CIENCE 



Friday, July 6, 1900. 



Single Copies, 15 cts. 

 Annual Subsckiption, $5.00. 



WM. GAERTNER & CO. 



Astronomical and Physical Apparatus 



5347 AND 5349 LAKE AVE., CHICAGO 



SPECIALTIES 



Standard Apparatus of New and Improved Designs 

 READING Microscopes and telescopes 

 Astronomical Telescopes Heliostats 



Spectroscopes Dividing Engines, Comparators 



michelson interferometers general laboratory apparatus 



Bolometers Universal Laboratory Supports 



FOSSIL BRYOZOA. 



Languages $ 



«3P 



We liave brouglit together 

 a series of about two hun- 

 dred species of authorita- 

 tively determined American Palaeozoic Bryozoa which we ofEer for sale in sets or as 

 single specimens. Write for list enumei'ating these with prices. 



WARD'S NATURAL SCIENCE ESTABLISHMENT, 30 to 40 College Ave., Rochester, N.Y. 



Book and Magazine Work m English and other 



languages, modern and ancient. Hand or linotype com- 

 position. 



Technical Works : mathematical, physical, chemical, 

 crystallographic, mineralogic, biologic, and philologic. 

 Grammars and dictionaries; interlinear, parallel and 

 phonetic te.xts. 



Examination Papers printed and delivered promptly in 

 sealed packages. Theses. Monographs. Catalogs. 



Translating, Transliterating, Editing, 



Samples anS estimates (urnisbcS on application. 



Company 



$ 



$ 



114 Fifth Avenue, New York, 



Willyoung 8" to I5"-110 Volt X-Ray Machine. 



TAKE NOTICE 



AFTER VACATION comes the FALL WORK, you will need 

 Apparatus then. DON'T WAIT BUT PLACE YOUR ORDERS 

 NOW FOR FALL DELIVERY. You wiU get your goods in time, 

 SAVE MONEY, and enable us to arrange our summer work and hold our 



trained force together. 



Send your list novj and get our quotations. 



WE MAKE A LARGE LINE OF SCIENTIFIC INSTRU- 

 MENTS OF PRECISION, MAINLY ELECTRICAL INCLUDING 

 GALVANOMETERS, STANDARDS OF RESISTANCE, PHO- 

 TOMETERS, ELECTROMETERS, OSCILLOGRAPHS, ETC. 



Repairs to all kinds of Instruments. Resistances readjusted in IN- 

 TERNATIONAL OHMS. 



CATALOGUE W-US pages, free on application. 



g^ELMER G. WILLYOUNG (Srphll&&'^), 82-84 Fulton St., New York | 



