, d e, as possi- ble ; at the lower corner of the section, draw g A, parallel to d e; then the distance that these lines are apart, will be the thickness required for the twists of a moulded rail. . The foregoing method of finding moulds for rails is applicable to all stairs which have continued rails around cylinders, and are without winders. WINDING STAIRS. 376. — Winding stairs have steps tapering narrower at one end than at the other. In some stairs, there are steps of parallel width incorporated with tapering steps ; the former are then called ^yer* and the latter tiinders. 377. — To describe a regular geometrical winding stairs. In Fig. 272, abed represents the inner surface of the wall en- closing the space allotted to the stairs, a e the length of the steps, and efgh the cylinder, or face of the front string. The line, STAIRS. 219 Fig. 272. a e, is given as the face of the first riser, and the point, j^ for the limit of the last. Make e i equal to 18 inches, and upon o, with i for radius, describe the arc, ij; obtain the number of risers and of treads required to ascend to the floor at j, according to Art. 361, and divide the arc, ij, into the same number of equal parts as there are to be treads ; through the points of division, 1, 2, 3. &c., and from the wall-string to the front-string, draw lines tend- ing to the centre, o ; then these lines will represent the face of each riser, and determine the form and width of the steps. Allow the necessary projection for the nosing beyond a e, which should be equal to the thickness of the step, and then a el k will be the dimensions for each step. Make a pitch-board for the wall-string having a k for the tread, and the rise as previously ascertained ; with this, lay out on a thicknessed plank the several risers and treads, as at Fig, 256, gauging from the upper edge of the string for the line at which to set the pitch-board. Upon the back of the string, with a 1;^ inch dado plane, make 220 AMERICAN HOUSE-CARPENTER. a succession of grooves IJ inches apart, and parallel with the lines for the risers on the face. These grooves must be cut along the whole length of the plank, and deep enough to admit of the plank's bending around the curve, abed. Then construct a drum, or cylinder, of any common kind of stuff, and made to fit a curve having a radius the thickness of the string less than o a ; upon this the string must be bent, and the grooves filled with strips of wood, called ke^s, which must be very nicely fitted and glued in. After it has dried, a board thin enough to bend around on the outside of the string, must be glued on from one end to the other, and nailed with clout nails. In doing this, be careful not to nail into any place where a riser or step is to enter on the face. After the string has been on the drum a sufficient time for the glue to set, take it off, and cut the mortices for the steps and risers on the face at the lines previously made ; which may be done by boring with a centre-bit half through the string, and nicely chiseling to the line. The drum need not be made so large as the whole space occupied by the stairs, but merely large enough to receive one piece of the wall-string at once — for it is evident that more than one will be required. The front string may be constructed in the same manner ; taking e I instead of a k for the tread of the pitch-board, dadoing it with a smaller dado plane, and bending it on a drum of the proper size. Fig. 273. 378. — To find the shape and position of the timbers neces- sary to support a winding stairs. The dotted lines in Fig. 272 show the proper position of the timbers as regards the plan : the shape of each is obtained as follows. In Fig. 273, the line, 1 a, is equal to a riser, less the thickness of the floor, and the lines, 2 w, 3 w, 4 0, 5 /? and 6 q, are each equal to one riser. The STAIRS. 2li\ line, a 2, is equal to am in Fig. 272, the line, m 3 to m ?i in that figure, &c. In drawing this figure, commence at a, and make the lines, a 1 and a 2, of the length above specified, and draw them at right angles to each other ; draw 2 m, at right angles to a 2, and m 3, at right angles to m 2, and make 2 m and m 3 of the lengths as above specified : and so proceed to the end. Then, through the points, 1, 2, 3, 4, 5 and 6, trace the line, 1 b ; upon the points, 1, 2, 3, 4, &c., with the size of the timber for radius, describe arcs as shown in the figure, and by these the lower line may be traced parallel to the upper. This will give the proper shape for the timber, a b, in Fig. 272 ; and that of the others may be found in the same manner. In ordinary cases, the shape of one face of the timber will be sufiicient, for a good workman can easily hew it to its proper level by that ; but where great accuracy is desirable, a pattern for the other side may be found in the same manner as for the first. 