mass demonstration in the auditoriumThe projectionist can follow a specimen through a progres.sive series of ever-closer localizations, from its gross aspect

to its ultimate microscopic demonstration under oil-immersion

A..

The auxiliary Scopicon dark-chamber "round-table"

affords superb facllity for small-group study.

Here the projected image is cast upon a platen

within a light-tight chamber, with separate light-

excluding viewing hoods for each observer. Any

number up to ten may share in conference, which

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cate areas of interest to all the others for discussion.

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theI

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T his fine new SANBORN instrument is designed forthose research and diagnostic groups whose require-

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Introduction of the two -channel Twin -Viso is beinghailed with the same enthusiastic praise as was the Poly -Viso- not only because it too helps answer more recording problems,but because it has the same basic design advantages of the "Poly."Among these are: immediately visible, inkless recording in true

rectangular coordinates; clear, sharp and permanent records; localand remote code marking; and a choice of ten paper speeds rangingfrom 0.5 to 100 mm/sec.

Quick and easy interchangeability of amplifiers and pre-amplifiersmakes possible the availability of a variety of input circuits - whichoffers the user a wide range of two -channel recording possibilities,such as; combinations of 'cardiograph leads; direct pressure record-ings; polygrams; pneumograms; ballistocardiograms; myograms;sphygmograms; phonocardiograms (for timing); and temperaturemeasurements - using, as required, supplementary Sanborn equip-ment or attachments, or "pick-up" transducing and amplifyingdevices which may now be in your laboratory.

For further information, address Dept. S

Established in 1917

CAMBRIDGE 39, MASSACHUSETTSOFFICES IN 33 CITIES THROUGHOUT THE U.S.A.

March 2, 1951 1

Textbook of Organic Chemistry3rd Edition

by E. Wertheim, Ph.D., UNIVERSITY OF ARKANSAS

Consider It For Fall ClassesNew material, references, and teaching aids have been

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958 Pages, 105 Illustrations $5.00

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a new theoretical material throughout on-bond energies,bond distances, inductive effect, electronegativity, electronicmechanism of reactions

fl new reactions-chloromethylation, Clemmensen reaction, Re-formatsky reaction

new literature references-all critically reviewed, many oldones removed

O new questions and numerical problems-added to eachchapter

fl physical constants-checked with latest informationO double bonds placed in all of the benzene and other aromatic

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RESERVE YOUR EXAMINATIONCOPIES NOW! A

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The Blakiston Company, 1012 Walnut Street, Philadelphia 5, Pa.Please send me a copy of Wertheim's "Textbook of Organic Chemistry"-3rd Edition. O Also Wertheim's "Laboratory Guide for OrganicChemistry". _

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SCIENCE, Vol. 113.s

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SCIENCE, Vol. 113

Automatic Tidal Volume RcorderPeck-Wailer

Relieves investigator of constant supervision . . Respira-tory rates of 2-60 per minute, and tidal volume of 25 ccto 400 cc can be recorded.

WRITE:

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Menlo Research Laboratory introduces the new Fluoretor, aportable blacklight instrument weighing only 2 lbs. Ideal formany types of laboratory quantitative and qualitative checks,also on-the-spot glow-fracture testing of materials in factoryor field. Patented dark chamber head permits tests in fulldaylight-or remove to use as wand for examinations indarkened areas. Models for operations from two standardflashlight batteries or 115-v 60 cps power, both with choiceof 2537 or 3650-63 A frequency. Ready to use, in sturdywooden box-portable model $49.50, 115-v $42.00. Inter-changeable head for alternate frequency, other accessoriesavailable. Write for free literature. Dealer inquiries invited.

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March 2, 1951 5

SHARP CUT-OFF FILTERS FOR THE NEAR INFRAREDThe Polaroid Type XRX

Filters developed * for signalingand identification devices arenow available for general use.These filters block the ultravioletand visible light but transmit thenear infrared with an efficiencynot approached by other filters.They are proving increasingly

useful in military and other ap-plications involving infraredspectroscopy, photography,communications, and vision sys-tems employing IR-sensitiveimage tubes, phosphors, leadsulfide photocells, cesium vaporlamps, and the like.

All of the filters are notablysharp and complete in their cut-off. Total visual transmissionslie in the range of o.oooi percent to o.ooooooI per cent.

Through the darker typesthe mid-day sun can be dis-cerned only after substantialdark adaptation. Special var-ieties are available throughwhich the brightest commonsources of artificial light arecompletely invisible, even to thefully dark-adapted eye.

