150 Contributions to Electricity and Magnetism. 
verse current will not have, as it were, as much space for its de- 
velopment, and therefore, will have less power in neutralizing the 
induction of the primary than before. But there is another, and, 
perhaps, a better reason, in the consideration that in the case of 
the increase of the number of elements of the battery, although 
the rapidity of the development of the primary current is greater, 
yet the increased resistance which the secondary meets with, in 
its motion against the action of the several elements, will tend to 
diminish its effect. Also, by diminishing the length of the pri- 
mary current, we must diminish (76) the intensity of the secon- 
dary, so that it will meet with more resistance in passing the acid 
of the single battery, and thus its effects be diminished. 
87. The action of the secondary current, in the long coil at 
the ending of the primary current, should, also, at first sight, pro- 
duce the same screening influence as the current in the inter- 
posed plate ; but, on reflection, it will be perceived that its action 
in this respect must be much more feeble than that of the similar 
current at the beginning ; the latter is produced at the moment of 
making contact, and hence it is propagated in a continuous circuit 
of conducting matter, while the other takes place at the rupture 
of the circuit, and must therefore be rendered comparatively fee- 
ble by being obliged to pass through a small portion of heated 
air; very little effect is therefore produced on the helix by this 
induction, (19.) The fact that this current is capable of giving 
intense shocks, when the ends of a long wire, which is transmit- 
ting a primary current, are grasped at the time of breaking the 
circuit, is readily explained, since, in this case, thé body forms, 
with the conductor, a closed circuit, which permits the compara- 
tively free circulation of the induced current. 
88. It will be seen that I have given a peculiar form to the 
beginning and ending of the curves, Figs. 17, 18, &c. These 
are intended to represent the variations which may be supposed 
to take place in the rate of increase and decrease of the quantity of 
the current, even in the case where the contact is made and broken 
with mercury. We may suppose, from the existence of analo- 
gous phenomena in magnetism, heat, &c., that the development 
of the current would be more rapid at first than when it approxi- 
mates what may be called theta of current saturation, or when 
the current has reached more nearly the limit of capacity of 
conduction of the metal. Also, the decline of the current may 
