SCIENCE— ADVERTISEMENTS 



i t 



THALOFIDE CELL" 



A NEW LIGHT REACTIVE RESISTANCE 

 OF GREAT SENSITIVITY 



These new cells will lower their electrical 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 exposure to very low light 

 intensities. 



Write for Particulars 



Case Research Laboratory 



AUBURN, NEW YORK 



SPENCER SCIENTIFIC INSTRUMENTS 



WHETHER 



MICROSCOPES, MICROTOMES, DELINEASCOPES. REFRACTOMETERS 

 OR OTHER SCIENTIFIC APPARATUS 



MAKE AN INSTINCTIVE APPEAL 



TO THE LABORATORY WORKER 



It isn't only their accuracy and utility. It's 

 something in the finish, even more in the design, 

 but in addition to all these, it is those little 

 things — clever little devices, which accomplish 

 the same end but in a better way — exactly the 

 way that the laboratory worker wants them. 



These are the distinctive features of Spencer in- 

 struments, made distinctive because our design- 

 Spencer Delineascope Model O, with 400 watt flj^n nn '^''^' experienced laboratory workers, possess the 

 Mazda lamp, 2ji inch objective. Complete vP/U.UU laboratory view pomt. 



SPENCER DELINEASCOPES 



for lantern slides or opaque projection or both have incorporated in them the Spencer Transposer, 

 a patented mechanical means for handling the slides, doing away with the old antequated slide 

 holder. It gives a dissolving view on the screen, which is only attained in other outfits by using 

 two Stereopticons, one above the other. One Spencer Delineascope does it 



SPENCER LENS COMPANY 



BUFFALO, N. Y. 



