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449
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j°iii i' a ' vn from t to the point of section in o g produced ;H^t , w an 4 d n > produce mb to meet f g at a, and let d np. 1 « at e; then will abed be the section required.
^9ure 3.— To find the section of a right cone.of the circle abcdepgh be the base. Find the centre0 j> e c ' r cle, and draw through it G v, parallel to I O, cuttings attl at v , and the circumference at G and c; through the0p e Point draw st, perpendicular to io, cutting io at l,r at)t at R > and the circumference at a and e ; divide the quad-tvf 0 S A c > 0 e, e G, G A, into any number of equal parts, as'trough the points of division draw lines parallel to G vin a L > one on each side of, and parallel to A e, cutting o poutp an 4 s ; and the other parallel to g c on each side of it,of 0 p in u and w; draw Kiatz, each equal to the heightf es e oone ; draw pt, qt, sr, tt, cutting op in p, q, r, s, t* 1 ^ ectlv ely; also draw iz, uz, xz, wz, cutting op inOj make oi, ok, ol, om, on, respectively equal to
O l, o M, o N ; join p i, qk, r l, sm, and nt ; drawh q ^ v g, ufi t e, parallel to oi, cutting r 1 at a and e;and h, and ms at b and d; then abedef gh will
£,. e section required.
4. shows how the section of an oblique cone is
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the method is the same as for a right cone : excepttne intersection, b c, must be placed parallel to the
ft a ti at 'on; by which means the axis, G I, has the same incli-Pl to b c, which the axis has to the plane of the base.8t 0n ate 4. is exceedingly useful in finding the bevels of the
*t 0 ,
ln ®8 Of
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oblique cylindric arches, where the joints of the
r un in planes perpendicular to the axis of the cylinder.®hall here begin with the most simple case, which is6 q e 2. Let A b represent the axis of the cylinder, and letto 4 Present the plane of the arch ; draw a d perpendicular
ar| d make the angle, dae, equal to the inclination of4 of a stone with the horizon ; from the centre, a,
-, an }' radius, ae, describe the arc ED. Draw E c andA. jj j^rallel to a b, and c f parallel to A d ; join e f ; then ifthe a e ^ le under-side of the joint or bed in the intrados of®id e * 0 p > the angle, abf, will be the angle which the under-p. the joint makes with the face of the arch.
4.—Exhibits the bevels for a complete arch, con-of seven joints.
tlig pj e t—Shows the method of finding the joints when
111 ,
Wf Q| ^ riZon . Let A b represent the axis of the cylinder as11 c t ( . ’ B c the insisting-line of the side of the arch : produceGfj p > draw fg perpendicular to f c; make the angle,Wang e 4 Ua l to the inclination of the end of the arch, and the0 the horizon.
Pu!' re —Shows the joints for a complete arch.
*e<>t; 0 e Figure 1.—Exhibits the method of finding the°t a cone upon the general principles, as explained in°f this article.
pj^re 2—The lines for the section of a cylinder.t<f rj re 3—The lines for the section of a cuneoid.toiig re 4.-—Another method for finding the section of atl<e sin, 110 * 1 ’ s pl a ' n to inspection, the principles being nearlyas bef ore.
P; r „ re 5—Section of a right cone.p: IUr e g _p? Ur e 7,_
b—Method of the intersection of a plane fromP°’ nts > ar >3 the heights upon these points,a r e ®—Method of finding the section of the segment
^finder.
Pf'ncip
ex plained, it is presumed that, by barely inspectingVo£ - es > the methods of tracing them will be sufficiently
of the sides of the arch are not perpendicular to
-Section of an oblique cylinder.-Section of a right cylinder.
Vv P'lneiples and methods for these having been pre‘
5 x
obvious without having recourse to the references of theletters.
Plate 6. Figures 1, 2, and 3.—Method of finding the sec-tion of a right prism when the plane of the section is per-pendicular to one of the sides of the prism.
Figures 4, 5, and 6.—Method of finding the section of aright prism when the plane of the section is oblique to oneof the sides of the prism, according to three given heights.See Cylinder.
STILES, (from the Saxon, stigele,) in joinery, the verticalparts of a frame, into which the ends of the rails are fixed bymortises and tenons.
STILTED ARCH, an arch whose springing-line is abovethe impost, or which is raised, as it were, upon upright stiltsor props.
STILTS, (from the Saxon stcelean, supporters,) a set ofpiles driven into the ground-plot for the intended pier of a \bridge; the tops of which being sawn to the low-water mark,the pier is raised upon them ; a method formerly used, when ithe bottom of a river could not be laid dry. The stilts were !surrounded, at a few feet distance, by a row of piles, with jplanks laid close to them, after the manner of a coffer-dam ; Ithis was called a sterling, or jettee ; after which, loose stones, j&c., were thrown into the space till it was filled up to the jtop ; so as to form a kind of pier of rubble, or loose-work, Iwhich was kept together by the sides of the sterlings : thepiling was then paved level at the top, and the arches wereturned upon it. Most of the large old bridges in Englandwere erected upon this method; but the inconveniencesattending it are so great, that it is now quite exploded ; for,on account of the loose composition of the piers, they mustbe made very large and broad, otherwise the arch would pushthem over, and fall down as soon as the centre was drawn.This great breadth of the piers and sterlings necessarily con-tracts the water-way so much, as not only to incommode the jnavigation through the arch, from the fall and quick motion Iof the water, but it also causes the bridge itself to be in danger, jparticularly in time of floods; besides this, there is greatdanger of the pier bursting out the sterlings, which are alsosubject to decay and damage, from the velocity of the water,and the passing of craft through the arches.
STOCK, (from the Saxon stoc,) a boring instrument, con-sisting of a double crank, so that one end may rest againstthe workman’s breast, and the other upon the wood intendedto be bored. It is provided with several steel cutters, called !bits, of different dimensions, according to the holes to be jmade. It is, therefore, in London , called stock and bits, butin most country places, brace and bits.
STONE, (from the Saxon ston,) a hard mineral substance, inot soluble in water, employed in the construction of edifices; !of these there are various kinds, as described more largely 'under the article Material. j
STONE ARCH, an arch constructed of stone: the general !principles of the construction of which will be found under ithe article Masonry. j
STONE BRIDGE. In a former article, (Bridge) a 'general historical view has been taken, of the rise, progress, 1and present state, of bridge-building, exemplified in descrip- \tions of the most celebrated edifices of the kind, in various :parts of the world. Under the present head, the theory of ithe art will be principally considered ; and we shall availourselves of the permission granted to us by the late ThomasTelford Esq., to make considerable extracts from the ablearticle on this subject, written by him for the EdinburghEncyclopaedia.
“ The construction of a magnificent stone bridge, is justly