October 13, 1904J 



NATURE 



575 



and at the same time the most complete, is further 

 illustrated by seven large folding lithographed plates. 

 These are bound at the end of the volume. 



Suffice it to say that this piece of work is a matter 

 for congratulation to Prof. Disselhorst, and its publi- 

 cation a credit to all concerned. 



Francis H. .\. Marshall. 



SPECTRUM ANALYSIS. 

 An IiilroiUiction to the Study of Spectrum Analysis. 

 By W. Marshall Watts, D.Sc, F.I.C. Pp. vii + 

 325. (London : Longmans, Green and Co., 1904.) 

 Price los. 6d. net. 



IT is somewhat remarkable that, in spite of the 

 great interest and importance of the subject, 

 there are few, if any, text-books on spectrum analysis 

 which really meet the requirements of beginners who 

 desire to take up the matter practically. The 

 announcement of an introductory work by the well- 

 known compiler of the " Index of Spectra," how- 

 ever, led to the hope that this gap in the literature 

 of the spectroscope would at last be adequately filled, 

 but it is disappointing to find that the needs of the 

 practical student are again almost disregarded. 



The book includes a brief account of the optical 

 principles underlying the different forms' of spectro- 

 scope, and general explanations of the methods of 

 producing and mapping spectra, besides which there 

 are short statements relating to the arrangement of 

 lines in series, and the applications of the spectro- 

 scope to the study of the heavenly bodies. When 

 it is stated that nearly half the book is occupied by 

 wave-length tables, and that there are 135 illustra- 

 tions — many of them large ones — it will be seen that 

 the general treatment can scarcely be otherwise than 

 sketchy. The descriptions of the modes of procedure 

 are consequently often lacking in details which would 

 have been of the greatest use to the student. Thus, 

 with reference to the spectra of gases, the only 

 method of observation indicated is that of a ready- 

 made Geissler tube, which, as the author remarks, 

 does not always show the spectrum of the gas 

 present in the greatest proportion ; it would have 

 been useful to explain how the student might 

 examine the spectrum of a gas collected or prepared 

 by himself. Later on, there is a short account of 

 stellar spectra, but no directions whatever as to how 

 such a spectrum may be observed. 



.Another verv serious defect from the student's point 

 of view is the use of the arbitrary scale of Bunsen in 

 the maps and earlier descriptions of the charac- 

 teristic lines of the different elements. It is after- 

 wards shown how such measurements may be 

 reduced to wave-lengths, but surely it would have 

 been better to define the various lines by their wave- 

 lengths from the very beginning ; as it stands, a 

 great deal of unnecessary labour is involved in the 

 comparison of the descriptions and maps with the 

 wave-length tables given at the end of the book. 



The book, in fact, leaves a great deal to be 

 NO. ^824, VOL. 70] 



desired, whether considered as a laboratory guide or 

 as a descriptive work. Many important facts are 

 left unnoticed, though space might have been found 

 for some of them by the omission of superfluous or 

 insufficiently described illustrations. In the section 

 on nebulae, for instance, there are no less than eight 

 diagrams showing the telescopic appearances of these 

 objects, but no reference to the fact that all nebulae 

 do not exhibit bright line spectra ; the reader is, more- 

 over, likely to get the wrong impression that the chief 

 nebular line is due to nitrogen. 



Though brought well up to date in some respects, 

 the book is far behind the times in others. It is 

 erroneously stated (p. 106) that the spectrum of 'the 

 solar corona includes lines of helium, hydrogen, and 

 calcium, and the important subject of enhanced lines 

 in relation to many celestial spectra is overlooked 

 altogether. 



Many other examples of the shortcomings 10 which 

 attention has been drawn might be given, but the 

 above will sufficiently indicate that the selection of 

 material has not been judiciously made. By far the 

 most valuable feature of the book is the series of 

 abridged tables of wave-lengths, showing the more 

 important lines in the spectra of nearly all the 

 known chemical elements. 



OUR BOOK SHELF. 



Text-hooks of Physical Chemistry. — Electrochemistry. 



Part i. General Theory. By R. A. Lehfeldt, D.Sc. 



Pp. viii + 268. (London : Longmans, Green and Co., 



1904.) Price 55. 

 SmDENTS of physical chemistrv have to-day no cause 

 to complain of a dearth of books upon the subject. 

 There are a considerable number of large volumes 

 treating of this branch, and now we have the series of 

 text-books edited by Sir William Ramsay. The book 

 under review is the second of the series, and has been 

 entrusted to Dr. Lehfeldt, who is well known as a 

 worker on the physical side of electrochemistry. 



Dr. Lehfeldt has not followed any hard or fast line 

 laid down by previous writers upon the subject, and 

 for this reason the book may be read with more than 

 ordinary interest. The book is divided into three 

 chapters, which might perhaps better be designated 

 parts i., ii., and iii. Chapter ii. is written by Mr. 

 T. S. Moore, and deals with the relation of chemical 

 constitution to conductivity. This chapter is very care- 

 fully thought out and arranged, and the author has 

 consulted the latest literature. It deals, in the first 

 place, with the relation of charge carried to constitu- 

 tion, this portion being reallv a repetition and enlarge- 

 ment of what has already been dealt with in the 

 previous chapter. In fact, chapter ii. is to a certam 

 extent an addendum to the first chapter, but it should 

 in no wise be skipped bv the student who desires to 

 comprehend the bearing of electrochemistry on chemical 

 problems. Other points treated in this chapter are 

 relation of the number of ions in solution to constitu- 

 tion, pseudo acids and bases, amphoteric electrolytes, 

 and so on. 



Chapter i. commences with a description of certain 

 voltameters. We would rather that the author had 

 adopted the term coulommeter, because the instru- 

 ments are for measuring current and not potential. 



