250 Prof. Do Ja Rive on the Propagation of Electricity 



stratifications are produced by a RuhmkorflPs apparatus, or by 

 an ordinary electrical machine, or an Armstrong's hydroelectric 

 machine, or even by a battery of high tension, we never get a 

 continuous discbarge, but only a series of separate discharges, 

 which may, it is true, succeed each other so rapidly that their 

 discontinuity is not indicated by a galvanometer; but this dis- 

 continuity nevertheless exists, as Mr. Gassiot showed by means 

 of a Grove's battery of high tension, which, with the same elec- 

 trodes and in the same medium, may give rise at first to stratifi- 

 cations, and afterwards, when the current has become continuous, 

 to -a voltaic arc. 



Moreover the mechanical action of the series of discharges can 

 be directly proved by very distinct oscillations of the mercury 

 column of a manometer placed in communication with the elastic 

 fluid, which accompany the propagation of electricity through 

 this fluid. These oscillations amount to two or three tenths of 

 a millimetre in the case of hydrogen under a pressure of 16 mil- 

 lims. ; they begin to be perceptible as soon as the electricity 

 passes — that is, at a pressure of 36 millims. ; they attain their 

 maximum of three-tenths of a millimetre with a pressure of be- 

 tween 20 and 12 millims., and decrease rapidly when the pres- 

 sure falls from 12 to 5 millims., below which pressure they do 

 not occur. With nitrogen and atmospheric air, the same tube 

 (16 eentims. long and 5 in diameter) being used, the oscillations 

 begin to show themselves as soon as the electricity passes, namely 

 under a pressure of about 20 millims. ; they attain their maxi- 

 mum of four or five tenths of a millimetre between 12 and 3 mil- 

 lims. pressure, and then diminish till the pressure reaches 2 or 

 3 millims., below which they are no longer sensible. 



With the tube of a metre in length, and even with that of 

 half a metre, I was unable to detect any perceptible oscillations 

 accompanying the transmission of electricity, whatever gas was 

 contained in the tubes, and to whatever pressure it was subjected. 

 On the other hand, I obtained very distinct oscillations of one 

 Or two tenths of a millirn. with a jar 20 eentims. in height 

 and 16 in diameter, containing hydrogen at pressures varying 

 from 30 to 15 millims., through which the electric discharge 

 passed between a central knob and a ring 12 eentims. in dia- 

 meter concentric with this knob. This last result shows that 

 the absence of oscillations in the long tubes depends less upon 

 the volume of the gaseous medium, which is not so great in them 

 as in the jar used in the last experiment, than it does upon the 

 effect of the sides of the tubes, which impede the movement of 

 the gas. It proves also that the oscillations really result from a 

 mechanical action, and not from a rise of temperature. As to 

 the intensity of the oscillations, that evidently depends upon the 