379. — To find the falling-mould for the rail of a loinding stairs. In Fig. 274, a cb represents the plan of a rail around half the cylinder, A the cap of the newel, and 1, 2, 3, &c., the face of the risers in the order they ascend. Find the stretch-out, e f of a c b, according to Art. 92; from o, through the point of the mitre at the newel-cap, draw o s ; obtain on the tangent, e d, the position of the points, s and h'* as. at t and/^ ; from e tf^ and /, draw e a;, t u,/^ g'^ and /A, all at right angles Xo e d ; make e g equal to one rise and/- ^^ equal to 12, as this line is drawn from the 12th riser ; from g^ through g^.^ draw^ i; make g x equal to about three-fourths of a rise, (the top of the newel, x, should be 3^ feet from the floor ;) draw x w, at right angles to e x^ and ease off the angle at w ; at a distance equal to the thickness of • In the above, the references, a^, U^, &c., are introduced for the first time. During the time taken to refer to the figure, the memory of the /otto of these may pass from the mind, while that of the sound alone remains ; they may then be mistaken for a 2, 6 2, &c. This can be avoided in reading by giving them a sound corresponding to their meaning, which IS second a second h, &c. or a second, b second. 222 AMERICAN HOUSE-CARPENTER. r[ie rail, draw v w y, parallel to x ii i; from the centre of the plan, 0, draw o I, at right angles to e d ; bisect h n in p, and through />, at right angles to,^' i, draw a line for the joint; in tlie same manner, draw the joint at k ; then x y will be the falling-mould for that part of the rail which extends from 5 to 6 on the plan. 380. — To find the face-mould for the railof axoinding-stairs. From the extremities of the joints in the falling-mould, as A', z and y, (Fig. 274,) draw k a^, z 6^ and y c?, at right angles Xo e d : make h ^ equal to / d. Then, to obtain the direction of \\v?. joint, c^ c^, or 6^ d\ proceed as at Fig. 275, at which the parts are STAIRS. 223 Fig. 275. shown at half their fill! size. A is the plan of the rail, and B is the falling-monid : in which k z is the direction of the butt-joint. From kj draw k b, parallel to I o, and k e, at right angles to k b ; from 6, draw b /, tending to the centre of the plan, and from/, draw / e, parallel to b k ; from Z, through e, draw I ^, and from i, draw i d, parallel toef; join d and 6, and d b will be the proper direction AMERICAN HOUSE-CARPENTER. for the joint on the plan. The direction of the joint on the other side, a c, can be found by transferring the distances, x h and o rf, Xo X a and o c. (See Art. 384.) Fi-. 27G. Having obtained the direction of the joint, make s r d b, (Fig. 276,) equal to 5 r db'^ in Fig. 27 A ; through r and d, draw t a ; through 6' and from d, draw t u and d e, at right angles to t a ; make t u and d e equal to t u and 6^ m, respectively, in Fig. 274 ; from w, through e, draw u ; through 6, from r, and from as many other points in the line, t a, as is thought necessary, as/, h and ;, draw the ordinates, r c,fg, h i,j k and a ; from w, c, ^, ^J k^ e and 0, draw the ordinates, ii 1, c 2, g 3, i A, k 5, e 6 and 7, at right angles to it, ; make ?i 1 equal to ^ 5, c 2 equal to r 2, ^ 3 equal to/ 3, &c., and trace the curve, 1 7, through the points thus found ; find the curve, c e, in the same manner, by transfer- ring the distances between the line, t a, and the arc, r d ; join 1 and c, also e and 7 ; then, I c e 7 will be the face-mould required for that part of the rail which is denoted by the letters, s r d* b"^, on the plan at Fig. 27 L To ascertain the mould for the next quarter, make acje, (i'V^. STAIRS. 22k Fig. 277. 277,) equal to a' c^j e^ at Fig. 274 ; at any convenient height on the h'ne, d i, in that figure, draw q i\ parallel to e d ; through c and J, {Fig. 277,) draw b d ; through a, and from 7, draw b k and ; 0, at right angles to b d ; make b k an&j equal to ^ k and q i, respectively, in Fig. 27 A ; from k, through 0, draw kf; and proceed as in the last figure to obtain the face-mould, A. 381. — To ascertain the requisite thickness of stuff. Case 1. — When the falling-mould is straight. Make h and k m, {Fig. 277,) equal to i y at Fig. 274 ; draw h i and m n, parallel tob d ; through the corner farthest from k f as n or ^, draw n ^, parallel to kf ; then the distance between k f and n i will give the thickness required. 