fame Experiments 'made with an Air-pump. 645 
experiment lviii* 
-Electrical appearances exhibited. 
Light began firft to appear in dallies, — — • 
Light appeared the whole length of the tube in ftriae. 
Tube was filled with an uniform body of pale light. 
The pump had now been worked five minutes. 
The pump was then worked five minutes more. 
The tube was ftill filled with a uniform body of pale 
light, — — — — 
'Degrees of exhaus- 
tion according to 
Barom. 
Pear- 
gage. 
gage. 
5 
8 
74 
3 S 
269 
230 
The conductor being then removed to a diftance from 
the tube, it was made to approach it by degrees till a 
fpark ftruck it, which was at the diftance of two inches ; 
the light in the tube now appeared like a compact body 
of fire, of a vivid purple colour, tending to a red. 
Objects were feen through the tube when filled with 
this body of the electrical light, no lefs diftinCtly than 
if there had been no fuch light in the tube^. 
The vitriolic acid being taken out of the receiver, I 
put a piece of leather of 100 grains, as it came from the 
leather-fellers, into that end of the tube which was next 
to the conductor of the eleCtrical machine, and fartheft 
from the receiver of the air-pump. I put the leather in 
(a) This circumftance has been before remarked by Dr. HAMJLTON-in his 
conje£tures on the tails of comets. 
a 
