1884.] On the Permanent Temperature of Conductors, $c. 177 



the bottom. The copper sheet is about 0'2 of a millim., or O'OOS inch 

 thick. It is probable that it would be better a little thicker. With 

 this cell I can command about 45 amperes for hours together at any 

 time, only requiring to take, now and then, a fresh supply of sul- 

 phate of copper from the reservoirs. The new cell which is in process 

 of construction is 69 inches long by 46 inches, and 3 inches deep. 

 It has four reservoirs, and six zincs placed in two rows of three 

 each. 



Received June 19. 



P.S. In the foregoing paper, I have described the construction 

 and capability of a cell, whose dimensions are given, constructed 

 about the beginning of July, 1883. It was found necessary, almost 

 whilst I was writing, to take the cell to pieces, as it had become blocked 

 up with copper deposited in the natural course of nine months' 

 working. In putting the cell together again, with attention to small 

 particulars, which I shall not describe as they will naturally occur to 

 anyone who desires to use the arrangement, but which, I need scarcely 

 remark, make, with such great currents, all the difference between 

 success and non-success, I have obtained, through a current galvan- 

 ometer of which the resistance is -^^ of an ohm, a current of 

 63 amperes, which was quite steady. 



J. T. BOTTOMLEY-. 



June 16th, 1884. 



XVI. " On the Permanent Temperature of Conductors through 

 ' which an Electric Current is passing, and on Surface 

 Conductivity, or Emissivity." By J. T. BOTTOMLEY. With a 

 Note by Sir WILLIAM THOMSON, F.R.S. Received June 17, 

 1884. 



(Preliminary paper.) 



The experiments of which an account is given in the following 

 paper were commenced several months ago in connexion with -a 

 theoretical investigation by Sir William Thomson, " On the Effect 

 of Clothing," showing the dependence of the effect on the relation 

 between the dimensions of the covered body, and the dimensions and 

 physical properties of the covering. A primary object of the experi- 

 ments was the determination, for practical purposes, of the temperature 

 of electric light conductors. The preliminary experiments have led 

 to results which seem to be of considerable importance, and they 

 point to the necessity for a fresh determination of the " emissivity " 



VOL. XXXVII. N 



