2 6o 



NATURE 



[April 29, 1920 



Portugal, and France, where there are many 

 •occurrences pf greater importance than some that 

 receive mention in this book. T. C. 



A Text-book on Machine Drawing for Electrical 

 ■ Engineers. By E. Blythe. (The Cambridge 

 Technical Series.) Pp. vii + 8i. (Cambridge: 

 At the University Press, 1920.} Price 20s. net. 

 All teachers of electrical engineering are aware 

 of the need for a text-book on the drawing 

 and construction of electrical apparatus. This 

 attempt, however, to supply the need is disap- 

 pointing. Apparently the author intends the book 

 to serve for a complete course of machine drawing 

 for electrical students, for he commences with the 

 laws of projection and gives several very simple 

 examples in illustration of them. He proceeds 

 then to 'fastenings, cable sockets, junction-boxes, 

 switches, and dynamos. The subject-matter is 

 confined entirely to such apparatus as is found in 

 small continuous-current power stations (but 

 instruments are not included) ; consequently the 

 alternator, induction motor, oil-switch, and other 

 important pieces of electrical apparatus are notably 

 absent. Several complete plates are devoted to 

 non-dimensioned sketches showing types of ap- 

 paratus, &.g. one on brush-holders ; a few such 

 examples are undoubtedly useful for practice in 

 sketching, but here too much space is occupied 

 in this way. The drawings are clear and very 

 ^well arranged, but the descriptive matter is un- 

 necessarily prolix. The examples given do not 

 always represent good practice ; for instance, in 

 several places a single-piece armature disc is 

 shown with a dove-tailed key, while a bearing is 

 shown on p. 73 which would be destroyed by a 

 little end-thrust. The book is well got up and has 

 been prepared carefully ; but the ground covered is 

 insufficient^at the price. 



Mathematics for Engineers. Part ii. By W. N. 



Rose. (The Directly Useful Technical Series.) 



Pp. xiv-f4i9. (London: Chapman and Hall, 



Ltd., 1920.) Price 135. 6d. net. 

 Part ii. of this book is devoted principally to 

 thfe differential and integral calculus, and includes 

 chapters on spherical trigonometry and mathemati- 

 cal probability. The book is intended for en- 

 gineers, most of whom are not called upon in 

 their profession to show capacity for high 

 mathematical flights, but are expected to com- 

 prehend clearly such fundamental principles as 

 enter into their work, and to be ready successfully 

 to apply them to practical problems. Examining 

 the book from this point of view, we believe that 

 it will find favour with most engineers and students 

 of engineering. If we include also the matter com- 

 prised in Part i. the volumes contain practically 

 everything in the way of mathematical principles 

 which the engineer is likely to require. The treat- 

 ment is clear and of a kind which appeals tO 

 engineers, and a very large number of practical 

 applications are given. Many of these are 

 fully worked out to the arithmetical result, and 

 there are very few which can "be , said to be of an 



; ; NO. 2635, VOL. 105] 



academical nature only. These examples cover a 

 wide field, having been drawn from all branches 

 of engineeering, and represent a large amount of 

 labour for which engineers will be grateful. We 

 can heartily recommend this volume, as well as its 

 predecessor, to all students of engineering. 



The Manufacture of Intermediate Products for 



Dyes. By Dr. J. C. Cain. Second edition. 



Pp. xi-f273. (London: Macmillan and Co., 



Ltd., 1919.) Price 105. net. 

 Probably no one in this country is more com- 

 petent to write on intermediate products than 

 Dr. Cain, and the fact that a new edition of this 

 book has been called for within a year is the best 

 testimony to its success. The opportunity has 

 been taken to improve certain sections and to 

 incorporate new work, most of which, it is of 

 interest to note, originates now in America. It 

 is gradually being realised that intermediates are 

 the crux of the dye situation, and the wisdom of 

 the policy adopted in this direction by British 

 Dyes, Ltd., in building their new factory at Hud- 

 dersfield is becoming apparent. Given the inter- 

 mediates, the manufacture of the several dyes is 

 usually a fairly straightforward problem, but there 

 is still much leeway to make up in connection with 

 intermediates, which will require the most ample 

 resources, alike in capital, plant, and technical 

 experience. This will take considerable time to 

 fructify, and some form of closer co-operation 

 with the heavy chemical trade would appear most 

 desirable. 



The British colour industry is receiving some 

 adverse criticism from the users of the rarer 

 colours for which the demand, at the most, is but 

 small, but it has a more important task at the 

 moment than to fritter away its energies in 

 making these colours. The colour industry is 

 based on intermediates; it is the manufacture of 

 these by the best methods, with the largest yields, 

 and of satisfactory purity which must be studied 

 in the laboratory and in the works. This is being 

 done, and Dr. Cain, through his book, in which 

 the available information is clearly presented, is 

 helping to do it. 



Solutions of the Examples in a Treatise on Differ- 

 ential Equations. By Prof. A. R. Forsyth. 

 Pp. 249. (London: Macmillan and Co., Ltd., 

 1918.) Price I05. net. 

 Even from the point of view of an undergraduate, 

 the subject of differential equations is very differ- 

 ent from what it was fifty years ago. But in a 

 large and miscellaneous collection of examples 

 like this there are a number of survivals which 

 remind us of De Morgan's application of the 

 proverb: "Those that hide know where to find." 

 Teachers and solitary students (if such there be 

 nowadays) will be grateful to Prof. Forsyth for 

 providing them with a key. It is one more 

 example of the author's untiring industry andi 

 so far as we have tested it, of his accuracy in 

 details of analysis. ^^■ 



?^bi 



