electrical phenomena exhibited in vacuo. 6g 
requiring almost absolute darkness to be perceived ; and it 
was not perceptibly increased by heat. 
I made two experiments on electrical and magnetic repul- 
sions and attractions in the mercurial vacuum, by attaching 
to the platinum wire two fine wires in one case of platinum, 
in the other of steel, terminated by minute spherules of the 
same metals : I found that they repelled each other when the 
wire was electrified in the most perfect mercurial vacuum, as 
they would have done in usual cases ; and the steel globules 
were as obedient to the magnet as in the air ; which last result 
it was easy to anticipate. 
In some of the first of these experiments, I used a wire 
for connecting the metal with the stop-cock ; but latterly, the 
rarefied air or gas was the only chain of communication ; and 
this circumstance enabled me to ascertain that the feeble- 
ness of the light in the more perfect vacuum was not owing 
merely to a smaller quantity of electricity passing through 
it, for the same discharge which produced a faint green light 
in the upper part of the tube, produced a bright purple light 
in the lower part, and a strong spark in the atmosphere. 
The boiling point of pure olive oil is not much below that 
of mercury ; and the butter or chloride of antimony (anti- 
monane) boils at about 388° Fahrenheit. I tried both these 
substances in the vacuum, and found, as might be expected, 
that the light produced by the electricity passing through the 
vapour of the chloride was much more brilliant than that 
produced by it in passing through the vapour of the oil ; and 
in the last it was more brilliant than in the vapour of mer- 
cury at common temperatures : the lights were of different 
colours, being of a pure white in the vapour of the chloride. 