382. — Case 2. — When the falling-mould is curved. In FHg. 278, sr db'is, equal tosr d^Wm. Fig. 27 L Make a c equal to the stretch-out of the arc, s 6, according to Art. 92, and divide a c and s b. each into a like number of equal parts ; from a and c. and from each point of division in the line, ac, draw ak^el^ (fee, at right an- gles to a c ; make a A; equal to ^ w in Fig. 274, and c; equal to 6' wi 29 22t AMERICAN HOUSE-CARPENTER. in that figure, and complete the ral ling-mould, kj, every way equal to M m in Fig. 274 ; from the points of division in the arc, sb, draw lines radiating towards the centre of the circle, dividing the arc. r d, in the same proportion ass bis divided ; from d and b, draw dtanAb u, at right angles to a d, and from j and v, dmwj u and v w, at right angles toj c ; then xtuwwiWhea. vertical projection of the joint, d b. Supposing every radiating line across s r d b~ corresponding to the vertical lines across A: ^-to represent a joint, find their vertical projection, as at 1, 2, 3, 4, 5 and 6 ; through the corners of those parallelograms, trace the curve lines shown in the figure ; then 6 u will be a helinet, or vertical projection, oisrdb. To find the thickness of plank necessary to get out this part of the rail, draw the line, z t, touching the upper side of the helinet m two places : through the corner farthest projecting from that line, as w, draw y w, parallel to ^ ^- then the distance between those Imes will be the proper thickness of stuff for this part of the rail. The same process is necessary to find the thickness of stuff in all cases in which the falling-mould is in any way curved. i»i— To apply the face-mould to the plank. In Pig 279 A represents the plank with its best side and edge in view and B the same plank turned up so as to bring in view the other side STAIRS. 227 Fig. 279. and the same edge, this being square from the face. Apply the tips of the mould at the edge of the plank, as at a and o, (^,) and mark out the shape of the twist ; from a and o, draw the lines, a h and o c, across the edge of the plank, the angles, e a h and e o Cj corresponding with kfd at Fig. 277 ; turning the plank up as at Bj apply the tips of the mould at b and c, and mark it out as shown in the figure. In sawing out the twist, the saw must be be moved in the direction, a b ; which direction will be perpen- dicular when the twist is held up in its proper position. In sawing by the face-mould, the sides of the rail are obtained ; the top and bottom, or the upper and the lower surfaces, are ob- tained by squaring from the sides, after having bent the falling- mould around the outer, or convex side, and marked by its edges. Marking across by the ends of the falling-mould will give the position of the butt-joint. 384. — Elucidation of the process by which the direction of the butt-joint is obtained in Art. 380. Mr. Nicholson, in his Carpenter^s Guide, has given the joint a different direction to that here shown ; he radiates it towards the centre of the cylin- der. This is erroneous — as can be shown by the following operation : In Fig. 280, a r j i'ls, the plan of a part of the rail about the joint, 5 w is the stretch-out of a i, and g p is the helinet, or ver- tical projection of the plan, a r j i, obtained according to Art 328 AMERICAN HOUSE-CARPENTER. gR Fig. 'iSO. 382. Bisect r t, part of an ordinate from the centre of the plan, and through the middle, draw c b, at right angles to g v ; from b and c, draw c d and b e, at right angles to s u ; from d and e, draw lines radiating towards the centre of the plan : then d o and e m will be the direction of the joint on the plan, according to Nicholson, and c b its direction on the falling-mould. It will be admitted that all the lines on the upper or the lower side of the rail which radiate towards the centre of the cylinder, as c? o, e m or ij^ are level j for instance, the level line, w t?, on the top of the STAIRS. 229 rail in the helinet, is a true representation of the radiating line, j i on the plan. The line, b A, therefore, on the top of the rail in the helinet, is a true representation of e mon the plan, and A: c on the bottom of the rail truly represents d o. From k, draw k /, parallel to c b, and from h, draw hf, parallel to 6 c ; join I and b, also c and/; then c k I b will be a true representation of the end of the lower piece, B^ and c fh b of the end of the upper piece, A ; and/ k oi h I will show how much the joint is open on the inner, or concave side of the rail. Fig. '981. 230 AMERICAN HOUSE-CARPENTER. To show that the process followed in Art. 380 is correct, let d o and e m, {Fig. 281,) be the direction of the butt-joint found as at Fig. 275. Now, to project, on the top of the rail in the helinet, a line that does not radiate towards the centre of the cylinder, as j kj draw vertical lines from J and k to w and A, and join w and h ; then it will be evident that whissi true representation in the helinet of j k on the plan, it being in the same plane as ; k, and also in the same winding surface as w v. The Hue, I w, also, is a true repre- sentation on the bottom of the helinet of the line, j' A:, in the plan. The line of the joint, e m^ therefore, is projected in the same way and truly by i 6 on the top of the helinet ; and the line, d o, by c a on the bottom. Join a and i, and then it will be seen that the lines, c a, a i and i b, exactly coincide with c 6, the line of the joint on the convex side of the rail ; thus proving the lower end of the upper piece, A, and the upper end of the lower piece, B, to be in one and the same plane, and that the direction of the joint on the plan is the true one. By reference to Fig. 275, it will be seen that the line, I i, corresponds to a; i in Fig. 281 ; and that e k in that figure is a representation of/ b, and i k of d b. Fig.ses. In getting out the twists, the joints, before the falling-mould is STAIRS. 