THE SMITHSONIAN INSTITUTION. 



375 



The oil was heated by immersino; the test tube in a water bath; 

 hence Becquerel's measurements did not exceed the boiling point of 

 water. 



Becquerel infers from his observations that the decrease of conduct- 

 ive capacity is proportional to the increase of temperature. 



Consequently, the resistance of a metal increases by an equal 

 amount for each degree of temperature. The following table indicates 

 the amount of increase of resistance for one degree expressed in frac- 

 tions of the resistance at zero. 



Silver 0.0040 



Lead 0.0043 



Gold 0.0034 



Iron 0.0047 



Copper 0.0041 



From this Becquerel computed 

 of these metals at 0° and 100°, 



Platinum 0.0019 



Zinc 0.0037 



Cadmium 0.0040 



Tin 0.0062 



Mercury 0.0010 



a table for the conductive capacity 



in which, however, the conductive 

 capacity of silver at 0° is made equal to 100 ; to compare these data 

 with those of Lenz, I have re-computed the table, making copper =: 100. 



Metal. 



Silver.... 

 Copper... 



Gold 



Cadmium 



Zinc 



Tin 



Iron 



Lead 



Platinum. 

 Mercury .*. 



Difference. 



31.4 

 29.1 

 18.4 

 7.7 

 7.0 

 5.9 

 4.3 

 2.7 

 1.3 

 0.2 



It is evident that there is not the least accordance here with the re- 

 sults of Lenz, either in regard to the conductive capacity of the metal 

 at 0°, or in regard to the decrease of the same with increasing tempera- 

 tures. If the law found by Becquerel were correct, tlie factors of t~ 

 in the equations on the last page should be zero, and the factors of t 

 multiplied by 100 should be equal to the differences of the above 

 table. 



Finally, Miiller, of Halle, has investigated this su])ject (Pog. Ann. 

 LXXIII, 434) with the view of showing that a relation exists between 

 the increase of the specific resistance to conduction, and the increase 

 of specific heat. He assumed the measurements of Lenz with refer- 

 ence to resistance ; for verifying those numbers he instituted a series 

 of experiments himself with iron wire, the results of which accorded 

 well with those of Lenz. The increase which the resistance of zinc 

 and mercury underwent at increasing temperatures, and which Lenz 

 had not determined, Miiller found to be very nearly proportional to 

 the increase of temperature. 



With reference to specific heat at different temperatures, Mtiller 

 adopted the determinations of Dulong and Petit, with the assumption 



