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The Special Theory of Relativity. By HERBERT DINGLE. vi 94 pp. New York: Chemical Publishing Co., Inc., 1941. Price: $1.50. This small book will be welcomed by all who have been somewhat confused by treatments of the theory of relativity which can only be described as murky mixtures of physics and metaphysics. Professor Dingle develops the special theory from a redefinition of the measurement of length and succeeds admirably in his task of presenting the theory as a mathematical formulation of relations first discovered in the world of experience. The final chapter is an illuminating, although brief, account of the transition to general relativity. All students concerned with the fundamental concepts of physical science will find much of interest and of value in this booklet. F. H. MACDOUGALL.
The Internal Constitution of the Stars, being a collection of papers read a t the Conference held by the New York Academy of Sciences on October 20-21,1939. By ZDENEKKOPAL,ROBERTE. MARSHAK, HENRYNORRIS RUSSELL,AND JAAKO TUOMINEN, with an introduction by HARLOW SHAPLEY. Vol. XLI, Art. 1. 0 x 9 in.; 76 pp.; 2 figures; 10 tables. New York: New York Academy of Sciences. Price: $61.00. Of the four articles published in this volume, those by Marshak and Tuominen deal with the theoretical calculation of opacity under white dwarf conditions and with the question of stellar envelopes and the mass concentration and central temperatures of stars, respectively. The former paper is entirely theoretical and makes no comparison with observations; the latter gives an application to the conditions in the brighter component of Capella-the sheet anchor of all theories on stellar structure-and shows that both the internal density distribution and the central temperature are very dependent upon the functional character of the opacity coefficient. The articles by Russell and Kopal deal with the distribution of density within a star and with the ellipticity and reflection effects in binary systems, respectively; in both cases the observational data are derived from observations of eclipsing binaries. Both authors present carefully worked out theories, based upon the fundamental laws of matter as we now understand them, and both authors claim that their theoretical results are satisfactorily borne out by the observations. This reviewer cannot subscribe to such an optimistic point of view and feels that both investigators have perhaps been carried away by their enthusiasm for their theories. Thus, no mention is made of the fact that in several eclipsing binaries the observational evidence indicates an axial rotation which is faster than the orbital revolution, whereas theory demands synchronism,-and these cases include the classical star Y Cygni. T o say that the constant K which measures the degree of central density concentration can be reliably determined from the observed advance of periastron is certainly a euphemism, and the statement that the evidence in favor of a high central condensation is conclusive creates a somewhat erroneous impression, in the reviewer’s opinion. The difficulty with the observed apsidal motions has always been, and still is, that many of them are much too slow and would indicate such excessively high central density concentrations as to be incompatible with all other estimates. N o mention is made likewise of the “ellipsoidal variables” and the fact that their light variations-not complicated by eclipses-indicate tidal distortions far in excess of those of even a homogeneous body. The statement that the observed value AZ = 1.03 f 0.03 (p.e.) shows that “if stars are polytropes, their structure seems to be specified very nearly by the index n = 3” appears far too emphatic, if one recalls that a polytrope of index 3 should haveAl = 1.029,but one with index 5 , or a Roche model with all the mass concentrated in one point at the center, should have A2 = 1.OOO.