231 applied, are cut perpendicularly, the face-mould being long enough to include the overplus necessary for a butt-joint. The face-mould for A, therefore, would have to extend to the line, i b ; and that for B, to the line, yz. Being sawed vertically at first, a section of the joint at the end of the face-mould for A, would be represented in the helinet by h if g. To obtain the position of the line, h i, on the end of the twist, draw i .«?, {Fig-. 282,) at right angles to if, and make i s equal to m e at Fig. 281 ; through 5, draw 5 g, pa- rallel to if, and make s h equal to 5 6 at Fig. 281 ; join h and i ; make i/equal to i /at Fig. 281, and from f, draw/^, parallel to i b ; then i b gf will be a perpendicular section of the rail over the line, e m, on the plan at Fig. 281, corresponding toi b gf in the helinet at that figure ; and when the rail is squared, the top, or back, must be trimmed off to the line, i b, and the bottom to the line, fg. 385. — To grade the front string of a stairs, havi?ig winders in a quarter-circle at the top of the flight connected with flyers at the bottom. In Fig. 283, a b represents the line of the facia along the floor of the upper story, bee the face of the cylinder, and c d the face of the front string. Make g b equal to | of the diameter of the baluster, and draw the centre-line of the rail, y*^, g h i and ij, parallel to a b, b e c and c d; make g k and g I each equal to half the width of the rail, and through k and /, draw lines for the convex and the concave sides of the rail, parallel to the centre-line ; tangical to the convex side of the rail, and parallel to k m, draw no; obtain the stretch-out, g r, of the semi-circle, k J) m, according to Art. 92 ; extend ab to t, and k mio s ; make c s equal to the length of the steps, and i u equal to 18 inches, and de- scribe the arcs, s t and u 6, parallel to mp ; from t, draw t w, tend- ing to the centre of the cylinder ; from 6, and on the line, 6ux, run ofl" the regular tread, as at 5, 4, 3, 2, 1 and v ; make it x equal to half the arc, u 6, and make the point of division nearest to ar, as v, the limit of the parallel steps, or flyers ; make r o equal iomz ; from 0, draw o a^. at right angles to n o, and equal to one rise ; 232 AMERICAN HOUSE-CARPENTER. 713 A3 r8 h^ Fig. 283. from a^5 draw a^ s, parallel to it o, and equal to one tread ; from s, through 0, draw 5 6\ Then from w, draw w c^, at right angles to n o, and set up, on the line, w c', the same number of risers that the floor, J., is above the first winder, B, as at 1, 2, 3, 4, 5 and 6; through 5, (on the arc, 6 u,) draw dr e^, tending to the centre of the cylinder ; from c^, draw s^/^, at right angles to n o, and through 5, (on the line. STAIRS. 233 w c',) draw ^'/^ parallel Xono ; through 6, (on the line, w c^,) and/^, draw the line, K^ ¥ ; make 6 coequal to half a rise, and from c' and 6, draw c^ r and 6/, parallel ion o ; make h^ i^ equal to h^p ; from i^, draw iH-*^, at right angles to i^ A^, and from/-, draw/*^^, at right angles to/Vi%' upon F, with Ic^ p for radius, describe the arc,/^ i%- make 6^ Z^ equal to h"^ f^-, and ease off the angle at h^ by the curve, f^ P. In the figure, the curve is de- scribed from a centre, but in a full-size plan, this would be imprac- ticable ; the best way to ease the angle, therefore, would be with a tanged curve, according to Art. 89. Then from 1, 2, 3 and 4, (on the line, w c^,) draw lines parallel to 7i o, meeting the curve in m^, 7i^, 0^ and p"^ ; from these points, draw lines at right angles to n 0, and meeting it in x"^, r^, s"^ and f; from x^ and r\ draw lines tending to w^, and meeting the convex side of the rail in y^ and z"^ ; make ni v^ equal to r s"^, and tu w'^ equal to r f ; from y-, z''. ^;^ and iv"^, through 4, 3, 2 and 1, draw lines meeting the line of the wall-string in a^, 6^, c^ and cP ; from e^, where the centre-line of the rail crosses the line of the floor, draw e^f^, at right angles to n 0, and from /^, through 6, draw/^ g"^ ; then the heavy lines,/^^', e^ (P, if' d^ z^ 6^, v^ &^ \c^ (P^ and zy^ will be the lines for the risers, which, being extended to the line of the front string, b e c d^ will give the dimensions of the winders, and the grading of the front string, as was required. 