THE transmission of electrical energy has now become a very important engineering problem. It is not surprising, therefore, that the literature on the sub j ec t is increasing very rapidly. The expert finds a difficulty in keeping abreast of the advancing tide of knowledge. Consequently, there is room for a book which describes the latest developments in the theory of transmission. This book is written by two capable engineers, and it is interesting to notice how they have collected, from the advanced treatises and papers they have studied, the theorems which have great practical value whether they are easy to understand or not. On p. 11, for example, we come across Maxwell's coefficients of capacity and potential. The schoolmaster in us objects, however, to such statements as “It will be obvious that p12 = P21”. This kind of assertion we come across in examination papers. In these cases we take it to mean that the examinee does not see it himself but hopes that it is obvious to the examiner. What pleases us most about the book is that it is thoroughly up-to-date, and that only really important practical theorems are given. There are some defects in methods of proof, but in no case, so far as we have noticed, is the defect serious. We confess to feeling annoyed every time we come across Kirchhoff's name spelt with only one h. One of the most valuable chapters in the book is on the relative value of earthing as compared with insulating overhead high tension networks. In Great Britain we generally use solidly earthed neutrals. In Germany they are earthed through Petersen coils, so called after their inventor, Prof. Petersen, of Darmstadt. At the present time, there is scarcely sufficient operating experience available to determine which system is the best; but the authors state the problem clearly.
Electrical Power Transmission and Interconnexion.
. (The Specialists' Series.) Pp. xi + 424. (London: Sir Isaac Pitman and Sons, Ltd., 1930.) 30s. net.