sir CHRISTOPHER WREN, knt.

335

SECT. XII.

A Catalogue, and Account of Defgns of Buildings in the Univer-feties of Oxford, and Cambridge.

Plan and Elevations of the Theatre of Oxford, and Scheme of the Roof

HIS Theatre, a Work of admirable Contrivance and Magnificence, was

j| the first publick Performance of the Surveyor, in Architecture; whichhowever had been executed in a greater and better Style, with a View to theancient Roman Grandeur discernible in the Theatre of Marcellus at Rome ; butthat he was obliged to put a Stop to the bolder Strokes of his Pencil, and con-fine the Expence within the Limits of a private Purse. What (among otherbeautiful and distinguished Parts of this Structure) has been esteemed very ob-servable, is the geometrical Flat-roof; which Dr. P — t has particularly * de-scribed, in his Natural History of Oxfordshire, as follows:

" It was an excellent Device, whoever first contrived it, of making Flat- * Natural Hi-" floors or Roofs of short Pieces of Timber continued to a great Breadth, without Pp »/Oxon.“ either Arch or Pillar to support them, but sustained only by the Side-walls, Jat> ' 1X ‘

“ and their own Texture ; for by this means many times the Defect of long" limber, or Mistakes of Workmen are supply’d, and rectified without any Pre-“ judice to the Building. Of this Sort of Work we have an Example in the" Schools, in the Floor of the uppermost Room of the Tower. —There is also" a Diagram of such Work in the * Architecture of Sebaflian Serlio. But * w, - u de

" Dr. Wallis was the first that demonstrated the Reason of this Work, and Gem. Cap. i.

“ has given divers Forms of it, beside the fore-mentioned, in his Book De" Motu, whence are taken the * Diagrams, Tab. . Fig. i, 2, 3, 4, 5. Upon SeeTab.xni.

“ the two firfl whereof depend the three last ; and all others of the Kind Dr. Plot.

" whatever, whether made up of Quadrats, or oblong Parallelograms, of“ which there are some other Forms in the fore-cited Book De Motu , beside“ that markt Fig. 3. consisting of great and small Quadrats-, or Triangles" alone, as Fig. 4. or mixed with Hexagons, as Fig. 5.”

■ A Model of a gcomctrick Flat-floor, contrived by the fore-mentioned Dr. Dr. Grew’xIgalhs, and given to the Mulæum of the royal Society , is in the Design ob- °fvioiis to the Eye. The Outsides represent the Walls of the Building, on whichthe Flat-floor or Roof is to be laid. The Beams next adjoining to the Sides,have one End lodged on those Walls; the other End sustained by another Beam,lying cross; both Ends of which, are, in like manner, sustained by other crossBeams ; and those again by others ; till they reach the other Walls. So thatno one of them can fall, unless the Walls fail, or the Beams break; all mu-tually sustaining each other, without any Pillar or Prop to support them, besidesdie outer Walls.

“ But of all the Flat-floors having no Pillars to support them, and whose Dr.Plot, date.“ Main-beams are made of divers Pieces of Timber, the most admirable is that“ of the Theatre of Oxford, from Side,wall to Side-wall, 80 Foot over one" Way, and 70 the other ; whose Lockages being so quite different from anycc before-mentioned, and in many other Particulars perhaps not to be paral-“ lcl’d in the World, I have taken care to represent an exact Draught of it."

See Pla s e, Fig. 1. &c. annexed.

“ Wherein aaa and bbb shew the Walls of the Theatre that support this" Frame of Timber, and the Places of the Pilasters of the Rail and Ballifler“ round it; ccc and ddd the Leads and Pipes let down into the Wall for

1 “ Conveyance,