3^ 



NATURE 



[September 8, 192 1 



point of view, the calculation of centres of gravity 

 and moments of inertia, leading up to a detailed 

 treatment of the theory and calculation of bend- 

 ing moments, shear forces and stresses in beams 

 under various conditions of. loading and of sup- 

 port. The application to the aeroplane then fol- 

 lows, the forces on the main plane structure, the 

 fuselage, and the control surfaces, in flight and 

 on landing, being considered in turn. A chapter 

 of particular interest is that on the partially dis- 

 abled aeroplane. Questions of detail in design are 

 dealt with next, followed by an account of the 

 methods of testing. 



From the mathematical and mechanical point 

 of view the chapter on the " principle of least 

 work " deserves special attention. The principle 

 is a statement of the fact that for a structure in 

 stable equilibrium the work function is a mini- 

 mum, and the authors show how it can be used 

 " to find the stresses in structures which are static- 

 ally indeterminate — i.e. in structures with too 

 many members." 



There are three appendices. The first consists 

 of tables of values of what are called Berry func- 

 tions. As Prof. Bairstow puts it in his preface, 

 "the most accurate method of calculation of spar 

 stresses yet known is due to Mr. Arthur Berry, 

 . . . and by the help of a number of tables which 

 he compiled the work is not unduly laborious." 

 The functions thus tabulated are : — 

 f{e) = 6{26 cosec 26 - \)l{2e)\ 0(^) = 3(i - 26 cot 26)l{26)\ 



F(^) = 6( I - 20 cosech 26)j{26)\ ^(d) = 3(26 coth 2d - i)l{26)\ 

 ^{6) = 2,{6-\2inh6)l6\ 



Values are also given for tanh 6. The second 

 appendix reproduces the " materials specifica- 

 tions " issued by the Air Ministry from time to 

 time, while appendix 3 gives the aerodynamical 

 characteristics of various types of aerofoils. 



The book is illustrated by twenty-one plates 

 and 259 diagrams. It is an authoritative account 

 of one of the most important aspects of aero- 

 plane design, as well as of aeroplane theory, and 

 will no doubt be the standard work on the subject 

 in English for some considerable time. 



S. Brodetsky. 



A Text-book on Oceanography. 



A Text-hook of Oceanography. Bv Dr. J. T. 



Jenkins. Pp. x-l-2o6. (London: Constable 



and Co., Ltd., 192 1.) 155. 



" 'Tf^HE higher forms of schools, teachers in 



J. training, and students attending schools 



of Geography in the Universities " constitute the 



audience for whom this book is intended. It is a 



short summary of the more salient results of physi- 



NO. 2706, VOL. I08I 



cal oceanography, and as such it is, on the whole, 

 a well-balanced statement. It is based on the 

 well-known " Handbuch der Ozeanographie " by 

 Dr. Otto Kriimmel. Dr. Jenkins follows the same 

 line of treatment, and borrows from the matter 

 of this authoritative w-ork. 



As Dr. Kriimmel 's book was published in 

 1907, the work before us neglects matters of much 

 interest that have been investigated since that 

 date. Thus there is comparatively little about 

 hydrobiological phenomena, and the modern ionic 

 theory of solution is not dealt with in spite of the 

 great importance of recent work. The section 

 on the composition of sea-water suffers by this 

 omission. It is not quite accurate to say that 

 "radio-activity is not observable in sea-water," 

 and the young student may find some difficulty in 

 the statement made that, " if the electric con- 

 ductivity of pure water be taken as nil, then that 

 of sea-water at 0° C. and of salinity 35 per mille 

 will be 0-0293 ohms." 



The section on the tides is badly done. There 

 are several misprints in the expressions given for 

 the tidal potential, and these may trouble inex- 

 perienced readers. Moreover, it is stated that 

 " the numerous calculations necessary in the har- 

 monic analysis can be performed by a machine — 

 the tidal predictor." There are said to be four 

 of these machines in existence, and that one of 

 them belongs to the British Government. This 

 does us too much credit : the British machine is 

 privately owned, and there are really more than 

 four in existence. As a matter of fact, the British 

 tide-tables published by the Admiralty are also 

 privately computed. 



Is it correct to say that the form of waves is 

 trochoidal? Cold surface water does not sink 

 down at the Poles because of its greater density, 

 but flows superficially and in a southerly direction 

 for a considerable distance because of its low 

 salinity before it sinks to the bottom. Recent 

 work by the Scottish Fishery Board shows that the 

 direction of flow of water in the north-west part 

 of the North Sea may take the reverse direction 

 to that represented on p. 182. 



Apart from such mistakes, and in spite of a 

 certain lack of appreciation on the part of the 

 author of the spirit and method of modern marine 

 research, the book is sure to be useful to just 

 the kinds of students mentioned in the preface. 

 But it is too small (and dear), and it is badly 

 illustrated. The figures are all borrowed, and 

 the sources of many of them are unacknowledged. 

 From the point of view of the student the index 

 is bad. J- J- 



