From ND 1.329 * . . to ND 1.740

E.K. rz0.ND 20 C. 1.36 1.46 1.66 1.66 1.75

467 Methyl Alcohol 1.8288

Water ................... 1.3330

08 Cyc loh eol... ..............~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. .. .. ......

297 Acetone .................1 92..

300 Ethyl Acetate............ 1.3727

2216 n-Heptane ............... 1.3872

50 -Butyl Alcohol..... 1.3991

62 nEButyl Chloride. 1.4022

2144 -Dioane ....... 1.4223

946 Methyleyclohexane. 1.4235133 Ethylene Glycol. 1.4318

316 Ethyl Citrate... 1.4434132 Ethylene Chloride.. 1.4633684 Trimethylene Chloride. .1.4476972 Cyclohexanone 1.45076

708 Cyclohexanol. . 1.46781698 Diethanolamine. .. 1.47821699 Triethanolamine ......... 1.483 p-Cymene....... 1.4908

241 -Tetrachloroethane 1.4943

326 Toluene 1.9657777 Benzene .......... 1.5017

119 Ethyl Iodide ........... 1.38

406 Anisolee ..........1.... 1261 Trimethylene Bromide....1.5238

70 Cblorobenzene 1.6250

164 Methyl Iodide 1.69310130 Ethylene Bromide... ___________....1.74383193 o-Nitrotoluene....... 1.6466

387 Nitrobenzene ............ 1.5o261617 Tri-ohcresyl Phosphate..... 1.6682

43 Bromobenzene. .1.6602to253 o-Toluldine.. 1.572626 Aniline.....~.......1.686446 Bromoform..........1.5973

1488 o-Iodotoluene..1.6096

216 Qulnaldine.... .....1.6120________

162 Iodobenzene.....,.. 1.6206____

218 Quinoline ........... 1.6272

240 s-Tetrabromoethane. R. 4 N Y.1.637846 .o-Bromonaphthalene.. 1.6680 _1__

1354 Phosphorus Tribromide 1.6966

167 Methylene Iodide.... ..1.74

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The word "Linde" Is a trade-mork of

I _

Arber: Goethe's Botany . . 2.00Asmous: Fontes Hastoriae Botanicae Rossicae.$1.25Baldwin: Forest Tree Seed ..............$ 5.00Bawden: Plant Viruses and Virus Diseases

third revised edition in preparation ..... ........... $ 4.75Biologia (per annual volume) ...... ................ $ 1.25Browne: A Source Book of Agricultural Chemistry ....$. 5.00Browne: Thomas jefferson and the Scientific Trends of

His Time . .....$............... $ 1.25Camp et al.: Intern. Rules of Bot. Nomenclature. $ 3.50Chester: The Cereal Rusts ........ ................. $ 5.00Chronica Botanica (annual subscription) ..... ........ $ 7.50Chronica Botanica, binding cases ...... .............. $ 1.25Condit: The Fig .............. .................... 55.00Copeland: Genera Filicum .$ 6.00Correll: Orchids of North America (shortly) ...... .... ca. $ 6.00Crafts et a).: Water in the Physiology of Plants (ready

shortly) ... ................. ca. $ 6.00Dachnowski-Stokes: Peat (ready shortly) ..... ..... ca. $ 4.75Darwin: A Naturalist's Voyage with the Beagle (1839/

1948) (ready shortly) ....... ................ ca. $ 4.75DeTurk (ed.): Freedom from Want, A Symposium ..... $ 2.00Donk: Genera of Heterobasidlae (in prep.) .... .... ca. $ 7.50Erdtman: Introduction to Pollen Analysis ..$ 5.00Foxworthy: Forests of Trop. Asia (in press) .... .... ca. $ 5.00Frear: Catalogue of Insecticides and Fungicides: Vol. 1.

