SCIENCE 



New Series 



Vol. LV, No. 1420 



Friday, Makch 17, 1922 



Single Copies, 15 Cts. 

 Annual Subscription, $6.00 



Bausch & Lomb 

 Apochromatic 



ectives 



For Immediate Delivery 



THE consideration of our customers, despite numerous delays, 

 has so encouraged us to carry forward our work of producing 

 really high-grade apochromatic objectives in the face of adverse 

 conditions that we believe many users will be interested to know 

 that we are now prepared to fill orders at once. 



Bausch & Lomb Apochromatic Objectives are of the highest 

 quality, so recognized by most critical users. Through extended 

 investigations we have been able to correct them for flatness of 

 field, without impairing working distance and numerical aperture. 



For immediate delivery we offer the 16 mm, 8 mm, 4 mm and 2 mm objec- 

 tives, as well as the complete line of Compensating Eyepieces. 



Write for new, illustrated descriptive leaflet. 



Bausch & Lomb Optical Go. 



409 St. Paul Street, Rochester, N. Y. 



New York Washington Chicago San Francisco London 



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 



es may sec -"^-^ ^^__^ 

 letter anl farther -^"^^ 



