Announcing the appointment of

as the official suppliers of back copies ofTHE SCIENTIFIC MONTHLY AND SCIENCE

The American Association for the Advancement of Science has com-pleted arrangements with Stechert-Hafner, Inc. (formerly G. E. Stechert& Co.), the international book and periodical suppliers, to handle allback copy sales of its publications, THE SCIENTIFIC MONTHLY andSCIENCE, effective May i, i947. Stechert-Hafner will warehouse andship from New York all back copies of the magazines (other than the.current year's issues) and will supply service for such copies through itsworld-wide distribution facilities.

The Circulation Department of the Publications Division, A.A.A.S.,.will continue to handle all correspondence and adjustments with respectto subscription copies. It will also handle single copy sales for thecurrent calendar year issues. Stechert-Hafner will continue to act as anagent for receiving sukscriptions in the same manner as it has in the past.

The following prices have been established for back issues of themagazines:

SCIENCEAll issues after January I, I946............... .. ¢per copyAll issues prior to I946............... X5 Plus 5 per copy,

per year.SCIENTIFIC MONTHLY

All issues after January I, I947.............. 6o0 per copyAll issues prior to I947.............. 75 per copy

Orders should be sent with correct remittance to:

Periodical Department

Stechert-Hafner, Inc.31 East Tenth Street New York 3, N. Y.

9

1W ww

i* ~~~for 25, 3 X 1"SLIDES

This BAKELITE BOX is compactly built for filing of 3 x 1" SLIDES-for storing

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value to those who find space at a premium. Practical for loan collections.

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* Compact Size 313" x 3-" x 15" to hold 25, 3 x 1" slides. Can be stored in minimumamount of space.

* Snap Fit Closure seals out dirt and dust.

* Index Card Permits recording titles of 25 slides corresponding to numbered slots. Num-bers are white for visibility. (See illustration)

* Attractive Black Bakelite-durable, accurate slotting, nice to handle.

Catalogue No. A-1604/BEach $.45 Dozen $5.00

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CLAY-ADAMS

10

New Wiley Books

CHEMICAL PROCESS PRINCIPLES-Part l-ThermodynamicsBy 0. A. HOUGEN and K. M. WATSON, Professors of Chemical Engineering, University ofWisconsin.

THERMODYNAMICS is a comprehensive and advanced but easily understood treatment of thethermodynamic problems of the process industries. It is suitable for use as a textbook in chemicaland chemical engineering thermodynamics courses at both the undergraduate and graduate levels.The text is organized so that the more advanced sections can be readily omitted from undergraduatecourses.

Ready in June. Approximately 380 pages. 5% by 8% Probable price $5.00.

CHEMICAL PROCESS PRINCIPLES-Part Ill-Kineticsand Catalysis

By 0. A. HOUGEN and K. M. WATSON.

KINETICS AND CATALYSIS is a study of chemical kinetics applied to reactor design for nearly alltypes of reactions, homogeneous, heterogeneous, and catalytic. It provides fundamental trainingfor both undergraduate and graduate students in applied chemical kinetics.

Ready in July. Approximately 310 pages. 5% by 8%. Probable price $4.50.

VEGETABLE GROWINGBy J. S. SHOEMAKER, Professor of Horticulture and Head of the Department of Horticulture,Ontario Agricultural College.

A logical treatise which applied research findings to successful vegetable growing. Includes athorough discussion of the production of high quality vegetable seed as basic to good crops. Makesclear the causes of various frequently misunderstood adverse effects in cultural practices. Thisthorough textbook is complete with material directly applicable to vegetable growing under variousconditions over a wide range of territory.

Ready in May. Approximately 506 pages. 5% by 8½. Probable price $4.50.

IGNEOUS MINERALS AND ROCKSBy ERNEST E. WAHLSTROM, Associate Professor of Geology, University of Colorado.

An authoritative and accurate summary of principles, this book combines features which will permitmicroscopic indentification of minerals in igneous rocks and, also, the classification of rocks accordingto a semi-quantitative scheme. Presents such topics as: description of igneous rocks, their chemicaland mineral composition and classification, structure, texture, color, alterations, and geologicaloccurrence.

Ready in May. Approximately 367 pages. 5½ by 8½. Probable price $5.00.

SEQUENTIAL ANALYSISBy ABRAHAM WALD, Professor of Mathematical Statistics, Columbia University.

The first book-length treatment of an important new statistical technique. Called the SequentialProbability Ratio Test, this modern method has many proven advantages over other procedures fortesting a statistical hypothesis. It was developed by the author and was used extensively duringthe war in development work on military and naval equipment. The book is part of the WILEYMATHEMATICAL STATISTICS SERIES edited by Walter A. Shewhart.

Ready in May. Approximately 225 pages. 6 by 9V4. Probable price $4.00.

John Wiley & Sons, Inc., 440-4th Ave., New York 16, N. Y.

