te 9 ae el 
TO THE MOVEMENT OF MACHINES. 521 
degrees amalgamated. By this the action is considerably weakened, 
or ceases altogether; for it is very remarkable that copper, silver, or 
platina, amalgamated on their surface, have scarcely any, or at most an 
extremely weak power of keeping up an electric current with any other 
metal. I have often remarked that the first deviation of the needle was 
very strong, and that at length it returned quickly to its first position 
of equilibrium, without exhibiting any deviation, whilst the voltaic cir- 
cuit, composed of zinc and amalgamated copper, remained always 
closed. It appears to me also remarkable that a wire of copper, pla- 
tina, or iron can be much more easily amalgamated under the influence 
of sulphuric acid by mercury containing other metals than by mercury 
entirely pure. It is desirable that this point should attract the atten- 
tion of scientific men to make similar experiments with more attention. 
Pure zinc has nearly the same qualities as amalgamated zinc or the 
amalgam of zine, viz. of being very little acted upon by sulphuric acid. 
It is only subjected to chemical action when it enters into a voltaic 
combination. I refer, on this subject, to the important memoir of 
M. Aug. de la Rive, inserted in the Bibliotheque Universelle, vol. xliii. 
1830. I have not yet been able to procure any pure zinc to repeat these 
experiments and to employ it in the magnetic apparatus. In zinc foun- 
dries pure zinc may easily be obtained in great quantity by re-distilling 
it until it is purified of the cadmium and other extraneous metals, 
Tts cost would not be much increased, but hitherto there has not been 
sufficient inducement to employ pure zinc to risk the expense of the 
repeated distillation. M. Fengler, manufacturing chemist at Myslowitz 
in Upper Silesia, has constructed the necessary apparatus for preparing 
pure zinc in large quantities; he could supply it for nine ecus the 
quintal, provided a quantity of three quintals were ordered, but unfor- 
tunately his foundry has since been burnt down. His process consists 
in interrupting the distillation when all the cadmium is driven off, in 
then changing the recipient and again interrupting the process as soon 
as he suspects that the other foreign metals are volatilized or mecha- 
nically drawn away. He repeats these operations as frequently as he 
thinks necessary. The zinc thus prepared should not be re-cast in iron 
crucibles. 
: 13. 
The rapid decrease of the voltaic effects in the ordinary voltaic piles 
opposes a great obstacle to the application of electro-magnetism. It 
may be overcome, partly at least, by an assiduous study of these effects. 
The motion of my magnetic apparatus was always very rapid at the 
commencement, but its velocity soon diminished, and ceased entirely 
after a lapse of time which never exceeded an hour. By employing 
amalgamated plates of zinc I have succeeded at three different times 
in making the apparatus work successively during 20, 22, and 24 hours 
without making any change whatever in the pile. The experiments 
