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bo !l° ra ^ *° a ’ ft' 0111 which drop perpendiculars on yourdri ■ ®’ ® rst fixed at as many places as you please ; thereari j' e , ln nails, and bend a straight rod till it touch them all;to \ v* 1 ’ W ' tb a pencil or chalk, describe the curve so formed,and^tt' 0 *- 1 ^ r ' n! ? the boards to be nailed on these little centres,p. 'eir joints will form a straight groin.”sun l ^ Ure “ Let c be a plan of greater extent, and which,g pose to be supported by two piers, as f l. The section dC u r Corn P ose d of entire semicircles, then consequently yourbe fl 68 tbe sect ' on e will be elliptical, as bnd, and mayth;« escr ' be d with a trammel. What was said in A explains„ jt one view.

Sec ,. these pillars should be in the way, view the plan andhein° nS a ® a ' n : fi rs t, form the principal curve, as D at aghb,a „ j® an ellipsis, so that the centres will be a Gothic sweepas tthe windows, as eg a; trace the curve dhb in e,an q a .j e to eg a in d, with which centre it, as shown in a,ce make good your groins to the sides: lastly, make a flatProfil 6 ’ 88 at ff hik, which flatness is shown in either of theCotn , es or sections d and e, and fix it on your centres beforeand h wb ' cb doubtless due inspection will make plain,« you avoid the pillars, which are equally firm,

heitnr p cause °f these centres against the windowsWh 0 f a '*°thic arch, proceeds from their making part of theWtVrfP or aroh > which though it does not add to itsAft ^ ^° es t0 ' ts s t ren gth in a particular manner.”a mere r S ^ 10w ' n S how to find the groined lines, as it were byHues me 5 kan >cal process, the method of finding the groinedbe ,°Y he bod y centre, he then shows how the same may^°°ked ^ u P on true geometrical principles, which may bes offit8 U P° n as the foundation of all kinds of cylindrical

for Va ^? ard l n g variety, I have given here another methodr eade r s ’ a ® d which, indeed, may give more pleasure to thea Ppear &S be '. n § a curiosity never before published, and mayh'telligible than that in the foregoing.”

° 0ni posed e " View the plan G and its section h, which is*hi ch i ° ent ' re semicircles, asbfe: see also the section i,Uothi n£r S - an fe "ipsis traced from b f e in h; but for use,“ Sgg 1 ?, r . nore true than the trammel.

Scribed P' an again, and also its section i, from which isSei uicir cu i t ie curv ilinear face k, and also the face of theWa“ arches > as l, all being alike. And this is whathe straight^ ac< : urate method for finding the groin, so as totule wher R Ver ' ts base > and at the same time gives a standardWhatever im* 0 aecoun t for any curve, or face of a ceilingn. 8ly in to unpl curve in iJs divided regularly, though seem-plan o Une< l ua ^ parts, which being drawn to the groin in•?* which T appears b y the figures 1, 2, 3, 4, 5, 6, 7, 8, 9,Clr cle b f e - are transferred into l at 1, 2, 3, &c. Also theCo Useq Uen ti ln . B ' s divided into eighteen equal parts; the half°? et hod d01] L? to n ine, which appears from b to e in L. Thisther expl anat - less W 'U be plain, and therefore needs no far-

Tii a t .a *

y thatof T K b ? lon S s to the section i, extended as it were,^etched , e l°ngs to one of the small arches of h, alsoHere it *’ the y being aH alike.”a USt °^ serve ^> that he has stretched out the

?d he has p T f no use > the covering only being wanted,n n ° at k Y,. e aded all the compartments of the plan inecess ar y. ’n 'eh is absurd, one of each being all that isy two contia ” 6y c annot be extended in contiguity, nor■P'ay be ,f U ° Us P ar t8 on the plan, though each adjoining

th T 0 g 6 se P arat ely.

Ere ct at - the gr . oin by a more common method, doer °f the pj S ra ] gbt P' ece of a board, or the like, on theer * be groin springs from, and drive in a nail2 b

at tlie point of the groin’s meeting, on which fasten one endof a chalked line, straining it tight, slide it down the side ofthe said straight piece, and it will form the groin so as tostand perpendicularly over its base.”

Mr. Price then proceeds to the methods of covering theparts of coved ceilings adjoining the angles, and also thecoverings of domes, as follows:

Plate VIII. Figure 1. “ Suppose m to be the plan of aceiling, as a b c d, and it is required to have a large frame,gulochi, or pannel. —First, produce some side or end of theroom, as n. Let it be required to describe the curvilinearface of the cove. The extent of the end of the said roomis a bf e, and it is coved one-fourth part of the height,at mb. The said frame or panel being gh; the quartercircle mg is divided into eight equal parts, which are trans-ferred to p, so that m g hi is the face of o, as stretched or «extended out, on which anything proposed to be described |therein may be truly performed. |

Figure 2. “ In Q is shown the plan of a niche, or dome:if a niche, let it be demanded to be fineered with walnut-tree, &c. If a dome, let it be required to be covered withboards or lead. Divide it into any number of parts, as hereinto nine, which transfer to s, as appears from h to l. Describethe section also, as R, being a quarter of a circle, whichdivide into any number of parts, as here into five, as isshown in the figure from h to i, which transfer in the plan Qfrom a to f; middle some one division, as from 4 to 5; thentake those distances from R, and transfer them to s, as fromf to 5, so that each division is halved or middled, as f a,f a :on these lines place the distances from Q, as at e, d, c, b,to 1, 2, 3, 4, in s, and these will form such curves asshall meet. ,

“ N.B. The more parts it is divided into, the better andtruer it will be performed.”

In this description, he is far from being clear, as we shallhere explain. “ Take the distances from R, and transferthem to s, as from f to 5.” But the extent of the line fromf to a at s does not contain the whole stretch of the arch h iof the section r, as it contains only four of the equal parts,whereas there are five; one part should have been describedto be below the line f ff &c., as the diagram s shows. Thewords “ so that each division is halved, as, f a, f a,” fyc., haveno meaning. “ On these lines place the distances from Q, asat e, d, c, b, to 1, 2, 3, 4, in s, and these will form such curvesas shall meet:” this is extremely obscure, and ought to havebeen thus described: From the points b c, d e, in q, describethe several arcs meeting each of the radii af and a 4j thenat S, through the divisions, 1, 2, 3, 4, draw lines at rightangles; upon these lines, and on each side of the said points,

1, 2, 3, 4, set off the several arcs at Q, beginning with f 4,at the bottom of s, and through the points on each side of theline f a describe the two curves, and the space comprehendedbetween them and the bottom line is the board required.

It must he observed, that though it is sometimes conve-nient to detach the parts of a diagram when it would occupytoo much space, it is by no means so obvious as one con-nected figure. In this respect, Mr. Price is very obscure, intransferring to so many different figures.

He then shows the nature of oblique or rampant arches,the tracing of, and the manner of finding the base or seat ofthe angle ribs of an annular groin, as follows:

Figure 3. “ That of a, is supposed to be the mitre-bracketof a cove, whose projection is be; and the height thereofis a b ; the curve being a segment, or part of a circle, let itbe demanded to trace a curve from it, as B, which shall beagreeable thereto, if applied as a common bracket, e d beingits height, as before, and ef its projection; first, divide the