I 



Electro-deposited Antimony. 451 



to 82 F. The cooling influence of the water, in this and in 

 several similar experiments^ appeared to prevent the metal un- 

 dergoing its full amount of change. 



40. The peculiar change is attended by alterations in the 

 colour and fracture of the metal ; from a bright steel colour and 

 glassy fracture it passes to a dull gray colour and granular 

 fracturcj as if it progressed a stage towards the crystalline modi- 

 fication : this is particularly manifest in thick pieces gradually 

 heated in the air until the change occurs. It is also attended 

 by a change in the form of the metal : bars which were nearly 

 straight before the action, were considerably curved afterwards ; 

 and the direction of the curvature was such, that the outer side, 

 or that last deposited, invariably became more concave. Upon 

 applying heat to a thin layer of dark antimony, formed upon a 

 thin sheet of silver, it immediately underwent the change, and 

 became exceedingly curved in a similar direction. This direc- 

 tion of curvature appears to be due to a cause already mentioned 

 (see 16, 17), the unequal cohesion of the inner and outer sur- 

 faces of the metal. 



41. By applying heat to the ends of deposits formed upon 

 heliacal copper wires, the action was gradually propagated to 

 the opposite ends at a speed varying from 13 to 30 feet per 

 minute ; and its rapidity of progress appeared to be dependent 

 upon the temperature of the metal and the cooling influence of the 

 enclosed wire, also upon the absence of gray nodules : the warmer 

 the antimony, the greater its thickness ; and the more free it was 

 from gray metal, the more rapid was the action : and in cases 

 where the deposit was thin in places, or had occasional gray 

 nodules, the action was impeded at those parts, and sometimes, 

 totally arrested. Gray nodules invariably impeded the action, 

 and caused it to progress by sudden starts. The progress of the 

 change was rendered more or less visible by the evolution of a 

 cloud of vapour at its advancing point ; also in the case of fine 

 copper wires, by a peculiar snake-like movement in the coils at 

 that part, apparently produced by the cohesive alteration already 

 mentioned (see 16, 17, 40). After the change, the layer of 

 antimony contained numerous transverse and longitudinal fis- 

 sures, as if it had contracted in those directions. 



43. In a number of instances, by connecting the ends of the 

 copper wires with a galvanometer, and inducing the change in 

 the coating l)y a heated wire, a feeble electric current occurred 

 in the enclosed wire whenever, from thinness of the coating, its 

 termination, or other causes, the action ceased, and in every 

 ease passed in a direction opposite to that of the peculiar action. 

 By toucliing the deposit with a heated vvii-e some time afterwards 

 at the point where the action ceased, a cuiTent of ordinary 

 2G2 