Chemical Insecticides ................ .$ 6.50Frear: Catalogue, Vol. 2. Fungicides, etc .. $ 5.50Fulford: Bazzania in C. and S. America ......... $ 5.00Garrett: Root Disease Fungi ..............$ 4.50Guilliermond: Cytoplasm of the Plant Cell ............ $ 5.00Gundersen: Families of D:cotyledons (shortly) ...... ca. $ 4.00Hoagland: Inorganic Nutrition of Plants ........... $ 4.50Honig, Verdoorn, et al.: Science and Scientists In the

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and Agriculture (in press) ....... ............. ca. $ 6.00Horsfall: Fungicides (new printing now ready) ..... $.... 5.00Howard: Luther Burbank. Victim of Hero Worship .... $.. 3.75Howes: Vegetable Gums and Resins (in press) ...... ca. $ 4.75lack: Biological Field Stations of the World ..... ...... S 2.50lessen: Botanik der Gegenwart und Vorzeit in Cultur-

historischer Entwickelung (1864/1948) .... ........ $ 6.00Johansen: Plant Embryology (shortly) ..... ........ ca. $ 6.00Kelley: Mycotrophy in Plants (shortly) ..... ....... ca. $ 4.75Knight: Dictionary of Genetics (shortly) ..... ...... ca. $ 4.00Lloyd: The Carnivorous Plants ... $ 7.00MacDougal: Tree Growth (revised ed. in press) .... ca. $ 4.50Merrill: Merrilleana-Selected General Writings .. $. 4.00Moldenke: Plants of the Bible (shortly) ..... ...... ca. $ 4.75Murneek et al.: Vernalization and Photoperiodism .. $ 4.50Nickerson et al.: Biology of Pathogenic Fungi ....... $ 5.00Pfeiffer: Experimentelle Cytologie (second printing ready

shorty) . ................................... ca. $ 4.75Rafir.asque: A Life of Travels .............$ 2.50Reed: A Short History of the Plant Sciences ........ $ 5.50Reed: Ingenhousz's Experiments (shortly) ............ $ 3.50Rickett. Botanical Expedition to New Spain ..... $ 2.50Rothamsted Symposium on Trace Elements (shortly) . . ca. $ 4.00Saint-Hilaire: Voyages au Bresil ....... .............. $ 2.00Schopfer. Plants and Vitamins ........ ............... $ 5.00Snger: The Agaricales (Mushrooms) (in prep.) ..... ca. $ 7.50Sirks: The Evolution of Biology (in press) ..... .... ca. $ 4.000. M. Smith et al.: Man. of Phycology (in press) .... ca. $ 6.00Stevens: Selected General Writings ....... ........... $ 2.00Verdoorn et al.: Manual of Bryology ....... ........... $12.00Verdoorn (ed.): Manual of Pteridology ...... ........ $14.00Verdoorn et al.: Plants and Plant Science in Latin America $ 6.00Verdoorn et al.: Plant Scientists in War and Peace (in

press) ......... .............................. $ 7.50Verdoorn's Annales Bryologici, 16 vols. (1927/39) .. $64.00Verdoorn (ed.): 21st International Plant Science Register

and Directory (in preparation) ...........$ 7.50Waksman: The Act nomycetes (in press) ..... ..... ca. $ 5.00Wilde. Forest Soils and Forest Growth .......... $ 5.00Wodehouse: Hayfever Plants ............ .$ 5.00Wyman: Arboretums of North America ......... . $ 1.50ZoBell: Marine Microbiology .............$ 5.00

Catalogue and Book Dept. Liasts on Request

The Chronica Botanica Co.International Plant Science Publishers

Waltham, Mass., U.S.A.London; Wm. H. Dawson and Sons, Ltd.

Groningen, Netherlands: Messrs. Noordhoff

11

PHOTOVOLTOptical

Fluorescence Comparator

For quantitative analysis of fluorescent solutions bymeansi of furscent standards; for vItamint4, quinine,atabrine, drugs. oils, organic and Inorganic compoundsHigh sensitivity Simple in operaltion

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Write for literature

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STIM ULATORThe Electrodyne Stimulator is primarily designed to af-ford elementary physiological laboratories a generator ofcontrolled electric pulses which may be applied to thestudy of nerve and muscular reactions to changes of

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The wave form of the generatedpulse rises rapidly to a maxi-mum, followed by an exponen-tial decay over a period of 0.3milliseconds.

The Electrodyne Stimulator is usedin the Elementary Physiology Courseat Harvard University in connectionwith the study of: "threshold"; use

A synchronized pulse for a stand-ard signal magnet is generatedby a separate circuit without in-terference with the stimuluscharacteristic.

of cathode ray oscilloscope; frogsciatic; human "motor points"; tur-tle heart vagal stimulation, ventricletetanization; etc.

Stimulator Model 461 is described in Bulletin 187. Specificationsof the Electrodyne Research Stimulator are liven in Bulletin 187-R.

