1>:> %j&*^Hi> ' : > 3> ^> y~ > : I> >; > > :> J> > .> ^ > > UNIVERSITY OF CALIFORNIA. (j^f l^eceiyeil cr^/r. , ^5- / f <^' Accession No. / y ^ / <3 ^"/.-/SN ,Vo. s . ' ) - . > v;! ^ > j ' > $^ >> > > :> > > , ' . >v > "> > > o j - O ^> "^ ^- : x> & > >. > > > > >>' .> S) >> ^>.-->: > ^ * N^-kX "^ ' ' 3E> ;> > ^ ^ >^>- > >y:> > > P^ >2>^ > ^ > 3 _> > } > > > : ::.> ^ > ^ >^> ^^ > >><>;> > > ->^ -/>^ ^ j .:>' i> )3 > > > > X_> J> J > ;> ^^ ' >' >l ">) J>> '^^ &^- > ' > J -^ ai 3&: _ } v>>"> ->~V: . > > > > ^B :> :> > > > :? >-O ^> :>'*> :> :>>."> vS '->>*> >-o. jj> :> . >- 5 --^ x- .'3 ^O >:> ->y5> ,> >..x^ :> > *x> *!> > >~>~> . >:> >3 j> j> J> ;> 5 ^~ ^>" J^a > I> _J -> > >il5 :>- ^> "t::i> r> O 3>- "-> i- -> > ..^ > ^ >3>3J> J3 > > * ,"> _-^^.>_ _j> .^3>..-> :^ ; , ; > . J> ^?> J -> > S, S '*> '> > ^ 5 9 -* -l> -> ' * -^ ' J -> > J J *> i - ^^)^) 33Hv> -> *> > ^^ ^^ ^ '> 5 > ^ ^ >^'^H>-^S^a5 > 5 30 ) >> -5^> 3 ) ^ > ;>>2 5>>"> \ vi>^ ' > 50 ^> >> -30-T>->3 3)J>-> ^ ^^ o )S5 5S5 "> ^-^ ^> 3>3 >>-> 5 > > > )J5 > ^ J 3 -->.>^ :> J > ^ o>9> - ~)^i > '>- > > > > ^>^> -? J >-> ^ ^Ti> ^ 5 1>' : "> ^ ) > 3 %?> > -3) > ^ ^ >>^ p V >', ^ ^)>4;/ * y 5 ) >>^ ^ :^ ,->J>'-> 3 >:>> > -* ^ Sr ^>i ->> i > ^? > ? 5J> ^> s -> >at >3 >> a> > ^r^"^> ) > > 5 3H> :> ^ ^ ^ N ~* ^-^ '^^ ' T *" K^ ?]>!-> 3 1^' ^ ; :o/^- .^ >S>^ i-S- ^,; ^> *<*>*' 3 >v > ->y>w "> "> *'S& 3 > )> i ^>> 5 5H&3 3 >S.3^3 - ? s*^ >^ ^r ,<;< < <: "- j ->, ^ j>> > -> ->^>> ->^> *> - EMBRACING THE PRINCIPLES OF CONSTRUC- TION AS APPLIED TO PRACTICAL DESIGN WITH NUMEROUS ILLUSTRATIONS OF TOPOGRAPHICAL, MECHANICAL, ENGINEERING, ARCHITECTURAL, PERSPECTIVE, AND FREE-HAND DRAWING EDITED BY W. E. WORTHEN, C. E. OF 1 UN: NEW YORK D. APPLETON AND COMPANY 1896 COPYRIGHT, 1885, 1896, BY D. APPLETON AND COMPANY. PREFACE. " AT the suggestion of the publishers, this work was undertaken to form one of their series of dictionaries and cyclopaedias. In this view, it has been the intention to make it a complete course of instruction and book of reference to the mechanic, architect, and engineer. It has not, therefore, been confined to the explanation and illustration of the methods of projec- tion, and the delineation of objects 'which might serve as copies to the draughtsman, matters of essential importance for the correct and intelligible representation of every form ; but it contains the means of determining the amount and direction of strains to which different parts of a machine or structure may be subjected, and the rules for disposing and proportioning of the material employed, to the safe and permanent resistance of those strains, with practical applications of the same. Thus, while it supplies numerous illustrations in every department for the mere copyist, it also affords suggestions and aids to the mechanic in the execution of new designs. And, although the arranging and properly proportioning alone of material in a suitable direction, and adequately to the resistance of the strains to which it might be exposed, would produce a structure sufficient in point of strength for the purposes for which it is intended, yet, as in many cases the disposition of the material may be applied not only practi- cally, but also artistically. . . . 1857." " There are no changes in the principles of projection as applied to drawing, and no marked improvement in drawing-instruments ; but in the present practice finished drawings in shade and colour are exceptional. It is sufficient, for almost every purpose, for the draughtsman to make accu- rate projections with pencil on paper, and trace them afterward on cloth. The pencil-drawings can be readily altered or amended, and, where there are many repetitions of the same parts, but a single one may be drawn. On the tracing they are made complete, and these are preserved as originals in the office, while sun-prints of them are used for details of construction in the shop, or distributed as circulars among customers. " Of late years the science of ' graphics ' has become of great impor- tance, and is here fully illustrated in its varied applications, showing not only this method of recording the facts of the statistician, and affording comparisons of circumstances and times, the growth of population, the iii IV PREFACE. quantities and cost of agricultural and mechanical production, and of their transport, movements of trade, fluctuations of value, the atmospheric con- ditions, death-rates, etc., but also in its application to the plotting of formulae for their ready solution, by the draughtsman and designer. For many of the rules in this work the results of the formulae of various authors have been plotted graphically, and the rule given one deemed of the greatest weight, not always by average, but most consistent with our own experience. " In astronomical calculations every decimal may have its importance. It is not so in those of the mechanical or architectural designer ; solutions by graphics are sufficient for their purpose, and, simpler than mathematical calculations, they are thus less liable to error ; it is a very good practice to use one as a check on the other. It is to be remarked that inaccuracy in facts, and carelessness in observation, are not eliminated from an equation by closeness of calculation, and when factors are not established within the limits of units it is useless to extend the results to many places of decimals. It is of the utmost importance to know at first well the object and pur- poses of the design, the stresses to which its parts are to be subjected, and the strength and endurance of the materials of which it is to be composed. In establishing rules for ourselves, be sure of the facts, and that there are enough of them for a general application. Rules are necessary, but their application and usefulness depend largely on the experience of the user, and life must be a record of applications and effects. It is comparatively easy to make a work strong enough ; but to unite economy with propor- tion is difficult. . . . 1886." The first edition of this work was suggested by " The Engineer and Machinist's Drawing Book " of Messrs. Blackie & Son, 1855, from which, with the consent of the publishers, much of the text and illustrations were taken. Since then, in the many editions, it has been the aim to keep up with mechanical progress, and matter has been drawn from all sources. Credit, as far as possible, has been given to mechanics for their designs and to experimenters for their results. Geometrical problems and examples of orthographic projection of the first work are largely retained, but examples of mechanical and archi- tectural construction are brought up to the present age of steel, with the latest illustrations of the applications of steam, and some of electricity. Isometry is retained, perspective has been more fully illustrated, and free- hand drawing now includes the recent processes by which, through pho- tography, the mechanical labour of sketching is diminished, adding to the correctness of detail and improving the effectiveness on paper. This may be called an age of illustration, and the processes have enabled a work like the present drawing book to give better and more illustrations, less text, more comprehensiveness, and greater certainty of detail. Mr. Robert E. Hawley, brought up in my office, has had charge of the new drawings and has acted as co-editor. AV. CONTENTS. PAGES. CONSTRUCTION OF GEOMETRICAL PROBLEMS 1-82 Drawing of lines straight, curved, perpendicular, and parallel : angles, ai'cs, and circles, 13. Triangles, polygons and circles, inscribed and described ; polygonal angles ; use of protractor, 21. Use of the triangle and square ; areas of figures ; scales, 25. Similar triangles, squares of proportionate sizes, 30. El- lipse, parabola, hyperbola, spiral, 35. Drawing-board, table ; straight-edges ; T-squares: parallel rulers ; curves, variable and adjustable; splines and weights ; thumbtacks; drawing pens; dotting instrument; compasses; dividers; plot- ting scales; protractors; sector; pantographs, 51. Drawing paper; tracing paper; tracing cloth ; heliographic paper ; damp stretching and mounting, 55. Use of instruments; representation of surfaces; enlarging and reduction of drawings ; designs in lines, 62. Lettering ; profile and cross-section paper, 77. Ornamental designs in straight and curved lines, 82. PLOTTING ....* 83-94 Scales ; plotting for surveys, plans and maps ; plotting by protractor, by lati- tudes and departures, by triangles, by offsets ; United States division of public lands, 94. TOPOGRAPHICAL DRAWING 95-120 Conventional signs ; representation of hills ; chart from United States Sur- vey, 102. Railway, 103. Hydrometrical chart, geological and section, 109. Transferring field notes, 110. Map projections, 116. Colored topography; pen and brush work, 119. Meridians and borders, 120. ORTHOGRAPHIC PROJECTION 121-146 Point ; straight line ; solid ; simple bodies : pyramid ; prism, 127. Conic sections, 130. Intersection of solids, 139. The helix, 141. Development of surfaces, 144. Shade lines, 146. SHADES AND SHADOWS 147-166 Shadow of a point, of a straight line, of a solid, of a pyramid, of a cylinder, of a hollow hemisphere; niche, 154. Lines of shade on sphere ; ring; grooved pulley ; screw, 159. Manipulation shades, surfaces in light, in shade by flat tints, by softened tints. Examples in plates. Conventional tints, 166. MATERIALS 167-185 Earth and rocks; woods, 170. Masonry, technical terms for; stones, gra- nitic, argillaceous, sand, lime, 174. Artificial building material ; brick, sizes of ; fire ; enamelled tile ; terra cotta, 175. Mortars ; concrete ; plastering ; weight of masonry, 177. Metals, conventional signs of, properties of; alloys, strength of, graphic representation by Prof. Thurston ; sulphur: glass; rubber; paints; coal ; flame, 185. v VI. CONTENTS. MECHANICS Force : centres of gravity ; mechanical powers ; parallelogram of forces ; toggle joint ; hydraulic press ; statics ; dynamics ; velocity of falling bodies, 196. Friction, 201. Mechanical work ; unit of force ; the force of animals, water, steam, and their application ; the steam-pressure indicator and cards, 211. Motion, example of the path of; parts of machines ; of the crank ; the Stanhope lever ; Whitworth's quick return ; parallel motion ; car coupler, 218 ; valve diagram ; Corliss cut off : link motion ; valve gear, 228. HAGES 186-228 MACHINE DESIGN AND MECHANICAL CONSTRUCTION Stress ; strain ; dead load ; factor of safety ; safe load of columns, cast and wrought iron ; shearing, torsional and transverse stress ; graphic diagrams, 239. Table of safe load on yellow-pine beams, on cast iron, on wrought iron, on steel ; box girders ; composite, 250. Bolts and nuts ; screws ; washers, 257. Shafts and axles, cast and wrought iron, 262. Pillow blocks ; standards ; hangers ; steps ; suspension and thrust bearings, 273. Couplings ; clutches, 282. Pulleys, wooden and iron plates ; cone, 287. Belts, plain, twist, and cross. Strength of rope driving, 299; chain driving; leather links, 301. Gearing, spur, rack, and pinion ; bevel. Form of teeth ; cycloid ; hypocycloid ; involute. 310. Diagram of stress on teeth ; diameter of pitch circle. Adcock's table of arcs for gear teeth ; mortise wheels, 316. Projections of a spur, bevel, and worm wheels ; screws, 330. Frictional and wedge gearing, 333. Blocks for running rigging ; chains ; chain couplings ; wire rope ; sockets ; hooks ; 337. Levers, cranks, 342. Eccentrics; wiper; stamp mill, 347. Connections, cot- ters, pins, rods, 348. Eccentrics and straps ; crossheads, 354. Working beam ; guide bars, 358. .Steam cylinders; pistons of pumps. Water pumps, 362. Wood and cup packing, 364. Steam jacket ; air chamber ; Thames Ditton pump ; Reidler ; Worthington, 366. The injector, 368. Clearances ; piston rods ; stuff- ing boxes, 370. Steam ports : Valves, cylindrical, balanced, automatic, disk, rubber, ball, poppet, flap, 376. Valves controlled by hand, cocks^ plug. Valves : compression, air, globe, gate, damper rotary, safety, 382. Hy- drants, 383. Riveted joints, 389. Boilers : tubular, marine ; water tube ; flue : locomotive, vertical, 398. Connections of steam and water pipes ; wrought- iron pipes ; couplings ; unions ; coils ; joints for submerged pipes, 406. Gov- ernor ; fly-wheels ; air chambers ; accumulators ; hydraulic press ; jack screw ; housings. 229-414 ENGINEERING DRAWING Foundations ; concrete base ; crib work ; New York dock ; Thames embank- ment ; breakwater ; screw piles ; masonry curbs ; steel caissons ; Poughkeepsie bridge pier ; pneumatic piles ; caissons and air lock ; freezing process, 435. Retaining walls, 436. Dams : earth, crib, masonry, 444. Gates : head, waste, 451. Canals, navigation, power. Locks of canals ; flumes and conduits, 459. Reservoirs ; sheet-iron pipe ; water tanks, 462. Water mains for city service ; specials ; inspection, 466. Sewers : brick, vitrified pipe, circular, egg-shaped, concrete, man-holes, 471. Gas supply, 472. Roads and highways ; street pave- ments : granite, asphalt, wooden, block, 479. Railroads ; road bed : rails ; elec- tric conduit, 483. Roofs and bridges ; principle of bracing ; frames, wooden, iron ; trestles, 498 ; truss bridges : wooden, iron, combination, 510. Turn ta- bles ; ferry-landing bridge ; high wrought-iron trestles ; masonry piers ; arch bridge, 522. Boiler setting, horizontal, tubular, 526 ; chimneys, 530. Loca- tion of machines ; foundation, 535. Tunnels : principles of timbering ; Hoo- sac ; bar timbering, 539. Railway rolling stock ; box car ; standard passenger ; locomotive frame, 545. Wave-line principle of ship construction, 547. 415-547 CONTENTS. vii PAGES ARCHITECTURAL CONSTRUCTION 548-693 Plans and elevations, 553 ; details of construction ; timber frames and floors, 561. Examples of fire-proofing, old, recent ; skeleton frames, fire-re- tarding construction of mills, 571 ; windows ; stairs ; doors. Fireplaces ; flues ; roofs ; gutters ; cornices, 587. Plastering ; mouldings, 590. Sizes of rooms ; water appliances and accessories ; Ferguson's rules of proportion ; de- signing of house ; illustration and details ; country and city, 609. Apartment houses ; store and warehouses ; machine-shop ; school-houses ; churches ; theatres; lecture rooms ; music and legislative halls; waves of sound; effect of air currents ; space for seats : ancient and modern churches ; organs ; 628. Theatres, dimensions of some, 630. Legislative halls, acoustic principles; hospitals ; stables ; cowhouses ; greenhouses, 634. Ventilation and warming ; stoves ; hot-air furnaces ; steam and hot water circulation, 647. Radiators ; laying out of pipes, 649. Plumbing ; soil pipe ; fixtures for kitchens ; baths ; water-closets ; traps and bends, 656. Lighting : gas, electric, wiring. Orders of architecture : Greek and Roman, Romanesque, Byzantine, Gothic, the Re- naissance. Arches ; domes and vaults ; buttresses ; towers ; bell cots ; spires, 674. Windows, lancet, traceried ; doorways, 679. Mouldings ; arch and architrave ; capitals ; bases ; string courses and cornices, 682. Ornaments, 693. ISOMETRICAL DRAWING ." . . . . . 694-705 PERSPECTIVE 706-725 Points and planes of perspective ; parallel and angular perspective of cubes and other solids, of buildings, of an arched bridge, of an interior, of a staircase, of reflection of objects in water, of shadows ; perspective as illustration of ad- vertisements. FREE-HAND DRAWING 726-764 Materials : paper, pencils, lithographic chalk, pens, ink. Proportions of Hu- man Frame, Geometrical drawings of, " Dictionnaire Raisone par Viollet le Due " and Dr. Rimmer's " Elements of Design." Half tones of photographs of plaster models, " ecorche " of wash drawing of flowers, etc., P. de Lohgpre. Pen and ink reproduction of photographs on plain salted paper, models "ecorche," Sandow, manikins, Venus de Milo, and Dumas. Pumping Station after Emer- son in toothpick and splatter work. Drawings on stipple paper or clayboard, Sal- vini and Venetian fete on the Seine. Pen and ink drawing, hands, feet, heads, Electioneer, Cow, Donkey from Landseer, hoofs, paws, muzzles, Espanola y Americana, Erik Werenskiold and design by Fortuny, Alexandrian pilot, Head of Sheik, Water Bearer, Donkey's Head, Deer, Ducks, Landscapes, Oak Trees, Morning, Cattle going Home, Lady of the Woods, Elm, Cedar, Sketch in chalk, Suez Canal and sea sketch. APPENDIX ...... 765-861 Patent office, Requirements for drawings and Registration of prints and labels. Mensuration, areas of surfaces, contents of solids ; measures, lineal, of surface ; of capacity ; liquid : dry. Weights, apothecaries', Troy, avoirdupois, compari- son of; Dynamic Table: cubic measure; shipping measure; register; ship- ping ; carpenter's rule. Table of inches and parts in decimals of a foot ; elec- trical units ; units of heat. Table of fifth powers of numbers ; weight of cast- iron balls, of cast-iron pipe, weights of rolled iron, 773 ; weight of wrought. Tables of dimensions and weight of wrought iron welded tubes ; nominal and actual diameters of boiler tubes. Heavy pipe for driven wells ; spiral riveted tubes, heavy and light ; weight of copper and brass rods ; rivets ; wrought spikes ; cut nails and spikes ; wire nails, weight of. Galvanized telegraph wire ; weights ; resistance in ohms ; sizes used. Standard Beams and Channels of Asso- vriii CONTENTS. PAGES ciation of American Steel Manufacturers ; grades of steel ; weights of lead pipe. Weight of a cubic foot of water at different temperatures. Flow of water, 781-791, over weirs, through pipes and conduits ; graphic diagrams of Kutter formulae. Table of equalizing the diameter of pipes ; flow of air ; comparison of flow of water by the Kutter diagrams, with that of air; with that of gas, and the products of combustion in chimneys. The Babcock and Wilcox boiler ; the Green economizer ; the Heine boiler. Table of saturated steam, 798; ex- pansive working of steam. Table of factors of evaporation. Electric Light and Power Station, Twenty-eighth Street, New York city, 805. Diagram of electric wiring ; lamp socket switch and Lundell motor ; Table of the density of gases. Specific gravity of liquids, of earths, of woods, of metals, solders ; alloys. Table of the circumferences and areas of circles, 819. Tables of squares, cubes, and roots, 826 ; of reciprocals ; Latitudes and Departures, 835. Natural sines and cosines, 845. Logarithms, 861. SCRAPS 862-912 Compound steel cylinders ; manholes and covers ; compressed-air locomo- tive ; cranks ; rudder frame ; boiler flues ; screw propeller ; spherical bearing ; conventional signs of riveting ; mechanical stokers. Boilers : Stirling and Abendroth and Root. Engines Corliss stationary: Deane steam pump; Reidler valve ; Locomotives ; car springs ; elevated railroad ; cable grip ; der- rick. Dams: canvas, earth, masonry, movable; Builder's hardware; hinges; construction of safes. Mantels and fireplaces ; doors ; marquetry ; pediment ; brackets ; railing ; summer house ; windows ; doorways ; porches ; house fronts ; dormers and towers ; skeleton construction ; Broad Street Station, Philadel- phia. Church spires ; churches ; perspective ; buildings of Centennial Exhi- bition ; of World's Pair ; Coney Island. DESCRIPTION OF PLATES. I. Shading of prism and cylinder by flat tints. Page 160. II. Shading of cylinder and segment of hexagonal pyramid. Page 161. Ill, IV. Finished shading and shadows of different solids. Page 163. V. Shades and shadows on screws. Page 164. VI. Example of topographical drawing, done entirely with the pen. Page 101. VII. The same, with the brush, in black. Page 117. VIII. The same, with the brush, in colour. Page 118. IX. Contoured map of Staten Island, shaded by superimposed washes, the washes increasing in intensity or strength as required to pro- duce the effect. Page 117. X. Geological map of part of New Jersey, coloured to show the different formations. Page 106. XI, XII. Topographical maps of parts' of Massachusetts. XIII. Plan and ceiling in colour. Page 548. XIV. Perspective view of Gothic church, finished in colour. (Frontispiece.) XV. Front elevation of a building, in colour. XVI. Finished perspective drawing, with shades and shadows, of a large bevel- wheel and two pinions, with shifting clutches. Page 160. XVII. Plan, elevation, and section of bevel-wheel, pinion, and clutches, shown in perspective Plate XVI. Page 160. EEEATA. Page 160, 19th line, omit Plate XI, and for Plates XII and XV, substitute Plates XVI and XVII. APPLETONS' CYCLOPAEDIA OF DRAWING. CONSTRUCTION OF GEOMETRICAL PROBLEMS. MOST persons, at some time, have made use of the simple drawing instru- ments, as pencils, straight edges or rulers, dividers and compasses with change- able .points, and many suppose that there can be no skill in their use; but to one critical in these matters there are great differences, even in common draw- ings, in the straightuess and uniformity of the lines and in the care of the surface of the paper. Pencils are marked according to their hardness: H (hard), HH, H H H, to 8 H ; or H, V (very) H, V V H, M (me- dium), H M^ M B (black), S (soft), M S, V S, V V S ; or by numerals, 1, 2, 3, to 8. Select for the geometrical problems and for usual drawings a No. 3. or H H H pencil. It should be sharpened to a cone-point (Fig. 1). Where a pencil is used for drawing lines only, some draughtsmen sharpen the pencil to a wide edge, like a chisel. In drawing a straight line, hold the ruler firmly with the left hand ; with the right hand hold the pencil lightly but without slackness, and a little inclined in the direction of the line to be drawn, keeping the pencil against the edge of the ruler, and in the same relative position to the edge during the whole operation of drawing the line. 2 (1) FIG. 1. 2 CONSTRUCTION OF GEOMETRICAL PROBLEMS. To draw a clean line and preserve the point of the pencil, the part of the cone a little above the point of the pencil should bear against the edge of the ruler, and the pencil should be carried steadily while drawing. Any oscilla- tion will throw the point farther from or nearer the ruler, and the line will not be straight (Fig. 2). FIG. 2. In the use of the compasses do not make a hole through the paper with the needle or sharp point, but only into the paper sufficient to maintain the position. Keep the paper clean, and use rubber as little as possible. A geometrical point, which is position only, is indicated in drawing by the prick-mark of a needle or sharp point, or the dot of a pencil ; sometimes' it is inclosed 0, sometimes designated by the intersection of two short lines X >. A line, which is extension in length only, is indicated by a visible mark of pencil or pen traced upon the paper. Geometrically lines have but one dimension, length, and the direction of a line is the direction from point to point of the points of which the line is com- posed : in drawing, lines are visible marks of pencil or pen upon paper. A straight line is such as can be drawn along the edge of the ruler, and is one in which the direction is the same throughout. In drawing a straight line through two given points, place the edge of the ruler very near to and at equal distances from the points, as the point of the pencil or pen should not be in contact with the edge of the ruler (Fig. 3). FIG. 3. Lines in geometry and drawing are generally of limited extent. A given or known line is one established on paper or fixed by dimensions. Lines of the same length are equal. Curved Lines. For the pencil-points of compasses, whittle down the stumps of pencils to suit. Insert the pencil-point in the compasses. With the needle or sharp point resting on the paper describe a line with the pencil around this point ; the line thus described is usually called a circle more CONSTRUCTION OF GEOMETRICAL PROBLEMS. 