30 



Messrs. W. E. Wiison and P. L. Gray. On the 



Fia. 3. Curve showing the relation of radiation to temperature in the case of (1) 

 bare platinum, (2) blacked platinum. 



the lowest temperatures, thus confirming our work of last year, but 

 in the case of the blacked platinum the curve is much less steep than that 

 given by a fourth-power law. In fact, after several trials it was found 

 that the exponent 3'4, in the expression q = aT x followed the curve 

 fairly well, but that a formula of the form 



would fit both curves, the values of a and 6 being obtained from the 

 respective experiments in the two cases. 



In this expression, as before, q represents quantity of radiation, T 

 the absolute temperature of the radiating surface, T the 