11

---Mm---

BARGAiNS~-WAR SURPLUS LENSES & PRISMSASSEMBLE YOUR OWN BINOCULARS!

Complete Optics! Complete Metal Parts!Save More Than M Regular Cost

ARMY'S 7 X 50BINOCULARS

Hre's an unusualopportunity to se-cure a fine set ofBinoculars at a sub-stantial saving ofmoney. Offeedhere are completesets of Optics andMetal Parts for theArmy's M-16 7 x 50Binoculars (M-16 isnot the waterproofmodel). Thescomponents are newand all ready forassembly. We sup-ply full instructions.Limit-1 set ofMetal Parts and 1set of Optics to acustomer.

METAL PARTS-Set includes all Metal Parts-completely finished-for assembly of 7 x 60 Binoculars. No machining required. Bodieshave been factory hinged and covered. A sturdy Binocular CarryingCam is included with each set of Metal Parts.Stock 5624-W......... 7 x 50 Metal Par............$35.50 PostpaidOPTICS-Set includes all Lenses and Prisms you need for ambling7 x 50 Binoculars. Thes Optics are in excellent condition-perfect orner perfect-and have new low reflection omating.Stock S5102-W......... 7 x 50 Optics..............$25.01PostpaidNOTICE! If ou buy both the Binocular Optice and the Binocular MetalParts your purchae becomes subject to *0% Fedel Excise Tax. Be sureto ;dd amount covering tax to your remittance or vour order cannot be Ailed.

ARMY'S 6 X 30 BINOCULARSNo Crng Cas with any Sets shown below. (None yet available inSurplus Market.) M-13A1 sets we waterproof model. M-3 ets are notwaterproof. Limit-i Bet to a Customer on all Set shown below.

COMPLETE OPTICS & METAL PARTS-Model M-13A1 6 x 311Binocular. Everything you need-edy for assembly. Whenffinihed will look like a regular factory job costing $102 to $120. TheOptis are new, in peat or near-perfect condition. Have new lowreflection coat Part are new and perfect all completely fin-lehed. No~maingo required. Bodies factory hinged and covered.Complete membl instructions included.Stock 5S0-W . .$40.0 Postpaid,

plus $8.0 tax-Total-$48.90COMPLETE OPTICS & METAL PARTS-Model M-3, 6 30 Binocu-las. The Optics in this set are new, perfect or near-perfect. Primshave new low refliction coating. Factory mounted Eye Piece and Ob-jective Assemblies not coated. Metal Parts are perfect, new, ready forssembly. When finished, this will look like a regular factory job, excepta name nas been filed off a cover plate. No machining required. Bodissfactory hinged and covered.Stock *831-W .......................................$ 35.00Postpaid,

plus $7.0 tax-Total-$42.90METAL PARTS ONLY-Model M-13A1. 6 x 30 Binoculars. NoOptics. Same Metal Parts as described for Stock S830-W.Stock 5832-W.......... 6 x 30 Metal Parts ..... $25.0 PostpaidMETAL PARTS ONLY-Model M-3. 6 x 30 Binoculars. No Optics.some machig on these Metal Parts required. Bodies hingedandPrism Shelf hole placed but you must tap them. Prism Shelves havebeen m hind. Six lea spiral focusing threads have been cut. Someless difficult components you must thread and machine yourself, but allmaterial you need is furnished except body covering material and Optics.Stock Y833-W.........6 x 30 Metal Parts .$12.00 PostpaidOPTICS FOR 6 x 360 Binoculars (No Metal Parts.) Slight seconds.Cemented but not coated.Stock *5123-W . . $10.00 Postpaid

ORDER BY SET OR STOCK NO. 4

All Items Finis Ground and Polished but Some Edge. Slightly Chipped orOther Slight Imperlction. Which We Guarantee Will Not Interfere WithTheir Use. Come Neatly Packed and Marked.

TO KEEP PO'SI)E on all our near Optical Items, send 10 andyour name and addrss to get on our re~ "Flah" mailing list.

