"Check your air, Sir?"

4 He's checking the air pressure in a branch cable, one ofscores serving a town. The readings along the cable areplotted as a graph to find low-pressure points wniich indi-cate a break in the protecting sheath.

To keep voices traveling stronglIr through telephonecables. you have to keep water out. This calls for speedin locating and repairing cable sheath leaks -a hardjob wvhere cable networks fork and branch to serve everyneighborhood and street.

At Bell Telephone Laboratories, a team of mechanicaland electrical engineers devised a way to fill a complexcable system with dry air under continuous pressure.Pressure readings at selected points detect cracks orholes, however small. Repairman can reach the spot Master meters keep watch over the various cablebefore service is impaired. networks which leave a telephone office in all

directions to serve a community. Air enters the

It's another example of how Bell Laboratories w%orks system at 7 pounds pressure, but may drop to 2pounds in outermost sections-still enough to

out wvays to keep your telephone service reliable - and keep dampness out.to keep down the cost to you.

IoBELL TELEPHONE LABORATORIESImprovina telephone service for America provides careers for creative men in mechanical engineering

Air compressor and tank are at right. Long cyl-inders on rack dry air before it enters cables.

- .--,a --- --- -- I-- -, ---- --

new (6th) edition!. . . E

McLESTER and DARBY on

I ,

Iin

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The wide and very real usefulness of thisbook is evidenced by the emergence of thisNew (6th) Edition. Only books that fill aneed and fill it well survive to such a rare andhealthy maturity. Thoroughly revised, it re-tains its reputation as the text of authorityon all problems of nutrition.

This is really two books in one-Nutritionin Health and Nutrition in Disease. The sec-tion on Nutrition in Health is especiallyworthwhile because of its discussion of Vita-mins-the most complete to be found in anytext today. The roles of vitamin B12, B6, andthe folic acid group; the necessity for aminoacids; the interrelation between acids and vi-tamins-all of these subjects have been in-cluded. Suggestions on dietar-y requirementsfrom infancy to old age are also given.

The section on Nutrition in Disease is high-lighted by information on deficiency dis-

eases, diabetes mellitus, food poisoning andallergy, nutrition in surgery and endocrinedisorders. Of course, therapeutic diets aregiven for all of these conditions (includingelimination diets).

In addition, there is highly useful informa-tion on water balance in relation to nutrition,obesity and leanness. Diet therapy in rheu-matoid arthritis and in various skin dis-orders is discussed, and there is a thoroughexplanation of the low-salt diet in congestiveheart failure.The authors have left nothing undone in thisrevision. "Nutrition and Diet Therapy" willpay for itself many times over in betterdietary planning and management.

By JAMES S. MCLESTER M.D., Professor of MedicineEmeritus, University of Alabama; and WILLIAM J. DARBY,M.D., Ph.D., Professor of Biochemistry and Director of theDivision of Nutrition, Vanderbilt University. 710 pages,6" x 9". $10.00. New (6th) Edition.

W. B. SAUNDERS COMPANYWest Washington Square Philadelphia 5

March 6. 1953 I

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SCIENCE, Vol. 1172

forRA A

SAMPLE COUNTINGUnusually versatile in use, nuclears "Roto-Matic" Model C-110 Automatic SampleChanger is designed with simple mechani-cal operation for reliability and long oper-ating life. This compact changer (14"x 15')uses minimum bench space, yet carries upto 50 samples at one time. Any number upto 50 can be counted, the cycle repeated,or background count recorded. There isno time lost with blank positions. Allsamples are counted while fully shieldedby 2' of lead.

Model C-110 operates with any scalerbecause it incorporates eight preset countsettings. It may also be controlled by a pre-set time or preset count scaler, or will pro-

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Heart of the "Roto - Matic" sample changeris the simple three-position "Auto-load"turntable which selects a sample, places itin counting position within the shield, andloads it into the storage sample magazinewhen the count is completed. Both samplemagazines are clear plastic so that progresscan be easily observed. Expendable samplecarriers and the chrome-plated turntablemake decontamination easy if necessary.

Model C-110 Automatic Sample Changeris available on good delivery. Write fordetails today.

nuclear INSTRUMENT & CHEMICAL CORPORATION237 West Erie Street Chicago 10, Illinois

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SCIENCE, Vol. 1174

0 - - - - -0

is important in the purchase

of laboratory ware, too!

