SCIENCE 



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New Series 

 Vol. LI, No. 1329 



Friday, June 18, 1920 



SmGLE Copies, 15 Cts. 

 Anhuai, Subsckiption, $6.00 



Common Sense 

 Will Tell You- 



— that a message visualized gets into the student's conscious- 

 ness much faster than the message spoken. Tie up the spoken 

 word with the picturized word through the 



^ausch^lomb 



BALOPTICON 



THE PERFECT STEREOPTICON 



A superior equipment producing'jsharp, clear, vivid im- 

 ages. Automatic, noiseless, economical. Even distribution 

 of light is insured by the new gas-filled Mazda lamp. Com- 

 bination models, projecting both slides and opaque objects 

 such as maps, post-cards, photos, etc., $81.00 up. Models 

 for slides only, $50.00 up. 



Bausch ^ Ipmb Optical Q. 



552 ST. PAUL STREET 



NEW YORK WASHINGTON 



ROCHESTER, N. Y. 



CHICAGO SAN FRANCISCO 



Leading American Makers of Photographic Lenses, Microscopes, Projection Apparatus 

 (Balopticons) , Ophthalmic Lenses and Instruments, Photomicrographic Apparatus, Range 

 Finders and Gun Sights for Army and Navy, Searchlight Reflectors, Stereo-Prism 

 Binoculars, Magnifiers and other High-Grade Optical Products. 



