February i6, 191 i] 



'NATURE 



503 



tion to what should specially be observed during each 

 of them. In spring" to love-making, song, and nidi- 

 fication, in summer to incubation, nestlings, with their 

 succession of plumages, and in autumn and winter to 

 the congregating of birds in flocks, and to migration 

 and the migratory instincts and such like. A further 

 section is devoted to the added help to field observa- 

 tions to be obtained from the study of cage birds, and 

 to the protection of birds by artificial nests, and in 

 protected woods. The formation of collections, the 

 methods of preserving eggs, skins, and skeletons, the 

 description of the proper instruments for the purpose, 

 and suggestions on the making of anatomical, sys- 

 tematic, faunistic, and specific observations occupy the 

 penultimate sections. The final pages supply some 

 hints on bird observation abroad. 



The volume is illustrated by excellent blocks, many 

 of them being reproductions of Kearton's well-executed 

 photographs. There is also a good index. 



ELECTRICAL ENGINEERING. 



(i) Electric Circuit Problems in Mines and Factories. 

 By E. H. Crapper. Pp. viii+159. (London: Col- 

 liery Guardian Co., Ltd., 1910.) Price 35. 6d. net. 



(2) Exercises in Electrical Engineering for the Use of 

 Second-year Students in Universities and Technical 

 Colleges. By Prof. T. Mather, F.R.S., and Prof. 

 G. W. O. Howe. Pp. v + 71. (London : E. Arnold, 

 1910.) Price IS. 6d. net. 



I ) ' I ""HE publication of this little volume is very 

 -I- opportune. Although the matter does not 

 differ essentially from that found in other books on 

 electrical testing of circuits, the manner of presenting 

 the subject is admirable, and particularly well adapted 

 to the class of reader for which the book is intended, 

 namely, the colliery- or factor}- engineer. There is no 

 padding and unnecessary- scientific verbiage, but 

 directness of treatment, which must be welcome to 

 the busy engineer. In this sense the treatment may 

 be called popular; there is only little mathematics 

 used, and that is of an elementary character, yet there 

 is no sacrifice of scientific accuracy. 



After a short chapter dealing with the units of 

 measurements we get a chapter on the determination 

 of insulation resistance, including tests on live systems. 

 Here the author might with advantage have included 

 Russel's and other tests on three-wire systems. The 

 following chapter, called "Circuit Testing," is mainly 

 concerned with the location of faults on cables by 

 bridge and potentiometric methods, the latter being 

 preferred by 1;he author. Then we come to the con- 

 struction of cables, and what the author has to say 

 on this subject is well worth reading. 



Fmally, there are some chapters on polyphase appa- 

 ratus and working. The only adverse criticism which 

 the present reviewer has to make is as to the appear- 

 ance of this little book. To present so much excellent 

 matter in so poor a guise is not doing the author 

 justice. The paper is too thin and the illustrations 

 are not neat. They are also of varying style, some- 

 times to a large scale, sometimes with fine lines, 

 then again to a small scale, or with unnecessarily thick 

 NO. 2155, VOL. 85] 



lines, making no distinction between lines that are 

 intended to represent bodily objects, and others that 

 are merely diagrammatic. These may seem unim- 

 portant matters to the reader who sits comfortably at 

 his well-lighted writing-table, but let him take the 

 book down a mine to consult it w-hile he is making 

 a test and he will begin to appreciate thick and non- 

 transparent paper, large type, and a systematic method 

 in illustrating electrical connections. 



(2) In this little book the authors have collected 

 the problems and exercises set in recent years at the 

 Central Technical College, both qs regards class work 

 and examinations. All teachers know how important 

 exercise classes are, especially if they are conducted in 

 a similar manner to the ever\'day work of the practical 

 engineer. Now in practical work problems seldom 

 present themselves in the definite manner in which 

 they must necessarily be given as examples in the 

 lecture-room ; the practical problem is often involved 

 or obscured by side issues and part of the work of 

 the practical man is to disentangle it and separate 

 that which really is of importance from that which 

 is merely a small disturbing influence, or without 

 influence at all. To present to students exercises pre- 

 cisely in the same way as problems arise in practical 

 work is, of course, impossible, for it would make the 

 questions too long, but the authors have gone as far 

 in this direction as may reasonably be expected. The 

 questions are such that some preliminary considera- 

 tion is required on the part of the student before he 

 can translate the wording into mathematical form, 

 and that is excellent training for his future work. 



The 427 questions contained in the book are 

 arranged in twenty-four chapters, ranging from the 

 elementary conception of electric circuits to machinery 

 and apparatus in practical use. Not all the questions 

 are set in such way that a numerical answer can be 

 given, many can only be answered in a general way, 

 and these are specially useful, because of forcing the 

 student to think instead of merely to calculate by some 

 rule learned in the lectures or copied out of an 

 engineering pocket-book. Where numerical answers 

 are required the solution is given in an appendix, but 

 the authors recommend that this appendix shall only 

 be consulted after the solution has been found, not 

 before. Some chapters would be the better for a 

 more extended range of problems. Thus in the 

 chapter on commutation we miss the subjects of influ- 

 ence of speed, brush contact resistance, and interpoles, 

 while great stress is laid on shifting of brushes. But 

 nowadays most machines do not require this shifting 

 of brushes, sparkless commutation being obtained by 

 interpoles, contact resistance, or some sort of com- 

 pensating and commutating winding. Again, in the 

 sections dealing with A.C. generators and trans- 

 formers, nothing is found on the subject of heating 

 or the predetermination of the inductive drop. The 

 nomenclature is also peculiar. The authors distin- 

 guish alternators as of the "copper t}-pe," "iron type," 

 and '"inductor type." The last name is generally 

 understood, but for the first two it would be better 

 to retain the usual designation, namely, "without 

 iron " and " with iron " in the armature. These are, 

 however, quite minor blemishes; on the whole the 



