November ii, 19 15] 



NATURE 



283 



(1( struction of this tribe, but for this a heavier 

 11 sponsibiHty rests on the Micmacs. Mr. 

 llowley's book tells all that can now be dis- 

 ci vered about them. Even if it shows lack of 

 literary skill and in some places might have been 

 \\\\\\ advantage abridged, it is an adequate record 

 of a regrettable chapter in the history of the 

 colony. In its format and illustrations it is 

 worthy of the traditions of the Cambridge Uni- 

 ^ ( rsity Press. 



THE RESISTANCE OF SHIPS. 



Ship Form, Resistance, and Screw Propulsion. 

 By G. S. Baker. Pp. vii + 247. (London : 

 Constable and Co., 1915.) Price 12s. 6d. net. 



THE author of this book is the superintendent 

 of the William Froude experimental tank 

 at the National Physical Laboratory, and it is 

 with the results of model experiments in this and 

 other such tanks that the greater part of the book 

 is concerned. While there is little new material 

 in the book, it forms a valuable collection of 

 collated data in. ship form and resistance research, 

 and from this point of view should be useful to 

 the student of naval architecture and to the de- 

 signer to whom the services of an experimental 

 tank are available. Full reference has been made 

 throughout to the work of Taylor, Biles, Froude, 

 and Peabody. Such research results as the 

 author considers to be of permanent value have 

 been collected and analysed, and although 

 opinions will differ as to the value of much of 

 the great mass of matter which has been ignored, 

 the book shows evidence of much care in sorting 

 and examining published data. 



The book is divided into two sections, the first 

 dealing with "Ship Form and Resistance," and 

 the second with "Screw Propulsion." In the 

 first and most successful part of the book, the 

 theory of ship resistance, with its dependence on 

 skin friction and on eddy and wave-making re- 

 sistances, is first considered. The effect of form 

 and of variations of form on these separate 

 sources of resistance is considered in detail, and 

 much attention has been paid to the analysis of 

 experimental data bearing on this part of the 

 work. Particular emphasis is laid on the import- 

 ance of the " prismatic " or " longitudinal " 

 coefficient of a vessel, as opposed to its "block" 

 coefficient. Experiment clearly shows that the 

 resistance of a ship, and more particularly the 

 form of its resistance-speed curve, depends chiefly 

 on the longitudinal distribution of its displace- 

 ment. A large part of this first section of the 

 book is devoted to the effects on resistance of 

 varying lengths of entrance, run, and parallel 

 NO. 24.02, VOL. q61 



middle body, work with which the author's own 

 investigations have been largely concerned. 



There is a useful chapter on the form and re- 

 sistance of high-speed vessels of abnormal type, 

 including hydroplanes and the floats of seaplanes, 

 and k further chapter deals with the effect on 

 resistance of varying depths of water and of re- 

 striction in the waterway of narrow channels. 



The second portion of the book deals briefly 

 with the various theories of the screw propeller; 

 with the elements of screw propulsion ; and the 

 design of propeller blades. Screw efficiency, 

 with the allied questions of hull efficiency, wake 

 deduction, and thrust deduction, are clearly ex- 

 plained in a very satisfactory series of chapters. 

 A chapter is devoted to a consideration of the 

 phenomenon of cavitation, and one to a brief 

 sketch of the main engine. This forms the least 

 satisfactory portion of the book. In the chapter 

 on cavitation there is much loose definition and 

 I lack of precision, which will probably be rectified 

 in any further edition, while the chapter on the 

 main engine is very superficial. The book would 

 not suffer appreciably by the deletion of this 

 section. The final chapter touches briefly on the 

 tabulation, plotting, and analysis of measured- 

 mile trials. 



The book as a whole is well arranged and has 

 a good index. 



OUR BOOKSHELF. 



Elementary Lessons in Electricity and Mag- 

 netism. By Prof. S. P. Thompson. New 

 Edition. Pp. xvi + 744. (London : Macmillan 

 and Co., Ltd., 191 5.) Price 45. 6d. 

 This well-known book has become almost a 

 classic for tliose beginning the study of elec- 

 tricity and magnetism. It is an encyclopaedia 

 of information on all things electrical. A new 

 edition of a volume that attempts so much, in a 

 science which develops so rapidly as electricity, 

 must suffer many changes, and the new volume 

 contains two interesting new chapters — one on 

 wireless telegraphy, and the other on the modern 

 conception of the electron. It is a tribute to Prof. 

 Thompson's skill as an expositor that he deals 

 in a short chapter with such difficult problems as 

 those involved in the consideration of the oscilla- 

 tions in the coupled circuits of a high frequency 

 oscillation transformer. The chapter on electrons 

 is also a welcome addition. The author has 

 managed to compress into a dozen pages as much 

 information on this subject as is usually con- 

 tained in books of much larger size. 



It is a matter for regret that Prof. Thompson 

 has not stated Ohm's law as it is generally 

 understood at the present time. Ohm's law as 

 stated by Ohm, without the condition of unaltered 

 physical prof>erties, is not a law at all. In the 

 text it is stated that the "resistance of a given 



