SQUEEZE TYPE
Polyethylene WASH BOTTLES* UNBREAKABLE
LIGHTWEIGHT. FLEXIBLE
* CHEMICALLY RESISTANT* VENTED TO PREVENT
DRIPPING* FITTINGS SOLD SEPARATELY
9823-E.
WASHING BOTTLES, Squeeze Type, Polyethylene. Ofchemically resistant pure polyethylene, flexible, tough,lightweight and practically unbreakable. Squeezing pro-duces a steady, controllable stream or a few drops, as de-sired~, with delivery stopped instantly when pressure is re-leased.
This formulation is inert to distilled water, buffered,acidic or alkaline wash solutions and is not significantly 9823-_F.attacked by corrosive solutions such as concentrated Hy-drogen Peroxide, but is not recommended for use above7O' C or for volatile organic solvents.Both screw cap and delivery tube are of polyethylene.
Delivery tube has carefully formed tip and screw cap has d_ia small vent to prevent dripping caused by overpressureresulting from rise in room temperature.9823-E. Washing Bottles, Squeeze Type, Polyethylene, as above
described complete with vented screw cap and deliverytube.Capacity, ounces ........ 4 8 16Diameter of bottle, inches 1 7/8 24/ 4 3Each ..76 .89 1.05Per dozen .8.19 9.60 11.32
9823-F. Fittings, only, of polyethylene, consisting of vented screw cap and bentdelivery tube. For conversion of stock polyethylene bottles intoWashing Bottles.To fit Bottle, oz. ................ 4 8 or 16Cap size No. .............. ...... 2428Each ............................. .52.52Per dozen ....................... . 5.60 5.60 9823-F.10% discount from "dozen" price in assortments of 144 or more. Method of Packaging.
ARTHUR H. THO MAS CONMPANYLABORATORY APPARATUS AND REAGENTS
WEST WASHINGTON SQUARREPHILADELPHIA 5, PA.
Telotype Service: Wstern Union WUX and Boil System PH-72
I
announcinga new book!
Krueger's Principles of Microbiology
This new book for introductory courses in general microbiology orbacteriology, accurately brings the basic principles, concepts andviewpoints of the subject into sharp, clear focus. In a refreshingstyle of writing, the author covers the field of microbiology withoutplacing particular emphasis on any special branch of the subject,and keeps discussions abreast of all modern developments.The text is divided into nine parts. Parts 1 to 3 cover the
biology of bacteria-the latter part discussing enzymes and their role in microbial activities;the nutrition and respiration of microorganisms; environmental factors affecting their growth;and bacterial heredity and variability. After these divisions have been studied, the sequence oftreatment may be altered at the discretion of the instructor to suit his own plan of presentation.Part 4 explains microbiologic techniques and methods-laboratory study and culti-vation of microorganisms, inhibition and destruction of microorganisms by chemical andphysical means, and chemotherapeutic agents. The remainder of the book deals withapplied microbiology-soils, fermentations, foods, water and sewage, pathogens and plantpathology.Every effort has been made to provide the necessary background material to aid the studentin future studies. There are helpful study questions at the end of each chapter, and 143 superbillustrations. These illustrations-photographs, photomicrographs and line drawings-increasethe book's usefulness and further clarify the student's understanding of the subject matter.By WALTER W. KRUEGER, Department of Biology, Grand Rapids Junior College. 649 pages, 6" x 8", 143 illus-trations. New!-Ready in April.
W. B. SAUNDERS COMPANYWest Wauhlugft. Squre PhMladelhia 5
April 3, 1953
£
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combines the Welch DENSICHRON
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. Vl 117
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SCIENCE, VOl. 1172
range Write for You7Copy TODA4Y
BIOCHEMICALS, INC.I CHAGRIN FALLS, OHIO
THE RECO DESALTER
A New Item!The RECODESALTER
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SCIENCE, Vol. 1174
I-I_a) TELESCOPE EXTENS AMAZ ING!
USED Double Utility!TELESCCOE Combination15X TELESCOPEand 35X ErectingMICROSCOPE
USED Extra utility by removingAS 35X telescope portion and using asMICRO. 35 power microscope to in-SCOPE spect, dissect, etc. Excellent
v 3h. clarity whether used as tele-scope or microscope. Telescopeobjective lens is achromatic,coated. Telescope ean be re-moved and carried in pocket-focuses from 10 ft. to
infinity. Microscope has 3 element, color corrected objective-image iserect-just as your eye sees it-not upside down as in an ordinarymicroscope. Ramsden eyepiece with coarse or fine focusing. Gives you 3"of wo king distance when used as microscope. This low price is possibleonly because we utilie some very high grade war surplus parts inmanufacturing this fine instrument. Entire unit folds down to 2" x 7"x 10". Telescope Instantly adjustable in height from 3" to 14".Stock No. 70,017-W ......................... $29.50 Postpid
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IMPGR-TED- MtKRGSCOPE100, 200, 300 Power ONLYGood optical qualities. Fine focus- eflflIng. Cretainly not the equal of a fl*lA 7$200 Instrument but definition Is Pstpd.surprisingly clear and good . . . 1 OCUL.in fact amazingly so at this price. 3 OBJECTIVEServiceable construction. The LENSES
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LOOK AT THESE BARGAINS!SLIDE PROJECTOR SETS-Consist of all unmounted lensesyou need to make the following size projectors:Stock #4029-W-35 nmm. ...................... $2.85 Postpaid
Stock #4038-IV ......... 21/4" x 2-14".$.35 Postpaid
SO MUCH for SO ITTLE!SIMPLE LENS KITS! Kits include plainly written, illus-trated booklet showing how you can build lots of opticalitems. Use these lenses- in experimental - opties. buiding.TELESCOPES, low power Microscopes, etc.Stock 2-W-10 lenses ....................$ 1.00 PostpaidStock # 5-W-45 lenses .................... $ 5.00 PostpaidStock #10-W 0 lenses .................... $10.00 Postpaid
NON-ABSORBING BEAM-SPLITTING MIRROR - Latestdevelopment! Optically flat to 1,4 wave length. Size:1-15/16" x 2-15/16"-%"' thick. Reflects approximately 50%and transmits approximately 50%. No light is absorbed.Has a three-layered film which accomplishes non-absorption.
