SCIENCE. 



ui 



Electrical Batteries for Medical Purposes. 



CHICAGO, 



NEW YORK, 



Manufacturers of and Dealers in 



STATIONARY GALVANIC BATTERIES, PORTABLE HIGH 

 ELECTROMOTIVE FORCE BATTERIES, CHLORIDE 

 OF SILVER BATTERIES, GALVANO-CAUTERY 

 BATTERIES, FARADAIC BATTERIES, POCK 

 BATTERIES, BATH APPARATUS, AND 

 ELECTRODES. 



mm 



EDISON'S 



Electric Pen & Duplicating Press, 



f. xtremely JJseful Jnvention 



Dr. Butler's Plumbago Rheostat, 



PLIABLE SPONGE ELECTRODES, &c, &c. 



DUPLICATING WRITTEN OR PRINTED MATTER. 



CATALOGUES ON APPLICATION. 



,000 Copies from a Single Writing, at the Rate of 400 an Hour. 



Address all Orders to 



Western Electric Man'fg Co. 



38 Union Square, 

 — NEW YORK — 



CITY. .^PRICE 



. is successfully used by Schools, Colleges, Banks, Commission Houses, Mercantile Firms, Lawyers, 

 Ministers, Copyists, and every person or firm desiring a number of duplicates of any document. 



10,000 fens now in pse and tfye Pemand Readily jncreasing ! 

 No. 1, $25.00; No. 2, $30.00; No. 3, $35.00 



Description and Samples of Work sent on Application. 



EDISON'S ELECTRIC PEN AND PRESS, 



38 Union Square, New York Citv. 



James W. Queen & Co.. 

 OPTICIANS, 



924 Chestnut St., Philadelphia. Pa. 



Magnifying Glasses, Microscopes, 

 Mounting Materials, Insect Pins, 

 etc. , etc. 



Catalogues sent on Application. 



Part ist, Mathematical Instruments. 



" 2d Optical Instruments. 



" 3d Magic Lanterns and Slides. 



" 4th Physical Instrument. 



FOR SALE CHEAP. 



A Zentmayer Binocular Centennial 

 Stand, and large amount of accessories 



List Price $580. Will be sold for $3 10. 

 J. W. S., care of Office of " Science." 



SCIENCE 



A. WEEKLY JOURNAL OP SCIENTIFIC PROGRESS 



Vol. II. No. 44, ------- April 30, 1881. 



CONTENTS. 



Mr. Edison and His Lamp (Edit.) ; Congreso Internacional de Americanistas ; The Unity of Nature, VII., by the Duke 

 of Argyll ; Dolbear on the Nature and Constitution of Matter ; A Critique, by William H. Dopp ; Intra-Mercurial 

 Planets, by A. Hall ; The Solar Parallax, by D. P. Todd ; Books Received ; Notes, Astronomical, Chemical, 

 Microscopical, Physical, &c, &c, &c. 



Subscription, Four Doli-ars a Year. 



Single Numbers, Ten Cents. 