DOUBLE ECONOMY-PYREX® test tubes are actually lower in cost asthey outlast other brands on a service for service basis. 22 standard sizesfrom 10 x 75mm. to 65 x 500mm. enable you to meet every requirement.

One thing you've got to give the squirrel, helooks out for himself as a matter of instinct.As a matter of experience, educators know

PYREX® laboratory ware to be the answerto real classroom economy. And for a verygood reason. The extra durability of PYREXapparatus withstands the abuse it so oftengets in inexperienced hands.

Records maintained by 49 high schools, for

example, show that PYREX brand test tubesoutlast other brands as much as 2 to 1! Theanswer? Greater resistance to both thermal andphysical shock plus chemical inertness in thepresence of acids and many alkaline solutions.

So here is one way you can stretch your1953 budget . . . specify PYREX laboratoryware for all of your requirements.Your labora-tory dealer stocks it for you. Call him anytime!

*'% the laboratory glassware that gives you economy, accuracy, durability

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It's the patented Technicon syphon-cycle that does it. Twice everyminute, seven fresh gallons of water are surged through thepipettes, loosening and dislodging clinging residues. Wastes areliterally swept out by the violent suction set up during the briskten-second emptying phase of the cycle.

So rapid, so thorough is the Technicon Washer that six flushingcycles will deliver a full basket-load of immaculately clean pipettes(it holds up to 200 pipettes, 1 ml, 18" long). The non-corrodingstainless steel basket carries its load of pipettes without changingthrough cleansing, washing and drying. Practically eliminates break-age and chippage because it requires no individual handling, noshifting from container to container. A MUST for the busy labora-tory. Ask for Bulletin 6150 giving particulars,

autonatic pipette sher

THE TECHNICON COMPANY, 21 5 EAST 149th ST., NEW YORK 5 1, N. Y.

SCIENCE, Vol. 117

1A gij gi IIA' A1I I~~~~~~~~~

600 POWER

IMPORTED MICROSCOPEYou Can Add Other Accessories

This unusual low-price instrument willtake standard objectives and eye-pieces.Thus you can add varied-power objectivesand eye-pieces, plus other standard sizeaccessories. You can add our triple orquadruple nosepiece, mechanical stage andIris diaphragm. Pu-rchase these accessoriesover a period of time-build up to a fine.ultra high-power instrument. If interestedin this project, write for MICROSCOPEBULLETIN W. In any event, your firststep is to purchase the basic 600 PowerMlieroscope an outstanding value worth

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IMPORTED MICROSCOPE100, 200,300 Power ONLY

Good optical qualities. Fine fousing. $1 195Certainly not the equal of a $200 in- f htpdtrument-but definition is surprisingly 1 OCULAR

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at this price. Serviceable construction. LENSESrhe greatest microscope bargain on the RACK &

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TRY IT FOR 10 DAYS . . . if you're REVOLVENGnot completely satisfled your money will DISC-LIGHT

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Instrument comes packed in sturdy, hard SQ(2"R swood case. 2-5/8") with

SLIDE CLAMPSStock Mo. 70 -W..... $14.95 Pospaid

IOOK AT THESE BARGAINS!SLIDE PROICECQR ZT*-Coupsist of All nurounted lensestbu need to make the following s1i6 projectors:

$2........... -2;85 PostpaldSotocek #~4=168Z-W.. 2- 'A"xr 2'1A".......P.35 Postpaid

SO MUCH for SO LITTLE!SIMPLE LENS KITS! -Kits include plainly written, illus-trated booklet showing how you can build lots of opticalitem-s. Use these lenses in experimental optics, buildingTXELE4OPNS, hlw power Microscopes, etc.tock W-10 len ..................... $ 1.00 Postpaid

Stock *5-W--1 lense s-...................... s5.00 Postsid

MICROSCOPEEYE-PIECES

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scope. Value $5.00 to $25.00.

Stock #30,039-W30,040-W30,041-W30,042-W30,043-W30,044-W

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MICROSCOPE. OBjECTIVES

Imnported! Achromatic I Will fit anystandard microscope. Packed in cnn-venicnt. screw-top plastic tube. Ex-

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Stock # Power Price

30,045-W 5X $4.00 Pstpd.

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PREPARED MICROSCOPE SLIDE SETS 10 Slides In Set-Standard Size

Stock No. 40,006-W Voetables .... .............. (Per Set) $2.50 P.P.

Stock No. 40,007-W Asimals .... ................ (Per Set) '$2.50 P.P.

