in terms of the B. A. Unit (1864) of Electric Resistance. 363 



Table III. 

 (Temperature of all, 0° C.*) 



Silver 



Copper 



Gold 



Aluminium 



Magnesium ... 



Zinc 



Cadmium 



Palladium 



Platinum 



Cobalt 



Iron 



Nickel 



Tin 



Thallium 



Lead 



Arsenic 



Antimony 



Bismuth 



Mercury 



Platinum-silver 



alloy 



German silver 

 Gold-silver allov 



Specific resistance in terms 

 of the B. A. unit. 



Hard- 

 drawn. 



Pressed. 



002103 

 0-02104 



0-02697 



007244 

 0-08865 



An- 

 nealed. 



001937 

 0-02057 

 002650 

 003751 

 005106 



0*1 140 

 01166 

 01221 

 01 251 

 0-1604 



0-1701 

 2296 

 0-2527 

 0-4417 

 0-4571 

 1-689 



0-3140 



0-2695 

 1-668 



•270 



Specific conducting-power 

 of metre length and milli- 

 metre diameter. 



Hard- 

 drawn. 



4756 

 47-53 



3708 



3-18 



3-71 

 7148 



Pressed. 



13-80 

 11-28 



5-88 

 4-36 

 396 

 2-27 

 219 

 0-591 

 0-788 



An- 

 nealed. 



51-63 

 48-61 

 37-73 

 26-66 

 19-58 



8-77 

 8-58 

 8-19 

 7-99 

 6-23 



The platinum-silver alloy contains 66*6 per cent, silver, and is 

 that alloy which has been used for making the copies of the B. A. 

 unitf. On comparing these values with those deduced from the 

 actual ones found, as given in the secoDd Table, we find a difference 

 with the silver of about 3 per cent. This is explained in our paper 

 by the fact that the silver wire used was drawn in a peculiar 

 manner ; and on referring to another paper J, like differences will 

 be found in the conducting-power of silver. The differences in 

 the other cases will be chiefly due to not using the correct spe- 

 cific gravities; thus, for instance, the specific gravity of copper 

 used was 8*95. Siemens § found it to vary for wire between 8'89 

 and 892 ; using the value 8 # 91, we find the conducting-power to 

 be 47-64. 



* Phil. Trans. 1864, p. 197, value for lead given in the Table is wrong; 

 it ought to be 832, and not 8'23 (see Phil. Trans. 1862, p. 16). 



t Report of the British Association, 1864. 

 § Poggendorff's Annalen, vol. ex. p. 18. 



2 B 2 



Phil. Trans. 1862, p. 6. 



