Reviews — Milne's Seismological Journal. 371, 



Tfif-ft in tlie country where they have been most widely and success- 

 fully studied. 



More than nine-tenths of the volume is occupied with two great 

 catalogues. In the first of these we find the time of occurrence of 

 every earthquake, the extent of ^aHcZ-area shaken, and figures which 

 by reference to an index-map give the approximate position of the 

 epicentre and the boundary of the disturbed area ; in the second, 

 the lengths of the axes of the disturbed area (thus giving the total 

 area), the distance of the epicentre from the shore when submarine, 

 and the seismic district to which the earthquake belongs. The 

 importance of the catalogues will be evident from this brief 

 summary. 



In the prefatory pages, Prof. Milne gives an account of some of 

 the first results which have been derived from a study of these 

 materials. Mr. Omori has investigated the distribution of after- 

 shocks in space and time, and has already published an important 

 memoir on the subject (see "Natural Science" for June). On a 

 reduced index-map, the distribution of seismic centres in Japan is 

 clearly exhibited. From this we learn that the central portions 

 of the country are remarkably free from earthquakes, and it is 

 interesting to notice that these are the very districts where mountains 

 and active volcanoes are prevalent. The greater number of earthquakes 

 originate along the eastern coast of the empire, from the face of the 

 steep monoclinal slope which Japan presents towards the Pacific 

 Ocean. The chief anticlinal axis of the island runs N.N.W. and 

 S.S.E., and, from the southerly prolongation of ihis axis, earthquakes 

 from time to time originate. Again, along lines of great slope 

 (1 in 20 to 1 in 30) earthquakes are frequent, while they are rare 

 where the slope is gentle ; and they are numerous in those districts 

 where there are evidences of secular elevation or depression. A map 

 has also been drawn, though not published, which shows the dis- 

 tribution of earthquakes accompanied by sound. Generally, it 

 appears, sound is heard in rocky mountainous districts, while on the 

 alluvial plains it is but rarely observed. 



Several of the Japanese earthquakes have been propagated as 

 far as Europe, and have been recorded by horizontal pendulums. 

 Dr. E. von Rebeur-Paschwitz, who has studied the records of these 

 instruments with great ability and success, contributes a list of 301 

 seismic disturbances recorded by them in different parts of Europe 

 and at Teneriffe. At least seven of these disturbances were due to 

 Japanese earthquakes. The preliminary tremors are estimated to 

 travel with a surface-velocity of 12 km. (about 8 miles) per second, 

 while the larger oscillations follow at a much slower rate. What is 

 the true nature of these remarkable movements, how they travel — 

 whether in straight or in curved lines, whether along the surface or 

 right through the interior of the earth, — these are the new problems 

 which are set before seismologists to solve, and to which their 

 attention is now being closely directed. C. Davison. 



