156 ME. G-ASSIOT ON THE STEATIPICATIONS IN ELECTEICAL DISCHAE&ES, 
they terminate abruptly in a dark space, the negative wire becoming intensely red , in 
this state, if the contact-breaker is pressed so as to make the discharge more sudden, 
stratifications extend to the negative wire, which loses its red and assumes a lummous 
white appearance. As the absorption of the carbonic acid continues, the stratifications 
become more distinct and separated, and the dark space often extends, in a tube of 20 
inches in length, to 6 or 8 inches ; they then assume a conical form, showing, when the 
contact-breaker is pressed, an apparent direction of force firom the positive wire, cen- 
tring on the axis of the stratified discharge*; the stratifications are then of the cloud- 
like appearance, precisely the same form as in the best Torricellian vacua. Under some 
conditions the stratifications gradually disappear, the glass tube is fiUed with famt 
luminosity, which, when tested by placing a galvanometer in the circuit, is found to be 
no longer a conductive but a reciprocating discharge. ^Vhen the process was carried 
still further, vacua-tubes were obtained, in which even this luminosity could not be per- 
ceived except with a stronger charge, as by attaching the condenser. In addition to a 
galvanometer, another vacuum-tube (which under the ordinary action of the coil showed 
stratifications) was introduced into the circuit and no light perceived in it ; thus the non- 
transferring condition of a vacuum has been experimentally ascertained f . 
105. Whatever may be the length of the stratified discharge, it ivdl always be found 
to be in the same electrical condition ; from its great length the positive would appeal- 
to be the dominant, as it is equally long whether taken from the outer or inner ter- 
minal. In my previous paper I stated that I was inclined to the opinion that the 
stratifications arose from pulsations or impulses of a force acting on highly attenuated 
matter;” and I am the more confirmed in this opinion, as, if the pulsations or vibrations 
are greatest in bright bands and least in the obscure, this system of interfei ence oi of 
pulsations would also account for the entire absence of stratifications ivhen the air or gas 
is not sufficiently rarefied, as well as when the vacuum becomes nearly perfect, while the 
graduations of narrow to the broad cloud-like stratifications can be thus satisfactoiii) 
explained. 
106. The absence of a dark band and of stratifications when the sides of the negative 
wire are completely protected by glass tubing, is strong eiddence that both must in some 
way be governed by the portion of the negative metallic surface which is exposed ; by 
carefully protecting the negative wire, we not only destroy all trace of stratifications, but 
we obtain evidences of apparently a direet force from the negative terminal. If the 
negative wire is uncovered and placed in a direct line 111111 the positive, the negatiie 
discharge is entirely in a lateral direction, as is denoted by the metallic deposit on the 
* This direction of force in the positive discharge is also noted hy the perforation in the stick of 
potassa (85) . 
f While preparing this communication for the Eoyal Society, I observed that Professor Plucker states 
that, after passing the discharge in a tube containing oxygen for about 1|- hour, “ the dischai’ge tlu'ough 
the tube began to be discontinuous, till at last only single separate discharges oecui’red ; finally, the current 
entirely ceased to traverse the tube.” I have since repeated the experiment in tubes carefully prepared bj 
Dr. ERAXKLAXn, continuing the discharges for several hours, but without obtaining this result. 
