u 



SCIENCE-ADVERTISEMENTS 



MARINE BIOLOGICAL LABORATORY 



WOODS HOLE, MASS. 



Biological Material 



1. Zooiosry. Preserred material of all types of animals 

 for class work and for the museum. 



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

 cluding Acanthias, Amia and Lepidosteus), Amphibia, and 

 BOme mammals. 



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

 worts and Mosses. Price lists furnished on application to 

 GSOEGE M. GRAT, Curator, Woods Hole, Mass, 



ROMEIKE'S 



PRESS CLIPPINGS 



are now an absolute necessity for every scientific 

 naan. By methodical searching through the most 

 important papers and periodicals published in this 

 country and abroad we are able to supply you at 

 short notice with information on any subject which 

 perhaps you would be unable to find yourself in 

 libraries or reference books after spending days or 

 even weeks at such a task. Write for further infor- 

 mation. 



HENRY ROMEIKE, Inc. 



106-110 Seventh Avenue New York City 



JULIEN'S POWER LATHES 



COMPACT— ACCURATE— DURABLE 



Uao ot Geologists, Mineralogists, etc, in SLICING 



and POLISHING all hard substanoes, rooks, ets., and 



in preparation of MICROSCOPIC THIN SECTIONS. 



GUSTAVUS D. JULIEN 



3 Webster Terrace NEW ROCHEIXE, N. Y. 



Memoirs «f the Wistar Institute of Anatomy and 

 Btology. No. 6, 1915 



THE RAT 



Data and Reference TaL>Ies. 278 Pages. 89 Tables. 



Bibliography. 

 Compiled and Edited by HENRY H. DONALDSON. 



Postpaid $3.00. 



The Wistar Institute 



Philadelphia, Pa. 



OPTIC PROJECTION 



Principles, installation and uso of the Mag"c Lantern, Opaque 

 Lantern, Projection Microscope and Moving Picture Machine; 

 700 pages, 400 figs. By Simon Henht Gage,, B.S., and 

 Henbt Phelps Gage. Ph.D. Postpaid, $3.00. 

 THE COMSTOCK PUBUSHING CO., Ithaca, N.Y. 



The Ellen Richards Research Prize 



The Naples Table Association for Promoting 

 Laboratory Research by Women announces the offer 

 of a research prize of $1000.00 for the best thesis 

 >VTitten by an American woman embodying new ob- 

 servations and new conclusions based on independent 

 laboratory research in Biology (including Psy- 

 chology), Chemistry or Physics. Papers published 

 before 1916 will not be considered and theses pre- 

 sented for a Ph.D. degree are not ehgible. Theses 

 offered in competition must be in the hands of the 

 Chairman of the Committee on the Prize before 

 February 25, 1918. Application blanks may be ob- 

 tained from the secretary, Mrs. Ada Wing Mead, 

 823 Wayland Avenue, Providence, R. I. 



El 



In the Brooks' Inductometer is offered 

 a compact form of variable inductance, 

 with a self inductfince range of 5 to 50 milli- 

 henrys, possessing the following advan- 

 tages: 



1. A fair degree of astaticism, which 

 tends to eliminate errors due to stray 

 field effects. 



2. It is less expensive and at the 

 same time fuUy as accurate as the Ayrton- 

 Perry instrument. 



3. It occupies less space than the 

 Aryton-Peiry form. 



The instrument has a very nearly uniform scale, obtained by properly proportioning the coils. 



It may be used as a mutual inductance. 



It has a good ratio of maximum to minimum inductance (about 9 to 1) and also has as high 

 a time constant as is consistent with good design and moderate size. 



The instrument is fully described in Bulletin No. 152, a copy of which wiU be sent upon request. 



ELECTRICAL MEASURING INSTRUMENTS 



4921 STENTON AVENUE 



PHILADELPHIA 