3 strictly it is the circumference of a circle the circle being the space inclosed. A portion of a circumference is an arc. The point around which the circum- ference is described is the centre of the circle (Fig. 4). The line embraced between the two points of the compasses is called the radius of the circle, and by mechanics a sweep; a line passing through the centre and terminating at each end in the circum- ference is a diameter, and is equal in length to two radii ; any line not passing through the cen- tre and limited by the circumference is less than a diameter and is a chord. The space embraced between a chord and its lesser arc is a segment. The space embraced between two radii and its arc is a sector; if the arc is the quarter of the cir- cumference, the sector is distinguished as a quad- rant. It will be observed that arcs are lines which are continually changing the directions, and are called curved lines, but there are other curved lines than those described by compasses, of which the construction will be explained hereafter. Lines which can neither be drawn by rulers or compasses, representing the directions of brooks and rivers, the margins of lakes and seas, points in which are established by surveys, defined on paper, and connected by hand-drawing, are irregular or crooked lines. Where it is necessary to distinguish lines by names, we place at their extremities letters or figures, as A B, 1 2 ; the line A B, or 1 2. But in lines other than straight, or of considerable extent, it is often necessary to introduce intermediate letters and figures, as a a a. FIG. 4. In the following problems, unless otherwise implied or designated, where lines are mentioned, straight lines are intended. If a straight line moves sideways in a single direction, it will sweep over a surface which is called a plane. All drawings are projections on planes of paper or board. Two lines drawn on paper, and having the same direction, can never come any nearer each other, and must always be at the same distance apart, however far extended. Such lines are called parallel lines. To draw a line parallel to a given line, and at a given distance from it (Fig. 5). Draw the line A B for the given .line, and take in the compasses the distance A C the distance at which the other line is to be drawn. On A, as a centre, describe an arc, and on B, as a centre, a similar arc ; draw the line C D just touching these two arcs, which will be the parallel line re- quired. 4 CONSTRUCTION OF GEOMETRICAL PROBLEMS. To draw a line parallel to a given line through a given point outside this line (Fig. 6). Draw the given line A B, and mark the given point C. With C as a centre, find an arc that shall only just touch A B ; and with B as a centre, and the n FIG. 5. same radius, describe an arc D. Draw through the point C a line just touching this last arc, and the line C D will be the parallel line required. Two lines in the same plane, not parallel to each other, will come together if extended sufficiently far. The inclination or intersection of two lines is called an angle (Fig. 7). If but two lines come together, the angle may be designated by a single letter at the vertex, as the angle E. But, if three or more lines have a common vertex, the angles are designated by the lines of which they are composed, as the angle D B C of the lines 'D B and B C ; the angle A B C of A B and B C ; the angle A B D of A B and B D. The letter at the vertex must always be the central letter. Describe a circle (Fig. 8). Draw the diameter A B. From A and B as centres, with any opening of the compasses greater than the radius, describe two arcs cutting each other as at D. Through the intersection of these arcs and the centre C, draw the line D E. D E makes, with the diameter A B, four angles, viz., A C D, D C B, B C E, and EGA. Angles are equal whose lines Fid. 7. have equal inclination to each other, and whose lines, if placed one on the other, would coincide. By construction, the points C and D have, respectively, equal distances from A and B ; the line D C can not, therefore, be inclined more to one side than to the other, and the angle A C D must be equal to the angle BCD. Such angles are called right angles. The four angles, formed by the intersection of D E with A B, are equal, and are right angles. The angles A C D and D C B, on the same side of A B, are called adjacent angles ; as also DOB and B C E, on the same side of D E. CONSTRUCTION OF GEOMETRICAL PROBLEMS. 5 If the base line be parallel with the surface of still water, it is called an horizontal line, and the line perpendicular to it is called a vertical line. Draw the line C F. It will be observed that the angle F C B is less than a right angle, and it is called an acute angle ; the angle F C A is greater than a right angle, and it is called an obtuse angle. It will be observed that, no matter how many lines be drawn to the centre, the sum of all the angles on the one side of A B can only be equal to two right angles, and, on both sides of A B, can only be equal to four right angles. It will be observed that the angles at the centre in- clude greater or less arcs between their sides, according to the greater or less inclination of their sides to each other ; that the right angles intercept equal arcs, and that, no matter how large the circle, the proportion of the circle intercepted by the sides of an angle is always the same, and that the arcs can therefore be taken as the measures of angles. For this purpose the whole circumference is supposed to be divided into three hundred and sixty de- grees (360), each degree subdivided into sixty minutes (60'), and each minute into sixty seconds (60"). Each right angle has for its measure one quarter of the whole circumference (-^f^), or 90, and is called a quadrant. To construct an angle equal to a given angle (Fig. 9). Draw any angle, as C A B, for the given angle, and the line a b A FIG. 10. \\i k FIG. 11. as the base of the required angle. From A, with any suitable radius, describe the arc B C, and from a, with the same radius, describe the arc b c. With the compasses take the length of the chord B C, and, from b as centre, describe an arc cutting the arc b c at c, and draw the line a c; cab is the required angle. To construct an angle of sixty degrees (Fig. 10). Lay off any base line, and from A, with any radius, describe an arc, and from B, with the same radius, describe another arc cutting the first, as at C. Draw the line C A, and the angle CAB will be an angle of sixty degrees. f> CONSTRUCTION OF GEOMETRICAL PROBLEMS. For if, on the circumference of any circle, chords equal to the radius are stepped off successively, six will exactly complete the circle, making 360. To draw a perpendicular to a line from a point without the line (Fig. 11). Draw a line, and mark the given point A. From A as a centre, with a \F B A FIG. 12. FIG. 13. suitable radius, describe an arc cutting the line at G and F. From G and F, as centres, describe arcs cutting each other. The line drawn through the point A, and the point of intersection E, will be perpendicular to the line G F. The radial line A E divides the chord G F and the arc G E F into two equal parts ; and, conversely, the line perpendicular to the middle point of a chord of a circle is radial passes through the centre of that circle. To draw a perpendicular to a line from a point ivithin that line (Fig. 12). 1st Method. Draw a line, and take the point A in the line. From A, as a centre, describe arcs cutting the line on each side at B and C. From B and C, as centres, describe intersecting arcs at D. Draw a line through D and A, and it will be perpendicular to the line B C at A. 2d Method (Fig. 13). Draw the line, and mark the point A as before. From any centre F, without the line, and not directly over A, with a radius equal to F A, describe more than a half-circle cutting the line, as at D. From D, through the centre F, draw a line cutting the arc at E. Draw A E, and it will be the perpendicu- lar to the line A D. The line D E is the diameter of a circle, and the angle DAE, with its vertex at A in the circum- ference, embraces with its sides half a circle. It has been shown that angles at the centre of a circle have for their measure the arc embraced by their sides. Angles with their vertices in the circumference have for their measure half the arc em- braced by their sides; and, consequently, angles embracing half a circumfer- ence are right angles. To draw a perpendicular to the middle point of a line (Fig. 14). -B FIG. 14. CONSTRUCTION OF GEOMETRICAL PROBLEMS. f From the extremities A and B of the line, as centres, describe similar inter- secting arcs above and below the line. Through these intersections draw the line C D. It will be perpendicular to the line A B, and bisect or divide it into two equal parts. If the line A B be considered the chord of a circle, its centre would lie in the line C D. This construction is sometimes used merely to divide a line into two equal parts, or bisect it; it can be more readily done with dividers (Fig. 15). Place one point of the dividers on one end of the line, and open the dividers to a space as near as may be half the line. Turn the dividers on the FIG. 15. central point ; if the other point then falls exactly on the opposite extremity of the line, it is properly divided ; but, if the point falls either within or with- out the extremity of the line, divide the deficit or excess by the eye, in halves, and contract or extend the dividers by this measure. Then apply the dividers as before, and divide deficit or excess till a revolution exactly covers the length of the line. By accustoming one's self to this process, the eye is made accurate, and one estimate is sufficient for a correct division of any deficit or excess. By a similar process it is evident that a line can be divided into any number of equal parts, by assuming an opening of the dividers as nearly as possible to that required by the division, and, after spacing the line, dividing the deficit or excess by the required number of parts, contracting or expanding the dividers by one of these parts, and spacing the line again, and so on till it is accurately divided. To bisect a given angle (Fig. 16). Construct an angle, and from its vertex A, as a centre, describe an arc cutting the two sides of the angle at B and C. From B and C, as centres, de- FIG. 16. FIG. 17. scribe intersecting arcs. Draw a line through A and the point of intersection D, and this line will bisect the angle. To bisect an angle when the vertex is not on the paper (Fig. 17). 8 CONSTRUCTION OF GEOMETRICAL PROBLEMS. Let A B and E C be two lines inclined to each other ; at equal distances and parallel to the above lines draw a b and a c, intersecting lines; bisect -the angle b a c. A line a d drawn through the vertex and the point of bisection is the required line. Through two given points to describe an arc of a circle with a given radius (Fig. 18). From B and C, the two given points, with an opening of the dividers equal to the given radius, describe two arcs intersecting at A. From A, as a centre, with the same radius, describe an arc, and it will be the one required. FIG. 18. FIG. 19. To find the centre of a given circle, or of an arc of a circle. Of a circle (Fig. 19). Draw the chord A B. Bisect it by the perpen- dicular C D, whose extremities lie in the circumference, and bisect C D. Gr, the point of bisection, will be the centre of the circle. To find the centre of an arc (Fig. 20). Select the points A, B, and C in the arc, well apart. From A and B as centres, and then from B and C as centres, describe arcs of equal radii cutting each other ; draw the two lines D E and F G through their intersections. The point 0, where these lines meet, is the centre required. To describe a circle passing through three given points (Fig. 20). Proceed, as in the last problem, to find the point 0. From 0, as a centre, with a radius A, describe a circle, and it will be the one required. X T. FIG. 20. FIG. 21. To describe an arc of a circle passing through three given points, ivhere the centre is not available (Fig. 21). CONSTRUCTION OF GEOMETRICAL PROBLEMS. 9 From the extreme given points A and B describe arcs A E and B D ; through the third given point C draw lines from A and B, intersecting the arcs at and ; from and cut the arcs in either direction by equal divisions, 1, 2, 3, and 1', 2' ; draw lines A 1, A 2 ; A 1', A 2' ; B 1, B 2 ; B 1', B 2'. The successive intersections of A 1 by B 1, A 2 by B 2, A 1' by B 1' are points in the required arc by the connection of which the problem will be complete. To describe this arc mechanically (Fig. 22). Lay off on a piece of cardboard the three points A, C, B, and connect them by lines extended beyond the points A and B ; and then cut out the cardboard FIG. 22. along these lines. Insert pins at the points A and B on the drawing, and placing the cardboard templet against these pins, and the angle against the point C, slide the templet each way, dotting in the drawing the angle C in its different positions. These dots will be points in the curve, which are to be con- nected. By extending the bisecting line in different positions of the templet to the drawing, radial lines are given which will be useful in laying off voussoir joints on segmental arches of large radius. Kadial lines are also necessary in perspective drawing, for which an instrument called the centrolinead (Fig. 23) is used. The principle is similar to that of the cardboard templet. To draw a tangent to a circle from a given point in the circumfer- ence. 1st Method (Fig. 24). Through the given point A draw the radial line A C. The perpen- dicular F G to that line will be the tangent re- quired. FIG. 23. 2d Method (Fig. 25). From the given point A set off equal arcs, A B and A I>. Join B and D. Through A draw A E parallel to B D, and it will be the tangent required. This method is useful when the centre is inaccessible. 10 CONSTRUCTION OF GEOMETRICAL PROBLEMS. To draw tangents to a circle from a point without it (Fig. 26). From the given point A draw A C to the centre of the circle. Bisect A C to find the point D. From D, as a centre, describe an arc with a radius D C, A E FIG. 24. FIG. 25. cutting the circle at E and F. Draw A E and A F, and they will be the tan- gents required. To' construct within the sides of an angle a circle tangent to these sides at a given distance from the vertex (Fig. 27). FIG. 26. FIG. 27. Let a and b be the given points equally distant from the vertex A. Draw a perpendicular to A C at a, and to A B at b. The intersection of these per- pendiculars will be the centre of the required circle. In the same figure, to find the centre, the radius being given, and the points a and b not known. Draw lines parallel to A C and A B, at a distance equal to the given radius, and their intersection will be the centre required. To describe a circle from a given point to touch a given circle (Figs. 28 and 29). FIG. 28. FIG. 29. D E being the given circle, and B the given point, draw a line from B to the centre C, and produce it, if the point B is within the circle, until it cuts the circle at A. From B, as a centre, with a radius equal to B A, describe the circle F G, touching the given circle, and it will be the circle required. CONSTRUCTION OF GEOMETRICAL PROBLEMS. 11 In all cases of circles tangent to each other, their centres and their points of contact must lie in the same straight line. To draw tangents to two given circles (Fig. 30). Draw a straight line through the centres of the two given circles. From the centres A and B draw parallel radii, A D and B E, in the same direction. FIG. 30. Draw a line from D to E, and produce it to meet the centre line at C ; and from C draw tangents to one of the circles by Fig. 26. Those tangents will touch loth circles as required. To construct a circle through a given point tangent to a second circle at a given point (Fig. 31). Let A be the given point of a circle A D C, B the point through which the required circle is to be drawn. Connect A and B, extend A O, bisect A B by a perpendicular. The intersection of this perpendicular with A extended will be the centre of the required circle. The same method of construction would apply if the point B were inside the circle ADC. Between two inclined lines to draiv a series of circles touching these lines and touching each other (Fig. 32). Fm. 31. FIG. 32. Bisect the inclination of the given lines A B and C D by the line N ; this is the centre line of the circles to be inscribed. From a point, P, in this line, draw P B perpendicular to the line A B ; and from P describe the circle B D, touching the given lines, and cutting the centre line at E. From E draw E F perpendicular to the centre line, cutting A B at F ; from F describe an arc, with a radius F E, cutting A B at G ; draw G H parallel to B P, giving H the centre of the second touching circle, described with the radius H E or H G. By a similar process the third circle, I N", is described. And so on. Inversely, the largest circle may be described first, and the smaller ones in succession. 12 CONSTRUCTION OP GEOMETRICAL PROBLEMS. Note. This problem is of frequent use in scroll-work. Between two inclined lines to draw a circular arc to fill up the angle (Fig. 33). Let A B and D E be the inclined lines. Bisect the inclination by the line F C, and draw the perpendicular A F D to define the limit within which the circle is to be drawn. Bisect the angles A and D by lines cutting at C, Fio. 34. and from C, with radius C F, draw the arc H F G, which will be the arc required. To Jill up the angle of a straight line and a circle, with a circular arc of a given radius (Fig. 34). On the centre C, of the given circle A D, with a radius C E equal to that of the given circle plus that of the required arc, describe the arc E F. Draw G F parallel to the given line H I, at the distance G H, equal to the radius of the required arc, cutting the arc E F at F. Then F is the required centre. Draw the perpendicular F I, and the line F C, cutting the circle at A ; and, with the radius F A or F I, describe the arc A I, which will be the arc required. To fill up the angle of a straight line and a circle, ivitli a circular arc to join the circle at a given point (Fig. 35). In the given circle B A draw the radius to A, and extend it. At A FIG. 36. draw a tangent, meeting the given line at D. Bisect the angle A D E, so formed, with a line cutting the radius, as extended at F ; and, on the cen- tre F, with radius F A, describe the arc A E, which will be the arc required. CONSTRUCTION OF GEOMETRICAL PROBLEMS. 13 To describe a circular arc joining two circles, and to touch one of them at a given point (Fig. 36). Let A B and F G be the given circles to be joined by an arc touching one of them at F. (L r FIG. 37. FIG. 38. Draw the radius E F, and produce it both ways ; set off F H equal to the radius, A C, of the other circle ; join to H, and bisect it with the perpen- dicular L I, cutting E F at I. On the centre I, with radius I F, describe the arc F A, which will be the arc required. To find the arc which shall be tangent to a given point on a straight line, and pass through a given point outside the line (Fig. 37). Erect at A, the given point on the giv- en line, a perpendicular to the line. From C, the given point outside the line, draw C A, and bisect it with a perpendicular. The intersection of the two perpendiculars at a will be the centre of the required arc. To connect two parallel lines by a re- versed curve composed of two arcs of equal radii, and tangent to the lines at given points (Fig. 38). Join the two given points A and B, and divide the line A B into two equal parts at C ; bisect C A and C B by perpendiculars ; at A and B erect perpen- diculars to the given lines, and the intersec- tions a and b will be the centres of the arcs composing the required curve. To join two given points in two given parallel lines by a re- versed curve of two equal arcs, whose cen- tres lie in the parallels (Fig. 39). Join the two given points A and B, and divide the line A B in equal parts at C. Bisect A C and B C by perpendiculars ; the intersections a and b of the parallel lines, by these perpendiculars, will be the centres of the required arcs. CONSTRUCTION OF GEOMETRICAL PROBLEMS. On a given line, to construct a compound curve of three arcs of circles, the radii of the two side ones being equal and of a given length, and their centres in the given line ; the central arc to pass through a given point on the perpen- dicular, bisecting the given line, and to be tangent to the other two arcs (Fig. 40). Let A B be the given line, and C the given point. Draw C D perpen- dicular to A B ; lay off A a, B b, and C c, each equal to the given radius of the side arcs ; draw a c, and bisect it by a perpendicular ; the intersection of this line with the perpendicular C D will be the required centre of the central arc e C e'. Through a and b draw the lines D e and D e' ; from a and b, with the given radius equal to a A or b B, describe the arcs A e and B e'. From D, as a centre, with a radius equal to C D, and, consequently, by construction, equal to D e and D e', describe the arc e C e'. The entire curve A e C e' B is the compound curve required. PROBLEMS ON POLYGONS AND CHICLES. Three lines inclosing a space form a triangle (Fig. 41). If two of the sides are of equal length, it is an isosceles triangle (Fig. 42) ; if all three are of equal Fio. 41. FIG. 42. length, it is an equilateral triangle (Fig. 43). If one of the angles is a right angle, it is a right-angled triangle (Fig. 44), and if no two of the sides are of equal length, and not one of the angles a right angle, it is a scalene triangle. To construct an isosceles triangle (Fig. 42). Draw any line as a base, and, from each extremity as a centre, with equal radius, describe intersecting arcs. Draw FIG. 43. FIG. 44. a line from each extremity of the base to this point of intersection, and the figure is an isosceles triangle. To construct an equilateral triangle (Fig. 43). Draw a base line, and from each extremity as a centre, with a radius equal CONSTRUCTION OP GEOMETRICAL PROBLEMS. 15 to the base line, describe intersecting arcs. Draw lines from the extremi- ties of the base to this point of intersection, and the figure is an equilateral triangle. To construct a right-angled triangle (Fig. 44). Construct a right angle by any one of the methods before described. Draw a line from the extremity of the one side to the extremity of the other side, and the figure is a right-angled triangle. It will be evident, in looking at any right-angled triangle, that the side opposite the right angle is longer than either of the other or adjacent sides ; this side is called the hypothenuse. To construct a triangle equal to a given triangle ABC (Fig. 45). 1st Method (Fig. 46). Draw a base line, and lay off its length equal to A B; from one of its extremities, as a centre, with a radius equal to A C, describe an arc ; and, from its other extremity, with a radius equal to B C, describe an arc intersecting the first. Draw lines from the extremities to the point of intersection, and the triangle equal to A B C is complete. FIG. 45. FIG. 46. 2d Method (Fig. 47). Draw a base line, as before, equal to A B. At one extremity construct an angle equal to C A B, and at the other an angle equal to C B A. The sides of these angles will intersect, and form the required triangle. 