Three imPortant new books to help you in your work or study-

A TEXTBOOK OF ENTOMOLOGYBy Herbert H. Ross-

Systematic Entomologist, Illinois State Natural History Survey,and Professor of Entomology, University of Illinois.

This book surveys all fundamental aspects of entomology. There are chap-ters on entomological history, and geological history of insects, showing rela-tionship with economic and scientific progress, and with geo-ecology. Toallow treatment by function, insect physiology is taken up separately. Sub-ject matter is linked throughout with the general biological picture.Ready in October Approx. 525 pages 431 illus. Probable price, $6.00

CLIMATIC ACCIDENTS INLANDSCAPE MAKING

By C. A. CottonProfessor and Lecturer in Geology, Victoria University College,

New Zealand.

This study of the interruptions which occur in geomorphic cycles considersthe "special"n processes which alter normal movements of cycles. The cli-matic shifts to aridity, which causes change in the base-level, are discussedin the first of the book's two sections. The second part is devoted to theclimatic swings to refrigeration, which brings about glacial eroieon.

August 1948 354 pages 267 illus. $7.00

OUTLINES OF PHYSICAL CHEMISTRYBy Farrington Daniels

Profrs ssor of Chemistry, U tiversity of Wisconsin.

A successor to the well-liked Getman-Daniels, the text is now completelythe work of Professor Daniel. Emphasis is placed on the research point-ofview without sacrificing necessary fundamentals. New material has beenadded and, where possible, laboratory data illustrate physical-chemicalphenomena.

Ready this month 713 pages 170 illus. $5.00

JOHN WILEY 6 SONS, Inc., 440 Fouith Ave., Now Yorkm16, N. Y.

SCIENCE, September 10, 1948, Vol. 108

EL-

9

Large, medium,vascular systE

Per dozen (prim

Large selects ainjected withPerdozen ..........

Extra large, laPerdozen ..........

Large and medjected (direcPerdozen ..........

Large, black luljected with aPerdozen ..........

Large, mediumdoubly injectPerdozen ..........

Large and mc4triply injectePerdozen ..........

CAROLINA PRESERVED MATERIALSQuality-Quantity-Dependability

STARFISH BULLFROGS AND GRASS FROGSand small. Plain and with water Large, medium, and small bullfrogs. Plain, singly,

em injected. and doubly injected.cc range) $2.00-$6.00 Per dozen ....... $12.00-$30.00

EARTHWORMS Jumbo, large, and medium grass frogs. Plain,and shorts. Plain and internally singly, and doubly injected.

chromic acid. Per dozen .......................... $2.00-$10.50

s....................................................... $1.00-$1.50Large and medium. Plain, singly, doubly, and

MUSSFELS triply injected.

rge, medium, and small. Per dozen....................... $40.00-$90.00..................................... $1.50-$3.00PIG EMBRYOS

CRAYFISH Extra large (11-13 inches), large (9-11 inches),Lium. Plain and with arteries in- and medium (7-9 inches). Plain, singly, and.tly through heart). doubly injected.

$1.00-$2.00 erdozen ............................... $9. 00-$30.00GRASSHOPPERS Embryos (6 mm.-30 mm.).bber, and Southern. Internally in Per dozen ..........5.50-$15.00

ilcohol. SHEEP BRAINS AND HEARTS

............................................................... $120-$1.25 ater. Per ... $17.50

DOGFISH Sheep hearts. Per dozen .$ 5.00DOGFISH~~sngyan DOGIS1, and small. Plain, singly, and Embalmed, plain, singly, and doubly injected.;ed. Per dozen ................... ........ $50.00-$85.00.........................................................$7.50-$25.00 Dog brains.Per dozen ...............................................$15.00

NECTURUS Dog hearts. Per dozen ... ... $ 5.00dium. Plain, singly, doubly, and Dog kidney, plain, doubly, and triply injected.bd. Per dozen $5.00-$15.00..........................................................$10.50-$25.00D og pluck.Pei dozen ...$15.00

CAROLINA BIOLOGICAL SUPPLY COMPANYElon College, North Carolina

PLEASE!IF YOU ARE CHANGING YOUR

ADDRESS, please let us know, if possi-ble, four weeks in advance, giving old aswell as new address, and adding zonenumber to meet postal requirements. Ifyou are unable to notify us, so as to affectsucceeding issues, kindly leave instruc-tions and postage with your postmasterfor forwarding your copy. Second classmatter requires postage when remailed toa different address.

