zyz The Natural Hifiory 



ftruts or braces-, as in Tab. 13. Fig. 6. mult neceffarily bend or 

 break before the window can fink. Nor are the round windows be- 

 low unworthy confideration, being contrived to admit air in foul 

 weather, yet not one drop of rain ; for being opened and fet ob~ 

 liquely,?& in Tab. 1 8. Fig. 7. it receives the rain within at a, and 

 cafts it out again at b ; much lefs will it admit rain any ways when 

 Jhut, itclofing within its/r/3weatthe top, and without it at the 

 bottom. 



148. It was an excellent device, who ever firft contrived it, of 



making flat floors or roofs of fhort pieces of Timber, continued to 



a great bredth without either Arch-work? Pillar tofupportthem, 



being fuftained only by the fide walls and their own texture ; for 



by this means many times the defecl of long timber, or miftakes of 



Workmen, are fupplyed and rectified without any prejudice to the 



Building' Of this fort of work we have an example in the Schools, 



in the floor of the upper moft room of the Tower ', but to be feen 



Only in the room underneath where the Records of the Vniverfity 



lye. There is alfo a diagram of fuch work in the Architecture fee 



forth by Sebaftian Serlj \ for which reafon I think I (hould fcarce 



have mention'd it, but that the Reverend and Learned Dr. John 



Wallit, Savilian Profeiior of Geometry here, was the firft that de- 



monftrated the reafon of this work, and has given divers forms 



of it befide the fore-mentioned, in his Book De Motu, whence I 



have taken the diagrams^ Tab. 13. Fig. 8,9,1 o, 1 1, 1 2 u . to make 



them more publick ; upon the two firs! whereof depend the three 



laft, and all others of the kind what ever, whether made up of 



quadrats or oblongparallelograms, of which there are fome other 



forms in the fore-cited Book De Motu, befide that engraven Fig. 



10. confifting of great and fmall Quadrats ; or Triangles alone, 



as Fig. 11. or mixt with Hexagons, as Fig. 12. to which Book 



I recommend the Reader for further fatisfa&ion concerning them. 



149. But of all the flat floors having no Pillars to fupport it, 



and whofe main beams are made of divers pieces of Timber, the 



moft admirable is that of the Theater in Oxford, from fide wall to 



fide wall 80 foot over one way, and 70 the other, whofe Lockages 



being fo quite different from any before mentioned, and in many 



other particulars perhaps not to be parallel'd in the World, I have 



taken care to reprefent an exaft draught of it, Tab. 14. Fig. 1 . 



t S.'b.Ser/ii ArchiteilLib. i. dtOcom. cap. I. u Walliti Mctbamca five de Motu, Parte 3. devcile 

 cap. 6. frop. 10. 



150. Where- 



