IV 



SCIENCE— ADVERTISEMENTS 



SCIENCE 



A Weekly Journal devoted to the Advancement of 

 Science, publishing the official notices and pro- 

 ceedings of the American Association for 

 the Advancement of ^cience 



Published every Friday by 



THE SCIENCE PRESS 



LANCASTER. PA. GARRISON, N. Y. 



New York City : Grand Central Terminal 



Entered in the post-office at I^ancaster, Pa., as second-class 

 matter, under the act of March 3, 1879 



TEACHERS WANTED 



AnSAssociate Professor in Physics, $2600; As- 

 sociate Professor of Biology, $2400; Professor of 

 Zoology and Geology, f2500; teacher of General 

 Science in High School, §2000; Assistant in Zo- 

 ology, $1800. 

 Th"? Interstate Teachers Agency, New Orleans, La. 



Marine Biological Laboratory 



WOODS HOLE, MASS. 



Biological Material 



1. Zoology. Preserred material of all types of animals for 

 class work and for the museum. 



2. Embryology. Stages of Borne invertehrates, fishes (in- 

 cluding Acanthias, Amia and Lepidosteus), Amphibia, and 

 Home mammals. 



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

 worts, Mosses, Ferns and Seed Plants. 



4. Microscope slides in Bacteriology, Botany and Zoology. 

 E. Life Histories, Germination Studies, and Natural His- 

 tory Groups. Catalogues famished on application to 



GEORGE M. GRAY, Curator 

 Woods Hole, Mass. 



The Microscope 



By SIMON H. GAGE of Cornell University 



13th Edition, Published December, 1920 

 In this edition, special emphasis is put upon the Dark-Field Microscope 



Postpaid S3.00 

 COMSTOCK PUBLISHING CO., Ithaca, N. Y. 



Electrical 

 Measuring Instruments 



for 

 Physicists and Physical Chemists 



Equipments suitable for research and industrial 

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Leeds & Northrup Co. 



Electrical Measuring Instruments 



4901 Stenton Ave. Philadelphia, Pa. 



Freas Constant Temperature 

 Laboratory Apparatus 



Freas Small Vacuum Oven, Type R.V. 

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 descriptive literature. 



Manufactured by 



The Thermo Electric Instrument Co. 



8 Johnson Street Newark, N. J. 

 We offer herewith 



Thermometers 



for immediate delivery 



Chemical Thermometers engraved on stem, each 

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110° C or equivalent F 



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200° " 



250° " 



300° ' ' 



360° " 



per doz. J9.00 

 10.00 

 11.00 

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 13.00 

 14.00 



Precision Thermometers, engraved on stem, 0-50° C 

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Ditto, with enclosed milkglass scale, 0-50° C in 1-5, 

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Beckman Thermometers, each . . . JlO.OO 



Other Thermometers and Hydrometers in all 

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We're Specialists in the manufacture of high-grade 

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Scientific Utilities Co., Inc. 



Manufacturers. Importers, Exporters 

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