SCIENCE1515 Massachusetts Avenue, N. W.

Washington 5, D. C.

SCIENCE, September 10, 1948, Vol. 108.

GARCEAU ELECTROENCEPHALOGRAPHSA.C. Operated No Batteries

Inkless Writing Require no ShieldingShipped Ready to Rtut Prompt Delivery

THE JUNIOR GARCEAUELECTROENCEPHALOGRAH

A simplified inexpensive instrument for recording electricalpotentials of the brain. Built-in interference eliminators per-mit use anywhere. Inkless records-no photography or film-development required. Instantaneous localization with any2 of the 10 leads

All Garceau Electroencephalographs operate en-tirely from the 115 volts 50 or 60 cycle power lines.

ELECTRO-MEDICAL LABORATORY, INC.HOLLISTON, MASSACHUSETTS, U.S.A.

10

ALPFTHNEW WORD ON

TELEPHONE CABLES

Lead makes an excellent sheath fortelephone cables - sixty years andthousands of miles in service havewell proven that. But lead is usefulin other ways-storage batteries andpaint, to name only two. So thetelephone industry shares the lim-ited available supply with otherclaimants.

Before the war when there wasno lead shortage, Bell Laboratoriesengineers sought to develop betterand cheaper cable sheaths. An idealsheath is strong, flexible, moisture-proof, durable and must meet spe-cific electrical requirements. Nosingle material had all those virtues,so thoughts turned to a compositesheath, each element of whichshould make a specific contributionto the whole.

Various materials and combina-tions were studied. Desirable com-binations that satisfactorily met thelaboratory tests were made up inexperimental lengths, and spent thewar years hung on pole lines andburied in the ground. After thewar, with an unparalleled demandfor cable and with lead in short

supply, selection was made of astrong composite sheath of ALumi-num and PolyETHylene. NowWestern Electric is meeting a partof the Bell System's needs with"ALPETH" sheathed cable.

Meeting emergencies -whetherthey be storm, flood or shortage ofmaterials - is a Bell System job inwhich the Laboratories are proud totake part.

BELL TELEPHONE LABORATORIES* EXPLORING AND INVENTING, DEVISING AND PERFECTING FORCONTINUED IMPROVEMENTS AND ECONOMIES IN TELEPHONE SERVICE.

-h5

SCIENCE, September 10, 1948, VoL 108 11

THE 1IICKETTSIAL DISEASES OF MAN

A NEW AAAS PUBLICATIONThis new symposium volume, about to appear from the press, is a comprehensive survey of the general field of

Rickettsial diseases in man. Among the 27 contributors appear the names of many of the foremost American au-

thorities on this important and relatively new field of medicine.

The first group of papers includes discussions of the taxonomy, biology, isolation, and identification of vectors,and reservoirs of infection of the Rickettsial diseases of man. The second group of papers is devoted to discussionsof serological reactions, the Well-Felix reaction, the complement-fixation and agglutination reactions, and the prepa-

ration and standardization of Rickettsial vaccines. The final group of papers treats of insecticides, methods of theirapplication, and mite controls.

Many of the contributors to this volume during World War II were on the battle fronts in Africa, Italy, France

and Germany, protecting our troops and the local populations wherever Rickettsial diseases prevailed. Rarely, ifever, have the authors of a medical book had so wide and so successful practical experience in the very subjects on

which they have written.

The Rickettsial Diseases of Man(7V x 1O%, cloth bound)

Price per copy in cartons, postage prepaid, for orders accompanied by checks:

To AAAS members ..................... $5.25

To those who are not members ...................... $6.25

Address orders to AAAS Book Department, 1515 Massachusetts Ave., N.W., Washington 5, D. C.

12 SCIENCE, September 10, 1948, Vol. 108

KLETTELECTRO PHOR ESIS

r

l

CUSTOM MADE -

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

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

M_ I---- --

Ready for Fall Classes!

-IfiT)

Carter's NEW FOURTH EDITION

MICROBIOLOGYAND

PATHOLOGYBy CHARLES F. CARTER, B.S., M.D.

