276 Dr. Hare’s Electrical Machine, &c. 
according to the manner in which the 
balls are associated with the positive 
or negative poles of the machine. 
When the small ball is attached to 
the positive pole, the spark is Jong, 
comparatively narrow, and of a zig- 
zag shape, such as lightning is often 
seen to assume; but when the situa- 
tion of the balls is reversed, the spark 
is straight and thick, not one third as 
long, and nothing of a zigzag shape 
ean be observed in it. 
According to the Franklinian the- 
ory, when any body is more highly 
charged with electricity than the ad- 
joining bodies, the excess of the fluid 
is attracted by them, while it is inad- 
equately repelled by the inferior quan- ea ph 
tity of the electric fluid, with which a . 
they are imbued. It follows that when = 9 x ; 
a small globe is made positive in the an AG! 
‘neighborhood of a large one, the ex- 
cess of electric matter in the former, 
is attracted by all the negatively ex- 
cited metal in the latter. When the small globe is made negative 
the metal of which it consists attracts all the electric matter in the 
large globe. Hence there is this difference in the two cases; the 
small globe being positive, a comparatively small movable mass of 
electric matter, is attracted by a large immovable mass of metal: the 
small globe being made negative, a large movable. mass of electric 
matter is attracted by a small immovable mass of metal. The charge 
being in both cases the effect of the same machine; the attractive 
power must be as great in one case as in the other. The forces by 
which the masses are actuated being therefore equal, it is quite rea- 
sonable that the greatest projectile power should be attained, when 
the small mass is movable. In that case, it will require less air to be 
seared i in order to effect a passage. 
2 is an analogy between the difference which T suppose to 
‘the case under consideration, and that which may be obsery- 
on the pevetrating: power of a rod, which is-blunt, and one 
which is pointed. 
‘ 
