Mr. J. T. Bottomley. Permanent Temperature [June 19, 



3 amperes, 5 amperes from the battery; then with 10 amperes, 

 20 amperes, and about 30 amperes from the dynamo-electric machine; 

 the last-named current overheating both the coverings and the wires 

 and burning some of them up. The differences of temperature were 

 wonderfully small, but they were decided. The following table shows 

 the wires arranged in order of coolness, and therefore of the efficiency 

 for emission of heat of their respective coverings : 



Current 



1-2 amperes H D C E F G R A 



3 , HDCEFGBA 



5 HDCEFGAB 



5 H D C E F GAB 



HDECFBGA 



10 

 20 



1)* 



H E C G B A 



With about 30 amperes 



Tin and mercury .... A 



Mercury B 



Bare surface (dim) . . C 



Cotton and shell-lac . . D 



Cotton covering E 



Shell-lac varnish .... F 



Bare polished G 



Lampblack H 



Surface slightly fused and blistered. 



Wire totally dissipated. 



No visible alteration. 



Coatings fused together. 



Covering burned off. 



Covering fused. 



No visible alteration. 



No visible alteration. 



It appears therefore that the surfaces stand as follows in order of 

 cooling efficiency : 



H, lampblack. 



D, cotton and shell-lac. 



C, bare wire, dim, in common unaltered condition. 



E, cotton-covered. 



F, shell-lac varnish. 



G, polished copper. 

 B, mercury surface. 

 A, tin and mercury. 



In order to show a comparison as to the amount of cooling effect, 

 may here quote the temperatures of these wires with a current of 

 5 amperes passing, and in air at 11 C. This was the highest 

 current I was able to apply with the battery I then had at command, 

 and with the mode of experimenting which I was using at the time 

 these experiments were made. The temperatures were determined ii 

 all the canes mentioned in the table above, but with the higl 



* Covering probably half burned in D and F. 

 heated. 



The wires bracketted were equs 



