3o6 



KNOWLEDGE & SCIENTIFIC NEWS. 



[December, 1905. 



Magnetic Induction in Iron and other Metals, by Professor J. A. 

 Ewing (Electrician Publishing Office). — We have received 

 a copy of the third edition of this classical treatise. It is a 

 veritable imli: mnum for the electrical engineer, or, indeed, also 

 for the theoretical physicist. Commencing with the simplest 

 definitions of magnetic qualities, the author extends the treat- 

 ment so as to include not only directly magnetic phenomena, 

 but <-ilso a large number of secondary effects which arise from 

 the effects of stress. The general method followed is that of 

 the magnetic circuit, as introduced by J. and E. Hopkinson, 

 a method which is analogous to the electric circuit method for 

 dealing with electric currents. By means of this method 

 great simphfication arises in the solution of problems in con- 

 nection with dynamos and transformers. The chapter which 

 will probably be found the most interesting to readers of this 

 journal is that on " .Molecular Theory," in which it is shown in 

 detail how all the properties of a piece of iron can be imitated 

 by a group of small pivoted magnets. When these are arranged 

 at random the assemblage behaves like non-magnetised iron. 

 When placed in a magnetic field a certain amount of alignment 

 takes place amongst the small magnets ; the assemblage has 

 then all the properties of a magnet, and this is the more so as 

 the alignment becomes more complete. The concluding 

 chapter on " Practical Magnetic Testing " is new to this 

 edition. 



An Introduction to the Study of Colour Phenomena, by J. W. 

 Lo\ibond (E. and F. X. Spon, Limited, London). — The main 

 object of the work described in these pages was the construc- 

 tion of a series of glass standard colour scales, which are 

 correlated to some physical colour constants, and by means of 

 which a colour sensation can be measured, recorded, and 

 reproduced at svill. The author adopts coloured glasses for 

 this purpose, and has had constructed a series of grades of 

 glass of different tints, by comparison with which — taken 

 singly or in combination — any colour can be classified. To 

 physicists who are accustomed to refer all tints to a standard 

 spectrum, specifying each by the wave-length of the light re- 

 ferred to, such an elaborate system of coloured glasses seems 

 not only unnecessary, but somewhat arbitrary. The writer of 

 this notice has seen a box of these glasses, and the standard 

 yellow glass appeared to him to be a distinct citron-green. 

 This in itself is, of course, no serious objection, assuming that 

 the same standard tint can be reproducible at will. To ensure 

 this a comparison is made with a definite thickness of the 

 solution of some pure salt, such as copper sulphate. Although 

 the arbitrariness of the scale of tints makes them useless for 

 scientific purposes, it is possible that they may be of use in 

 the identification of certain manufacturing products. We do 

 not think, however, that their limited utility will repay the 

 enormous labour which has evidently been spent in producing 

 them. This small volume is beautifully illustrated by hand- 

 coloured diagrams. 



Researches on the Affinities of the Elements, by Geoffrey 

 Martin, H.Sc. pp. xii. and 2.S7 (London; Churchill; price, 

 i6s. net.). — Since the days when Newl.inds pointed out that the 

 elements arranged in the order of their atomic weights exhi- 

 bited progressive relationships recurring at certain periods in 

 the series, this " periodic law," as it subsequently became in 

 the bands of Mcndeljeef, has formed the basis of much of the 

 speculation in chemical philosophy, and has borne fruit in the 

 di.scovery of new elements predicted theoretically as necessary 

 to fill gaps in the series. Mr. Martin's ,book also deals with 

 certain aspects of the periodic system, and is a valuable con- 

 tribution to the philosophy of chemistry. It is well known 

 that the various elements differ in their degree of attraction 

 for other elements, but hitherto no systematic attempt has 

 been made to discover whether these affinities varied in accord- 

 ance with any rule. Numerical dat.a are very scanty, and 

 consist of measurements of the heat of combination of the 

 different elements with one another, and hence the author's 

 conclusions have had to be based largely on qualitative differ- 

 ences in the readiness with which parallel conipoimds can be 

 decomposed into their constituents. Hut after making allow- 

 ances for the roughness of the method, it is shown that when 

 the elements arc arranged in their periodic order, their 

 " affinity surfaces," when compared, assume "the positions 

 of an advancing wave " repeating itself at the succes- 

 sive cycles in the system. Full directions for obtaining 

 these geometrical representations or " affinity surfaces " are 



I given, together with a large folding plate showing those of 14 

 I of the more important elements. This " wave law " is illus- 

 trated by an immense amount of experimental results collected 

 from scientific publications and arranged in tabular form. 