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12

Model 461

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Large clapc

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13

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Personnel Placement

POSITIONS WANTED

Anatomist: Wishes summer position teaching vertebrate compara-tive anatomy or embryology. Prefer New York-Washington area,or Florida. Box 45, Emory University, Georgia.

M.D., Ph.Di (Biochemistry) seeks research or administrative-re-search post. 33, single, veteran. Available October. Box 320A,SCIENCE.

Biologist: Ph.D. eastern university. Desires teaching position withopportunity for research. Only higher ranks considered. Tenyears successful college teaching. Research experience micro-biology. Numerous publications. Veteran, married, family. Box295A, SCIENCE.

Biophysicist, Ph.D.; particularly interested in radiologic physics,including work with x-ray, radium and radioactive isotopes as ap-plied to the field of medicine; teaching and research experience;past several years. biophysicist with large teaching hospital; forfurther information please write Burneice Larson, Director, Medi-cal Bureau, Palmolive Building, Chicago 11.

Botanist desires summer teaching either or both terms. Man,Ph.D. Box 327A, SCIENCE.

Botanist: 36, Ph.D. General botany, taxonomy, morphology, ecol-ogy, biology. Desires teaching position July and August 1948.All replies will be acknowledged. Box 317A, SCIENCE.

Botanist: Ph.D., anatomist and general morphologist. Twentyyears, research and teaching experience; publications. Desiresteaching position with research opportunities. Box 324A, SCI-ENCE.

Botanist: Recent Ph.D. Major training ecology; strong back-ground in soils, taxonomy, conservation. Teaching and researchexperience. Desires teaching-research or research position. Box307A, SCIENCE.

Chemical Engineer: Seeks teaching position in electrochemistryand chemical engineering. Of Chinese birth. Years of experiencein research, plant management and teaching in United States.Ph.D. Columbia 1925. Box 300A, SCIENCE.

Cytogeneticist: Ph.D.; Age 34; Two years post-doctoral scholar-ship research; Two years tomato breeding southern state experi-ment station; Three years present position assistant professormidwestern state university. Desires teaching with part researchat better salary. Box 326A, SCIENCE.

Organic Chemist-microscopist. M.Sc. (Ph.D. equivalent). Minorphysical chemistry; 18 years teaching-* 3 /2 years responsible re-search position. Box 321A, SCIENCi:.

Pharmacologist: Ph.D. Ten years experience in teaching and re-search with executive ability, wants position with at least halftime devoted to research. Box 318A. SCIENCE.

RESEARCH EXECUTIVE, Ph.D.With broad experience in research and research management inthe food industry desires executive position in the research anddevelopment department of a progressive food manufacturing com-pany. Presently employed. Box 325A, SCIENCE.

Scientific Writing, translating, abstracting; medical, biological ex-perience; knowledge scientific French and German; Philadelphiaarea or by mail. Box 322A, SCIENCE.

Zoologist, vertebrate-Ph.D. Cornell, five years teaching experi-ence. Desires teaching position with opportunity for some research.Box 319A, SCIENCE.

14

Personnel PlacementBotanist: Ph.D., to teach plant pathology and plant physiologyat a California state college. Instructor or assistant professor de-pending upon experience. Box 323A, SCIENCE.

Plant Pathologist: To develop program of basic and applied fungi-cide research in state experiment station. Excellent living andworking conditions and opportunity for advancement. Rani andsalary contingent on training and experience. Box 303A,SCIENCE.

Universities and Colleges throughoutAMERICAN the United States continue their

w reat demand for recommendationsCOLLEGE for those trained in the differentfields of Science. The positionsBUREAU ranige from instructorships to heads

of departments.X5 E JaXS Rn

Clia 4, IL Our service is nationwide.

Positions Open: (a) Physiological chemist to head department inlaboratories of 18-man group operating own hospital; duties includesupervising work of staff of seven technicians, conducting researchprogram involving chemistry of body in relation to blood-fluidbalance; Ph.D. preferred; candidate with master's eligible; townof 35,000, Rocky Mountain state; $375-$400. (b) Biophysicist,biochemist, cytologist and physiologist; research department, uni-versity school of medicine; preferably scientists interested in cancerresearch; West. (c) Senior pharmacologist and immunologist withspecial training in bacteriology; research appointments, pharma-ceutical company; candidates with Ph.D. degrees preferred;$5200-$7800; research involves animal evaluation of new substancesto be used for pharmaceuticals. (d) Physiologist or young physicianexperienced and trained in cardiovascular renal disease; full-timeresearch, department of obstetrics-gynecology, university medicalcenter. (e) Director of pharmaceutical research; duties consist ofdirecting group of chemists working on problems of pharmacy inconnection with formulation of new dosage forms and improvementof present products. (f) Bacteriologist to head control laboratories,biological manufacturing company; Ph.D. preferred, will considercandidate with master's or bachelor's degree; Pacific coast. S5-3Medical Bureau (Burneice Larson, Director), Palmolive Building,Chicago 11.

