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following purpose : “ divide the breadth into six equal partsfor pantiles, into seven for slates, and into eight for plaintiles ; then in each of these the whole number, wanting two,will be the height of the roof; that is, pantile slatesand plain tiles |, of the breadth of the beam.”

The following observations, with respect to the trusses ofroofs, are very judicious :

“ That the less in number the divisions or pieces are, thatcompose each truss, the stronger it is; for even the shrinkingof the wood will let a well-framed truss sag or drop in pro-cess of time; for which reason I cannot help recommendingEnglish oak, particularly for king-posts.” He recommendssquare bolts in preference to round ones ; “ for this reason :if you use a round bolt, it must follow the auger, and cannotbe helped ; by this helping the auger-hole, that is, takingoff the corners of the wood, you may draw a strap exceed-ingly close, and at the same time it embraces the grain ofthe wood in'a much firmer manner than a round one canpossibly do.” With respect to strapping, he observes; “ Ifit be objected that there is too much trust reposed on theiron-work, may it not be asked, if any common strap at thebottom of a king-post was ever known to break by continualpressure ? Witness the straps in a theatre, to which is fixeda prodigious weight.” With respect to timbers, he says,“ If purlins are used, they ought to be agreeable in numberto their supports “ but if bridged, need not be regarded.”

The following designs, which he shows for the fronts ofbuildings, which are required to have the ground story open,and supported with story-posts, may be useful to some:

“ In Figure 4, is shown the manner of a timber front,supposed to be open underneath, in form of an arcade. Andfor such open fronts, the foundation should be laid on reversedarches, which will strengthen it very much ; by this means,the ground bears between one post or pillar and the other,as well as under the same.

“ If on it you would have brickwork, or even stone, thensupport the bressummer, as is shown in Figure 5, whichmanner of framing renders it as strong between the. posts,or pillars, as it is directly on the same, and this seems suffi-cient to explain proper bearings for partitions.”

Mr. Price then proceeds to circular domes, and in theirconstruction shows, for the first time, how the purlins are tobe squared ; his description is as follows :

“ Of what has hitherto been described, nothing appears sobeautiful when done, as domes or circular roofs ; and, as faras I can perceive, nothing has appeared so difficult in doing,therefore it will be proper to speak something of them.”

Plate VII. Figure 1.—“Let b represent a plan, in whichlet b, b, b, be the plate on the supposed wall; and let c, c, c,be the kirb on which stands a lantern, or cupola; also leta, a, a, represent the principal ribs.

“ From the plan b make the section A; in which the kirbor plate b should be in two thicknesses; as also that of c;by which it is made stronger; and indeed the principal ribswould be much better to be in two thicknesses. The besttimber for this use is English oak ; because abundance ofthat naturally grows crooked. As to the curve or sweepof this dome A, it is a semicircle ; although in that point,every one may use his pleasure; and in it are described thepurlins d, e, from which perpendiculars are dropped to theplan b ; so that/is the mould the lower purlins are to be cutout by, before they are shaped or squared for use; and thatof g is the mould for the upper purlins. I rather show itwith purlins, because under this head may be shown themanner of framing circular roofs in form of a cone.

“ To shape these purlins, observe, in A, as at d and e,they are so squared, that the joints of the supposed small

ribs are equal. Observe, as at e, the corners of the purlin,from which the perpendiculars are let fall to the plan n-So that your purlin being first cut out to the thicknessrequired, as appears in e, and also to the sweep f; so thatk is the mould for the bottom, and l the mould for the top 5by which, and the lines for the corners of the said purlin e > 'the same may be truly shaped and squared.

“ N.B. This particular ought to be well digested, it beinga principal observation in a circular roof.

“ From the purlin d, in the section A, perpendicularsare dropped to the plan b j in which it appears that " jis the mould for the top, and i the mould for the bottom f ,so may this be squared, which completes the performance-As to other particulars, due inspection will explain them- ■If any should say, a dome cannot be done so safe without ,a cavity as usual, let them view St. Stephen’s, Walbrook*Stock’s-market, built by that great architect, Sir Christoph® 1 "Wren.”

He then shows the method of covering polygonal building® :

Plate VII. Figure 2. “ Let A be the plan, the upper pa rtof which is half an octagon. It is observable that a circul 81roof, as b, should extend no farther than the upright ofsupport, and there made so as to carry off the water; where 8 ®an ogee roof, as c, may extend to the extremity of the cor' ,nice, without injury to its strength, or offence to the eye °fthe most curious: also, a hollow roof, as D, may extendto the extremity of the cornice.

“ It appears to me, that many angles of a cupola gir® 1beauty; therefore the sweep E (Figure 2) is a regular curv®>the base line l k being taken from the angle of the octag 011in the plan a, as at l k. This curve, e, is divided into 8number of equal parts, in order to trace the common rib,from the said angular rib e : observe, in A, the base ofcommon rib, f l, which is placed in f, as from l to f : c0iy , •tinue the perpendicular, l, at pleasure; take the base lin e, on which are the perpendiculars dropped from the curv®>and observe to place that distance, k l in e, from/ in *> ,any part where it cuts the perpendicular l in f, as atfrom these divisions raise perpendiculars, so by continuing ;the base lines from the divisions in e, to these perpendicu* 8in f, their intersection or meeting is a curve, or s'veefjexactly agreeable, and which, indeed, may serve as a stand 81rule to trace any moulding whatever. .. e

“ To back the said angle-bracket, d, observe to des cr ‘the thickness of it on your plan, as in A at k, which ®b°how much your mould must be shifted, as may appear inThis also may be observed to be a general rule for the backof any bracket.” ^js

These methods are certainly founded on truth, butdiagrams are not laid down in the most obvious way; h® ® .so scattered as not only to be tiresome to the eye, bnoccasion also a long and tedious description. He then Pceeds with the centerings of groins, as follows : re A

Figure 3. “ Let A be the plan of a vault to be cente ^for groins. At a,b,c,d, are piers, generally preparewith the foundation, which bear the weight of the bricky® # :First, resolve on the curve you would have, as dec, ,semi-circle, which is shown by the section B. Begin &t A

dec; centre through as it were a common vault, and ® ^

it; which being done, to make your groin set centres, a® ja to c, and from b to d, divide the curve dee into fourparts, as at g and f; so are g ef small centres, you wifi y ,to nail on the centres first boarded, whose place or Pat h ; these small centres may be put in at pleasure, acc ® e e®

to the bearing of your boards, that is, as to the distance be

each centre. To make your groin straight on its ba fsome little height over the centres, strain a line from

y