Kodak reports to laboratories on:a summary of materials for color photography. . . a chemical for cancer investi-gators ... special screens for rear projection ... precisely pre-exposed flilm

ColorA color photograph speaks moreeloquently than one in black-and-white. Here, then, is a rundown ofthe products we offer for impartingthis eloquence and the additionalinformational capacity it adds tophotography.Kodachrome Filtmz everybody

knows about. Comes in 16mm and8mm for movie cameras and 35mmfor still cameras. "You press thebutton, we do the rest."

Kodacolor Filni is for roll filmcameras. We process to a negativewithout additional charge, and thenfrom your Kodak dealer you orderprints or enlargements. No projec-tion, no holding up against the light.Beyond these two that are familiar

to millions of amateurs there isKodak Ektachrome Film. It comesin roll and sheet film form, and you(Qr a local lab) convert it to a trans-parency. If you'd rather have a printto look at, we can make you a Koda-chrome Enlargenment, provided youroriginal is 4" x 5" or less. If it'slarger, we suggest a print by theKodak Dye Transfer Process. Thisyou can undertake yourself or leaveto a commercial laboratory for acreation of smashing visual impact.

Finally, if you'll be wanting sev-eral duplicates at minimum cost,particularly of exhibition size andwith the color brilliance so easilyachieved in a transparency, makeyour original negative on KodakEktacolor Film and your duplicateson Kodak Ektacolor Print Film.

Your Kodak dealer sells all theseitems and also the Kodak Color Hand-book ($4) that delves deeply into thedetails. Write Eastman Kodak Com-pany, Rochester 4, N. Y., ifyou have anydifficculty finding out what you want toknow.

CarcinogenWe've just made up a new batch of3-Methylcholanthrene, and here it is,in its entirety. The synthesis we usewas first published by a man full ofhonors in polycyclic chemistry. Itstarts with chlorotoluene. Con-dense with chloropropionyl chlo-ride. Close the ring to give the chlo-romethylhydrindone. Reduce to thecorresponding chloromethylhydrin-dene. Replace the chloro group witha nitrile group. Add an --naphthylgroup to the nitrile group. Pyrolyze

to 3-Methlylcholanthrene, which isEastman 4383 in the catalog ofEastman Organic Chemicals and

happens to be one of six carcino-genic hydrocarbons we produce forqualified cancer investigators whodon't like to badger their syntheticorganic chemical colleagues to gothrough operations like this forthem.

There are more thani 3500 otherEastman Organtic Chemicals in the cata-log. If the copy in your lab isn't marked"List No. 38," you had best drop a noteto Distillation Products Industries,Eastman Organiic Chemicals Depart-ment, Rochester 3, N. Y.(DivisionofEastman Kodak | |C'ompany). I

Rear projectionAny intelligent schoolboy knowsthat to look at a projected real im-age up close without getting in theway of the beam you catch the im-age on a diffuser like a ground glass.As the schoolboy grows into an op-tical engineer, he learns that a)the better the diffusion the morelight is likely to be wasted intospace where there are no eyes toprofit from it and b) ground glassreally doesn't diffuse very well, be-ing prone to a "hot" center and

a -,-TYPE 4 1I~

KODAK DAY-VIEW SCREEN

.111a ~ -TYPE I

TYPE 4E

..O 10- 20- 30- 40' so, 60' 70-ANGLE

dark corners for the image. As theengineer pursues the subject, he getsinvolved in the theory of field lenses,the light economy of high overalltransmission, the contrast-enhanc-ing value of light-absorbing mate-rial to counteract ambient illumina-tion, the question of graininess, and

the matter of over what angle theimage is to be seen. Eventuallyhe hears about Kodak Day-ViewScreens, a light-scattering disper-sion in gelatin on glass.Type I is white, of high transmis-

sion, with twice as much light trans-mitted at 300 as ground glass trans-mits. Type IV is rather black, whichimproves contrast substantially athigh (but not at low) ambient levels.Type IVR is green, which is sup-posed to be more restful to the eyesin constant use. The curves, belowleft, give brightness vs. angle on ascale where unity represents the re-flectance of a perfect diffuser.

Lookinig at the curves mav be ofsomehelp, but it's no substitute for actuallytrviing the three types of screents in anvapplication you may have in minid. IfseriouslYv interested, write EastmanKodak Company, Special ProductsSales Division, Rochester 4, N. Y.

