igen 
140 Contributions to Electricity and Magnetism. 
in the acid, and in full operation. The current, in this case, rapid 
as may be its development, cannot be supposed to assume per 
saltum its maximum state of quantity ; on the contrary, from the 
general law of continuity we would infer, that it passes through all 
the intermediate states of quantity, from that of no current, if the 
expression may be allowed, to one of full development ; there are, 
however, considerations of an experimental nature which would 
i us to the same conclusion, (18,) (90,) and also to the farther 
inference that the decline of the current is not instantaneous. 
‘ding to this view, therefore, the inductive actions at the 
ling and the ending of a primary current, of which the 
forniifion and interruption are effected by means of the contact 
“with a cup of mercury, may also be represented by the several 
parts of the curve, Fig. 17. 
68. We have now to consider how the rate of increase or dimi- 
-nution of the current, in the case in question, can be altered by 
a change in the different parts of the apparatus; and, first, let us 
take the example of a single battery and a short conductor, mak- 
ing only one or two turns around the helix; with this arrange- 
ment, a feeble shock, as we have seen, (11,) will be felt at the 
making, and also at the breaking of the circuit. In this case it 
would seem that almost the only impediment to the most rapid 
development of the current would be the resistance to conduc- 
tion of the metal; and this we might suppose would be more 
rapidly overcome by increasing the tension of the electricity; 
and, accordingly, we find that if the number of elements of the 
battery be increased, the shock at making the circuit will also be 
increased, while that at breaking the circuit will remain neatly 
the same. ‘'T'o explain, however, this effect more minutely, W® 
must call to mind the fact before referred. to, (17,) that when the 
poles of a compound battery are not connected, the apparatus ac- 
quires an accumulation of electricity, which is discharged at the 
first moment of contact, and which, in this case, would more t 
pidly develope the full current, and hence produce the more it- 
tense action on the helix at making the circuit. 
69. The shock, and also the deflection of the needle, at break- 
ing the circuit with a compound battery and a short coil, (9,) 4P” 
pear nearly the same with a battery of a single element, because 
the accumulation just mentioned, in the compound battery, 5 
—- almost instantly, and, according to the theory (71) of 
