w~~~~~~~~~~~~~~~~~~~~--

J~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Beckman L5 Uftraetifithey offer you the-Important choices.

In considering preparativeultracentrifuges, you probably wantthe widest range of choices you canget in rotors, tube materials, andaccessories, as well as the finest ininstrumentation, service andapplications back-up. Only Beckmanprovides them all.* You have a choice of four differentBeckman L5's, ranging from the40,000 rpm Model L5-40, to the 75,000rp*m Model L5-75,- the mostsophisticated preparative ultracen-trifuge available.* There are 34 Beckman titaniumand aluminum rotors -18 fixedangle, 10 swinging bucket, 5 zonal,and one continuous flow. They offera wide variety of volumes, forces, and

other characteristics to meet virtuallyany separation need.* You have a choice of Beckmantubes in four materials - cellulosenitrate, polycarbonate, polyallomer,and stainless steel. They featuremanydifferent combinations ofpuncturability, trans-parency, autoclavability,chemical resistance, andstrength.* And there are ahost of Beckmanaccessories rangingfrom densitygradient formers,fraction collectiondevices and a slowacceleration unit, tothe PrepUV Scanner which.gives results closelyapproaching those from ananalytical ultracentrifuge.

It's no wonder that nearlyeveryone in the world who buys anultracentrifuge, chooses Beckman.For literature on the L5's and theiraccessories, write for Data File400/174 to Spinco Division, BeckmanInstruments, Inc., 1117 CalifomiaAvenue, Palo Alto, CA 94304.

I*

e UU

The Most Astonishing Scientific

OfThis Decade!106 Complete Functions * Features Unequalled b Any Other Make

Produced in USA by COMMODORE

The

Commodore

rechargeable

SR4I9OR

There has never been an electronic calcu-lator with so extensive a performancerange as the brand new CommodoreSR41 90R. Its operating capacity, combinedwith the speed and accuracy with whichcomputations are performed is unequalledby any other calculator.

We are proud to offer it to you on a,"no-questions asked", full refund guaran-tee. More than its diversified applications,we want you to appreciate its many exclu-sive advantages for yourself.

Discover its unique Hours-Minutes-Seconds in digital clock format. Ambiguityis a thing of the past. And you can performarithmetic operations, such as time studyand motion analysis in this mode as easilyas in the decimal mode.

Complex numbers, difficult on somecalculators, impossible on others, are di-rectly accessible from the SR4190R key-board. Thanks to its extraordinary accuracylimit, Combination and Permutation opera-tions are not hindered by the overflowwhich occurs when the factorial is largerthan 10190

Among the 106 direct entry functionsare Poisson and Binomial Probability Den-sities; Gaussian Distribution; Linear Re-gression Analysis; Mean and StandardDeviation; and so many more. Most im-portant, all are on the keyboard. Severalthousand internal preprogrammed stepsput all of these functions at your fingertips... instantly. You needn't bother with pre-paring formulas, creating programs ormaintaining an elaborate library. It's allright there. The broadest range of diversi-fied applications is at your command.

A Limited Offering @

$7995A powerfulvnmnMarammad

A Brief Summary of the SR419OR1 0-digit Mantissa, 2-digit exponent withVariable Exponent Integer Increase andDecrease: MANT, EE, EE t, EE IRegister Keys: STO 1, RCL 1, 11, STO 2,RCL2, .2, x+y, Xn, Xi, Yi,a,f, y, 0.One Real Variable Function Keys: In, log,ex, 10X, 1/x, \Zx2, SIN, COS, TAN,INVSIN, INV COS, INV TAN sinh, cosh, tanh, INVsinh, INV cosh, INV tanhTwo Real Variable Arithnetic Function Keys:

Two Complex Variable Arithmetic FunctionKeys: j +. j -, j x, j-Two Real Variable Analytical Function Keys:

pn, I, yx, -,'y, %, A%, CnStatistical Function Keys: x++y, SLOPE,INTCP, GAUSS, BINOM, POISS, x,, Ys

