TRANSACTIONS OF THE SECTIONS. 27 
Ss 
diminished or destroyed ; in addition, we find the magnetizing power 
the battery lessened, or altogether interrupted, for the bar W W is 
longer able to attract E as before. Dr. Faraday had ascribed the 
appearance of the secondary current to the production of a current 
the parallel wire, which current, had that wire not been present, or 
d its extremities not been united, would have been found in the 
nducting wire itself; and he supposes the parallelism of the wires to 
necessary in the arrangement, yet, in the present case, the wires 
e not parallel, though the effects remain unchanged. It is possible 
fo unite the extremities of helix B with the helix of an electro-magnet 
such a manner as to excite the latter. When the apparatus is 
e to act so weakly as that the hands may be retained on the 
nders for a number of rapidly succeeding shocks, it is sometimes 
y difficult to disengage them. He was induced to believe that 
easing the number of galvanic circles, without diminishing the 
of plates, would increase the effect. He found it more useful 
to increase the energy of the battery by strengthening the acid mix- 
ture, than by enlarging the plates. When too powerful a battery is - 
used, rendering the contact between some of the connecting wires less 
yerfect, made the machine uniform in-its action. Jacobi says that, 
in his experiment, increasing the battery did not increase the effect ; 
but Mr. M‘Gauley showed the contrary, by experiment, in this case. 
Still, whatever was the reason, he observed, he did not, even in an 
arrangement similar to that of Professor Jacobi, find that a very small 
battery produced an effect equal to that of a larger one: so much do 
circumstances, unnoticed or unappreciated, sometimes alter, not only 
the extent, but the nature of results. 
ee eee 
On the Interference of Electro-magnetic Currents. 
By M. De ta Rive. 
beet A 
_ After a brief réswmé of the known properties of electro-magnetic 
currents, M. De la Rive adverted to some new results at which he had 
arrived in studying them. He remarked, that in chemical decompo- 
on effected by these currents, the individual force of each was 
eater the more rapidly they succeeded each other ; so that, to de- 
apose a given quantity of water, it becomes necessary to have a 
nber of these currents, so much the greater as the succession is less 
id. There is, however, a limit beyond which the force of the 
rents is not augmented by any further augmentation of the rapidity 
the succession. When plates of platina are employed, instead of 
es, in the decomposition of water, the decomposition ceases. to take 
ce when the surface of contact of the metal with the liquid sur- 
ses a certain limit. Nevertheless, the current, far from diminish- 
‘in intensity, becomes, on the contrary, more intense—as is shown 
by the indications of a metallic thermometer—the helix of which, 
jlaced in the current, furnishes a measure of its calorific energy. As 