Flashed densitiesGenerally we sell our film unex-posed, but even to that there is an ex-ception. We refer to Kodak FlashedDensities, used for cutting downlight by a specific fraction. They'replain sheets of precisely exposed,precisely processed, and preciselycalibrated film (not to be confusedwith Kodak Wratten Neutral DensityFilters, in which diffuse densitynearly equals specular density).One application is in equipment

for patrolling the smoke output ofdistant chimneys by comparisonwith adjacent sky seen through thefilm. To a wider audience than justsmokestack inspectors, we announcethat we can supply any flashed den-sity from .05 (890 transmission) to4.05 (0.00900 transmission), with adensity tolerance of i 30% or +.02 in density, whichever is greater.Maximum usable area is 72,4"xx91/2'',including holes at the corners. Pricesvary from $2.75 for 4" x 5" size inthe .05 to 1.05 density range, up to$25.25 for 8" x 10" in the 3.06 to 4.05density range.

Ifany questions about Kodak FlashedDensities occur to you, drop a note toEastman Kodak Company, IndustrialPhotographic Sales Division, Rochester4, N. Y.

A

This is one of a series of reports on the many products and serviceswith which the Eastman Kodak Company and its divisionsare ... serving laboratories everywhere

The RecoCHROMATOGRAPHYDRYING OVENA mechanical convection ovendesigned for heating paperchromatograms.

The RecoCHROMATOCABFor two dimensional paperchromatography, using stand-ard filter paper sheets 183/4by 221/2 in., or smaller.

-- RACKSStainless steel or glass for one

dimensional chromatography.

. L t ~INDICATOR SPRAYSI /JJ \ For application of indicators tol /g \ ~chromatograms.

CLIPSl [All stainless steel spring clips for 'KL.jII [holding chromatograms to glass rods

!~~~~~~n=iovr.JTTtn Ii r- c I /-D-q)OOWU L LV tlFoI IKUusin r_ ~~~~~Foruse in chromatoicabs'-- ~~or one-dimensionalI racks.

I .I ALSO AVAILABLE:

I Densitometers...for quantitative deter-minations on paper

I Ultraviolet LampsI Pyrex Disc ChambersI Micro PipetsI Desalters

July 24, 195311~~~~~

A General Catalogueof the RECO Line ofPaper PartitionChromatographicEquipment Is

Available on Request.

KLETTELECTROPHOR ESIS

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

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---.a

July 24, 1953 11

PERSONNEL PLACEMENT

||11||111110j|1ll| POSITIONS WANTED |ltllllliljllll]lJ4JBacteriologist-Chemist: D.Sc., training and experience in bac.terial enzymology, immunology, food bacteriology, micro-biologicalassays. Desires research (industrial or academic) or teaching posi-tion. Box 141, SCIENCE. 7/31

(1) Biochemist: Ph.D., 26, 4 years' experience biochemistry andmedicinie, medical research, desires same, any location, veteran.(2) Bacteriologist: M.S., 33, 3 years bacteriology, pharmaceuticalfirm, 2 years research associate, university, seeks same or labora-tory directorship, East. (3) Parasitologist: M.S., 4 years univer-sity, 3 years teaching hospital, mycology experience, any location.For further information please write, Science Division, WoodwardMIedical Buireau, 185 North Wabash, Chicago. X

Biochemist: Associate professor, 11 years' teaching experience inmedical biochemistry and immunology. Approximately 30 publica-tionis in enzymology, immunochemistry, protein chemistry, nutri-tion, clinical chemistry. Desires teaching and research appointmentin medical school, or research appointment in hospital or othermedical research institution. Box 140, SCIENCE. 7/31; 8/7

Mineralogist and Petrographer. Ph.D. '52. Optical, physiocochemi-cal mineralogy, petrography, crystallography, X-ray diffraction.University teaching and research experience. Desires teaching orresearch position. Box 138, SCIENCE. X

Ph.D. Zoology, Chemistry; prefers teaching and research orstraight research; four years, instructor in zoology; three yearsassistanit professor of biology, eastern university. For furtherinformation, please write Science Division, Medical Bureau (Bur-neice Larson, Director) Palmolive Building, Chicago. X

Physician, NI.S. in biochemistry, experienced in research. Age 35.Box 139, SCIENCE. X

Plant Physiologist, recent Ph.D.; (minors; Botany, Bacteriology);desires industrial or teaching appointment. Please write ScientificPersonnel Service, 122 South Michigan Ave., Chicago. X

Zoologist, Ph.D.; male, available for teaching and/or research posi-tion in Western U.S. or Canada. Experienced in comparativephysiology, histochemistry, anatomy and enzyme research;references. Box 142, SCIENCE. X

|||||||||||||||||||||||POSI'HONS OPEN I|||||||||||||8||||||Bacteriologist, Ph.D.; research appointment; food manufacturingcompany, Midwest. Please write Scientific Personnel Service, 122South Michigan Ave., Chicago. X