Director, Carter's Clinical Laboratory, Dallas, Texas

830 Pages

With 228 Text Illustrations

and 25 Color Plates

PRICE$5.00

Since the appearance of the last edition of this bookthe sciences of both microbiology and pathology haveundergone great progress. So rapid has been develop-ment and change that methods which were new onlya few years ago are now obsolete.In revising this popular text, Dr. Carter has brought itcompletely up to date, without materially enlargingthe size.All chapters have been carefully scrutinized, someomitted, others combined. In no case have essentialdetails been omitted, however.Added stress has been given the part which microbesplay in the processes of nature, the home, manufactur-ing and commerce. In the section on pathology, chap-ters on vitamin deficiencies and on endocrine glandshave been added.

OUR COLLEGE CATALOG WILL GLADLY BE SENT TO YOU ON REQUEST.

ORDER FORMSci 9-10-48

The C. V. Mosby Co.3207 Washington Blvd.,St. Louis 3, Missouri.

Please send me a copy of Carter's 4th Edition MICROBIOLOGY and PATHOLOGY-The price is $5.00

[] Enclosed is my check. C Charge my account

SCIENCE, September 10, 19481 Vgl. 108

Name

Addresis

...........................................................................................................................................................................................................................................

.....................................................................................................................................................................................................................................

13

Personnel Placement

POSITIONS WANTED

Bacteriologist: B.A. MS. degrees; considerable work towardsPh.D.; three years laboratory experience; two years research as-sistant, university medical school; for further information, pleasewrite Burneice Larson, Director, Medical Bureau, Palmolive Build-ing, Chicago 11, Illinois. X

Electroencephalographer: Experienced diagnostician. Woman,M.A. Experienced in physiological and psychological research.Publications. Interested in full time position or one with oppor-tunity for further graduate work. Box 447A. SCIENCE. X

Chemist: Literature research and report writing, abstracting, ex-cerpting, compiling, analyses and correlation of scientific material.Eight years experience. Knowledge journals chemistry, physics,engineering, medicine, nutrition. New York or suburban area.Interview AAAS Washington Meeting. Box 451A, SCIENCE. X

Physicist: Ph.D., mid 40s, experience in electronics, radioactivity,desires change of position. Research with or without teaching,academic or industrial. Midwest only, Chicago area preferred.Box 443A, SCIENCE. 9-10

Physiologist, now assistant professor of physiology (pharmacologyincluded) in a university medical school, is available: B.A. andPh.D. degrees; research work has been of such outstanding qualityhe was awarded highly coveted Fellowship; for further informa-tion, please write B urneice Larson, Director, Medical Bureau,Palmolive Building, Chicago 11, Illinois. X

POSITIONS OPEN

Bacteriologist: To head newly formed chemotherapy group in thepharmaceutical division of progressive Midwest company. Pleasestate training and experience. Box 446A, SCIENCE. 9-24

Director of training: By old established technical, mechanical in-stitute in Chicago area. Applicant must have engineering back-ground with degrees, teachin; experience as well as administrativeability in supervising a technical, mechanical staff. Remunerationcommensurate with applicants' qualifications. Give complete de-tailed history. All information held in confidence. Box 441A,SCIENCE. 9-10

Pharmaceutical Research Chemist: Good opportunity available fora man 30-40 who can demonstrate marked professional ability inthe development of new pharmaceutical products. Men with ex-perience in the manufacture of tablets, ampules, liquids, ointments,and related products will be given preference. Initial appraisalof respondent will be based on completeness and content of resumeof academic training, scope of experience, and evidence of possess-ing qualities as a leader. Position has good future with largemidwestern pharmaceutical firm. Box 442A, SCIENCE. 9-10

Pharmacologist-M.S. or equivalent in Industrial Research. Willconsider Physiologist with pharmacological experience. Researchposition with Pacific Coast pharmaceutical firm. Salary openwith $3500 minimum. Box 434A, SCIENCE. 9-10

Pharmacology Teaching Assistant: Medical and Pharmacy Schoolsof Pacific Coast University; opportunity for graduate study leadingto M.S., Ph.D. B.S. in Chemistry, biological sciences or Phar-macy required. $1080 per year. Box 448A, SCIENCE. X

Physicist: Physicist with proven administrative ability wanted.Must have Doctor's degree with exceptional experience in the fieldof semi-conductors and the solid state. Salary commensurate withexperience and an unusual opportunity with an aggressive and well-established concern in Cambridge, Massachusetts. Reply, givingfull particulars to: Box 445A, SCIENCE. X

