322 Intelligence and Miscellaneous Articles. 



tities of sulphuric acid and of oxide of copper are proportionally 

 the same ; we may thus consider the new mineral a mixture of 

 Langite (4CuO, S0 6 + 4H0) with a very basic silicate of alumina 

 analogous to Scarbroi'te or to Schrotterite (varieties of allophane), or 

 with a hydrate of alumina mixed with a silicate of the genus allo- 

 phane or Halloysite. Woodwardite is to be considered an analo- 

 gous mixture, in which there is a hydrate of alumina with a little 

 silica in the place of a very basic allophane. 



The Langite found in Cornwall as killas must then, under certain 

 circumstances, have been deposited along with a hydrate of alumina 

 or a very basic silicate to form those mixtures of a variable colour 

 which constitute Woodwardite and the mineral which resembles it. 



It must be concluded from these facts that Woodwardite can in 

 no way constitute a new species ; and just as we frequently see in 

 various localities allophanes coloured by more or less oxide of cop- 

 per, there are also in Cornwall allophanes or hydrates of alumina 

 mixed with Langite, as is the case with the two minerals I have exa- 

 mined. Moreover, the quantity of silica in the allophanes being very 

 variable (10 to 24 per cent.), nothing militates against the supposi- 

 tion that the varieties poor in silica contain a mixture of hydrate of 

 alumina, which predominates in Woodwardite, the allophane of which 

 would have a minimum of silica, — completing thus the analogy of 

 the two minerals which form the subject of this note. — Comptes 

 Rendus, December 30, 1867. 



DIALYSIS OF INDUTION CURRENTS. NOTE BY M. BOUCHOTTE. 



"We have already* called attention to the remarkable fact that the 

 introduction of a voltameter, containing acidulated water, into the 

 circuit of a magneto-electrical machine gives rise to very marked 

 phenomena of polarization ; that to obtain this result it is suffi- 

 cient to use as electrodes platinum wire sufficiently fine; that 

 one electrode, being immersed to a depth of from 7 to 8 millimetres 

 in the liquid, the other being completely submerged, becomes sur- 

 rounded by a luminous sheath, and acquires positive electricity. 



To regulate more easily the contact of the platinum wire and 

 the liquid, the electrode may be introduced into a glass tube, in 

 which it is made to slide, the metal ou !;side the tube being alone 

 exposed to the electric action. By this arrangement, all the parts 

 of the voltameter may be tested ; and it can be shown that the effects 

 of the polarization of the current are independent of the position 

 of the electrodes. 



Continuing these researches, the following results have been 

 obtained : — 



1. When a second gas- voltameter is brought into the circuit, it 

 yields hydrogen and oxygen gases in the proportion of 2 to 1, — 



* Phil. Mag. Feb. 1868. 



