upon different Metals. 7 



pains are taken to keep the face of the hammer parallel to the 

 surface of the anvil ; and that it can only be counteracted, when 

 required, by directing a blow from time to time upon the acute 

 angle. To determine, if possible, whether any connexion sub- 

 sists between these results of the direct application of mecha- 

 nical force to the metals, and the structure of the bars of tin 

 developed by the action of mercury, as just described, I insti- 

 tuted the following experiments. 



EXPERIMENT VIII. 



A bar of tin, of about the same dimensions as the last, which 

 had assumed the rhomboidal form during the process of ham- 

 mering, from the original cylindrical shape in which it had 

 been cast, was treated with mercury in the manner described 

 above : it was resolved, as before, into four rectangular trihe- 

 dral prisms, but with two unequal angles, corresponding to 

 the bisected angles of the rhomboid. 



EXPERIMENT IX. 



The tin bars upon which the previous experiments were made 

 had been shaped by the hammer, and I was desirous of ascer- 

 taining whether the forces which had been applied had in any 

 way disposed their particles to assume the structure which had 

 thus been developed. For this purpose, a bar was cast, in a 

 mould, of nearly the dimensions of that employed in Exp. vii. 

 and was treated with mercury in the same manner. The four 

 trihedral prisms, with their two pyramids, were formed as 

 before ; but the clefts and the planes of junction were not as 

 neat as in the foregoing instances. This seemed to be owing 

 to the angles of the original bar not having been so sharp as 

 when formed by the hammer, but having necessarily come 

 rounder from the mould, and presenting a surface to the action 

 of the mercury. 



EXPERIMENT X. 



A cast cylinder of. tin, five inches long, and a. quarter of an 

 inch in diameter, was substituted for the square bar in the 