3d Method (Fig. 48). Construct an angle of the triangle equal to any angle of A B C, say the angle A C B. On one of its sides measure a line equal to C A, and on the other side one equal to C B ; connect the two extremities by a line, and the triangle equal to A B C is complete. FIG. 47. FIG. 48. From the above constructions it will be seen that, if the three sides of a triangle, or two sides and the included angle, or one side and the two adjacent angles are known, the triangle can be constructed. Construct a triangle, ABC (Fig. 49). Extend the base to E, and draw B D parallel to A C. As A C has the same inclination to C B that B D has, the angle C B D is equal to the angle A C B. As A C has the same inclina- tion to A E that B D has, the angle D B E is equal to C A B. That is, the 16 CONSTRUCTION OP GEOMETRICAL PROBLEMS. two angles formed outside the triangle are equal to the two inside at A and ; and the three angles at B are equal to the three angles of the triangle, and their sum is equal to two right angles. Therefore, the sum of the three angles of a triangle is equal to two right angles. On one side of a triangle (Fig. 50) construct a triangle equal to the first. The exterior lines of the two triangles form a four-sided or quadrilateral figure, of which the opposite sides are equal and parallel, and the opposite an- FIG. 49. FIG. 50. gles equal. This figure is called a parallelogram, and the line C B, extend- ing between opposite angles, is a diagonal. On the hypothenuse of a right-angled triangle (Fig. 51) construct another equal to it, and the exterior lines form a parallelogram, which, as all the angles are right angles, is called a rectangle. If the four sides are all equal, it is called a square. A parallelogram in which all the sides are equal, but the angles not right angles, is called a rhombus (Fig. 52) ; if only the opposite sides are equal, it is FIG. 51. FIG. 52. called a rhomboid (Fig. 50) ; if only two sides are parallel, the figure is a trape- zoid (Fig. 53). Take any figure (Fig. 54) bounded by straight lines and from any interior point draw lines to all the angles. There will be as many triangles as sides, and the sum of the angles of the figure will be equal to as many times two right FIG. 53. FIG. 54. angles as sides less the four right angles at the centre, the sum of the angles of any triangle being equal to two right angles. If a line be drawn from the CONSTRUCTION OF GEOMETRICAL PROBLEMS. interior point to one side, another triangle is added to the collection and two right angles to the sum of the angles. Polygons are figures of many angles, which if equal and of equal sides are FIG. 55. FIG. 56. FIG. 57. FIG. 58. called regular polygons, and are designated by the number of their sides, as pentagons, hexagons, octagons, nonagons, decagons, etc. To describe a circle about a triangle (Fig. 59). Bisect two of the sides A B, A C, of the triangle at E, F ; from these points draw perpendiculars cutting at K. From the centre K, with K A as radius, describe the circle A B C, as required. To inscribe a circle in a triangle (Fig. 60). Bisect two of the angles A, C, of the triangle A B C, by lines cutting at D ; from D draw a perpendicular D E to any side, as A C ; and with D E as radius, from the centre D, describe the circle required. When the triangle is equilateral, the centre of the circle is more easily found by bisecting two of the sides, and drawing perpendiculars. Or, draw a perpendicular from one of the sides to the opposite angle, and from the side set off one third of the length of the perpendicular. To inscribe a square in a circle ; and to describe a circle about a square (Fig. 61). To inscribe the square. Draw two diameters, A B, C D, at right angles, and join the points A, C, B, D, to form the square as required. FIG. 60. FIG. 61. To describe the circle. Draw the diagonals A B, C D, of the given square, cutting at E ; on E as a centre, with E A as radius, describe the circle as required. 3 18 CONSTRUCTION OP GEOMETRICAL PROBLEMS. In the same way, a circle may be described about a rectangle. To inscribe, a circle in a square ; and to describe a square about a circle (Fig. 62). To inscribe the circle. Draw the diagonals A B, C D, of the given square, cutting at E ; draw the perpendicular E F to one of the sides, and with the radius E F, on the centre E, describe the circle. To describe the square. Draw two diameters A B, C D, at right angles, ( \ '/ x^ >*' X v - XL J; 1 F FIG. 62. 1 and produce them ; bisect the angle D E B at the centre by the diameter F G,. and through F and G draw perpendiculars A C, B D, and join the points A, D, B, C, where they cut the diagonals, to complete the square. To inscribe a pentagon in a circle (Fig. 63). Draw two diameters, A C, B D, at right angles ; bisect A at E, and from E, with radius E B, cut A C at F ; from B, with radius B F, cut the circum- ference at G and H, and with the same radius step round the circle. to I and K ; join the points so found to form the pentagon. To construct a regular hexagon upon a given straight line (Fig. 64). From A and B, with a radius equal to the given line, describe arcs cutting at g ; from g, with the radius g A, describe a circle ; with the same radius set FIG. 64. off from A the arcs A G, G F, and from B the arcs B D, D E. Join the points so found to form the hexagon. To inscribe a regular hexagon in a circle (Fig. 65). Draw a diameter, A B ; from A and B as centres, with the radius of the circle A C, cut the circumference at D, E, F, G ; draw straight lines A D, D E, etc., to form the hexagon. To describe a regular hexagon about a circle (Fig. 66). CONSTRUCTION OP GEOMETRICAL PROBLEMS. 19 Draw a diameter, A B, of the given circle. With a radius A D from A as a centre, cut the circumference at C ; join A C, and bisect it with the radius D E ; through E draw F G parallel to A C, and with the radius D F describe FIG. the circle F H. Within this circle describe a regular hexagon by the preceding problem ; the figure will touch the given circle as required. To construct a regular octagon upon a given straight line (Fig. 67). Produce the given line A B both ways, and draw perpendiculars A E, B F ; m I FIG. 68. E .- - -F bisect the external angles at A and B by the lines A H, B C, each equal to A B ; draw C D and H G parallel to A E and equal to A B ; and from the centers G, D, with a radius equal to A B, cut the perpendiculars at E, F, and draw E F to complete the octagon. To make a regular octagon from a square (Fig. 68). Draw the diagonals of the square intersecting at e ; from the corners A, B, C, D, with A e as radius, describe arcs cutting the sides at g h, etc. ; join the points so found to complete the octagon. To inscribe a regular octagon in a circle (Fig. 69). Draw two diameters, AC, B D, at right an- gles ; bisect the arcs A B, B C, etc., at e,/, etc. ; and join A e, e B, etc., for the inscribed figure. To describe a regular octagon about a circle (Fig. 70). 20 CONSTRUCTION OF GEOMETRICAL PROBLEMS. Describe a square about the given circle A B ; draw perpendiculars h k, etc., to the diagonals, touching the circle. Or, to find the points h, k, etc., cut the sides from the corners of the square, as in Fig. 68. To inscribe a circle within a regular polygon. When the polygon has an even number of sides, as in Fig. 71, bisect two FIG. 71. Fio. 72. opposite sides at A and B, draw A B, and bisect it at C by D E drawn between opposite angles ; with the radius C A describe the circle as required. When the number of sides is odd, as in Fig. 72, bisect two of the sides at A and B, and draw lines A E, B D, to the opposite angles, intersecting at C ; from C, with C A as radius, describe the circle as required. To describe a circle about a regular polygon. When the number of sides is even, draw two diagonals from opposite angles, like D E (Fig. 71),,, to intersect at C; and from C, with C D as radius, describe the cir- cle required. When the number of sides is odd, find the cen- tre C (Fig. 72) as in last problem, and, with C D as radius, describe the circle. For the construction of the regular polygons Fig. 73 will be found useful. Divide the interior circle into the number of degrees corresponding Fja 73 to the proportion of the sides of the polygon to the entire circle, e. g., -2-f -2- 72. With a radius of unity describe an exterior circle and extend radii through the divisions of the in- CONSTRUCTION OF GEOMETRICAL PROBLEMS. 21 terior circle. The chords of th^ arcs intersected correspond to the sides of the different polygons. The figure gives the polygons such as are usually found in practice, but a similar figure can be constructed increasing the number of sides as far as may be required. For the laying out of angles the protractor is used. In its simplest form it consists of a semicircle of metal or horn of which the edge is divided into 180 degrees. To lay off a given angle say 47 (Fig. 74) place the edge of the protractor, a 5, along the given line and make the centre of the protractor coincide with the vertex c of the angle to be laid off ; mark off on the edge the division 47, remove the protractor, and through this mark and the vertex c draw a line; the angle a c d will be equal to 47, and b c d to 133. These two are supplements of each other, or what each requires to make up the sum of 180. Fig. 75 represents the terms used in defining angles, and of which tables are given in the Appen- dix by which angles may be constructed without the use of the protractor. Considering BCD the angle, the perpendicular D H dropped from the radius at D and intersecting the diameter at II is the sine, the line B A perpendicular to B C and inter- secting the extended radius at A is the tangent, the extension of the radius C D to the intersection of the tangent at A the secant ; the versed sine is the line B II extending from the sine to the tangent. The cosine, cotangent, cosecant, and coversed sine are respectively the sine, tangent, secant, and versed sine of the angle D C F, the complement of B C D, having the number of degrees necessary to complete the quadrant of 90 degrees. FIG. 75. 22 CONSTRUCTION OF GEOMETRICAL PROBLEMS. USE OF TKIANGLE AND SQUARE. Right-angled triangles constructed of wood, hard rubber, celluloid, or metal are very useful in connection with a straight-edge, or ruler, in drawing lines parallel or perpendicular to other lines. To draw lines parallel to each other, place any edge of the triangle in close contact with the edge of the ruler. Hold the ruler (Fig. 76) firmly with the FIG thumb and little finger of the left hand, and the triangle with the other three fingers ; with a pencil or pen in the right hand, draw a line along one of the free edges of the triangle ; withdraw the pressure of the three fingers upon the triangle, and slide it along the edge of the ruler, keeping the edges in close contact ; a line drawn along the same edge of the triangle, as before, will be parallel to the first line. If the edge of the hypothenuse of the triangle be placed in contact with the ruler, lines drawn along one edge of the triangle will be at right angles to those drawn along the other. Through a given point to draw a line parallel to a given line (Fig. 77). Place one of the shorter edges of the triangle along the given line A B, and bring the ruler against the hypothenuse ; slide the triangle up along the edge of the ruler until the upper edge of the ruler is sufficiently near to the given point C to allow a line to be drawn through it. Draw the line, and it will be parallel to A B. If the triangle be slid farther up along the edge of the ruler, and a line be CONSTRUCTION OF GEOMETRICAL PROBLEMS. 23 drawn through C along the other edge of the triangle (Fig. 78), this line will be perpendicular to A B. If the triangle be slid still farther up along the FIG. 77. edge of the ruler, and a third line be drawn touching A B, the figure con- structed will be a rectangle ; and if E D be laid off on A B, equal to C E, the figure inclosed is a square (Fig. 79). It will be seen that the triangle and ruler afford a much readier way of C C f-\ f-\ A ,0, B A , ^-X- te E D B _X FIG. 78. FIG. 79. drawing parallel lines, and lines at right angles, than the compasses and ruler, and may be used in solving the following problems : The area of a figure is the quantity of space inclosed by its lines. Construct a right angle (Fig. SO). Divide the base and the perpendicular by dividers into any number of equal spaces ; for instance, ten on the one and five on the other. Construct a rec- tangle with this base and perpen- dicular, and through the points of division lay off lines parallel to the base and perpendicular. The rectangle will be divided into fifty equal squares, and its FIG. 80. CONSTRUCTION OF GEOMETRICAL PROBLEMS. measure in squares will be the divisions ten in the base, multiplied by the five in the perpendicular. If the division were inches, then the area of this rec- tangle would be fifty square inches; if feet, then fifty square feet. If there D Fio. 81. FIG. 82. were but five divisions in the base and five in the perpendicular, the surface would be twenty-five squares. Therefore, a rectangle has for its measure the base multiplied by its adjacent side or height. Draw a diagonal, and the rectangle is divided into two equal triangles. Each triangle must therefore have for its measure the base multiplied by half the perpendicular, or, as is usually said, by half the altitude. Take any triangle (Fig. 81), and from its apex draw a line perpendicular to the base. The triangle is divided into two right-angled triangles, which must have for their measure A D X i C D, and D B X i C I), and the sum of the two must be A B X i C D. If the perpendicular from the apex falls outside the triangle (Fig. 82), then the triangle B D C and ADC will have for their measure B D X \ C D and A D X \ C D, consequently their difference, ABC, must have for its measure A B X \ C D. Any polygon can be divided into trian- gles (see Fig. 54), and its area is made up of the sum of the areas of the triangles. By graphic con- struction the sum of the areas of the different triangles composing a polygon may be resolved readily into a single triangle and its area taken. For instance, take a six- sided polygon (Fig. 83), draw a line from A to C, and a line parallel to A C, at B intersecting the extended base at B', a diagonal drawn from A to B' will give one side of the triangle ; draw a diagonal from A to E, extend the side E D of the polygon indefinitely, draw a line at F parallel to A E, and intersect the extended side at e, draw the line A D and a parallel to this at e, intersecting the extended base at E'. A di- agonal drawn from A to E' will, with the side previously obtained and the base, give a triangle equal in area to the polygon. FIG. 83. CONSTRUCTION OF GEOMETRICAL PROBLEMS. 25 i g SCALES. The distances given in Fig. 80 may represent feet, yards, miles, or any other unit of measure. Thus, if they represent miles, the figure represents an area of fifty square miles. With a scale of equal parts, each part may represent any unit of measure, and a drawing on paper to that scale represents the object from which it is drawn in a reduced form, from which measures in detail by the scale may be more readily and as accurately taken as from the natural ob- ject in the shop or on the estate, and if de- signs are made to a scale they can be exe- cuted conformably and accurately in all their parts in either enlarged or reduced size. Practically a two-foot rule, with its divis- ions into inches, halves, quarters, eighths, and sixteenths, may be made use of as a scale of equal parts, any division being taken as the unit to represent a foot, a yard, or a mile ; but among drawing instruments scales especially adapted to the purpose are found in great variety of forms, divisions, and material. Fig. 84 represents a convenient form of scale, as it contains, in addition to the simply divided scales, a protractor along its edges. The simply divided scales consist of a series of equal divisions of an inch, which are num- bered 1, 2, 3, etc., beginning from the second division on the left hand ; the upper part of the left division in each is subdivided into twelve equal parts, and the lower part into ten equal parts. The scales are marked at the left 1 inch, , , , and when used in drawing the scale is written as I inch, f , , or inch to a foot, rod, or mile, or whatever may be the unit of actual measure. When the unit is the inch the first scale will be full size, the second f, the third , and the fourth full size. If the scale adopted is such a part of an inch to the foot, then the upper subdivisions will represent inches. Above the simply divided scales there is a scale marked C, which is a scale of chords; taking a radius equal to C-60, the chords of the different angles are represented by the division ; thus an angle of 20 the chord will be C-20. - at OUT \ s Fia. 84. CONSTRUCTION OP GEOMETRICAL PROBLEMS. SIMILAR TRIANGLES. Triangles which are equiangular are similar, and have their homologous sides that is, their sides adjacent to the equal angles proportional ; conversely, two triangles which have their homologous sides proportional are equiangular. Two triangles which have their sides parallel (Fig. 85) or perpendicular to FIG 85. FIG. 86. each other (Fig. 86) are similar. A line c drawn parallel to one side c' of a triangle (Fig. 87) forms a triangle a c b whose sides are proportional to the original triangle. In Fig. 88 a polygon is divided into triangles by lines from an interior point to its angles and these lines intersected by lines parallel to the sides of the polygon. The figure thus constructed is a polygon similar to the original polygon composed of triangles similar to the triangles into which it was divided. In the figure the parallel lines are drawn across the sides of the triangles at one half their length, and the areas of the small triangles are therefore equal to the square of one half or to one quarter that of the original triangles ; conse- quently the area of the interior polygon is one quarter that of the exterior one. As this construction obtains at any intersecting length, it affords a means of reducing the scale of the original polygon. To a scale of inch (Fig. 89) lay off a line and divide from by equal units to 6 ; at 6, with a radius equal to 6 on scale ( inch), describe an arc, and from with a scale of f inch, with a radius equal to 6, intersect the previous arc. Complete the triangle through this intersection, and draw lines parallel to 6, 6' through the divisions of the CONSTRUCTION OF GEOMETRICAL PROBLEMS. 27 first line ; the triangle will be divided into six similar triangles of which the homologous sides are proportional and represented on their different scales by the same number of units. FIG 89. Fig. 90 illustrates the application of scales to the measurement of lines which are inaccessible. Thus the lines a b and a c, with their inclosed angle, can be measured, and, if plotted to any scale, the line c b can be measured on the same scale. The height of an object may be obtained by the application of similar tri- angles, or by the length of the shadow cast, which is merely another applica- tion of the same method. The observer measures off, say, 60 feet from a flag pole (Fig. 91), and a rod is held at, say, 12 feet from the observer; a sight is then taken to the top and bottom of the flag pole at the 60-feet distance, and the points at which the sights intersect the rod are found to be 10 feet apart. Then by construction the height of the flag pole is found by scale to be 50 feet. By means of shadows, if the length of the shadow is found to be 40 feet and the shadow cast by a 10- foot rod is 8 feet, then by plotting the height is found, as before, 50 feet. The value of the above solution of geometrical problems depends on the accuracy of the drawing. To construct a square equal to one half of a given square (Fig. 92). Let a b c d be the given square, and draw diagonals in it. The square, e b f d, constructed on one half of one of these diagonals, will be equal to one half the' given square. FIG. 91. To construct a -square equal to double a given square (Fig. 93). Construct a square on one of the diagonals in the given square, or inclose the square with parallels to the diagonals of the square. 28 CONSTRUCTION OF GEOMETRICAL PROBLEMS. To construct a square equal to three times a given square (Fig. 94). Extend the base of the given square to the length of its diagonal. Draw a line from the point at which this line ends to the extreme angle of the square, and upon this line erect a square, which will be the square required. For a square four times the size of a given square, make the base double that of the given square. FIG. 94. To construct a square equal to five times a given square (Fig. 95). Extend the base of the given square, making the extension to d e equal to c d. From e draw a line to #, and on this line construct a square, which will be the square required. FIG. 95. Assuming the side of the given square in Figs. 92, 93, 94, and 95 to be the radius (or diameter) (Fig. 96) of a given circle, then the side of the square to be constructed half, twice, three, four, or five times the size of the given square will be the radii (or diameters) of the circles half, twice, three, four, or five times the size of the given circle. CONSTRUCTION OF GEOMETRICAL PROBLEMS. 29 It will be seen by Fig. 93 that the square constructed on the diagonal of a square is equal to double that of the original square. FIG On any right-angled triangle A C B (Fig. 97) let fall a perpendicular from the vertex of the right angle to the hypothenuse A B ; the triangle will be divided into two similar triangles, similar to each other and to the original triangle, and AD:AC::AC:AB; that is, A C 2 = A D X A B ; BD:BC::BC:AB; that is, B C 2 = B D X A B. AD-(-BD = AB, and the sum of the two equations is A B 2 = A C 8 + BC 2 . Therefore the square constructed on the hypothenuse of a right-angled triangle is equal to the sum of the squares of the other two sides (Fig. 98). To determine how much is added to a given square by extending its base and constructing a square thereon (Fig. 99). Let a represent the side C D of the given square. The area of the square is a X a or a 2 . Extend the side C D by a length, D G, represented by b. Then the new FIG. 97. 30 CONSTRUCTION OP GEOMETRICAL PROBLEMS. square (a -\- b) X (a + b) will be made up of the old square, or a 2 , and two rec- tangles, D G E H and P E K L, or 2 (a X b) or 2 a b, and one square, E H K J, b X b, or b 2 . The area To determine how much is taken from the area of a given square, by reducing its base and constructing a square (Fig. 99). Let a represent C G, the side of the given square. FIG. 99. Reduce C G, the length G D, represented by b. The new square (a b) s is the given square, or a 2 , diminished by two rectangles, D G J K and P L J H, or 2 a b excepting one square, E H J K, b X b or -f- b 2 . The area (a b) 2 = a*-2ab + b 2 . The last two constructions, in default of a table of squares, may often be found of use. CONSTRUCTION OF THE ELLIPSE, PARABOLA, HYPERBOLA, AND SPIRAL. An ellipse is an oval-shaped curve (Fig. 100), in which, if from any point, P, lines be drawn to two fixed points, F and F', called foci, their sum will always be the same. The line A B pass- >_ ing through the foci is the major axis, and the perpendicular C D at the centre of it is the minor axis. To construct an ellipse, the axes being known (Fig. 100). 1st Method. Let the two axes be the lines A B and C D. From C as a centre, with a radius equal to E B (half the major axis), de- scribe an arc cutting this axis at two points, F and F', which are the foci. Insert a pin in each of the foci, and loop a thread upon them, so that, when stretched by a pencil CONSTRUCTION OF GEOMETRICAL PROBLEMS. 