SCIENCE— ADVERTISEMENTS 



COMPTON 



QUADRANT 



ELECTROMETER 



PROBABLY THE MOST 

 SENSITIVE ELECTRO- 

 STATIC INSTRUMENT 

 AVAILABLE 



Ask for Catalog 16 



PYROLECTRIC 

 INSTRUMENT CO. 



PYROMETRIC AND ELECTRICAL 

 PRECISION INSTRUMENTS 



636-640 EAST STATE STREET 

 TRENTON, N. J. 



Central Electrical System of Compton Electrometer 



"THALOFIDE CELL" 



A NEW LIGHT REACTIVE RESISTANCE 

 OF GREAT SENSITIVITY 



lliese new cells will lower their dectrical resistance 50 per cent. 



on exposure to .25 of a foot candle when the source used is a 



Tungsten Filament. Special cells are constructed which will do 



this in .06 of a foot candle. 



Their recovery after exposure is extremely rapid as also is 

 their response to the light stimulus which 

 is in marked contrast to the Selenium Cell, 

 especially on exposiu-e to very low light 

 intensities. 



Write for Particulars 



Case Research Laboratory 



AUBURN, NEW YORK 