(1) Biochemist: M.S. with adequate experience or Ph.D., 400-bedhospital, excellent facilities; $6000, Chicago Area. (2) Chemist:M.S., Ph.D., clinical pathology, 325-bed hospital, medical schoolaffiliation; $7000. (3) Bacteriologist-Serologist: M.S., hospital ex-perience, expanding laboratory program, 200-bed hospital, univer-sity citv; $5000 up. For further information, please write, ScienceDivision, Woodward Medical Bureau, 185 North Wabash,Chicago. X

Pharmacologist, recent Ph.D., experience desirable; research inlarge drug manufacturing company in East. Salary open. Box 137,SCIENCE. 7/24

||||||||||||||||:|||!|t|POSITIONS OPEN ||

(a) Pharmacologist, M.D., or Ph.D., to conduct research on phar-macodynamic action of drugs; minimum three years' experience,pharmaceutical industry required; East. (b) Immunologist orchemist; research institution specializing in investigation of malig-nancy; investigators experienced in cancer research required.(c) Physiologist; Ph.D. preferred with background in biochem-istry; university school of dentistry; in addition to teaching, op-portunity for research. (d) Bacteriologist; research position inindustry; university town, Midwest. (e) Assistant professor,physics; Ph.D.; South. (f) Director of Chemistry; laboratorylarge teaching hospital; ample time for research; East. (g)Physiologist; Ph.D. required, Master's desirable. (h) Assistantprofessor of botanv; college of pharmacy; East. S704 ScienceDivision, Medical Bureau (Burneice Larson, Director) PalmoliveBuilding, Chicago. X

L1ANGUAGES l||||||

LINGUAPHONE MAKES LANGUAGES EASYAt home, learn to speak French, Spanish, German, Italian, Nor-wegian, Russian, Japanese, any of 29 languages by quick, easyLinguaphone, Worlds Standard Conversational Method. Save timwork and money. Send for FREE book TODAY. LINGUAPHONiINSTITUTE, 8407 Mezz., Rock. Plaza, New York 20, N. Y.

WANTED TO PURCHASE . . . Sets and runs. foreign

SCIENT|*P PERIODICALS and domestic. EntireSuui.gi~~~~~. } ~libraries and smallerand B O O K S collections wanted.

WALTER J. JOHNSON * 125 East 23rd St., New York 10, N. Y.

Your sets and files of scientific journalsare needed by our library and institutional customers. Please sendus lists and description of periodical files you are willing to sellat high market prices. Write Dept. A3S, J. S. CANNER, INC.

Boston 19, Massachusetts

LOOK A4ROUND ... notice the increasingnumber of satisfied advertisers using small-space ads regularly inpractically every issue of SCIENCE-proof that these small ads getresults! If you have a product or service of interest to scientists,why not take advantage of this low-cost means of increasing yourprofits!

SCIENCE, Vol. 118

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YOUR ad here reaches over 32,000 scientists in theleading educational' institutions, industrial laboratories,and research foundations in 77 countries-at a verylow cost.

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a

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BACK NUMBER PERIODICALS - Bought and Sold[ Tell us what you want -What have you to offer?

Abrahams Magazine Service K DEPT. P. 56 E. 13th ST.Established 1889 P NEW YORK 3, N. Y.

SCIENTIFIC BOOKS and PERIODICALS WANTEDComplete libraries - Sets and runs - Single tites

Please senduw your wnt listSTECHERT - HAFNER INC. 31 East 10th St.. New York 3The World's Leading International Bookse

AVOID DELAY .... Cash in Advance paymentMUST be enclosed with ALL classified ads.See "Charges and Requirements"

LOOKING FOR A PUBLISHER?Write for Free Booklet SC telng how we can publishyour book. All subjects conidered. New authon velcome.

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_tProject research and consultation inaBiochemistry, Chemistry, Bacteriology- ~~~and Entomology

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liiiWf1WIfhIlllhIIiIIPROFESSIONAL SERVICES IIIII1IIIIfhII1ILNS11I

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For Sale: Journal Sets. 8000 plus papers, monographs. Biology,Philosophy, mainly Cytogenetics (1900-1953) Box 143, Science. X

INDEX OF REFRACTIONShillaber's Certified Index Liquids

High Index Liquids (1.81-2.0)Allen's Solid Refractive Index Standards

For MicroscopyWrite for informative ND-S leaflets

R. P. CARGILLE LABORATORIES, INC.117 Liberty Street e New York 6, N. Y.

For CONSISTENT Rats . 0

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STAINSSTARKMAN BIdIgId ah-aluy

(THIS 1s the EXACT SIZE REOTANGLEon the Field Finder containingover LQ00O lines and lndicia.They for a simple, non-marklngdevice for the microscopist to re-locate fields of interest In aslide-mounted specimen.' Otheradvantages: Superb precision-with lnterchangeability; non-des-truative; used by substitution.)