Personnel PlacementPOSITIONS OPEN

Positions Open: (a) Young men trained in radiochemistry or radio-biology; Ph.D. preferred; possibility of considering candidate withMaster's degree; research position; new radioisotope unit of largehospital; Middle West. (b) Professor and head of department ofphysiology, university medical school having important expansionprogram; although physician preferred, Ph.D. eligible: should beclinically minded and interested in research. (c) Senior pharma-cologist and immunologist with special training in bacteriology;research appointments, pharmaceutical company; candidates withPh.D. degrees preferred; $5200-$7800; research involves animalevaluation of new substances to be used for pharmaceuticals. (d)Statistician; division of cancer control, state department of health;should be able to develop broad statistical department coveringseveral public health activities as well as the cancer field; research-minded person required; although man preferred, woman eligible;minimum, $5000. (e) Ph.D. in Physics; liberal arts college ofMiddle Western University; although rank depends upon qualifica-tions, preference for someone qualified to direct department afterbecoming established. (f) Assistant dean, university school ofdentistry; preferably one with Doctor's degree in education orPh.D. with Major in education. S9-2 Medical Bureau (BurneiceLarson, Director), Palmolive Building, Chicago 11, Illinois. X

Psychiatrist: (Psychoanalyst) has a vacancy for a volunteer as-sistant, preferably a Ph.D. in Psychology. Excellent opportunityto learn dynamic and clinical psychiatry. Location: Washington,D. C. Box 450A, SCIENCE. 10-1

The Market PlaceBOOKS

WANTED TO PURCHASE SCIENTIFIC BOOKSAND PERIODICALS

Entire libraries, and smaller collections; sets and runs;foreign and domestic.

WALTER J. JOHNSON,125 East 23rd Street, New York 10.

Your sets and file of scientific journals are needed by ourand institutional customers. Please send us lists and description ofperiodical files your are willing to sell at high marketV S. CANNER AND COMPANY, 909 Boylston Street. roton15, Massachusetts. tf

Send us your Lists of dSCIENTIFIC BOOKS AND PERIODICALS

which you have for sale.Complete libraries; sets and runs; and single titles are wanted.

Also please send us your want lists.STECHERT-HAFNER, INC., 31 East 10th Street, New York 3.

PROFESSIONAL SERVICES

Amino Acid and protein analysis by microbiologic methods. Re-search problems on contract basis. SHANKMAN LABORA-TORIES, 2023 South Santa Fe Ave., Los Angeles 21. Calif. tf

SCIENCE, September 10, 1948, Vol 105

CHARGES FOR CLASSIFIED ADVERTIS3INGRegular setting word Minimum charge $2.50 foreac inserton. A box number counts as 8 words of theadvertisement (e.g. 25 words plus box number uals 33words). Make checks payable to the AAAS. Al inser-tions must be accompanied by correct remittance sad sent14 days in advance of publication date to the AdvertisingDepartment, AAAS 1515 Massachusetts Avenue, N. W.,Washington 5, D. C.

WANTEDVI ROLOGIST-OR

BACTERIOLOGIST Ph.D.

preferably with production experience to head de-velopmental research section. Send personal Data& references in answering.

Write Mr. M. C. Bloom

E. R. SQUIBB 6 SONSNEW BRUNSWICK, N. 1.

14 SCIENCE, September 10, 1948, Vol. 108

The Market PlacePROFESSIONAL SERVICES

SUPPLIES AND EQUIPMENTPre-Mixed Microbiological Assay Media (One complete mixtre)assay standards: pure amino acids (analysed): microbiologios)assays. H. M. CHEMICAL COMPANY, LTD.. 144 N0Has wnrtb Avenue. Los Angeles 36. California tfAll Amino Acids (natural and synthetic, rare sugars. biochemicalproducts and reagents, new pharmaceuticals in stock. Write forcomplete price list. BIOS LABORATORIES, 607 West 43rdStreet, New York 18. tf

MICRORESPIROMETERDifferential type. No thermostat required. For studies withmicroorganisms, tissue slices, insects, etc. Descriptive literaturesent without obligation. MICROCHEMICAL SPECIALTIESCO., 1834 University Avenue, Berkeley, California. X

FOR SALE:Scarce superior Leitz Petrographic Microscope and accessoryequipment. Unused. Immediate delivery: $1680. Terms to suit.Box 449A, SCIENCE. X

-M C1 --

SCIENTIFIC INSTRUMENTSaFPELDEIUIPPENTIPi GEOLO6I5TS5URVEcORS,EENsINWE5PoORExi mery oecessi5)s5gests sdcuA *sro/c3

SCIENCE, SeptemberP10,1948,Vol.10108

SCIENCE, September 10, 1948, Vol. 108

The Market PlaceSUPPLIES AND EQUIPMENT

A.A.A.S. DIRECTORY OF MEMBERSThis Directory, now being printed, con-

tains the names of 40,000 scientists: theiraddresses, positions, degrees, specialties, andprofessional positions.

