RESEARCHES ON THE PHENOMENA 



WHICH CHARACTERIZE AND ACCOMPANY 



THE PROPAGATION OF ELECTRICITY 



IN HIGHLY EAKEFIED ELASTIC FLUIDS.* 



BY PROFESSOR A. DB LA RIVE. 



Translated for the Smithsonian Institution from the Mcmuires de la Societe dc Physique el 

 d' Historic Naturdle de Geneve, tome XVII, 1863. 



I was led in 1849, in my first memoir on the aurora borcalis,f to show that 

 the electric light which is produced in a vacuum of from four to five millimetres 

 is obedient to the action of the magnet. I subsequently found that this experi- 

 ment, in which, to produce electricity, I at first used an ordinary electric instru- 

 ment, and then the hydro-electric machine of Armstrong, succeeded still better 

 with Ruhmkorif's induction apparatus. The employment of this apparatus 

 has since supplied the means of studying in a surer and more commodious 

 manner the propagation of electricity in rarefied gases, and thus the assurance 

 has been obtained that, while an absolute vacuum will by no means transmit 

 electricity, the presence in any space of the smallest quantity of ponderable 

 matter in the state of an elastic fluid suffices for such propagation. To the con- 

 clusive experiments of M. Gassiot we essentially owe the demonstration of this 

 important principle. It has been observed that the transmission of electricity 

 through elastic fluids is effected with more or less facility, according to the na- 

 ture and density of the fluid, and that it is accompanied, when the gas is very 

 much rarefied, by an appearance which has been called the stratification of 

 electric light, consisting in the phenomenon of a succession of strata alternately 

 luminous and obscure, presented by the luminous electric discharge. The 

 action of the magnet on this light has likewise been studied. M. Plucker, after 

 numerous and important experiments, has ascertained its law in connecting it 

 with the formation of magnetic curves. Lastly, different explanations have 

 been offered of the stratification of electric light, some based on the peculiar 

 mode of the production of electricity by Ruhmkorff's apparatus, others referring 

 it, not to the character of the apparatus producing the electricity, but rather to 

 that of the medium which propagates it. 



The phenomena just cited had awakened in me a lively interest, and I have 

 for some years more particularly studied them. I have encountered great diffi- 

 culties in this pursuit, as, on account of the necessity, in operating on highly 

 rarefied elastic fluids, of having apparatus which Avill properly maintain a vacuum, 

 as well as very delicate instruments to appreciate with minute exactness the 

 degree of rai-efacation. The establishment at Greneva, conducted by so skilful 

 a machinist as M. Schwerd, has, however, enabled me in a great measure to 



* For a table of French measures, compared with English, see the last page of this Report. 

 t Annates dc Cliimie ct dc Physique, tome XXV, p. 31U; and Comptcs Rcndus del Academie 

 des Sciences, tome XXIX, p. 412. 