31 FIG. 101. inside the loop, the point of the pencil will coincide with C. Move the pencil round, keeping the loop evenly stretched, and it will describe an ellipse. This construction follows the definition above given of an ellipse, that the sum of the distances of every point of the curve from the foci is equal. It is seldom used by the draughtsman, as it is difficult to keep a thread evenly stretched ; but for gardeners, laying out beds or plots, it is very convenient and sufficiently accurate. There are many forms of ellipsographs for drawing ellipses, and various sizes of ellipses in hard wood and rubber on sale. Pattern-makers usually lay out ellipses by means of a trammel (Fig. 101), which consists of a rectangular cross, with guiding grooves in which movable rods at- tached to sliders on a bar are fitted, so as to move easily and uni- formly. In describing an ellipse place the trammel with its grooves on the lines of the axes with the bar on the line of the major axis ; set the pencil or marker on the extremity of this axis, and slip the outer rod to the crossing of the grooves and clamp it to the bar. Now slide the rod down the minor axis, and, with the pencil at the extremity of this axis, clamp the intermediate rod to the bar at the crossing of the guides. Revolve the bar, the intermediate rod fol- lowing the major-axis groove, and the extreme rod that of the minor axis, and the pencil will describe the ellipse. Light trammels are made for the use of draughtsmen, but, as the necessity of drawing el- lipses is not frequent, it can be readily done by the use of a strip of cardboard (Fig. 102). Lay off the major and minor axes on the pa- per ; these represent the grooves of the trammel. Now take a strip of card- board with a straight edge, lay it along the line of the maior axis, and mark the FIG. 102. J . positions a at the extremity of this axis, and c at the crossing of the axes ; place the mark a on the ex- tremity of the minor axis, and mark on the edge of the card at b the cross- ing of the axes. Revolve the card as described for the trammel, mark the posi- tions of a by points, and connect them for the curve. To construct an approximate semi-ellipse by means of Jive arcs of circles. Let A B (Fig. 103) be the major axis, and D the semi-minor axis. Draw the semicircles A C B and d D a". Divide these semicircles into equal parts 32 CONSTRUCTION OF GEOMETRICAL PROBLEMS. by the radial lines e, Of, e', Of. From the points of intersection of these radial lines with the semicircumference draw g b, h a, h' a', g' b', parallel to the major axis. From e,f, e',f, intersections of the radial lines with the semicircumference A C B, draw e b, fa, e' a', and f V parallel to the minor axis. The intersections of these lines with b g, a h, etc., will be points on the ellipse. Now through the three points a, D and a' construct an arc of a circle. Connect a and b with a chord, bisect it with a perpendicular ; where this per- pendicular intersects a S at c is the centre of the , arc a b. Connect b and c; d, the intersection of b c with A B, will be the centre of the arc b A. Arcs through a' b' and B can be con- structed in the same way, or the centres can be transferred. The ellipse can in the same way be made up of any number of arcs of circles. To draw a tangent to an ellipse through a given point in the curve (Fig. 104). CONSTRUCTION OF GEOMETRICAL PROBLEMS. 33 From the given point T d raw i straight lines to the foci, F, F' ; produce F T beyond the curve to c, and bisect the exterior angle c T F' by the line T d. This line T d is the tangent required. To draw a tangent to an ellipse from a given point without the curve (Fig. 105). From the given point T as a centre, with a radius equal to its distance from the nearest focus F, describe an arc ; from the other focus F', with the major axis as radius, cut the arc at K, L, and draw K F', L F', touching the curve at M, N ; then the lines T M, T N, are tangents to the curve. The Parabola. The parabola may be defined as an ellipse whose major axis is infinite ; its characteristic is that every point in the curve is equally distant from the direc- trix E N and the focus F (Fig. 106). To construct a parabola when the focus and directrix are given. 1st Method (Fig. 106). Through the focus F draw the axis A B perpendicular to the directrix E N, and bisect A F FIG. 106. FIG. 107. at e, the vertex of the curve. Through a series of points, C, D, E, on the di- rectrix, draw parallels to A B ; connect these points, C, D, E, with the focus F, and bisect by perpendiculars the lines F C, F D, F E. The intersections of these perpendiculars with the parallels will give points, C', D', E', in the curve, through which trace the parabola. 2d Method (Fig. 107). Place a straight-edge to the directrix E N, and apply to it a square LEG; fasten at G- one end of a cord, equal in length to 4 34 CONSTRUCTION OF GEOMETRICAL PROBLEMS. E G ; fix the other end to the focus F ; slide the square steadily along the straight-edge, holding the cord taut against the edge of the square by a pencil, D, and it will describe the curve. To construct a parabola when the vertex, the axis, and a point of the curve are given (Fig. 108). Let A be the vertex, A B the axis, and D the point in the curve. Con- struct the rectangle A B D C ; divide D C into, say, four equal parts at 123, and A C into the same number at 1' 2' 3' ; draw diagonals, A 3, A 2, A 1 ; and parallels to the axis through 1' 2' 3'. The intersection of the diagonals A 3, A 2, A 1 with the parallels 3', 2', 1' at G, F, E will be points in the required curve. Extend the axis to B', making A B'=A B ; draw perpendiculars to the axis from G, F, E, D ; lay off toward B', a'=A. a, A '=A b, A c' = A c; and draw B' D, c' E, V F and a' G. These lines will be tangents to the curve at D, E, F, G, and lines perpendicular to the tangents at these points will be perpen- dicular to the curve. The Hyperbola. An hyperbola is a curve from any point, P, in which, if two straight lines be drawn to two fixed points, F, F', the foci, their difference will always be the same. To describe an hyperbola (Fig. 109). From one of the foci, F, with an assumed radius, describe an arc, and from the other, focus F', with another radius exceeding the former by the given difference, describe two small arcs, cut- ting the first as at Pandjt?/ Let this operation be repeated with two new radii, taking care that the second shall exceed the first by the same difference as before, and two new points will be determined ; and this determination of points in the curve may thus be con- tinued till its track is obvious. By making use of the same radii, but transposing, that is, describing with the greater about F, and the less about F', FIG. 109. we have another series of points equal- CONSTRUCTION OF GEOMETRICAL PROBLEMS. 35 ly belonging to the hyperbola, and answering the definition ; so that the hyper- bola consists of two separate branches. The curve may be described mechanically (Fig. 110) by fixing a ruler to one focus, F', so that it may be turned round on this point, and connecting the other extremity of the ruler, R, to the other focus, F, by a cord shorter than the whole length of the ruler by the given difference ; then a pencil, P, FIG. 110. FIG. 111. keeping this cord always stretched, and at the same time pressing against the edge of the ruler, will, as the ruler revolves around F', describe an hyperbola. To draw a tangent to any point of an hyperbola (Fig. 111). Let P be the point. On F' P lay off P p, equal to F P ; draw the line F p; from P let fall a perpendicular on this line, P p, for the tangent. To describe a spiral (Fig. 112 and Fig. 113, the primary on a larger scale). Divide the circumference of the primary into any number of equal parts, say not less than eight. To these points of division o, e,f, i, etc., draw tangents, \ FIG. 112. FIG. 113. and from these points draw a succession of circular arcs ; thus, from o lay off o g, equal to the arc a o reduced to a straight line, and connect a and g by a curve ; from e, with the radius e g, describe the arc g h; from / the next arc, and so on. Continue the use of the centres successively and repeatedly to the extent of the revolutions required. DRAWING INSTRUMENTS. THE simple drawing instruments illustrated and applied in the construc- tion of the preceding problems, together with scales of equal parts, a protractor, and a drawing-pen, are all the instruments essential for topographical or me- chanical drawing. It is often convenient, for facility in working, to have com- passes of various sizes and modifications, and these, together with an assortment of rulers, triangles, squares, scales, and protractors adapted to varied work, are included in boxes of drawing instruments furnished by dealers. The smaller rulers and triangles are generally of hard rubber, and the larger of wood. As it is often inconvenient to carry long rulers, or straight-edges, and difficult to procure them ready-made, the draughts- man may have to depend on a carpenter or joiner for them. The drawing-board in its simplest form consists merely of narrow strips of thoroughly seasoned white-pine wood, free from knots, closely joined and glued, and held together either with a ledge at each end or with battens screwed to the back. For small boards, the former kind is in some ways the best, as it ad- mits of being planed on all four edges. Fig. 114 is more elaborate and one of the best drawing boards, possessing all the qualities of a first-class board. It is made of pine wood, glued up to the required width, with the heart side of each piece of wood at the surface. A pair of hard-wood battens are screwed to the back, the screws passing through the ledges in oblong slots that are bushed with brass, which fit closely under the heads, and yet allows the screws to move freely when drawn by the contraction of the board. To give the battens power to resist the tendency of the surface to warp, a series of grooves are 36 FIG. 114. DRAWING INSTRUMENTS. 37 sunk, half the thickness of the board, over the entire back. These grooves take the transverse strength out of the wood and allow it to be controlled by the battens, leaving at the same time the longitudinal strength of the wood nearly unimpaired. To make the two working edges perfectly smooth, allowing an easy move- ment of the square, a slip of hard wood is let into the end of the board. The slip is afterward sawed apart at about every inch to admit of contraction. The drawing-board should be truly rectangular and have perfectly straight sides, for the use of the T square. Two sizes are sufficient for ordinary use 41 x 30 inches for double elephant paper, and 31X24 inches for imperial and smaller sizes. Boards smaller than these are too light, and unsteady in handling. The drawing-table should be about 6 feet long and 4 feet wide, of 1 inch stuff, constructed similarly to FIG. 115. the drawing-board, and it is usually supported by a pedestal the height and inclination of which is adjusta- ble, or on trestles, or a strong frame at such height that the draughtsman may not have to stoop to his work. Fig. 115 shows an excellent form of trestle ; the upper part of the horses is attached to hard- wood supports, which slide through the body of the trestle and are provided with numerous holes ; by means of strong pins passing through the body of the horses and the holes the board may be set at various angles, the steel points in the top preventing the drawing-board from sliding or slipping off. Straight-edges are made of close-grained, thoroughly seasoned wood, such as mahogany, maple, pear, etc. ; also of celluloid, hard rubber, steel, or German silver. Those made of maple or pear wood answer every purpose and have the advantage of soiling the paper less than rubber or metal. No varnish of any description should be applied to any of the instruments used in drawing, as varnish will retain dust and soil the paper. Use the wood in its natural state, keeping it carefully wiped. Straight-edges should be about inch thick in the square or slightly rounded edges and 1 to 2 inches wide, according to their length. As the accuracy of a drawing depends greatly on the straightness of the lines, the edge of the ruler should be perfectly straight. To test this, place a sheet of paper on a perfectly smooth board; insert two very fine needles in an upright position through the paper into the board, distant from each other nearly the length of the ruler to be tested ; bring the edge of the ruler against these needles, and draw a line from one needle to the other; reverse the ruler, bringing the same edge on the opposite side and against the needles, and again draw a line. If the two lines coincide, the edge is straight ; but if they disagree, the ruler is inaccurate, and must be rcjointed. When one ruler has been tested, others can be examined by placing their edges against the correct one, and holding them between the eye and the light. Triangles may be made of the same kinds of wood as the ruler, somewhat 38 DRAWING INSTRUMENTS. thinner, and of various sizes. They should be right-angled, with acute angles of 45, or of 60 and 30. The most convenient size for general use measures from 3 to 6 inches on the side. A larger size, from 8 to 10 inches long on the side, is convenient for making drawings to a large scale. In the smaller trian- gles circular openings are made in the body for the insertion of the end of the finger, to give facility in sliding the triangle on the paper. Triangles are sometimes made as large as 15 to 18 inches on the side ; but in this case they are framed in three pieces, about 1 inch wide, leading the centre of the triangle open. The value of the triangle in drawing perpen- dicular lines depends on the accuracy of the right angle. To test this (Fig. 116), draw a line with an accurate ruler on paper. Place the right angle of the triangle near the centre of this line, and make one of the ad- jacent sides to coincide with the line ; now draw a line along the other adjacent side, which, if the angle is strictly a right angle, will be perpendicular to the first line. Turn the triangle on this perpendicular side, bringing it into the position ABC'; if now the sides of the triangle agree with the line B C' and A B, the angle is a right angle, and the sides are straight. If they do not agree, they must be made to do so with a plane, if right angles are to be drawn by the triangle. The straightness of the hypothenuse or longest side can be tested like a common ruler. FIG. 117. The T square is a thin straight-edge or ruler (Fig. 117), fitted at one end with a stock, applied transversely at right angles. The stock being so formed DRAWING INSTRUMENTS. 39 as to fit and slide against one edge of the drawing-board, the blade reaches over the surface, and presents an' edge of its own at right angles to that of the board, by which parallel straight lines may be drawn upon the paper. The stock should be long enough to give sufficient bearing on the edge of the board, and heavy enough to act as a balance to the blade, and to relieve the operation of handling the square. The blade should be sunk flush into the upper half of the stock on the inside, and very exactly fitted. It should be inserted full breadth, as shown in the figure ; notching and dovetailing is a mistake, as it weakens the blade, and adds nothing to the security. The upper half of the stock should be about ^ inch broader than the lower half, to rest firmly on the board and secure the blade lying flatly on the paper. One half of the stock c (Fig. 118) is in some cases made loose, to turn upon a brass swivel to any angle with the blade a, and to be clenched by a screwed FIG. 118. nut and washer. The loose stock is useful for drawing parallel lines obliquely to the edges of the board, such as the threads of screws, oblique columns, or connecting-rods of steam-engines. T squares are also made with a single movable head, shown in Fig. 119 ; FIGS. 119, 120. the blade, turning on , is clamped in position by the thumb-nut b. Fig. 120 illustrates a T square with a protractor at the head, convenient for laying off lines of designated angles. In many drawing-cases will be found the parallel ruler (Fig. 121), consist- FIG. 121. DRAWING INSTRUMENTS. ing of two rulers connected by two bars moving on pivots, so adjusted that the rulers, as they open, form the sides of a parallelogram. The edge of one of the rulers being retained in a position coinciding with, or parallel to, a given line, when the other ruler is moved, lines drawn along its edge are also parallel to the given line. This instrument is only useful in drawing small parallels, and in accuracy and convenience does not compare with either the triangle and ruler or T square. Another form of parallel ruler (Fig. 122) consists of a strip of wood with bevelled edges, having two holes to receive two broad wheels, a, a, which are FIG. 122. connected by an axle passing under the metal cover, b, #, and revolving in the supports, c, c ; the wheels come slightly below the surface of the wood, as shown in the end elevation. In drawing parallel lines the fingers are placed with a firm pressure about the centre of the metal cover, and the ruler is moved in the proper direction. This ruler is more easily applied than the former, but is more liable to error. VAKIABLE CURVES. For drawing arcs of a large radius, beyond the range of ordinary compasses, and lines varying in curvature, thin slips of wood, termed curves, are usually employed. These forms are of very general application, but others of almost every form, and made of hard rubber, pear wood, or celluloid, can be pur- chased. Whatever be the nature of the curve, some portion of the instrument will be found to coincide with its commencement, and it can be continued throughout its extent by applying, successively, such parts as are suitable, care being taken that the parts are tangent to each other, and that the continuity is not injured by unskilful junction. Fig. 123 shows an adjustable curve ruler, the main features of which are a hard-rubber face, , which holds the form of the required curve by a bar of FIG. 123. soft lead, Z>, kept in contact with the rubber face by the fasteners, c, and a flat spring inside these fasteners. This curve, while useful in the coarser kinds of draughting, does not do as neat or accurate work" as the separate curves above given. Thin splines are also to be had, which, held in position by leaden weights, serve admirably for a guide to the pen in describing curves (Fig. 124). For the DRAWING INSTRUMENTS. 41 same purpose a thin, hard-rubber ruler, with soft-rubber backing, answers well, and, as it can be readily rolled up, is extremely portable. The weights above shown are very convenient in holding the drawing-paper on the board, but thumb-tacks (Fig. 125), steel points with large, flat heads, are in general use. They can be readily forced into the wood, and as readily raised, but thumb-tack lifters can be purchased. in Elliptic, parabolic, and hyperbolic (see above) curves are furnished sets, but the draughtsman can make a model out of thick cardboard or cellu- loid, with which he can draw a very uniform curve. For the drawing of ellipses, very neat trammels or compasses with elliptic guides or patterns may be purchased. 42 DRAWING INSTRUMENTS. Fio. 124. FIG. 125. The drawing or right-line pen (Fig. 126) consists of two blades with steel points, fixed to a handle ; and they are so bent that a sufficient cavity is left between them for the ink. The blades are set with the points more or less open by means of a mill-headed screw, so as to draw lines of any required fineness or thickness. For red inks, the blades of the pen should be nickle-plated or German silver. One of the blades is framed with a joint, so that by taking out the screw the blades may be complete- ly opened, and the points effectively cleaned after use. The ink is put between the blades by a common pen. In using the pen, it should be slightly inclined in the direction of the line to be drawn, and care should be taken that both points touch the paper. These observations equally apply to the pen-points of the compasses. The drawing - pen should be kept close to the ruler or straight- edge, and in the same direction during the whole operation of drawing the line. Care must be taken to hold the straight-edge firmly with the left hand, that it does not change its position. For drawing close parallel lines in me- chanical and architectural drawings, or to represent railroads, canals, or roads, a rail- road pen (Fig. 127) is frequently used, a double pen with an adjusting screw to set the pens to any required small distance. This instrument is also made with pencil points (Fig. 128). Border - pens (Fig. 129), for drawing broad lines, are double pens with an intermediate blade, and are applicable to the drawing of map- borders. The same work may be done by drawing heavy outer lines with the common drawing- pen, and filling in with a brush or writing-pen. The curve-pen (Fig. 130) is especially de- signed for the ready drawing of curved lines. The axis of this pen is carried through the han- dle and fastened by a nut on top, allowing the pen to revolve, and thus more easily follow the curve. This instrument, made with two pens (Fig. 131), is called a railroad curve-pen. FIG. 128. FIG. 129. 43 The dotting-pen (Fig. 132) has on the back blade a pivot, on which may be placed a dotting- wheel, resembling the rowel of a spur ; the screw is for opeu- FIG. 131. ing the blades to remove the wheel for cleaning after use or replace it with one of another character of dot. A variety of dotting-wheels accompanies the in- strument, each producing a different-shaped dot. These are used as distin- guishing marks for different classes of boundaries on maps ; for instance, one kind of dot distinguishes county boundaries, another kind town boundaries, a third kind distinguishes that which is both a county and a town boundary, etc. 1 FIG. 132. In using this instrument, the ink must be inserted between the blades above the dotting-wheel, so that, as the wheel revolves, the points pass through the ink, each carrying with it a drop, and marking the paper as it passes. It sometimes happens that the wheel will revolve many times before it begins to deposit its ink on the drawing, thereby leaving the first part of the line blank, and, when it is gone over again, the first-made dots are liable to get blotted. This evil may be avoided by placing a piece of blank paper over the drawing to the very point the dotted line is to commence at, and drawing the wheel over the blank paper first, so that by the time it reaches the proper point the ink begins to flow. The dotting -instrument (Fig. 133) works on the principle of the drawing-pen. The outer wheel is rolled on the edge of a T square or straight-edge, and turns a ratchet wheel which causes the pen to move up and down. The flat point close to the pen must slide on the paper. To change the pat- tern of the dotted lines, the spring which holds the wheels on the axle is thrown back, and the proper ratchet wheel inserted. The best pricking -point is a fine needle held as in Fig. 134, and is used to transfer drawings by pricking through at the points of a drawing into the paper FIG. 133. FIG. 134. placed beneath. The handle of the ordinary drawing-pen often contains a pricking-point, which may be used by unscrewing the pen where it is joined to the handle. When drawings are transferred by tracing a prepared black sheet being placed between the drawing and the paper to receive the tracing the eye end of the needle forms a good tracing-point. 