March 23, 1922] 



NATURE 



369 



instruments, and when, towards the end of last century, 

 it was found that, at distances far away from the region 

 affected by the sensible shock, disturbances which were 



Iarly connected with great earthquakes could be 

 :ected by suitable instruments, it was natural to 

 )pose that the origin was the same for both. Only 

 recent years has it been recognised that the earth- 

 ike proper, caused directly by fracturing of the 

 face rocks, is but a secondary effect of a more deep- 

 ted disturbance, or bathyseism, which, and not the 

 thquake proper, is presumably the origin of the 

 disturbance represented in the preliminary tremors of 

 the distant record. 



Meanwhile, seismology has developed on two dis- 

 L.nct lines, and in reality into two distinct sciences, 

 differing in method, means, and requirements. On 

 one hand, we have the newer seismology of the long- 

 distance record, in which personal observation counts 

 for nothing ; some mechanical ingenuity is required 

 for the design of efficient instruments, some care in the 

 maintenance of them and their records, but after that, 

 the discussion and interpretation are purely a matter 

 of the higher mathematics. On the other hand, we 

 have the older seismology, in which there is still much 

 work to be done, even with no further mathematical 

 equipment than an intelligent schoolboy may carry 

 away from a modern public school, but in which the 

 collection of data is entirely dependent on personal 

 observation, and the coincidence of occasion and a 

 competent observer. 



With such a difference of scope and methods, it 

 is scarcely possible for one individual to become a 

 master of both branches, and this is illustrated by the 

 existence of two recent text-books, both nominally of 

 seismology ; first we have the " Modern Seismology " 

 1 the late Dr. G. W. Walker, which appeared some 

 ars ago and is an admirable introduction to the 

 newer development of the subject, but scarcely refers, 

 and only incidentally, to the earthquake proper; 

 then we have this book, by Dr. C. Davison, which is 

 called a manual of seismology and devotes only a part of 

 one chapter to the subject of Dr. Walker's book. The 

 difference accounts for, and is indicated by, the fact 

 that one appeared as a Monograph on Physics, the 

 other as part of the Cambridge Geological Series. 



The object, as well as the scope, of Dr. Davison's 

 work accounts sufficiently for the fact that he devotes 

 only part of a chapter to the newer seismology, and the 

 treatment is adequate, in so far as it gives that amount 

 of information which a student of the older seismology 

 cannot afford to ignore. As a manual of that older 

 seismology the book fills a much-felt want, for we had 

 no satisfactory introduction to the study of the earth- 

 quake proper. Well arranged and clearly expressed, 

 NO. 2734, VOL. 109] 



the only adverse criticism which can be made is that 

 the ground is possibly too fully covered, and that some 

 matters which might have been omitted from an 

 introductory text-book have necessarily received too 

 brief a treatment ; but this fault — if such it be — • 

 is counteracted by the references to other works in 

 which the subject is more fully dealt with. These 

 references to previous literature add very greatly to 

 the value of the work ; not large in number, they 

 are very judiciously selected, form a satisfactory basis 

 for advanced study in all branches of the subject, and, 

 without exception, are such that no one wishing for a 

 mastery of the subject could afford to leave them 

 unstudied. R. D. 0. 



Chemical and Physical Constants. 



Handbook of Chemistry and Physics. A Ready- 

 Reference Pocket Book of Chemical and Physical 

 Data. By Prof. C. D. Hodgman, assisted by Prof. 

 M. F. Coolbaugh and Cornelius E. Senseman. 

 Eighth edition. Pp.711. (Cleveland, Ohio : Chem- 

 ical Rubber Company, 1920.) 3 dollars. 



THIS compact little volume contains a vast array 

 of chemical and physical constants. Since the 

 first publication in 1914 it has passed through eight 

 editions in the United States — a sufficient proof of 

 its utility as " a comparatively comprehensive reference 

 book for use in the laboratory or classroom." 



The tables on the properties of inorganic and organic 

 compounds are very complete, and chemists will 

 appreciate particularly the tabular information on the 

 solubility of inorganic salts in water. The data on the 

 " Dehydration of MetaUic Sulphates " and the " De- 

 composition of Anhydrous Metallic Sulphates" are 

 distinctly novel features. In the qualitative analysis 

 scheme it is somewhat difficult to follow out the 

 behaviour of chromium. A very complete table is 

 given of heats of formation and solution, but it is to be 

 regretted that no indication is given as to the sources 

 from which the data have been compiled. 



The section devoted to physics is fairly complete, and 

 one notes with pleasure that the table for the reduction 

 of psychrometric observations refers to the ventilated 

 type of wet and dry bulb thermometer only. At the 

 end of the volume eight pages are devoted to problems, 

 the utihty of wh h in a book of data is doubtful. 



The book has some blemishes, for the most trust- 

 worthy data have not always been chosen. To take 

 one example only, in the table of " Fixed Points for 

 High Temperatures " the melting point of nickel is 

 given as 1427° and that of platinum as 1775°. Ten 

 years ago the Carnegie Institution published a memoir 

 on High Temperature Gas Thermometry, and the values 



O I 



