J 01

JOI

Jjet d be the centre of your chalked scroll in Figure 107 ;

which describe, with the projection of your mouldingsji-om Figure 106, the small circle d; take from Figure 106,o , le bigness of the stuff, as eg, or ef which add to the8 ®all circle, and form the circle hit, which is the bigness of,, e of the scroll : this done, take the distance from r, toe 'nside of the rail, as the supposed chalked scroll, which^Ppose k ; with it, make a diminishing

distance

your

scale, by setting thatProm * to l; draw the line k l; place one foot of4ivide° mpaSSes ' n describe the part of a circle <8, whiche Wk rt' nt ° e< l ua l parts, because here your supposed

re V oi . 8cr °H was to come into its eye, or block, at oneof rev Ut ! on .°f a circle. (Scrolls may be made to any number

in tv utlons desired, by the same rule, witness that above,

figure 108 .)

Cii-cl e lC ?. one of your compasses in d, describe the largey°n 8tl ../ ^ u ’ which always divide into eight parts, becauseint 0 th° ne ' ei g hth P art °f a c ' rc l e every time, till you comebiro- e * e y e> or block, ith; from the said divisions on theinect C '!' de ’ draw lines th rough, for on them your sectionsyour’" 'J 0 * 1 f° rtn the scroll. It is observable in drawingth® „,. eCtlon . 8 > that they do not end in the line drawn through’aside 6U c ' rde > on 'y the outside scroll; for those of theI snn D SC, °^ e ”d on a line drawn to each respective centre,fail o| ? S ^ A and B t° be two steps ; the rest I think cannotWldci, r' n ° oaderstood, by observing the letters and figures,Mr p°. VV , eac h part distinctly.”gather nce 8 a< l v l ce ) to make a scroll first of chalk, is alto-T| 1(i m ^’’geometrical, and therefore unworthy of notice.c ° n stru . ■ .°^ f° rm t n g it is of Italian invention. A similar

p°u rs 13 ua ed in describing the Ionic volute in Daviler’sitivcti ^ rc hiteeture, dated Paris, 1720. He ascribes the,? Ut > in our opinion, it is far fromTlie od t ' Iat a S reea ble variation of curvature required.e xtrci,i Uln ® next to the eye expands too rapidly towards theS-nit ,•> much more perfect method, and not very

^ is ‘ s tanf "r cons truction, is that published in the Joiner'sSc *o L l /’ “. “

hy Nicholson. See the articles Sfiral and

‘In

;u ' J "lS r make the squaring of a twisted-rail easy,

the plan E— - ^ U. 1„I01CU-1«I1 tUOJ, 5CC

Soiim p- * l 9 Ure 109, which is the same as that in the fore-Clll 'Ves *9 Ure 107, and find the point of touch, b. From these

W1

« A,' 0 * 1 ,' vll( ‘n

w ; noul< l must be traced out, in order to form a sweep,

, erf applied on the rake, is agreeable to this ofyou w’li figure 110. (It is first to be observed,l'ai^ . want wood extraordinary, both on the top of? s 9, / t> ) ,' n Figure 111, at e, a; and also under the same,

dl<! plan w h>ch, observe wliere your sweep begins,

• the en T r Jure h09, as at a c; also observe that o and n

C a “’’’nb! twisted

ns ^

r 0r a

part. Therefore, from a to n, divideno° P e< l u al parts, so as to transfer them on some2, from a to n ; also divide the inside of 109,°; mto equal parts, so as to transfer them on

c to

> as

in 113,‘from* c too; take the distance e a,pitchV M’phy it to the pitch-board, as from g to e ; take thed 9, i >md > U 4, with its place e to c, in 113 ; draw the lineParts . i ma he the point s ; divide from d to s into eight equa"’hioii r fl '°m d to o into the same number ; draw the lines,orm a sweep, whose use shall be hereafter shown,in nowise take the pitch-board, 114, and apply e to a,di vid e | dl ' a w the line e p, and make the point r; from e to rdp a\v , ' Uo ei ght equal parts ; also from e to n do likewise ;haw a, Sht lines from each division : that curve showsHich d ‘ Wood is wanting on the back of the rail, as 6 i,

’n

Siess

3ci 'ibe

of

la Hi, from e to a ; and there describe thevmay l 6 rad ’ which shows how much wood is want-0l -. n/ e °bserved by what was said above. The other

part of the twist is cut out of a parallel piece, as 115 ; whichthickness extraordinary is shown in 111, at e a.

“ To square the twisted part of the rail, having so muchwood extraordinary on the top and bottom, observe in 109,from a to e, and from c to f must be traced as was abovementioned. Takeaein 109, apply it to the pitch-board 114, itshows g i, which length place in 110, from k to i; also, takefrom 109 the distance b d, apply it to the pitch-board 114, itshows g m, which length place in 110, from l to m. Thisdone, trace out the raking-mould 110, agreeable to the plan109, which, by inspection and a little practice, will becomeeasy, and without which nothing is known truly. I say, thewood extraordinary being accounted for in 111 both on thetop and the bottom of the rail, observe to place yonr stroke fin its true place, that is, at the beginning of the twisted part;take the raking-mould 110, set. i toy in 111 ; there strike itby ; with the angle of your pitch-board describe the prickedline f, by the side of the rail ; then apply the mould 110 tothe bottom ; set i to this pricked line, and there describe byit, with your pencil. Lastly, cut that wood away ; also, cutthe remaining part of the scroll out of the block, as 115 ;then glue these together, and bend both moulds, 112 and113, round the rail ; strike them by that, and cut the woodaway ; so will the back of your rail be exactly square, andfit to work.”

This method of squaring the twist of the scroll is correct ;the principle is that of the section of a curved prism at rightangles to a given plane, and amounts to no more than tracinga common angle-bracket. The construction, however, re-quires a very considerable addition to the thickness of stuff;and even this thickness will be variable, according to theplace of the pitch-board. This method, though muchsuperior to that of Halfpenny, is not to be compared withthat of springing the plank, introduced by Mr. Nicholson.

Mr. Price says, that his method will apply to any twistor wreath whatever : we grant that it will ; but then thestuff would require to be from 4 to 8 inches in thickness, andsometimes more. In drawing the section upon the plank, inorder to be cut out, the shank of the mould is always appliedparallel to the arrises ; this application occasions also a greatwaste in the breadth as well as in the thickness. In theconstruction of the face-mould of the scroll, he employs thepitch-board of the flyers. He gives no example of forminga wreath over winders ; but if the same principle is to beapplied, recourse must be had to a development of the steps.

It is unnecessary to make any farther observations, as theauthor of the Architectural Dictionary, Mr. Nicholson, hasplaced these and his own before his readers, in order to com-pare and point out the specific differences of each, by properdiagrams, at the end of this article.

“You are always to observe this general rule, viz., toconceive each respective paragraph, as it occurs, before youbegin another ; the neglect of which appears by some whocannot conceive the particulars of the foregoing Figure,although I had put it in so clear a light.

“ I have here described three distinct methods of squaringthe twisted part of a rail, which may be known, and the railsquared, with more ease than in the foregoing Figure. Butwhen done, they will not have that agreeable turn in theirtwisted part as they would have, if done by the foregoingunerring rule, as may more clearly appear by the followingexplanation :—

“That of Figure 116, is the raking-mould, taken fromFigure 110 (whose use and application was therein clearlyshown) ; that of 117, is the pitch-board, taken from 114;which gives the rake or declivity of the rail.

“ In Figure 118 is shown how to square a rail, without