pages instead of 1091. Some of the essay chapters are omitted or condensed and combined, and paragraphs or groups of para- graphs are cut directly out of the larger text to make the smaller edition.

This book is well written and gives an air of authority without any signs of pedantism. I t contains a tremendous amount of good theoretical and practical information, There are many references to the commercial uses of organic compounds as well as to laboratory processes of the preparation. Chemistry is a laboratory science and the discussions of reactions from the lab- oratory standpoint help chemists to keep "one foot on the ground." Questions are given a t the ends of someaf the chapters, also references to the literature, chiefly and properly to review articles. The book is up to date as evidenced'by the discussion of resonance, of the use of isotopic tracer elements in solving the courses of reactions, and of the structure and synthesis of biotin. Brief notes on the history of compounds, the derivationof names, and the biological significance of compounds, are excellent. Not only are these of general interest, they also help the student by association to remember facts. The book is full of structural formulas and they are very well done. Scarcely a page is noted without a t Least one, and this extensive use of the organic chem- ist's shorthand is worth while. Many tables of compounds and physical data are very helpful.

The Geneva system of nomenclature is used considerably. The authors follow the older method of adding suffixes (hutened) instead of the more modern American Chemical Society method of prefixes (2-butene).

The introductory chapter consisting of 24 pages on "The Ka- ture of Organic Compounds" is a liberal education in the funda- mentals of the subject, and the section on "Problems in Synthesis" is provocative of good thinking. Three hundred ninety-five pages cover aliphatic compounds and two hundred twenty-six, aromatic compounds. There are, of course, some overlapping subjects, such as the chapter on stereochemistry, and there are two closing chapters on "Synthetic Fibers and Plastics," and "Physiologically Active Agents." The aromatic compounds are adequately discussed, and the accent on aliphatic chemistry is desirable in these days. The arrangement or order of treatment of subjects may not be what might be considered regular, but the general subject is so well covered that the author's arrange- ment is scarcely open to question. There is a very good index, 32 pages of double columns.

The typography of the book is excellent and errors must be very few sinceonly two, in spelling, were nated (pp. 79,648).

HARRY L. Frsnen U. S. I ~ n u s r a r * ~ C w ~ n c r ~ s , INC.

STAMPOLD. C O N N B C T ~ V T

SEEING THE INVISIBLE. THE STORY OR THE ELECTRON MICRO- SCOPE. Gessner G. Hawley. Alfred A. Knapf, New York, 1945. xv + 196 + ix pp. 12.5 X 18.5 cm. $2.50. Written for the layman, this little volume is the life history of our latest scien- tific baby, the electron microscope. Chapter 1, "The Search far the Small"--excites us to its

wonders: jagged particles of face powder magnified 47,800 times; pneumonia germs looking 35,000 times larger than nature in- tended; studies on quick-setting cement for the Siegfried Line: photographs of paper, textiles, and synthetic rubber for a nation at war; current practice of taking electron microscope pictures with 1000 to 8000 times magnification, then photographically enlarging to a hundred times the magnification achieved with the ordinary microscope.

Chapter 2, on "The Physics of Waves"--diffraction, resolving power, and interference is poorly done, using oversimplified analo- gies with water-waves-examples which confounded this re- viewer more than the phenomena themselves.

Chapter 3, "How the Electron Microscope Works2'-includes many interesting details: (a) electrons from a hot filament oper- ated around 60.000 volts *l volt d. c. obtained from ordinary 110-volt a,-=. house current; (b) electromagnetic focusing giving higher resolution and magnification than electrostatic focusina.

500 to 5000 Angstroms thick mounted on a 1000-Angstrom col- lodion layer, or transferred to a polystyrene film; (d) recent models with improved vacuum technique, eliminating the special air-lack; (6) stereoscopic pictures.

Happily this author does not view his popular science through roseate glasses, for in Chapter 4 he frankly states the limitations of the electron microscope: its lower limit of 15 Angstroms, too small to see common molecules; the destruction of specimens by vacuum, or by the searing and dehydrating effect of electron bombardment; and difficulties in preparing specimens.

Chapter 5 reviews the historical development in this country down to the present portable models by RCA (electromagnetic focusing) and by GE (electrostatic focusing). Perhaps too little is said of the superb photographs once obtained in Europe.

Chapter 6 discusses the pioneer researches by Columbia Carbon Co., revealing that particles of carbon black are round and smooth, and the importance of this in rubber chemistry; of the round and pear-shaped particles of rubber latex, 20 times larger in natural rubber; of grains of metallic smokes, round for alu- minum, needles for zinc oxide.

Industrial applications are treated in Chapter 7-the struc- ture of wood pulp, textile fibers with dyes, photographic emul- sions, clays and soils; and of the recent techniques for obtaining impressions on plastics.

In Chaoter 8. we see clumsv bacteria outside the cells: viruses which penetrate and reproduce within the cell; leucocytes en- gulfing pneumonia germs, a bacteriophage attacking, penetrat- ing, and finally destroying a streptococcus ceil; and individual molecules of tobacco mosaic virus. There is speculation on things yet to be discovered with cancer cells, and with genes.

The concluding chapter peers briefly into the future, reiterating the shortcomingsof the new instrument.

The author has performed a useful service both in collecting these pictures, most of which have already appeared in print, and in writing a story of our latest scientific prodigy. The story is a t times dull, explanations awkward, and statements inac- curate, but on the whole the volume should prove interesting to the young scientist andlayman.

HUBERT N. ALYEA PRINC&TON U N m ~ B s r n PIWCETON, Nsw JERSEY

EXPER~MENTS IN GENERAL INORGANIC CHEMISTRY. J . L. Maynard and T . I. Taylor, Assistant Professors of Chemistry, School of Chemistry. University of Minnesota. D. Van Nos- trand Comoanv. Inc.. New York. 1944. xi + 554 oo. 101 . .. . . figs. 17 X 24 cm. 'paper cove& spiral wire binding. per- forated sheets. $2.90. This laboratory manual is designed to accompany "General

Inorganic Chemistry" by Sneed and Maynard, although it may he adapted to accompany other textbooks. Fifty-five general experiments are included, together with qualitative analysis for twenty-two common cations according to the scheme presented in "Semimiera Qualitative Analysis" by Barber and Taylor.

The hook opens flat and occupies small desk space. The system of recording results on separate pages indexed according to the experiment is an admirable feature. A large appendix includes a discussion of errors and logarithms.

The manual i.i relatively heavy for the flimsy covers. The experiments are irregular in length. The first 22 of the 55 ex- periments cover the topics of introductory principles, oxygen. hydrogen, and water. Experimental directions, questions about observations, and reference questions are often included in the same paragraph, sending the pupil frequently to the textbook when writing his lahoratory report. The description of the ex- perimental synthesis of copper sulfide (p. 83) differs radically from that given in the textbook. Small quantities of reagents are specified throughout. Normal or molar designations are regularly made for the concentrations of liquid reagents, e. g., 36 N HsS04.