416 On Electricity by Position or Induction. 
But the Professor’s experiments do not appear to have 
been made with all that circumspection which is necessary 
to investigatea ‘* general fact.” Indeed, it will be easily 
conceived, by those who are acquainted with the philoso- 
phical labours of Dr. Robison, that he must have taken 
many of his propositions on the authority of others; for it 
seems impossible, that all the facts which appear in his 
writings should have been verified by himself. ) 
From the following experiments, which were often re- 
peated with much care, it appears that a conductor electri- 
fied by position retains the electric fluid # long time after 
the excited surface is removed. 
Experiment.1.—A conductor AB, consisting of a brass 
tod twelve inches long, with a ball of the same metal fixed 
upon each end, was placed upon an insulating stand. A 
glass tube, being excited bv rubbing it with silk, was 
brought near the end A, but not within the striking di- 
stance. The pith-ball electrometers, which were suspended 
from the tnds of the conductor, diverged, and on examina- 
tion the end A contained the resinous electricity, and the 
end 8 the vitreous. 
The tube being removed, the balls at B collapsed and 
immediately diverged again with tesinon$ electticity, the 
end A continuing ih the same statt; and when the air 
was favourable for the experiment, the conductor showed 
signs of resinous electricity for more than an hour after. 
"Explanation. The conductor in its natural state con- 
tained the two eleciric fluids in such intimate tinion as to 
exhibit no marks of their existence. But when the excited 
tube was brought near A, it attracted the resinous electri- 
city towards that end of the conductor, and repelled the 
vitreous towards the other end. 
Now it may be easily understood, that the same power 
which repels the vitreous electricity towards B, will, at the 
same time, force some part of it out of the conductor at 
that end into the air, and consequently the conductor 
AB will contain less vitreous electricity than resinous; and 
when the excited surface is removed from the neighbour- 
hood of the conductor, the resinous electricity will pré- 
vail, which will not vanish when the excited surface is re- 
moved. ' 
As the particles of the same fluid repel one another, the 
charge of a conductor is continually dissipating, till all 
electrical signs vanish ; and it will be easily conceived that 
this dissipation will increase as the fluid is condensed : 
therefore an increase in the electrical energy applied at A 
will 
