November i 7, 1923] 



NATURE 



719 



survivals from a cold-water fauna which had a wide- 

 spread distribution at the end of the glacial period. 



In dealing with the variations of lake levels. Prof. 

 Halbfass discusses the asserted dessication of the con- 

 tinents. This view he dismisses most emphatically. 

 The fall in level of many lakes he attributes to artificial 

 influences, and he holds that lakes in all parts of the 

 world show that there has been no general lowering of 

 their level in historic times. He refers especially to 

 Lake Chad, which he says is placed in the first line by 

 the " dessication fanatics." He holds that this lake 

 gives them no support since Marquardsen has shown 

 that for eighty years after the visit of Denham (j,.e. from 

 1824 to 1905), the boundary of the lake has remained 

 essentially the same. In dealing with this problem he 

 refers to Bruckner's thirty-five-year climatic cycle 

 period, which he says is not confirmed by the evidence 

 of the lakes of at least four of the continents ; yet he 

 holds that there is an actual climatic period, which is 

 three times as long as the Bruckner period. 



In the chapters on the distribution and origin of lake 

 basins Prof. Halbfass rejects their glacial origin, except 

 in so far as many of them occupy hollows in drift, or 

 are held up by moraine dams. He rejects not only 

 the glacial origin of deep rock basins but of many 

 lakes of the Baltic Plain for which glacial denudation 

 seemed far more probable. He adopts the views of 

 Wahnschaffe and Jentzsch that these basins are due to 



« tonic subsidences, and in some cases, such as that of 

 ! Rogasener Lake in Posen, the basin, though now all 

 covered with drift deposits, was pre-glacial in origin. 

 In dealing with this problem Prof. Cotton's book (4), 

 which is a general summary of physiography illustrated 

 by examples from New Zealand, is less in accordance 

 with recent opinion ; for he represents the New Zealand 

 fiords as glacially cut troughs of which the lower parts 

 have been filled by the sea. They appear to agree 

 with those of Norway, where the overwhelming balance 

 of opinion is in favour of the pre-glacial age of the 

 fiords. Prof. Cotton has an exceptionally fascinating 

 subject, as New Zealand is especially rich in clear 

 examples of geographical processes. 



The book is well illustrated and his views are clearly 

 stated. It illustrates the growing extent to which 

 some schools in Australasia are dominated by American 

 opinion ; this fact, in the case of geography, is easily 

 explained by the attraction of that logical scheme of 

 geographical evolution for which we are deeply indebted 

 to Prof. VV. M. Da vies. The extent to which British 

 work is overlooked may be judged by the bibliography. 

 Of the 59 memoirs quoted only five are British, and 

 they date from 1802 to 1876, the latest contribution 

 in this list by any British worker being Thomson's 

 paper on the windings of rivers. 



NO. 2820, VOL. I 12] 



Our Bookshelf. 



Theorie der Kristallstruktur : ein Lehrbuch. Von Prof. 

 Dr. Artur Schoenflies. Pp. xii + 555. (Berlin: 

 Gebriider Borntraeger, 1923.) 185. 



Apart from its obvious indispensability to the specialist, 

 this new edition of the author's former " Krystall- 

 systeme und Krystallstruktur " (1891) would seem to 

 bear a character of wider significance, as showing that 

 wisdom is justified of her children. There can be few 

 such signal instances in science in which an abstract 

 and apparently unverifiable theory has been so rapidly 

 brought within the ambit of the experimental method, 

 and proved to be equal to all demands. It is, there- 

 fore, peculiarly appropriate that one of the original 

 founders of the modem theory of crystal structure 

 should return to his subject in the light of recent 

 X-ray developments. By including a discussion of 

 those points in which the theory is still ahead of 

 experiment, the author contrives to confer on his work 

 a new prospective value. 



The book is, of course, mainly concerned with a 

 systematic development of the 32 classes of symmetry 

 and the 230 possible ways in which matter may be 

 properly disposed throughout the space occupied by a 

 crystal. The general arrangement is necessarily much 

 the same as before, but the exposition has been vastly 

 improved in at least one particular. The former edition 

 was solely addressed to the mathematician, to whom 

 the addition of anything of the nature of a diagram 

 (unless it take the special form of a symbol) would 

 presumably impede the working of pure thought. The 

 present work is rather directed to the crystallographer 

 and X-ray analyst, and is therefore illustrated with 

 structural diagrams, praiseworthy alike in quality and 

 quantity. 



In view of the existence of such an authoritative 

 treatise as the Braggs' " X-rays and Crystal Structure," 

 the author has refrained from entering into any account 

 of the practice of X-ray investigation. It is, however, 

 evident that the actual results are fully appreciated, 

 for considerable space is devoted throughout the text 

 to a systematic treatment of the relations between the 

 number of particles (as also their symmetry) and the 

 various positions they occupy in the structure. More- 

 over, a special chapter is devoted to space-partitioning 

 and the packing of equal spheres ; whilst another, 

 possibly the most important of all, deals witli selected 

 cases investigated by X-ray workers. This inevitably 

 leads to a discussion of the possible influence sub- 

 atomic structure may exert on the physical manifesta- 

 tions of a crystal, and to a final conclusion that the 

 only possible way of further progress is along the path 

 of experiment. 



It may be added, in conclusion, that those qualities 

 of clear and concise expression, which have always 

 made Dr. Schoenflies' writings the most favoured 

 original source in the domain of crystal structure, are 

 fully preserved. By bringing out so valuable a work 

 in the fare of obvious contemporary difficulties, both 

 author and publishers have placed a wide-spread body 

 of workers under a debt of gratitude, which they can* 

 scarcely ever discharge. 



T. V. B. 