(Army's 6 x 360 Binoculars - Cont'd.)SAME OPTICS AS ABOVE (6 x 30), but coated.Stock %5124-W.................................... 12.75 PostpaidIfyou buy both the Binocular Optics and the Binocular Metal Park, yourpurchase become. subject to 20% Federal Excise Tax. Be sure to addamount cosering tax to your remittance or your order cannot be filed.Optics and Metal Parts are Available for Monoculars (%a Binocu-lar). For Complete Details, Write for Bulletin S 14-W.MOUNTED PROJECTING LENS SYSTEM. F.L. 91.44 mm. (justright for 35 mm. Projectors). Speed of F 1.9. Outside dia. of mountat one end 60 mm. Length of mount 64 mm.Stock ft4433-W .................................... $3.09 PostpaidMOUNT FOR ABOVE PROJECTING LENS SYSTEMStocks *715-W .................................... $1.50 PostpaidSCHMIDT OPTICAL SYSTEM. Black plastic body size 3%' by51'. F.L. 2.4`.. with amazing speed of F.O.9. Tased in Navy'sInfra-Red Sniperscope and Signalling Units. Govt. cost $134. Limit-1 toWa customer.Stock *720-W...............................$........... 6.01 Postpaid23 POWER PRISM SPOTTING TELESCOPE SET-Optics consistof perfect Achromatic Objective with dia. of 64 mm. and 20 inch F.L.(not a War Surplus item), an Eye Achromat, Field Lens and Prisms from6 x 30 Binocular. These are slight seconds. All low reflection coatedexcept Objective. Half a covered 6 x 30 Binocular Body, all parts forEye-Piece end and Prism Shelf section are supplied. You must furnishan extension tube and any parts needed to mount the Objective Lens.Stock #5127-W ............................... $21.0 PostpaidPOLARIZING VARIABLE DENSITY ATTACHMENT for 7 x 50Binoculars. An amazingly effective unit for controlling amount of lightreaching your eye. Cuts down glare in sky and overwater observations.Easily snap on and off over he, eye cups of American-made 7 x 50Binoculars. Govt. cost $8.30 each.Stock 526,0-W............................... $2.00 Postpaid2H' DIA. ACHROMATIC TELESCOPE OBJECTIVE-F.L. 20 inches.(Not a war surplus item.) The Govt. used ve*r few long focus ObjectiveLeAs so we had these made for you. First clam lens suitable for Spot-ting Scopes, Terrestrial Telescopes, etc. Not coated.Stock 5 6197-W............................... $10.50 PostpaidAIR FORCES GUN SIGHT-With Polarizing Variable DensityAttachment. Can be used as Slide Viewer, or take it apartand you canget Polarizing Variable Density Attachment. Mangin Coneave Mirror,Rfector Plate, Metal Reticle Window, Lamp Housing, Ring and BeadSight. The Polarizing attachment alone in worth many times the prof entire unit. Consists of 2 Polarizing Filters mounted with small handlewhich rotates one around the other. May be used in Photography, Re.search, Experiments, as Light Dimmer. etc.Stock 59S-W.................................$5.0 11Postpaid

Same Unit Without Polarizing AttachmentStock S916-W ................................ 2.560 PotPaidSPECTROSCOPE SETS ... These sets contain all Lenses and Prismsyou nesd to make a Spectroscope plus FREE 15-pages InstructionBooklet.Stock *15506W-Hand Type...........................$ 3.45 PostpaidStock S 1501-W-Laboratory Type....................$ 6.50 PostpaidBOMBER SIGHTING STATION-A double end Periscope TyrpeInstrument of highest preciion. Brand new and in perfect condition.6 ft. tall, shipping wt. 360 lbs. Orig. cost $9,850. Consists of numerousLensess, G Motors, Metal Parts and ElectricalGadgets.Stock 5914-W...............................$ 50.50 F.O.B. OklahomaBATTERY COMMANDER'S PERISCOPE With Tripod-6 PowerInstrument. Excellent condition. Length 27% inches, diam. 1%inches. Cost UI. S3. Govt. approximately $175.00.Stock %717-W................................ 520.00 F.O.B. AudubonWE HAVE LITERALLY MILLIONS OF WAR SURPLUS LENSESAND PRISMS FOR SALE AT BARGAIN PRICES. WRITE FORCATALOG "W"-SENT FREE!

TANK PRISMS-PLAIN OR SILVERED90-45-46 deg. 5%'a long, 2W' wide, finely ground and polished.Stock #3504-W-Silvered Prism (Perfect).$2.5 PostpaidStock #3005-W-Plain Prim (Perfect) .................$2.00 PostpaidStock 03100-W-Silvered Prism (Second)...............$1.00 PostpaidStock 03101-W-Plain Prism (Second) ................ $1.00 Postpaid

(Illustrated Book on Prisms included FREE)

SATISFACTION'rGUARANTEED

EDMUND SALVAGE COMPANY, P. 0. Audubon, New Jersey12

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EDUCATION

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TRACERLABD INC.55 OLIVER STREET, BOSTON 10,MASS.

WRITE FOR BULLETIN DESCRIBINGTHE TRACERLAB AUTOSCALERFOR RADIOACTIVITY MEASUREMENTS

MONTHLY PUBLICATION traceriogSENT FREE UPON REQUEST OIL PROSPECTING

13

1

BIOLOGICAL TEST DIETS

Vitamin Test CaseinVitamin A Test Diet U.S.P. XIIVitamin B-Complex Test Diet

Rachitogenic Diet No.2 U.S.P. XIIOther GBI Diet Materials

Salt Mixture No. 2 U.S.P. XIIBrewers Yeast Powder

Casein Hydrolysate PowderLactalbumen Hydrolysate Powder

Vitamins and Amino AcidsWrit* for Booklet 677 describing these andother special products for nutritional research.