Included in this 1600 page volume arethe names of scientists from 76 foreigncountries.A unique and valuable feature is its

Geographical Index from which may befound the names of specialists from everyfield of science in every city in the UnitedStates and Canada.

Introductory to the reports on the greatmeetings held by the A.A.A.S. and its affili-ated societies is a Historical Summary ofthe great scientific discoveries of 100 years.About 1600 pages, clothbound.To members, $8.50; to others, $9.50.

-

-

-

-

-

-

-

s

-

-

-

-

-

-

-

-

--

-

-

-

-

s-

-

-

-

s-

-

5

=

A.A.A.S., 1515 Massachusetts Ave.,Washington 5, D. C.

Please send me a copy of the A.A.A.S.Directory of Members and SummarizedProceedings, for which I enclose my cheek.

Name ...........................................................................

Address ..................................................................

15

lHOLTZMAN RAT Co . | |Specializing in the Production of High Quality White Rats

for Laboratory Use.

R. 4, MADISON 5, WISCONSIN PHONE 6-5573

L_. i~~~~~~~~~~~~~~~~~~~on

FOOD RESEARCH LABORATORIES, INC.Founded 1922

Philip B. Hawk, Ph.D., PresidentBernard L. Oser, Ph.D., Director

t 8 RESEARCH-ANALYSES-CONSULTATIONBiological, Nutritional, Toxicological Studiesfor the Food, Drug and Allied Industries

48-14 33rd Street, Long Island City 1, N. V.Write for descriptive brochure

TABLETS: made to order, small or large runs.Would chemicals for reagent or technical purposes orfor laboratory syntheses be useful to you In tabletform? Small quantities can be dispensed accuratelywithout weighing, Inquiries soflcited.

CARCILLE SCIENTIFIC INC.118 Liberty St. New York 6, N. Y.

ANIMAL CAGES AND ACCESSORYEQUIPMENT

ORDERS NOW ACCEPTED FORFALL DELIVERY

HOELTGE BROS., Inc.1919 GEST ST. CINCINNATI 4. OHIO

Write for Illustrated Brochure9-10

1

-1in 1

You get UNIFORMS ACCURATE results with the; i.| .. ..

l

PRECISION INCUBATORPrecise performance is essential in any incu-bator used in bacteriological work . . . andprecise performance is the outstanding featureof all Castle Precision Incubators.Independent laboratory tests proved these

two important facts:UNIFORMITY,* Y.OC. Never as much as a

degree variation between top and bottom ofchamber when loaded.CONSTANT TEMPERATURE, 1'2? to V41C.Never more than a fraction of a degree varia-tion at the thermometer .. despite room

temperature fluctuations.For full details, see your Castle dealer or

write: Wilmot Castle Company, 1212 Univer-sity Ave., Rochester 7, N.Y.

U m~~~~~~~~~~~~~~~~~~~~~~~~~~f~~~~~w-~~~~~~~~~~E #

f

PHOTOVOLTElectronic

Transmission Densitometer

* For accurste measurements of transasiob det ofphotographkc photirogrp , x-ry,*p ph ,A x-ray difration plte ad films.

*. For radiation monitoring with x-ray films.* For exposr dheterion it otomcrorphy by

rect light measuremets i e focal plane.Write for Bulletin #250 to

PHOTOVOLT CORPORATION95 Madison Aye. New Yor 16, N. Y.

Also: Colorimetes, Flesnec Meters,pH Meters, Photome

16

FOR LATEST AUTHORITATIVEREVIEWS ON LABORATORY

PROCEDURES II

A monthly publicationcom_-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

onfAnuinflaAUSCHOOT OF

U VAunu L ;TECHNIQUEa51S4 CIENs t. eSt. 1o0 is, l.

