April 23, 1903] 



NA TURE 



1 



junction with this division of the book, as it contains 

 a set of formula;, deduced from Fourier's theorem, with 

 the coefficients worked out, for calculating the har- 

 monics (up to the nth) of an alternating current wave- 

 form. The author states that in all curves actually 

 met with in practice, the 13th and higher harmonics 

 can be neglected, as they are so small. This is, how- 

 ever, not true. It has been recently shown that in 

 (he E.M.F. curve of the alternators of the Glasgow 

 Corporation Tramways, the 13th harmonic is one of 

 the most important, and alternators may very well 

 exist in which the 15th and 17th harmonics are the 

 largest. 



The last division, on polyphase currents, does not do 

 more than show the general star and delta relation- 

 ships, and contains a chapter on the measurement of 

 three-phase power. 



As stated above, the book will be mainly useful to 

 practical engineers who desire to have at hand a 

 volume which will help them out of mental entangle- 

 ments which arise from time to time in working with 

 alternating currents. The general theory (general 

 differential equation) of the electric circuit is not dealt 

 with at all. This being so, we of course find no 

 mention of the exponential terms which vanish with 

 time, and which appear in the full solution of the 

 general equation. These, though airily dismissed by 

 many writers, are really of the utmost importance, as 

 on them depends the theoretical treatment of all the 

 important phenomena met with in electric switching, 

 and oscillations set up by sudden changes in the 

 current flowing. These exponential terms certainly 

 constitute a " Grundgesetz," and as such should have 

 been mentioned. The work is closed by a table of 

 formulae, but that greatest sin of omission, no index, 

 is committed. C. C. G. 



THE PRINCIPLES OF DYEING. 

 The Principles of Dyeing. By G. S. Fraps, Ph.D., of 

 North Carolina College. Pp. xii + 270; with 22 

 illustrations in the text. (New York : The Mac- 

 millan Co.; London: Macmillan and Co., Ltd., 

 1903.) Price js. net. 



IN the preface to this work the author states that " it 

 attempts to apply to the teaching of dyeing the 

 same methods of class-room work, coordinated with 

 experiments in the laboratory, which have proved so 

 successful in the teaching of inorganic chemistry and 

 other branches of science," and its novel feature con- 

 sists in the insertion, interspersed throughout the text, 

 of a series of experiments, seventy-nine in number, 

 which the student is to carry out in the laboratory. 



Although no such division is made by the author, the 

 book may conveniently be considered in two portions, 

 chapters i. to vi. giving a general survey of the subject 

 in 53 pages, while the remaining sixteen chapters, 

 occupying 200 pages, are devoted to a systematic 

 amplification. 



This larger portion of the book follows the lines 

 adopted in most modern text-books on dyeing, and 

 little need be said in reference to it beyond the obvious 

 remark that, even with the most careful condensation, 

 it is not possible, without dangerous generalisations, 



NO. I 747, VOL. 67] 



to compress into 200 small pages any adequate dis- 

 cussion of the various matters treated under the 

 headings cotton, linen, wool, silk, bleaching, scour- 

 ing, machinery, general observations, direct cotton 

 colours, basic colours, acid colours, mordant colours, 

 insoluble colours, mercerisation, dyeing of unions, 

 theory of colour, spectrum analysis, dye testing and de- 

 tection of dyes. The inevitable result of too general 

 statement follows; for example, on p. 251 the follow- 

 ing sentence is found: — " A dye on cloth has nearly 

 the same absorption-spectrum as a solution of the dye 

 of corresponding strength." This is by no means the 

 case, since the hue of the dyed fabric often differs con- 

 siderably from that of a simple solution of the dye. 

 In the same section a normal spectrum is figured, while 

 the description refers to the prismatic spectrum. 



Less importance, however, should be attached to 

 slight errors of statement than to the general scope of 

 the work, and from this point of view the chief interest 

 attaches to the preliminary chapters, to which the 

 author's statement, quoted in the first paragraph, 

 chiefly applies. After a short introductory chapter 

 dealing with the fibres and explanatory of the 

 scheme of the book, the following five sections 

 are each devoted to a study of the composition 

 and characteristics of one of the important groups 

 of dyes, one or two members of each group 

 being used as illustrative of the group. The 

 scheme is well worked out, but sufficient care has not 

 been taken to prevent, what is always a pitfall to 

 students, over generalisation; and instead of giving 

 the student a clear general view of dyeing phenomena, 

 he will probably acquire, by a perfectly logical process, 

 some very erroneous views. For example, chapter vi. 

 is devoted to indigo, chrome yellow, theory of dyeing, 

 and classes of fibres. Now indigo and chrome yellow 

 have absolutely nothing in common, either chemically 

 or in mode of application, and there is not a word of 

 explanation as to the reason for coupling them to- 

 gether until chapter xix. is reached, when it is seen 

 that it is based on the fact that they both form in- 

 soluble pigments on the fibre — a purely artificial and 

 altogether insufficient connection. 



One would expect, in a book of this type, that the 

 various theories which have been put forward to 

 account for dyeing phenomena would receive consider- 

 able attention, but they are not only dismissed in a 

 page and a half, but are quite incorrectly stated. 



The experiments detailed in the text are in most 

 cases well chosen, and add greatly to the value of the 

 book, but a student of inquiring mind may well ask 

 why cotton should be dyed with Congo-red in an alka- 

 line bath and wool in a neutral bath, and the results 

 considered as comparative (Exp. 4). Exp. 12 should 

 certainly be modified. It is highly dangerous to tell 

 a student to pour boiling concentrated sulphuric acid 

 into water, even if the word " caution " is interpolated. 



This book is very welcome as an obviously original 

 attempt to teach the general principles of dyeing on 

 novel lines, and most of its shortcomings are explain- 

 able by the opening sentence in the preface : — " This 

 book is the result of two years' instruction in dyeing." 



W. M. G. 



