96 



Conducting Power at Temp, in Celsius's degrees. 



Mercury 1-63 22'8 



Bismuth 1-19 138 



Alloy of Bismuth 32-j 



parts ^ 0-884 24'0 



Antimony 1 part J 



Alloy of Bismuth 12 ^ 



parts I 0-519 22'0 



Tin 1 part J 



Alloy of Antimony 21 



parts, Zinc 1 part . . J 



Graphite, No. 1 0-0693 22-0 



Graphite, No. 2 0*0436 22-0 



Gas-coke 0'0386 25-0 



Graphite, No. 3. 0-00395 22'0 



Bunsen's Battery-Coke . . 0-00246 26'2 



Tellurium 0'000777 19'6 



Bed Phosphorus 0-00000123 24-0 



All the metals were the same as those used for my thermo-electric 

 experiments, with the exception of cadmium, which was purified by 

 my friend Mr. B. Jegel. 



The alloys of bismuth-antimony, bismuth-tin, antimony and zinc 

 were determined in order to ascertain whether, as they give, with other 

 metals, such strong thermo-electric currents, they might be more ad- 

 vantageously employed for thermo-electric batteries than those con- 

 structed of bismuth and antimony. 



Coppers No. 1, 2, 3 were wires of commerce. No. 1 contained 

 small quantities of lead, tin, zinc, and nickel. The low conducting 

 power of No. 1 is owing, as Professor Bunsen thinks, to a small 

 quantity of suboxide being dissolved up in it. 



Graphite No. 1 is the so-called pure Ceylon ; No. 3 purified Ger- 

 man, and No. 2 a mixture of both. The specimens were purified by 

 Brodie's patent and pressed by Mr. Cartmell, to whom I am indebted 

 for the above. 



The conducting power for gas-coke, graphite, arid Bunsen's bat- 

 tery-coke increases by heat from to 140 C. ; it increases for 

 each degree 0-00245, i. e. at C, the conducting power =100, and 



