660 



SUMMAKY OF CUKRENT RESEARCHES RELATING TO 



A gallery is fixed to the lamp upon which a chimney is placed. The 

 chimney is provided with a bullseye condenser which is placed in align- 

 ment with the positive carbon. At right angles to this and also supported 

 in the chimney is a pin-hole camera. This will be found most useful in 

 enabling the user to see an image of the arc when the carbons require 

 feeding as if thrown on a ground-glass screen, and it can at once be seen 

 what the length of the arc actually is. 



The carbons used are 8 mm. cored placed in a horizontal position, 





Fig. 131. 



and 6 mm. solid for the vertical, when the current does not exceed 

 5 amperes. 



There is a clamping arrangement which holds the lamp at any posi- 

 tion on the upright of stand, and another which permits the whole lamp 

 to be tilted to any angle required. 



This arc lamp can be used for the projection lantern without the 

 chimney, but the latter is needed when employed for microscopic or 

 spectroscopic work. 



An inexpensive yet efficient resistance suitable for use on a 100 or 

 200 volt current is supplied for use with this arc lamp. 



