Intelligence and Miscellaneous Articles. 503 



analyses to ^^ in 10,000 volumes of air. It is consequently from 

 10 to 11 times greater than in the air in its normal condition. The 

 diminution of oxygen amounted sometimes to 68*350 in 10,000 vols, 

 of air; instead of 2101-425 oxygen, I found only 2033-075. This 

 decrease is therefore readily detected even by less sensitive methods 

 than the one which 1 employed. 



On the other hand, the air of the plain of Bogota sometimes pre- 

 sents an amount of carbonic acid far greater than the atmosphere 

 of the tierra caliente. This difference may be explained either by 

 the existence of volcanoes, which are situated not far from Bogota, 

 or by the more or less active influence of the solar light. It will be 

 conceived, in fact, that in the tierra caliente, where the temperature 

 is very elevated, the decomposition of the carbonic acid by the 

 green parts of the vegetables must be effected in a far more rapid 

 manner than on the high plain of Bogota, where the temperature is 

 not higher than from 57° to 64° F. 



It is perhaps allowable to suppose, on observing this enormous 

 quantity of carbonic acid appear from time to time in the atmosphere 

 of the New World, and considering the large number of volcanoes 

 which exist in the country, that a portion of the carbonic acid of 

 the air is due to them, and that they thus contribute in part to 

 nourish the vast and beautiful vegetation of the tropics. — Comptes 

 Rendus, Sept. 29, 1851. 



ON THE MAGNETISM OF GASES. BY M. PLUCKER^. 



I introduce the gases to be examined into a thin glass bulb, 45 

 millimetres in diameter, and which can be closed by a cock, also 

 composed of glass. I attach the bulb to one of the arms of a delicate 

 balance capable of indicating -^th of a millegramme with perfect 

 distinctness. The glass of the bulb is slightly magnetic ; its mag- 

 netism is exactly compensated by the magnetic action of the sur- 

 rounding air, so that the action of the magnet upon the bulb, pre- 

 viously exhausted, is absolutely null, whilst the attraction of the 

 bulb when filled with a gas, either compressed or expanded, is exactly 

 that of the same gas. At the ordinary pressure, the weight of the 

 oxygen contained in the bulb is about equal to 57 millegrammes, 

 and the attraction exerted upon this gas by the electro-magnet, 

 when 6 of Grove's elements are used, is equal to 20 millegrammes. 



1. On comparing the specific magnetism of oxygen with that of 

 iron, taken as unity, I found the number 0"003500, which differs 

 considerably from that given by M. E. Becquerel, but agrees tole- 

 rably well with the valuation made by Prof. Faraday. 



2. Oxygen loses its sensible magnetism in almost all those gases 

 with which it enters into chemical combination. Nitric oxide (NO^) 

 forms an exception, which is unique at present ; its magnetism in 

 round numbers is f th of that of oxygen. The protoxide of nitrogen 

 (NO) did not exhibit the least trace of action, i.e. if this action 



* Extract from a letter to M. Arago. 