SCIENCE, September 10, 1948, VoL 108

J.. Ia

.1

.1'

TSCALERH ere is the answer to your need for a reasonably priced scaler which combines trouble.free operation with precise and reliable radioassay results. Plug-in Duoscales, embodyingan improved version of the Higginbotham circuit, make possible a simplified wiring layout.

Scaling circuit repairs are made by a procedure nomore complicated than replacing a tube. There isno need to purchase a separate register since "The64 Scaler" contains a built-in Wizard register withprovisions for zero reset. Resolving time of the scal-ing circuit is 5 microseconds, faster than that of anycommercially available Geiger tube. Scale selectorswitch and neon interpolating lights are mounted ina clear lucite dial. A meter on the front panel indi-cafes voltage across the Geiger tube which is con-tinuously variable between 600 and 1800 volts andelectronically regulated. Provisions for stopping andstarting both an electric timer and the scaler with asingle start-stop switch on the front panel eliminate

TOP VIEW OF CHASSIS SHOWING THE timing errors.SIX DUOSCALES PLUGGED IN POSITION Request Bulletin 8 for complete specifications of

"The 64 Scaler"

Commercial Radioactivity Centerinstruments * isotope processing * tracer analyses

;"^...^.;^1 "^1;-------9~._s

More clearly than if they were right imens, lantern slides- all are projected

beside you, your pupils can see and in vivid detail.

understand without moving from their For further information about thisseats-when you perform a demqnstra- and other instruments for visual in-

tion from your desk with a Spencer struction, write Dept. K3

Model B Delineascope.From a convenient horizontal projecu American Optical

tion platform, it throws a clear cut Scientific instrument Divisioimage onto an overhead screen. Science Buffalo 1,NewY~rkexperiments, drawings, contours of spec-

m

a

Count C14 with Maximum Efficiency

"Q-Gas" counter used with Model 163 Automatic Scaling Unit to count C14'

with the new CounterAn exclusive development ofNuclear Instrument & Chemical Corporation ...

Counts alphas, soft or hard betas, and gammas, tooThis is the new counter that's unparal-leled for versatility. It is ideal fordetection of soft ionizing radiation likethat of C14 and 535. There is no windowabsorption or energy loss because thesample is placed inside the sensitivevolume. Yet it efficiently counts hardbetas and gammas, too, because highercounting gas pressure (atmospheric) pro-vides high counting efficiency for pene-trating radiation. Discriminate countingcan also be done by the use of absorbers.This versatility is possible because of theuse of "Q-Gas", a new quenching gasdeveloped exclusively by NUCLEAR.The counter is very longlived becausethere is nothing to replace or repair.Operation is in the Geiger region at

nuclear instrumel| 223-233 West Erie Street, Chi

Formerly Instrument Developm

1450 volts, and no amplification is neces-sary when used with most commerciallyavailable scaling units. The "Q-Gas" iseconomical in operation and quickly ob-tainable from stock. A low cost back-ground shield is available.These are only a few of the manyoutstanding features of the "Q-Gas"counter. Write today for complete in-formation.

most complete lineNUCLEAR'S line of instruments andaccessories for radiation research is un-matched for completeness and quality.We invite your requests for cataloginformation and counsel on isotopeapplication.

nt & chemicalicago 10, Illinois-Cablelent Laboratories, Inc.

corporationAddress "Nuclear"

SPENCER No. 135 LAMP' ~ Here is the illuminator for advanced microscopy you

knew was bound to come . . . with convenient preciseC controls for critical adjustment . . . with essential optical

and mechanical qualities to complement a fine microscope.COOLER OPERATION. Sturdy die-cast housing dissipates heat.

* CRITICAL FOCUSING FROM EITHER SIDE. Rack & pinion movement.

NO TRANSFORMER. Lamp operates from 110 volt outlet.

PRECISION REFLECTOR ADJUSTMENT. lSo quick, simple, and accurate. +

I|||RAPID BULB CHANGE. Lamphouse separates.Hinged lamp chimney opens to reveal bulb and reflector.

*PRECISE TILTING. Screw adjustment maintains any angle.

QUALITY OPTICAL SYSTEM. Two plano-convex lens elements.

IRIS DIAPHRAGM. Knurled ring control. +

FILTER HOLDER. Choice of single or multiple holder.

Correct illumination is essential for thebest results from any microscope objective, American V Opticaleyepiece and condenser. Your instrument ColMPANVdeserves the Spencer No. 735. For further Scientific Instrument Divisiondetails write pt. L1 Buifalo 15. NewYork