upon different Metals. 3 



examination, a large cluster of crystals, similar to the preceding, 

 was found adhering to its upper part, and others floating 

 upon the liquid. They were not quite so large as the first; 

 but bore very distinctly the form of six-sided plates. The 

 whole mass was thoroughly saturated with mercury, but had 

 been more acted upon at the bottom than the top of the portion 

 immersed. At the lower end, the prisms had the appearance 

 of being more detached from one another than in their original 

 state, from cracks which had taken place in the metal ; and 

 which conferred upon their extremities the semblance of imper- 

 fect pyramids. Several deep clefts also had been formed along 

 the more prominent edges of the mass. 



EXPERIMENT III. 



A small bar of lead was plunged, for about half its length, 

 into some mercury contained in a test-tube. Having been left 

 undisturbed for ten days, it was carefully lifted out and exa- 

 mined. A bundle of very delicate, silver- white, feathery crystals 

 was found loosely adhering to it, on a line with the surface of 

 the fluid. Their form could not be accurately determined, but 

 they resembled a heap of frosty particles swept together on a 

 pane of glass ; and their minute prisms appeared to be attached 

 together at angles of sixty degrees. The bar had been most 

 acted upon at its lowest extremity : it was thoroughly impreg- 

 nated with mercury throughout its substance, but had not 

 totally lost its ductility. After the operation, the tin crumbled 

 to pieces under a slight blow of the hammer, but the lead could 

 be flattened into a plate. 



EXPERIMENT IV. 



A bar of zinc was treated in the same way, and for a like period. 

 It was found, upon examination, studded throughout the whole 

 length which had been immersed with very bold crystals, of 

 the form of hexahedral plates, which increased in quantity and 

 size from below upwards. The bar tapered downwards to a 

 point, and was more unequally acted upon than the former 

 metals, its surface being rough, and corroded into cavities. 

 Some of the crystals adhered very strongly to the surface, and 



B 2 



