NICKEL-PLATING. 



135 



The mercury used in nickel-plating exerts but a small 

 influence on zinc when the latter is thick ; but in the contrary 

 case its action is very marked ; this is the reason why the nickel- 

 plating of zinc is a very delicate operation. It is only by actual 

 experiments that the operator can find out the length of time 

 required for the immersion of the zinc in the mercurial solution. 

 The nickel deposited on amalgamated zinc is more resisting 

 and more beautiful than that deposited on coppered zinc. M. 

 Meidinger has observed that the various kinds of German 

 silver were with difficulty coated with nickel, and that a better 

 result is obtained by previously amalgamating them. 



Polishing Lathe. 



Works of Messrs. Neumann, Schwartz, and Weil, at Freiburg. 

 We illustrate, Fig. 24, one of the most complete nickel- 

 plating works that we know of, and will give a brief description 

 of them. 