The near infrared cut- offsrange, for the various types, from8ootogoomillimicrons. All filterstransmit to 2.8 microns and theunlaminated filters have an ad-ditional transmission band be-tween 3.5 and 6.5 microns. Theycan be used continuously at tem-peratures of go°C (about 200°F); may be used for short periodsat higher temperatures.

Polaroid infrared filters TypeXRX are stocked as 2-inch

90

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square and 2-inch circularfilters, for laboratory use. Price:$s.oo each in plastic, $7.oo eachin water - white glass. Corre-spondence is invited concerninglarger sizes and large-scale uses.Write Polaroid Corp., Dept.SC4I, Cambridge 39, Mass.U. S. A.

Q.V PO LAROPID

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the s lampmicroscope lamp

SCIENCE, Vol. 113

r-

POLAROID XRX FILTERS

I/ I, Y300 TYPES

P H OTO VO LTExposure Photometer Mod. 200-M

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The Life of J4ertebratesBy J. Z. YOUNG

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Each of the separate studies of em-bryology, anatomy, physiology, bio-chemistry, paleontology, and ecologyis concerned with the same central fact,that life goes on. Professor Young, con-vinced that these formal divisions ofbiology are not acceptable, has com-bined the results of the various studiesin a single volume. This is an under-taking unique not only for its scope butfor the brilliant success with which itsaim has been carried out.

767 pages profusely illustrated $8.50

A Clarendon Press Book

OXFORD UNIVERSITY PRESS114 Fifth Avenue, New York 11

SCIENCE, Vol. 1138

6 REASODIS for using

_~~ ~ ~~P_,R. ID+-t0 : 0ii -0;000 --0:-: 0-XE-W04 tSEPARATORYF N*1*EL

1.Heavy wall bodies

2. Re-enforced seals

3. Precision-ground surfaces

4. Scientific annealing

5. Fire-polished drip tips

6. Heat resistance

The manner in which Corning makes

its Separatory Funnels assures longerservice life. After fabrication, for ex-

ample, they are fully annealed, eliminat-

_!x ing all strains. Accurately ground stop

cocks enable you to separate liquids

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thermal shock. No leakage duringshaking due to precision grinding of

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Pyrex brand Separatory Funnels are

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ml. For prompt, efficient service, callyour nearby laboratory supply dealerMaalbforSeparatory Funnels and other high-

quality Pyrex brand laboratory ware

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Excellent sensitivity.Completely a-c. operated.Has outlet for recorder operation.Internal electronic stabilization.

FEATURESCompact . . . accessible.Fully accessible interior.Comparisons of light intensitiesindicated as decimal percentages.

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SCIENCE, Vol. 113

Since 1919

I

In Recognition of a Job Well DoneWestinghouse fully recognizes the excellent foundation being provided engineeringstudents in many colleges and universities throughout the land.But to speed young engineering graduates in the inevitable transition from theory

to practice, Westinghouse has dedicated a new building ... the Westinghouse Educa-tional Center.Primary purpose of this center is to offer the best facilities possible for the training

and continued education of new employees ... top students from leading engineeringschools. This modern center includes such facilities as an auditorium; classroomsacoustically treated and with modern visual aid equipment; library and magazine room;formal and informal lounges; game, billiard and hobby rooms; facilities for athleticactivities, and a convenient cafeteria.This is but one way in which Westinghouse encourages scientific advancement, in

addition to supporting 42 fellowships, 149 scholarships, 5 professorships, and agraduate study program through which advanced degrees may be obtained fromleading universities by Westinghouse employees. Another important phase of theWestinghouse program is summer research work by selected graduate students, andan industrial experience program for faculty members of engineering schools.In these ways, Westinghouse co-operates with colleges in a common effort to advance

scientific achievement in gll of its aspects. Westinghouse Electric Corporation,Pittsburgh 30, Pennsylvania. G-10136

YOU CAN Si SURE..IF IT'sWestingouseMarch 2, 1951 11

for

SCIENCE andINDUS.TRY

Monochromatic light is becoming increas-ingly important in research and quality con-trol studies. Uses include spectrophotometry,microscope illumination and direct irradia-tion studies. Food industry uses monochro-matic light advantageously in bacteria studies... petroleum industry for oil sand studies.To meet the increasing demand for an illu-minator that will deliver a beam of high in-tensity monochromatic light, Bausch & Lombannounces the new Grating Monochromator,with these important advantages:

* Linear dispersion* Large relative aperture* Extra-wide range (2,OOOA to 1o,oooA,

with a peak intensity in the low U-V)* Low cost

WRITE for complete information and a dem-onstration to Bausch & Lomb Optical Co.,642-4 St: Paul St., Rochester 2, N. Y.

Bausch & lomb a441%"9 Monochromator

SCIENCE, Vol. 113