Friday, April 6, 1900. 



SiSGLE Copies, 15 cts. 



AlfXUAL SUESCEIPTIOS, 



. GAERTNER & CO. 



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Astronomical and Physical Apparatus 



152-158 EAST 56th ST., CHICAGO 



SPEOIALTIES 



SIMPLE MICROMETER tor use with 

 lur Standard Microscope and Telescope 



Standard Apparatus of New an 



READING Microscopes an 



Astronomical Telescopes Heli 



Spectroscopes Divii 



MicHELsoN Interferometers Gen 



3 rMpROVED Designs 

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)STATS 



iNG Engines, Comparators 

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dmeters 



Univetrsal Lab 



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' Supports 



MINIATURE INCANDESCENT LAMPS. 

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 X-RAT TUBES AND APPARATUS. 

 FLUOROSCOPES — — . 



Catalogues on Application. 



Edison Decorativs and Miniatare Lamp Department, 



{General Euectric Cokipany), 



HARRISON, N. J. 



WRITE FOR OUR NEW 



Supplement of Helicidae 



including the allied HeUcoid and Zonitid 

 snails and the American Bulimulids. Classifi- 

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 and other valuable matter. Free on Request. 



WARD'S NATURAL SCtENCE ESTABLISHMENT, 28 to 40 College Ave., Rochester, N.Y. 



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Electrical Measuring Instruments 



Manufactured by Morris E. Leeds & Co. 



Kelvin Galvanometers, Ballistic Galvanometers, Rowland D'Arsonval Galvanometers, 

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JAMES Q. BIDDLE, 



1034 Drexel BIdg., Philadelphia. 



Write for Illitstraied Catalogue B,"Elec- 

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