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First time available at such low price! EDSCORPPOCKET COMPARATOR. Fine, imported measuringmagnifier - for fast, accurate inspection of intricateparts without expensive equipment. Used to checklayouts, machining on tools, dies, gauges -to checkthreads, chamfers, small holes. In optical work f r
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M ICROSCOPEEYE-PIECES
Imported! Will fit any standard micro-scope. Value $5.00 to $25.00.
Stock #
30,039-W30,040-W30,041-W30,042-W30,043-W30,044-W
Pewer
5X8X
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$3.75 Pstd.3.75 Pstpd.3.75 Pstpd.4.00 Pstpd.
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MICROSCOPEOBJECTIVES
Imported! Achromatic will ft anystandard microscope. Packed in con-venient, screw-top plastic tube. Ex-cep. value.
Stock # Power Price
30,045-W 5X $4.00 Pstpd.30,046-W loX 10.00 Pstpd.30,047-W 20X 12.00 Pstpd.30,048-W 40X 16.00 Pstpd.30,049-W 60X 24.00 Pstpd.
30,050-W 1OOX(oil immersion) 32.00 Pstpd.
30,051-W 1lo0X(oil immerlon
with Iris Diaph.) 60.00 PstPd.
PREPARED MICROSCOPE SLIDE SETS 10 Slides in Set-Standard Size
Stock No. 40,006-W Vegtables ...... ............ (Per Set) $2.50 P.P.Stock No. 40,007-W Animals ....... ............. (Per Set) $2.50 P.P.
Stock No. 40,008-W Micro-Organisms .... ......... (Per Set) $3.00 P.P.
EYE-PIECE MICROMETER-Imported! 19 mm. diameter. 10 mm. scale dividedinto 100 parts. Val. $5.00.Stock #30,035-W ..... .................... $3.50 Pstpd.STAGE MICROMETER-Importedl Rectangular glass slide with photographicseale 1 mm. long divided into units of 0.01 mm. Val. to $10.00.Stock #30,036-W ..... .................... $4.00 Pstpd.REVOLVING NOSEPIECE-Importedl Triple and quadruple. For Standard sizemicroscopes and objectives._
Stock #30,037-W ... Triple ...$11.00 PstPd.Stock #30,038-W ... adrapi. ... $13.50 Pstpd.
IF YOU'RE INTERESTED IN ORTICAL BBARGNAINSo Send Chock or M. 0.1"te for FREE CATALOG W f . ' or *. Satisfaction GuaranteedwnIe ILr a r Sol* at I-
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TiltersMULTILAYER:-Bandwidth gen-erally less than 70 A. Peak trans-mission above 70%. Suppliedfrom stock for mercury green at5461 A, sodium D at 5890 A,hydrogen alpha at 6563 A, andlithium red at 6708 A, with var-iance from +30 A to -10 A.Available on longer delivery atmost wavelengths in the visibleregion. Provided in 2" and 1"squares, at $50 and $30.
Typicol transmission curve of a Multilayer Interference Filter
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STANDARD:-Bandwidth approximately 150 A.Peak transmission from 5% to 35%, dependingon wavelength. Stocked for most wavelengths from3300 to 10.000 A, with peak variance of 5S0 A.Provided in 2" squares, at $25.
BIREFRINGENT: - Custom-built filtersof the birefringent type are available on
special order, to bandwidths as low as 1Angstrom. Prices on request.
SCIENCE, Vol. 117
FOR DISTI IN AT HIGH VACUUM
WITHOUT DAMAGE
To MOIECUIAR STRUCTURE!
A simple, precision-built, high-efficiency unit whose normal fieldof distillation is among materialswhose molecular weights areabove 250, except for materialsof extreme heat sensitivity suchas some of the vinyl monomers.
* More economical than having processes done byoutside laboratories.
* Either a concentrated residue or a derived distillatemay be obtained.
* Simple in operation; easily controlled. Junior person-nel can fractionate successfully and speedily aftera few hours of observation and instruction.
