NA TURE 



^3 



THURSDAY, SEPTEMBER 24, 1914. 



SPECIALISED GEOLOGY. 

 /"' I Structural Geology. By C. K. Leith. Pp. 

 iii+iSg. (London: Constable and Co., Ltd.) 

 Price 65. 6d. net. 



Geologischer Fiihrer durch Nordwest-Sachsen. 

 By E. Krenkel. Pp. vii-i-202 + 14 plates. 

 (Berlin : Gebriider Borntraegfer, 1914.) Price 

 4 marks. 



(3) Australasian Fossils. A Students' Manual of 

 Palaeontology. By F. Chapman. With an 

 introduction by Prof. E. W. Skeats. Pp. 341. 

 (Melbourne and London : G. Robertson and 

 Co. Propy. , Ltd., 1914.) 



(4) Practical Instructions in the Search for, and 

 the Determination of, the Useful Minerals, 

 including the Rare Ores. By A. McLeod. 

 Pp. ix+114. (New York: J. Wiley and Sons, 

 Inc. ; London : Chapman and Hall, Ltd., 1914.) 

 Price 55. 6d. net. 



(il TV T R. LEITH'S book does not cover so 

 IV 1 wide a field as Prof. James Geikie's 

 "Structural and Field Geologfy," which was 

 reviewed in this journal in 1912 (vol. xc. , 

 P- 159)) nor is it so attractive at first read- 

 ing- as Prof. Wilckens's " Grundziig^e der tek- 



jtonischen Geolog-ie " (Nj\ture, vol. xcii.", p. 564). 



[But it represents the application of close 

 thinking- to the problems of earth-fracture 

 and the displacement of rock-masses in reg-ard 

 to one another, and it forms a specialised 

 manual for the student of all kinds of rock-flow. 

 The larg-e amount of sliding- and differential move- 

 ment that takes place between layers of the same 

 contorted series may be well realised in the field ; 

 but it is not apparent in our ordinary diagrams. 

 Mr. Leith, on p. 114 and elsewhere, very usefully 

 directs attentiori to it, and connects the "drag-- 

 folds " seen on a small scale with the overfolded 



j structure of the Alps, Willis's terms, "com- 

 petent " and "incompetent," which are too familiar 



jin their ordinary usage, are adopted (p. iii) 



jfor layers of rock that respectively resist and 

 yield to compound crumpling-. A fold may 



^exhibit "competence" up to a certain point, and 

 may become "incompetent" on continuance of 



jpressure, yielding^ in this case as a series of folds 

 m which the successive beds are similarly curved. 

 The book is full of matter that leads to accurate 

 realisation, and includes useful reviews of such 

 widely separated terminals of the subject as the 

 origfin of joints and the theory of isostasy. 



(2) In his description of North-west Saxony, 

 t)r. E. Krenkel has the advantag-e of dealing- with 

 a district that includes a palaeozoic rangfe folded 

 NO. 2343, VOL. 94] 



in Middle Carboniferous times, a conspicuous 

 development of Permian strata with associated 

 volcanic rocks, Olig-ocene and Miocene brown 

 coals, and boulder-clay in which Scandinavian 

 g-ranite (rappakiwi) has been found. The com- 

 bination is a happy one for those who study 

 geology at Leipzig, though there is a large gap 

 in the stratigraphical succession. The glacial 

 and fluvioglacial deposits contain the mammoth, 

 Rhinoceros tnercki, and the reindeer. Ice- 

 scratched surfaces are noted at several points, 

 and the dry epoch at the close of the last ice-age 

 has left its traces in the form of grooves etched 

 by wind-borne sand on the porphyry cliffs of the 

 Klein Berg (p. 91). The contact-metamorphism 

 due to granite of Carboniferous age is studied in 

 the last of the excursions, and the question is left 

 open as to whether the associated gneisses are a 

 marginal type of the granite, or an older mass 

 into which the latter has intruded (p. 180). 



(3) The early association of Mr. F. Chapman, 

 now of the National Museum, Melbourne, with 

 the detailed researches of Prof. Rupert Jones 

 gave promise of the accurate contributions that 

 he has made to Australian palaeontology- It is 

 an admirable sign of the times that Great Britain 

 is no longer the field to which problems of the 

 southern hemisphere must be referred. The pub- 

 lication of an introduction to the study of fossils 

 in which Australian examples are primarily 

 employed cannot fail to stimulate observation, 

 and such absorbing details as the "CoUyweston 

 Slate" and the "Oldhaven Beds" may in time 

 drop out of view in examination papers set for 

 our antipodes. At the same time, the author will 

 be the first to recognise that notable gaps in the 

 record must be filled in by reference to other 

 lands. The Triassic cephalopods and almost all 

 fossil mammalia serve as notable examples, and 

 a "students' manual of palaeontology" may be 

 expected to lay a broader foundation than is here 

 given. Mr. Chapman's book, however, is justified 

 by its principal title, and it will be of immense 

 help to workers in Europe who require a ready 

 reference to species recognised on the other side 

 of the equator. The bibliographies following 

 each chapter still further deserve our gratitude. 



(4) Mr. McLeod 's book is bound for the pocket, 

 and contains useful hints for the prospector, who 

 is shown how to perform a number of tests with 

 ingenious and simple apparatus. It is, however, 

 taken for granted that he will not be interested 

 in the reactions involved. The chemical com- 

 position of minerals is loosely stated, and a mixed 

 list of minerals and chemical oxides on p. 81 is 

 styled a list of "ores." The mouth-blowpipe is 

 not relied on ; yet it would reduce cassiterite in 