Hours-Minutes-Seconds Mode: HMSUnit Conversions: (°F) C, (d) dms, (d) gra,(gal) 1, (oz) g, (lb) kg, (ft) m, (mi) km, (f oz) 1,(in) cm, (BTU) JDegree/Radian Conversion and Mode Keys:d/r, d+-rNumerical Entry Keys: 0-9, ir

3 Angular Units: radians, degrees, gradsPoisson and Binomial probability densities.Gaussian distribution.Mean and Standard Deviation PLUS LinearRegression Analysis.Power supply: Built-in rechargeable Ni-Cadbatteries. AC adapter/recharger included.One Year Warranty

30 APRIL 1976

multifunctioncalculator with 106directly accqssiblekeyboard functions.The complete mini-computer forEvery EngineerPhysicistChemistGeologistDemographerEcologistMathematicianStatisticianQuality Control AnalystTime and Motion ExpertAdvanced Student... and so many others

FCall Toll Free:800-323-2408

(Illinois call: 312-595-0461)Work With It For Two Weeks

No ObligationPlease send.. Commodore #4190R 106 Func- |

I tion Scientific Calculator(s) at the limited priceoffering of only $79.95 (plus $3.95 shipping andinsurance) each. If not completely satisfied I canreturn it within two weeks for an immediate refund.

| Check or Money Order Enclosed3 Charge My Credit Card Checked Below:

|3 American Express a BankAmericardO3 Diners Club 0 Master Charge

Carte Blanche

| Credit Card I

Master Charge Bank #____ I

Expiration Date I

IName l

Address I

City State Zip I

Signature I

I Co t Send Couponlo: h.tIq Inc.790 Maple Lane, Bensenville, Il. 6610 J

419

commodoreA Name You Can TrustCommodore is perhaps the oldest brand in con-sumer electronic calculators. The SR419OR wasdesigned, developed and produced in Palo Alto,California. Other Commodore plants are locatedin Osaka, Japan, Toronto, Canada and Eaglescliff,England.SATISFACTION OR YOUR MONEY BACK IN FULLOrder your SR4190R Rechargeable Scientific on a"No-Questions-Asked" trial basis. If not satisfiedwith the performance of your SR4190R, return Itfor a full refund.

aaas announces. . . . . 0

Reviews of ScienceDon't miss this chance to keep up with SCIENCE! Our new compendium series presents au-thoritative articles on many of the principal issues that face science and society-articlesoriginally published in SCIENCE, selected from earlier years as well as from recent issues-articles you would have clipped for future reference if you knew then what the critical issuesof today would be-articles you will want to assign your students for background reading, oruse to supplement your own professional library. . .

We've brought these articles together in attractive compendium volumes on food, on energy,and on population. And others are in preparation, including a volume on materials to be pub-lished in May 1976. Each compendium is available in your choice of casebound or paperboundedition. Order one-or all of them-today!

1. ENERGYEnergy: Use, Conservation, and Supply. Edited with foreword by Philip H.Abelson; 154 + v pp. ISBN (CB) 0-87168-213-3, (PB) 0-87168-223-0.

A collection of enduring and read-able articles on ways to conserveenergy and use it more efficiently, notonly in industry but also on an indi-vidual level.

Partial Contents ListingLow-Cost, Abundant Energy: Paradise

Lost?: H. H. LandsbergEfficiency of Energy Use in the United

States: Eric Hirst and John C. MoyersEnergy Conservation: G. A. LincolnConservation in Industry: Charles A. BergIndividual Self-Sufficiency in Energy: Allen

L. HammondEnergy Use in the U.S. Food System: John

S. Steinhart and Carol E. Steinhart

Prognosis for Expanded U.S. Production ofCrude Oil: R. R. Bert, J. C. Calhoun,Jr., and R. L. Whiting

Oil and Gas Resources: Did USGS Gush TooHigh?: Robert Gillette

Oil Shale: A Huge Resource of Low-GradeFuel: William D.. Metz

Problems of Expanding Coal Production:John Walsh

Clean Fuels from Coal Gassification:Arthur M. Squires

Nuclear Electric Power: David J. RoseEnergy Choices That Europe Faces: A

European View of Energy: W. HafeleGeothermal Electricity Production:

