v 



{Established 1843.) 



•\X7-ILLIAM T. GREGG, 



* * Manufacturer and Importer Astronomical, En- 

 gineering, and Photographic Instruments. American 

 and Foreign Photographs. 



318 Broadway, corner Pearl Street, New York. 



Inspection and correspondence solicited. 



SCIENCE 



^he Travelers Insurance Company 



of Hartford, Conn., organized 1864, issues both Life Policies and 

 Accident Policies. Only large accident company in America. Only $5 

 a year to professional and businessmen for each $1,000 insurance, with 

 $5 weekly indemnity. Has paid policy-holders nearly $11,000,000. All 

 policies non-forfeitable. All claims paid, without discount, and imme- 

 diately on receipt of satisfactory proofs. 



QUSTAV E. STECHERT, 



766 Broadway, New York. 

 Importer of Scientific Books and Periodicals. 

 Branches : Leipzig, Hospital Str. 16 ; London, 26 

 King William Str., Strand. 



B WESTERMANN & CO., 



(Established 1848.) 



838 Broadway . . . NEW YORK, 



FOREIGN BOOKSELLERS AND IMPORTERS. 



MAGAZINES AND REVIEWS!! 



Complete sets of all the leading Magazines and Reviews, and 

 back numbers of several thousand periodicals, for sale at low 

 rates. Full files of Science, either bound or unbound, or odd 

 volumes and numbers supplied. Subscriptions taken on favorable 

 terms for any periodical either American or foreign. Address 

 THE AMERICAN AND FOREIGN MAGAZINE DEPOT, 

 47 Dey street, New York City. 



"THE ELECTRICAL REVIEW," 



An illustruteri weekly journal, is theacknowled^ed lead- 

 er in the world of electrical science. Edited with cure, 

 its editorial opinion is reliable, its news columns bright 

 and instructive. *3.00 per year ; single copies, 10 cents. 



23 PARK ROW, NEW YORK. 

 tn?~ Best advertising medium in the electrical field. 



GERMAN SIMPLIFIED. 



An eminently practical new method for learning the German larj- 

 KuaKe. Edition for self-instruction, in 12 numbers, at 10 cents each, 

 sold separately ; school edition (witbout keys), bound in dOlfc.fl.2S. 

 For sale by all booksellers ; sent post-paid on receipt of price by Prof- 

 A. KNOFLACH, 140 Nassau St., New York. Prospectus mailed free. 



"Rinding 



Volumes of Scicnc ( I. , 1 1 ., and 1 1 1 .) for sale , bound or 

 unbound. Those who desire to have their own copies bound 

 are requested to write to J. H. H. McNAMEE, 418 Harvard 

 Street, Cambridge, Mass., and not to the publisher. 



AN ILLUSTRATED WEEKLY JOURNAL. THE SCIENCE 

 COMPANY, OWNERS AND PUBLISHERS. 



Officers and Directors.— D. C. Gilman, of Baltimore, President - 

 Simon Newcomb, of Washington, Vice-President; Gafdiner G. Hi b- 

 bard, of Washington ; Alfx. Graham Bell, of Washington ; O. C. 

 Mafsh, of New Haven ; J. W. Powell, of Washington. 



SCIENCE appears every Friday. Volumes begin in July and January. 

 Communications will be welcomed from any quarter. Rejected manu- 

 scripts will be returned to the authors only when the requisite amount of 

 postage accompanies the manuscript. 



Address all correspondence about contents cf paper to 

 u Editor of Science," 



47 Lafayette Place, 



New York. 



Subscriptions. — In United States and Canada, $5 a year. 



In Great Britain and Europe, $6 a year. 

 Address all financial correspondence to 



" Publisher of Science," 



743 Broadway, 



New York. 



The Treasurer of the Science Company will in all cases send 

 a receipt for money paid to the publisher. 



% 



HORSFORUS 



Acid Phosphate 



(Liquid), 



For Dyspepsia, Mental and Physical Exhaustion, 

 Nervousness, Wakefulness, Diminished Vitality, 

 etc. 



Prepared according to the directions of Pro- 

 fessor E. N. Horsford of Cambridge, from the 

 phosphates of lime, magnesia, potash, and iron, 

 with phosphoric acid in such form as to be readily 

 assimilated by the system. 



Universally prescribed by physicians. 



It is not nauseous, but agreeable to the taste. 



No danger can attend its use. 



Its action will harmonize with such stimulants as 

 are necessary to take. 



It makes a delicious drink with water and sugar only. 



Prices reasonable. Pamphlet mailed free. 



Rumford Chemical Works, Providence, R. I. 



PRIZES OFFERED BY THE BOSTON 

 SOCIETY OF NATURAL HISTORY. 



THE WALKER PRIZES. APRIL, 1886. 



The Society offers a first prize of from $60 to $100, and 

 a second prize of $50, for the best memoirs in English, on the 

 following subject: 



" Original unpublished investigations on the embryology of 

 any plant." 



The essays are to be sent to the Secretary of the Society, 

 on or before April I, 1886, accompanied by a sealed envelope, 

 endorsed with a motto corresponding to one on the essay, 

 containing the name and address of the writer of the essay, 

 which must not, in any way, be apparent in the manuscript. 



Boston, Mass. EDWARD BURGESS, Secretary. 



Kntered at the Post-office in New York as second-class mail matter. Copyright, 1886, l>y 'I he Science Company 



