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The Silverman Illuminator

A new eye for the microscope Offers important advantages for practically every application of the Microscope It shows more detail. Ö-A clearer and better defined picture is presented to the eye and the camera.

ra. I woH c-Several novel methods of illumination can be produced. d-It saves very much valuable time. e-It prevents eye strain, eye fatigue, and brain fag. s-It can be lowered in to deep. hollow places. -It gives excellent results for very low power work as well as higher magnifi

cations, also in oil immersion work. A It can be used with any Microscope, ordinary or binocular.

A small circular tube lamp surrounds the objective and furnishes a diffused and uniform illumination directly where it is needed. The Silverman Illumi. nator marks

A Great Advance in Microscope Illumination

For sale by all the better dealers

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By AUSTIN M. PATTERSON, Ph. D.

Formerly Editor of Chemical Abstracts"
Author of “A GERMAN-ENGLISH DICTIONARY FOR CHEMISTS

This useful new Dictionary defines over 30,000 words and phrases. It is the only book covering its particular field, and follows the lines of the same author's very successful German-English Dictionary. The entire chemical field is covered, and in addition common general words and many troublesome idioms and verb forms are included.

The Introduction contains information on French chemical nomenclature and gives a few principles of grammar and examples of the plurals of nouns, declension of verbs, ete.

This book has 384 pages, 5 by 7, and is flexibly bound. $3.00 postpaid.

Let us send YOU a Free Examination copy-
determine for yourself just how valuable it is

JOHN WILEY & SONS, Inc.

432 Fourth Avenue

NEW YORK

NEW SERIES
Vol. LIII, No. 1374

FRIDAY, APRIL 29, 1991

SINGLE COPIES, 15 Cts.
ANNUAL SUBSCRIPTION, $6.00

RECENTLY ISSUED

Cault
* Leland Stanford, Jr., Unlv.,

Stanford Univ..
Guido H. Marx,

Smith's Bacterial Diseases Plants
* There are many unique features about this book.

irst treatise
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ject. The style is easy and tremendously interesting. aggestions
given throughout are practicable they have been thorouxnly tried and
the hints on the details of technic will prove serviceable. The book is
adaptable to the use of either the graduate or the undergraduate student."
-L. R. Hesler in "Phytopathology."
By ERWIN F. Smith, in charge of Laboratory of Plant Pathology, Bureau of Plant Industry, Washington,
D. C. Octavo of 600 pages, illustrated.

Cloth, $10.00 net.

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Prentiss and Arey's Embryology

Third

Edition
This edition has been given a thorough and careful revision, adding every
new advancement. It deals particularly with the chick and pig embryos
usually studied in the laboratory, comparing them constantly with the
human embryo and giving you a concise, systematic account of human
embryology. A large number of original dissections are described and
illustrated.
Large octavo of 411 pages, with 388 illustrations By CHARLES W. PRENTISS, Ph.D., formerly Professor of
Microscopic Anatomy, and LESLIE B. AREY, Ph.D., Associate Professor of Anatomy, Northwestern University.

Cloth, $5.50 net.

Seventh
Mallory and Wright's Pathologic Technic

Edition
This work gives the technic of bacteriologic methods, bacteriology of
various diseases, histologic methods, the special methods used in clinical
bacteriology and pathology, and the preparation of bacterial vaccines.
Octavo of 555 pages, with 181 illustrations. By FRANK BURR MALLORY, M.D., Pathologist to

he Boston City Hospital; and JAMÉS HOMER WRIGHT, M.D., Pathologist to the Massachusetts General Hospital.

Cloth, $4.75 net.

Sign and Mail this Order Form Today
W. B. SAUNDERS COMPANY,West Washington Sq., Phila.
Please send me the books marked (X), charging the amount to my account:
Smith's Bacterial Diseases of Plants.

Cloth, $10.00 net
Prentiss and Arey's Embryology

Cloth, $5.50 net
Mallory and Wright's Pathologic Technic . . Cloth, $4.75 net
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Pyrolectric Instrument Co.

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When you purchase Leeds & Northrup resistance apparatus for your laboratory you do so with the manufacturer's guarantee that all the precautions in manufacture, which long experience has shown essential, are carefully observed. You are further assured that the instrument, whatever it may be, is as accurate as the specifications have stated it to be, and that its design is in accordance with the best practice, consistent with reasonable cost.

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SCIENCE

Experimental Organic

Chemistry

NEW-WORLD SCIENCE SERIES

edited by John W. Ritchie A Weekly Journal devoted to the Advancement of Science, publishing the official notices and proceedings of the American Association for

the Advancement of Science

Published every Friday by
THE SCIENCE PRESS
LANCASTER, PA.
GARRISON, N. Y.

By AUGUSTUS P. WEST
NEW YORK, N. Y.

University of the Philippines
Entered in the post-office at Lancaster, Pa as second-class
matter, under the act of March 3, 1879

A text containing full laboratory direcWANTED_Two graduates in Zoology, Physiology or

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Structural formulas and equations show

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number of charts and diagrams make Weather Bureau A rational and deductive treatise on the physics of clear the interrelation of compounds. As the atmosphere. Of great value to meteorologists,

a laboratory guide and text to accompany physicists and the aviator. 678 Pages, Illustrated, Index, 8vo. Price, $5

lectures this book fills a real need. Address orders and inquiries to THE FRANKLIN INSTITUTE

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Chapters devoted to near relatives of Coccids, Preparation, External Anatomy, Classification, and to each put it into use in my classes." of the Subfamilies and Tribes, Twenty-seven in all. 8mo. Cloth. IX+502. $6.00 net.

Cloth. xiï + 469 pages. Illustrated. Sent prepaid upon receipt of price. Order direct from publisher

SCARAB COMPANY 603 Michigan Ave. Urbana, Illinois

Price $3.20.

The Physics of the Air

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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 $3.00
COMSTOCK PUBLISHING CO, Ithaca, N. Y.

WORLD BOOK COMPANY

Yonkers-on-Hudson, N. Y. 2126 Prairie Avenue, Chicago

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