aS a eae ee Se eee 
* 
Electricity. 118 
It is known that according to MM. Dumas and Prévost, urea shows 
itself in the blood of animals after the removal of the kidneys, and that 
they conclude from the fact that the kidneys remove the urea, while not 
producing it. 
Picard has completed the demonstratation. He has compared, as 
is closed. The chemical theory has definitely triumphed. As explained 
e reviews and explains all the alleged facts in favor of the theory of 
contact. He thus sp 
displace by iron the copper of the sulphate of copper it is necessary to put 
task of giving a theory of the pile. His studies as wéll as his 
lead him in this direction. : . 
De la Rive was the first who recognized the ——. fact that zine 
chemically pure is not attacked by hydrated sulphuric acid ; that two 
metals on which pure nitric acid, for example, has no action, such as gold 
‘the contrary, they produce an instantaneous current when a drop of chlo- 
ee orog acid is added. The theory of contact has never yet explained 
is fact, 0 
The third volume of his work is reserved for the applications of elec- 
icity. The important part which De la Rive took in the invention of 
_ SECOND SERIES, VoL, XXIII, NO. 67.—JAN., 1857. 
15 
