SCIENCE-ADVERTISEMENTSS

Compact Micro-Projector

HIS new instrument has been designed to meetthe demand for a compact and permanently

aligned Micro-Proj'ector. All optical parts are accu-rately precentered and arc vertically and laterallyaligned. The only centering adjustment necessary onthe part of the user is to bring the light source [eithera Mazda unit or an Automatic Feed Arc Lamp] intoalignment. with the optical axis. This adjustment iseasily made by two screws on the rear of the illumi-nating unit support.The substage is arranged with three condensers and aheat absorbing filter glass. The condensers-onswinging arms-take care of a range of objectivesfrom a 72 mm Micro-Tessar to a 4 mm objective.

May we send descrzptive literature ?

Bausch & Lomb Opt'ical Co.632 St. Paul Street, Rochester, N. Y.

New York Chicago Boston san FranciscoLondon Frankfurt

iX

SCIENCE-ADVERTISEMENTS

BIOLOGIST (Zoologist), Ph.D., 35, five years' graduate studyAmerican universities and Paris, desires new location in Col-lege or University on basis of record of 10 years' successfulteaching experience and constructive service. Experiencedpremedical education a.nd museum work. Member professionalsocieties. Professional success as indicated by appointmentsheld, papers published, unusual references. Interview do.sired. Address "T. N.," Science, 3939 Grand Central Ter-minal, N. Y. City, N. Y.

SCIENTIFIC PERIODICALSWe wish to purchase complete files of Bound and UnboundMagazines such as Journal of Experimental Zoology, Amer-ican Journal of Physiology, Biochemical Journal, as wellas other Scientiflc Magazines. Odd volumes and copies alsointerest.

B. LOGIN & SON29 East 2ISt Street New York

SCHOOL OF MICROSCOPYRoom 1500, Pershing Square Building, New York City,Evening Classes. Course of Instruction includes lectures anddemonstrations on the Microscope and Accessories; Prep-aration of Material, Staining, Sectioning, Slide Making;Outline of Photomicrographic Methods. Fees nominal.

CHARLES P. TITUS, DirectorTelephone 2530 Walker

-~~~~~18,UMO in use for filtering fast throughfilter paper or felts.$8.04 and $15.00 sizes complete with pump.

Write for circular.ALSOP ENGINEERING CO.

N.Ul.Northwestern University

MEDICAL SCHOOLSituated in Chicago in close proximity to importantHospitals with an abundance of clinical material.

ADMISSION REQUIREMENTS-Two years of Collegecredit, including a satisfactory course In Physics, Chem-istry, Biology or Zoology, and French or German.

COURSE OF STUDY-leading to the degree of Doctor ofMedicine-Four years in the Medical School and a fifthyear either as Interne in an approved hospital or devotedto research in some branch of Medical Science.

GRADUATE INSTRUCTION-in courses leading to the de-gree of Master of Arts or Doctor of Philosophy.

RESEARCH FOUNDATION-The James A. Patten Endow-ment for Research affords unusual opportunities for ad-vanced students of Medical Science to pursue specialinvestigations.

RESEARCH FELLOWSHIPS-Four fellowships of thevalue of $500 each are awarded annually to promotescholarly research.

TUITION FEES-The tuition fee for undergraduate stu-dents is $215.00 a year.Next session begins September 28, 1926.

For informatios address

C. W. PA1TERSON, Registrar2421 South Dearborn St. Chicago, Illinois

Becond Edition: Revised and EnlargedTHE RAT: DATA AND REFERENCE TABLES

MemoirNo. 6: 458 Pages. Bibliography: 2206 TitlesHENRY H. DONALDSON

Published by THE WISTA INSTITUPhiladelphia, Pa., U. S. A. Price, $5.00

I --I

a<iPOaTDtYPe,E*Ne0 ~~ountgLin enTpeTwritr.V. S. A.r i Quick. Valuable, ReadableWriter.

Great Indexer, Check Writer andLabeller. W't, X oz.Complete with Ink and Pocket

Case, $Sooo.(U. S. Pat. 1,57I,656. Co.)

BookletH.E.W,'S Specials, Audubon, Pa.

