SCIENCE 



New Series. 

 Vol. XI. No. 269. 



Fkiday, February 23, 1900. 



Single Copies, 15 cts. 

 Annual Subsceiption, S5.00 



THREE ELEMENTS 



OF OUR SUCCESS 



Have been the three LENSES with which 

 our most popular Microscopes are equipped 



* inch Objective 



^ inch Objective. 



tV 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 has 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. 



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



Branches : 



NEW YORK and CHICAGO. 



