396 



EECElfT PROGRESS IN PHYSICS. 



15 degrees, and also the instant when it was 16, 17, 18, &c., to 2 

 degrees, in this way it was found that the time required to raise th 

 temperature of the spirit of wine from — 



15 to 17 viz: 2' 



was 



1.05 minutes. 



2.22 



3.25 



4.30 



5.42 



6.53 



and hence it follows that the time t, necessary to raise the tempera-i 

 lure of the spirit of wine 1°, was on an average 0.542 minutes. 



The resistance to conduction of the spiral wire was ascertained byl 

 observing, (after the removal of the apparatus of fig. 47 from thel 

 circuit,) how many turns of the rheostat had to be inserted, in order, 

 to bring the current again to the same strength that it had with thel 

 heating apparatus in the circuit. 



The following table contains the results of a great number of such' 

 experiments: 



Three different wires of German silver Avere used in the experiments ; 

 that designated by a was the thinnest ; h was a little thicker than a 

 and c a little thicker than h. 



In this table s denotes the force of the current ; I the resistance to 

 conduction of the wire, expressed in units ; and t is the time neces- 

 sary to raise the temperature of the spirit of wine 1°. How the value 

 of t was determined each time from a series of experiments has already 

 been stated above. 



The quantity of spirit of wine poured into the jar was always nearly 

 the same, or 90 grammes on an average. 



If we compare all those series of experiments in which the force of 



