67 
connection was established between the rings of each ma- 
chine and the commutator on the prolongation of the arma- 
ture axis. As the commutator necessarily revolved syn- 
chronously with the two armatures, it was found that the 
combined alternating currents were rectified, just as if they 
had proceeded from only one machine ; and were, conse- 
quently, available for electro-deposition, or for any other 
purpose for which a direct current might be required. 
Although this property of synchronous rotation has, as 
yet, been observed only in the case of several pairs, and a 
triple combination, of machines, yet the author sees no reason 
for supposing that it may not be extended to any number 
of machines that may be conveniently worked together from 
the same prime mover. It is necessary, however, to observe 
that, as the controlling power of the current is only calcu- 
lated to correct such minute deviations from synchronism 
as it is beyond the power of mechanical skill to prevent, the 
driving and driven pulleys should be, respectively, as nearly 
as possible of the same diameters ; as the correction of any 
considerable difference in the number of the revolutions of 
of the armatures, caused by differences in the diameters of 
the pulleys, must necessarily, be attended by a corresponding 
diminution of the useful effect of the current outside the 
machines. 
The author concludes his communication by directing 
attention to an important property of the magneto-electric 
circuit, which renders the commonly accepted theory by 
which the generation and propagation of the electric 
influence in voltaic circuits is explained, inapplicable to 
those circuits which are entirely metallic. Reference to this 
property is all the more called for at the present time, as the 
author finds that a want of acquaintance with it has given 
rise to no small amount of misconception on the part of 
several eminent mathematicians and electricians, who have 
examined his experiments on the electric condition of the 