CHAGRIN FALLS# OHIO

write for thisGBI BookletNo. 667

which lists a widerange of ready-to-useproducts for nutritional

investigators.

TABLE OF CONTENTS

Vitamin rest Casein, Vitamin-Free Casein Hydrolysate, Salt MixtureNo. 2-U. S. P. XiI, Vitamin A Test Diet-U. S. P. XII, RachitogenicDiet No. 2-U. S. P. XIi, Vitamin B Complex Test Diet, Biotin, YeastSupplement Solution, Choline Chloride, Basal Medium Stock Solution,Crystalline Vitamins, Amino Acids, Misc. Research Biochemicals.

GBI products, suitably packaged and economi-cally priced, are offered as a special service tonutritional investigators for biological and micro-biological procedures. They will save time,trouble, and expense in your laboratory.

GENERAL BIOCREMICALSINCORPORATED

60 LABORATORY PARK CHAGRIN FALLS. OHIO

IMMEDIATE DELIVERYColeman pH Electrometer

The Coleman pH electrometer is a ruggedly constructed,precision instrument designed with particular attentionto simplicity and practicability in operation. Eachmeter is a complete self-contained unit, consisting ofglass and reference electrodes, batteries, sample cup andreference solution all housed in a solid walnut cabinet.Complete operation instructions are supplied with eachinstrument and are conveniently located in the cover ofthe case.These electrometers consist of an electronic amplifier,

precision potentiometer, Weston type standard cell andutilize the well-known Coleman impulse amplifier circuitwhich prevents changes in tube characteristics influenc-ing the precision of the instrument readings. All partsare firmly mounted within the cabinet. Tubes and bat-teries are cushioned by sponge rubber.S-6542ELECTROMETER, Coleman, Model3ApH Scale.This instrument is intended for general laboratory andplant work where extremes of temperatures are not en-countered and where oxidation reduction tests are notmade. The scale is graduated from 0 to 13 pH in .05pH subdivisions and may be read by interpolation to .01pH. The electrical accuracy is .1% and the electro-chemical accuracy .05 pH. This rated accuracy is atroom temperature but can be extended over higher orlower temperatures by using tables supplied with theinstrument. Complete with sealed glass and referenceelectrodes, tubes, batteries, KCl solution, buffer tablets,etc., but without redox electrode. Each 180.00S-6548 ELECTROMETER, Coleman, Model 3D, pH andMillivolt Scales, Redox Electrode and TemperatureCompensator. This instrument is like No. 6542 buthas a scale-changing switch for reading millivolts as wellas pH, an automatic temperature compensator, and aredox electrode for oxidation-reduction determinationsand for determining pH with quinhydrone electrodes.The scale is graduated 0 to 1300 millivolts in 10-millivoltsubdivisions and 0 to 13 pH in .1 pH subdivisions. Bothscales are easily read, and are accurate to 2 millivoltsor .02 pH. The automatic temperature compensatorinsures accurate pH results over a temperature range of0 to 50WC. Supplied complete with sealed glass andreference electrodes, gold redox electrode, KCl solution,buffer tablets, tubes, batteries, etc. Each 235.00

STANDARD SCIENTIFIC. SUPPLY CORP.34 WEST 4TH STREET NEW YORK 12, N. Y.

60 LABORATORY PARK

14

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Ifthe Federal Model 40 is not avail-able through your regular supplierof scientific equipment, write to 'Federal giving us his name.

Attractive Meoal CarryingCose Available $8.50

S 4 **0c4

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gA

15

Is this the scientistyou need for your staff?

Bacteriologist. Minor plant pathology, PhD in June. De-sires teaching position in small college with opportunity for re-search, or research position. College teaching, other experi-ence. Box 843, SCIENCE.

If you have staff vacancies readPERSONNEL PLACEMENT regularlyeach week.* Well-trained and re-sourceful scientists seeking profes-sional advancement announce theiravailability each week. If your needis immediate a notice in PERSONNELPLACEMENT will bring quick resultsat a low cost.

* See Science this issue, page 18.

p-New Reinhold Books I~~~~~~~~~~~~~~~~~~~~INJECTION MOLDING OF PLASTICS

By ISLYN THOMAS, President, Thomas Mansfacturing Corp., Newark, N. J.REINHOLD PLASTICS SERIES

A detailed, specific and thoroughly practical coverage of the history, development, and mechanical problems in-volved in injection molding, written from the point of view of shop practice. The book contains 450 illustrations(inluding five color plates), most of which deal with the mechanical details of presses, mold design and operat-ing techniques. Everything of any importance regarding injection molding is recorded, and up-to-date methodsof designing, machining and utilizing molds with all types of plastic molding materials are fully and painstak-ingly described.640 pages Profusely Illustrated $10.00

