Royal Society. 223 



horizontal and turns in the same direction as the hands of a watch, 

 the magnetism merely impresses on it a continuous movement 

 of rotation, without making any alteration in its form, its direc- 

 tion, or its appearance. 



Conclusions. 



It follows from the experiments described in this memoir: — 



1. That the action of magnetism, when it is exerted only on 

 a portion of an electric jet transmitted through a rarefied gas, 

 determines in that portion an increase of density. 



2. That the same action, when it is exerted on an electric jet 

 placed equatorially between the poles of an electromagnet, pro- 

 duces in the rarefied gas in which it is propagated an increase of 

 resistance which is as much greater as the gas itself is more 

 conductive. 



3. That this action, on the contrary, determines a diminution 

 of resistance when the jet is directed axially between the two 

 magnetic poles, this diminution being as much greater as the 

 gas is more conductive. 



4. That when the action of the magnetism consists in im- 

 pressing a continuous movement of rotation on the electric jet, 

 it has no influence on the resistance to conduction, if the rota- 

 tion is effected in a plane perpendicular to the axis of the mag- 

 netized soft-iron cylinder which determines the rotation ; while 

 it notably diminishes it if the rotation takes place so that the 

 electric jet describes a cylinder round the axis of the rod. 



5. That these different effects apparently cannot be attributed 

 to variations of density produced in the gaseous medium by the 

 magnetic action, but very probably their explanation will be 

 found in the perturbation induced by that action in the arrange- 

 ment (or disposition of the particles of the rarefied gas) neces- 

 sary for the propagation of electricity. 



XXVII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 155.] 



May 25, 1871.— General Sir Edward Sabine, K.C.B., President, 

 in the Chair. 



THE following communication was read : — 

 " Note on the Spectrum of Uranus and the Spectrum of Comet 

 I., 1871." By Willian Huggins, LL.D., D.C.L., V.P.R.S. 



In the paper "On the Spectra of some of the Fixed Stars"*, 

 presented conjointly by Dr. Miller and myself to the Royal Society 



* Phil. Trans. 1864, p. 413 ; and for Mars, Monthly Notices E. Astr. Soc. 

 vol. xxvii. p. 178. 



