August 17, 1893] 



NA TURE 



36- 



written in his usual clear and popular manner, but the 

 prevailing impression is decidedly that of disproportion. 

 Too much space is occupied by the personalities which 

 were unfortunately too frequently shown in his controver- 

 sial methods, and by details of a comparatively unimport- 

 ant character ; while essentials are, as we have pointed 

 out, frequently incompletely dealt with or even entirely 

 omitted. 



Mr. Ranyard's portion is admirably written, is very 

 thoughtful and suggestive, and is a valuable contribution 

 to our knowledge of the stellar universe and the condition 

 and distribution of matter in external space. Indeed, 

 the comparative brevity of this portion of the book is its 

 chief fault, and a condensation of the earlier portion to 

 allow of the expansion of this would greatly increase 

 its value to the student, and would certainly not lessen its 

 interest to the general reader. A. T. 



EARTHQUAKES. 



Erdbebenktinde. Die Erscheinungen und Ursachen der 

 Erdbeien, die Methoden threr Beobachtungen. Von Dr. 

 Rudolf Hoernes, o.o. Professor rler Geologie und 

 Paktontologie an der Universitat G.az. (Leipzig: Veit 

 and Co., 1893.) 



Etude sur les Tremblenienls de Terre, Par Leon Vinot. 

 (Paris and Nancy: Berger-Levrault et Cie, 1893.) 



IN a recent article in this journal, entitled " Seismology 

 in Japan" (see Nature, June 8, p. 136) attention was 

 directed to the long series of memoirs which deal with 

 the methods and results of earthquake-observation, and 

 have appeared in the Transactions of the .Seismological 

 Society of Japan, or its successor, the Seismological 

 Journal of Japan. Any advance in our knowledge of 

 the phenomena or causes of earthquakes resulting from 

 the study of the frequently occurring shocks in Japan is 

 largely due to the untiring efforts of the editor of those 

 Journals, Prof John Milne, and to those of the school of 

 active seismologists, whom he has educated and inspired 

 with some of his own enthusiasm. We can best judge, 

 perhaps, how far advances of our knowledge on this 

 difficult and obscure department of physics and geology 

 have been real and of permanent value from the examina- 

 tion of text-books and general treatises, in which sum- 

 maries are given of the latest and most important 

 researches upon the subject. 



The two works whose titles appear at the head of this 

 article, and which have recently made their appearance 

 in Germany and France respectively, may well serve the 

 purpose of illustrating what is the high-water mark of our 

 knowledge at the present time concerning these remark- 

 able but little understood phenomena. 



If we compare these two books with their numerous 

 predecessors, the first peculiarity which strikes us is the 

 classification of earthquake-phenomena, based on the 

 supposed causes of the disturbance of equihbrium in the 

 earth's solid crust, which have been adopted by the 

 ' recent authors. While the older writers took for granted 

 the close connexion between seismological and vulcano- 

 logical phenomena, so that " earthquakes and volcanoes " 

 were almost always discussed in the same treatise, the 

 two works before us afford distinct evidence that this 

 MO. 1242, VOL. 48] 



conviction has now been very seriously shaken. It is 

 true that nearly all great volcanic outbursts have been 

 attended by eatth-tremblings ; but it is equally true that 

 some of the grandest displays of seismic energy have 

 occurred in areas that have not at any recent period been 

 the scenes of volcanic activity ; and both the German and 

 the French author admit the existence of great classes of 

 seismic disturbances, which have no necessary connexion 

 with any manifestations of volcanic energy. 



Dr. Hoernes classifies earthquakes under the four head- 

 ings : " Vulkanische Beben," " Einsturzbeben," " Dis- 

 locationsbeben," and " Relaisbeben." M. Vinot tieats 

 of them under the following heads :—" Tremblementsde 

 terre suivis, d'druptions ou lids directement a Taction 

 volcanique;"" Tremblementsde terre dus encore a Taction 

 direct dufeu central, mais sans manifestation consecutive 

 du volcanisme ; " and, lastly, " Tremblements de terre 

 independent de Taction volcanique." 



But with this recognition of the class of non-volcanic 

 earthquakes the resemblance between these two books 

 ceases. Dr. Hoernes commences his work with an ad- 

 mirable account of the speculations on the nature and 

 causes of earthquake-phenomena which have ap- 

 peared from the earliest times. His comprehensive 

 sketch begins with extracts from the writings of 

 Hebrew prophets and Greek philosophers, and ends with 

 references to the Seismological Society of Japan. The 

 two chapters which follow on earthquake-phenomena and 

 earthquake-observation ari clear and useful summaries 

 of the most recent researches on the subject, and are well 

 brought up to date. Supplied as they are with drawings 

 and descriptions of seismographic apparatus, they afford 

 one of the best guides with which we are acquainted to a 

 general knowledge of the principles and methods of 

 seismological investigation. 



M. Vinot commences his work with a chapter on the 

 nebular hypothesis and the proofs of the existence of 

 central heat within the earih. He insists that, to explain 

 the phenomena of earthquakes, it is necessary to assume 

 the existence at a depth which certainly does not exceed 

 " quelques centaines des kilometres," of a mass of in- 

 candescent liquid materials, which he argues must consist 

 of molten metals in which are dissolved certain gases. 

 The subsequent chapters of his book are a series of 

 deductions from these premises. It will thus be seen 

 that the methods and plan of the German and French 

 au'.hors are about as diverse as can well be conceived. 

 Tiie German work abounds with references by means of 

 which the student who is not satisfied with the summary 

 statements in the text is enabled to put himself into 

 com.munication with the memoirs of the original in- 

 vestigator whose views have been cited. The French 

 work is simply a readable essay, in which we have none 

 of these valuable aids to study. The illustrations of 

 M. Vinot's book consist of several page plates, repro- 

 duced from photographs, and representing the now- 

 destroyed terraces of Rotomahana in New Zealand and 

 the country affected by the eruption of Tarawera but the 

 connexion of these illustrations with the text is by no 

 means obvious. 



In two works so diverse in their plan and execution as 

 are those before us, it is interesting to note yet another 

 and somewhat unexpected feature which they present in 