Stock Ne. 40,00-W Mlere-Oais ... ........... (Per Set) $3.00 T.P.

Stock W.lOW-480 len15 ...................... $10.010 Postpaid EYE-PIECE MICROMETER-Importedl 19 mm. diameter. 10 mm. scale divided

into 100 parts. Val. $5.00.

NON-ABSORBINqG BEAf-SPLITTING MlBROR - Latest Stoc #30 035-W .................................... B3I50 PstpI.developmnAhtl Optically flat to 'A wave length. Size: STAGE UICROMETE--Importedl Rectangular glass slide with photographic1-15/16" x 2-15/16-%" thick. Reflects approximately 50% scale-1 mm. long divided into units of 0.01 mm. Val. to $10.00.and transmits. approximately 50%. No light .13 absorbed. -Stock #30,036-W ......... .. $4.00 Pstpd.Has a three-layered film which accomplishes non-absorption. REVOLVING NOSEPIECg-Importedl Triple and quadruple. For Standard si8

St4ck #567-W ....... ........... $5.00 Postpaid microscopes and objectives.

/) E -- Stock #30,037-W ... Triple ..... $11.00 Pstpd.\ { Stock #30,038-W .... Radruple ... $13.50 Pstpd.

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March 6, 1953

IMPORTED! 50 POWER POCKET MICROSCOPEAll Metal!Powerful!Only

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7

A. H. T. CO. SPECIFICATION

STOPCOCK TENSION CLIPSFor INSTANT attachment to, or removal from, practically

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3291-B. Fig. 2.Rear view, showing spring opposed jaws.

3291-B. Fig. 1.Method of attachment to, or removal from,

Van Slyke Blood Gas Apparatus.

STOPCOCK TENSION CLIPS, A.H.T. Co.Specification, (Patent applied for). Of Stainlesssteel, for pressure-tight seating of practically anytype stopcock with groove for rubber washer atsmall end of plug.Can be attached instantly by compression of the spring

combined with thumb and finger pressure on the narrow

flanged sides. Can not work loose, but can be removedinstantly. Recommended for glassware which requireshand or mechanical shaking such as Van Slyke Apparatus,Separatory Funnels, etc., and to improve the efficiencyof stopcocks on Burettes, Gas Analysis Apparatus, etc.Clip does not interfere with normal manipulation of thestopcock handle.

3291-B. Fig. 3.In position on Burette Stopcock.

3291-B. Stopcock Tension Clips, as above described. For satisfactory use, the stopcock on whichClip is used must be furnished with a plug with groove so placed that its distal edge isat least 1/16-inch beyond the stopcock shell.Maximum jaw diameter, mm .................... 1 1 16 19

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SCECE.ol 1J-

8 SCIENCE, VOl. 117

"An excellent book far better than any covering thesame material with which I am-acquainted. It is up-to-date, well presented and there is enough modernmaterial to make it attractive. If I were to write a textI would aim at approaching the-same standard ofexcellence."

CECIL T. LANEProfessor, Physics Dept.,Yale University I

The above quote is typical of what professors are saying about

PHYSIlCSFor Science And Engineering Students

by W. H. Furry, E. M. Purcell and J. C. StreetAll of Harvard UniversityOther professors add:"I am favorably impressed by Dr. Purcell's emphasis upon fun-damental physical laws rather than upon details and I like histreatment of modern physics, particularly Quantum Theory andCosmic Theory."-An Ohio Professor

"In this book the amount of coverage and the obvious emphasison principles useful in modern physics are surprising. Forexample, I don't recall any elementary text which discussesgroup velocity or which uses Fermat's Principle. The sectionsand chapters dealing with quantum theory, atomic physics and

cosmic rays are so well written that I want the students in my intermediate course in atomicstructure to read them as a preface to that course."-A Missouri Professor

PHYSICS - For Science and Engineering StudentsBv Furrv. Purcell and Street 800 Illustrations, 694 Pages $6.50 I

THE BLAKISTON COMPANY575 Madison Avenue 105 Bond Street Toronto 2, CanadaNew York 22, N. Y.PLEASE SEND ME

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Typical transmission curve of a Multilayer Interference Filter

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39 UNIVERSITY ROAD CAMBRIDGE 38, MASS.

GENERAL BIOCHEMICALS, INC.l 60 LABORATORY PARK * CHAGRIN FALLS, OHIO

SCIEN-'F, Vol. 11710

:7-.r,,rlz

gives Industry the Answers to Better Methods and Products

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