SCIENCE-ADVERTISEMENTS 



WM. GAERTNER & CO. 



Astronomical and 

 PhysiceJ Apparatus 



SPECIALTIES 



Standard Apparatus of New and Improved Desterns 

 Reading Microscopes and Telescopes 



Dividing Engines 



Astronomical Telescopes 



Spectroscopes 



Micfaelson Interferometers 



Heliostats 



Comparators 



General Laboratory Apparatus 



Universal Laboratory Supports 



5345 and 5349 Lake Ave. 



CHICAGO 



Portable Equatorial Telescope w«A 

 Driving Clock. 



Shells! Shells! 



An anusual opportunity for some institution or concholo- 

 gist. About 5,700 species and varieties ; over 50,000 speci- 

 mens. All correctly named and labeled. The result of 60 

 years' collecting. Very moderate price. Address 



J. C. ROWELL 

 3415 West Street Oakland, California 



BUY SCIENCE APPARATUS 

 |— Direct From Factory — i 



Yon pave money by buying Chapco Tested and 

 Guaranteed Laboratory Apparatus as we sell direct 

 from factory to school thus you escape alltheheavy 

 o%-erhead charges and selling expenses of those 

 who sell through travelers. Write for FREE 

 copy of latest Chapco Purchase Guide Ko. 11 

 and state your schi 



Chicago Apparatus Co. 65 s.oiinfon St. Chicago 



MARINE BIOLOGICAL LABORATORY 



■WOODS HOLE, MASS. 

 biuioglcal Material 



1. Z00I0S7. Preserved maveriE.1 of all types of animali 

 for class work and for the museum. 



2. Embryology. Stages of some invertebrates, fishes (in- 

 cluding Acanthias, Amla and Lepidosteus), Amphibia, and 

 some mammals. 



3. Botany. Preserved material of AJgae, Fnngi, Livei- 

 wortB, and Mosses. Price lists furnished on application to 



GEORQB M. QRAY, Curator, Woods Hole, Mass. 



PROVIDENT TEACHERS' AGENCY 

 120 Tremont Street BOSTON, MASS. 



We enroll and we recommend teachers and ofiBcera 

 for public and private schools, for normal and tech- 

 nical schools, and for colleges and universities. 

 Vacancies now for immediate service and for 1914- 

 15. Director, JAMES LEE LOVE, formerly of 

 Harvard Faculty. 



SECOND EDITION, REVISED AND ENLARGED 

 -Clean Water and How to Get It. 



Hazen- 



By Allen Hazen, Member of the American Society of Civil Engineers, etc. Small 8vo, xii+ 

 196 pages, containing 18 full-page half-tone illustrations. Cloth, $1.50 net. 



R ector — Underground Waters for Commercial Purposes. 



By Frank L. Rectoe, B.S., M.D., Bacteriologist, Great Bear Spring Company, New York, 

 Member American Public Health Association, American Microscopical Society, American 

 Chemical Society, American Association for the Advancement of Science, New England Water 

 AVorks Association. 12mo, vi-|-97 pages, illustrated. Cloth, $1.00 net. 



THIRD EDITION, REWRITTEN 



Prescott-Winslow — Elements of Water Bacteriology. 



With Special Reference to Sanitary Water Analysis. By Samuel Cate Peescott, Associate 

 Professor of Industrial Microbiology in the Massachusetts Institute of Technology, and 

 Chables-Edwaed Amoey Winslow, Associate Professor of Biology, College of the City of 

 New York, and Curator of Public Health, American Museum of Natural History, New York. 

 Small Svo, xii + 318 pages. Cloth, $1.75 net. 



THIRD EDITION, REWRITTEN 



Wiechmann — Sugar Analysis. 



For Cane-sugar and Beet-sugar Houses, Refineries and Experimental Stations, and as a Hand- 

 book of Instruction in Schools of Chemical Technology. By Feedinand G. Wiechmann, 

 Ph.D. Small Svo, xiii-f 307 pages. Illustrated. Cloth, $3.00 net. 



JOHN WILEY & SONS ''' ^ovRm AyB^vs 



London : CHAPMAN & HALL, Ltd. 



NEW YORK CITY 



Montreal, Can., RENQUF PUB. CO. 