Geoffrey R. RobsonSolar Energy by Photosynthesis: Melvin

Calvin

Solar Energy Utilization by PhysicalMethods: Martin Wolf

Power, Fresh Water, and Food from Cold,Deep Sea Water: Donald F. Othmerand Oswald A. Roels

Windmills: The Resurrection of an AncientEnergy Technology: Nicholas Wade

Methanol: A Versatile Fuel for ImmediateUse: T. B. Reed and R. M. Lerner

Hydrogen: Its Future Role in the Nation'sEnergy Economy: W. E. Winsche,K. C. Hoffman, and F. J. Salzano

Energy Storage (I): Using Electricity MoreEfficiently: Arthur L. Robinson

Energy Storage (11): Developing AdvancedTechnologies: Arthur L. Robinson

2. POPULATIONPopulation: Dynamics, Ethics, and Policy. Edited by PriscillaReining and Irene Tinker with a preface by Margaret Mead;184 + viii pp. ISBN (CB) 0-87168-214-1, (PB) 0-87168-225-7.

The ethical issues of choice . . . theinterrelationship of population sizeand economic development . . . theconsequences of population growth-such are the issues debated in thiscompendium. A collection of out-standing articles, research reports,and policy debates that appeared inSCIENCE during a 10-year time spanbeginning in 1966.

Partial Contents ListingEthics and Population Limitation: Daniel

CallahanThe Tragedy of the Commons: Garrett

Hardin422

Beyond Family Planning: Bernard BerelsonPopulation Policy: Will Current Programs

Succeed?: Kingsley DavisFamily Planning and Public Policy: Who is

Misleading Whom?: Judith BlakeAID's Family Planning Strategy: R. T.

RavenholtIntegrated Incentives for Fertility Control:

Lenni W. KangasToward the Reduction of Unwanted Preg-

nancy: Frederick S. JaffeThe Perfect Contraceptive Population: Larry

Bumpass and Charles F. WestoffAbortion, Illegitimacy, and the American

Birth Rate: June Sklar and BethBerkov

The Limitation of Human Population: A

Natural History: Don E. DumondThe Demography of Primitive Populations:

Norma McArthurPorotic Hyperostosis, Anemias, Malarias,

and Marshes in the PrehistoricEastern Mediterranean: J. LawrenceAngel

!Kung Hunter-Gatherers: Feminism, Diet,and Birth Control: Gina BariKolata

Other People's Family Planning. Review ofThe Khanna Study (Wyon and Gor-don) and The Myth of PopulationControl (Mandani): Burton Benedict

Feedback in Economic and DemographicTransition: Harald Frederiksen

Man and His Environment: Ansley J. Coale

Ecology and Population: Amos H. Hawley

SCIENCE, VOL. 192

Height and Weight at Menarche and a Hy-pothesis of Critical Body Weights andAdolescent Events: Rose E. Frischand Roger Revelle

Immigration Composition and PopulationPolicy: Charles B. Keely

Cross-National Comparison of PopulationDensity: A lice Taylor Day andLincoln H. Day

Urban Growth and Decline: San Jose andSt. Louis in the 1960's: Peter A.Morrison

Population and Pollution in the UnitedStates: Ronald G. Ridker

Birth Order, Family Size, and Intelligence:Lillian Belmont and Francis A.Marolla

Contraceptives and Dysplasia: Higher Ratefor Pill Choosers: Elizabeth Stern,Virginia A. Clark, Carl F. Coffelt,and Paul Shankman

Birth Control after 1984: Carl DjerassiRelevance of Demographic Transition

Theory for Developing Countries:Michael S. Teitelbaum

3. FOODFood: Politics, Economics, Nutrition, and Research. Edited with foreword byPhilip H. Abelson; 202 + v pp. ISBN (CB) 0-87168-214-X, (PB) 0-87168-226-5.

This report is essential reading foreveryone concerned with the seriousproblems we face in meeting theworld's need for food. A provocativereassessment of the worldwide foodcrisis of the last three years and arealistic look at our options for thefuture.