TUNGSTEN its History, Geology, Ore-Dressing, Metallurgy, Chemis-try, Analysis, Application, and Economics

Second Edition, Revised and EnlargedBy K. C. LI, Governor, Commodity Exchange, New York and CHUNG YU WANG, University

Medalist, Columbia UniversityThis book has been expanded and revised to meet the need for a comprehensive treatment of the geology, proc-essing and uses of this strategic metal. The occurrence, composition and preparation of tungsten ores, its uses,chemistry and economic aspects-all are discussed. It includes maps, illustrations and color reproductions.435 Pages A.C.S. Monograph No. 94 $8.60

Send Todayfor New Free Catalog "Let's Look It UP" (over 200 titles)

REINHOLD PUBLISHING CORPORATION330 West 42nd Street, New York 18, N. Y.

AlsoPublishers of Chemical Engineering Catalog, Metal Industries Catalog, Materials &Methods (formerly Metals and Alloys), and Progressive Architectare-Pencil Points.

I

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INTERF-ERENC:E FiLTrERSfor prompt delivery

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These fixed transmission filters, pro.duced by skillful utilization of mod-ern techniques -in metal evaporation,are now readily available at low costfor solution of optical problems re-quiring narrow-band transmission.

Prompt delivery can be made formost wave lengths.

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These transmission curves are typical of BairdInterference Filter performance. Note that theband width and the specified tolerance com-bine to give adequate transmission at thedesired wave-length.

Baird d/issociates Inc.INDUSTRIAL PHYSICISTS

UNIVERSITY ROADCAMBRIDGE 38, MASS.

FOR LATEST AUTHORITATIVEREVIEWS ON LABORATORY

PROCEDU RES

A monthly publication corm-piled for laboratory direc-tors, technicians and physi-cians. Full of essential factsand reviews of current literature on labora-tory procedure, professionally edited by R.B. H. Gradwohl, M. D., Sc. D. A neces-sity in the modern laboratory. Published by

GIR IIWflHI LSCHOOL OFI.1KfLhIWsIIHI StLABORATORY

MI~fl~hIVI~bTECHNIQUE3514 Lucas Ay. .St. Louis, Mo.

16

LUMETRON Colorimeter MOD. 450for Nessler Tubes

A new photoelectric Instrument for the accurate measurementof pale colors and faint turbidities.

* For all colorimetric determinations in which only aslight coloration can be developed.

* For sanitary examination of drinkable water and foranalysis of water for industrial purposes.

Replaces all visual comparison tests in Nessler tubes.Write for literature to

PHOTOVOLT CORP.95 Madison Ave. New York 16, N. Y.

m--

.... ...0 coo# $see auto

ALL-STEEL GUARDModem research requires higher speed cen-

trifuge equipment. Higher speeds neces-

sitate stronger construction for greaterprotection. The "All-Steel" guard bowlsupplied on the "Reinforced" Size 1, TypeSB and "Reinforced" Size 2 Centrifugesinsures full protection under all operatingconditions.

As the name implies, the All-Steel guardis fabricated entirely of heavy boiler platesteel with all seams heavily welded. Whenyou order your next Size 1, Type SB or

Size 2 Centrifuge, specify the ReinforcedModel with the "All-Steel" boiler plateguard.

INTERNATIONAL EQUIPMENT CO.352 Western Ave. Boston, M m.

Makers of Fine Centrifuge

I-:-1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~he# made *..class Absorpson Cells

Fused under high temperature with acid, alkali ana othersolvent resisting cement. Optical flat walls. Many stock i.

Special requirements made to orderSoleaufaturer is the mUited States of fusedlOectrPhohesis eels

Makers of complete Electrophoresis Apparatus- LETr SCIENTIFIC PRODUCTS

IKltt-Sum eraea Photoelectric Colorneters, ClUrimn-tors, Nophlometoe,Fluerimeters, B10 Colorueoters. e-1trpheresis Appratws. Glow Standards. Kett Reagents

Klett Manufacturing Co.179 East 87th Street, New York. New York

LaMOTTE COMBINATIONSWIMMING POOL TEST-

ING OUTFIT_ This outfit offers you an

easy way to make yourpool the safe, popularplace to swim. It is idealfor the control of residualchlorine and alkalinity inpool waters within the

1 W ranges specified by PublicHealth Authorities-thetests are simple and canbe made quickly and ac-curately. The unit is

compact and portable. Price, complet with in-structions, $12.50 f.o.b. Towson, Md.

LaMOTTECHLORINE COMPARATOR

This comparator provides complete facilities .orcontrolling the chlorination of pool water. Eachunit is complete with calibrated comparison tubes,measuring pipette, reagent and color standards.Price $12.50 including instructions, f.o.b. Towson,Md.If you do not have the laMotte. "ABC of pH Control,"a complimentary copy will be sent upon request with-out obligation.

LaMotte Chemical Products CompanyDept. "H" Towson 4, Md.

