282 



NATURE 



[June 13, 1918 



ment. This is largely due to the great extension 

 of the gas-mantle industry, which, in its exploita- 

 tion of the sources of thorium and cerium, has 

 placed at the disposal of investigators relatively 

 large quantities of material more or less rich in 

 "rare earths." Indeed, in the case of certain of 

 these substances the term "rare earths " is a mis- 

 nomer. Some of them have been found to be 

 widely distributed and to occur in large amounts. 

 Accordingly, the literature on these elements has 

 been largely augmented during the last few 

 decades, as its loibliography shows, and it has 

 needed no inconsiderable skill on the part of Mr. 

 Little to deal with it within the limitations of 

 space necessarily imposed upon him. The biblio- 

 graphy reveals how very slight and comparatively 

 unimportant have been the contributions of 

 German chemists to this literature. Up to the 

 present there are some fifteen "rare earth" 

 elements (excluding actinium) the identity of 

 which may be considered as established, and all 

 of these have been discovered by Scandinavian, 

 Swiss, or French chemists. An Austrian chemist, 

 Auer von Welsbach, resolved Mosander's didymia 

 into its components, and he shares with Urbain 

 the credit of proving that Marignac's ytterbia 

 was complex. Investigators of the type of Klap- 

 roth, Bunsen, and Wohler are, apparently, no 

 longer to be found in Germany. The work of en- 

 larging our knowledge of a particularly interesting 

 group of elements of great theoretical importance 

 and rich in possibilities of technical application is 

 rapidly passing into the hands of Anglo-Saxon 

 chemists, and especially of American chemists, 

 who have not only devised adequate methods 

 of separation and isolation, but have also inci- 

 dentally contributed a great amount towards the 

 chemical history of the individual metals. 



We can unreservedly congratulate Mr. Little on 

 the production of a particularly useful work. If 

 the rernaining^olumes of the series maintain the 

 same high level, the entire treatise will constitute 

 a most valuable contribution to our chemical 

 literature. 



THE CONSTRUCTION OF HARBOURS. ' 

 A Treatise on the Principles and Practice of 

 Harbour Engineering. By Dr. Brysson Cun- 

 ningham. Second edition. Pp. xvi + 377. 

 (London: Charles Griffin and Co., Ltd., 1918.) 

 Price 255. net. 



T^HE second edition of this standard work has 

 -*■ been revised and brought up to date; much 

 new matter has been added — including numerous 

 additional illustrations — nearly a further hundred 

 pages. Many of the points briefly referred to in 

 the first. edition have been elaborated, so that its 

 pages are now crowded with useful information. 



Chap, v., dealing Avith "Piling," is one of the 

 most instructive in the book. Timber versus re- 

 infdrced-Goncrete piles is discussed, also the vari- 

 ous methods of pile-driving. The sustaining power 

 of piles, and the prevention of destruction of piles 

 caused by decay or by marine organisms, are ablv 

 NO. 2537, VOL. IOl"l 



dealt with. The Hennebique and other forms of 

 steel sheet-piling are described and compared with 

 timber sheet-piling. 



The introductory chapter deals, among other 

 matters, with the , national interest in harbours, 

 which will doubtless be more marked after the war 

 than it was previously, for undoubtedly the State 

 will take over many of our principal harbours, and 

 in many cases enlarge them. Chap, ii., dealing 

 with "Harbour Design," has been dealt with in 

 a most exhaustive manner, and the author has 

 done well to include particulars and illustrations of 

 that harbour which has probably caused more dis- 

 cussion than any other — the. Madras Harbour, the 

 projection of which has resulted in such a huge 

 accumulation of sand on the windward side 

 (due to the south-west monsoon), necessitating 

 the spending of large sums annually in 

 dredging inside the harbour ; while the havoc 

 wrought by erosion on the lee side, due to the 

 trapping of the sand by the harbour, is most 

 serious. The effect of rivers flowing through har-r 

 hours has had due consideration in the book, but 

 the cause of bars occurring at the mouths of 

 harbours, and the suggested means for removing 

 these, have not been dealt with so fully as one 

 would have washed. 



The chapters on "Breakwater Design" and 

 "Breakwater Construction" deal very fully with 

 these subjects, and many excellent details of con- 

 struction are given, which would only occur to a 

 practical author ; the additional plates which have 

 been added to these chapters increase their value 

 immensely. Figs. 154-59, showing the construc- 

 tional staging at Gibraltar Harbour Works, are 

 admirable. 



One is disappointed to find no reference made 

 to slipway construction at a time like the present, 

 when so many slipways are being laid down ; and 

 the notes on the action of sea water on concrete 

 might have been extended. A few more examples 

 of failures in breakwaters, either through faulty 

 foundations or storms, would have added to the 

 value of the .book, for, after all, the engineer 

 learns more from failures than from successe's. 



The use of reinforced-concrete in harbour 

 engineering has not been given the, prominence in 

 the book that one would have desired, especially 

 its use in the construction of jetties. .The effect 

 upon reinforced-concrete piles of their being alter- 

 nately submerged in sea water in tidal work and 

 exposed to air does not appear to be referred to, 

 and this is at the present time a very debatable 

 subject. The mechanical handling of material 

 might have occupied more space in the book, and 

 the use of reinforced-concrete ,in the building of 

 lightships and in the construction of lighthouses 

 might have* been discussed. 



The chapter dealing with ," Surveying, Marine 

 and Submarine," will be most useful to . civil 

 engineering students, the course of procedure 

 being clearly set out and, w-ell. illustrated, and the 

 notes on this subject are very practical. 



The chapter on "Channel Demarcation" is in- 



j teresting, as.it deals with lighthouses, lightships, 



and buoys, while that, on " Pier-heads, Quays, and 