Partial Contents Listing

The Great Food Fumble: F. H. SandersonWorld Food: A Perspective: T. T. PolemanInstitutional Obstacles to Expansion of

World Food Production: P. R.Crosson

Difficult Issues Underlying Food Problems:H. Walters

U.S. Agribusiness and Agricultural Trends:J. Walsh

Energy Use in the U.S. Food System: J. S.Steinhart and C. E. Steinhart

Weather Variability, Climatic Change, andGrain Production: L. M. Thompson

India: A Perspective on the Food Situation:J. D. Gavan and J. A. Dixon

Agriculture in China: G. F. SpragueHuman Milk, Nutrition, and the World Re-

source Crisis: D. B. Jelliffe andE. F. P. Jelliffe

Nutrition and Infection in National Devel-opment: M. C. Latham

Beyond Economics and Nutrition: TheComplex Basis of Food Policy: J. T.Dwyer and J. Mayer

Management of Femine Relief: J. MayerFood Production: Technology and the Re-

source Base: S. H. WittwerInternational Agricultural Research: N. WadeRice Breeding and World Food Population:

P. R. JenningsFood Science in Developing Countries: N. L.

Brown and E. R. PariserSoils of the Tropics and the World Food

Crisis: P. A. Sanchez and S. W. BuolFood Production and the Energy Crisis:

D. Pimentel et al.

Prospects for High-Frequency Irrigation:S. L. Rawlins and P. A. C. Raats

The Ganges Water Machine: R. Revelle andV. Lakshminarayana

Shrubs-A Neglected Resource of AridLands: C. M. McKell

Pest Management: R. L. Giese, R. M. Peart,R. T. Huber

Our Vanishing Genetic Resources: J. R.Harlan

Genes Conferring Specific Plant Disease Re-sistance: K. W. Shepherd and G. M. E.Mayo

Plant Cell Cultures: Genetic Aspects of CropImprovement: P. S. Carlson and J. C.Polacco

Improving the Efficiency of Photosynthesis:I. Zelitch

Nitrogen Fixation Research: A Key toWorld Food?: R. W. F. Hardy andU. D. Havelka

Adaptation of Photosynthetic Processes toStress: J. A. Berry

PRICE FOR EACH COMPENDiUM: Retail: $12.95 casebound, $4.95 paperboundAAAS members: $11.95 casebound, $4.45 paperbound

Remember to watch for the MATE-RIALS COMPENDIUM, scheduled forpublication in May. In it, the country'sforemost authorities will talk aboutthe implications of national policies,energy constraints, and environmentalconsiderations on materials productionand use. Essential reading for everyoneconcerned with materials issues andtheir import for the health of indus-trial economies, the future of materialsresearch, and, ultimately, the qualityof life.YOU CAN HELP! We hope our

compendium series will serve as a use-ful source of information on importantissues of science, and we welcome yoursuggestions on topics for future vol-umes in the series. Take a few minutesof your time to share your ideas withus. Send them to AAAS PublicationsDepartment, 1776 MassachusettsAvenue, N. W., Washington, D.C.20036.30 APRIL 1976

ORDER FORM

Please send me the following compendium volumes.ENERGY POPULATION FOOD

Casebound copies - Casebound copies - Casebound copies

I - Paperbound copies Paperbound copies Paperbound copiesPRICE FOR EACH COMPENDIUM:Retail: $12.95 casebound, $4.95 paperboundAAAS members: $11.95 casebound, $4.45 paperboundO Check enclosed (payable to AAAS) EJ Please bill meE Please send me information on standing orders for the compendium series.Remittance must accompany member orders.

Name

A ddrev.s

Mail to:AMERICAN ASSOCIATION Dept. GFOR THE ADVANCEMENT 1515 Massachusetts Avenue, N.W.,

I OF SCIENCE Washington, D.C. 20005423

- - Who knows about it?No one expert knows all its complexities.But many experts know many different aspects.You have to bring the experts together toget the whole story.

During interviews with science journalists Barbara J. Culliton and WallaceK. Waterfall, 19 recognized authorities provide some thought-provoking newideas as well as an overview of current progress in cancer research, therapy,and rehabilitation such as:

* The psychological impact of cancer onpatients, families, physicians and thepublic.

* Facts and fallacies about cancer's warningsignals.