1 --jl~~~~~~~~~~~~~~~~~~~*

17

-', :.. 4.1 w-. . 11

Personnel Placement

POSITIONS WANTED

The California Medical Bureau. Agency for scientific and lay personnel inmedicine, biology, chemistry, physics and allied sciences, supplies teachers,research workers, laboratory dieners, skilled office help. Prompt service.Registration free. Your patronage respectfully solicited. THx CAU.-FORIA MEDICAL BUREAU, Agency, Arcade Medical Center, 696 ColoradoStreet, Pasadena 1, California.

Anatomist, PhD, assistant professor, desires change. Publications. Box847, SCIENCE.

Bacteriologist. Minor plant pathology, PhD in June. Desires teachingposition in small college with opportunity for research, or research position.College teaching, other experience. Box 843, SCIENCE.

Woman Chemist: MSc, desires position in greater New York area in trans-lation and literature abstracting work. Languages: English, German,Dutch, French. Available Sept. 1. Box 842, SCIENCE.

Geneticist: PhD. Cytogenetics, plant breeding, considerable trainingin horticulture. Experiment station experience and teaching in plantsciences. Publications. Desires improved position. Minimum salary:$5000. Available September 1. Age 42. Box 849, SCIENCE.

Mathematician, MA, Woman, fifteen years college teaching mathematicsthrough differential calculus. Desires improved teaching position inreputable university or college. Box 850, SCIENCE.

Pharmacologist-Physiologist, M D, 35, assistant professor in medical school,desires improved position. Seven years of teaching, 12 of research. Ex-pect attend Chicago meetings. Box 848, SCIENCE.

Physician, graduate doctorate in bacteriology-immunology, certifiedclinical pathology, with broad experience in medcal school teaching,diagnosis and research desires affiliation part, full-time or consultativewith institution or group. Please provide details. Box 844, SCIENCE.

Physiologist: PhD, female, married, seeking academic or industrial positionin or near New York Cit Publications. Sigma Xi. Experiencedteacher. Box 845, SCIENCE.

Plant Anatomist; PhD. Ohio State University; desires college teachingposition in general botany, plant morphology and anatomy, plant ecology;available July 1. Box 846, SCIENCE.

Secretary experienced, BA degree, biology major, chemistry minor.Reply (Miss) E. L. Hill, 1191 Merrick, Detroit 2, Mich.

Zoologist: PhD, histology, hematology; invertebrate and general zoology;languages. Wide experience in research and teaching. Desires researchor teaching position. Box835 SCIENCE.

Botanist is available; BA (major, botany; minor, geology), MA (major,ecology; minor, taxonomy) PhD (major, plant physiology; minors, geologyand taxonomy); graduate training in plant morphology and anatomy;several years botanist with soil conservation service; six years teachingexperience, biology and biochemistry; for further informationplease writeBurneice LarsonDirector, Medical Bureau, Palmolive Building, Chicago11.

Chemist-PhD (major, organic chemistry; minor, microbiology); severalyears teaching experience; four years research fellow in biochemistry andpathology; eight years director of research in large industrial company-for further information please write Burneice Larson, Director, MedicalBureau, Palmolive Buildng, Chicago 11.

Personnel Placement

POSITIONS OPEN

Attractive industrial research, production and sales positions for agrono-mists; bacteriologists; chemists: analytical, biological, inorganic, organic,pharmaceutical, physical; chemical engineers; entomologists; geologists;horticulturists; metallurgists; microscopists; pharmacologists; physiciansand surgeons; physicists; plant pathologists and physiologists. ChemicalDepartment, Position Securing Bureau, Inc. (Agency) 45 John Street,New York City.

Wanted: A biochemist to do research work in a urological laboratory.,One with experience preferable. Communicate with Dr. A. E. GoldsteinSinai Hospital, Baltimore, Maryland.

Bio-physicist or physicist wanted for research in physiological and patho-logical body mechanics. Full time study in pleasant situation. NewYork Osteopathic Clinic, 205 East 20th Street, New York, N. Y.

Cancer research position in research institute of large midwest hospital.Young MD or PhD interested in cancer research as a career. Specialtraining in pathology or other biological science desirable but not essential.Opportunity for permanent association. Box 852, SCIENCE.

Geologist: One to teach paleontology, micropaleontology andlstratigraphyanother to teach geophysics, a third for courses in physical and historicalgeology. Salary and rank open. Several instructorships in mineralogyand general geology also available. Box 794, SCIENCE.

Mathematician or mathematical physicist, PhD or equivalent, for engi-neering-research group. Problems in space geometry, control systems,general analysis. Publication possible. Salary open. Write Departmentof Electrical Engineering, Northwestern University, Evanston, Illinois.

Pharmacologist, PhD, to take charge of biological laboratory in mediumsized pharmaceutical company. Midwest location in Chicago area. Someindustrial experience in pharmaceuticals desirable, but not absolutelynecessary. Reply Box 851, SCIENCE.

