PHOTOMETRY OF THE ELECTRIC ARC 131 



Since the intensity of light becomes less with these lengths 



10/10 Soft 



5)Cl00 



4,000 



3. 





10 12 14 16 M.M. 

 LENGTH IN MM. 



FlG. 40. 



and the power consumed becomes greater, the ratio be- 

 tween the two becomes rapidly smaller with arcs more 

 than a few millimeters long. 



Fig. 40 illustrates also the 

 difference between different 

 kinds of carbons and shows 

 how impossible it is to make 

 any definite statement con- 

 cerning the candle power of | 2 ' 000 

 arc lights, or to give any 

 formula which will hold 

 with different carbons. No 

 two kinds of carbons vary 

 in the same way. One might 

 almost say that no two pairs 

 of carbons of the same make show the same results. 



Measurements were made by Ayrton with different cur- 



1,000 



io 20 30 35 

 CURRENT IN AMPERES 



FIG. 41. 



