Intelligence and Miscellaneous Articles. 143 



ON THE THEORY OF THE DISSOCIATION OF GASES. 

 BY G. JAGER. 



The author starts from the fundamental idea that the beginning 

 of the dissociation of a molecule is bound up with a certain 

 temperature-limit, and in conformity with this a certain limit of its 

 kinetic energy. The stationary condition occurs when as many 

 molecules are dissociated as recombine. 



The number of the non-dissociated molecules which possess a 

 velocity between w and do) is given by Maxwell's law in the form 

 of a differential expression. If it be assumed that the velocity of 

 dissociation of a molecule is proportional to its progressive velocity 

 w, the integral of the above expression extended from the lower 

 limit of velocity at which dissociation begins to w=oo is a measure 

 of the number of molecules which split up in unit time. 



According to Maxwell's law of distribution, the number of 

 impacts may be calculated which a partial molecule experiences in 

 unit time so that the velocity remains below a certain limit ; and 

 likewise the probability that the velocity of the colliding mole- 

 cules also does not exceed the same value. In this way an ex- 

 pression is obtained for the number of molecules which combine 

 in unit time. 



By calculations which cannot here be reproduced the author 

 arrives at the following expression for the dependence of the 

 density d of a gas on the temperature : 



d = < 



1 + 



V1+. 



In this c=a l e^^ 1+at) /(l + a*) 3 , in which a x and <p are two constants, 



and a= ^, d Q is the greatest possible density of the gas at which 



there are no dissociated molecules. 



The formula gives for hyponitric acid results which agree well. 

 For the temperature at which a molecule is dissociated t is found 

 >6000°, an unexpectedly high number, which is in disaccord 

 with the ordinary views. — Beibl'dtter derPhysik, No. 5, 1892 ; from 

 Wiener Berichte, November 12, 1891. 



AURORAS OBSERVED AT GODTHAAB. BY ADAM W. PAULSON. 



The author publishes the journal of the observations of all the 

 auroras which appeared at Godthaab (South Greenland) during the 

 winter of 1882 to 1883, and develops the general considerations 

 to which they lead. 



Aurora? boreales are divided into two distinct categories. When 

 the phenomenon is feeble they simply appear as luminosities or 

 luminous clouds. The more marked aurora? boreales affect the arc 

 shape. These arcs may present various shapes known as curtains, 

 bands, zones, and corona?. The two latter, no doubt, do not differ 