Physicists: Several academic positions, technical branch southeasternUniversity. PhD preferred. MS eligible. Openings in all ranks. Goodpossibilities for advancement. Box 836 SCIENCE.

Zoologist to teach anatomy of the chordates and general biology. Women'scollege, East. Box 840, SCIENCE.

Positions Open: (a) Assistant professor in histology, assistantprofessor inbacteriology, asistant or associate professor in biological chemistry, schoolof dentistry, state university; $4000-4500. (b) Young physician with re-search training or PhD in physiology; research involving high blood pres-sure and urology, department of obstetrics-gynecology, university, medicalcenter. (c) Zoologist to develop invertebrate zoology and parasitology orprotozoology and related fields; should have PhD degree; duties includinggraduate course and assisting with graduate work in zoology; rank depend-ent upon qualifications; Middle Western university. (d) Instructor orassist-ant professor in pharmacology; eastern medical center. (e) Sanitaryengineer; county department of health; staff includes three inspectorsgeneralized program including supervision of milk control; $3300-4200including car and its expenses; East. (f) Statistician to become associatedwith one of the national professional organizations; duties involve statisticswith blood plasma program. (g) Bacteriologist for food research; MSor PhD degree, Middle West. (h) Nutritionist; research laboratories oflarge food manufacturing company; PhD in nutrition or biochemistry re-quired; Chicago. (i) Associate professor in bacteriology and, also, instruc-tor or associate in parasitology; young man interested in research; lightteaching loads; PhD s required. (j) Spectrographer to make spectographicanalyses of plant and animal tissues for presence of minor chemical ele-ments; should be well trained in quantitative chemical analyses withbackground in agricultural subjects; duties include full time research;PhD preferred, MS eligible; department of chemistry, southern university;$4000-5000. S5-2 Medical Bureau (Burneice Larson, Director) Palmolive.Building, Chicago 11.

Universities and colleges throughtout the United States are asking usfor recommendations for positions on their staffs that need to be filled.Because the demand this year is so great, we are interested in furtherregistration of those ready for advancement in professional rank and ofthose who would accept instructorship. Our service is nation wide.

AMERICAN COLLEGE BUREAU28E. Jackson Blvde Chicago 4,Illinois

18

CHARGES FOR CLASSIFIED ADVERTISINGRegular setting lot a word. Minimum charge $2.50 for ac iner-tion. A box number counts as A words of the advertisem t (eg. 25words plus box number equals 33 words). Make checks payableto the A.A.A.S. All insertions must be accompanied by correctrittaace and sent to the Adv. Dept. A.A.A.S. Please addressreplies as follows: Box number, Scrnrcz, 1515 Mass. Ae., N. W.,Washington 5, D. C.

The Market PlaceLANGUAGES

Iaphoie makes languager easy. At home learn to speak Spanish,Portuguese, Italian, French, German, Russian or any of 29 lang es byquick, easy Linguaphone Conversational Method. You learn by listening.Save time, work, money. Linguaphone correspondence courses are aail-able to veterans under the G. I. Bill of Rights. Send for free book. Stateif G. I. LINGUAPONE INSTITUTE, 37 R. C. A. Building. New York 20,N. Y.Technical Translations made from or into any language: Medicine, Chem-istry, Biology, Engineering, Physics, Metallurgy, plastics and other sci-ences. We translate manuscripts, articles, patents, books, catalogues anddescriptive literature. TRANSLATION & RzSEARCH BurAU, 7 East 42ndSt., New York, N. Y-

BOOKSWanted to purchase-Scientific Periodicals, sets and runs. Foreign-Domestic. Entire Libraries and smaller collections. WALTEZ S. JoDox,125 East 23rd Street,7New York 10.Journals, Periodicals, sets and runs. Also whole collections purchased forcash. 3. S. Camu & CoMPANY, 909 Boylston Street, Boston iS,Massachusetts

SUPPLIES AND EQUIPMENTFrone. Argine, otc.; Biochemicas. Consulting, analytical, manufac-turing chemists. Precision analysis of biological materials. H. MCHEmIcAL Co., LTD., 144 No. Hayworth Ave., Ls Angeles 36, Calif.Glucuronic acid, cholesteryl oleate, calciferol, isovaleric acid thymine,amino acids. Dougherty Chemicals, 71-10 Loubet St., Forest lills, N. Y.Bo. 8-5146.For Sale: Two Cenco iypervac Twenty pumps just factory reconditioned$200.00 each plus shipping costs. Philadelphia Serum- Exchange, 1740Bainbridge Street, Philadelphia, Penna.Wanted-High-grade microscope, B & L Research type or equivalent,such as Zeiss Kaydu. Box 6000, Station A, Albuquerque, New MexicoWanted: Homal oculars No. II or VI, III, or B and L Ampliplan low,medium and high oculars. Also Microtessars or Microtars 16 mm, 32mm, 48 mm, 72 mm. Box 853, SCIENCE.Wanted: A Leitz dissecting binocular operating microscope, preferablywith lamp attachment. Box 854, SCIENCE.

