Intelligence and Miscellaneous Articles. 553 



exist as sulphide by treating the substance with sulphide of ammo- 

 nium, which dissolved out sulphide of nickel. The stone contains 

 55 '60 per cent, of silicates ; and taking into account the water deter- 

 mined by Cloez, the oxygen ratio of the silicate is that of serpentine. 

 If the alumina is due to anorthite, it will give 242 per cent, of this 

 felspar contained in the meteorite. Subsequent observations by 

 Des Cloizeaux, Pisani, Daubree, and Cloez prove that this remark- 

 able meteorite contains minute rhombohedral crystals of a double 

 carbonate of magnesia and iron, and Cloez obtained a little more 

 than a half per cent, of carbonic acid from a portion of the meteorite 

 operated upon.^-Silliman's American Journal for March 1865. 



NOTE ON THE PROPAGATION OF ELECTRICITY THROUGH METALLIC 

 VAPOURS PRODUCED BY THE VOLTAIC ARC. BY A. DE LA RIVE. 



In following out my investigations upon the propagation of elec- 

 tricity in greatly rarefied elastic fluids, I have been led to study this 

 propagation in the vapours of various metals. 



The apparatus that I make use of for this purpose consists of a 

 large glass balloon, furnished with four tubulures and supported 

 on a foot. The two tubulures at the extremities of the horizontal 

 diameter are furnished with leather plugs traversed by metal rods, 

 to which are fitted the metallic or charcoal points, which serve to 

 produce voltaic arcs by means of a Bunsen's battery of 60 to 80 

 pairs. The two tubulures situated at the extremities of the ver- 

 tical diameter serve for the passage of two brass rods, terminated by 

 metal balls, between which passes at the same time the electric jet of 

 a Ruhmkorff's apparatus. The balloon, after a vacuum has been 

 produced in it, is filled with thoroughly dried nitrogen, which is 

 rarefied to a pressure of from 2 to 3 millims. ; then the electric jet is 

 passed through, its intensity being measured by means of the pro- 

 cess of derivation described by me in a previous communication. 



After the constancy of this intensity has been ascertained, the 

 horizontal metallic points are brought near to each other, so as to 

 produce the voltaic arc, which acts here solely as a source of heat. 

 Care must be taken to maintain this arc for some minutes ; then at 

 a certain moment the intensity of the electric jet is seen to be con- 

 siderably increased ; at the same moment the colour of this jet, 

 which was of a deep rose in the nitrogen, acquires quite a different 

 tint, which varies according to the nature of the conducting points 

 between which the voltaic arc passes. This new appearance lasts 

 for some moments after the cessation of the arc ; and it is even at 

 this period that it is most remarkable, as it no longer has to suffer 

 by contrast with the dazzling light of the arc. 



The voltaic arc was successively produced between points of silver , 

 copper, aluminium, zinc, cadmium, and magnesium, and between two 

 points of gas-coke, all these materials being capable of acquiring a 

 gaseous state in consequence of the high temperature which is pro- 

 duced. With points of silver and zinc the electric jet exhibits a 

 very distinct blue colour, darker with zinc than with silver. With 

 points of copper the tint is a very dark green ; with cadmium applet 



Phil. Mag. S. 4. No. 199. Suppl. Vol. 29. 2 



