320 Intelligence and Miscellaneous Articles. 



construct and frequently verify the Table of the ratios of the forces 

 to the galvanometric deflections. 



M. Morren has succeeded thus in arranging a comparative Table 

 of the electrical conductivity of some gases, which contains for 

 each gas the pressure, the deflection of the galvanometer, and the 

 force of the current corresponding to this deflection. Up to 36° of 

 deflection the forces arc represented by the same numbers as the de- 

 flections ; but from 36° they increase far more rapidly than the 

 deflections. 



Thus, for a deflection of 66° # 2 (the maximum deflection obtained 

 with hydrogen under a pressure of 2 millims.), the corresponding 

 force is 174, and so on. 



One of the most singular characters which rarefied gases present 

 is the black non-luminous band found near the negative electrode. 

 Its length frequently varies under circumstances which apparently 

 are quite identical ; yet the author was able to determine the follow- 

 ing lengths in various gases at pressures between 1 millim. and 0'5 

 millim : — millims. 



Hydrogen 40 



Nitrogen 35 



Oxygen G4 



Carbonic acid 19 



Carbonic oxide 42 



The colour of the jet varies with the nature of the glass of the tube 

 in which the gas is enclosed, which exercises great influence on the 

 colour which the different gases present. The aureole which sur- 

 rounds the negative electrode varies least, and furnished a ready 

 means of ascertaining the greater or less stability of some gases, par- 

 ticularly of the compound gases. 



One fact noted by M. Morren, which appears curious enough, is 

 that oxygen, when pure, and the vapour of mercury give no stratifi- 

 cations. 



It follows from the numbers in the Tables given by M. Morren, 

 that conductivity commences for each gas at very different moments 

 as regards pressure. Thus the current begins to pass, approximately, 



In hydrogen at GO millims. pressure. 



In carbonic acid ,,39 „ 



In air „ 29 



In nitrogen and in oxygen. . ,, 23 ,, 



It is seen from the same Table, that for each gas there is a certain 



pressure at which the electric conductivity is at its maximum. Thus 



this maximum is — millims. 



For hydrogen .... 174, and takes place under a pressure of 2*0* 



For oxygen . 174 ,, „ ,, 0'7 



For atmospheric air 172 ,, ,, ,, 0*7 



For carbonic acid. . 168 ,, ,, ,, 0*8 



For nitrogen 102 ,, ,, ,, 1*0 



* From 2 to 1 millims. of pressure the intensity scarcely changes, since 

 under a pressure of 1 millim. it is still 173. 



