SCIENCE-ADVERTISEMENTS 



Cramer's Precision Color=Filters 



FOR ALL PURPOSES 



Ibos and Visual Luminosity for landscape, portrait and telephoto work. 



Tricolor Filters for 3-color work. Contrast Filters for special color work. 



Micro-filters for Photomicrography and Spectroscopy. 



Our special booklets on " The Photography of Color Contrasts " 



and "Trichromatic Work" free to interested parties on request. 



Q. Cramer Dry Plate Company St. Louis, Mo. 



Theresa Seessel Research Fellowships to 



promote original Research in 



biological studies 



YALE UNIVERSITY 



Two fellowships yielding an income of $1,000 

 each. Preference is given to candidates who have 

 already obtained their Doctorate and have demon- 

 strated by their work fitness to carry on sncoessfnlly 

 original research work of a high order. Applications 

 should be made to the Dean of the Graduate School, 

 New Haven, Conn., before April 1st ; they should be 

 accompanied by reprints of scientific publications and 

 letters of recommendation. 



MARINE BIOLOQICAL LABORATORY 



WOODS HOLE, MASS. 

 biuiogical Materia] 



1. Zaolos:y. Preserved lasvcriLl of all types of anlmali 

 for claes work and for the rauseum. 



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

 eluding Acanttuas, Amla and Lepidosteus), Amphibia, and 

 gome mammals. 



3. Botany. Preserved material of Algae, Fungi. Uver- 

 irortg, and Mossei. Price lists furnlBhed on application to 



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



ELEVENTH EDITION 



THB A4ICROSCOPE, 



ftn introduction to Microscopic Metbods and to Histology, by 

 BiHoy Henry Gage of Cornell University. The 11th edition 

 has eight pages of new matter and corrections, otherwise it la 

 like the 10th ed. Price $2.00 postpaid. 



COMSTOCK PUBLISHING CO., Ithaca, N. Y, 



MAURER — Technical Mechanics. 



THIRD EDITION, REWRITTEN 

 By Edward R. Maurer, Professor of Mechanics in the University of Wisconsin. 

 6x9, vii+343 pages, 91 figures. Cloth, $2.50 net. 



KENT — Investigating an Industry. 



A Scientific Diagnosis of the Diseases of Management. By William Kent, Con- 

 sulting Engineer, and author of Kent's " Mechanical Engineers' Pocket-Book." 

 With an Introduction by Henry L. Gantt. 5x7J^, xi+126 pages. Cloth, $1.00 net. 



PICKELS- WILE Y— Text-Book on Railroad Surveying. 



By W. G. PiCKELS, Instructor in Civil Engineering, University of Illinois, and C. 

 C. Wiley, Instructor in Civil Engineering, University of Illinois. 43^x6^, ix+ 

 263 pages, 99 figures. Morocco, $2.50 net. 



WIECHMANN— 5agar Analysis. 



THIRD EDITION, REWRITTEN 



For Cane-sugar and Beet-sugar Houses, Refineries and Experimental Stations, and 

 as a Handbook of Instruction in Schools of Chemical Technology. By Ferdinand 

 G. WiECHMANN, Ph.D. 51^x8, xiii-1-307 pages, illustrated. Cloth, $3.00 net. 



JOHN WILEY & SONS ''' '"'''™ ^^n'eTvork ctv 



London: CHAPMAN & HALL, Ltd. Montreal, Can., RENOUF PUB. CO. 



