Of N I C H E S.
and complete the equilateral Triangle A hj, setthe given Breadth of the Pilaster, suppose i k,from A, to i, and from A to k, then drawingLines from. A to the first one, the next three,the next one, the next three, &c. in thetLine b I,they wilL divide the Line i k into its Flutes andFillets, as required.
Ex a mp. II. To divide the Flutes and Fillets with
Beads at the Angles, of any Pilaster, as Fig. B.
Draw a Lipe as mp at Pleasure, and thereinset 31 Parts as before, and then completing theequilateral Triangle B m p, proceed in every Re-spect, as in the preceeding Example. And herenote, That when the Lines representing the Flutesand Fillets of a Pilaster are thus drawn, on aDraught Board, &c. from those Lines, the Flutesand Fillets of all other Pilasters of greater Dia-meter may be readily found. As for Example :Suppose the Lines b f and a d, Fig. B were theDiameters of two other Pilasters. On any Point, inany Side, suppose on b, with an Opening equal tob /, describe the Arch g e, cutting the Side ofthe Pilaster in / ; then drawing the Line b f,the several Flutes and Fillets first drawn, will di-vide that Line in the fame Proportion ; and sothe Line a d the Diameter of the lesser Pilaster.
The Innes r t and q s, Fig. B, express thefame, in that Pilaster which hath Beads at itsAngles.
To represent the perspective Appearances of Flutes
and Fillets in the Shafts of Columns , Fig. C, D.
By Prob. XI. of the Ionick Order, describethe Flutes and Fillets in each Semicircle a g c,-and c b d, from whence draw perpendicularLines,which terminate with Arches, as# XX, &c, and.the Whole will be completed, as required,
Plate LV, LVI, LVIL0 / NICHES.
These three Plates contain six grand Designsfor Niches, of the Tujcan, Dorick , Ionick , Corin-thian and Composite Orders, whose Cavities, tho*here represented semicircular, may be made semi-elliptical at Pleasure when required ; and as theworking of the Heads of Niches, semicircular
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semi-elliptical, may be performed two differentWays, which are very curious, I shall thereforenow explain those Operations as follows :
Piate LVIII, Fig. K.
To form the Head of a semicircular and semi ellipti-cal Niche , by divers Thicknesses of Plank, Lee.glew’d together.
(1.) On the Surface of a flatPannel, &c. largeenough to contain something more than the Planof the Nich, describe a Semicircle, as 1 2 $,&c.14, tyd Fig. K, of the fame Diameter, as thatof the Nich. Take the Thickness of your Plank,&c. in your Compasses; and set that Distance onthe Semidiameter a a, from a to c, from c to e ,&c. and through the Points cegi, &c. drawLines parallel to the Diameter 1 a d. Take aPiece of Plank, as Fig. A, and with a Square,applied to its Edge about the Middle of itsLength, as at s; draw a Line, from the underto the upper Surface ; the Extreams of which, aretwo Centres -, on which you are to describe twoSemicircles ; the under one with the Radius a x ;the upper one with the Radius c 2. With a turn-ing Saw, cut obliquely through the two Semicir-cles; and then you will have done the firstThick-ness. Take a second Piece of Plank, as Fig. B;draw a Line on its Edge near its Middle, squareto both Surfaces; whose Extreams are two Cen-tres as before. On the under Centre thereof,with the (last) Radius, c 2, describe a Semicir-cle equal to the last (because the under Surface ofthis second Piece, is to be glew’d on the upperSurface of the first) and on its upper Centre,withthe Radius e 3, describe a Semicircle on the up-per Surface; then cutting through both Pieces asbefore ; the second Piece is done,
(2.) Proceed in like Manner, until the Wholeis complete ; the Operations of which are expres-sed by the several Semicircles 3, 3 : 4, 41 4, 4 \5, 5 ; (Ac. in the Figures C, D, E, F, G, I, K,L, M, N, O, which represents, the several Piecesof Plank as their respective Heights above the.Base 1 ad-, approach the Zenith of the Nich,(3.) Glew all these Thicknesses, one on theother ; and with a Compass, smoothing Plain,whose Arch is something quicker, than that os ',the Nich ; clear off and finish the Inside,
(4.) Ah;