386. — To obtain the falling-mould for the twists of the last- mentioned stairs. Make P g^ and P h^, {Fig. 283,) each equal to half the thickness of the rail ; through h^ and g^^ draw h^ r dind g^f, parallel to P s ; assuming k k^ and m w^ on the plan as the amount of straight to be got out with the twists, make 7i q equal to k k^, and r P equal to ?n m^ ; from n and Z^, draw lines at right angles to n o, meeting the top of the falling-mould in rv' and 0^ ; from o^, draw a line crossing the falling-mould at right angles to a chord of the curve, /^ V ; through the centre of the cylinder, draw u^ 8, at right angles to 7i o : through 8, draw 7 9, tending to k^ ; then n^ 7 will be the falling-mould for the upper twist, and 7 0^ the falling-mould for the lower twist. 30 234 AMERICAN HOUSE-CARPENTER. 387. — To obtain the face-moulds. The moulds for the twists of this stairs may be obtained as at Art. 380 ; but, as the faUing- mould in its course departs considerably from a straight line, it would, according to that method, require a very thick plank for the rail, and consequently cause a great waste of stuiF. In order, therefore, to economize the material, the following method is to be preferred — in which it will be seen that the heights are taken in three places instead of two only, as is done in the previous method. Fig, 284. o Case 1. — When the middle height is above a line joining the other two. Having found at Fig. 283 the direction of the joint, w s^ and p e, according to Art. 380, make k p e a^ {Fig. 284,) equal to W p^ e p in Fig. 283 ; join h and c, and from o, draw A, at right angles to b c ; obtain the stretch-out of d g, as dfj and at Fig. 283, place it from the axis of the cylinder, p, to q^ ; from q^ in that figure, draw q^ r\ at right angles ion o ; also, at a convenient height on the line, n n% in that figure, and at right angles to that line, draw u^ v^ ; from b and c, in Fig. 284, STAIRS. 235 draw h j and c Z, at right angles to b c ; make b j equal to u^ n' in Fig. 283, i h equal to lu^ r^ in th?it figure, and c Z equal \o v^ ^ \ from Zj through j*, draw / m ; from A, draw /i n, parallel to c b ; from 71. draw n r, at right angles to b c, and join ?' and 5 ; through the lowest corner of the plan, as />, draw v e, parallel to b c ; from a, e, II, p, k, t, and from as many other points as is tliought ne- cessary, draw ordinates to the base-line, v e, parallel to ?' s : through A, draw w x, at right angles to in I ; upon n, with r s for radius, describe an intersecting arc at x, and join n and x ; from the points at wliich the ordinates from the plan meet the base- line, V e, draw ordinates to meet the line, m /, at right angles to v e ; and from the points of intersection on in Z, draw correspond- ing ordinates, parallel to nx ; make the ordinates which are pa- rallel to n :r of a length corresponding to those Vv^hich are parallel to r s, and through the points thus found, trace the face-mould as required. Case 2. — When the middle height is below a line joining the other two. The lower twist in Fig. 283 is of this nature. The face-mould for this is found at Fig. 285 in a manner similar to that at Fig. 284. The heights are all taken from the top ot the falling-mould at Fig. 283 ; b j being equal to lo 6 in Fig. 283. i h equal to x^ if" in that figure, and cl\ol^ ol Draw a line through J and Z, and from A, draw h tz, parallel to 6 c ; from n. draw n i\ at right angles to b c, and join r and s ; then r s will be the bevil for the lower ordinates. From A, draw h x, at right an- gles toj I ; upon ?i, with 7' s for radius, describe an intersecting arc at x, and join n and x : then n x will be the bevil for the upper ordinates, upon which the face-mould is found as in Case 1. 388. — Elucidation of the foregoing method. — This method of finding the face-moulds for the handrailing of winding stairs, being founded on principles which govern cylindric sections, may be illustrated by the following figures. Fig. 286 and 287 repre- sent solid blocks, or prisms, standing upright on a level base, b d : 'he upper surface, j a forming oblique angles with the face, b I — 236 AMERICAN HOUSE-CARPENTER. Fig. 285. in Fig. 286 obtuse, and in Fig. 287 acute. Upon the base, de- scribe the semi-circle, h s c ; from the centre, i, draw i s, at right angles to 6 c ; from 5, draw 5 x, at right angles to e d, and from i, draw i h, at right angles to b c ; make i h equal to 5 x, and join h and x ; then, h and x being of the same height, the line, h x, joining them, is a level line. From A, draw h w, parallel to h c, and from?^, draw n r, at right angles tob c; join r and 5, also n STAIBS. 237 Fiff. 286. !