SCIENCE-ADVERTISEMENTS 



Our Laboratory Spectrometers 



are sold in competition 

 with instruments of 

 European make to many 

 of the best laboratories 

 throughout the world. 



Spectrometer 

 L4020— $80.00 



A New Student's 



Spectrometer 



L 4022 



Send for Catalog and further details. 



WM. GAERTNER & CO. 



Physical and Astronomical Instruments 



5345-49 Lake Ave. CHICAGO 



" THE CAMERA OF QUALITY " 



POLYGON CAMERAS 



with 



Rietzschel Double Anastigmats 



are the embodiment of all that is desirable in cameras. They are compact, small, and 

 light in weight, yet they are very reasonable in price: "They fit the Pocket." They 

 are made from miniature size up to 5x7 inches, in all styles. All are built of light but 

 indestructible metal ; all are leather covered ; all have leather bellows ; all have rising, 

 falling and cross front ; all have detachable lensboard ; all have quickly reversible 

 ground glass ; all are fitted with double anastigmats, the better ones with the finest 

 cemented lenses ever put on the market, in compound shutter. 



We also sell 



ERNEMANN Cameras and Double Anastigmats 

 MEVER CAMERA «& IINSTRUMEINT CO., Inc. 



18 West 27th Street, NEW YORK 



IMPORTERS OF AND DEALERS IN SCIENTIFIC INSTRUMENTS 



