MORE THAN ONE HUNDRED scientific laboratories are using the Type K Potentiometer method for measuring hydrogen-ion concentrations. We have yet to learn of a single case where, with proper manipulation, a Type K Outfit has not unfailingly given as highly accurate results as the experimental conditions permitted. IF YOU WANT FURTHER PROOF IF of the excellence of the Type K Potentiometer as applied to hydrogen-ion measurements, you will find them in Catalogue S75, which also contains much valuable information about such measurements. Leeds & Northrup Company Electrical Measuring Instruments 4901 Stenton Ave. Philadelphia, Pa. FOR SALE Scientist retiring from active work will sell The Microscope the following apparatus, which would form an excellent adjunct to any institution of learning: One complete X-ray outfit, adaptable to By SIMON H. GAGE of Cornell University 13th Edition, Published December, 1920 any current, with fluoroscopes. One Demon- in this edition, special emphasis is put upon the Dark-Field Microscope stration Apparatus, with Polariscope, Spectro scope, Pencil Apparatus, Lenses, and every COMSTOCK Must be seen to be appreciated. Postpaid $3.00 Professor in a Western College desires exchange professorship with Zoologist in university or college in Eastern States. Address Apply R, care of Science, Garrison, N. Y. | P., Science, Garrison, N. Y. New Books That Have a Message For You Hygiene By Clair E. Turner, Asst. Prof. of Biology and Practical Chemical Analysis of Blood By Victor C. Myers, M.A., Ph.D., Prof. of Pathological Chemistry, N. Y. Post-Graduate Medical School and Hospital. 125 pages, 7 x 10, with 13 illustrations. Price, cloth... .$3.00 Myers presents a discussion of the chemical blood determinations which have been found of definite value in the treatment and diagnosis of disease. Complete literature references, Blood and Urine Chemistry By R. B. H. Gradwohl, M.D., Director of the Gradwohl Laboratories, Chicago and St. Louis; Director of the Pasteur Institute of St. Louis; and A. J. Blaivas, formerly Assistant in Chemical Laboratory, St. Luke's Hospital, New York. 418 pages, 6 x 9, 75 text illustrations and four color plates. Second edition, revised and en.85.00 larged. Price, cloth.... This second edition represents the accumulated literature of the past three years on blood and urine chemistry both as regards technic and interpretations. Physiological Chemistry By Sidney W. Cole, M.A., Trinity College, Cam- Price, cloth... New fifth edition, completely revised. some quantitative urine methods, and lists of Physiological Chemistry standard solutions and reagents are given. Wassermann Test By Charles F. Craig, M.D., M.A., F.A.C.S., Lieut- Includes the modification of the complement- By C. J. V. Pettibone, Ph.D., Assistant Professor Selected Lectures and Essays Including Ligaments-Their Nature and Mor- The classic lectures and essays of the famous You should order copies of these important books today through your bookseller or direct from the publishers. Also request a copy of our complete catalogue of medical, dental, scientific, pharmaceutical, and nursing publications. Mention "Science" when writing or ordering. pl. $3.50, $5.00 NEW-WORLD SCIENCE SERIES Edited by John W. Ritchie ZOOLOGY 169. Callaway, Morgan. The Infinitive in Anglo-Saxon. A Textbook for Colleges and Octavo, 352 pp. . . . 171. Lancaster, H. C. Pierre Du Ryer, Dramatist. Octavo, . 187 pp., 1 pl. $1.25 189. Osgood. C. G. Concordance to the Poems of Spenser. Quarto, 1010 pp., 1 pl.. $20.00 202. Cooper, Lane. Concordance to the Works of Horace. Octavo, 603 pp. $7.00 208. Broughton, L. N., M. R. Thayer. and others Concordance to the Poems of Keats. Quarto, 458 pp., 1 pl., $7.00 262. Bergen, Henry, The Fall of Princes, by John Lydgate, edited from the best Manuscripts, with Bibliographical Introduction, Notes, and Glossary. Octavo . . In press The publications of the Institution how number over 400 volumes, the subjects including Anatomy, Archæology, Astronomy, Botany, Chemistry, Climatology, Economics and Sociology, Embryology, Experimental Evolution and Heredity, Engineering, Folk-Lore, Geology, History, International Law, Literature, Mathematics, Medicine, Nutrition, Paleontology, Philology, Physics, Stereochemistry, Terrestrial Magnetism, Zoology. Classified and descriptive lists will be sent postpaid on application. All communications should be addressed to The simple explanations of biological CARNEGIE INSTITUTION OF WASHINGTON facts and the pleasing style in which the WASHINGTON, D. C. Publications of The Philippine Bureau of Science VEGETATION OF PHILIPPINE MOUNTAINS. The relation between the environment and physical types at different altitudes. By William H. Brown. 434 pages, 41 plates, and 30 text figures; postpaid $2.50, U. S. currency. INDEX то THE GENERA OF BIRDS. By Richard C. McGregor. 185 pages; postpaid $1.00, U. S. currency. SPECIES BLANCOANAE. A critical revision of the Philippine species of plants described by Blanco and by Llanos. By E. D. Merrill. 424 pages; postpaid $2.25, U. S. currency. PHILIPPINE WATER SUPPLIES. By G. W. Heise and A. S. Behrman. 218 pages, 19 plates; postpaid $1.75, U. S. currency. AN INTERPRETATION OF RUMPHIUS'S HERBARIUM AMBOINENSE. By E. D. Merrill. 596 pages, 2 maps; postpaid $3.00, U. S. cur book is written offer an unusual appeal to both the specialist and the liberal student. The general reader also is finding great interest in the book. These are the opinions of some who have examined the book: "I am filled with enthusiasm. What a remarkable account it is of just what the student should know. I admire and wonder at the clever and broad and apt selection of topics quite as much as I enthuse over the masterly treatment." "I think so much of the book that I shall order copies at once. I had planned to follow my own outlines and use the library, but with this book on the market I have changed my mind." "It is quite different from anything that has hitherto been written. It is full of originality." "It is a wonderfully comprehensive and human document." Cloth. xii+558 pages. Illustrated. WORLD BOOK COMPANY Yonkers-on-Hudson, N. Y. 2126 Prairie Avenue, Chicago |