372 



NATURE 



[November i8, 1920 



bearing upon points concerning which fuller in- 

 formation was desired. The address takes the 

 form of a general survey of the present position 

 and outlook of education in this country, and of 

 the part that co-education may be expected to play 

 in its development. 



The author defines education as the training of 

 life, for life, by life. We must think of the child 

 as a living organism with immense and varied 

 possibilities. The purpose is to give these possi- 

 bilities the fullest opportunity of development quite 

 irrespective of the child's future vocation, and 

 concerned only with the point of view of his posi- 

 tion as an actual and potential member of the 

 community. Mr. Badley's contention is,' as a 

 result of twenty years' experience at the Bedales 

 residential school for both sexes, that the full 

 value of education in its widest aspect cannot be 

 attained for either sex unless both be taught to- 

 gether during the whole period of school and 

 student life with such differentiation as physical 

 and psychical conditions demand. It is a carefully 

 reasoned statement worthy of the serious atten- 

 tion of all educators. We are face to face with 

 the making of a new world, in the fashioning of 

 which men and women will share equally, and in 

 the common educational training of both sexes the 

 problem will find its most effective solution. Such 

 is the view of the author of this most inspiring 

 address. 



A Text-hook of Electrical Engineering. Trans- 

 lated from the German of Dr. Adolf Thomdlen. 

 By Prof. George W. O. Howe. Fifth English 

 edition. Pp. xi-t-482. (London : Edward Arnold, 

 1920.) Price 28s. net. 



A NUMBER of minor alterations which have 

 been introduced into this edition increase 

 its value. For instance, the symbols have been 

 modified, when necessary, so as to bring them 

 into line with the recommendations of the Inter- 

 national Electrotechnical Commission, and descrip- 

 tions of obsolete machines have been omitted. 

 The theory of the single-phase commutator motor 

 has been extended, and students will find the 

 theorems given simple and instructive. We can 

 recommend the book to those who want a general 

 survey of the whole elementary theory of electrical 

 machinery. 



It is assumed throughout that the alternating- 

 current waves follow the harmonic law ; this 

 greatly simplifies the analysis. We should like 

 the author to have laid greater stress on the 

 limitations of the theorj- due to the assump- 

 tions which have been made. Owing to hysteresis, 

 for instance, the waves do not follow the harmonic 

 law, and although the error introduced by the 

 assumption may be small, it makes it difficult — 

 if not impossible — to judge of the relative merits 

 of some of the alternative diagrams given, as 

 they are all affected to varying extents. ^ 



We notice that the translator defines the slip 

 of an induction motor as the difference between 

 the number of revolutions per second of the stator 

 NO. 2664, VOL. 106] 



magnetic field and of the rotor. It is more cus- 

 tomary now to define it as the ratio of this differ- 

 ence to the revolutions per second of the stator 

 field. Defined in this way, the slip is a pure 

 number, and the mathematical equations of the 

 induction motor are simplified. 



Governors and the Governing of Prime .Movers. 

 By Prof. W. Trinks. Pp. xviii4-236. (London: 

 Constable and Co., Ltd., 1920.) Price 225. 6d. 

 net. 



This book is probably the only one in the English 

 language which deals exclusively with governing, 

 the subject being usually dealt with in text-books 

 on prime movers. The author's aim has been to 

 produce a book of essentials and principles, put in 

 a form which will enable the reader to judge exist- 

 ing and future types of governors ; there are no 

 catalogue pictures. The author does not pretend 

 to have covered the whole field of governing ; thus 

 the mathematical side has been restricted to the 

 usual undergraduate standard ; and he projects a 

 further volume for the use of engineers who have 

 to make governing a life study. 



Among the other subjects treated in the volume 

 will be found discussions on the governor as a 

 motor and as a measuring instrument, promptness 

 and traversing time, adjustment of equilibrium 

 speed, shaft governors, natural period of vibration 

 of governors, interaction of the governor and the 

 prime mover, rate-of-flow, pressure and relay 

 governors, governor troubles and remedies. There 

 is also a very useful chapter on discarded tyf>es 

 of governors. In all these the treatment is clear, 

 and there is a large number of line drawings, 

 which will be of assistance to the student. Since 

 there are no makers' illustrations, the book is 

 equally suitable for British and American students, 

 and we can recommend it with confidence. 



Portraits of Scientists. 11 in. by 14 in. -f margin. 

 (The Class-room Portrait Gallery, 7 Queen 

 Square, W.C. i.) Price 6s. 6d. each, or 30s. 

 the set of five. 



These collotype portraits have been produced with 

 the view of meeting the need for instructive 

 decoration in classrooms, lecture halls, and labora- 

 tories. The publishers hope that, while helping 

 to create an atmosphere of culture, the portraits 

 will also supply a background for much solid in- 

 struction woven around the lives of great men. 



The difficulties met with, at present, in the 

 choice and provision of artistic, decorative, and 

 educational pictures for secondary schools and 

 other institutions are such that any attempt at 

 improvement in this direction is welcome. How- 

 ever, the paper of the present issue and the artistic 

 effect of the portraits leave much to be desired. 

 The series includes Galileo, Sir Isaac Newton, 

 Michael Faraday, J- Clerk-Maxwell, and Lord 

 Kelvin ; and it is proposed to prepare a further 

 series, incuding chemists and other men of science 

 of to-dav. 



