5o6 



NA TURE 



[April 22, 1922 



Little. The final value 55-84 is sufficiently far from a 

 whole number to suggest the existence of isotopes, for 

 there is every reason to believe that this value is well 

 established. In view of Dr. Aston's work, and the 

 resuscitation of Front's hypothesis, it will be interesting 

 to learn how the difference from the integer is to be 

 accounted for. Chap. 4 deals with the important 

 subject of the corrosion of iron, of which the editor has 

 made a special study. It is, however, remarkable, in 

 spite of the large amount of work which has already 

 been done on this subject, how much remains to be 

 ascertained. The remaining chapters, five in number, 

 deal with the general properties of iron salts, of its 

 compounds with hydrogen and the halogens, and with 

 the elements of Groups VI., V., IV., and III. of the 

 Periodic Table. The whole concludes with a chapter 

 on the detection and estimation of iron. 



As in the case of the entire work, a special feature is 

 a wealth of bibliographical reference. Practically every 

 statement can be verified by reference to the original 

 source of information. This, of course, adds greatly to 

 the value of the treatise as a compendium, but it is 

 naturally not of much service to the student without 

 access to a well-found library. There is probably no 

 single library in London in which all the books thus 

 referred to could be found. 



A new feature in the work is the inclusion of a table 

 giving a list of important journals and periodicals deal- 

 ing with chemical matters, with the dates of issue of 

 their several volumes, from the year 1800 down to 1 919. 

 It was compiled by Mr. Clifford, the librarian of the 

 Chemical Society, and occupies some eight pages of the 

 book. Its value to the book itself is not very apparent, 

 since the date of publication in the case of any particular 

 reference is invariably given in the footnote. The table 

 has no special appropriateness to the volume under 

 review ; its proper place would be either at the begin- 

 ning or the end of the completed work. 



(3) The " Dictionary of Chemical Solubilities," by 

 Drs. A. M. Comey and Dorothy A. Hahn, is a revised and 

 enlarged edition of a work by the first-named author 

 which appeared in 1895, and which, in its turn, followed 

 the well-known " Dictionary of Solubilities " compiled 

 in 1864 by Prof. F. H. Storer on a plan indicated so far 

 back as 1731 by Peter Shaw. Storer's book is long 

 since out of print, and no attempt has been made to 

 bring it up to date and to reissue it. During the 

 quarter of a century which has elapsed since the first 

 edition of Dr. Comey's work a large amount of addi- 

 tional matter relating to the solubilities of inorganic 

 substances, with which the book is alone concerned, 

 has made its appearance. This has been carefully 

 brought together by Dr. Dorothy A. Hahn, of Mount 

 Holyoke College, and forms the material upon which 

 NO. 2738, VOL. 109] 



the present edition is based. It constitutes a volume 

 of 1 140 closely printed pages, and its subject-matter 

 .has been brought down to 1916. Its printing and 

 publication have been delayed by circumstances arising 

 out of the war. 



In a work of this kind easy reference is of primary 

 importance, and opinions may differ as to the best 

 arrangement to adopt. The one used is practically 

 alphabetical, but it will be obvious that such a scheme 

 leads to occasional anomalies, which could be obviated 

 only by elaborate cross-referencing, thereby adding 

 considerably to the bulk of the volume. In the case 

 of discrepant statements by different observers, no 

 attempt at a critical selection has been made, which 

 we think detracts from the value and authority of the 

 work. A careful examination of the original papers and 

 of the methods and apparatus employed would have 

 enabled a satisfactory judgment to be reached, and 

 thereby obviated much unnecessary printing. Methods 

 of determining the solubilities of gases, for example, 

 have been improved greatly since Bunsen's time, and 

 many of his estimations have been superseded by more 

 accurate observations. It serves no useful purpose to 

 retain them, and indeed only confuses the searcher, who 

 is not in a position to discriminate between the several 

 observers. The compilers may rightly say they have 

 done their best to deal with the enormous mass of 

 material they have collected, but they can scarcely have 

 escaped the conviction that much of the numerical data 

 rests upon a very insecure experimental basis. The 

 fact is, it is only within quite recent times that methods 

 of estimating solubilities have reached the necessary 

 precision, and that sources of error hitherto overlooked 

 have been obviated. 



In spite, however, of these difficulties and imperfec- 

 tions, the present work is the most comprehensive 

 compilation on the subject which has yet appeared in 

 any language, and a word of commendation is due to 

 Dr. Hahn for the patience, care, and assiduity with 

 which she has collected the vast amount of material 

 with which she has had to deal. 



Formal and Philosophical Aspects 

 of Logic. 



Logic. By W. E. Johnson. Part i. Pp. xl-f-255. 

 165. net. Part 2. Demonstrative Inference : De- 

 ductive and Inductive. Pp. xx + 258. 145. net. 

 (Cambridge : At the University Press, 1921, 1922.) 



A LOGICIAN is a person who takes infinite pains 

 to solve problems which present no manner of 

 difficultyto ordinary mortals. This may be, and nodoubt 

 is, because ordinary mortals live and die unconscious of 



