PCr & 
NEw SERIES. SINGLE Copiss, 15 cts. 
VoL. X. No. 236. FRIDAY, JULY Us 1899. ANNUAL SUBSCRIPTION, $5.00 
WM. GAERTNER & CO. 
Astronomical and Physical Apparatus 
152-158 EAST 56TH ST., CHICAGO 
SPECIALTIES 
STANDARD APPARATUS OF NEW AND IMPROVED DESIGNS 
READING MICROSCOPES AND TELESCOPES 
ASTRONOMICAL TELESCOPES HELIOSTATS 
3%-inch Telescope SPECTROSCOPES DIVIDING ENGINES, COMPARATORS 
on Universal Mounting MICHELSON INTERFEROMETERS GENERAL LABORATORY APPARATUS 
Price, $150.00 BOLOMETERS UNIVERSAL LABORATORY SUPPORTS 
MINIATURE INCANDESCENT LAMPS. 
MINIATURE LAMP RECEPTACLES. 
X-RAY TUBES AND APPARATUS. 
FLUOROSCOPES. 4 
Catalogues on Application. 
Edison Decorative and Miniature Lamp Department, 
(GENERAL ELECTRIC ComPanr,) 
HARRISON, WN. J. 
BIOLOGICAL SUPPLIES 
FOR CLASS WORK IN SCHOOLS AND COLLEGES. _ 
Starfish, Squids, Sea Anemones, Crayfish, River Mussels, etc. Specially Prepared for Class Dissection. 
WARD’S NATURAL SCIENCE ESTABLISHMENT, 28 to 40 College Ave., Rochester, N. Y. 
Apparatus for Wireless Telegraphy : 
An inexpensive but reliable outfit ; for colleges and schools as well as general experimenters. 
Comprising Special Induction Coil, Oscillators, Morse Key, Receiver with adjustable Co- 
herer, four-inch vibrating bell, specially wound high relay and necessary battery. 
Net Price for Complete Outfit (for distances up to 200 feet) $40 00. 
WY 
The subject of wireless telegraphy g 
is exciting such great interest JAMES G. BIDDLE WY 
that every laboratory should be ona O 0 x 
enulppedvonenpeninents. 1034 Drexel Building, Philadelphia, Pa. 
tESCEESS SE SEES ESSE SES ESSE SSS ESSEC ERE EE SSS SES EEE E CEES eeeeSeeeeece 
690222 2 2222929 29999229 