 Several other conclusions are drawn from a consideration of 

 the facts, and all are supported by very able reasoning. 

 Unfortunately the style frequently leaves much to be desired, 

 and the book teems with irritating misprints, in addition to 

 the long list of errata given at the end. 



Elementary Chemistry: Progressive Exercises in Experiment 

 and Theory, by F. R. L. Wilson, M.A., and G. W. Hedley, 

 .\I. .A., pp. \ii. and 167 (Oxford: Clarendon Press; price js.). — 

 The authors state in their preface that this book is intended 

 to train the thinking powers of the pupil rather than to fill 

 him with chemical facts, and the series of progressive exercises 

 and questions they have devised appears admirably adapted 

 to carry out this aim. They begin with simple measurements 

 involving the use of the metric system, and then deal with the 

 construction of simple apparatus, the thermometer, the chemi- 

 cal balance, solution and crystallisation, the properties of 

 liquids, and finally the identification of substances by their 

 physical properties. In short, it would be difticult to find a 

 more thorough or complete introduction to physical chemis- 

 try. The book is well printed on good paper, and gives clear 

 illustrations of the apparatus described in the text. 



An Intermediate Course of Mechanics, by Alfred W. Porter, 

 B.Sc. (Murray ; price 5s.). As may be gathered from the title, 

 this book is intended for students at College Lectures, and 

 aims at giving them a clear idea of general principles rather 

 than fulness of details. The subjects of rectilinear translation, 

 momentum, vectors, Ike, are clearly explained, and the mathe- 

 matics introduced are not too deep, as is so often the case in 

 such text books. .\ chapter on the Mechanics of Fluids is 

 added, and appendices give many examples and specimen 

 examination papers. 



The Origin and Influence of the Thoroughbred Horse (Cam- 

 bridge Biological Series, 1905 ; pp. x\ i. and 53S. illustrated ; 

 price, i2s. 6d. net). — Although an arch;i;ologist in place of a 

 naturalist by profession, the author of this well-illustrated 

 volume is to be congratulated on having brought together a 

 vast store of valuable information — nuich of which was diffi- 

 cult of access to the ordinary naturalist — with regard to the 

 vexed question of the origin and distribution of our domesti- 

 cated breeds of horses, and more especially the English 

 thoroughbred and its ancestral type — the Barbs, Turks, and 

 Arabs. It is true, indeed, that he is somewhat vague as to 

 what constitutes a species and a sub-species, or race, and that 

 there are ninnerous inconsistencies and errors in his summary 

 of the existing forms of the liiiiiidu- ; but, as a matter of 

 fact, this part of the subject has comparatively little bearing 

 on the main thesis of his work, and, in our opinion, it 

 would have been no loss had the greater part of this been 

 altogether omitted. 



The author's main contentions appear to be as follows. 

 Adopting the views of previous works as to the distinctness 

 of the thoroughbred stock from that of the horses of 

 northern Europe and northern and central Asia, Professor 

 Ridgeway believes in the existence of three distinct types of 

 horse. Firstly, the Celtic type, from Iceland, the Hebrides, 

 and other parts of north-western Europe. Secondly, the tar- 

 pan, now represented by some forms of the so-called Eipius 

 przeuiilskii, of Mongolia. And, thirdly, the North African, or 

 Barbtype, inclusive of Arabs, Turks, and the modern thorough- 

 bred. The first two are represented by small breeds of large- 

 headed horses, showing a marked tendency to dun-colour, with 

 dark brown legs. From their small size, they were first 

 broken for driving instead of riding, and, owing to their in- 

 tractable disposition, were controlled by means of the bit. The 

 Barb typo, on the other hand, is represented by horses of 

 larger size, with relatively smaller heads, and of more sN-nder 

 build, whose typical colour appears to be Ijay, frequently 

 accompaniird by white " stockings " and a white star on the 

 forehead. Their more tractable disposition led to these horses 

 being controlled by a nose-band in place of a bit, while from 

 their superior size they were in the first instance broken for 

 riding. Northern Africa is held to have been the original 

 home of this stock, which was not introduced into Arabia 

 till a comparatively recent date. Barbs, Turks, and finally 