44: DRAWING INSTRUMENTS. The stylus (Fig. 135) is a piece of polished agate placed in a handle, and is used as a tracing-point. FIG. 135. Compasses are fitted with ink-points and with lengthening bars for drawing larger circles. Compasses should have joints in the legs, so that the points, pencil, and pen may be set perpendicular to the planes in which the circles are described (Fig. 136). Compasses of this general form may be had in sizes of 3 to 7 inches. For the measurement and laying off of small spaces, and the describing of small circles, there are small bow com- passes (Fig. 137). These are sometimes made with an adjusting screw between the legs. For the measurement or laying off FIG. 136. FIG. 137. Fio. 138. of distances the plain dividers are convenient, but for ready and close ad- justment the hair dividers (Fig. 138) are most suitable. The only difference is that in the hair dividers one of the points is attached to the body by a FIG. 139. spring, and by means of the screw b it can be moved a very little toward or from the fixed point more accurately than by closing or opening the dividers. In dividing a line into equal parts especially, it enables one to divide the excess or deficit readily. DRAWING INSTRUMENTS. For convenience of carrying in the pocket, there are portable or turn-in compasses (Fig. 139). There is a small attachment for a common pencil which enables it to be used like compasses. FIG. 140. Three-legged dividers (Fig. 140) are convenient, while transferring measures from a drawing to a copy on an equal scale, for locating a third point when two are established. For setting off very long lines, or describing circles of large radius, beam compasses are used (Fig. 141). These consist of a mere strip of wood, A, and two brass or German silver boxes, B arid C, which can easily be attached to the beam ; connected with the brass boxes are the two points of the instrument, G and H. The object of this instrument is the nice adjustment of the points G and H at any definite distance apart; at F is a slow-motion screw, by which the point G may be moved any very minute dis- tance after the distance from H to G has been adjusted as nicely as possible by the hand alone. The wheel attachment, I, is to carry the weight of the beam. The metal parts of this instru- ment occupy but little space. There are beam compasses in which the beam is graduated, and in which the boxes corresponding to B and C are fitted with vernier or reading plates, to afford the means of minutely subdi- viding the divisions on the beam. Beam compasses are also made of small round German-silver bars, one screwing into the other, on which are slides adapted for carrying pen or pencil and points. 16' H FIG. 142. Proportional dividers (Fig. 142), for copying and reducing drawings, are found in most cases of instruments. Closing the dividers and loosening the screw C, the slide may be moved up 46 DRAWING INSTRUMENTS. in the groove until the mark on the index corresponds with the required num- ber ; then clamping the screw, the space inclosed between the long points, A B, will be as many times that between the short points, E D, as is shown by the number opposite the index. If the lines are to be reduced, the distances are measured with the long points, and set off by the short ones ; if the lines are to be enlarged, then vice versa. Proportional dividers are also used for dividing the circumference of a circle into a number of parts. A special scale along the graduated edge, marked circles, is used, it being only necessary to move the slider to the proper number on this scale to obtain a chord of the proper length. It often happens that the length of the points becomes reduced by use or acci- dent. In this case it is only necessary to loosen the screw holding the short- ened point, take it out, grind to a point, and set to its former length. Scales. The application of simple scales to the construction of diagrams has been explained ; but among drawing instruments scales especially adapted to plotting are to be found in great varieties of form, divisions, and material. It is usual, especially in topographical drawings, for the draughtsman to con- struct a scale upon the finished sheet on account of its ready application to the determination of measures, and when the drawing is to be reduced or enlarged by photographing it is indispensable. Moreover, paper expands and contracts under hygrometric changes ; the scale should be subject to those same changes. To remedy this inconvenience Mr. Charles Holzapfel has introduced paper scales, which are portable and cheap; but as all kinds of paper are noi equally susceptible to changes of condition on the atmosphere, the detached paper scale affords only a partial correction. The scale should be written or drawn in all drawings ; also the date of com- pletion and name or initials of the draughtsman, as these data may be of value in the identification of the drawing. In all working architectural and mechanical drawings, use as large a scale as possible ; and even then do not depend upon the mechanics employed in the construction measuring correctly, but write in the dimensions as far as prac- ticable. For architectural plans, the scale of ^ of an inch to the foot is in very general use and is convenient for the mechanic, as the common two-foot rule carried by all mechanics is subdivided into ths, iths, and sometimes sixteenths of an inch, and the distances on a drawing to this scale can therefore be easily measured by them. This fact should not be lost sight of in working drawings. When the dimensions are not written, make use of such scales that the dis- tances may be measured by the subdivisions of the common two-foot rule ; thus, in a scale of ^ or ^ full size, 6 inches or 3 inches represent one foot ; in a scale of an inch to the foot or twelfth full size, each an inch repre- sents 6 inches, of an inch, 3 inches ; but when or fa an inch to the foot, or any similar scale, is adopted, it is evident that these divisions can not be taken by the two-foot rule. Plotting scales (Fig. 143) are scales of equal parts, with the divisions usu- ally on a bevelled edge, by which any length may be marked off on the paper without using dividers. There are also small offset scales, for use of which see " Topographical Drawing." Sometimes these scales are made with edges bevelled on both sides, and DRAWING INSTRUMENTS. 47 graduated to four different scales. Sometimes the section of the scale is tri- angular (Fig. 144), with six scales on the different edges. To avoid confusion NrLL 1 II II 1 i 1 II II 1 1 Ml II II 1 1 1 ill]' 1 ,! Ml II 1 1 1 1 1 I! 1 1 1 II \ ao \ f Oil- 6 1 It 19 IS Itr IE |Z It FIG. 143. from having many scales on one ruler, the triangular scale has a small slip of metal, A, readily put on, which covers partially the scales not in use. FIG. 145. FIG. 144. To divide a given line into any number of equal parts (Fig. 145). Let A B be the line, and the number of parts be ten. Draw a perpendicu- lar at one extremity, A, of the line ; with a plotting scale place the zero at the other extremity, B, of the line ; make the mark 10 on the scale coincide with the perpendicular ; draw a line along the edge of the scale, and mark the line at each division of the scale 1 to 9 ; draw per- pendiculars through these marks to the line A B, and they will divide A B into ten equal parts. The above figure illustrates the construction of diagonal scales. The simply divided scales give only two denominations, primaries and tenths, or twelfths ; but more minute subdivision is attained by the diagonal scale, which consists of a number of primary divisions, one of which is divided into tenths, and subdivided into hundredths by diago- nal lines (Fig. 146). This scale is con- structed in the follow- ing manner : Eleven parallel horizontal lines are ruled, inclosing ten equal spaces ; from one end set off the primary unit divisions, 0, 1, 2, 3, and draw vertical lines through these points; subdivide the extreme unit to the left on the upper and lower lines into ten equal parts, 1, 2, 3, etc. ; connect on the upper line with 1 on the lower line FIG. 146. 48 DRAWING INSTRUMENTS. A by a diagonal, and draw lines parallel to it through the other subdivisions. To take a measurement of, say, 168, we place one foot of the dividers on the pri- mary 1, and carry it down to parallel 8, and then extend the other foot to the intersection of the diagonal which falls from the subdivision 6 with this par- allel. The primaries may, of course, be considered as yards, feet, or inches ; and the subdivisions as tenths and hundredths of these respective denomina- tions. If the number of parallel spaces be eight and the subdivision be twelve, we can measure feet, inches, and eighths. In the diagonal scale the vertical subdivisions are often omitted. The diagonals may be applied to a scale where only one subdivision is re- quired. Thus, if seven lines be ruled (Fig. 147), inclosing six equal spaces, and the length be divided into primaries, as A B, B C, etc., the first primary, A B, may be subdivided into twelfths by two diagonals running from 6, the mid- dle of A B, to 12 and 0. We have here a very con- venient scale of feet and inches. From C to 6 is 1 foot 6 inches ; and from C on the several parallels to the various intersections of the diagonals we obtain 1 foot and any number of inches from 1 to 12. For the designing of machinery, it is very convenient to have some scale of reference by which to proportion the parts ; for this purpose a vertical and horizontal scale may be drawn on the walls of the room. Vernier scales are preferred by some to the diagonal scale already described. To construct a vernier scale (Fig. 148) by which a number to three places may be taken, divide all the primary divisions into tenths, and number these sub- 7/V 2 v <>L^- f / \r / \, / \ 0/2 FIG. 147. 10 2 4} 6 8 f f f II I I II I I I I I I I I I I I I I I i I I II I wn I ' I I I I i i I wv |/0 8 6 \ t 2 FIG. 148. divisions 1, 2, 3, from left to right. Take off now with the compasses eleven of these subdivisions, set the extent off backward from the end of the first primary division, and it will reach beyond the beginning of this division, or zero point, a distance equal to one of the subdivisions. Now divide the extent thus set off into ten equal parts, marking the divisions on the opposite side of the divided line to the lines marking the primary divisions and the subdivisions, and number them 1, 2, 3, etc., backward from right to left. Then, since the extent of eleven subdivisions has been divided into ten equal parts, so that these ten parts exceed by one subdivision the extent of ten subdivisions, each one of these equal parts, or, as it may be called, one division of the vernier scale, exceeds one of the subdivisions by a tenth part of a subdivision, or a hundredth part of a primary division ; thus, if the subdivision be considered 10, then from to the first division of the vernier will be 11 ; to the second, 22 ; to the third, 33 ; to the fourth, 44 ; to the fifth, 55, and so on, 66, 77, 88, 99. DRAWING INSTRUMENTS. 49 To take off the number 253 fr,om this scale, place one point of the dividers at the third division of the vernier ; if the other point be brought to the pri- mary division 2, the distance embraced by the dividers will be 233, and the dividers must be extended to the second subdivision of tenths to the right of 2. If the number were 213, then the dividers would have to be closed to the second subdivision of tenths to the left of 2. The number, thus taken, may be 253, 25'3, 2'53, according as the pri- mary divisions are taken as hundreds, tens, or units. The construction of this scale is similar to that of the verniers of theodolites and surveying instruments. The sector in its old form carried several scales on its faces. As given in Fig. 149, there are only double scales starting from the centre joint, which, without drawing, may be applied to the solution of problems on similar triangles. Let the lines A B, A C, represent the legs of the sector, and A D, A E, two equal sections from the centre ; then, if the points B C and D E be connected, the lines B C and D E will be parallel ; therefore, the triangles A B C, A D E, FIG. 149. FIG. 150. will be similar, and, consequently, the sides A B, B C, A D, D E, proportional that is, as A B : B C : : A D : D E ; so that if A D be the half, third, 5 50 DRAWING INSTRUMENTS. or fourth part of A B, then D E will be a half, third, or fourth part of B C ; and the same holds of all the rest. Hence, if D E be the chord, sine, or tangent of any arc, or of any number of degrees to the radius A D, then B C will be the same to the radius A B. Thus, at every opening of the sector, the transverse distances D E and C B from one ruler to another are proportional to the lateral distances, measured on the lines A B, A C. It is to FIG. 151. be observed that all measures are to be taken from the inner lines, since these only run accurately to the centre. On the scale in common boxes of drawing instruments, the edges of the sides are divided as a protractor (Fig. 84) for the laying out of angles. The ordinary pro- tractor consists of a semicircle of thin metal or horn (Fig. 150), whose circumference is divided into 180 degrees (180). In the larger protrac- tors each of these divisions is subdivided. Application of the protractor. To lay off a given angle from a given point on a straight line, let the straight line a b of the protractor coincide with the given line, and the point c with the given point ; now mark on the paper against the division on the periphery coinciding with the angle required ; remove the protractor, and draw a line through the given point and the mark. Fig. 151 is a protractor with a straight-edge revolving on a horn centre. Where the straight- edge is intersected by the edge of the protractor a vernier is attached, and will be found useful in close work for dividing the degrees into tenths. This protractor is often extended to full circles. For plotting field-notes expeditiously, drawing-paper can be obtained with FIG. 152. DRAWING INSTRUMENTS. 51 large, full circular protractors printed thereon, on which the courses can be readily marked, and thus transferred to the part of the paper required by a parallel ruler, or by triangle and ruler. These sheets are of especial use in plotting at night the day's work, as, on account of the large size of the protrac- tor, angles can be laid off with greater accuracy than by the usual protractor of a drawing-instrument case, with less confusion of courses, and more expe- ditiously. The pantograph is used for the copying of drawings, either on the same scale, on a reduced scale, or on an enlarged scale. Fig. 152 shows its simplest form and its application. The lower left-hand point, around which the frame is turned, is fixed, and the proportion of the drawing is determined by the position of the screw eyes in the holes of the arms. Fig. 153 is another form, of more finished construction. It consists of a set of jointed rulers, A, B, and another, C, D, about one half the length of the FIG. 153. former. The free ends of the smaller set are jointed to the larger at about the centre. Casters are placed at a a, etc., to support the instrument and to allow an easy movement. DBAWING-PAPERS. Papers adapted to drawing may be obtained of various qualities, thicknesses, and dimensions, either in sheets, pads, or rolls. Machine-made papers are generally used, and are to be had from stock in rolls up to 62 inches in width, but to order much wider. They are generally made from cotton for the more finished drawings ; but stronger papers for working drawings and details are of manilla or of coarse heavy stock. Eoll and sheet papers can be had mounted or backed with cotton cloth, which prevents. them from being torn, and permits of their being hung to the walls as maps. Hand-made drawing-papers are usually made in certain standard sizes, about as follows : Cap 13 inches by 17 inches. Demy 15 20 " Medium 17 " 22 " Royal 19 " 24 " Super Royal 19 " 27 " Tracing-paper is a prepared tissue paper, transparent and qualified to re- ceive ink lines and tinting without spreading. When placed over a drawing Imperial 22 inches by 30 inches. Atlas 26 " 34 " Double Elephant 27 " 40 " Antiquarian 31 " 53 " 52 DRAWING INSTRUMENTS. already executed, the drawing is . distinctly visible through the paper, and it may be copied directly or traced in pencil or ink. Tracing-paper often becomes tender with age, is apt to break in the folds, is not easily rolled. It is not suitable, therefore, for permanent drawings ; but the tracing can be readily transferred to drawing-paper by means of transfer paper. Place the fair sheet on the drawing-board, above it the transfer sheet with the prepared face down, then the tracing, and steady the whole by weights or by thumb-tacks fixed into the drawing-board. A fine, smooth point is then passed over each boundary and line on the tracing with a pressure of the hand sufficient to cause a clear line to be left by the transfer paper on the fair sheet. Finish these lines in ink. The copyist should be careful in his manipulation that no unnecessary lines or smutches be left on the fair sheet. Transfer paper can be readily obtained in sheets, either in black, blue, vermilion, or graphite, or it can be made by smearing with a piece of flannel one surface of thin paper with a coating of lard and graphite and, after a day's drying, wiping off the superfluous portion with a soft rag. Parchment papers are much stronger than tracing-papers, and are usually transparent enough to serve the same purpose ; the thicker kinds are well adapted for drawing and engrossing. De La Rue's process for the manufac- ture of parchment paper is to plunge unsized paper for a few seconds into sulphuric acid, diluted with half to a quarter its bulk of water, the solution being of the same temperature as the air, and afterward wash with 'weak ammonia. A drawing may be made to accompany a letter by saturating the letter paper with benzine till it becomes transparent, then using it as tracing-paper, copying the design in pencil, and finishing in copying-ink after the benzine has evaporated, so that it can be transferred with the descriptive writing to the letter book. Transparent tracing-cloth can be had in wide and long rolls. It is much stronger than tracing-paper, and serves a permanent purpose. Should the tracing-cloth refuse to take ink lines well, almost any fine white powder will remedy this, such as chalk, fuller's earth, pipe clay, or plaster of Paris sprinkled on and rubbed in well. It is usual to draw on the dull side of the cloth, except where colour is to be put in, when the ink lines are drawn on the glossy side and the colour on the dull back. Designs. and finished drawings made in pencil on paper are traced on cloth in ink, and in this form are preserved as originals and can be copied by the heliographic process, either wholes or details as needed. When a white sheet of paper is placed behind the tracings, the drawing may be readily photographed on a reduced or enlarged scale, and much more cheaply than by any other process ; and such negatives may be used in process engraving for book illustrations. Heliographic paper can readily be had in sheets or rolls, and the mixture for the preparation of the paper can also be purchased, or can be made by dissolving If ounce of common citrate of iron in 8 ounces of water, and 1 ounce of red prussiate of potash in 8 ounces of water, and then mixing them just previous to using. Papers and mixtures must be kept from the light or they will lose their sensitiveness. The above is a mixture for the most com- DRAWING INSTRUMENTS 53 mon form of sun prints, called, the ferro-prussiate or blue process, in which white lines are developed on a blue ground. By the cyanotype process blue lines are developed on a white ground ; by the nigrosine process, black lines on a white ground ; by the chromide dry process, dark lines on a tinted ground. Papers for all of the above processes are on sale, with directions for use. If none can be had, and it is desired to prepare some, use the ferro-prussiate process as the simplest, of which a recipe has been given above, the paper should be chemically neutral, of even material, and capable of being washed. Inks are to be had especially adapted for the tracings in bottles and cakes. It is necessary for a good print that the lines should be of a deep black. If not sufficiently opaque, burnt Sienna, burnt umber, or gamboge added to the ink improves the prints. For the manipulation there is needed plate glass and a blanket a little larger than the drawing, also a shallow tray, that the drawing can be placed in flat for washing. Lay down the blanket on the drawing-board, above that the ferro-prussiate paper, next the drawing, and then the glass. Expose to the sunlight until the background is a metallic gray. The length of exposure may be from five min- utes up, depending on the intensity of the sunlight, the age of the prepared paper, and the transparency of the tracing. Now lay the ferro-prussiate paper in the tray, cover with water, and leave it for five to ten minutes ; wash thor- oughly and dry. The usual form of printing-frame, as purchased of dealers, shown in Fig. 154, consists of a frame into which fits a sheet of glass, preferably of plate glass, - -O. rnacin N g/ass FIG. 154. with a hinged backboard, to the inner side of which a piece of felt is glued in the smaller sizes, while in the larger the felt is separate ; on the back of this board are two brass springs fitting under the metal catch, making a close con- tact with the glass. As shown in the small sectional drawing, the frame is turned upside down. The glass is placed in first, then, successively, the tracing with its face to the glass, the prepared paper with the prepared side to the tracing, and the felt ; then the backboard is placed and held in position by the springs, the frame is turned up, and the directions given above as to exposure and washing are properly carried out. When it is necessary to make additions and alterations on blue prints, a 54 DRAWING INSTRUMENTS. special ink can be procured; lines made with this preparation on the blue ground turn white. (See FREE-HAND DRAWING.) The helios process is useful for copying not only drawings, but contracts, estimates, tables, etc., when they are written on transparent paper or cloth; and so is the nigrosine process. Bristol board is a cardboard with a very fine surface. It can be obtained of various thicknesses and of the same dimensions as sheet drawing-papers. It is adapted to water-colours, pen-and-ink sketches, and fine line-drawings ; the Patent Office requires sheets 10 by 15 inches, and these can be obtained with border and wording of witness, inventor, and attorney properly printed in. Mouth glue, for the sticking of the edges 6f drawing-paper to the board, is made of glue and sugar or molasses ; it melts at the temperature of the mouth, and is convenient for the draughtsman. Drawing-paper may be fixed down on the drawing-board by thumb-tacks at the corners, by weights, or by gluing or pasting the edges. The first is sufficient when no shading or colouring is to be applied, and if the sheet is not to be a very long time on the board ; and it has the advantage of preserv- ing the paper in its natural state. For shaded or tinted drawings, the paper must be damped. Damp-stretching is done as follows : The edges of the paper should first be cut straight, and, as near as possible, at right angles to each other. The sheet should be enough larger than the intended drawing and its margin to admit of being afterward cut from the board, leaving the pasted or glued border. The paper must first be placed on the drawing-board and thoroughly and equally damped with a sponge and clean water on the side on which the draw- ing is to be made. This done, lay a straight flat ruler on the paper, with its edge parallel to, and about half an inch from, one of its edges. The ruler must now be held firm, while the projecting half inch of paper is being turned up along its edge ; then a piece of mouth glue, having its edge partially dissolved by holding it in warm water for a few seconds, must be passed once or twice along the turned-up edge of the paper, after which, by sliding the ruler over the glued border, it will be again laid flat, and, the ruler being pressed down upon it, that edge of the paper will adhere to the board. If sufficient glue has been applied, the ruler may be removed directly, and the edge finally rubbed down by an ivory book-knife or by the bow of a common key, rubbing it on a slip of paper placed on the drawing-paper, so that the surface of the latter may not be soiled ; this will firmly cement the paper to the board. Another edge of the paper is then treated in like manner, and the remaining edges in succession. Sometimes strong paste or mucilage is used instead of glue. The wetting of the paper is done for the purpose of expanding it ; and the edges, being fixed to the board in its enlarged state, act as stretchers upon the paper, while it contracts in drying, which it should be allowed to do gradually. All creases or undulations by this means disappear from the surface, and it forms a smooth plane to receive the drawing. After the drawing is finished, cut off the paper inside the pasted edge, and remove the edge by warm water and the knife. DRAWING INSTRUMENTS. 