SCIENCE 



Friday, April 27, 1900. 



Single Copies, 15 cts. 

 Annual Sdbscriftion, $6.00 



THREE ELEMENTS 



OF OUR SUCCESS 



Have been the three LENSES with which 

 our most popular Microscopes are equipped 



f inch Objective 



^ inch Objective. 



Tj inch Oil Immersion Objective. 



The 2=3 inch Objective possesses the large field, depth of focus, and 

 high resolving power which make a low-power lens desirable. 



The 1=6 lias remarkable working distance, making it especially adapted 

 to general laboratory work, and at the same time resolving, magnifying, and 

 illuminating power equal to the best. 



The 1 = 12 inch Oil Immersion has so many excellent features that 

 only a trial can demonstrate them. Unusually long working distance, ex- 

 treme flatness of field, high resolving power, and absolute permanency of the 

 materials of construction are a few of the good qualities. Our method of 

 mounting the delicate hemispherical front lens secures the greatest possible 

 permanency and the least liability to leakage. 



Bausch & Lomb Optical Co. 



Branches : 



NEW YORK and CHICAGO. 



N. St. Paul Street, ROCHESTER, N. Y. 



