R. V. Gill — Electric Discharge in Geissler Tubes. 417 



the third stratum, and so on. In the case of an induction coil, 

 the whole series is that due to a single spark. The figure in 

 Spottiswoode's paper does not indicate this difference of phase, 

 but it is improbable that he looked for such a result, and, as it 

 might not prove to be sufficiently marked to attract attention 

 when it was not looked for, this is not surprising. Indeed, 

 many reasons might be given to show that there would be a 

 certain overlapping of the different images corresponding to a 

 node. 



Again, several interesting results might be obtained by com- 

 paring the number of intermissions or oscillations as determined 

 by the mirror, with the distance between the strata, since from 

 this theory it would follow that, ceteris paribus, the distance 

 between the strata ought to increase as the frequency of oscilla- 

 tion decreased. However, such experiments might not be con- 

 clusive, as this distance would depend, in perhaps a greater 

 degree, on the intensity of the discharge. We were unfortu- 

 nately unable to compare the period of oscillation as calculated 

 from the formula v = n\, with that directly observed by means 

 of a rapidly rotating mirror. 



There are, of course, many points to be examined, but as the 

 stratified discharge has received but little attention from the 

 point of view proposed in the foregoing pages, it would per- 

 haps be premature to enter into minute details. On a future 

 occasion we hope to describe some confirmatory experiments 

 which it is our intention to undertake. 



Louvain. 



