SCIENCE-ADVERTISEMENTS 



Increased Factory Facilities 



Including the building and operation of the most ideal optical glass factory in America — 

 possibly the worid — one of the maryels of our great war program, 



ENABLES US TO PROMPTLY RESUME MANUFACTURE OF INSTRUMENTS 

 OF PEACE: 



MICROSCOPES MICROTOMES 



DELINEASCOPES SCIENTIFIC APPARATUS 



IN A LARGER AND MORE COMPLETE WAY THAN HERETOFORE 



It also permits the maturing of plans for the manufacture of 



Optical Measuring Instruments 



In which we expect to incorporate superior features, making them excel European models. 

 The first of these instruments which we expect to have ready will be an 



ABBE REFRACTOMETER 



Announcement of which will be made later. 



SPENCER LENS COMPANY 



BUFFALO, N. Y. 



THERESA SEESSEL RESEARCH 

 FELLOWSHIPS 



TO PROMOTE ORIGINAL RESEARCH IN 

 BIOLOGICAL STUDIES 



YALE UNIVERSITY 



TWO FELLOWSHIPS, yielding an income of $1,000 each, 

 open to men or women. Preference is given to candidates who 

 have already obtained their Doctorate, and have demonstrated 

 by their work fitness to carry on successfully original research 

 of a high order. The holder must reside in New Haven dur- 

 ing the college year, October to June. Applications should be 

 made to the Dean of the Graduate School, New Haven, Conn., 

 tiefore April 1, 1919; they should be accompanied by repiints 

 of scientific publications and letters of reconmiendation, and a 

 statement of the paiticiilar problem which the candidate ex- 

 pects to investigate. 



OPTIC PROJECTION 



Principles, installation and use of th« Mag'o Lantern, OpaquB 

 Lantern, Projection Microseope and Moving Picture Machinei 

 TOO pages, 400 figs. By SnioH Henbt Gaob. B.S., and 

 Hhmbt Phelps Gaob, PhJ>. Postpaid, S3.00. 



THE COMSTOCK PUBLISHING CO., Itiuica.N.Y. 



TEACHERS WANTED 



Men needed for college positions: — Physics, $2000; Biology. 

 $1600; Chemistry and Physics, $1700; Instructor in Physics 

 Jisoo; Assistant in Chemistry, $1500. Special terms. Address 



THE INTERSTATE TEACHERS' AGENCY 

 MACHBCA BUILDING NEW ORLEANS 



Proceedings of the Biological 

 Society of Washington 



Thirty-one Volumes Published, which contain 

 thousands of original descriptions of taxo- 

 nomic groups in Zoology and Botany and are 

 a necessity to systematic workers. 



If you want these valuable Proceedings, act 

 now, as only three complete sets are available 

 from the Society. Price for the 31 volumes in 

 original brochures, ^93.00. Annual Subscrip- 

 tion, ?3.oo. 



Bulletin of the Biological Society 

 of Washington 



One Volume published: A Sketch of The Nat- 

 ural History of the District of Columbia, 142 

 pages, 5 maps. 



Essential to libraries desiring complete 

 collections on general or local natural history, 

 on the geography or distribution of life in 

 Eastern United States, or on the Coastal Plain 

 and Pine Barrens. Price ^2.15 postpaid. 



BIOLOGICAL SOCIETY 



Biological Survey Washington, D. C. 



