SCIENGE—ADVEBTISEMENTS 



3dii 



WALLACE 



Photomicrographic and Spectrographic 



COLOR FILTERS 



The color filters illustrated here were devised 

 by Dr. R. James Wallace, formerly Photo- 

 Physicist of the Yerkes Observatory and later 

 Director of the Research Laboratory of the 

 Cramer Dry Plate Company, primarily to enable 

 worlcers in photomicrography to obtain an 

 accurate photographic reproduction of objects, 

 the details of which are rendered conspicuous to 

 the eye by inherent or artificial color differentia- 

 tion. 



By their use, the field of application of 

 photography to bacteriology, histology, metal- 

 lography and spectrography is greatly extended 

 and the accuracy of conclusions drawn from a 

 careful study of visual impressions, rendered 

 permanent on the photographic plate, is in- 

 creased beyond measure. 



The Wallace Color Filters consist of a set 

 of ten gelatine coated glass plates two inches 

 square, each bound with a protecting cover 

 glass. The transmission values of these filters 

 are the result of years of research work on the 

 part of one who combines in a unique manner 

 the viewpoints of both physicist and photog- 

 rapher, and the ranges are therefore selected 



to cover practically every possible combination of photographic plate and desirable or undesirable 



color value in the specimen to be photographed. 



WALLACE COLOR FILTERS, set of ten, as described above, in neat wooden case covered 

 with imitation leather. Each plate is numbered for convenience in referring to 

 the scale of transmission ranges on the inside of the cover $12.00 



WALLACE COLOR FILTERS, same as above but with gelatine film mounted on optical 



glass of first quality. These will be made up to order only S24.00 



Bulletin No. 95S, now in preparation, gives a complete explanation of the application of color 

 filters to photomicrography and contains much information of value to those who are engaged in 

 such work. It will be sent free upon request. 



Central Scientific Company 



460 EAST OHIO STREET 



CHICAGO, U. S. A. 



