October 14, 1920] 



NATURE 



205 



Sections ii.-vi. contain tabular matter exclu- 

 sively. The explanation of the tables is contained 

 in the ten chapters of section i- This appears to 

 be a model of clearness. Except in chronological 

 questions and in special researches the ordinary 

 astronomer rarely has occasion for single places 

 of the moon outside the range of the hourly ephe- 

 meris provided in the .\lmanacs. The chief func- 

 tion of the tables therefore lies in the calculation 

 of this ephemeris from year to year, and this fact 

 has been kept in view in their arrangement. Ad- 

 vantage has been taken of Hansen's example to 

 the extent deemed profitable, and a number of 

 original devices have been introduced, including a 

 new scheme of re-entrant arguments. By these 

 means it is believed that the computation of an 

 ephemeris will be at least as rapid as with 

 Hansen's tables, in spite of the inclusion of about 

 five times as many terms, .'^n accumulation of 

 errors in the sums of many tabular entries is un- 

 avoidable. From this source probable errors of 

 0-04" in the longitude or latitude, and of 0-003" '" 

 the parallax, are expected after these co-ordinates 

 have been finally contracted to one decimal place 

 less. Imperfections in the adopted constants and 

 cumulative small defects of theory may raise these 

 amounts to ±01" and ±005" respectively. Clear 

 instructions are given for making such adjust- 

 ments in the fundamental constants as may here- 

 after prove necessary. But there need be no illu- 

 sion that the moon will actually follow the strict 

 gravitational path laid down so carefully in these 

 tables. As it is, the empirical term 



+ 1071" sin (i400°(/c- 18-5)+ 1707°}, 



with a period of 257 years, has been admitted in 

 the longitude, with consequential changes in the 

 arguments of some other terms. In magnitude 

 this is comparable with the great Venus term, and 

 the explanation of it is still to seek. Discrepancies 

 will recur, and the advantage to be expected from 

 the new tables is that they will no longer be en- 

 tangled with the errors of a faulty ephemeri.s. If 

 this hope is realised — and there is no reason to 

 doubt that it will be — unstinted gratitude will be 

 due to Prof. Brown and to those who have 

 assisted him cither by active collaboration or by 

 financial aid. 



The tables have been printed in luigland at the 

 Cambridge University Press. The paper is of an 

 unusually sumptuous and durable quality appro- 

 priate to a work of lasting value which will have 

 to bear repeated handling for a long time. The 

 type is admirably clear. Only one superficial 

 point suggests adverse comment. The pagina- 

 tion is peculiar. In their present form the tables 

 consist of six sections in three volumes. Each 

 NO. 2659, VOL. 106] 



section, of length varying from 39 to 223 pages, 

 is paged independently from i onwards. In what- 

 ever form the work is finally bound, this will 

 surely prove an inconvenient plan for any purpose, 

 such as the correction of errata. .\ continuous 

 sequence would have been preferable. But per- 

 haps there will be no errata (beyond one already 

 noted), and in any case the blemish, if it be one, 

 is trivial. H. C. P. 



Genesis, Evolution, and History. 

 The Evolution of the Earth and Its Inhabitants. 

 By Joseph Barrell and Others. A Series of 

 Lectures delivered before the Yale Chapter of 

 the Sigma Xi during the Academic Year 1916- 

 1917. Pp. xiv -H 208 4- iv plates. (New Haven : 

 Yale University Press; London: Humphrey 

 Milford; Oxford University Press, 1918.) Price 

 loi. 6d. net. 



THIS book consists of five lectures by five 

 experts, who deal with various aspects of 

 evolution. The range extends from the nebula to 

 modern civilisation, and the wonder grows that one 

 word can cover it all. We feel as if the word "evo- 

 lution " were in danger of becoming like a house- 

 hold knife — used in so many ways that it tends to 

 become useless. The use of the same term for so 

 many different kinds of becoming is apt to suggest 

 that they are all describable by the same formulae. 

 To avoid this fallacy, might it not be well to find 

 differentiated terms, such as genesis in the domain 

 of things, evolution in the realm of organisms 

 (keeping development for the becoming of the 

 individual), and history for the kingdom of 

 man? 



The first lecture deals with the genesis of the 

 earth and of the parent .solar system, and, the 

 establishment of the earth having been accounted 

 for, its subsequent changes are traced until the 

 time of its becoming a fit home for life. Prof. 

 Barrell adopts the theory of the origin of the earth 

 as a secondary spiral nebuk heaved off from the 

 central sun as the result of tidal forces produced 

 by the cJose approach and passage of another star. 

 He favours the hypothesis of earth-growth by the 

 rapid infall of planetoids (not by Chamberlin's 

 "slow accretion of planetesimals ") and the hypo- 

 thesis of an earth initially molten. 



The .second lecture, by Prof. Schuchert, dis- 

 cusses the changes of the earth's surface and 

 climate during geologic time, which the author is 

 inclined to put at about 800 million years. The 

 constant shrinkage of the earth leads to an insta- 

 bility of surface that brings about periodic changes, 

 not only in the areal space-relations of water and 

 land, but also in the shapes and heights of the 



