NEw SERIES 
VoL. XXXV. No. 904 
The Superior Quality 
of Bausch& Lomb len- 
ses, microscopes, field 
glasses, projection ap- 
paratus, engineering 
and other scientific in- 
struments is backed by 
nearly Sixty Years’ 
Experience. 
SINGLE CoPizs, 15 Crs. 
FRIDAY, APRIL 26, 1912 ANNUAL SUBSCEIPTION, $5.00 
RAPID EASY CHANGES 
Science teachers appreciate the advantage offered by this Balopticon, of 
changing from any one form of projection to any other form instantaneously 
and easily. It is most efficient, durable and economical. The 
Bausch fomb a 
Convertible \ationat 
Balopticon 
projects interchangeably lantern slides by direct illumination — 
opaque illustrations and objects, up to 6 inches square, in vertical 
and horizontal plane as may be desired—microscopic objects, po- 
larized light and physical experiments. Every known form of 
projection is possible with maximum efficiency. 
The screen image is very brilliant. The optical and mechanical parts are of the 
highest grade and constructed on strictly scientific lines. 
DESCRIPTIVE CIRCULAR 15D SENT ON REQUEST. 
Bausch £3 lomb Optical ©. 
NEW YORK WASHINGTON CHICAGO SAN FRANCISCO 
LONDON ROCHESTER. NY. FRANKFORT 
