TRANSACTIONS OF THE SECTIONS. 385 



them by means only of a slip of tinfoil, immediately throws oft' 

 the needle 25° ; which experiments, he conceives, can hardly 

 be reconciled with M. Becquerel's views respecting radiation: — 

 (Ann. de Phtjs. et de Cliim., Aout 1829.) 



4. That copper is, under all circumstances, a better con- 

 ductor both of heat and electricity than iron ; wherefore the 

 electro-positive quality of iron to copper cannot be due to supe- 

 riority of conduction ; and, by analogy, conduction should not 

 generally be the positive principle in this particular develop- 

 ment of electricity : — 



5. That iron, antimony, and zinc become positive by heating; 

 that is, a bar of either of these metals hot is positive to a bar of 

 the same metal cold ; a quality which he denominates thermo- 

 positive. 



That platinum, silver, copper, lead, tin, bismuth, become 

 negative by heating ; that is, a hot bar is negative to a bar of the 

 same metal cold, which he calls thermo-negative ; and thus the 

 metals are resolved into two thermo-electric classes. 



That the thermo-positive quality is possessed by the above- 

 named three metals in the following order : 



f"*""«"y'l. nearly equal. 

 Iron, J •' ^ 



Zinc. 



That the thermo-negative order is as follows : 

 Bismuth, 

 Silver, 

 Platinum, 

 Copper, 

 Tin, 

 Lead. 

 And that the order of thermo-electric reaction seems due to 

 the idio-positive or negative quality, compounded with that of 

 conduction, taking conduction directly in the thermo-negative 

 class, inversely in the thermo-positive. That is to say, anti- 

 mony and iron are not very different in thermo-positive power ; 

 but antimony is the worse conductor, and takes the lead. 



Iron and zinc differ little in conducting power ; but iron is 

 the stronger thermo-electric, and takes the lead. 



In the thermo-negative class bismuth is the worst conductor, 

 and strongest thermo-negative, and therefore takes the lowest 

 place. 



Silver is a better conductor, but stronger thermo-negative, 



than copper. The one quality should raise it, the other lower it, 



in the table, and accordingly the difference between those two 



metals is small; and Mr. Prideaux frequently finds copper 



1833. 2 c 