* Crucial factors in diagnosis.* New progress in tailor-made therapy.* Why the statistics are so grim.* Where basic research is leading.

These and many more cancer topics are covered in four one-hour cassettes.Each attractively-bound, book-style album also contains a 40-page bookletwhich summarizes the tape-recorded interviews.To hear what medical science knows about cancer and the directions it istaking toward new knowledge, order your CANCER audiotape album now.Or, order a copy of the CANCER booklet alone.

. - - _ - _-.__ -_

I ORDER FORM ICANCER AUDIOTAPE ALBUM CANCER BOOKLET I

Ol $49.95 Retail E] $2.50 Retail I

[1 $44.95 AAAS members El $2.00 AAAS membersI O Check enclosed (Payable to AAAS) El Bill me ($2 handling charge) II Prepaid orders are postpaid in the U.S. (Please allow 6 to 8 weeks for delivery) I

Please send me CANCER audiotape album(s) (includes booklet) for_ each

Please send me __ _ CANCER booklet(s) (without album) for per copy I

Name: I

Address/Box No.:

City, State, Zip: I

I Mail to: American Association for the Advancement of ScienceI Dept. C-1., 1515 Massachusetts Avenue, N.W., Washington, D.C. 20005

.___ ___I

30 APRIL 1976 425

A New Vorld of

MaterimalIs:Renewable andNonrenewableResourcesEdited byPhilip H. Abelsonand Allen L. Hammond

An important exploration of the new set of realities affectingthe flow of raw materials-a probing of the incrpasing demandfor them and the obstacles to their discovery and production.

A reliable flow of raw materials has been the fundamentalfactor in the health of the American economy and of theeconomies of all other industrial nations. While economicgrowth has begun once again in the United States and, moreslowly, in Europe, it is predicated on a whole new reality ofmaterials dramatically different from that of a decade ago. Nolonger can an abundance of basic commodities be taken forgranted, and no longer can the supplying of any commodity beassumed continual. We have learned that the flow of existingmaterials is vulnerable to interruption by financial shifts,increased nationalization of foreign-owned properties,restriction of access to resources on public lands, and a host ofother considerations born of the 1970's. In the development ofsubstitute materials we must hurdle these obstacles and alsoadhere to new regulations for environmental protection.

In February 1976 Science devoted an entire issue to a criticalin-depth look at these and related problems. The special issuecontained 24 papers written by some of the country's foremostauthorities. Thirteen more articles created by other, equallydistinguished authors were added to the list, and the total isbeing published as a compendium to provide a meticulouslook at Materials: Renewable and Nonrenewable Resources.The compendium's authors probe the implications of

national policy, energy constraints, environmental

ORDER FORM:

Please send me copies of your latest Compendium Materials:Renewable and Nonrenewable Resources.

El Casebound, @ $12.95 retail, $11.95 for Members (prepaid).II Paperbound, @ $4.95 retail, $4.45 for Members (prepaid).

El Check or Money Order payable to AAAS enclosed.

El Please bill me. (Remittance must accompany all orders under $5.00.)(Please allow 6 to 8 weeks for delivery)

considerations on materials production and use, theperspectives in needs and supplies of resources, hightechnology materials, and renewable and reusable resources.They examine those materials issues most vital to industrialeconomics, the future of materials research, and the effect ofthe new realities on the quality of life.The result is rare and refreshing-a detailed study which

yields an identification of critical problems as well as theauthors' consensus that, in principle, these problems aresolvable. This overview must be studied by those involved inmaterials problems today, by those reaching for answers, andby all of us who will benefit from the solutions. Don't miss thisvital collection of papers. A brief sampling of thecompendium's contents reveals the importance of studyingand dealing with these new realities.

Papers in the Compendium include"Materials: Some Recent Trends and Issues"-Hans H.Landsberg

"The Age of Substitutability"-H. E. Goeller and Alvin M.Weinberg

"Forest Resources: An Overview"-James S. Bethel and G. F.Schreuder

MAIL TO:

5jffiB- American Association for the Advancement of ScienceDept. M-1., 1515 Massachusetts Avenue, N.W.,Washington, D.C. 20005

Name

Adaress

-StateCity430

-in

SCIENCE, VOL. 192