\~ Iil,|/,, Dissectinf and Operating Pans\/,and Tables for rats, mice, frogs, cats

and rabbits. Student and researchmodels. Made of stainless metal. Steri-lizable. Quick-adjusting. Simple con-struction. (Pat. pend.) Write for cir-

ZOO-LINE cular.7 Zoo-Line Apparatus Company

1209 Sout* 1700 East Sailt Lake City 4 Utah

B K S SCIENTIFIC and__________ _VTECHNICAL

LARGE STOCK ALWAYS AVAILABLEPlease Stae Interests

LONDON: H. K. LEWIS & Co. Ltd.136 GOWER STREET, W. C. 1Cahlss:-Pubieault: Weatcet: London England -I

PLEASE!IF YOU ARE CHANGING YOUR

ADDRESS, please let us know, if possible,four weeks in advance, giving old as well as

new address, and adding zone number tomeet postal requirements. If you are un-

able to notify us, so as to affect succeedingissues, kindly leave instructions and postagewith your postmaster for forwarding your

copy. Second class matter requires postagewhen remailed to a different address.

SCIENCE1515 Massachusetts Avenue, N. W.

Washington 5, D. C.

1000 SAMPLES in 33 INCHESof SHELF SPACE...!

Here's the answer toa Big Problem

CONVENIENT, COMPACT,~~SAMPLE STORAGE SETS

for indexing and storing referencesamples-100 samples in 3% inches

shelf space; 1000 samples in 33 inches.

MODEL "A" BET, shown her

stores 100 samples (about 10 ml. vol-i"'ume) in 31' shelf space.

ONE THOUSAND SAMPLESwithin 33 inches of shelf space

Choice of 4 ModelsComplete with vials, corks, or caps... gummed labels and larg

Index Cards.

A...ContainalO04j'xji'vlab. $3.25each. m30.dos.A-SC .. Same, as "A", but with rmew-capped vial. $5. each.

848. dos.B . . . Contai50 21' x 1' vials. $250 each, $24. dos.C ... Contains 60 31'x 1'vials. $3.0 each, $56. dos.

Write Dept. S. Orders filed immediately.Hydrion (short rng ndspecial), pH teat p ewrs.

Write for latest information.

R. P. CARGILLE 118 Liberty StreetNew York 6, N. Y.

ERIC SOBOTKANew and Used Microscopes

for Immediate delivery

Microscopes eertly rqepired

102 West 42nd StreetNEW YORK 18, N. Y.

19

--- eq- - W1r---- ---- . - --- . 1

aI

l''GandfD

ELECTRO-TITRATORNOW AVAILABLE FOR IMM1w1EDIATE DELIVERY

WRITE FOR a copy of Booklet 1283 whichcontains complete information on theLeitz G and D Electro-Titrator. It's free.

E. LEITZ, INC.304 HUDSON STREET

NEW YORK, 13, N. Y.

20

LEITZ REPAIR SERVICEExpert repairs on Leitz microscopes and otherLeitz instruments. Factory trained technicians.Genuine Leitz parts supplied. Have your Leitzequipment checked and serviced by those bestqualified to do this work.

1 *wou,

0

_-c

0\0

1S5 51S4 t

501 'een Irango,&1e 'alLC

Al'"'u -i71 5siars .aWa relate,,c13 ala.oa, cXbaJdXaron,.ringy

. . . you can order from a single dependable source. The 173-page "Eastman Or-ganic Chemicals, List No. 35" is your index to the most complete stock of organiccompounds in the world. If your laboratory hasn't a copy, write to OrganicChemical Sales Division, Eastman Kodak Company, Rochester 4, N. Y.

*A useful reagent for identification of alcohols. One of its principal advantages is that theesters formed have very high melting points. The wide differences in the melting points of theesters of homologous and isomeric alcohols make identification easy.**In laboratory quantities at purity indicated by boiling point range-55.5 -55.80. Order it asOrganic Chemical No. 297 (or as P-297 when purity requirements are less stringent).

UW

JA 0 IA\\ . %A-.-C%C-C:-C

IAIA^X

Especially Equipped

~~~SPENCERw _ ~MICROSCOPES

* Microscopic inspection at regular intervals is essentialin controlling objectionable odors, excess toxic industrialwastes, sewage contamination, and in explaining theclogging of filters.Spencer Water and Sewage Microscopes are specificallyequipped to meet the needs of those who safeguard thepublic health. Various applications of the microscope arefully described in StandardMethods of Water Analysis American w Opticalpublished by the American &cntific OIMPANY DivSiOnPublic Health Association. Buffalo M5. NewVYork

Forfurther details write Dept. S2.