BECKMAN PHOTOELECTRIC

QUARTZ SPECTROPHOTOMETERAVAILABLE FOR IMMEDIATE SHIPMENT FROM OUR STOCKI~~~~~~~~~~~~~~~~~~~~~~

9101-A2.

QUARTZ SPECTROPHOTOMETER, Beckman Photoelectric. A self-contained unitwith which a wide variety of research and control work can be conducted with convenience,speed and precision. Consisting of quartz monochromator with light source, holder- forabsorption cells, twin phototubes and built-in electronic meter for translating phototubecurrents into direct readings of percentage transmission and density. See Gary and Beck-man, Journal of the Optical Society of America, Vol. 31, No. 11., (Nov., 1941), p. 682.

Wavelength scale approx. 100 cm long, readable and reproducible to 0.1 mmu in the ultraviolet andto 1.0 mmu in the infrared, with scale accuracy of 1 mmu. Built-in potentiometer and electronic amplifiermakes possible direct readings in percpntage transmission and density. Switch position "0.1" providesa ten-fold expansion of the transmission scale for mre accurate readings on solutions below 10% trans-mission.

The new model No. 2400 is provided with a liquid-cooled, cast metal lamp housing which takestungsten, hydrogen and mercury lamps mounted on self-aligning, interchangeable backplates. In addi-tion, a resistor box assembly (not shown in illustration), with three-position switch, is attached to thephototube compartment for rapid and convenient selection of proper phototube load resistor to regulatethe sensitivity for alternate use in transmission and flame photometry.9101-A2. Quartz Beckman Photoelectric, Model DU (No 2400), range 320 to 1000 mmu, as above de-

scribed,with volt tngsten lamp in liquid-cooled lamp housing with interchangeable backplate, one eachulte and caesium-oxide phototubes, resistor box assembly, matchei set of four square fusedCorex glass absorption cells for 10 mm liquid depth and 4-place holder. With dry cells for operating themeter but without 6-volt storage battery for operating the tungsten lamp and electronic tubes. 1Be0.00

9101-B2. Ditto, Model DUV, range 220 to 1000 mmu, identical with above but with the addition of ultraviolet accessoriesconsisting of one pasr of matched fused silica absorption cells for 10 mm liquid depth, hydrogen discharlamp on interchangeable backplate, and power supply unit, 115 volts, 50/60 cycles, a 0.. 1 575

More detailed information regarding above, and also Flame Photometer,Diffuse Reflectance and Fluorescence Attachments, and Test Tube CarrierAssembly, sent upon request.

We maintain a qualified technological staff for consultation,reoair and serv-icein connection with above and similarinstruments sold by us.

ARTHUR H. THOMAS COMPANYRETAIL-WHOLESAL'E-'EXPORT

LABORATORY APPARATUS'AND REAGENTSWEST WASHINGTON SQUARE PHILADELPHIA 5, PA., U. S. A.

Cable Address, "BALANCE," Philadelphia

November 30, 1951

IL il

PRINCIPLES OFPLANT PHYSIOLOGYby James Bonner and Arthur W. GalstonCalifornia Institute of Technology

NOTES ON A NEW BOOKEmphasizes principles and experiments basicto our understanding of the plant.... Inte-grated development of principles, fortifiedwith selective use of quantitative data. . . .

Simple, modern treatment of dynamic bio-chemical aspects of physiology... . Brief andconcise. . . . Beautiful illustrations clarifyphysiological processes.

To be published in January, Approx. 528 pp., Approx. 30 tables,Approx. 225 illus. by Evan Gillespie, $5.50

______ CONTENTS1. Plants and Plant Physiology. Part 1. NU-TRITION: 2. Photosynthesis; 3. Mineral Nu-trition; 4. Permeability and the Absorptionof Nutrients; 5. Water Economy; 6. The Soilas a Medium for Plant Growth; 7. Transloca-tion: The Redistribution of Nutrients. Part11. METABOLISM: 8. Enzymes: The Ma-chinery of Metabolism; 9. Carbohydrates: TheirNature, Functions, and Interrelations; 10. Res-piration and the Mechanism of Biological Oxi-dations; 11. Nitrogen: Its Metabolism andEconomy in Plant and Nature; 12. Lipids:Their Role in Structure and Function; 13.Highways and Byways in Plant Metabolism.Part 111. GROWTH AND DEVELOPMENT:14. The Dynamics of Growth and Develop-ment; 15. The Integration of Growth; 16.Auxin and the Control of Growth; 17. ThePhysiology of Reproduction; 18. Dormancyand Arrested Development; 19. The Problemof Differentiation; 20. Plant and Environment.

