98 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



arc-lamp (figs. 10, 11) may be used, as desired, for constant current or for 

 variable current, and has the further advantage that its current-strength 



i<u;itiu>i-MttMmtti,r,: 



jPlG.114. 



Fig. 15. 



may be varied at pleasure by regulation of the resistance. The lamp is 

 thus also useful for experimental purposes. In the projection of 



Fig. 16. 



Fig. 17. 



diapositives the lamp is used in an inclined position, and for 'that 

 purpose the upper carbon, in order to attain the optimum position of 



