NATURE 



[November 3, 1904 



who can realise much higher prices by selling early in 

 the season. Prof. Lemstrom calculated that in the case 

 of wheat the outlay on a field of 25 acres will be repaid 

 in two or three years, and that afterwards a net profit 

 of 40/. a year or more can be realised. We cannot here 

 enter into the details of the working, such as the best 

 time of electrification, the effect of wet and dry weather, 

 and so forth, but we should strongly advise those 

 interested in the subject to study this book carefully ; 

 they will find it full of valuable suggestions, and the 

 time spent in reading it will be amply repaid. 



(3) We have already reviewed the first three volumes 

 of this publication, so that it is only necessary here to 

 refer briefly to the matter contained in the present 

 volume. This is devoted to electric tramways, and 

 is divided into seven chapters, dealing with overhead 

 construction, feeders, surface contact systems, con- 

 duit systems, rolling stock, electric boats and motor 

 cars, and electric traction on railways. The defects 

 to which we alluded in our previous review are not 

 so noticeable in this volume, which furnishes a good 

 description of a very important branch of electrical 

 engineering. The excellence of the illustrations is a 

 characteristic of the whole production, and is a par- 

 ticularly valuable feature in the present instance, as the 

 subjects are such that they cannot be effectually de- 

 scribed without numerous photographs and diagrams. 



(4) This exceedingly interesting monograph on the 

 much debated theory of the chemical reactions taking 

 place in the lead accumulator is probably already well 

 known in the original German to those who have con- 

 cerned themselves specially with this subject. Since 

 the book first appeared the discussion has progressed 

 a stage further, so that the English translation may 

 be said to be out of date to a certain extent. This is, 

 however, the penalty that the average English student 

 has to pay for the neglect of his schoolmasters to 

 teach him German, and he will probably therefore 

 welcome the appearance of an English translation. 

 Herr Dolezalek treats the subject from the standpoint of 

 Nernst's osmotic theory, and shows that thermo- 

 chemical considerations all point to the validity of the 

 sulphate theory originally advanced by Gladstone and 

 Tribe. Whether the author will succeed in satisfying 

 others to the same extent as he has apparently satisfied 

 himself may be regarded as open to question, but in 

 any case the book is one which cannot be neglected by 

 anyone wishing to study this complicated but fascin- 

 ating problem. 



(5) The design and construction of electric motors 

 is becoming daily a matter of more importance to 

 electrical engineers on account of the very rapid 

 extension of the use of electricity for power purposes. 

 When one considers the enormous number of tramcars, 

 lifts, factories, &c. , which are driven by electricity, it 

 is easy to see not only how important the subject is, but 

 also how very varied is the work which the electric 

 motor is called upon to perform. If the development 

 now is great, in a few years' time, when some of the 

 numerous power schemes are more matured, it will be 

 much greater still. The student of electrical engineer- 

 ing may find here ample scope for his abilities, and he 

 cannot consult a better guide than the volume before us. 



NO. 1827, VOL. 71] 



The book is divided into two parts, the first dealing 

 with continuous and the second with alternating 

 current motors. The relative advantages of different 

 tyoes are considered in detail, and there are numerous 

 calculations of motors of different types and capacities. 

 In addition, there are a large number of curves, 

 diagrams, and photographs. 



(6) The essays which are comprised in M. Cornu's 

 little book were written with a special and rather 

 peculiar object, the author having been requested by 

 some of his old pupils, who had been unable to keep 

 touch with the rapid development of electrical engineer- 

 ing, to write for them something which would enable 

 them to appreciate better the technical or semi-technical 

 literature of to-day. These " Notices " are conse- 

 quently of a somewhat elementary character, nor can 

 the book be regarded in any sense as a text-book of 

 electricity. But M. Cornu has succeeded in writing a 

 book which should appeal to a very much larger 

 audience than that for which it was originally in- 

 tended; one cannot look through its pages without 

 realising at every point that it is the work of a master, 

 and such works repay study by all — the most advanced 

 as well as the most elementary students. The be- 

 ginner will find here ideas expressed clearly and 

 concisely, and cannot fail to derive great benefit from 

 the book as an introduction to more detailed treatises. 

 The engineer will see well known facts expressed in 

 new and suggestive language, and will doubtless have 

 his own views enlarged in consequence. The subjects 

 dealt with are the correlation of the phenomena of 

 static and dynamic electricity, generators, transmission 

 of power and polyphase currents, and we would 

 strongly recommend anyone interested in any of these 

 matters to spend a few hours reading M. Cornu's 

 admirable booklet. 



(7) We cannot help being conscious that the end of 

 1904 is rather late in the day to review a book which 

 contains a resume of the technical achievements of 

 1903. Still, as we gather that this publication is 

 intended to appear annually, this notice may be of 

 some service in directing readers' attention to the 

 volume dealing with this year's progress, which we 

 imagine will appear very soon; in addition, it may be 

 pleaded that the lapse of time enables one to see matters 

 more in the right perspective, and so to form a better 

 estimate of the value of M. Da Cunha's work. The 

 book ranges over a great variety of subjects. Thus 

 we find at one place a mathematical calculation of the 

 mechanical problems involved in " looping the loop," 

 and in another a discussion of alcoholism and temper- 

 ance worthy of the columns of a daily paper in the 

 silly season. Between these extremes lie such subjects 

 as the progress in wireless telegraphy, automobilism, 

 aerial navigation, and the hundred and one other 

 technical developments which are taking place in all 

 branches of applied science. To the engineer the book 

 can serve no other purpose than to while away an idle 

 hour or so. The general reader who is interested ir» 

 scientific and technical progress may read it with both 

 profit and pleasure. He will find the descriptions clear, 

 the style agreeable, and the illustrations and diagrams 

 in many cases excellent. .M. S. 