PLEASE!IF YOU ARE CHANGING YOUR

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CHARGES FOR CLASSIFIED ADVERTISINGRegular setting 10¢ a word. Minimum charge $2.50 foreach insertion. A box number counts as 8 words of theadvertisement (e.g. 25 words plus box number equals 33words). Make checks payable to the AAAS. All inser-tions must be accompanied by correct remittance and sent10 days in advance of publication date to the AdvertisingDepartment, AAAS. 1515 Massachusetts Avenue, N. W..Washington 5. D. c.

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.

Journals Periodicals, Learned and scientific serials bought andsold. Complete or part sets, back volumes. J. S. CANNER &COMPANY, INC., 909 toylston Street, Boston 15, Massachu-setts.

Send us your Lists ofSCIENTIFIC 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.

Several issues of AAAS publications are now out of print. TheAssociation will be pleased to receive the following issues:SCIENCE-1947, Vol. 105: #2715, 2717 thru 2726, 2728, 2730thru 2737.THE SCIENTIFIC MONTHLY-1947, Vol. 64: #2, 3, 4, 5,and 6.Second class or parcel post postage will be refunded to thosedonating their spare copies of these journals. Address: AAAS,Attn: Mrs. H. Greenwald, 1515 Massachusetts Avenue, N.W.;Washington 5, D. C.

Wanted: Archives of Biochemistry, Vol. 5; Journal of Biologi-cal Chemistry, Vols. 157, 158. Joseph E. Seagram & Sons, Inc.,Att: Central Purchasing Department, Louisville, Kentucky, Box240.

AAAS Symposia volumes are available as follows:Tuberculosis and Leprosy (133 pp), $3.00 ($2.50 to members)Human Malaria (406 pp), $5.00 ($4.00 to members)Liebig and After Liebig (119 pp), $3.00 ($2.50 to members)Aerobiology (299 pp), $4.00 ($3.50 to members)Relapsing Fever (136 pp), $3.00 ($2.50 to members)Mammary Tumors in Mice (231 pp), $4.00 ($3.50 to members)Dental Caries and Fluorine (111 pp), $3.50 ($3.00 to members)Approaches to Tumor Chemotherapy (442 pp), $7.75 ($6.50 tomembers)

All volumes 7X2 X 10/2, double column, illustrated, cloth bound.Send orders with remittance enclosed to Publications Division,AAAS, 1515 Massachusetts Ave., N.W.; Washington 5, D. C.

PROFESSIONAL SERVICES

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15

I

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1

EARTH SCIENCE BOOKSThe Flow of Homogeneous Fluids

Through Porous Media

By Morris Muskat, Chief of Physics Division, GulfResearch and Development Company

This is a second printing of the reprint edition ofthe book originally published by McGraw-HillPublishing Company, Inc.

xix, 763 p. $7.00

Structural Behavior of Igneous Rocks

By Robert Balk, Department of Geology, TheUniversity of Chicago

A reprint of Memoir 5, Geological Society ofAmerica.

x, 177 p. 25 plates, 3 folded charts $4.25

J. W. EDWARDSAnn Arbor, Michigan

Second AnnualInternational

Photography-in-Science Salon

Sponsored by

THE SCIENTIFIC MONTHLY-SMITHSONIAN INSTITUTION

Accepted entries will be shown fromSeptember 1 to 21, inclusive, in the Nat-ural History Building, U. S. NationalMuseum, Washington, D. C., and subse-quently in museums throughout thecountry.

