46 



REPORT 1876. 



diiference between 2 and 3, by heating 2 and comparing it with 3 scarcely 

 heated, if at all, was 16. 



The above peculiarities suggested to me to make a set of experiments on 

 the plan of keeping the current going as much as possible. It was hoped 

 that thus a certain hmiting state, as regards temperature, would be arrived 

 at, which from the construction of the coils would in a great measure be 

 independent of small variations of temperature in the experimenting-room *. 



This method of proceeding would not introduce any error in the com- 

 parison of single coil with single, and the error introduced into multiple-arc 

 experiments would be regular and could be alloM'ed for. The last of the sets 

 of experiments given below was conducted on this plan with satisfactory 

 results. 



Tabular Scheme of best Experiments. 



* No special means of keeping the double and quintuple coils at a constant temperature 

 was resorted to. The object was not to find the resistances of the coils at any definite 

 temperature, but to compare them under the same circumstances as regards temperature. 

 It was therefore thought that any attempt to surround the coils with watei', &c. would 

 introduce greater errors than would arise from small variations of temperalui'e in the room 

 during the experiment. 



