802 



NA TURE 



[December 16, 1922 



may begin with no previous knowledge of the subject, 

 it is a well-known device to alternate the theoretical 

 and the experimental sections ; but this method is 

 surelv out of place in a treatise which is so extensive 

 that it can be used only as a work of reference. In 

 such a treatise it is merely an annoyance, and a source 

 of unnecessary trouble to the reader, to break up the 

 text in this way. Thus the systematic account of 

 ozone and hydrogen peroxide is sandwiched between 

 unrelated chapters on the kinetic theory and on 

 electrolysis, to the obvious disadvantage both of the 

 theoretical and the descriptive portions of the book. 

 In the same way, and presumably for the same reason, 

 a valuable section on chemical affinity has been buried 

 in a chapter on hydrogen, together with a section on 

 mass action, while sections on catalysis, on con- 

 secutive reactions, and even on neutralisation, are 

 hidden away in a chapter on oxygen. In each of these 

 cases the index alone gives the clue as to where the 

 author lias concealed his hidden treasures. It is 

 perhaps even more bewildering to discover a long 

 discussion of the indices of refraction of liquids and 

 vapours in a chapter on crystals and crystallisation. 

 In all these cases reference to the theoretical sections 

 is rendered unnecessarily difficult by the way in which 

 certain portions have been detached and redeposited 

 in the systematic chapters of the book. 



A similar confusion between the methods which are 

 suitable for an elementary text-book and those which 

 are required in a work of reference is also to be. found 

 in some of the figures. For example, it would have 

 been much more satisfactory if facsimile reproductions 

 had been given of the apparatus used by Lavoisier for 

 the decomposition of steam by iron, and by Dumas 

 for determining the composition of water, instead of 

 the simplified and modernised versions of the diagrams 

 which are given on pages 130 and 134 of volume 1 ; 

 these can be of no possible value except to a student 

 in the first stages of his chemical education, when 

 simplicity rather than detailed accuracy is perhaps 

 necessary. The figures are, however, not a strong 

 feature of the treatise ; thus, in volume 1 a figure has 

 been omitted on page 89, while on page 214 a block 

 has been printed upside down. On page 007 a block 

 of Iceland spar with strictly rectangular faces is made 

 to show the double refraction of a black spot on a 

 strip of white paper without producing any refraction 

 at all of the paper which carries the spot ; the trigonal 

 axes on page 618 also give the impression of being 

 rectangular, and the rhombohedron of Iceland spar on 

 page 619 does not appear to have been drawn according 

 to any recognisable crystallographic scheme. The 

 diagrams of spectra would also have bun ol greater 

 value if they had been plotted on a scale of wave- 

 NO. 2772, VOL. I IO] 



lengths instead of on what appears to be the arbitrary 

 scale of an instrument. 



At the head of each section a quotation is given, and 

 many of them are particularly apt and interesting ; 

 it is a pity that only the name of the author is given 

 and that the system of references does not enable these 

 quotations to be traced to their source. This difficulty 

 arises also in other cases, e.g. on page 83, where half-a- 

 dozen striking examples of the influence of impurities 

 on the properties of metals are given with the name 

 oi the author but no reference to the place where the 

 [uotations may be found. The author has adopted 

 an ingenious system of numbering separately the 

 references to each section of perhaps half-a-dozen 

 page's, so that no extensive re-numbering is required 

 when additional references are inserted, and each 

 section with its references is complete in itself; but 

 even this excellent system has occasionally failed and 

 most of the minor errors which have been detected in 

 ihc eiirlier chapters have arisen in connexion with the 

 misplaced numbering of the references. It is, how- 

 ever, necessary to enter a protest against the way in 

 which, especially in the systematic portion of the book, 

 a score or more of references are included under a 

 single number. In the case of a student who wishes 

 to consult the whole bibliography of a subject, no harm 

 may be done by this system ; but in the case of a 

 chemist who wishes to look up quickly the original 

 sources from which data have been quoted, this method 

 of handling the references gives rise to much trouble- 

 some delay. To take only one example, on page 84, 

 volume 2, a figure is given of an apparatus by F. P. 

 Worley, and the text corresponding to this figure is 

 close at hand at the foot of the page, but a careful 

 inspection fails to reveal any number or sign with the 

 help of which the reference to this work might be 

 found among the two pages of closely printed references 

 at the end of the section. The numbers which form a 

 guide to the references are in any case not easy to find 

 in a text-book which bristles with the subscript numbers 

 of chemical formulae and the superscript numbers of 

 mathematical formulas and equations ; and it is 

 necessary to go back to the top of page 83 and forward 

 to page 85 in order to discover the numbers 30 and 31, 

 with the help of which the reference to Worley's work 

 is finally traced among the eleven references quoted 

 under the number 30. If this system of quoting 

 references is to be satisfactory, the reader should at 

 least have the assurance that he will not have to go 

 beyond the limits of a paragraph in order to find the 

 number which will lead him to the reference. 



A fault which appears for the first time in volume 2 

 is the introduction of abbreviations into the main 

 portion of the text. These abbreviations may be in 