55 MOUNTING PAPEE AN.D DBAWINGS, VAENISHING, ETC. When paper of the requisite quality or dimension can not be purchased already backed, it may be mounted on muslin. The cloth should be well stretched upon a smooth flat surface, being damped for that purpose, and its edges glued down, as was recommended in stretching drawing-paper. Then with a brush spread strong paste, beating it in till the grain of the cloth be all filled up ; for this, when dry, will prevent it from shrinking when subsequently removed ; then, having cut the edges of the paper straight, paste one side of every sheet, and lay them upon the muslin sheet by sheet, overlapping each other slightly. If the drawing-paper is strong, it is best to let every sheet lie five or six minutes after the paste is put on it, for, as the paste soaks in, the paper will stretch, and may be better spread smooth upon the cloth ; whereas, if it be laid on before the paste* has moistened the paper, it will stretch after- ward and rise in blisters when laid upon the cloth. The paper should not be cut off from its extended position till thoroughly dry, which should not be hastened. Leave it in a dry room to do so gradually, if time permit ; if not, it may be exposed to the sun ; in the winter season the help of a fire may be neces- sary ; but it should not be placed too near a scorching heat. In joining two sheets of paper together by overlapping, it is necessary, in order to make a neat joint, to feather-edge each sheet ; this is done by care- fully cutting with a knife half way through the paper near the edges on the sides which/ are to overlap each other and then stripping off a feather-edged slip from each, which, if done dexterously, will produce a very neat and effi- cient joint. For mounting and varnishing drawings or prints, stretch a piece of linen on a frame, to which give a coat of isinglass or common size ; paste the back of drawing, which leave to soak; and then lay it on the linen. When dry, give it at least four coats of well-made isinglass size, allowing it to dry between each coat. Take Canada balsam diluted with the best oil of turpentine, and with a clean brush give it a full flowing coat. When drawings are not mounted on muslin, the edges may be protected from tearing by binding with gummed tape, or strips of paper which may be cut or purchased. Drawings, as far as possible, should be preserved flat in drawers, and this is especially desirable for tracings which are to be often sun-printed. The classification of drawings is varied. The common method is to devote a separate drawer to the drawings of each machine, or of each group or class of machine ; another is to have drawers of various sizes and arrange the drawings according to sizes. MANAGEMENT OF THE INSTEUMENTS. In constructing preparatory pencil-drawings, it is advisable, as a rule of general application, to make no more lines upon the paper than are necessary to the completion of the drawing in ink ; and also to make these lines just dark enough to be sufficiently distinct. It is often beneficial to ink in one part of a drawing before touching other parts at all ; it prevents confusion, makes the first part easy of reference, and 56 DRAWING INSTRUMENTS. allows of its being better done, as the surface of the paper inevitably contracts dust and becomes soiled in the course of time, and therefore the sooner it is done with the better. Circles and circular arcs should, in general, be inked in before straight lines, as the latter may be more readily drawn to join the others than can the former. When a number of circles are to be described from one centre, the smaller ones should be inked first, while the centre is in better condition. When a centre is required to bear some fatigue, it should be protected with a thickness of stout card glued or pasted over it, to receive the compass-leg. India-rubber is the ordinary medium for cleaning a drawing and for cor- recting errors of the pencil. For slight work it is quite suitable ; that sub- stance, however, operates to destroy the surface of the paper ; and, by repeated application, it so ruffles the surface as to spoil it for fine drawing, especially if ink shading or colouring is to be applied. It is much better to leave trivial errors alone, if corrections by the pencil may be made alongside without confu- sion, and not clear away superfluous lines till the inking is finished. W T hen ink lines have to be erased to any considerable extent, the best way is to use an ink-erasing rubber. Single lines may be erased by cutting a long narrow slit in a piece of thin cardboard or celluloid and erasing through it. For cleaning a drawing, a piece of bread two days old is preferable to India- rubber, as it cleans the surface well and does not injure it. A sponge rubber may also be used for this purpose. For ordinary small erasures of ink lines, a sharp rounded pen-blade, applied lightly and rapidly, does well, and the sur- face may be smoothed down by the thumb-nail. In drawings intended to be highly finished, particular pains should be taken to avoid the necessity for cor- rections, as everything of this kind detracts from the appearance. The best work can only be accomplished by keeping the instruments in good order; their working parts should be carefully preserved from injury. The scales must be kept scrupulously clean ; the inking tools should have especial care, and the blades kept well set, for which a small oil-stone is con- venient. To dress up the tips of the blades of the pen or of the bows, as they usually become worn unequally, they may be screwed up into contact in the first place, and passed along the stone, turning upon the point in a directly perpendicular plane, till they acquire an identical profile. Being next unscrewed and exam- ined to ascertain the parts of unequal thickness round the nib, the blades are laid separately upon their backs on the stone, and rubbed down at the points, till they be brought up to an edge of uniform fineness. It is well to screw them together again, and to pass them over the stone once or twice more, to bring up any fault ; to retouch them also on the outer and inner side of each blade, to remove barbs or fraying; and, finally, to draw them across the palm of the hand. India ink, which is commonly used for line-drawing, should be rubbed down in water to the degree that avoids the sloppy aspect of light lining with- out making the ink too thick to run freely from the pen. This medium degree may be judged of after a little practice by the appearance of the ink on the palette. The best quality of ink has a soft feel when wetted and smoothed^ being then free from grit or sediment, and has a musky smell. DRAWING INSTRUMENTS. 57 Slabs of many forms and different materials are used in grinding down the ink. The one shown in Fig. 155 is a square slab of slate, with a countersunk circular recess and a well in the centre to hold the ink ; the cover is a piece of heavy glass. A quantity of ink may be prepared at one time, but it must be kept well covered to exclude dust and prevent evaporation. The pen should be filled by FIG. 155. a narrow strip of paper, dipped in the ink and inserted between the blades. India ink and ink of various colours can be purchased in bottles, and this answers very satisfactorily for most work. Waterproof ink, which admits of being washed over, can be bought in sticks or in bottles. It is of primary importance to keep the blades of the inking tools free from obstruction ; this may be readily accomplished without unscrewing the pen by passing a slip of paper between the blades, or by drawing the point firmly over a piece of paper or on the fleshy part of the hand. EXERCISES WITH THE DRAWING-PEN. Before proceeding to the construction of finished drawings, skill should be acquired in the use of the drawing-pen, supplemented often by the writing-pen. Beginning with lines, outlines of figures, alphabets, and the like, the draughts- man should strive to acquire the habit of readily drawing clean, uniform lines, without abruptness or breaks where straight lines connect with curved ones. Draw straight lines of different grades : as, fine medium coarse at first, lines of indefinite length, taking care that they are drawn perfectly straight and of uniform width or grade. Then draw lines of definite length between assumed points, taking care to terminate the lines exactly at these points. Lines as above are / till lines. The grades depend on the effect which the draughtsman wishes to give. Draw dotted lines, broken lines, and broken and dotted lines, of different grades : 58 DRAWING INSTRUMENTS. Draw fine lines at uniform distances from each other : FlO. 156. To give uniform appearance, the lines must be of uniform grade and equally spaced. Practice in lines of this sort is important, as they are much used in drawing to represent sections, shades, and conditions, as soundings on charts, density or characteristics of population, areas of rain, temperature, and the like. Draw lines as in Fig. 156. These lines are diagonal with the border-lines, and are used to represent sections of materials. In the figure, lines differently inclined .rep- resent different pieces of the same material. Instruments called section- liners are to be had for draw- ing these lines, but for the usual needs of a drawing office the triangle and straight-edge, with the drawing-pen, will be sufficient. Sections of different materials may be represented in different kinds of lines (see page 177). To represent cylindrical surfaces (Fig. 157). Draw a semi-circumference, and mark on it a number of points, at equal distances apart, and through these points draw lines perpendicular to the diameter across the surface to be represented. It is not absolutely necessary that the central space should be equal to the others; it will be more effective to leave out two of the lines, and make it to this extent wider. To construct a mass of equal squares (Fig. 158). Lay off a right angle, and on its sides mark as many points at equal distances apart as may be necessary ; through these points draw lines parallel to the sides. Or, construct a rectangle ; mark on its sides as many points, at equal dis- tances apart, as may be necessary ; through these points draw the lines. To construct the squares diagonally to the base (Fig. 159). FIG. 157. DRAWING INSTRUMENTS. 59 Mark on the sides of the right angle as many points, at distances apart equal to the diagonal of the required squares, as may be necessary. Connect these points by lines as shown, and through the same points draw lines at right angles to the others. To cover a surface with equilat- eral triangles (Fig. 160^. Construct an angle of 60, and mark on its sides points at dis- tances apart equal to the side of the triangle. Connect these points 5 and through these points draw lines FIG. 158. parallel to the sides of the angle. Two such triangles joined at the base form a lozenge. Six triangles may be arranged as a hexagon. The whole surface may be arranged in lozenges or hexagons. To cover a surface with octagons and squares (Fig. 161). Lay off the surface in squares having sides equal to the width of the octagons. Corner the outer squares to form octagons (Fig. 68). Extend the sides of these octagons across the other squares, and similar corners will be cut off, and the octagons and squares required will be com- plete. With the aid of paper thus covered with squares, triangles, or lozenges, various geometrical designs may be readily con- structed, pleasing in their effect, and affording good practice to young draughtsmen. Any design can be copied by covering it and the clean sheet with squares. Mark the positions of points in the design or the sides of cor- C F FIG. 159. FIG. 160. FIG. 161. 60 DRAWING INSTRUMENTS. responding squares, and draw the connecting lines. To enlarge or reduce the design, make the squares or triangles proportionately larger or smaller. FIG 162. FIG. 163. FIG. 164. In transferring designs and drawings from books or plates, on which squares can not be drawn, it is very convenient to have a square of glass, with squares upon it, which may be laid on the drawing, and thus serve the same purpose as if squares had been drawn. The glass may be readily prepared by painting one of its surfaces with a thin coat of gum, and drawing squares upon it with the drawing- pen ; if every fifth or tenth line be made fuller or in a different colour, it will be still more convenient for reference. Fig. 162 gives the front and side views of an acanthus leaf, the surface being covered with squares, and on a ground of like squares in Fig. 163 the side view is transferred, but in a re- versed position. This is done by making the position of the outline and then of the interior lines with reference to the squares, as designated by letters and numerals. Fig. 164 is a transfer of both figures on a reduced scale. Designs for woven goods, oil cloths, ceiling and wall ornamentation, and the like are usually based on geometrical figures, and in certain proportions sym- metry and subordination of one part to another fall within the term of artistic. The following are designs in which the ruling figure is a trefoil : "In the equilateral triangle (Fig. 165), each side is divided by a dot, and from the centre of the triangle lines are drawn to each angle, and from the dot in the middle of each side to the opposite sides of the figure. The geometrical plan of the design is thus laid out, and the figure is easily filled in by drawing simple curves from the centre of the form to the DRAWING INSTRUMENTS. 61 dot on each side of it, and, lastly, filling in the form of the trefoil a little below the point of each corner of the triangle. "The square (Fig. 166), which is the next form, is developed in much the same manner. The sides are bisected, and from a point in the centre lines are FIG. 165. FIG. 166. FIG. 167. carried to each angle, and to all the dots on the sides. As in the preceding figure, slight curves are made on either of 'the side-lines, and the trefoil is added to each angle, with the base of the middle leaf touching the transverse working-lines between the sides. It will be seen that the penta- gon (Fig. 167) and the hexagon (Fig. 168) also are formed in the same general manner, but the proportion of the top of the trefoil varies from its sides. " In drawing the circular rosette (Fig. 169), the circum- ference should be constructed on a vertical and a horizontal diameter, with two other diameters bisecting it at equal angles, which divide it into eight sections, the half diameters, upon FIG. 168. FIG. 169. FIG. 170. all of which curved lines and the top of the trefoil are made. A series of arcs may be added at the pleasure of the designer. In the two pieces of moulding (Figs. 170 and 171) the trefoil is inserted vertically to the sides in one and horizontally in the other. In the latter, a half of the trefoil is added upon the sides to enrich the elementary figure ; and the double line and the transverse lines which form the squares are repeated for the sake of symmetry, and as affording an impression of agreeable repose. " It is from such a basis as this that all these various patterns are derived, and they produce a result which an inexperienced eye, unaccustomed to analyze designs, could scarcely resolve into its elements." 62 DRAWING INSTRUMENTS. Figs. 172-175 are other illustrations of the same principle, of varieties of rosettes constructed on a similar plan. FIG. 171. All of these designs can be constructed mechanically, but more grace is given to the design by the filling in with free hand, and it is an excellent prac- FIG. 172. Fio. 173. FIG. 174. FIG. 175. tice in the execution of the more elaborate Saracenic and Moorish diaper. In all of these where there are repetitions of the same figures it is usual to draw but one, and then transfer this, with the finish in crayon or pencil. LETTERING. In Fig. 176 are examples of block letters constructed on squares, a rudimen- tary form of mechanical letters, which can be made with the aid of cross-sec- tion paper. Although lettering admits of an endless variety of forms, the draughtsman should comprehend that there are rules on which letters should be constructed before he undertakes the free-hand method. Fig. 177 gives the designation of various parts of a letter to which reference is made in the description. In the Roman letters the square is taken as the scale of construction. Fig. 178 gives the scale of proportionate width. W takes the whole square, its height and width being equal ; I is one quarter as wide ; A, five sixths, etc. To obtain the width of any letter according to this scale, the height may be marked off on the vertical 12. Where the horizontal line from this point intersects the diagonals of the desired letter the width is measured. The thickness of the body stroke of the letters is about one fifth the height; the thickness of the body curve is slightly in excess of this, and the excess is added outside the letter ; otherwise in comparison with the straight body strokes the curved stroke would appear too thin. All letters are of the same height, except those curved or pointed at the top or DRAWING INSTRUMENTS. 63 bottom, such as C, G, J, 0, S, U, A, V, W. When the curved or pointed parts are at the top they must extend a little above the line and when at the bottom below the line, otherwise they will look smaller than those of square outline. The lower feet of letters and the feet of T extend about one third the height, but the upper feet are a trifle smaller. The intermediate horizontal hair stroke in B, E, F, H, and E is a little N D _l> z u. x UJ > r a Fia. 177. above the centre, P slightly below the centre, and A about one third of the, height above the lower line. The hair strokes and outlines are first put in ; the outline is then filled with a writing-pen, toothpick, or brush. DRAWING INSTRUMENTS. Fio. 179. However well proportioned the letters may be, an even effect is not produced unless a proper space is made between them. In letters of square form the spacing is equal, but where such combinations as LT, AT, AA, and numerous others occur the spacing must be less. No general rule can be given for this, and it must be left to the practised eye of the draughtsman. The only rule necessary for the construction of small Koman letters is that for ascertaining their height as compared with the capitals : Let a vertical line a b (Fig. 179), equal to the height of the -capital, be drawn, and a line at right angles at the top of this line, equal to one half its length ; connect d to ec, and lay off the length of the line d e, equal to b d ; then a e will be the height required. When the learner has acquired some dexterity in lettering, the upper and lower line alone will be nec- essary for his guidance ; he may then attempt the ex- ecution of the curves, without the compass, by free hand. In Italic letters the proper angle for their slant is 23 from the vertical ; the proportions are the same as in the Roman letters In stump letters the capitals are the same as Italics. The small letters differ somewhat, and are made with one bold stroke of the pen, the hair line gliding imperceptibly into the body stroke. Block letters, of which an example has been given, constructed on squares, are one of the most valuable types, being very distinct and readily drawn by the drawing-pen. The letters are of the same proportional width as the Roman, except that the M is a square. The height and width of the letters are varied to suit their application. There are lettering triangles (Fig. 180) made to give the angles with the verticals of inclined letters. Old English and German text and other let- ters of a similar character may be quickly and neatly written by the use of a wooden toothpick for the body strokes, the hair lines and termina- tions being afterward put in with a fine pen. An old style of writing that has lately gained considerable popularity in this country is round writing. This resembles ordinary writing in that one letter is joined to the next, and each word written as a whole. There are special pens made for this writing, which are very useful; but in place of these the ordinary stub pen can be used. This writing consists of a very few elements, merely shaded semicircles, straight shaded lines, and diagonal hair strokes ; the pen is held in such a manner that you are able to draw a fine hair line at an angle of 45 with both nibs of the pen, and the pen is held in this position for all letters. NXY AMV W FIG. 180. DRAWING INSTRUMENTS. HOMAET ABCDEFGHIJK LMNOPQRSTW abcdeWXYZ fghij klmnopqrstuvwxyz ITALIC LMNOPQRSTUV alcdeWXYZ fghij klm n op qrs t uvwxyz acefg h ik ms u wxy z i n m iv v vi yn w ix XLC DM O12 34 5 6 780 V r. 66 DRAWING INSTRUMENTS. ABCDEGHJKLMNOPRSTUWY ABCDEGHJKLMNOPRSTUVWY ABCDEFGHJKLMNOPRSTUVWr ABCDEFGHIJKLMNOPQBSTUVWY DRAWING INSTRUMENTS. 67 ENGLISH GOTHIC. ABC DE FGH IJ KLMN OP QRST UV WX YZ 1234567890 ITALIC. ABC DE FGH IJ KLMN OP QRST UV WX YZ a be de fgh ij klmn op qrst uv f ivx yz TUSCAN. ABC DE FGH IJ KLMN OP QRST UV WX YZ 1234567890 ABC DE; PGH IJ KLMUOPQEST UVWX YZ ate de fgh. ij klmn op qrst uvwxyz DRAWING INSTRUMENTS. ENGLISH CHURCH TEXT. ic / iC fl ' abr fa fglj ij klntn np qrst tin rax g MEDIAEVAL. O adr bp fg| ij hlran 09 qrsf ufi fDf g? 131 K3LWB WX f 25 lic d.e fgh ij ttlmn np qrst utr wx COAST CHART No. 20 NEW YORK BAY AND HARB OR NEW YORK DRAWING INSTRUMENTS. 69 LJ O Q cc CD LJ OH CO ^ (WJ Q - - / | z O o X DC LJ O * h- D E Q Z m DC DC WATE a: LJ E oc Ul CO U) S 03 u Q u Z CO o 1 D CO s h X (fi CJ OD 70 DRAWING INSTRUMENTS. Cxmfrart PLAN FRONT ELEVATION REAR SIDE TRANSVERSE LONGITUDINAL SECTION The character and size of the letters should be in accordance with the draw- ing on which they are to appear. Thus in engineering or mechanical drawing nothing is so appropriate as the block and Koman letter. In topographical or map drawing several styles of various sizes are used ; Koman capitals of different sizes are used in designating States, countries, and cities, while State boundaries and towns, large villages, summits, and boundaries of countries are written with an initial capital and small Roman letters. Large bodies of water are denoted in Italic capitals, smaller bodies, such as streams, creeks, small lakes, and ponds, with an initial Italic capital and stump letters, the general direction of the letters following the course of the stream. Capital block letters differing in size represent ranges of mountains, railroads, stations, streets, and prominent objects on a map. Oblique capital block letters repre- sent railroads and canals. Old English and German text are the styles most employed for the en- grossing of certificates and similar uses. Letters on topographical drawings are written horizontally, so as to be read from the lower right-hand corner of the map, except such as follow the course of a stream or a railroad ; and these can usually be arranged to be read from the same direction. A number of specimen titles are given, illustrating the use of the different styles of letters, but it will be found that the plainer the letters the better the effect produced, and for this reason it is generally well to omit fancy letters. No better example of neat and dignified titles can be found than those on the maps issued by the United States Coast Survey, the chief beauty of which con- sists in the admirable adjustment of the sizes of letters, the few styles, and the almost perfect execution. The illustrations of letters and titles given are taken from those in general use, but the draughtsman should make a large collection of titles of maps and books, drawings of machinery, advertisements, and business cards, copying carefully such as may suit him, by which he will gain ease of manipulation and taste in selection, to give character and finish to his own drawings. DRAWING INSTRUMENTS. 