For information and entry blanks,write to

The EditorThe Scientific Monthly

1515 Massachusetts Ave., N. W.Washington 5, D. C.

MEMBERSHIP IN THE AAAS NOT AREQUIREMENTNO ENTRY FEE

16

COMING

The New SCIENTIFIC MONTHLYBeginning in July: New, larger format and moreauthoritative articles, such as

Time and Change in the Metagalaxy, by HarlowShapley, Harvard College Observatory

Are Our Wars Good Times by William F.Ogburn and Jean L. Adams, University ofChicago

The Problem of the Helicopter, by AlexanderKilemin, American Society of MechanicalEngineers

The Doctrine of Ahinsa and Cattle Breeding inIndia, by Burch H. Schneider, West VirginiaUniversity.

Is Mathematics an Exact Science by N. A.

Court, University of Oklahoma

Bacterial Viruses, by Winston H. Price, Rocke-feller Institute for Medical Research

available for investigational use:

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AN INTRODUCTIONTO COLORBy Ralph M. Evans, in charge of Color Quality,Color Control Department, Eastman KodakComjipany.

A fundamental study, written in non-mathe-matical terms. The book systematically coversthe physical, psycho-physical and psychologicalaspects of color. Starting with the physics ofcolor, the discussion goes on to include a treat-meat of the properties of the eye, then considersthe effects due to the observer himself. Thewhole is then covered in relation to the fields inwhich color plays an important part. Fifteenfull-page color plates are included in a totalof about 400 illustrations.

Ready in June $6.00 340 pages

FARM SOILSFourth Edition

By Edmund L. Worthen, Professor Emeritvs ofSoil Technology, Cornell University.

Written from a practical point of view, FarmSoils includes: directions for managing soils infarming; thorough instruction in such oper-ations as fertilizing, liming, manuring, drain-ing, irrigating and tilling; practical methodsof soil conservation; complete details formanaging soils of gardens, lawns and orchards.This edition contains a new chapter on erosionand its control, and the most recent informationon the best types of fertilizers and theirapplication.

Ready in June Approx. 511 pages

Probable price, $3.60

Preparation and Characteristics of

SOLID LUMINESCENT MATERIALSPublished by arrangement with the American Physical Society, under the auspices of the NationalResearch Council. Edited by Gorton R. Fonda, General Electric Company, and Frederick Seitz,Carnegie Institute of Technology.

One of the most important books in the field ever to be published. It includes 29 papers whichwere first read at a symposium of the Division of Electron Physics. General discussions of the sub-ject were recorded and are included. The papers and discussions offer: a general survey; theory ofluminescence phenomena; purification, crystallization and constitution of luminescent materials; newinformation collected during the war years; a summary of the present status of the subject; andsuggestions and opinions pointing the way toward further needed research.

April 1948 459 pages $5.00

METHODS OF PSYCHOLOGYEdited by T. G. Andrews, Assistant Professor of Psychology, University of Chicago; Scientific Ad-viser, Research and Development Group, Logistics Division, U. S. Army General Staff. Twenty-twoContributing Authors.

Written to fill the need for a book giving greater stress to methodology. Each chapter has beenwritten by a specialist-in terms completely familiar to students who have completed an introductorycourse. In every case the study of methods is related to the major problems of psychological investi-gation. "Content" aspects of general psychology are summarized briefly in each chapter. Only es-sential and modern methods have been chosen for discussion in Methods of Psychology.Ready in June 716 pages $5.00

JOHN WILEY & SONS, Inc., 440 Fourth Ave., New York 16, N. Y.

REPORT No.2 ON PHASE MICROSCOPY

LEADING SCIENTISTSFIND MANY APPLICATIONSFOR PHASE MICROSCOPY

FOR the past two years the American Optical Companyhas been placing phase microscopes in the hands of out-

standing scientists. As a result of their experience we cannow recommend equipment best suited to more than 70different applications. This inforimiation will soon be avail-able in printed form for reference by microscopists.

Some of the many materials in which phase microscopyreveals detail never seen before are: protozoa, bacteria,tissues, blood, chemicals, textile fibers, glass, and plastics.

To cover this wide and rapidly increasing range of applica-tions a number of phase objectives have been developed.They are available in four magnifications, three degrees ofcontrast (Bright, Dark, and B Minus), and in three gradua-tions (low, medium and high). All are now in regular pro-duction.

A new type of Phase Turret Condenser is offered with in-dividually centerable and interchangeable annular dia-phragms. For specific applications involving less frequentchange of magnifications, a single unit, lower cost, con-denser is supplied.Spencer Phase Microscopes and accessories will shortly beavailable through qualified distributors.

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