Research on some Standards of Light. 



499 



Table VIIL (See fig. 12.) 



Mass of Platinum Ingot 510 grammes. 



Intensity of the Light from 1 sq. cm. of Platinum at the Temperature 

 of Solidification - 1*004. 



Time. 1 



I: notometer 

 residing." 



Light. 3 

 



1 ft 







141:0 © 



-L I/O 



9ft 



1 A A 



1 loU 



3ft 



J, 4)0 O 



J- Veto 



40 



148 -8 



1-038 



50 



150 -1 



1 -005 



60 



150 -8 



-988 



70 



150 -3 



1 -001 



80 



150-4 



0-998 



90 



150 -9 



0-986 



100 



151 -0 



0-984 



110 



151-2 



0-979 



120 



152-8 



-942 



130 



155-8 



0-875 



140 



163-8 



0-722 



150 



173 -8 



0-567 



160 



183 '8 



0-444 



1 The time is counted from the instant at which the blow-pipe was stopped. 



2 The photometer reading is the distance in centimetres between the photometer 

 head and the incandescent lamp which served as a standard of reference. 



3 The unit of light is the mean of a number of determinations made under the 

 ''normal" conditions. 



Fig. 12. — Mass of the platinum ingot, 510 grammes (or 45 per cent, above the normal) ; intensity 

 of the light at the temperature of solidification, 1'004 (or 0*004 above the normal). 



O 10 20 30 40 50 60 70 80 90 100 /fO /£0 130 140 150 160 



Time in Seconds. 



metric observations. The " normal " conditions are chosen in order to 

 make the rate of cooling as slow as possible, and any variation in the 

 circumstances must necessarily cause the platinum to cool more rapidly. 



2 2 



