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electrons through gases at moderate down to very low pressures. These are by no means the least coy or elusive of the more out-of-the-way data of physics, and their tracing down, even in relatively simple special cases, taxes or overtaxes the resources even of a large library. I n many sections of the subject, sufficiently precise and extended numerical data were practically nonexistent a few years ago, and all workers-even those favored ones who have enjoyed the help of a more experienced hand in the same laboratory-must have felt acutely the need for tables of the kind now under review. The book therefore undoubtedly fills‘a serious gap in the literature. The completeness of the filling can only properly be judged after prolonged use of the book in the laboratory. The less stringent test of a fairly close inspection reveals no serious omissions or errors in the work, which contains not only a comprehensive summary of the relevant properties of atoms, molecules, electrons, ions, and photons, but also the equivalent of “workshop hints” on the materials in common use in discharge tubes, and on high vacuum technique, together with a useful collection of mathematical formula and tables. Some minor criticisms may be offered, mainly on p a t t e r s of form; for instance, the unjustifiable piling up of unsignificant figures on some of the data, and the habit of referring the more inquisitive reader to the Handbuch der Physik or similar works, and not to the original papers. These points do not however affect the general utility of the book. The price is somewhat high, especially in sterling, but the book, with its elaborate tables and large number of specially drawn curves, cannot have been a cheap one to produce. H. R. ROBINSON. Rontgenoskopie und Elektronoskopie von dispersen Systemen, Faden, Filmen, und Grenzschichten. Sonderheft der Kolloid-Zeitschrift, Bd. 69, H. 3. Edited by Wo. Ostwald (12 contributors). 27 x 19.5 cm.; 138 pp. Dresden and Leipeig: Steinkopff, 1935. Price: 9 RM (stiff paper cover). This volume presents the contributions of Ostwald, Schiebold, Brill, Fricke, Halle, Astbury, Hofmann, Saupe, Wever, Rupp, Trillat, and Bruche t o the General Meeting of the Kolloid-Gesellschaft in Hanover in September, 1934. It provides a useful and authoritative general sketch for those wishing to acquire some familiarity with these comparatively new applications of x-ray and electron optics, with some hundreds of references to original papers which will be invaluable to those whose interests are more specialized. H. R. ROBINSON. Dizionario di Chimica generule e industriale. Volume 11. F-2. By MICHELEGIUA AND CLARA GIUALOLLINI. 29 x 20 cm.; iii, 71 1137 pp. Turin: Unione Tipografico-Editrice Torinese, 1934. Price : 175 lire. This second, and final, volume of the Dictionary of Chemistry, containing 54 more pages of text than the first volume, covers the headings F-Z. Thus it is evident that, even when allowance has been made for the difference in the Italian alphabet, the matter i n this volume has been more condensed than in the previous one. The second volume contains 23 full page plates and 521 illustrations in the text, as against 28, and 565, respectively, in the first. I n addition, the second volume includes 71 pages of comprehensive index t o the whole, 2 pages of corrections, and a list of journals with their quoted abbreviated titles. The dictionary is comprehensive, dealing not only with pure chemistry, but also
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