274 



NATURE 



[May 5, 1910 



unduly critical of all other evidence is a fault on the 

 right side. He has succeeded in including work 

 which appeared almost up to the time of publication 

 of the book, and has produced a most valuable account 

 of what is known of the subject. 



AMERICAN GEOLOGY. 

 Geology : Shorter Course. By Thomas C. Chamberlin 



and RoUin D. Salisbury. Pp. xviii+978. (London : 



John Murray, 1909.) Price 21s. net. 

 A College Text-book of Geology. By the same. Pp. 



xviii+978. (New York : Henry Holt and Co., 



1909.) 



THESE are respectively the English and American 

 editions of the same work, and each weighs 

 3 lb. 10 oz., without in any way approaching the 

 dimensions of a German " Handbuch." We are not 

 clear in this case if the insertion of an English title- 

 page adds to the price of the work ; but we note that 

 the larger text-book by the same authors costs 63s. 

 in London and 505. in New York. This " shorter 

 course " is not one that could be used in colleges in 

 our island, except as a description of the geology of 

 North America; while as a reference-book on this 

 subject and on the valuable original views of the 

 authors the larger work is manifestly superior. 



It is a misfortune, which often must be felt in our 

 own colonies, that text-books on natural history re- 

 quire a local setting and foundation ; even the first 

 413 pages of Messrs. Chamberlin and Salisbury's 

 shorter course, dealing with physical geology, are 

 almost entirely illustrated from American sources, and 

 are, of course, all the better on that account, in view 

 of the intentions of the authors. Maps of the United 

 States Topographic Survey are utilised effectively, as 

 in Mr. Salisbury's treatise on physiography; and 

 the photographs of landscape-features, such as the 

 rippled sand-dune on p. 100, the Bad-land topography 

 on p. 135, and the dust-cloud of Pel^e on p. 381, are 

 so beautifully reproduced that we cannot blame the 

 publishers for their choice of heavy paper. " La 

 Croix," by the by, in the description of the last- 

 mentioned picture, should be Lacroix ; " Gyrvan " on 

 p. 406 is our Scottish Girvan ; and " the Achaischen 

 earthquake " on p. 348 is surely an accidental hybrid. 

 The esker of Punkaharju, shown on p. 273, is not in 

 Scandinavia, but in Finland. But there are very few 

 misprints in this handsome volume. 



The account of glacial phenomena is of especial 

 interest, and the views of various writers as to glacier- 

 motion are carefully stated (pp. 280-8). There is 

 probably less difference between the views of Tyndall 

 and James Thomson (not "Thompson") than is here 

 suggested; Tyndall himself wrote in his "Forms of 

 Water," 



"the gist of the Regelation Theory is that the ice of 

 glaciers changes its form and preserves its continuity 

 under pressure, which keeps its particles together." 



He does not appear to have insisted upon actual 

 fracture as necessary to glacier-motion. 



Other interesting discussions are that of the 

 planetesimal origin of the solar system, which is here 

 NO. 2 1 14, VOL. 83] 



concisely treated (p. 420), and that of the depth to 

 which water from the surface may penetrate tht earth 

 (p. 197). Excellent diagrams are given of the effects 

 of faulting and folding on the outcrops of strata on a 

 level surface. 



In the stratigraphical section of the book, we may 

 note that an Archeozoic era is accepted, its rocks 

 being in part sedimentary, but lying unconformably in 

 most places beneath those of the Proterozoic (Algon- 

 kian) era. Diagrammatic maps after De Lapparent 

 are given to show the distribution of certain strata in 

 Europe; but their scale is too small to render them 

 serviceable as guides. That of the Devonian system, 

 for example, allows of the existence of only the Lower 

 Devonian series in the British Isles, and the disposi- 

 tion of the Devonian lakes in Wales and Ireland is 

 singularly capricious. Maps of North America are 

 given for each system, usefully discriminating between 

 actual outcrops and conjectural extensions. 



The Carboniferous period is divided into a lower 

 Mississippian and an upper Pennsylvanian period ; the 

 Cretaceous into Comanchean and Cretaceous proper. 

 This last subdivision, however, raises exactly the 

 same difficulties as the attempt to restrict Silurian to 

 the upper part of the old Silurian system. European 

 readers will gain greatly from the last half of the 

 book. Though they cannot accept it as their only 

 text-book of geology, they will recognise at all points 

 the ontrinalitv and perception of the authors. 



G. A. J. C. 



ELECTRIC WAVES IN THEORY AND 

 PRACTICE. 

 (i) Electric Waves. An Advanced Treatise on Alter- 

 nating-current Theory^ By Prof. W. S. Franklin. 

 Pp. X + 315. (New York: The Macmillan Co.; 

 London : Macmillan and Co., Ltd., 1909.) Price 3 

 dollars net (los. net). 



(2) Wireless Telegraphy and Wireless Telephony. 

 An Elementary Treatise. By Prof. A. E. Kennelly- 

 Second edition. Pp. vii+279. (London : T. Fisher 

 Unwin, 1909.) Price 4s. net. 



(3) Wireless Telephones and How They Work. By 

 Dr. J. Erskine-Murray. Pp. iii+68. (London : 

 Crosby Lockwood and Son, 1910.) Price is. 6d. 



net. 



(4) Handbook for Wireless Telegraph Operators. 

 Published for official use. October, 1909. Price 3d. 



(i) T)ROF. FRANKLIN'S treatise, although by its 

 1 title it might be expected to deal more par- 

 ticularly with that class of electric waves used in 

 Hertzian telegraphy, deals with the whole subject of 

 electromagnetic waves, and is more adequately de- 

 scribed by its sub-title. Indeed, the subject of wire- 

 less telegraphy is given, if anything, less than its fair 

 share of attention on the ground that it is already 

 adequately treated in Fleming's "Principles of 

 Electric Wave Telegraphy." It is to be wished that 

 all authors showed a similar moderation and restraint. 

 The volume opens, after a brief introductory chapter, 

 with two chapters on water waves and wave trains, 

 which serve as a useful introduction to the principal 

 ideas of wave motion. The next four chapters deal 



