MECHANICS AND USEFUL AKTS. 79 



USE OF ZINC FOR COINAGE. 



The French Government having recently proposed to lower the standard 

 of its silver coinage, cm account of the increasing scarcity of silver, and 

 the continued disappearance of the old silver coinage from circulation, 

 authorize;! M. Peligot, chemist to the mint, to make experiments to 

 ascertain how far the introduction of some zinc, or the complete substi- 

 tution of zinc for copper as an alloy in the coins in question, would affect 

 their appearance and durability. M. Peligot has in accordance with his 

 instructions, therefore, recently reported to the French Academy, that 

 his experiments undoubtedly show that alloys of silver and zinc possess 

 considerable physical advantages over the corresponding alloys of silver 

 and copper, while they are of course sensibly cheaper, since the market 

 price of capper is more than four times that of zinc. 



An alloy of silver and zinc, in the proportions of 165 zinc to 835 silver 

 he found to be appreciably whiter than the corresponding alloy of copper 

 and silver, while it is also " remarkably m il leable " and " perfectly 

 homogeneous when rolled." He experimented also on alloys of silver 

 and zinc in atomic proportions, and found that both an alloy of one 

 equivalent (or 108 parts by weight) of silver with one equivalent (or 32 

 parts by weight) of zinc, and an alloy of two equivalents (or 216 parts) 

 of silver with one equivalent (32 puts) of zinc, are readily malleable, 

 while alloys containing either iwo equivalents of zinc to one of silver, or 

 three equivalents of zsnc to two of silver are too brittle to be rolled. 

 All the alloys of silver and zinc upon which he experimented are more 

 fusible, more sonorous, and more elastic than alloys, in the same propor- 

 tions, of silver and copper ; and when those of them which are malleable 

 have had their malleability impaired by hammering, it can be readily 

 restored by simple heating. Moreover, the zinc alloys have over the 

 copper alloy the very great advantage of no verdigris being formed by 

 the contact with them of acid liquors and the equally great advantage of 

 not being nearly so readily discolored by sulphuretted hydrogen, or other 

 sulphur-compounds. M. Peligot, indeed, states that an alloy of 800 

 parts silver with 200 parts zine will preserve its whiteness unimpaired in 

 a solution of a poly sulphide in which the standard alloy of silver and 

 copper would soon become quite black. 



Zinc would thus certainly seem to be better adapted than copper to 

 alloy silver with, for coinage ; while some of the alloys of silver and zinc 

 above mentioned especially that of 800 parts silver with 200 parts 

 zinc should be worth the attention of silversmiths, and other producers 

 of ornamental metal work. 



IMPROVEMENTS IN ENGRAVING. 



In the process of engraving- metallic plates by etching with acids 

 there has been one obstacle to perfect work which we have regarded 

 as insurmountable. As heretofore practiced, this process consisted 

 in covering the plate with a thin coating of wax ; which was attended 

 with difficulties almost insurmountable. But these difficulties have 

 been completely overcome by a French invention which is one of 

 the most beautiful that has ever been made in this delicate art. 

 The inventor is Monsieur E. Vial, of Paris, and the following is 

 a description of his process : A drawing is made with a greasy 



