144 aiE. GASSIOT ON THE STEATIEICATIONS IN ELECTEICAX DISCHARGES, 
distinct series of stratifications, one from each terminal, separated in the centre of the 
tube by a dark band of about inch. In this state the tube rras sealed, and remained 
for several days, during which time I repeatedly obtained the same double set of strati- 
fications. Unfortunately, on one occasion I continued the discharges too long : one of 
the wires became heated and the tube fractured. 
Injhence of Temperature. 
76. If the heat from the flame of a spirit-lamp is applied along one side of a Torricel- 
lian vacuum-tube in which the stratifications are naiTow and close, that side of the tube 
aids the transmission of the discharge which now leaves the cooler for the heated side, 
the stratifications becoming clearer and wider apart. If a section of the tube is equally 
heated, that section will exhibit the stratifications much wider apai't than the portion 
which has not been heated, where they appear to collapse ; as the tube returns to its 
normal state of temperature, the stratifications throughout resume their original figure. 
If heat is applied to a section of a tube which exhibits the cloud-like stratifications, they 
lose their clear distinctness, becoming confused and intermingled ; in this state the black 
from the negative wire appears to be more freely deposited; and when the flame of a 
spirit-lamp surrounds the negative wire, distinct discharges can be heard inside the tube 
near the negative, but none from the positive. 
77. Through the kindness of Dr. Faeaday, to whom I am much indebted for sug- 
gestions, advice, and personal assistance in the progress of these researches, I had the 
opportunity of making the following experiments in the laboratory of the Koyal Institu- 
Eig. I. 
tion : — 
Fig. 4 represents an air Torricellian vacuum, the 
tube being bent in the form of the figure, 10 inches 
in length, and about I inch internal diameter. This 
tube was placed in a mixture of ice and salt, without 
altering the form of the stratifications, which were 
of the cloud-like character. It was then placed in 
a bath of ether, which, by solid carbonic acid, was 
gradually cooled to about -100»; all trace of the stratifications disappeared, the tube 
being filled with a luminous discharge, the negative wire no longer exhibiting the re 
<r 
f 
a-S 
c, 
glow. 
78. Fig. 5 represents a tube of the same dimen- Eig. 5. 
sions, with sufficient mercury to cover both wes. 
In this tube the stratifications are narrow, but very 
clear and distinct ; the centre of the tube was placed 
in the ether bath, leaving the ends and both wires 
exposed, the mercury remaining in the bend of the ^ 
tube. The mercury soon froze, and the stratifications underwent considerable alterations. 
particularly near the positive terminal, where they were much mder apart ; over the sur ace 
