PHOTOMETRY OF THE ELECTRIC ARC 



141 



The curves showing the distribution of light for these 

 arcs are given in Fig. 49. While the total quantity of light 



FIG. 49. 



emitted by the open carbon arc is greater than that for 

 either the closed arc or for the first form of the magnetite 

 arc, it will be seen from the curves that the amount sent 

 in a horizontal direction is less for this arc than for any of 