■ ijr. vJr^7. and ^; then, n and x being of the same height, n x is a level hne ; and this line lying perpendicularly over r 5, n x and r s must be of the same length. So, all lines on the top, drawn parallel to n or, and perpendicularly over corresponding Unes drawn parallel to r 5 on the base, must be equal to those lines on the base ; and by drawing a number of these on the semi-circle at the base and others of the same length at the top, it is evident that a curve, j X Z, may be traced through the ends of those on the top, which shall lie perpendicularly over the semi-circle at the base. It is upon this principle that the process at Fig. 284 and 285 is founded. The plan of the rail at the bottom of those figures is supposed to lie perpendicularly under the face-mould at the top ; and each ordinate at the top over a corresponding one at the base. The ordinates, n x and r 5, in those figures, correspond to n x and r 5 in Fig. 286 and 287. In Fig. 288, the top, e a, forms a right angle with the face, d c ; all that is necessary, therefore, in this figure, is to find a line corresponding to h x in the last two figures, and that will lie level and in the upper surface ; so that all ordinates at right angles to dron the base, will correspond to those that are at right angles 238 AMERICAN HOUSE-CARPENTER. F\-^ 2S8. r to e c on the top. This ekicidates Fig: 276 ; at which the lines, h 9 and i 8, correspond to h 9 and i 8 in this figure. Fig. 289. 389. — To find the hevil for the edge of the plank. The plank, before the face-mould is applied, must be bevilled accord- ing to the angle which the top of the imaginary block, or prism, in the previous figures, makes with the face. This angle is de- termined in the following manner : draw w i, [Fig. 289,) at right angles to i s, and equal to w hat Fig. 284 ; make i s equal to t 5 in that figure, and join iv and s ; then sw p will be the bevil required m order to apply the face-mould at Fig. 284. In Fig. 285, the middle height being below the line joining the other two, the bevil is therefore acute. To determine this, draw i s, (Fig. 290,) at STAIRS. 239 Fig. 290. right angles to i p, and equal to i 5 in Fig". 285 ; make 5 w equal \o h w in Fig. 285, and join w and i ; then tv i p will be the bevil required in order to apply the face-mould at Fig. 285. Al- though the falling-mould in these cases is curved, yet, as the plank is sprung, or bevilled on its edge, the thickness necessary to get out the twist may be ascertained according to Art. 381 — taking the vertical distance across the falling-mould at the joints, and placing it down from the two outside heights in Fig. 284 or 285. After bevilling the plank, the moulds are applied as at Art. 383 — applying the pitch-board on the bevilled instead of a square edge, and placing the tips of the mould so that they will bear the same relation to the edge of the plank, as they do to the line, j /, in Fig. 284 or 285. Fig. 291. 390. — To apply the moulds ivithout bevilling the plank. Make w p, {Fig. 291,) equal to w p at Fig, 289, and the angle, bed, equal to 6 j I in Fig. 284 ; make p a equal to the thick- ness of the plank, as w? a in Fig. 289, and from a draw a o, pa- rallel tow d ; from c, draw c e, at right angles to w d, and join e 240 AMERICAN HOUSE'CARPENTER. and h ; then the angle, b e o,ona square edge of the plank, hav- ing a Ime on the upper face at the distance, p a, in Fig. 289, at which to apply the tips of the mould — will answer the same pur- pose as bevilling the edge. If the bevilled edge of the plank, which reaches from p to w, is supposed to be in the plane of the paper, and the point, a, to be above the plane of the paper as much as a, in Fig. 289, is dis- tant from the line, w p ; and the plank to be revolved on p 6 as an axis until the line, p w, falls below the plane of the paper, and the line, p a, arrives in it ; then, it is evident that the point, c, will fall, in the line, c e, until it lies directly behind the point, e, and the line, b c, will lie directly behind b e. k Fig. 292. 391. — To find the b evils for splayed work. The principle employed in the last figure is one that will serve to find the bevils for splayed work — such as hoppers, bread-trays, &c. — and a way of applying it to that purpose had better, perhaps, be introduced in this connection. In Fig. 292, a 6 c is the angle at which the work is splayed, and b c?, on the upper edge of the board, is at right angles to a b ; make the angle, /^^', equal to a b c, and from/, draw /A, parallel to e a; from 6, draw b o, at right an- gles Xoab ; through o, draw i e, parallel to c 6, and join e and d ; then the angle, a e d, will be the proper bevil for the ends from the inside, ox k d e from the outside. If a mitre-joint is re- STAIRS. 