Sir W. Snow Harris’s Researches in Statical Electricity. 87 
glass internally by means of a point connected with the electrical 
machine and projecting within the globe. 
9. That induction would go on within the globe were it free 
to do so, may be exemplified by one or two striking illustrations. 
Ezp. 6. Let a charged hollow globe of metal or glass, fig. 7, 
be placed on an insulating support as before, fig. 6; introduce 
within. it the small insulated carrier-ball 6, and whilst within the 
globe touch the carrier-ball with a light insulated wire, cb, pro- 
jecting freely into the air; remove this wire and then withdraw 
the carrier-ball ; the carrier-ball will be found charged with elec- 
tricity opposite to that of the globe; if the globe be plus, the 
carrier-ball will be minus, as might be expected. In this state 
introduce the carrier-ball again within the globe, and so as to 
touch the interior surface ; it comes away now quite neutral, 
that is to say, it has taken up positive electricity from the inte- 
rior surface, either by immediate contact with the electrical par- 
ticles in the case of a charged globe of glass, or through the 
medium of the metal surface in the case of a charged metal 
globe. 
The same result ensues if we touch the carrier-ball with the 
free wire when in contact with the interior surface, provided both 
be raised together off the surface previously to withdrawal of the 
wire, otherwise the carrier-ball immediately takes up positive 
electricity and comes away neutral. The insulated free wire, 
however, comes away positively charged with the electricity which 
had retired from the carrier-ball. 
If both the touching wire cd, fig. 7, and carrier-ball d, be 
raised together and removed without the globe, then the whole 
evinces positive electricity ; for the carrier-ball, whilst in contact 
with the interior of the sphere, having first become negative, 
immediately takes up positive electricity from the charged sphere 
and becomes neutral, and probably remains so whilst in contact 
with the sphere; whilst the exterior ball c of the touching wire 
evinces positive electricity, being necessarily charged with the 
electricity superinduced upon it by the first induction (3), fig. 2. 
On raising the whole system out of the sphere, however, this 
superinduced electricity expands over the whole; for the ori- 
ginal conditions are restored, whilst the new electricity taken up 
remains; hence the carrier-ball will now evince positive elec- 
tricity. And this is really what happens when an insulated wire 
and ball are introduced within the globe of sufficient length to 
project into the air. 
10. Although the two cases of charged globes to which I have 
thus called attention may at first appear different, the one being 
a case of a hollow globe of metal, the other of glass, yet a very 
little reflection will show that both cases are virtually the same 
