SCIENCE-ADVERTISEMENTS 



Our Laboratory Spectrometers 



are sold in competition 

 with instruments of 

 European make to many 

 of the best laboratorieB 

 throughout the world. 



Spectrometer 

 L4020— $80.00. 



A New Student's 



Spectrometer 



L 4022 



Send for Catalog and further details. 



WM. GAERTNER & CO. 



Physical and Astronomical Instruments 



S34S-49 Lake Ave. CHICAGO 



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 Ferdinand G. Wiechmann, 

 Ph.D. Third Edition, Rewritten. Small 8vo. 

 xiii+307 pages. Illustrated. Cloth, $3.00 net. 



MACINTIBE — Mechanical Refrigera- 

 tion. A Treatise for Technical Students and 

 Engineers. By H. J. Macintire, M.M.E., 

 Member Am. Soc. M.E., Member Am. Soc. 

 Refrig. Eng., Assistant Professor of Mechan- 

 ical Engineering, University of Washington. 

 8vo, ix+346 pages, 121 figures, including 10 

 folding plates in text. Cloth, $4.00 net. 



CLEWELL—l,aboratory Manual, Direct 

 and Alternating Current. By Clar- 

 ence E. Clbwell, Sheffield Scientific School 

 of Yale University. 8vo, 100 pages, 41 Illus- 

 trations. Cloth, $1.00 net. 



HOWE — Symmetrical Masonry Arches. 



Including Natural Stone, Plain-Concrete, and 

 Reinforced-Concrete Arches. For the use of 

 Technical Schools, Engineers, and Computers 

 in Designing Arches According to the Elastic 

 Theory. By Malvehd A. Howe, M. Am. 

 Soc. C.E., Professor of Civil Engineering, 

 Rose Polytechnic Institute. Second Edition, 

 Revised and Enlarged. 8vo, xxiv-|- 245 pages, 

 6 plates. Cloth, $2.50 net. 



JOHN WILEV & SONS, Inc., 



SCIENTIFIC PUBLICATIONS 



432 Fourth Avenue, New York City 



London : 

 CHAPHAN & HALL, Limited 



Montreal, Can.: 

 RENOUF PUBLISHING CO. 



