42 
rOPULAl! SCIENCE REVIEW. 
spirals is collected by a metal spring wliick presses upon tlie 
axle and conveys tlie current onwards to the depositing solu- 
tion ; and all the opposite ends of wire are connected with an 
apparatus on the axle called a communicator or break, and this 
apparatus collects all the negative electricity of those ends and 
transmits it to another spring which conveys it to the plating vat. 
And thus, by quick rotation of the wheel, a rapid succession of 
electric impulses are generated, which are employed for plating- 
purposes in the same manner as the ordinary voltaic current. 
The above machine is a very convenient source of electricity 
where a cheap motive power is at command, and where the 
quantity of electricity required is not very great. 
The surface of silver deposited from the ordinary cyanide of 
silver and potassium plating solution has a frosted or snow- 
white appearance, which in many cases has to be burnished and 
made bright by mechanical means. This, with articles of highly 
figured design, and also with the interior of certain articles 
that required to be made bright, was a great disadvantage, as the 
process of burnishing is tedious, and with the interiors of vessels 
also very awkward to perform. As with the difficulty in the 
early period of the electro-process in obtaining thick deposits 
of firm silver, a little circumstance was the cause of that diffi- 
culty being overcome, so was it with this obstacle, and it 
happened as follows : — In the process of copying figures for 
electro-typing by a mixture of wax and resin, the surface of the 
wax is covered with a film of phosphorus by means of a solution 
of phosphorus in bisulphide of carbon. It was observed by Mr. 
Mill ward, at Messrs. Elkington’s establishment, that when 
these prepared wax moulds were put into the cyanide of silver- 
plating solution for the purpose of receiving a coating of silver, 
other articles, such as spoons, forks, &c., which -were being- 
plated in the same vat, and especially those nearest to the wax- 
moulds, acquired a coating, more or less perfect, of bright silver, 
which occurred sometimes in patches, and sometimes extended all 
over the articles, instead of the ordinary snow-white deposit. This 
circumstance attracted attention, and induced Mr. Millward to 
try the effect of adding bisulphide of carbon alone to the plating 
liquid. Considerable success soon resulted ; but at this juncture 
the secret escaped, and in consequence thereof a patent was 
taken out, March, 1847, by Mr. Millward and a person of the 
name of Lyons, who had acquired a knowledge of the secret, 
for producing bright deposited silver by means of bisulphide of 
carbon. This process has been constantly employed ever since, 
and is now in extensive use, and with its aid the silver is ren- 
dered very bright and the amount of burnishing required very 
considerably reduced, but it has the disadvantage of making the 
deposited silver much harder. Bright copper had been observed 