71 PROFILE AND CROSS-SECTION PAPER. Paper printed in squares is used by designers of figures for calicoes, silks, and woollens. For the engineer, there is a class of papers called profile and cross-section papers, sold in sheets or rolls, and of various scales. In the first, which is almost entirely applicable to lines of surveys of railroads and high- ways, the vertical scale is to the horizontal as 20 to 1. This is the usual dis- tortion to make grades, with the cuts and fills apparent. The latter originally UNITED STATES UNITS. FIG. 181. intended, as the name implies, for cross-sections of railway or canal cuts, bat now extensively employed by the architectural and mechanical designer for the rough sketches of works either executed or to be executed ; by the 72 DRAWING INSTRUMENTS. sanitarian, for the plotting of death-rates ; for thermometric and hygrometric readings ; by the broker and merchant, for the graphic representation of the prices of gold, stocks, or articles of merchandise, during a term of years ; by the railway superintendent, for the movement of trains ; and for a multitude of other uses. Cross-section papers most generally applicable are in. divisions of tenths ; but as mechanics are more conversant with the two-foot rule, of which the divisions are in eighths, paper with like divisions are more convenient, and designs on it more intelligible to them. Fig. 181 shows a graphical method of determining the equivalent values of the metric system of measurements in United States units, or vice versa. The vertical scale represents the metric units, and the horizontal the common or United States units. Example. What is the equivalent value of seven kilometres in miles ? Read upward on the metric scale to 7, then read on that horizontal line to the point of intersection with the line designated " Miles and Kilometres," that is, at the point on the United States scale of units representing 4*35, and you find that seven kilometres are equal to 4-35 miles. What is the value of five pounds in kilogrammes ? The process is the same as the foregoing, except that, to change United States units into the metric units, you first read horizontally, then upward. In this case five pounds is found equal to 2*25 kilogrammes. The divisions may represent single units, ten units, one hundred units, etc. Of late it has been common here and in England, to write ft. Ibs., instead of Ibs. ft., but where French weight and measures obtain, the rule is to say kilogrammetres, that is the weight before the distance moved. Fig. 182 shows the method of finding the average of a number of observa- tions, to determine the velocity of a current of water. The figure represents the path of a float in a wooden flume or channel, of rectangular section, from WIDTH OF FLUME 1O' 20" FIG. 182. Francis's " Lowell Hydraulic Experiments." The width of the cut represents the width of the flume, each abscissa being one foot ; the ordinates are the speeds of float in divisions of O'l foot per second ; the small circles represent the floats in their observed path and speed ; and the curved line shows the average velocity in the different threads of the stream, from which the lines of average velocities of the entire width of flume are deduced. The velocities were taken by tin tubes loaded so as to float within about an inch of the bottom of the flume, with the top plugged and projecting a few inches above the surface of the water. The results were checked by flows DRAWING INSTRUMENTS. 73 measured over a weir ; but for all practical purposes the velocities as taken by the floats may be considered averages on each thread of the stream. A full set of tubes were prepared adapted to the depths of the water, and taken to the flumes while experimenting. For general use a cylinder may be adapted as a float with an open pipe sliding down it adjustable to the depth. Fig. 183 is a diagram illustrating graphically the difference between the charge on a ton of merchandise per mile on the New York Central and Hud- son Eiver Railroad and the Erie Canal for every year between 1857 and 1880. The higher values in every case represent the railroad rates and the lower the canal rates. The black band shows the difference between them. FIG. 183. Fig. 184 is a graphic representation made up from the records of " The Engineering and Mining Journal," exhibiting the amount of pig iron made in the United States per year for thirty-one years. In constructing the diagram Y4 DRAWING INSTRUMENTS. cross-section paper was used, but in tracing the vertical cross lines were omitted. FIG. 184. Fig. 185 is made up from the time-table of the New York, New Haven and Hartford Railroad, showing the movement of trains, two from New York and two from New London, the horizontal lines being cut off on a scale of miles for each station, and the vertical lines being a scale of hours. If the speed had been uniform, the line showing the movement of trains would have been straight, but the line represents the practical running time. DRAWING INSTRUMENTS. m r- o> m CN ooo h ca x - - _ OU.UJ COQ.(/5_IC/>C3Uj5 O (/) O-l CO O UJ 12 Z "s,. ^ x 10 Fia. 185. 12 10 76 DRAWING INSTRUMENTS. ?" A , . A ,| . ill A 75 SU A H I. ' 1 11 "in i i 1 N A 111' J 1 A /> [1 IA A A Jl W * 1 A A/> M | IT W 5 AA A A A s , A A ^ A A A A 1 ll'll II I A A A A A A A A AA A A A A ^ J| A f AA > A A A A A A A A 1 A A A - A A \ A A A A A A A /\ . A A AW A A A A A /\ /\ A A ' /\ "> A A A ^ A A n A Range of Temperature degrees daily A Percentage of Humdty dally A A 55.2 T. Total deaths from all causes L. Deaths from Loca Diseases nfant Mortal ty under 1 year of age Z. Mortal ty from all Zymot c Diseases 2 3 Z Z < OL Id Q_ 40 . Q H 3 CL 0. ^ b. " T O ~^ on n CO u D "0 - - - -. J-M JUNE JULY AUGUST SEPTEMBER 1870 Fio. 186. DRAWING INSTRUMENTS. ff Fig. 186 is a graphic representation of the mortality and general classes of diseases as registered by the New York City Board of Health for the months of June, July, August, and September, 1870 ; with the daily records of tem- perature and humidity ; to complete these diagrams there should be one of the daily rainfalls. For meteorological purposes it is usual to take at observatories the commencement, termination, and amount of rainfall. Above is an ornamental design in straight lines on the bases of lines parallel to the sides of an equilateral triangle. In pages 78, 79 are given designs on the bases of lin'es ruled in rectangles and lozenges. The figure, page 80, illustrates how colors may be represented in a design. In pages 81, 82 are illustrations in single lines of the tracery of Gothic windows of which the lines of construction are left to assist the draftsman in completion of the design, which will afford excellent practice in the intricate work of making lines tangent to each other. DRAWING INSTRUMENTS. DRAWING INSTRUMENTS. 1 X X ! ! y y V j x x X X "> j y x X X 1 gj X \ ; x y y ^ | y y y y X* y v ] y y v & y X V t 1 x y *> ( j 8 y V V i [ V y / V v j f \ V s f" v ^r V s [ v ,x X x. V p ! X / ^K X i a! A !, X v > Xj > s X c <. 2 * X ,x x l> ^ <, X X X ^s x^ KI x X > rf t X X ^ X /\ X *> < /\ X /s X X ) < X X s / >< X X X > < V X V X f x s < x i > < > < $ < > < > X x X p< X /s X > < /\ X /N X X s < x X X \ < X X s < X X X X X x X X V X r i < V X V X X V < X 80 DRAWING INSTRUMENTS. DRAWING INSTRUMENTS. 81 82 DRAWING INSTRUMENTS. PLOTTING. PLOTTING is the laying out on paper in plan, or horizontal projection, the boundaries of portions of the earth's surface of greater or less extent, from the notes of surveys or other records. When the extents are large, embracing de- grees of latitude and longitude, the plots are designated as maps ; but if of small extent, as lots, estates, and farms, they are usually designated as plans or plots. After completing the outlines, it is usual to fill up the plot with the charac- teristic features, geographical, geological, agricultural, industrial, and domestic, which are expressed conventionally, as will be shown under the head of " Topo- graphical Drawing." Scales. The choice of the scale for the plot depends on the purpose for which the drawing is intended. It should be large enough to express all de- sirable details which it is intended to illustrate, and the place it is to oc- cupy. Plans of house-lots and small plots of farm surveys are usually so many feet to the inch ; maps of surveys of States, so many miles to the inch ; and maps of railway surveys, so many feet to the inch or so many inches to the mile. Formerly the lines of farms were measured by the four-rod chain. Two to three chains to the inch was then a very common scale. On the United States Coast Survey all the scales are expressed fractionally and decimally. The original surveys are generally on a scale of one to ten or twenty thousand, but in some the scale is larger or smaller. The public sur- veys embrace three general classes: 1. Small harbour charts. 2. Charts of bays, sounds, etc. 3. General coast charts. The scales of the first class vary from go ^ 6 to 60 ^ 00 , according to the nature of the harbour and the objects to be represented. The scale of the second class is usually fixed at -g-^^n,-. Preliminary charts, are, however, issued of various scales, from -g-jj-J-j-o to 2 * . Of the- third class the scale is fixed at 4 fa 6 for the general chart of the coast from Gay Head to Cape Henlopen, although considerations of the prox- imity and importance of points on the coast may change the scales of charts of other portions of our extended coast. On all plots of large surveys, it is very desirable that the scales adopted should bear a definite numerical proportion to the linear measurement of the ground to be mapped, and that this proportion should be expressed fractionally on the plan, even if the scale be drawn or expressed some other way, as miles to the inch. The decimal system has the most to recommend it, and is generally adopted in government surveys. For railroad surveys, the New York general railroad law directs the scale of 83 84 PLOTTING. map which is to be filed in the State Engineer's office to be 500 feet to ^ foot, For canal maps, a scale of two chains to the inch, i g * 8 4 , is employed. In England plans and sections for projected lines of inland communication, or generally for public works requiring the sanction of the legislature, are re- quired by a standing order to be drawn to scales not less than four inches to the mile, 1 : 15,840, for the plan, and 100 feet to the inch, 1 : 1,200, for the profiles. In the United States engineer service the following scales are prescribed : General plans of buildings ...... 10 feet to the inch, 1 : 120 Maps of ground with horizontal curves 1 foot apart . 50 " " 1 : 600 Topographical maps, 1 mile square .... 1 mile to 2 feet, 1 : 2,640 Topographical maps, 3 miles square .... 1 " 1 foot, 1 : 5,280 Topographical maps, between 4 and 8 miles . 1 " 6 in., 1 : 10,560 Topographical maps, 9 miles square . . . .1 " 4 " 1 : 15,840 Maps not exceeding 24 miles square ..... 1 " 2 " 1 : 31.680 Maps comprising 50 miles square . . . .1 " 1 inch, 1 : 63,360 Maps comprising 100 miles square . . . .1 " " 1 : 126,720 Surveys of roads and canals ...... 50 feet to 1 " 1 : 600 Many government maps are made on a scale of -^oVo- or It is always desirable that the scale should be drawn on maps and plans, as they are often reduced by photography. In cities and towns, plots of lots and squares are generally rectangular, and they can be readily plotted on any convenient scale. Fig. 187 is a plan of the usual New York city lot, 25 X 100, on a scale of 20 feet to the inch, or -g-^. Fig. 188 is a city square containing thirty-two of these lots, on a scale of 100 feet to the inch, or 12 1 00 . The most accurate way is to plot the large rec- tangle 400x200 feet, and then subdivide it. Fig. 189 is a plan of the city squares, with the inclosing streets, on a scale 200 feet to the inch, or -y^Vff- But many lots and most estates are not rectangular, and these, the angles being recorded, must be plotted by the aid of a protractor. If the survey has been made by triangles, the principal triangles are first laid down in pencil by the intersection of their sides, the length being taken from the scale and described with compasses. In general, when the surveys have been conducted without instruments, the positions of the points on paper are determined by the intersection and construction of the same lines as has been done in the field. Surveys are mostly conducted by measuring the inclination of lines to a meridian or to each other by the compass or by the transit. In the survey of farms, where great accuracy is not required, the compass is mostly used. The compass gives the direction of a line with reference to the magnetic meridian. The true meridian can be obtained from the observations of the polar star or from the magnetic meridian corrected from the records of the variations by the geodetic surveys of the United States at the place and time. The plane table is very convenient for filling in the details of a survey when PLOTTING. 85 the principal points have been determined by triangulation, and its records are readily transferred to the drawing. At the left of Fig. 190 are the notes of a compass survey, from which the figure is plotted by drawing a meridian through each station and laying off the FIG. 187. angle of deflection. In small drawings it is more convenient, as shown in Fig. 191, to plot all the bearings on a single meridian and then transfer them to the places where they are wanted by any instrument for drawing parallel lines, or to lay off on a single meridian as many bearings as convenient and then trans- fer the meridian for another plot. If, as in Fig. 192, the plot fails to close that is, if the termination a of the last line does not join the commencement of the first line at 1, either the sur- vey or the plotting is incorrect. If the latter be correct, the error of the sur- vey must be balanced, or distributed through the lines and angles of the plot (Fig. 192). Connect 1 with a, and draw lines parallel to 1 a through 2, 3, 4, 86 PLOTTING. 5, of the plot. Draw an indefinite line, I a (Fig. 193), and on this, with any convenient scale, lay off consecutively the lines of the survey, 1-2, 2-3, 3-4, J FIG. 189. 5 ? 5_#. Erect perpendiculars at the extremities of the lines, 2, 3, 4, 5, and a. On the perpendicular a b, lay off 1 a from the plot and connect b 1. The 3.23 la -(5)- 3.55 cd -(4)- 222 -(8)- 1.29 -(2)- 2.70 -OH FIG. 190. intersections of the perpendiculars by this line will determine how much each of the points of the plot is to be moved on the parallels to 1 a to distribute the error. The dotted lines on the figure show the corrected outline. If the amount by which the plot fails to close is large, the plot should be resurveyed. PLOTTING. By the aid of the Traverse Table a plot of a survey may be balanced. The Traverse Table (see appendix) is a table of differences of latitudes and FIG. 192. departures, the difference of latitude between two stations being the difference north and south between them ; the difference of departure, the difference east and west. Thus, N S (Fig. 194) being the meridian, N and A B the course, A C is the difference of latitude, and A D the departure. The differences vary according to the length of A B, and the angle it makes with the merid- ian. Taking the field notes of the following sur- FIG. 193. vey, we make a table as follows of the stations, bearings, and distances, leaving columns for latitudes and departures : STATION. Bearing. Distance. LATITUDES. DEPARTURES. N. S. E. w. 1 N. 52 B. S. 29f E. S. 31| W. N. 61 W. 1,063 410 769 713 655 346 356 654 &38 203 405 624 2 3 4 Find by the Traverse Table the number of degrees of the angle or bearing on the left-hand side of the page if less than 45, and on the right-hand side if more. The numbers on the same line running across the page are the latitudes and departures for that angle and for the distances which may represent any 88 PLOTTING. unit, as feet, chains, links, metres, etc. The traverse table gives the latitudes or departures for a single unit ; 10, 100, 1,000, or any other decimal quantity may be obtained by moving the decimal point one, two, three, or more places to the right. Thus let us take station 1 in previous survey, in which the latitude and de- partures of a course having a distance of 1,063 feet and a bearing of 52, and then take out the latitude and departure for 1, 6, 3, and place them as below : Distance. 1,000 60 1,063 Latitudes. 616-0 36-94 1-847 654-787 Departures. 788-0 47-28 2-364 837-644 If the survey has been accurately performed, the northings and southings of the latitude and the eastings and westings of the departures will balance and the survey will close. In the preceding survey they do not balance ; it there- fore becomes necessary to balance it. This operation consists in correcting the latitudes and departures of the courses so that the sums of the northings and southings of the latitudes and the eastings and westings of the departures shall be equal. This is done by distributing the difference of their sums among the courses in proportion to their length. The difference between the northings and southings of latitude, which is 9, is divided by the total length, 2,955, which gives the amount per foot to be added to the lesser column and subtracted from the greater column in propor- tion to the length of the courses to cause the northings and southings to balance. The departures are balanced in a similar manner. The following table gives the original latitudes and departures and the cor- rected ones : i^. 09 to M Stations. Bearings. Dis- tances. LATITUDES. DEPARTURES. CORRECTED LATITUDES. CORRECTED DEPARTURES. N. S. E. W. N. S. E. vv. N. 52 B. S. 29J E. S. 31f W. N. 61 W. 1,063 410 769 713 655 "346 "356 654 838 203 658 "355 651 834 201 408 627 405 624 "348 2,955 1,001 1,010 1,041 1,029 1,006 1,006 1,035 1,035 After the latitudes and departures have been corrected, it is necessary to make a drawing of the plot. How this is done will be readily seen by the accom- panying illustration of this survey (Fig. 195). This figure also illustrates a very convenient and accurate method of determining the area of the survey mathematically. By means of the latitudes and departures the area of the full parallelogram is taken, and the triangles on the four sides of the plot are deducted from it, leaving 489,245 square feet as the area of the figure. The use of the compass is now confined to the surveying of land areas of large extent and little value, or as a means of checking the bearings as taken by the theodolite or transit. Forcing should not be attempted with the latter in- struments. If the survey does not balance almost exactly, it should be resur- PLOTTING. 89 veyed ; otherwise it could not be used in a court of law except as approximately correct. The steel tape divided decimally is almost exclusively used in accu- rate work. The system of plotting by traverse is the same for the survey by transit as Pep. 834 *> Dep. 20l' Dep. 627' Fio. 195. by compass, except as the angles are taken to minutes and seconds. The latitudes and departures are to be taken by logarithmic sines and cosines ; if these are not obtainable, the table for natural sines and cosines in the appendix will give minutes, and seconds can be obtained by interpolation of differences. Fig. 196 is the plot of a survey by transit. Any side of the plot may be assumed as a meridian. The bearings are always taken to the right of it.. After it has been plotted it can be checked by the traverse. Meridians de- scribed through each of the angles will show the meridional angle, tudes and departures may be obtained as follows : The lati- Angle. Nat. sine. Distance. Departure. 41 40' 0-66480 X 350 = 233 Angle. Nat. cosine. Distance. Latitude. 41 40' 0-74703 X 350 = 261 In the third line of the third column the angle, instead of 120, is set down at 30, because, when an angle is in excess of 90, 180, or 270, the ex- cess is the angle of which sine and cosine are to be found. There can be no division of distance into latitude and departure when the course is either at right angles to or parallel with the meridian. It is then 90 PLOTTING. FIG. 196. either all departure or all latitude. In the tables the latitudes are identical for angles and for their supplements, and so are the departures. Reference to Fig. 75 will illustrate this, calling the sine latitude and the cosine departure. Course. Azimuth. Angle. Dis- tance. Latitudes. Depar- tures. Triangles deducted. Rectangles deducted. 0-1 41 40' 41 40' 350 261 23R 261 x 233 _ 30106 1 2 85 30 85 30 280 22 279 2 22 x 279 _ g 069 233x22 = 5,126 2-3 120 00 30 00 320 160 277 2 277 x 160 _ 00160 3-4 154 29 64 29 300 271 129 2 129 x 271 _ 17479 129 x 160 = 20,640 4-5 228 00 48 00 700 469 520 2 5-6 288 30 18 30 420 133 3Q8 2 133 x 398 O g 16? 6-0 360 00 00 00 484 484 000 2 221,521 25,766 Circumscribed rectangle, 918 x 900 = 826,200 Deduct 221,521 + 25,766 = 247,287 578,913 square feet. PLOTTING. 91 When it is difficult to measure along the boundaries of an estate, the sur- veys should be made along more convenient and accessible lines, which may be by a closed plot, as in Fig. 196, or by base lines from which the intersections of boundaries are established by offsets carefully determined by measures and angles from points of the survey. Fro. 197. The first work of the draughtsman is to complete the plot along the lines of the survey; work up the estimate of contents by traverse, and check by measures on -the plot. Fig. 197 is an illustration. Find the cosine 49 40' distance 215 = 140-1 sine 163-1 " 55 25' " 152= 86-3 " 125-1 226-4 Line 525226-4 = 298-6 = 301-0 the line of plot. 38 = 12708 = Bine of 7' 18' 90 -7 18' = 82 42' 90 - 49 40' = 40 20'. By similar construction 34 30' and 78 30' are calculated. 