Attraction. 17 



that which holds their parts together. It has 

 been already made evident in the experiment of 

 the two leaden balls, and the same effect will be 

 proved by pressing together the smooth surfaces 

 of two pieces of looking-glass, particularly if a 

 little moisture is dropped between them to ex- 

 clude the air more perfectly. The adhesion or 

 tenacity of all bodies is supposed to depend on 

 the degree of this attraction which exists between 

 their particles ; and the cohesive power of several 

 solid substances has been ascertained by different 

 courses of experiments, in which it was put to 

 the test what weight a piece of each body of a 

 certain diameter would sustain. 



In the following table the numbers denote the 

 pounds avoirdupois, which, at a mean, are just 

 sufficient to tear asunder a rod of each of the 

 bodies, whose base is an inch square. 



Metals. 



Steel, bar 1 35,000 Ibs. Tin, cast 4,440 Ibs. 



Iron, bar 74,500 Bismuth 2,900 



Iron, cast 50,100 Zinc 2,600 



Silver, cast 41,500 Antimony 1,000 



Copper, cast 28,600 Lead, cast 860 

 Gold, cast 22,000 



Woods. 



Locusttree 20,100lbs. Teak, Orange 15,000 Ibs. 



Box 20,000 Alder 13,900 



Jujeb 18,500 Elm 13,200 



Ash 17,000 Mulberry 12,500 