W. H. FREEMAN AND COMPANY !549 Market Street, San Francisco 5, California

November 30, 1951 'I'

KLETTELECTROPHORESIS

CUSTOM MADE

TOOL FOR THE ANALYSISOF COMPLEX COLLOID SYSTEMS, AND FORTHE CONTROL OF PRODUCTION OFPURIFIED PROTEINS, ENZYMES, HORMONES

KLETT MANUFACTURING CO.179 EAST 87TH STREETNEW YORK, N. Y.

November 30, 1951 I

For MEASUREMENI of SKIN RESISIANCE

* Gareean RECORDINGPSYCHOGALVANOMETER

4 For the study of thepsychogalvanic reflexand skin resistance.The instrument isdirect-reading and givesa written record of thereaction of the patient.Price . $775.00

GarceanCLINICAL DERMOHMETER

For clinical and experimen-tal investigation of disordersinvolving sympathetic reac-tion, such as pain reflexes.In the psychological labora-tory, the instrument has awell-known application as aso-called "'lie detector". Re-sistance is read directly froma calibrated dial. Small va-ations, greatly magnified, areshown on the meter. Batteryoperated. Price ....$115.00

ELECTRO-MEDICAL LABORATORY, INC.New Address-SOUTH WOODSTOCK 2, VERMONT, U.S.A.

Pioneer manufacturers of the electroencephalograph

Keep your copies of SCIENCE always available for quick,easy reference in this attractive, practical binder. Simplysnap the magazine in or out in a few seconds-no punch-ing or mutilating. It opens FLAT-for easy reference andreadability. Sturdily constructed-holds 26 issues.

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November 30, 1951

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-PERSONNEL PLACEMENT

IIIIgIIIIIIIIItztyzIIPOSITIONS WANTED |lllllllll]It}j(2Cellular Physiologist-Geneticist Ph.D., '48. National ResearchFellow '48-'49; currently Assistant Professor, full-time researchlarge University. Teaching experience; publications. Desires teach-ing-research position. September '52. Box 44, SCIENCE. X

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Pharmacologist. Broad academic and industrial experience. Nu-merous publications. Seeks change to another responsible position.Box 45, SCIENCE. X

Protein Chemist: 32, Ph.D. biochemistry 1946. Completing fourthyear of postgraduate work in analytical and reparative proteinchemistry, electrophoresis, ultracentrifuge, plasma fractionation.Graduate work: amino acids and enzymes. Independent research,several publications. Desires research position, teaching considered.Preferably northern parts of USA. Box 41, SCIENCE. 11/30

||||||||||||||||||||||||POSITIONS OPEN |||||||||lllllllllllBiochemist-Ph.D. with experience in basic research on inter-mediary metabolism. Background in enzymes and organic chemistryessential. Drug industry, Central New York State. Box 29, SCI-ENCE. 11/30

Positions Open:(a) Biochemist, Ph.D., to supervise clinical laboratories and de-velop more difficult diagnostic procedures; university medicalschool; South; minimum $6,000; percentage later. (b) Micro-biologist well qualified in biochemistry; research in carbohydratemold metabolism, fermentations, antibiotics and enzyme chemistry;small company; Midwest. (c) Graduate in one of biological sci-ences to develop bioassay procedures for pituitary hormones; ad-vantageous if qualified conduct hypophysectomies in laboratoryanimals; well known research institution; university medical cen-ter; $6000. (d) Pharmacologist to divide time directing researchdivision, pharmaceutical company and serving as professor phar-macology in medical college; Ph.D. or M.D.; competent admin-istrator with teaching ability required. (e) Pharmaceutical Chemistor Biochemist; new product department; laboratories specializingin allergy products; West. (f) Protein Chemist and Starch Chem-ist; straight research; industrial company; Midwest. S11-5 ScienceDivision, Medical Bureau (Burneice Larson, Director) PalmoliveBuilding, Chicago. X

SCIENTISTS-salaried positions, $3,600 to $25,000.This confidential service for outstanding men who desire a changeof connection, will develop and conduct preli ; negotiationswithout risk to present positien. Send name and addres for details.TOMSETT ASSOCIATES * 335 Frick Bldg., Pittsburgh 19, Pa.

||||||||||||||||1111111]11POSITIONS OPENI|||||||||||||||11|111Physicist to do research and development work on silicones andfluorinated polymers. Give education, personal data, photographsalary requirements in letter of application. The Connecticut HardRubber ompany, Attention: T , 407 East Street, New Haven,Connecticut. 12/7

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Must have experience in all phases of maaufacturing IF andRF coils and permability tuners. Electrical engiaeer orequivalent desired. Knowledge of methods and processig isessential. Unusual opportunities to grow in a new section ofan established highly regarded electronic manufacturing com-pany. Write Box 31.

