NEU? BOOKS
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then afterwards to view it stereoscopically to be a t once convinced of the immense gain in clarity obtained by so doing. It is a real difficulty in work on crystal structure that the results of an analysis are not easily made clear to the chemist or mineralogist whom they might interest. The ideal method, the study of three-dimensional models, is rarely available, but sets of stereoscopic models of this kind make a very good substitute for models, and one could wish that more of them existed. Mrs. Rehbock-Verstandig has drawn the figures for this volume with much skill, and with the help of the text, which was contributed by Dr. G. Menser and has been translated into English by Mr. Greenwood, the English and German versions being in parallel columns, it is easy to get a very good idea of the plan according to which the structures here shown are built up. Although, if necessary, this information can be obtained from the Strukturbericht of Ewald and Hermann, it would undoubtedly have been a convenience to the reader if references to the sources from which the structures are taken had been given in the text. R. W. JAMES.
Eclipses of the Sun. By 8. A. MITCHELL.Fourth edition, revised and enlarged. New York City: Columbia University Press. Price: $5.00. The present, and fourth, edition of this standard treatise on eclipses differs from the previous issues chiefly in the addition of an extra chapter dealing with the recent eclipses of 1932 and 1934. It is unfortunate, in this connection, that a t least a few allusions to these eclipses were retained uncorrected from the previous edition. Thus, we find that in 1935 the author still predicts what will happen in 1932. This last chapte>rcontains an excellent summary of some of the conclusions derived from crucial observations made a t the occasion of these two recent eclipses, and a description of Lyot’s success in obtaining spectra. of the corona without an eclipse. The remainder of the book is still essentially the same as in previous editions, and contains a description of historical eclipses and of the gradual development of and the improvement in the prediction of eclipses; furthermore, some chapters dealing with the working of the spectroscope and giving an outline of our present ideas on the structure of the atom and the theories of ionization and relativity. The remainder of the book is devoted to a detailed description of virtually all well-observed eclipses of modern times from 1842 onward. The arrangement of the chapters suggests that the author had a dual purpose in writing this book, namely, to make it appeal to both professional astronomers and the public a t large. The very large amount of personal narrative included was doubtless a concession to the latter, but the reviewer feels that its omission would have made the book more acceptable to the former. Similarly, in connection with the early historical eclipses a good deal of Egyptian history has been included and a rather invidious comparison made between the astronomical accomplishments of the early Egyptians and the Babylonians, which, in this reviewer’s opinion, might well have been left out. Such comparisons represent, at best, only a consensus of opinion rather than a statement of fact, and in the present instance appear to be based chiefly upon the authority of a single egyptob ogist-Breasted-in a field of such great diversity of opinion. The reviewer cannot help expressing the wish that the author, one of the foremost observers of eclipses of our times, would condense into a separate monograph all the facts and theories of interest to the professional astronomer, but without any concession to popular appeal in the form of discussions which are, after all, not very relevant from the astronomer’s point of view. W. J. LUYTEN.
