^58 Influence of Colour on the 



Cylinder y No. 1, 'variously coated — continued. 



The radiating power being greater, as the time of cooling is 

 less, we have the order of radiating power of the different co- 

 loured substances as follows : — white, red, brown, orange, black, 

 green. Omitting in this enumeration the blackened surface of 

 the red oxide of lead, which had passed in thickness the maxi- 

 mum radiating thickness, and is only comparable with the result 

 which precedes it, the change of colour effected by changing the 

 surface sulphuret of lead (black or rather brown), increases the 

 radiating power in the ratio of 1.03 to 1, which is within the 

 average of error. 



The following results, given in order of time, and reduced by 

 the standard, were obtained with cylinder No. % 



