70 



NATURE 



[September 25, 1919 



though lucrative, slaughter which is at present 

 hapi>ening in the southern hemisphere and else- 

 where is rapidly leading both the larger Cetacea 

 and a valuable industry to extinction. 



Lydekker's remark that the Addo Bush 

 elephants "are specially protected" causes , a 

 pang when we recollect that the statement is no 

 longer true. No naturalist could hear of the 

 recent decision to exter-ninate this most interest- 

 ing herd without grief. One may be pardoned 

 for wondering whether much more would be 

 heard either of the damage done by these 

 elephants or of the project to exterminate them 

 if the authorities, in granting the licence to kill, 

 were to stipulate that the whole of the profits of 

 the chase should be expended upon obtaining such 

 a series of specimens, photographs, and casts as 

 would form an adequate memorial of the threat- 

 ened race for the use of zoologists and compara- 

 tive anatomists, and that the balance, if any, 

 should be applied for the purposes of zoological 

 research in Africa. 



To conclude, we would reiterate that this book 

 contains a vast amount of most interesting and 

 valuable information brought together by a man 

 of unrivalled experience and ability ; this informa- 

 tion is most lucidly conveyed throughout, and 

 many passages in the work are quite charming. 

 The illustrations, on the whole, are very good, 

 and some of the coloured plates may fairly be 

 called magnificent. Our sole regret is that Mr. 

 Lydekker did not require a theme. 



M. A. C. H. 



WATER IN ACTION— CONTROLLED AND 

 FREE. 



(i) Irrigation Engineering. By Dr. A. P. Davis 

 and H. M. Wilson. Seventh edition, revised 

 and enlarged. Pp. xxiii + 640. (New York: 

 John Wiley and Sons, Inc. ; London : Chapman 

 and Hall, Ltd., 1919.) Price 215. net. 



(2) Shore Processes and Shoreline Development. 

 By Prof. D. W. Johnson. Pp. xvii + 584. 

 (New York : John Wiley and Sons, Inc. ; Lon- 

 don : Chapman and Hall, Ltd., 1919.) Price 

 23s. net. 



(i) A FTER passing through six editions, this 

 ■^*- work, originally composed by Mr. 

 Wilson in 1896, has been recast and largely re- 

 written with extensive additions by Dr. A. P. 

 Davis, whose own book on " Irrigation Works in 

 the United States " was reviewed in Nature for 

 June 20, 1918. It speaks much for the merits of 

 a technical work that it should reach a seventh 

 edition, and the present issue will undoubtedly 

 maintain the reputation gained by its predecessors. 

 The .scope of the treatise is wide — admittedly 

 too wide for complete treatment — and the object 

 kept in view, and that very successfully, has been 

 to present a general outline of the whole field of 

 irrigation work, including its history, the 

 chemistry of soils and soil treatment, sources of 

 water supply, methods of application and 

 NO. 2604. VOL. I04.1 



measurement, construction of canals and dams, 

 drainage and sewage disposal, water rights, 

 surveys and preliminary investigations, and 

 systems of operation and maintenance. It is 

 obvious that, even in a volume of 600 odd pages, 

 matters so many and so varied could not be 

 treated exhaustively, and that some must receive 

 less attention than, perhaps, is their due. The 

 chapter on masonry dams, for instance, would, 

 in our opinion, have admitted with advantage of 

 some amplification in respect of the fundamental 

 law of the middle third, and some account of the 

 theory of vertical shearing stresses, especially as 

 the book is intended primarily as a manual for 

 engineers. 



On the other hand, there are to be found on 

 nearly every page practical notes of considerable 

 utility. Moreover, at the end of the volume is 

 the complete specification, running to fifty-six 

 pages of small print, of the contract for the con- 

 struction of the Arrowrock dam in Idaho. This, 

 in itself, will prove of inestimable value to the 

 practising engineer for reference purposes. There 

 are also a number of tables with useful data, and 

 computed results of various formulae. 



Another restriction, which must be noted and, 

 perhaps, is inevitable, is that, with one or two 

 rare exceptions, all the examples illustrated are 

 chosen from American practice. It is true that 

 the Assuan dam is mentioned, and that Indian 

 irrigation is not without notice, but the book is 

 written almost entirely from the American point 

 of view. Possibly it gains in interest and value 

 in this way, since the authors thus confine them- 

 selves to cases in which they speak with experi- 

 ence and authority. 



The illustrations, both photographs and dia- 

 grams, are excellent throughout. It is a most 

 valuable and informative book, in a compre- 

 hensive way, on a subject which materially affects 

 farmers, geologists, meteorologists, engineers, 

 chemists, and business men, as well as the 

 highest interests of the State. 



(2) A work of some 550 pages, in which a list 

 is given of 416 authorities cited, and the refer- 

 ence's in one chapter alone amount to 187, cannot 

 fail to impress the reader with the erudition of 

 its author and the immense labour he must have 

 taken to collect his data. We pay a tribute, in 

 passing, to the unremitting zeal and perseverance 

 which have produced so concise a compendium of 

 opinion on a subject which, on account of its 

 complexity, is little understood and yet is of the 

 greatest scientific interest. 



The book is compiled on methodical lines. 

 Each chapter opens with an "Advance Sum- 

 mary " and closes with a "Resume." The first 

 and second chapters deal with waves and their 

 work, the third with currents, and the fourth with 

 shore classification. The ensuing six chapters 

 contain an exposition ■ of theories of shoreline 

 development. 



The earlier part of the volume is largely his- 

 torical and retrospective ; it reviews the data 

 obtained by experimentalists in the past, with the 



