370 O. IN. Rood on the Electric Spark. 
Prof. Rijke, in order to test his the- 
ory, caused the discharge of a large 
induction coil to take place between 
insulated brass points, which were con- 
nected with the poles of the coil b 
two strings wet with distilled water; the diameter of these 
strings was 5™™, their length 4 of a meter. Under these cir- 
cumstances, ali of the electricity developed is subjected to a 
very considerable resistance in passing through the water, and he 
found that in this way, in conformity with his theory, the bright 
ticed hereafter, may throw 
some light on the mode 
in which electricity’ pro- 
gresses over imperfect: 
ly conducting surfaces, 
similar to 19 are still obtained. : 
These experiments explain to a considerable extent the differ- 
ence between the positive figures as obtained by frictional elec- 
tricity and by the coil, showing them in great part to be due 
the presence ef the luminous atmosphere. 
Form of the Negative figure produced by the Luminous Atmosphere. 
When the negative electrode is the brass ball, and its distance 
ys inch from the sensitive plate, the “atmosphere” is blow? 
ke... 
out, producing ee: 
ae 
21, consisting of an external 
heavy black streak, irregular- 9 
ly shaped, and often not over && 
ve d at its ed its 
