564 oN A NEW METHOD FOR ASCERTAINING 
cautions in using them. It is, therefore, more 
advantageous to dispense with the measurement 
of the voltaic currents, by employing equation 
3, in which the current is constant and the resis- 
tance variable. 
I take two pieces of thin wire, the conducting 
powers of which have been previously ascertained, 
and immerse one of them in a quantity of water, 
and the other in the substance whose specific heat 
is to be determined. I then place the wires in 
different parts of the same voltaic circuit, so as to 
cause the same current to traverse both of them 
consecutively. After the current las passed for 
a proper length of time, I note the increase of 
temperature which has occurred in the water and 
in the substance under examination. Thus I 
obtain two determinations of y in equation 3, 
one of them for water, and the other for the sub- 
stance under trial, from which the specific heat of 
the latter may be readily deduced. 
The method I have just described requires an 
accurate knowledge of the resistance of the wires 
by which the heat is evolved. The principal ways 
of ascertaining the resistances of wires to the 
passage of electric currents are those of Ohm 
