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Apparatus for Magnetic Precision Measurements

The Fahy Permeameter

Compensated Type

Developed to meet the need for a reliable and convenient apparatus
for the magnetic testing of single specimens (bars, rods, sheet ma-
terial) and for the simultaneous comparison of two similar or dis-
similar specimens. Fully described in Scientific Paper No. 306 of
the U. S. Bureau of Standards.

The Fahy Permeameter

Simplex Type

Represents a further distinct advance in the art of magnetic measurements. Specially designed to test single specimens only-two or more specimens can be compared, of course, by the results of consecutive tests-it fully retains the high accuracy and perfect consistency of the compensated apparatus, but gains considerably in simplicity of operation and speed of tests.

The Magnet-Meter

An instrument developed for the precise and rapid investigation of shaped permanent magnets, such as used in magnetos, electrical measuring instruments, etc. This instrument serves to determine not only the initial strength, but also the stability of magnets.

Write for descriptive literature

HERMAN A. HOLZ

Apparatus of High Quality for Magnetic and
Metallurgical Testing and Research Work

Metropolitan Tower

NEW YORK

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WE SPECIALIZE IN

Graduated and Blown Glassware

Thermometers, Hydrometers

Coors and Guernsey Porcelain

Pyrex Glassware

All kinds Filter Paper, Hardware

Heavy Separatory Funnels and Kipps
Generators and Stains

Our 500-page catalogue sent upon request LENZ APPARATUS CO. Manufacturers-Dealers-Importers 18 East Sixteenth Street New York City, U. S. A.

Marine Biological Laboratory

Woods Hole, Mass.

INVESTIGATION

Entire Year

INSTRUCTION July 2 to August 12, 1919

SUPPLY DEPARTMENT Open the Entire Year

Facilities for reseach in Zoology. Embryology, Physiology and Botany. Seventy-six private laboratories, $100 each for not over three months. Thirty tables are available for beginners in research who desire to work under the direction of members of the staff. The fee for such a table is $50.00.

Courses of laboratory instruction with lectures are offered in Invertebrate Zoology, Protozoology. Embryology, Physiology and Morphology and Taxonomy of the Algae. Each course requires the full time of the student. Fee, $50. A lecture course on the Philosophical Aspects of Biology and Allied Sciences is also offered.

Animals and plants, preserved, living, and in embryonic stages. Preserved material of all types of animals and of Algae, Fungi, Liverworts and Mosses furnished for classwork, or for the museum. Living material furnished in season as ordered. Microscopic slidesin Zoology, Botany, Histology, Bacteriology. Price lists of Zoological and Botanical material and Microscopic Slides sent on application. State which is desired. For price lists and all information regarding material, address

GEO. M. GRAY, Curator, Woods Hole, Mass. The annual announcement will be sent on application to The Director, Marine Biological Laboratory, Woods Hole, Mass.

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Two NEW VOLUMES IN THE UNIVERSITY OF
CHICAGO PRESS SERIES

The Living Cycades

By CHARLES JOSEPH CHAMBERLAIN Professor of Botany in the University of Chicago

This study includes investigations extending over a period of fifteen years, that necessitated trips to Cuba, New Mexico, Australia, and Africa. The author studied all the genera and many of the species in the field, and preserved much material for later study in the laboratory. In addition to the data presented, the author gives an account of some of his experiences while on his tours of investigation.

186 pages, cloth; $1.50, postage extra
(weight 14 oz.)

Problems of Fertilization

By FRANK R. LILLIE

Professor of Embryology and Chairman of the
Department of Zoology in the University
of Chicago

A subject which has important bearings upon the problems of heredity and close relations to several fundamental biological problems. This volume is a popular presentation of the subject.

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Langmuir Condensation Pump

Dr. Irving Langmuir (of the General Electric Co.) has developed an exceedingly interesting and valuable high-speed high-vacuum pump, and by special agreement with the makers, we are acting as sole distributors, for laboratory purposes.

With this pump pressure as low as 10-5 bar have been obtained; and there is little doubt that very much lower pressures can be produced, by cooling the bulb to be exhausted, in liquid air, so as to decrease the rate at which gases escape from the walls. Some type of primary pump must be used; capable of developing a vacuum not less than 0.1-0.15 mm.of mercury.

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The illustration shows a Langmuir pump, connected to a two-stage primary oil pump which is operated by a HP motor; all three parts of the outfit being assembled together on one base.

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SERVICE

With the liquidation of the extensive Government Contracts, which we received during the war period from the Medical Departments of the U. S. Army and Navy, we now find ourselves in a position to offer our service in a prompt and unrestricted manner.

GUARANTEE

Our binding guarantee accompanies everyone of Haemacytometer complete with FLEI double chamber the FEI Blood Counting Apparatus and FE Blood Pipettes as well, that their accuracy conforms to the specifications established by the U. S. Bureau of Standards. Test Certificates are furnished upon request.

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Marked improvements have been accomplished in both method of manufacture and control of the degree of fineness of the mass in the Mandler Diatomaceous Filters. Several of the largest manufacturers of biologicals in the U. S. using these Filters in very large quantities now report them as distinctly superior to those previously imported.

27689. FILTER CYLINDERS, MANDLER DIATOMACEOUS, with metallic headpiece, fitted with lock nut, two rubber washers and one fibre washer as required for use in glass mantles, etc, on negative pressure. Where cylinders are used on positive pressure, the flat rubber washer and fibre washers are, of course, unnecessary. Size, inches.

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3.50
24

2 x

1x

3.00
72

2.50

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27678. FILTER CYLINDER, MANDLER DIATOMACEOUS, 10x2 inches, with glazed porcelain headpiece and nipple, for filtering acids, etc., Furnishe l in one size only.

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27679. FILTER CYLINDERS, MANDLER DIATOMACEOUS, with metallic headpiece with specially long nipple. Furnished with lock nut, two rubber washers and two fibre

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SCIENCE

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war.

THE BOTANICAL OPPORTUNITY1

WHEN this program was arranged, it was intended to bring to the attention of botanists how they could serve the nation in the crisis of Committees had been multiplied to do various kinds of necessary work. The results were not all that we had hoped for, but botan ists were beginning to find themselves, and organization was gradually becoming more effective, because the spirit of cooperation was developing. Enough results were obtained to prove that botany could be of great service at a time of national need. The practical results were not so conspicuous to the public in the immediate activities of the war as those of chemistry and physics for example, but they were fundamental and far-reaching, looking to future as well as to present needs. We must recognize that to bring into effective cooperation great numbers of isolated, scattered, and sometimes conflicting units, takes time and a great controlling motive. But we were making progress, not so rapid as the impatient desired, but probably as rapid as human nature permitted.

Now that the emergencies of war have passed, shall we stop this kind of progress? I wish to attempt to answer this question. In doing so, I shall not formulate any plan, any scheme of organization, but shall present in brief general statement what seems to me to be our opportunity. The other speakers upon the program will doubtless present more concrete suggestions, for which I hope my statement may be an appropriate background.

In connection with the period of reconstruction, there has come to the science of botany a great opportunity, and botanists must rise to the occasion. It is a critical time for our science, for we may lapse into our former state and become submerged by more aggressive

1 Invitation paper before the joint meeting of botanists at the Baltimore meeting of the American Association for the Advancement of Science.

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