550 Intelligence and Miscellaneous Articles. 



We have operated in the same manner for B,, C p D v and have 

 drawn up the following Table: — 



Coercive Force. Magnetic Capacity. 



.\ v 47 64 



B t 45 66 



O x 42-5 67 



D 1 33-5 68 



E x 13 69 



The magnetic capacity of soft iron of the same form and weight 

 was 71. 



These approximate relations show how important it was to seek 

 out a method of rigorous measurement of magnetic power. — 

 Comptes Rendus de lAcademie des Sciences, Nov. 9, 1876, tome 

 lxxxiii. pp. 857, 858. 



ON SOME REMARKABLE PHENOMENA IN GEISSLER TUBES. BY 

 PROF. E. REITLINGER AND A. VON URBANITZKY. 

 Having, at the commencement of July last, made preparation 

 for continuing our experiments with the aid of a G-eissler mercury 

 air-pump, we filled so-called Wiillner tubes with different gases, 

 and first investigated afresh the conversion of attraction into re- 

 pulsion by a higher degree of rarefaction. The experiments were 

 made with air, nitrogen, oxygen, hydrogen, and carbonic acid. 

 They established that, with all these gases, between 4 and 12 

 millims. pressure the electrical luminous column is attracted, but 

 at about 2-1 millim. it is repelled. Between the two phenomena 

 there is an intermediate stage, in which neither attraction nor re- 

 pulsion is perceptible. For the first occurrence, however, of per- 

 ceptible repulsion it was the less possible to find with the different 

 gases one and the same degree of rarefaction, as the repulsion and 

 attraction proved to be dependent on the intensity of the current, 

 and, for example, a luminous column which showed itself indif- 

 ferent to the finger was caused distinctly to recede from the finger 

 by the insertion of a resistance. Now since the gases in the tube 

 themselves offer different degrees of resistance, we had to take 

 into account at the same time the intensity of the current, in 

 order to render the data comparable. The latter has been found 

 to exert the greatest influence ; yet up to the present time we have 

 ouly numerous results to communicate at the proper time respect- 

 ing that influence, but have ascertained no general law for it : this 

 we shall endeavour to discover. If rarefaction be continued below 

 1 millim., in all the cases which we have observed, layers are pro- 

 duced as the rarefaction proceeds, of little breadth and constant in 

 position so far as our observation extends, which either do not 

 retreat before the finger at all, or only when the induction-current 

 is very much weakened by the insertion of resistances. In con- 

 sequence of this circumstance the repulsion exhibits a certain 

 maximum during the rarefaction, which again diminishes when the 

 rarefaction is carried still further. A portion of the experiments 

 were made with a somewhat wider tube without any capillary part, 

 which thus was in a certain sense intermediate between the Geissler 



