SCIENC 
NEW SERIES. SINGLE COPIES, 15 CTS. 
VoL. X. No. 260. FRIDAY, DECEMBER 22, 1899. ANNUAL SUBSCRIPTION, $5.00 
THREE ELEMENTS or our success 
Have been the three LENSES with which 
our most popular Microscopes are equipped 
a 
3 inch Objective. 4 inch 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. 
BRE Coun eit CHICAGO. N. St. Paul Street, ROCHESTER, N. Y. 