211 quired, setfg, the thickness of the stuff on the level, from e to m, and join th and d ; then k d m will be the proper bevil for a mitre-joint. If the upper edges of the splayed work is to be bevilled, so as to be horizontal when the work is placed in its proper position, fgj, being the same as a 6 c, will be the proper bevil for that purpose. Suppose, therefore, that a piece indicated by the lines, k g, g-f and /A, were taken off; then a line drawn upon the bevilled surface from d, at right angles to k d, would show the true position of the joint, because it would be in the direction of the board for the other side ; but a line so drawn would pass through the point, o, — thus proving the principle correct. So, if a line were drawn upon the bevilled surface from d, at an angle of 45 degrees to k d, it would pass through the point, n. 392. — Another method for face-'inoulds. It will be seen by reference to Art. 388, that the principal object had in view in the preparatory process of finding a face-mould, is to ascertain upon it the direction of a horizontal line. This can be found by a method diflferent from any previously proposed ; and as it requires fewer lines, and admits of less complication, it is probably to be preferred. It can be best introduced, perhaps, by the following explanation . In Fig, 293,^' d represents a prism standing upon a level base, h /, as an axis until it stands perpendicu- larly over p/, and at right angles to the plane, C ; then the plane, J, will lie over the plane, C, with the several lines on one corres- ponding to those on the other ; the point, i, resting at /, the point, ^^, at x^ and g at j ; and the curve, g n i, lying perpendicularly over b s c — as was required. If we suppose the cylinder to be cut by a level plane passing through the point, Z, (as is done in finding a face-mould,) it will be obvious that lines corresponding to Q'/ and jo/ would meet in / ; and the plane of the section. A, the plane of the segment, B, and the plane of the base, C, would all meet in that point. 393. — To find the face-mould for a limid-rail according to the principles explained in the previous article. In Fig. 295, a e cf is the plan of a hand-rail over a quarter of a cylinder ; and in Fig. 296, a b c d is the falling-mould ; / e being equal to the stretch-out of a df in Fig. 295. From c, draw c A, parallel to ef; bisect h c in i, and find a point, as 6, in the arc, df {Fig. 295.) corresponding to i in the line, h c; from i, {Fig. 296,) to the top of the falling-mould, draw i j, at right angles to Ac; at Fig. 295, from c, through 6, draw c g, and from b and c, draw bj and c k, at right angles to ^ c ; make c k equal io h g at Fig. 296, and bj equal to ij at that figure ; from k, through j, draw k g, and from^, through a, drsiw g p ; then ^p will be the intersecting line, corresponding to/m in Fig. 293 and 294 ; through e, draw p 6, at right angles to g j^, and from c, draw c q. parallel to g p ; make r q equal to h g at Fig. 296 ; join p and q^ and proceed as in the previous examples to find the face-mould, A. The joint of the face-mould, u v, will be more accurately determined by finding the projection of the centre of the plan, o, as at w ; joining 5 and w^ and drawing ii v, parallel to s w. It may be noticed that c k and b j are not of a length corres- ponding to the above directions : they are but^ the length given. iiiAlRfe. 24S Fig. 295. 246 AMERICAN H0r5'Ji'''?ARPENTEIl. Fig. 296. The object of drawing these lines is to find the point, g-, and that can be done by taking any proportional parts of the lines given. as well as by taking the whole lines. For instance, supposing c k and h j to be the full length of the given lines, bisect one in i and the other in m; then a line drawn from m, through i, will give the point, g, as was required. The point, g, may also be STAIRS. 247 obtained thus : at Fig. 296, make h I equal to c 6 in Fig. 295 ; from Z, draw I k, at right angles to h c ; from 7, draw^* k, parallel to A c ; from g, through k, draw g n; at Fig. 295, make b g equal io In in Fig. 296 ; then g will be tlie point required. The reason why the points, a, b and c, in the plan of the rail a^ Fig. 295, are taken for resting points instead of e, i and/, is this : the top of the rail being level, it is evident that the points, a and e, in the section a e, are of the same height ; also that the point, i, is of the same height as 6, and c as/. Now, if a is taken for a point in the inclined plane rising from the line g ;:>, e must be below that plane ; if b is taken for a point in that plane, i must be below it ; and if c is in the plane,/ must be below it. The rule, then, for taking these points, is to take in each section the one that is nearest to the line, g p. Sometimes the line of intersection, g p, happens to come almost in the direction of the line, e r : in such case, after finding the line, see if the points from which the heights were taken agree with the above rule ; if the heights were taken at the wrong points, take them according to the rule above, and then find the true line of intersection, which will not vary nmch from the one already found. Fig. -297. 394.