July15,1949,Vol.110 SCIENCE 11~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SPECTROSCOPIC PROPERTI ES OF URANIUM COMPOUNDSBy G. H. DIEKE, The Johns Hopkins University; and A. B. F. DUNCAN, University ofRochester. National Nuclear Energy Series. Special Separations Project. Division III.Volume 2. 281 pages, $2.75

Represents what is probably the most comprehensive study of the spectroscopic properties yetmade for any one group of related solid compounds. Correlation of absorption measurementswith those obtained from fluorescence spectra have seldom been made in the past for such a

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IONIZATION CHAMBERS AND COUNTERS: EXPERIMENTAL TECHNIQUESBy BRUNo Rossi, Laboratory for Nuclear Science and Engineering, and Massachusetts In-stitute of Technology; and H. H. STAUB, Stanford University. National Nuclear EnergySeries. Los Alamos Project. Division V. Volume 2. In press

Part I of this book discusses the general physical principles underlying the operation of ioniza-tion chambers and counters, with special emphasis on subjects that are of importance in moderndetection techniques and have not been discussed in previous textbooks. Part II contains a

detailed discussion of a number of detectors developed by the authors and others at the LosAlamos Laboratory for the study of different kinds of radiations.

THE SCIENCE OF CHEMISTRYBy GEORGE W. WATT and LEWIS F. HATCH, University of Texas. 566 pages, $4.50

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16 SC(ENCE July 15, 1949, Vol. 110~~~~~~~~~~

VOLUME XVIIIANNUAL REVIEW OF BIOCHEMISTRY

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he Instrument for ANY Colorimetric Test-the Rouy'hotrometer is pre-calibrated for the 38 most commonlyequired clinical tests and can be calibrated for any test-ientifically suited to colorimetric technique.

No Standards ... No Calculation-Pre-calibration andan Individual Handbook eliminate any need for calculationor preparation of standards. Accurate reagents are quicklyavailable through the Leitz Solution Supply Service.

Performance Proved -Photrometers and Leitz Colori-meters are now serving more than 8,300 satisfied users.Each instrument is made to exacting standards of pre-cision and sturdiness by Leitz, first large-scale producerof photoelectric colorimeters.

Pre-calibrated for 38 tests-$257.80Pre-calibrated for 22 tests-$182.80

For information, write E. LEITZ, Inc., 304 Hudson Street, New York 13, N. Y.

LEITZ SCIENTIFIC INSTRUMENTS . MICROSCOPES * BINOCULARSLEICA CAMERAS AND ACCESSORIES

ATTACHED ILLUMINATORfills field at various powers with-out refocusing condenser andpermits inclination of micro.scope without disturbing illu.mination.

A IMPROVED SUBSTAGEALIGNMENTpositive locking device assuresaccurate optical alignment.NEW, N.A. .25, 10XDIVISIBLE OBJECTIVEwith cut-away boot-permitsbetter oblique top lighting.NEW FINE ADJUSTMENTball-bearing, micrometer screwtype-accurate 2 micron grad.uations-comfortable loweredposition."PINCH GRIP" SLIDEHOLDER

provides for inserting slideseasily without disturbing staget ,.,gsettings.ADJUSTABLE TENSIONsubstage and coarse adjustment

controls may be adjusted tosuit individual preference.INTERCHANGEABLE BODIESEASY TO CARRYlighter weight-twice as rigidas previous models.DUST SHEDDING DUAL-CONE NOSEPIECEwith new positive ball-and.groove stop.NEW INCLINATION JOINTLong wearing-bearings auto-matically compensate for wear.

American Optical CompanyScientific Instrument Division

Buffalo 15, New York

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