Xll 



SCIENCE-ADVERTISEMENTS 



Cramer's Precision Color=Filters 



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Ibos and Visual Ltuninosity 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" tree to interested parties on request. 



Q. Cramer Dry Plate Company 



St. Louis, Mo. 



Lantern Pictures 



of every sphere of ART, SCIENCE 

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Unger & Hoffmann, a.g. 



Dresden A. 77. GERMANY 



MARINE BIOLOQICAL LABORATORY 



WOODS HOLE, MASS. 



Biuio^caJ Material 



1. Zoologry. Preserved mavtritl of all types of animal! 

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2. Embryoloffy. Stages of some Invertebrates, fishes (ii^ 

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

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GEORQE M. GRAY, Curator, Woods Hole, Mass. 



ELEVENTH EDITION 



THE iVlICROSCORE, 



en introduction to Microscopic Methods and to Histology, by 

 Simon Hknky Gage of Cornell University. The llth edition 

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

 like the 10th ed. Price 82.00 postpaid. 

 COMSTOCK PUBLISHING CO., Ithaca, N. Vo 



Mathematical Monographs 



A Series of Volumes, each independent of the others, on topics in pure and 

 applied Mathematics 



Edited by Mansfield Mbeeiman and Egbert 8. Woodward 



6x9 inches. Cloth, $1.00 each 



The latest addition to this Series is No. 12, entitled 



The Theory of Relativity 



By Egbert D. Caemichael, Associate Professor of Mathematics, Indiana University. 



The following is an extract from a two column review which appeared in Science, 

 February 13, 1914 : 



" Unlike most presentations of the theory of relativity, which contain a consider- 

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 in the same way that the discussion of the foundation principles of geometry or mechanics 

 or chemistry might be made non-technical and logical. The book may, therefore, be 

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 or by the physicist who is unacquainted with mathematical analysis. ' ' 



Descriptive literature of this series upon request. Other volumes in preparation. 



JOHN WILEY & SONS ^'^ ''""'^™ ^^n'eTw ci.v 



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



