496 



Mr. J. E. Petavel. An Experimental 



Fr&. 10 (see Table V, fig. 8, and p. 495).— Illustrating the graphical method used 

 in reducing the observations. 



0-86 



Q-B5 



0-B4 



0-9i. 





















1 



1 









I 











1 





< 











1 

























































































2. The mean rate of change of the intensity of the light during the 

 so-called " constant period " exceeds - 03 per cent, per second. 



In the course of the present investigation, observations were taken 

 for some three hundred curves, but for obvious reasons only a few of 

 the most typical are recorded here. 



It must be clearly understood that the present experiments were not 

 undertaken with a view of obtaining any absolute determinations, but 

 purely as a preliminary investigation. The objects in view were : 



1. To ascertain the most favourable experimental conditions. 



2. To determine the degree of accuracy to be obtained under these 

 conditions. 



The results are expressed in terms of the quantity of light emitted 

 by 1 sq. cm. of platinum at its temperature of solidification, and under 

 the following conditions : — 



The total mass used was 345 grammes in the shape of a disc. The 

 area of the upper surface of the disc was 17 sq. cm. The diameter of the 

 hole in the cover of the furnace was 1*6 cm. The observations were taken 

 after the blow-pipe had been alight for fifteen minutes, burning 0*8 cubic 

 foot of hydrogen per minute, the two gases being mixed in the ratio of 

 four volumes of hydrogen to three of oxygen. The above conditions 

 will, for the purpose of this investigation, be taken as the " normal 



