240 



A DISCOURSE 



March 23, 1663. 

 The experiment of breaking several sorts of wood was begun to be 

 made : and there were taken three pieces of several kinds, of Fir, Oak, 

 and Ash, each an inch thick, and two feet long ; the Fir weighed 815 

 ounces, and was broken with two hundred pounds weight ; the Oak 

 weighed 121 ounces, broken with two hundi-ed and fifty pounds weight ; 

 the Ash weighed 10^ ounces, broken with three hundred and twenty- 

 five pounds weight. 



Besides, there were taken three pieces of the same sort of wood, each 

 of half an inch thick, and one foot long ; the Fir weighed 1 ounce, and 

 was broken with five-eights of an hundred ; the Oak weighed If ounce, 

 broken with five-eights of an hundred ; the Ash weighed If ounce, 

 broken with one hundred pounds. 



Again ; there was a piece of Fir half an inch square, and two feet long, 

 broken with thirty-three pounds ; a piece of half an inch thick, one inch 

 broad, and seven feet long, broken with one hundred weight edge- 

 wise ; and a piece of half an inch thick, and one and a half broad, and 

 two feet long, broken with one hundred and twenty-five pounds weight, 

 also edge-wise. 



" also when wood is cross-grained, as it often happens in sawing, this will weaken it more 

 ^ or less, according as it is more or less cross the grain ; and I have found, by experience, 



" that tough wood, cross the grain, such as Elm or Ash, is from seven to ten times weaker 

 " than straight ; and wood that easily splits, such as Fir, is from sixteen to twenty times 

 " weaker : and for common use, it is hardly possible to find wood but it will be subject to 

 " some of these things : besides, when timber lies long in a building, it is apt to decay, or 

 " be worm-eaten, which must needs very much impair its strength. From all which it ap- 

 " pears, that a large allowance ought to be made for the strength of wood, when applied to 

 " any use, especially where it is to continue for a long time." 



The following proportions of the strength of several sorts of wood are taken from 



Mr. Emmerson's tables : 



Box, Yew, Plum-tree, and Oak 11 



Elm and Ash 8^ 



Walnut and Thorn 7g 



Red Fir, Hollen, Elder, Plane, Crab, and Apple-tree 7 



Beech, Cherry-tree, and Hazel 6i 



Alder, Aspen, Birch, White Fir, Willow or Saugh 6 



I 



