OF FOREST-TREES. 



243 



weight ; as v.g. why a piece of wood an hundred pounds weight, poising cHAP. IV, 

 more in the air than two pounds of lead, the two pounds of lead should ^-^''v-**^ 

 seem to weigh (he should say sink) more in the water*? why fruits, »ofthespe. 

 being cut off from the tree, weigh heavier than when they were growing ? 



of timber in 



with several the like paradoxes, haply more curious than useful, and ^^"erf'^e the 

 therefore we purposely omit them ; but so may we not the recommen- ptjfosophicar 

 dation of that useful Treatise of Duplicate Proportion, together with a n,'"''"i69''°"and 

 new Hypothesis of Elastic or Springy Bodies, to shew the strengths of 

 timbers, and other homogeneous materials applied to buildings, machines, 

 &iC. as it is published by that admirable genius, the learned Sir William 

 Petty : to which we join that part of Dr. Grew's Comparative Anatomy 

 of Trunks, as variously fitted for mechanical uses ; where that most in- 

 dustrious and curious searcher into nature, describes to use whence 

 woods are soft, fast, hard, apt to be cleft, tough, durable, &c. 



Lastly. Concerning squared and principal timber, for any usual build- 

 ings, these are the legal proportions, and which builders ought not to 

 vary from. 



/' F. F. -v. T„ /In. In.>^ ^ Feet 



e \ 14 16 i ^engm, i 8 j"- i lU in length 



Summers 1 ,q . c,r^r "^"^t be y -.c, o nf ° \ ?i 

 or ffirders<f in their J^^^ 9\^} ™"st be 



orgiraers<2Q v m meir < lOf.^S n their 



^'""^ / 23 26\ - / 16 12 U / m square 



V.26 28^ V 17 14 V 



Binding C ■) In length fg ^"^ Wall- plates and beams fin. 



joists andjF. F, (must be ^ f of any length, from 1 5 j 7 j 



trimmers 7 to 1 1 H i"^ their "S g t feet, may have in their "j 1 0 & 6 



from (_ 3 square ... ) square 8 6 



Purlines/ f " , f,' ) f " ^^"g^^' f \ 

 n < 15 to ]8| Vhave m their & > 



(l8^ 21^1 square (l2— sj 



X F. F. -s ^ In. In.-^ /" N Single 



PrincinalV^^ 14J / In length, ^ 8 5 ) ^6jrafters 



"™P^Ml4i 181 (must have 



rafters ^ '■^^ ±0^ V '"^"^^ y ' V the l'\ 

 rarieis < igi to2U (in their ^]0to8 ' , < 8 Uength 

 cut taper J g^^, reon^2 9^ rJsifrom 



from... (2^1 ggpoJeside Cg 9 I to , 



■o • ' ITT, i'Feet 1 must have ("Inch, 



Prmcpal dischargers » I ^^^^.^ J 



or any length irom ... » ,1 I -.n 



^ " (upward ) square ... ( 16— 



But carpenters also work by square, which is ten feet in framing and 

 erecting the carcase, as they call it, of any timber edifice, which is valued 