360- (82 42' + 40 20' + 34 30' + 78 30') = 123 58'. The line of the plot, 301, and the adjacent angle, 123 58', are thus ob- tained, and all lines and angles of the plot are established in the same way. The plot is then transferred to a clean sheet, with lines and angles as calcu- lated, but without any lines of survey. When the lines of a plot are irregular, as in Fig. 198, divide the plot into equal spaces, and draw parallel lines across the figure through the points of division, add together the two extreme lines, divide the sum by two, and to this dividend add the lengths of the other lines and multiply their sum by the 92 PLOTTING. equal vertical distance between the parallel lines, which will give very closely the entire area. Having completed the plot, that is, the main lines of the survey, the filling of other points may in general be done on paper in the same way as they have been established in the field. Intersections of the main lines by roads, streams, fences, and the like are measured off ; other points FIG. 198. FIG. 199. not intersecting, are usually fixed by triangles or by offsets, or lines run on purpose by angles from the main lines. In case of unimportant lines, as the crooked brook, for instance (Fig. 199), offsets are taken to the most prominent angles, as a a a, and the inter- mediate bends are sketched by eye into the field- book, and similarly on the plan. The most rapid way of plotting the offsets is by the use of a plotting and offset scale (Fig. 200), the one being fixed parallel to the line A B from which the offsets are to be laid off, at such a distance from it, that the zero-line on the movable or offset scale coincides with it, while the zero of its own scale is on a line perpendicular to the position of the station A from which the distances were measured. In the field-book all the offsets are referred to the point of beginning on any one straight line. Move the offset scale to the first distance by the scale at which an offset has been taken, and mark off the length of the offset on its corresponding side of the line ; establish thus repeated points, and join the points by lines as they are on the ground. It may not always be pos- sible to obtain the same scales as those of the plan ; but they may be made of thick drawing-paper or pasteboard. For extensive plotting, as in govern- ment surveys, the offset scale may be made to slide in a groove upon the plotting scale. In protracting the triangles of an extended trigo- nometrical survey in which the sides have been cal- culated or measured, it is better to lay down the triangles from the length of their sides ; for ordina- ry surveys, the triangulation is most expeditiously plotted by the means of a protractor. PLOTTING. 93 The outlines of the survey having been balanced and plotted in, with the subsidiary points, as established by offsets and by triangles, the filling in of the interior detail, with the natural features of the ground, from the skeleton or suggestions in the field-book or other records, is done according to conventional signs, to be shown under " Topographical Drawing." The public lands of the United States are surveyed, mapped, and divided into nearly square tracts, according to the following system : Ranges. Standard lines must first be determined from which to measure. Accordingly, in each land-district some meridian line is run due north and south ; this is called the principal meridian. From some point of the principal meridian is also run a line due east and west, called the base line. Other lines are then run in the same direction as the principal meridian, at distances of six miles, measured on the base line, on each side of it. The strip between the principal meridian and the first line, thus run east of it, is known as Range 1 East, the second strip as Range 2 East, etc. And so on the west. This division is shown in Fig. 201. FIG. 201. j ? Tp.2 North tn . . S S 3 a w i? a ^ * 1 1 Tp.l * K* * * North W BASE LINK _j . Tp.l I ! i * South MERIDIAN PRINCIPAL Tp.2 South FIG. 202. Townships. In like manner, lines are run north and south of the base line at intervals of six miles. These lines cut at right angles those which separate the ranges, and with them form squares six miles on each side, called toiunslrips. Each township contains thirty-six square miles. The township nearest the base line on the north is known as Township 1 North, of the particular range it is in ; the next farther north is Township 2 North, of that range, and so on. In like manner, going south from the base line, we have in succession Township 1 South, Township 2 South, etc. (Fig. 202). Sections. Each township is divided into thirty-six squares, called sections, each one mile long and one mile wide, and therefore having an area of one square mile. The sections of a township are numbered 1, 2, 3, etc., up to 36, PLOTTING. beginning at the northeast, and running alternately from right to left and from left to right, as shown in Fig. 203. A section may be subdivided into half-sections, quarter-sections, eighths, and sixteenths, designated as in the example that follows : Let F G (Fig. 204) be Section 3 of Township 2 North, in Eange 1 West ; then 6 5 4 3 2 1 7 8 9 10 11 12 18 17 16 15 14 13 19 20 21 22 23 24 30 29 28 27 26 25 31 32 33 34 35 36 1 mile. D E FIG. 203. FIG. 204. A is N. (north) of Section 3, Township 2 North, Range 1 West. B is S. W. (southwest) of Section 3, Township 2 North, Eange 1 West. C is W. (west) of S. E. (southeast) of Section 3, Township 2 North, Range 1 West. D is N. E. i of S. E. i of Section 3, Township 2 North, Range 1 West. E is S. E. i of S. E. i of Section 3, Township 2 North, Range 1 West. Correction Lines. If the meridian lines were parallel to each other, the townships and sections would be exact squares. But as these lines gradually converge toward the north, meeting at the pole, the townships deviate some- what from squares, being narrower on the north than on the south ; and the northern sections of a township are a little smaller than the southern ones. In order that the townships of a range may not thus keep getting smaller and smaller as we go toward the north, a new base line, called a correction line, is taken at intervals, differing in length in different land-districts, and new north- and-south lines are run at distances of six miles measured on the correction lines. The system of survey described above is not used in Texas, the public lands there being State property. TOPOGRAPHICAL DRAWING. TOPOGRAPHICAL DRAWING is the delineation of the surface of a locality, with the natural and artificial objects, as houses, roads, rivers, hills, etc., upon it in their relative dimensions and positions, giving, as it were, a miniature copy of the farm, field, district, etc., as it would be seen by the eye moving over it. Many of the objects thus to be represented can be defined by regular and mathematical lines, but many other objects, from their irregularity of out- line, it would be very difficult thus to distinguish; nor are the particular irregularities necessary for the expression. Certain conventional signs have therefore been adopted in general use among draughtsmen, some of which resemble, in some degree, the objects for which they stand, while others are purely conventional. These signs may be expressed by lines, by tints, or by botb. Figs. 205 and 206 represent meadow or grass land, the short lines being FIG. 205. FlO. 206. FIG. 208. supposed to represent tufts of grass ; the bases of the tufts should always be parallel to the base of the drawing, whatever may be the shape of the in- closure. Figs. 207, 208, 209, and 210 give various methods of representing trees. Figs. 207 and 208 represent in plan a forest and an orchard respectively. The FIG 209. FIG. 210. FIG. 211. method of Figs. 209 and 210, showing the same in elevation, while it is not consonant with the projection of the plan, to many is more expressive and in- telligible. 95 96 TOPOGRAPHICAL DRAWING. Fig. 211 represents cultivated land. The lines are supposed to represent plough-furrows, and adjacent fields should be distinguished from each other by different inclinations of lines. Figs. 212 and 213 represent marsh or bog land. Fig. 212 is the more ordi- nary mode of representing fresh- water bog ; Fig. 213, salt marsh. FIG. 213. FIG. 214. Fig. 214 represents a river, with mud and sand banks. Sand is designated by tine dots, made with the point of the pen ; mud by a series of short parallel lines. Gravel is represented by coarser dots, and stones by irregular angular forms. Water is almost invariably represented, except in connection with bogs, by drawing a line parallel to the shore, following its windings and indentations closely, then another parallel a little lighter and a little more distant, a third still more so, and so on. Brooks, and even rivers when the scale is small, are represented by one or two lines. Fig. 215 gives a plan and sectional view of water, in which the white curves represent the character and direction of the FIG. 215. Fio. 216. flow of streams, retarded at bottom and sides, and more rapid near the surface and at centre. The direction of the current may also be shown by arrows. Fig. 216 represents a bold shore bounded by cliffs. TOPOGRAPHICAL DRAWING. 97 Fig. 217 represents a turnpike. . If the toll-bar and marks for a gate be omitted, it is a common highway. Fig. 218 represents a road as sunk or cut through a hill ; Fig. 219, one raised upon an embankment. Fig. 220 is a rail- Via. 217. FIG. 218. FIG. 219. FIG. 220. road, often represented without the cross-ties by two heavy parallel lines, some- times by but one. Fig. 221 represents a bridge with a single pier ; Fig. 222, a swing or draw bridge ; Fig. 223, a suspension bridge ; and Fig. 224, a ford. Fig. 225 is a lock FIG. 221. FIG. 222. FIG. 223. FIG. 224. of a canal. Canals may be represented like roads, except that in the latter the side from the light is the shaded line ; in the former, the side to the light. Or by Conventional signs for the more important ob- jects that are likely to need representation on a map are : Saw-mill, FIG. 225. Signal of Survey, A Telegraph, $MP Court-house, III Post-office, jjj% Tavern, ^J^ Blacksmith's shop, ^L Guide-board, Quarry, ^ Grist-mill, Wind-mill, Steam-mill, Furnace, Woolen-factory, Cotton-factory, Dwellings, Churches, Grave-yards, HE CURRENT Anchorage for ships, Anchorage for coasters, J^, Rocks always covered, ^ 8 Buoys, f \ Wrecks, Harbors, Light-house, Signal-house, Channel-marks, 98 TOPOGRAPHICAL DRAWING. The localities of mines may be represented by the signs of the planets, which were anciently associated with the various metals, and a black circle is used for coal, thus, $ Mercury, ? Copper, ^ Lead, D Silver, Gold, $ Iron, 21 Tin, Coal. The Representation of Hills. The two methods in general use for rep- resenting with pen or pencil the slopes of ground are known as the vertical and the horizontal. In the former (Fig. 226), the strokes of the pen follow the course that water would take in running down these slopes. In the second (Fig. 227), they represent horizontal lines traced round them, such as would be shown on the ground by water rising progressively by stages, 1, 2, 3, 4, 5, 6, up the hill. The last is the more correct representation of the general character and features of the ground, and, when vertical levels or contours have been traced by level at equal vertical distances over the surface of the ground, they should be so represented ; or when, by any lines of levels, these contours can be traced on the plans with accuracy, the horizontal system should >be adopted : but where, as in most plans, the hills are but sketched in by the eye, the verti- cal system should be adopted ; it affords but proximate data to judge of the slope, whereas, by the contour system, the slope may be measured exactly. It is a good maxim in topographical drawing not to represent as accurate any- thing which has not been rigorously established by surveys. On this account, for general plans, when the surface of the ground has not been levelled, nor is required to be determined with mathematical precision, use the vertical system of representing slopes. On drawing hills on the vertical system, it is very common to draw contour- lines in pencil as guides for the vertical strokes. If the horizontal lines be traced at fixed vertical intervals, and vertical strokes be drawn between them in the line of quickest descent, they supply a sufficiently accurate representa- tion of the face of the country for ordinary purposes. It is usual to make the vertical strokes heavier the steeper the inclination, and systems have been pro- posed and used by which the inclination is defined by the comparative thick- ness of the line and of the intervening spaces. FIG. 226. Fio. 227. TOPOGRAPHICAL DRAWING. 99 In describing ground with the pen, the light is generally supposed to descend in vertical rays, and the illumination received by each slope is di- minished in proportion to its divergence from the plane of the horizon. Thus, in Fig. 228, it will be seen that a horizontal surface receives an' equal portion of light with the inclined surface resting upon it, and, as the inclined surface is of greater extent, it will be darker than the horizontal in propor- tion to the inclination and conse- quent increase of the surface, and on this principle varied forms of ground are represented by proportioning the FIG. 228. thickness of stroke to the steepness of the slope. In the German system proposed by Major Lehmann for representing the slopes of ground by a scale of shade, the slope, at an angle of 45, is indicated by black, the horizontal plane by white. A modification of Lehmann's method, proposed by the United States Coast FIG. 229. Survey, has the advantage of discriminating between slopes of greater inclina- tion than 45. The table gives the proportions of black and white for different inclinations, and the construction may easily be un- derstood from Fig. 229. Contour - Lines. Conceive a hill to be com- pletely covered with water. Then suppose the water to be drawn down, say five feet at a time. Each line of contact of the hill and the water will be a contour-line, or a line every point of which is at the same height or level above a fixed horizontal plane, called the datum-plane. For a small hill, stake out the ground in squares of say fifty feet to the side, and take levels at each point of these squares, and as many intermediates as the change of slope makes necessary. To draw the map, lay off these squares to a scale, and mark the elevation of each point and the intermediates in pencil. Then by the eye draw in the contours at such vertical distances apart as the requirements of the map call for. For a large survey, say of a mountain, such a method is impracticable. In this case, the surveyor fixes a number of points at the same level, the points being absolutely estab- lished by the transit or compass, so that they can be plotted accurately. Con- nect all points on each level, and fill in the distances between by the eye, on the supposition that the slope is uniform between these lines. The lines absolutely Slope. Propor Black. tion of White. 2 1 or 2f 1 10 5 or 6 2 9 10 or 11 3 8 15 or 18 4 7 25 or 26 5 6 35 6 5 45 7 4 60 8 3 75 9 2 100 TOPOGRAPHICAL DRAWING. established and those merely sketched in must not be confounded, and should be distinguished apart either by colour, by size of lines, or by dotting. The contour-lines denoting every five, ten, etc., feet above the datum or plane of reference may be numbered with such height. This is an effective way of rep- resenting hills, but is only to be recommended when lines have been traced and it becomes a record of facts. Fig. 230 represents, on double the scale, the FIG. 230. half of the hill (Fig. 227), with one half completed by drawing the interme- diate contour-lines. The objection to the drawing of hills by any system is that the depths of shade representing different slopes conflict with the lights and shades of the TOPOGRAPHICAL DRAWING. 101 drawing, and are therefore confusing. The plan adopted by Von Eggloff stein in his maps was to form a model by cutting out of sheet-wax under the needle of a sewing machine, on the lines of contours, and then properly superimposing them on one another. A mould was then taken from them in plaster. A FIG. 231. model from the mould, also in plaster, was then taken. This was watered while fresh by a vertical rain from a water-pot, which broke down the vertical edge of the contours, and gave natural lines of watershed. This model was then photographed under an inclined light, and gave an admirable projection. Fig. 231 is a contoured map of Greenwood Cemetery and vicinity, Brook- lyn, N. Y. Fig. 232 is a map of the harbour and city of New Haven, reduced from the charts of the United States Coast Survey. Plate VI is a map of a farming country. These two maps illustrate^the practical applications of topographical conventionalities. r-, /A : 102 TOPOGRAPHICAL DRAWING. FIG. 232. TOPOGRAPHICAL DRAWING. 103 Railway Surveys are usually plotted by tangents. The curves are then put in, and the topographical features' for the width necessary. The curves are designated by degrees, as a curve of 1, 2, 3, etc., according as the angle subtended at the centre by a 100-feet chord is 1, 2, 3, etc. Knowing the tangent points, it is easy to plot in the curve, as the centre of the curve must be the intersection of the perpendiculars to the tangents at these points ; or, with one point of tangency, erect a perpendicular at this point, and lay off the radius on it to get the centre of the curve. When the curves are larger than can be de- scribed by the dividers or beam compasses, they can be plotted as shown in geometrical problems, or points of a curve may be obtained by calculation of their ordinates, and the curves drawn from point to point by variable curves. Knowing the central ordinate of the curve between two points, the central ordinate of one half that curve will be approximately one quarter of the first ; but the greater the num- ber of degrees in the arc, the less near to the truth is the rule. ^, 3l.43PeAEattperSlilt ^, Level Degree. Radii, ft. Central ordinate. 1 5729-65 0-218 2 2864-93 0-436 3 1910-08 0-655 4 1432-69 0-873 5 1146-28 1-091 6 955-37 1-309 7 819-02 1-528 8 716-78 1-746 9 637-27 1-965 10 573-69 2-183 FIG. 234. Fig. 234 represents a plot of a railway line ; in this plot the curve is repre- sented as a straight line, the radius of curvature being written in. This method is sometimes adopted when it is desirable to confine the plot within a limited space upon the sheet, and it is convenient plotted thus directly beneath the profile or longitudinal section (Fig. 233). In plotting the section, a horizontal or base line is drawn, on which are laid off the stations or distances at which levels have been taken ; at these points perpendiculars, or ordinates, are erected ; upon them are marked the heights of the ground above the base ; and the marks are joined by straight lines. Where borings or soundings have been made, and it is necessary to indicate the character and define the limit of the material, the rock may be shown by diagonal hatchuring, streams as in Figs. 222 and 223, and other substances by a combination of lines and'dots, resembling as nearly as possible the material 104 TOPOGRAPHICAL DRAWING. which it is to represent, and the name inserted. If there is a bog or mud in which soundings have been made, the position and depth of soundings should be given ; but when work is to be done by contract, characteristics, unless well established, should not be definitely marked. Since it would be in general impossible to express the variations of the sur- face of the ground in the same scale as that adopted for the plan, it is cus- tomary to make the vertical scale larger than the horizontal, usually in the proportion of 10 or 20 to 1. Thus, if the horizontal scale of the plan be 400 feet to the inch, the vertical scale would be 40 or 20 feet to the inch. For the purpose of facilitating the plotting of profiles, profile-paper can be obtained from stationers, on which are printed horizontal and vertical lines. In the plotting of sections across the line which are extended but little beyond the line of the cut or embankment, equal vertical and horizontal scales are adopted ; these plots are mostly to determine the position of the slope, or to assist in calculating the excavation. When cross sections are extended to show the grade of cross-road, or changes of level at considerable distance from the line of rail, the same scales, vertical and horizontal, are adopted as in the longitudinal section or profile. In Fig. 233 the upper or heavy line represents the line of the rail, the grades being written above ; this is the more usual way, but sometimes, as in Fig. 235, the profile and plan are combined ; that is, the heights and depths above and below the grade line of the road are transferred to the plan, and re- Fio. 235. ferred to the line in plan, which becomes thus a representation both in plan and elevation. Cross sections, for grades of cross-roads, etc., are usually plotted beneath or above the profile or across the line when plan and profile are combined. Besides the complete plans, as above, giving the details of the location, land plans are required, showing the position and direction of all lines of fences and boundaries of estates, with but very few of the topographical features. The centre line of the road is represented in bold line, and at each side, often in red, are represented the boundaries required for the purposes of way. In gen- TOPOGRAPHICAL DRAWING. 105 eral, a width of 100 feet is the amount of land set off, lines parallel to the cen- tral line being at a distance of 50 feet on each side ; but when, owing to the depth of the cut or embankment, the slopes run out beyond this limit, the ex- tent is determined by plotting a cross section and transferring the distances thus found to the plan, and inclosing all such points somewhat within the limits as set off for railway purposes. These plans are generally filed in the register's office for the county through which the line passes. Hydrometrical or Marine Surveys. In plotting hydrometrical or marine surveys, the depths of soundings are seldom expressed by sections, but by figures written on the plan, expressing the sounding or depth below a datum FIG. 236. line, generally that of high water, the low-water line being usually represented by a single continued line. The soundings are expressed in fathoms or in feet. Fig. 236 is a map of Cape Cod Bay plotted by this method. The depths are expressed in feet, and the dotted lines are contour-lines or lines of equal depths. 106 TOPOGRAPHICAL DRAWING. An effective way of making a marine chart is to express the different depths by lines varying in direction, distance apart, width, etc. Fig. 237 is a chart of the Isle of Wight and the surrounding water, with the depths expressed as shown at the bottom of the cut. Sections are often used for rivers, especially rivers like those of the West, that have a very changeable bottom. By plot- ting sections, taken at different times, over one another, distinguishing Depth under 5 Fathoms. 5 to 10 Fathoms. 10 to 20 Fathoms. Over 20 Fathoms. 5 Miles. FIG. 237. them apart by a difference in colour and variety of line, the changes that take place in the bottom of the river, and the erosion of the banks, are boldly shown. In a geological profile the different rocks or formations are sometimes dis- tinguished by colours, explained by marginal notes and squares, but more often by marks, dots, or cross-hatchings. The geological and statistical features of a country may be expressed simi- larly and graphically in lines, as in Fig. 238, a preliminary survey of Kentucky, illustrating the principal geological features; and in Fig. 239, in a broader form, giving a larger extent of country, including the portion of the United States east of the Eocky Mountains and the southeasterly portion of Canada. These maps give the larger geological divisions, and are suited for books, but are not as effective nor comprehensive of the smaller subdivisions, of which Plate X is an example of a portion of a map of the State of New Jersey. TOPOGRAPHICAL DRAWING. 107 '4\ 108 TOPOGRAPHICAL DRAWING. FIG. 239. STRATIFIED ROCKS 1 . 1.1, L-l Sections of horizontal and inclined strata. Fio. 240. TOPOGRAPHICAL DRAWING. 109 Psycho Quater- nary. Tapir, Peccary. Bi Equus. Megatheri , Llama. Equus Beds. /fjjaiu, Tapiriu, Elefhat. Pliohippus Beds. P/iohipput, Mastodon, B