October 22, 1908 J 



NA TURE 



629 



the all too short notice he g-ives of the ethnography 

 of the country is concerned with this question. Space 

 only allows of the conclusions at which he arrives 

 being given. 



After noting the greater density of the population 

 in the southern part of the colony, a result partly of 

 the forcing seawards of the people by repeated migra- 

 tions from the north, and partly of the exceptional 

 fertility of the ground ; he sums up rather unex- 

 pectedly for the remainder of the colony by saying, 

 ■' tandis que les grandes rivieres de I'intdrieur font 

 I'office de poles repulsifs de la population, les 

 montagnes ont et^ au contraire des poles attractifs." 



The book is essentially one for the geologist, and, 

 if in some places the amount of detail given appears 

 almost too great, we have in M. Hubert's work a 

 most comprehensive and valuable description of an 

 important West Coast colony. 



In view of what M. Hubert has been able to do 

 for Dahomey, and Drs. Esch, Solger, and others for 

 Kamerun, it is somewhat dispiriting to find a less 

 keen interest taken by geologists in England in 

 regard to the investigation of the not insignificant 

 British colonies and dependencies. J. P. 



THE SOLAR SYSTEM. 

 The Solar System. .4 Study of Recent Observations. 

 By Charles Lane Poor. Pp. x + 310; illustrated. 

 (London : John Murray, 1908.) Price 6s. net. 



IN putting into book form his lectures at the Colum- 

 bia University, Prof. Poor has rendered a great 

 service to those serious students who, unequipped 

 with a technical vocabulary and a knowledge of mathe- 

 matics, yet desire to become acquainted with our 

 present-day knowledge of the solar system. 



The book is distinctly different from the majority 

 of astronomical text-books in respect to the relative 

 importance attached to the various parts of the sub- 

 ject. Prof. Poor's lectures were evidently intended 

 to supplement the available text-books, and difficult 

 matters, generally given but brief notice, are treated 

 more fully and so clearly that the general reader will 

 find them now well within his limits. This charac- 

 teristic of the book is noticeable from the beginning, 

 where the author discusses the moon, and the alleged 

 variations of lunar features, the earth as an astro- 

 nomical body, and the tides. The figure and mass 

 of the earth, and their determination, the variation 

 of g'ravity with latitude, the modifications undergone 

 bv the luni-solar tide ere it produces the effects seen 

 round various coasts, and similar subjects are treated 

 comparatively fully. 



In the descriptions of the various attempts to 

 measure the solar paralla.x (chapter iv.), the author 

 refers to the 1900 observations of Eros as likely to 

 afford trustworthy values, but does not appear to have 

 included the preliminary results which have accrued 

 from the Greenwich and Cambridge campaigns. 



The chapter on the physical characteristics of the 

 sun is more conventional in its treatment, the history, 

 nature, and changes of sun-spots being discussed at 

 some length. A striking illustration of the variati><n 



NO. 2034, VOL. 78] 



with latitude of the solar rotation is provided in the 

 brief description of the relative displacement of land- 

 masses which would follow did the earth but exhibit 

 the same mobility; in a few days from the commence- 

 ment of a rotation, South America would have dis- 

 placed South Africa, whilst Sumatra would be directly 

 south of New York. The explanation of the Lockyer- 

 Janssen method of observing solar prominences leads 

 up to the more recent photographic application of the 

 principle in the spectroheliograph, and several of the 

 Verkcs results are reproduced. 



The brief descriptions of the instruments and 

 methods whereby the sun's light and heat have been 

 determined are especially clear, and should give every 

 reader a very fair idea of the results achieved by the 

 beautiful researches of Pouillet, Crova, Violle, Lang- 

 ley, and .^bbot. 



In the succeeding chapters the planets are dis- 

 cussed, first generally, as to their apparent motions, 

 mutual attractions, &c., then seriatim. The relative 

 certainty with which their various markings have 

 been established is treated at some length, and some 

 of the conclusions arrived at by Prof. Lowell come 

 in for sharp criticism. But it must here be remarked 

 that that observer has himself stated that the Venus 

 markings are not so hard or regular, or so Martian 

 in their appearance, as they were at first reported to 

 be, whilst many of the theoretical arguments against, 

 and practical negations of, the presence of water 

 vapour in the Martian atmosphere will avail little 

 against the spectroscopic evidence obtained at th^ 

 Lowell Observatory by Mr. Slipher (see Nature, 

 No. 2002, March 12, p. 442) since this book was 

 written. 



The present-day rapid march of astronomical dis- 

 covery is further illustrated in the chapter (xii.) on 

 satellite systems, in which the author recounts the 

 discoveries of three new satellites in as many years ; 

 yet the tale is incomplete, for, naturally, J viii is not in 

 the list. After a chapter on comets and meteors, 

 the book fittingly concludes with one on the evolu- 

 tion of the solar system, in which the author, after 

 taking a brief historical survey of the various hypo- 

 theses, shows how the planetesimal-spiral hypothesis 

 of Chamberlin and Moulton may be held to explain 

 most satisfactorily the many, and sometimes appa- 

 rently inconsistent, phenomena observed. 



The volume is beautifully printed and illustrated, 

 whilst its freedom from slips shows that the author 

 has exercised the same minute care over the proofs 

 that he has in the selection and exposition of the 

 matter. William E. Rolston. 



OUR BOOK SHELF. 

 Haitdbuch der Pharmakognosie. By Prof. A. 

 Tschirch. Part i. (Leipzig : Chr. Herm. Tauch- 

 nitz, 190S.) To be completed in about 30 parts at 

 2 marks (2.?.) each. 

 During the past twenty-five years there has been no 

 lack, in Europe or in the United States, of text- 

 books of pharmacognosy, most of which have been 

 designed to meet the requirements of limited circles 

 of students, and have doubtless more or less efli- 

 ciently served their purpose. But Prof. Tschirch 