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PROFESSIONAL SIM'WMS

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15

HOTEL RESERVATIONS

118th AAAS MEETINGPhiladelphia, December 26-31, 1951

The list of hotels and the reservation coupon below are for your convenience in making your hotelroom reservation in Philadelphia. Please send your application, not to any hotel directly, but to theAAAS Housing Bureau in Philadelphia and thereby avoid delay and confusion. The experienced HousingBureau will make assignments promptly; a confirmation will be sent vou in two weeks or less. Share a

room with a colleague if you wish to keep down expenses. Mail your application n.ow to secure your

first choice of desired accommodations.

HOTELS AND RATES PER DAYHotel* Single Double Twin-Bedded

ADELPHIA* $5.00-$6.00 $7.50-$10.50 $10.00-$12.50BARCLAY $ 8.00-$12.00BELLEVUE-STRATFORD* $4.50-$6.00 $8.00-$ 10.00 $ 9.00-$12.00BENJAMIN FRANKLIN* $5.00-$7.50 $8.00-$10.50 $11.00-$13.00DRAKE $6.00 $ 7.00 $ 9.00ESSEX $4.75-$5.00 $6.00-$ 8.50 $ 9.00-$10.00JOHN BARTRAM* $3.25-$4.50 $5.00-$ 8.00 $ 7.00-$ 9.00PENN SHERATON $5.00-$7.50 $7.50-$10.00 $ 8.00-$10.50RITZ-CARLTON* $7.00-$7.50 $1 1.00-$12.00ROBERT MORRIS $4.50-$5.00 $7.00-$ 8.00 $ 8.00ST. JAMES $4.00-$5.50 $6.00-$ 8.00 $ 6.50-$ 9.00SYLVANIA* $ 9.00-$11.00WARWICK * $ 9.00-$12.00

Cots added to a room are $2.50 each; dormitory style rooms (for 5 or more) are $3.50 per person.* Hotels starred have sessions in their public rooms. For a list of the headquarters of each participatingpease see Association Affairs, Science, August 24, or The Scientfic Monthly, September.

Suites$25.00-$35.00$14.00-$25.00$20.00-$30.00

$18.00$15.00

$12.00-$15.00

$18.00$22.00-$24.00

society and section,

* .--------- THIS IS YOUR HOTEL RESERVATION COUPON-. -AAAS Housing BureauArchitects Building (1st Floor) Date of Application ................

Philadelphia 3, Pa.Please reserve the following accommodations for the 118th Meeting of the AAAS:

TYPE OF ACCOMMODATION DESIRED

... Single Room (s)

. . . Double Room (s)

Desired Rate ......... Maximum Rate.

Desired Rate ......... Maximum Rate ......... Number in Party

... Twin-Bedded Room (s) Desired Rate ......... Maximum Rate.

... Suite (s) Desired Rate ......... Maximum Rate ......... Sharing this room will be:

........... (Enumerate persons here and attach list giving name and address of each person, including yourself)

CHOICE OF HOTEL

First Choice ................. Second Choice .... ...... Third Choice.

DATE OF ARRIVAL ... ....... DEPARTURE DATE .(These must be indicated)

NAME ........................ ............................................(Please print or type')

ADDRESS .......(Street) (City and Zone) (State)

Mail this now to the Housing Bureau. Rooms will be assigned and confirmed in order of receipt of reservation.

16 SCIENCE, Vol. 11.4

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- qhlantern slides. The new Lqb-aid transparency file~~~~has 40 smooth-sliding -fiat trays, each holding 16standard 2" mounts, or 5 31/41 x 41/4" lanternslides in full view. They're easy to insert . .you just drop them flat in the grooved frames.Easy to remove, too, by popping them out fromunderneath.

The special cabinet with its pull-out illuminatordrawer lets you view a whole tray of transpar-encies at a glance, without removing any of them.Sitting or standing, you can inspect hundreds ofslides under ideal viewing conditions without stir-ring from your place. And the disappearing shelfis a mighty handy place to lay slides down tem-porarily while you're working with them.

Both tray and illuminator cabinets are of thesame dimensions and finish as all the other units

a in the Technicon Laboratory Filing System, andansparency Tray Cabi- can be stacked interchangeably with them, If youits, with the illuminatorkbinet drawer pulled out. _ would like more information about these or otherse the table base, or units of the system, we'll be glad to send details.task them with yourresent Lab-aid Files. *

The disappearing shelf is sovenient as a temporary restingplace for slides while working Inspect all your slides without re-with them. moving any of them, or even stir_

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