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XXIX.—ON THE METHOD OF CHARGING HOLTZ’S ELEC- 
TRICAL MACHINE, sy W. 8S. M‘CAY, m.a., F.1T.c.p. 
[Read March 17th, 1879. ] 
Everysopy knows that Holtz’s Electrical Machine produces 
surprising results when it has once been started, but nearly 
everyone knows that it is very hard to be sure of starting it 
when required. 
The method of starting the machine I am about to put forward 
is probably not new, but as all the text-books say that it should 
be started in the originally described manner, and none of them, 
as far as I am aware, mention any other mode of doing it, I 
thought it might be worth while to bring before the Society the 
method devised by myself, and found uniformly successful in 
Trinity College. I am bringing it forward in the hope that 
Dublin Physicists, at least, may not waste their precious time in 
vain attempts to follow the directions of the books. 
The method of starting Holtz’s Machine, originally described, 
consists in charging the paper armatures, by bringing an excited 
plate of ebonite near one of them. I have never known this 
method succeed, and on account of the induction acting through 
the plates on the combs, I am sure that it would very generally 
be uncertain in practice. I have known the machine to be suc- 
cessfully started by charging one of the armatures by means of 
another electrical machine, but even this frequently failed. 
The method I am about to describe of starting Holtz’s Machine 
occurred to me from the very simple consideration that when 
the machine has been started, and the knobs separated, one of 
the conductors is highly charged with (say positive) electricity, 
and the other with negative if insulated, or none if put to earth ; 
and so it appeared to me that if before the Machine was started 
I could get up and maintain, by external means, such a state of 
electrification on the conductors, and then work the Machine, 
that the armatures would become properly charged by a process 
precisely the inverse of that by which they are supposed to 
charge the prime conductors in the original method. 
Accordingly I separated the knobs of the two prime conduc- 
tors, and connected one by a brass chain with the prime conduc- 
tor of any other Electric Machine, and the other with the ground. 
