Jn.2 



NATURE 



[April 24, 19 19 



The war may now be over, and these special 

 occasions for service may no longer exist. But in 

 the long new struggle before us the need for scien- 

 tific training and method is as great as ever. Our 

 capital is gone. We must pay our debts and 

 earn our living, and, besides, we must amend the 

 pre-war conditions of our workers' lives. It cannot 

 be done except by making every use of the know- 

 ledge we have already, and by labouring to add 

 to it : that is to say, by following scientific 

 methods. The services of the laboratory-trained 

 men will still be indispensable. That there is a 

 general understanding of the position is shown by 

 the crowding of new students into the universities, 

 and the demand for instruction in science. 



But where are the teachers and the apparatus 

 for teaching? Even before the war the salaries, 

 especially of the junior staff, were poor and the 

 positions few. Many of the former teachers 

 will not come back, for some have been lost in 

 the war, and others are being attracted by the 

 better prospects of research laboratories and com- 

 mercial work. The universities have no funds 

 wherewith to meet the proper increases of salaries 

 or any increase of staff, for their grants remain 

 unchanged, all expenses have increased, but they 

 may not raise their fees. The number of students 

 is growing rapidly, and, as things are, increase in 

 numbers generally means an increase in expendi- 

 ture. Most of the universities are really unable 

 to carry on without increased aid from the State. 



The sowing of the seed is the last thing that 

 may be neglected if there is to be a harvest, and 

 all our experience, thrown Into strong relief by 

 the war, shows that the harvest of the successful 

 development of the work of this country, work 

 which is to pay our uebts and bring comfort to 

 our peoples, will follow only on the application of 

 scientific method and research, which is the seed 

 sown In universities and technical schools. 



FOUNDATIONS OF ELECTRICAL THEORY. 

 The Theory of Electricity. By G. H. Livens. 

 Pp. vi + 717. (Cambridge: At the University 

 Press, 1918.) Price 305. net. 

 ipLECTRICAL theory, the most rapidly grow- 

 -»— ' ing part of physics, has now reached such 

 dimensions that no author can hope to produce a 

 text-book which will deal effectively with Its many 

 aspects. A series of such books is necessary 

 which shall take different points of view and lay 

 especial emphasis In certain broad directions. We 

 already have several, and notably the works of 

 Jeans and Richardson, which are both compara- 

 tively recent. But lafcunae remain, and one of 

 these the present author has set out to fill. We 

 may say at the outset that he has filled it with 

 considerable success, for the work now before us 

 NO. 2582, VOL. 103] 



in no way constitutes a reduplication of any im- 

 portant part of an existing treatise. It is, more- 

 over, one which can be recommended without 

 reserve to a student who is anxious to obtain a 

 clear picture of the fundamental principles under- 

 lying certain important, and often rather 

 neglected, aspects of electromagnetic theory. 



This is said advisedly, for the feature of the 

 book which makes the strongest appeal to the 

 reader Is probably the excellent ■ account of that 

 much-discussed and rather chaotic subject, the 

 energy, stress distribution, and general mechani- 

 cal relations of polarised media. Matters of this 

 kind are usually presented very imperfectly to the 

 student, in spite of the classical foundation which 

 exists in papers by Larmor, and the author has 

 done good service In directing attention to them 

 by their incorporation. In a consistent and very 

 complete form, within the compass of a treatise 

 of this size. If any other section of the work 

 were selected as deserving of special mention, it 

 should probably be that devoted to conduction 

 of electricity by metals, with some of the small, 

 though fundamental, phenomena which accom- 

 pany It. The author has himself contributed a 

 great deal of work to the subjects described In 

 these sections, and is especially qualified to give 

 an effective account of them. 



The preface describes the work as largely "the 

 outcome of a course of lectures delivered ten years 

 ago by Sir Joseph Larmor. We may express 

 regret that such a fine compliment is so rarely 

 paid to those who lecture by members of their 

 audience. Although dealing with a mathematical 

 subject, the mathematical side Is kept under con- 

 trol by the author, who does not expound It 

 beyond the point necessary for a real compre- 

 hension of the principles Involved, and an insight 

 into the manner in which they must be worked out 

 in detail. References to the more complete or 

 elaborate investigations are provided as footnotes, 

 and, though by no means exhaustive, these are 

 sufficiently numerous to direct the reading of those 

 who wish to pursue special sections of the subject. 



There are two main divisions of electrical theory 

 at the present day, both extensive. In the first 

 place, we have the original framework of Faraday 

 and Maxwell, developed for systems in motion by 

 Larmor, and just afterwards, with more gene- 

 rality, by Lorentz. Superposed on this is the 

 more speculative side, including the principle of 

 relativity, theories of atomic structure, photo- 

 electricity, and other branches, together, in fact, 

 with all the phenomena for which the quantum 

 theory has been invoked. We call this section 

 speculative only by comparison, in that its mathe- 

 matical and logical foundations and inter-connec- 

 tions are of a lower order of security. It has been 

 well developed in existing treatises, and is not 

 seriously touched upon in the present work. The 

 need for a comprehensive treatise on the older 

 form of theory, satisfactory from the point of 

 view of mathematical and physical consistency, if 

 not always capable of Including certain pheno- 

 mena within its scope, has always been felt, and 



