and the Influence of Temperature on the Resistance of Metals. 197 



the same mercury in tubes carefully picked from a large quan- 

 tity, lie does not arrive at a greater accuracy than I did with 

 alloys made in different places, by different persons, of different 

 gold and silver, and drawn by different wire-drawers. If, on the 

 contrary, I had made and drawn the eight alloys myself of the 

 same gold and silver, I should undoubtedly have obtained re- 

 sults not varying 01 per cent. If now different experimenters 

 determine the conducting power of mercury, is it not probable 

 that much greater differences would be found between their 

 results than those obtained by M. Siemens himself '? Now it so 

 happens that different observers have already determined the 

 conducting power of mercury. Let us compare their results ; and 

 we will first compare the conducting powers of the metals, 

 taking silver =100, and afterwards taking mercury =100. 

 Now I maintain that if the values obtained for one and the 

 same metal by these different observers agree better when com- 

 pared with silver than with mercury as unit, then M. Siemens's 

 proposed standard must be useless as such. 



Table II. — Conducting Power of Metals. Silver = 100. 





Siemens. 



Lenz, 



Becquerel. 



Matthiessen. 



Silver* 



Copper* 



Gold* 



100 

 96-9 f 



1*4*2 



1-72 



100 

 73-4 



58-5 



22-6 



130 



10-7 



10-4 



3-42 at 18-9 



100 



95-3 



68-9 



26-3 



25-7 



150 



131 



8-8 



8-6 



1-86 



100 



99-5 



78 



23-8 

 - 29-2 



12'3 

 14-4 at 20-4 



g.q 



10-5 at 207 

 1-65 



Cadmium ... 



Tin 







Platinum* ... 

 Mercury 



Table III. — Conducting Power of Metals. Mercury = 100. 





Siemens. 



Lenz. 



Becquerel. 



Matthiessen. 



Silver* 



Copper* 



Gold* 



5820 

 5640 



"825* 

 100 



2924 

 2146 

 1710 



"659 

 380 

 312 

 304 

 100 at 18-7 



5376 



5123 



3704 



1414 



1382 



810 



704 



473 



462 



100 



6060 

 6030 

 4727 

 1442 

 1770 



745 

 872 at 20-4 



503 

 636 at 20-7 



100 



Cadmium ... 



Zinc 



Tin 







Platinum* ... 

 Mercury 



* Hard-drawn. All temperatures 0°C, except when the contrary is 



stated. 



t Value given in 2nd paper 1 00 



