572 



By making the Nernstlarap burn at different tensions, the gauging 

 could alwajs be carried out for different intensities of light. Likewise 

 different intensities of current were always used. These were measured 

 in a milliampère meter of "Koeler". The resistance of the platinum 

 plate was measured with the Wheatstone bridge. 



The values 2,43 i2, 2,50 £1, and 2,48 il, hence on an average 

 2,47 il were found for r, the electric resistance. 



i' r U'l 



'=ir,^ijï <^» 



= 7.40 X 10-7 X 0.434 = 3.2 X 10-" cal. per second, 

 i.e. that a deviation of 1 mm. is caused by 3.2 X 10-" cal. per 

 second. It should be stated here that the distance from the galvano- 

 meter mirror to the lath amounted to 174.3 mm. in these measurements. 

 I owe a few words of cordial thanks to Prof. Dr. VV. Reinders, 

 who enabled me to carry out this investigation in the Phys. Ohem. 

 Lab., and for the encouragement he gave me during the work. 



Delft, July 15, 1917. 