YRTIC! WMR AM.T.rTTV

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PARASITOLOGICAL PREPARATIONS* high quality - low priced. Write for catalogTROPICAL BIOLOGICALS * P.O. Box 2227, San Juan, Puerto Rico.

July 24, 1953

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Guaranteed suitable for your needs.JOHN C. LANDIS . Hagerst., Md.Reasonably pricedDependable service

CYCLOHEPTANONE I replies received from ONE| 2,4-DINITROFLUOROBENZENE i classified ad in SCIENCE...

9-CHLOROBUTYRON ITRILED ,.~Your ad here will get results!Write for a copy of price list

CUSTOM CHEMICAL LABORATORIES Send your ad NOW!2054 N. Cicero Ave., Chicago 39, Ill.

PHOTOVOLT -Line-Operated Electronic CentennialMULTI PLI ER-PHOTOMETER Symposia presented to commemorate the first

Mod. 520-M hundred years of AAAS include 42 papersby leading scientists in thirteen major fields:* Sciences of Society * The World's Natural* Educational Potentials Resources* Human Individuality * Genes and Cytoplasm* Food and Nutrition * High Polymers* Housing* World Health Problenxs Interactions of matter*Sources of Energy and Radiation

* The Upper Atmosphere- W'aves and Rhythms7% x 10Y2 inches, double column,

clothbound, 320 pages

Cash price to AAAS members $4.50Nonmembers and institutions $5.00

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Absorption and flame photometry. Colorimetry through I5lWWashingtonS, D. C.microscopes. Scintillation measurements. Fluorescence EnclWshing Dc.trace analysis. Monochromatic color densitometry. Enclosed find my check or money Qrder for

Write for Bulletin #360 to $....... for one copy of Centennial.

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14 SCIENCE, VOl. 118

Evolution in the GenusDrosophila

by John T. Patterson and Wilson S. StoneThe most extensive treatment of any living genus thus far attempted, the bookcovers the evolution of the Drosophila as demonstrated by living forms. It ismainly concerned with isolating mechanisms, genetic systems shown by hybrids,and the cytology of over one-third of the known species of the genus. Being amonograph of the Genus Drosophila, the book gives the distributional relation-ships, chromosomal evolution, and changes in genetic systems leading to isola-tion which allows the genus to diversify.

610 pages. 1953 $8.50

Genetics in the TwentiethCentury

edited by L. C. DunnThis collection of papers prepared for the Golden Jubilee Meeting of the GeneticsSociety of America surveys the growth and development of genetic theory duringthe past 50 years. Each outstanding contribution covers a different phase of thescience. Important agricultural and medical applications are discussed as well asthe latest theoretical and experimental findings.

634 pages. 1951 $5.00

Evolution Emergingin two volumes-by William K. GregoryThis new work summarizes from the available evidence the epic of evolution,spanning a time period of more than 500 million years and the slowly changingpatterns of life from primeval forms to man. It is arranged in general order fromthe earliest to the later forms, and from the less differentiated to the more differen-tiated. Volume I contains all the textual material, while Volume II consistsentirely of illustrations organized in the same order as the material in Volume I.

Vol. 1 736 pages, Vol. 11 1013 pages $20.00 per set

eJee c4 ay60 FIFTH AVENUE, NEW YORK 11, N. Y.

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"PINCH GRIP"MECHANICAL STAGE

FOR THE MAN who uses microscopes day afterday, year after year, bnly the simple construc-tion of the AO Spencer "Pinch-Grip" Mechani-cal Stage ogers such ease of operation, safetyto slides and durability.

Slight pressure between forefinger andthumb opens the gripper arm without jarringthe stand or disturbing mechanical stage set-tings. Upon release, the arm returns smoothly

holds slides firmly without injury. An extra-long coil spring permanently provides just theright tension.

This AO design for the microscopist is ap-parent also in the renowned Spencer Optics,dust-proof, dual-cone nosepiece, "autofocus",custom tension adjustment, "full-field" illumi-nation, convenient arrangement of controls, andmany other features. But test the many advan-tages of AO Spencer Microscopes yourself. Askyour AO Spencer distributor for a demonstra-tion or write Department U4.

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