80 Specific ^Resistance of Pure Electrolytic Copper. [May 24, 



mixture of pure sulphuric acid and distilled water, the cathode being 

 another strip of copper enclosed in a new and clean cell of porous 

 earthenware. The current was continued until the solution had the 

 desired strength. From this solution a sheet of copper was deposited 

 ou. a polished copper plate, as described in the first part of this paper, 

 the rocking tank A copper still being the anode. The deposit was 

 then cut into narrow strips and drawn through sapphire dies to the 

 requisite diameter. It was finally annealed by heating in a current 

 of CO 2 gas. 



Specific Gravity of the Copper B. It was ascertained by weighing 

 equal lengths of this wire and sample A (both drawn through the 

 same die), that their specific gravities did not differ to any appreciable 

 amount, the density 8'959 at 15 C. was therefore taken for this 

 sample B. 



Diameter of the Wire. 300 cm. of the wire weighed 5' 5845 grams ; 

 the diameter is therefore 



X = 



5845 



-959x300 



= 2x0-025717 = 0-051434 cm. 



Electrical Measurements. The same arrangements were employed 

 as previously. 



Table V. 



To ascertain the specific resistance in C.G.S. units, the constant by 

 which to multiply 986 (last column, Table V) was calculated in the 

 same manner as in Equation No. 7, and -by substituting - 025717 for r 

 instead of 0'025755, the constant 1'6856 is obtained. We thus have 

 the specific resistance of the pure copper : 



ffl6 . 9 o c = 986x1-6856 = 1662 C.G.S. units. 



Measurements at higher temperatures for ascertaining the tempera- 

 ture coefficient were made, but the data were unfortunately lost. The 

 result, however, was 



A, = 0-00415. 