* Preliminary passes can be made to remove water, air,and high or low boiling-point fractions.
* Almost no supervision or adjustment required otherthan initial setting of rate of flow, degree of vacuum,and temperature.
* Flasks (removed in a few seconds) are fluorescent-lighted from below so that contained liquids can bechecked for color, clarity, etc.
* No installation problem-merely plug into a standardelectrical outlet and connect apparatus to a cold-water faucet by means of rubber tubing.
Pumps, heating elements and dry-ice cooling unitsare of standard make, instantly accessible, andeasily replaceable. Weighs only 210 lb.-fittedwith casters-moved easily to wherever it is needed.
WRITE FOR BULLETIN 2238-K
Manufactured by Asco Mfg. Co., Webster, N. Y.SOLD ONLY BY
AMERICAN INSTRUMENT COMPANY, INC.
AMERICAN INSTRUMENT COMPANY, INC.Silver Spring, Maryland * In Metropolitan Washington, D. C.
April 3, 1953
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Aminco-Stern universal re-search model for large out-put and a wide variety ofsample volumes.
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Ask for our newcomplete catalogue
SCIENCE, Vol. 117
Recent Publications
CARNEGIE INSTITUTION OF WASHINGTON1530 P Street Northwest
Washington 5, D. C.Piibl.No.594 Smith, A. Ledyard, and Alfred V. Kidder.
Excavations at Nebaj, Guatemnala. WithNotes on the Skeletal MIaterial, by T. D.Stewart. 1951. Quarto, vii + 90 pp., frointis-piece, 90 figs. Paper, $5.25; cloth, $6.00.
597 Longyear, John M., III. Copan Ceramnics: AStudy of Southeastern Maya Pottery. 1952.Quarto, xiii + 114 pp., 118 figs., 3 maps.Paper, $5.25; cloth, $6.25.
Year Book 51, July 1, 1951-June 30, 1952. Reportson curreilt research from all the departmentsof the Institution. 1952. Octavo, xxxv + 20 +286 pp., 3 pls., 12 figs. Paper, $1.00; cloth,$1.50.
Subject lists in archaeology and anthropol-ogy; astronomy and astrophysics; botany, ecology,and climatology; chemistry and physics; embryol-ogy, genetics; geology and geophysics; history,economics, and history of science; literature;mathematics; mediciue; nutrition; paleontology;and zoology, or a complete catalogue will be sentupon request. Orders may be placed direct orthrough regular dlealers.
IL!!.:- I
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Images up to 10 feet acrosseven under oil-immersed objectives
Because of the virtually solar intensity of the Scopi- , ;con's high-pressure mercury arc, you can project sharply Thdetailed images up to ten feet across even under oil- t .te@dy -immersed microscope objectives. The light's white color neith* w dsedemonstrates the various biological stains to their best *Ickms.advantage.
The Scopicon is highly adaptable-can be usedwith equal convenience for small-group study in a nor-mally lit room, or for exhibition to large groups in adarkened auditorium. Let us send you the brochuredescribing this versatile instrument.
The Scopiconhigh-pressuremercury arc
CAS p _ ~~~~~~~~~~~~~~~~~lamp.
micro-projection equipmentCOPICON, Inc. 215 E. 149th ST. NEW YORK S1, N. Y.
9April 3, 1953
FUNDAMENTALS OF PHYSICAL SCIENCEBy Konrad Bates KrauskopfStanford University
New Third Edition694 pages, $6.00
In order to maintain a completely contemporary outlook and keep abreast of all recent advances, theauthor offers a fine revision of this excellent and extremely successful physical science survey text.Intended for the non-science student, it provides a thorough coverage of the main facts of astronomy,physics, chemistry, and geology.
These four fields are all treated from the point of view that they are parts of a unified gen-eral field of knowledge rather than stressed as distinct subjects. Superficiality is wholly averted throughselection of certain key topics of emphasis, then development of these topics with a rigor compar-able to that used in elementary courses in the specialized sciences. Throughout, it is principle ratherthan application which is stressed, for it is the author's intent that through knowledge of scientificmethods, the student will learn what a scientific problem actually is and the manner in which a scien-tist achieves solution.
In the revision, primary material on atomic nuclei, atomic energy, cosmic rays, andthe earth's interior have been brought up to date, and other, more minor revisions make the bookcomplete in modern methodology. New sections have been added, furthermore, on electronics, sili-cones, and recent theories about the origin of planets. Most of the half-tone illustrations are replacedfor great improvement, and new problems have been added.
The test is designed for great flexibility. Sections not essential to continuityhave been printed in smaller type, making the book adaptable to courses of differing lengths and varyingdegrees of difficulty. To further this convenience of teaching and presentation, problems which referto these less essential sections are marked with asterisks.
Here then is an excellent text to provide the student with ageneral understanding of the vital importance of science to the age in which we live, and to indicatethe manner in which it functions. The book is also of value to the student of specialized science forreview and background material in related fields.
Send for copies on approval
McGRAW-HILL BOOK COMPANY, Inc.330 West 42nd Street New York 36, N. Y.
SCIENCE, Vol. 11710