1894.] Specific Resistance of Pure Electrolytic Copper. 75 



least squares is the one which naturally suggests itself in calculating 

 this coefficient, but the calculation would be too laborious in com- 

 parison with the value of the figure arrived at. Therefore, in order 

 to ascertain which values could be used for calculating the temperature 

 coefficient (A<), the above observations were plotted in the usual way, 

 the co-ordinates being x = temperature arid y = specific resistance 

 in C.G.S. units. 



As previously stated, the values in column 6 of Table II have to be 

 multiplied by 1'6906 to give the specific resistance in C.G.S. units ; 

 to save labour the multiplication was done graphically (Graphic 

 Table No. 1). 



The resistances in column 6 of Table I reduced to C.G.S. units by 

 means of the graphical Table 1 are tabulated in another table 

 (Table III). 



The graphic Table No. 2 is a reproduction of Table III, and gives 

 the results of the above measurements. 



As the values formed so very nearly a straight line, two only are 

 selected : 



1707 C.G.S. units at 16-0 C. 

 1937 5V2 C. 



These gave the following equations : 



i707ss(l+16y) 



1937 = ff(l + 51-2y), from which 

 .7- = 1603- C.G.S. units 

 y = 0-004077. 



x is the specific resistance of the A deposit (hard drawn) at C., 

 and y is the temperature coefficient. By means of these values an 

 extrapolation was made from to 16 C. in the graphic Table No. 2. 



