AS OBSEEVED IN TOEEICELLIAN AND OTHEE VACUA. 
159 
I have ali-eady stated that the striee can be obtained by the electrical machine* if a 
Leyden jar is discharged through a vacuum-tube; they may at times be observed, but 
the discharge generally passes in the form of a wave of light of dazzling brightness ; this 
has also been observed by Messrs. Quet and SEGumf ; but if the intensity of the dis- 
charge is reduced by means of a wet string, the strise can be developed in a vacuum- 
tube as clearly and as distinctly as from the induction coil; this led me to suppose 
that when the circuit is interrupted, as in the experiment of Mr. Gkove, the absence of 
striae is due to the heightened intensity of the discharge. 
Having at this time a considerable number of vacuum-tubes at my command, I have 
been enabled to repeat Mr. Gkove’s experiment, and to test the above supposition in a 
variety of ways, and I invariably found that with the best vacuum-tubes which show 
large cloud-like stratifications, I could obtain the result described by Mr. Geove with 
greater certainty ; for instance, in my large cylinder (103) which I exhibited at the 
meetiug of the Eoyal Society on January 13, and with which Mr. Geove subsequently 
repeated his experiment at the Eoyal Institution on January 28, the stratifications are 
destroyed by an interruption of about one-eighth of an inch, although with other tubes 
the distance must not only be considerably increased, but the stratified and non-stratified 
discharges, “notwithstanding all the care used, pass in irregular succession.” Now if 
the disappearance of the stratifications be due, as suggested by Mr. Geove, to the 
cutting off of the feeble cui’rent by the interruption introduced into the circuit, it 
remains to be explained why a space of one-eighth of an inch abolishes the stratifications 
in one tube, while three times that space will fail to do so in another. 
With a vacuum-tube in which the stratifications were entirely destroyed when the 
secondary cu'cuit was interrupted, I found they were always restored when the space 
thus inteiTupted was completed by means of a wet string ; but as this experiment is not 
strictly analogous to the reduced discharge of a Leyden jar, it was varied by making a 
second interruption in the cffcuit and closing this by a wet string ; in this manner the 
discharge passed through the space in air, but being retarded by the string the stratifi- 
cations were again \isible. 
This experiment appears to be fatal to the theory of Mr. Geove ; for the introduction 
of a wet string in a distant portion of the circuit cannot possibly help a feebler current 
to cross the interval opposed to it ; it is quite evident that in this case, as well as in that 
of the Leyden jar, the appearance of the strise depends not upon the conflict of “ secondary 
and tertiary” currents, but simply as to the manner in which the discharge passes. 
I also ascertained that when, by means of an interrupted discharge, the stratifications 
are destroyed, they are reproduced in a carbonic acid vacuum-tube, when heat is applied 
to the caustic potash ; in this experiment the increased resistance arises from the greater 
density of the matter formed in the tube ; if this be correct, the discharge, when passed 
simultaneously through two tubes, in each of which the attenuated matter possesses 
different densities, would produce different effects; if one tube exhibits with the ordi- 
* Philosophical Transactions, 1858, Part I. p. 10. t Comptes Eendns, December 13, 1858. 
