34 Professor Leslie on Electrical Theories. 
We may observe, that, if the intensity of A’s electricity con- 
tinue the same, and the air flow uninterrupted, the distance to 
which the bright cone extends, will be determined by the num- 
ber of luminous particles in contact with the point A. For since 
the divergency is unaltered, the brightness of CD will be propor- 
tioned to the quantity of lucid matter spread through it. Hence* 
the pencil is contracted by making the point flner ; and, in many 
cases., it cannot, on a small needle, be distinguished from the 
star. 
The pencil at A will not be sensibly affected, by altering the 
shape and magnitude of the body B, or even by removing it en- 
tirely ; for, at that distance, the action of B is quite inconside- 
rable. If the pointed metallic body has the same electricity 
with the cushion, and no conducting substance be near it, the 
appearance of the star is owing to another principle. The adja- 
cent air, from its proximity alone, acquires an opposite electri- 
city, whose intensity diminishes fast with the distance ; and 
hence the same effects, almost, are produced, as when the aerial 
particles are emitted from another body. 
If the pointed wires, A and B, possessing opposite electrici- 
ties, be brought near each other, the cone will become narrower, 
and extend ; the anterior part of the star will also protrude, 
while the rays will gradually bend more from behind, till the 
light forms a continued stream between the two points ; and 
thus a slow, though constant, agitation is communicated to the 
air, which will occasion a faint whistling sound. If two metal- 
lic balls are placed at a short distance apart, and connected, the 
one to the conductor, and the other to the cushion, while the 
machine is worked ; the aerial stream will play faintly between 
them, their electricities will become more intense, and their ac- 
tions will increase, till a violent impression overpower the resist- 
ance, and produce a quick discharge, which is not renewed un- 
til there is an equal accumulation of the electrical virtue. And, 
hence, the sudden concussion causes a sharp, loud sound. The 
cylinder of luminous air between the balls, by reason of the re- 
pulsion of its particles and their slight divergency, is protube- 
rant and faint, or purplish at the middle; and, as its motion is 
obstructed by the opposite dark stream, it makes sudden defle- 
xions and contorsions from its course, and occasions that forked 
appearance, which always obtains, in a certain degree. In dense 
