102 Proceedings of the British Association. 



vessels made to communicate with each other by platinum, so as to make 

 each extremity of the latter enter into the mercury of either vessel. 

 Things having been arranged in the manner described, the polar wires 

 were each introduced into one of the tumblers, so that the free end of 

 each wire was made to plunge into the mercury. Under these circum- 

 stances, both polar wires appeared to be equally affected — that is, they 

 were precisely in the circumstances as if they had not been connected 

 with any voltaic arrangement. From these facts, Prof. Schonbein 

 infers — 1st, That neither common nor voltaic electricity is capable of 

 changing the chemical bearings of any body, and that the principles of 

 the electro-chemical theory, as laid down by Davy and Berzelius, are 

 fallacious. 2nd, The change which certain metallic bodies, when placed 

 under the influence of a current, seem to undergo with regard to their 

 chemical relations, is due to the production of some substance or other, 

 and its deposition upon those bodies by the agency of a current of 

 electricity. 3rd, The condition, sine qua non, for efficaciously protecting 

 readily-oxidizable metals against the action of free oxygen dissolved in 

 fluids, is, to arrange a closed voltaic circle, which is made up, on one 

 side, of the metal to be protected, and another metallic body more readily 

 oxidizable than the former, and, on the other side, of an electrolyte 

 containing hydrogen, as water. 



Prof. Shepard, of the Medical College, South Carolina, gave an account 

 of the analysis of a Meteorite, in which he had detected chlorine and silicon. 



'On the Composition of Idocrase,' by Mr. T. Richardson. — The com- 

 position of the Silicates has attracted a considerable share of the at- 

 tention of chemists, but until the discovery of the doctrine of Isomor- 

 phism, this department of mineralogy might be said to have remained 

 stationary. It is however remarkable, that, even with the advantages 

 of this beautiful law, many of the formulae of minerals are very incor- 

 rect representations of their constitution, as, for example, in the 

 received formula of Petalite, there is a difference of six per cent, of 

 Silica between the result of the analysis and that computed ; and this is 

 only one among many instances which might be adduced. Idocrase is 

 even in a worse state than this, for Berzelius says, (Die Anwendung 

 Lothrohres, p. 218,) that the formula is not known with certainty, 

 although Prof. Johnstone, in his report on Dimorphous Bodies, has as- 

 signed to it the following formula in common with the Garnet — viz. 



. ... Tai 



Ca Si •+■ \~. Si 

 3 iFe 



The subject has moreover been lately involved in greater obscurity, 

 by the publication of M. Ivanoe's analysis in Poggendorff 's Annalen, 

 which differs from all the analyses hitherto made. With the view then 

 of assisting in explaining these descrepancies, I have made the following • 

 analyses of Idocrase from different localities, with specimens selected 