— To appl]/ the face-mould thus found to the plank. The face-mould, when obtained by this method, is to be applied to a square-edged plank, as directed at Art. 383, with this differ- ence : instead of applying both tips of the mould to the edge of 248 AMERICAN HOUSE-CARPENTER. the plank, one of them is to be set as far from the edge of the plank, as x^ in Fig. 295, is from the chord of the section p q — as is shown at Fig. 297. A. in this figure, is the mould applied on the upper side of the plank, i5, the edge of the plank, and C, the mould applied on the under side ; a b and c d being made equal to q X in Fig. 295, and the angle, e a c, on the edge, equal to the angle, p q r, at Fig. 295. In order to avoid a waste of stuff, it would be advisable to apply the lips of the mould, e and 6, im- mediately at the edge of the plank. To do this, suppose the moulds to be applied as shown in the figure ; then let A be re- volved upon e until the point, 6, arrives at g^ causing the line, e b, to coincide with eg: the mould upon the under side of the plank must now be revolved upon a point that is perpendicularly beneath e, as /; from/, draw / A, parallel to i d. and from (/, draw d A, at right angles to i d ; then revolve the mould, C, upon /, until the point. A, arrives at J, causing the line,/ A, to coincide with/^', and the line, i d, to coincide with k I j then the tips of the mould will be at k and I. The rule for doing this, then, will be as follows : make the an- gle, ^/A', equal to the angle q v x, at Fig. 295 ; make /A' equal to/i, and through A-, draw k /, parallel to ij ;. then apply the corner of the mould, i, at /r, and the other corner c?, at the line, k I. The thickness of stuff is found as at Art. 381. 395. — To regulate the application of the falling-mould. Obtain, on the line, h c, [Fig. 296,) the several points, r, q,2h I and m, corresponding to the points, J^, a^^ z^ y, &c., at Fig. 295 ; from r q Pj (fee, draw the lines, r t, q ii, p v, (fee, at right angles to he; make A .«?, r t, q u, &c., respectively equal to 6 c"; r q, 5 d', &c., at Fig. 295 ; through the points thus found, trace the curve, s w c. Then get out the piece, g s c, attached to the fall- ing-mould at several places along its length, as at z, z, z, &c. In applying the falling-mould with this strip thus attached, the edge, sw c, will coincide with the upper surface of the rail piece STAIRS. 249 before it is squared ; and thus show the proper position of the fall ing-mould along its whole length. (See Art. 403.) SCROLLS FOR HAND-RAILS. 396. — General rule for finding the size a7id jjosition of the regulating square. The breadth which the scroll is to occupy, the number of its revolutions, and the relative size of the reguJa ting square to the eye of the scroll, being given, multiply tlie number of revolutions by 4, and to the product add the number of times a side of the square is contained in the diameter of th^ eye, and the sum will be the number of equal parts into which the breadth is to be divided. Make a side of the regulating square equal to one of these parts. To the breadth of the scroll add one of the parts thus found, and half the sum will be the length of the longest ordinate. 6 5 8 I- 4 1 Fiff. 298. 397. — To find the proper centres in the regulating square. Let a 2 1 6, {Fig. 29S,) be the size of a regulating square, found according to the previous rule, the required number of revolu- tions being If. Divide two adjacent sides, as a 2 and 2 1, into as many equal parts as there are quarters in the number of revo- lutions, as seven ; from those points of division, draw lines across the square, at right angles to the lines divided ; then, 1 being the first centre, 2, 3, 4, 5, 6 and 7, are the centres for the other quar- ters, and 8 is the centre for the eye ; the heavy lines that deter- 32 250 AMERICAN HOUSE-CARPENTER. mine th«se centres being each one part less in length than its pre- ceding line. ^ M Fig. 299. 398. — To describe the scroll for a hand-rail over a curtail step. Let a b, (Fig. 299,) be the given breadth. If the given number of revolutions, and let the relative size of the regulating square to the eye be ^ of the diameter of the eye. Then, by the rule, If multiplied by 4 gives 7, and 3, the number of times a side of the square is contained in the eye, being added, the sum is 10. Divide a 6, therefore, into 10 equal parts, and set one from b to c ; bisect a c in e ; then a e will be the length of the longest ordinate, (1 c/ or 1 e.) From a, draw a d, from e, draw e 1, and from b, draw 6/, all at right angles to a b ; make e 1 equal to e a, and through 1, draw 1 d, parallel to a b ; set b c from 1 to 2, and upon 1 2, complete the regulating square ; divide this square as at Fig. 298 ; then describe the arcs that compose the scroll, as follows: upon 1, describe d e; upon 2, describe e f; upon 3., describe/^ ; upon 4, describe g A, &c. ; make d I equal to the STAIRS. 251 width of the rail, and upon 1, describe Im ; upon 2, aescribe m w,