THE MONISTOctober, 1926

Contents:Recent Philosophical Work in English Speaking

CountriesC. Lloyd Morgan

" Influence and Reference"R. F. Alfred Hoernle

" IdeaLism and Evolutionary Naturalism"M. C. Otto

" Instrumentalism"Harold R. Smart

" Logical Theory"Wilbur M. Urban

" Value Theory and Aesthetics "

Louis Arnaud Reid" The Appearance of Values"

Henry WV. Wright" Ethics and Social Philosophy "

B. MI. Laing"Hume and the Contemporary Theory of

Instinct"A. A. Roback

" Psychology as an American ScienceW. P. Blevin

" The Theory of Sensation"Seymour Guy Martin

"History of Philosophy"Single copies, 85 cents; yearly, $3.00

THE OPEN COURT PUBLISHING CO.122 South Michigan Ave. Chicago, Illinois

INVENTIONS-PROCESSESWe have responsible clients in the Industrial

field who desire to secure rights to inventionsand processes of proven or potential commer-Cial value.We invite correspondence from Physicists

and others who desire to profit by their inven-tions, and we make no charge for consultationand advice.

H. R. VAN DEVENTER, Inc.,342 Madison Ave. New York

Consulting and Industrial Engineers.Specialists in Waste Utilization, Refrigeration, and

the Development of Electrical and Radio Devices.Our Patent Department under the personal super-

vision of H. R. Van Deventer, Solicitor of Patents.

.r

II

SCIENCE-ADVERTISEMENTS

.MIKMP -I (

4' *SUPPLY BILuu rrEIDZPrETMNT BIOLOGICAL SUPPLIES

Open the EntireYeM For the classroom, museum or aol-

lector.*4 >^* First class preparations.

Send for new (I926) CatalogueNo. I. Zoological and Embry-ological material, Life His-tories and Habitat Groups.Catalogue No. 2, Botanical MaterialCalogue No. 3, Microscopic Slides

Address all correspondence regard-ing material and catalogues to:

GEO. IM GRAY, CuratorTHE MARINE BIOLOGICAL LABORATORY

Woods Hole, Mass.

MicroscopesBausch & Lomb, Spencer, Zeiss and Leitz.

Complete listings in our BiologicalCatalog.

EIMER & AM]Est. 1851

Third Ave., 18th to 19th St. New York, N. Y.

ENDInc. 1897

ELECTRICALMEASURING

EQUIPMENTS SUITABLE FORRESEARCH AND INDUSTRIAL

LABORATORIESList of Publications Furnished on

RequeFt

LEEDS & NORTHRUP CO.4901 STENTON AVENUE PHILADELPHIA

"You hase tho, beat ight-weight bag made,"-Dr. a. P. PordvceFALUA PATENT SLEEPING BAG

You can sleep outdoorsIn perfect comfort

Scientijloally CorrectMade like the fur of an animal, itretains body heat but not themoisture. No dead air spaces tobecome foul or soaked, as in aclosely woven or filled fabric. t9%Weighs about 5 lbs ....^Ps*

NMW PAULIN ALTITERUsed by U. S. Engineers, Oil Companies and others.

Particularly useful for securing contours one manwith a Paulin Altimeter can do the work ok two menwith Rod and Level. Send for Cirulor "A."

Writefor

Folder"A"

GURLEY'S Transits, Levels,Alidades, Meters & Registers.Microscopes & Binoculars.

Outfits for Explorers, Scientists, etc.

ANTHONY FIALA, 25 Warren SL, New York

Just one of ourSuperiorMethods

In producing Anal-ysis-Certified Chem-icals, we are deter-mined to adoptevery reasonable ex-pedient that willgive our customersunusual quality orconvenience.An example is our

_ '2 lg 2 _new square-neckedwax bottle for Hy-drofiuoricAcid. This

* sensible shape for~J~ ~- the opening gives

the user-no matterhow he happens topick up the bottle

~~*~,.., -a groove throughwhich he can pouirthe acid just whereit is wanted, with-out waste or dangerof spattering thiscorrosive acid oanthe user. Squarestopper fits snugly.

~~, .~ ~~' You will be de-lighted with Ster-ling Service onAnalysis - CertifiedChemicals.Send for Price lIst.Sterling ProductsCompany, Dept. 8

Easton, Pa.Wax with Square Neck

xiii

Coleman & BellBiological Stains

Are recognized throughout the UnitedStates and foreign countries as beingDEPENDABLE. This is due to thehigh standards of quality enforced in themanufacture, purification and testing ofthese products.A number of the common stains are

now available with the certificate of theCommission on Standardization of Bio-logical Stains.Complete catalogue of Laboratory Re-

agents upon request.

THE COLEMAN & BELL COMPANY(Incorporated)

Manufacturing ChemistsNorwood, Ohio, U. S. A.