O'Eeilly — 071 Localities marked by Earthquakes. 511 



Thus, examining the Rhine valley earthquake district, it may be 

 observed that not only is it well defined on the west by the east coast 

 of England direction, but that, moreover, the locality of relatively 

 greatest intensity, which may be taken as corresponding to Gross 

 Gerau, occurs at the intersection of the great circle direction, Axis of 

 Sumatra (jSTo. 28), with the parallel to the coast of England passing 

 through Elba. 



•Furthermore, the great circle direction ISTo. 56, Promontory of New 

 Ulster, passes somewhat to the south thereof at Strasburg and Carls- 

 ruhe, and defines sufiiciently the northern boundary of the Saxony 

 central earthquake district. This district may, indeed, be defined as 

 bounded on the north-west and south-east by this great circle, and a 

 parallel thereto, and on the north-east and south-west by the great 

 circle, east Cape of Madagascar (No. 2), and a parallel thereto. This 

 great circle (No. 2), and those representing the east and west coasts of 

 the Red Sea, are very characteristic in their intersections, and all pass 

 through Iceland, and would suggest a possible connexion between the 

 volcanic and earthquake activity of that island and localities situated 

 on these great circle directions. Such connexion or simultaneity of 

 action at points of a coast-line direction wide apart is demonstrated 

 by the repeated occurrence of shocks at Grsechen in Switzerland and 

 Constantinople, on the same day and nearly same hour, both points 

 being situated on a parallel to the north-east coast of the Persian 

 Gulf (No. 32). It is evidently of extreme importance to follow out 

 these relations, since, if established for points at great distances on 

 great circle directions, every new relation thus established between 

 phenomena apparently isolated and unconnected points towards a law, 

 and would be of a nature to guide physicists as to the localities whereat 

 seismographs may be most advantageously established for observation. 



These considerations lead up to the examination of the second point 

 which I proposed to consider, that is, the relations to be established 

 between these coast-line directions considered as great circles and loca- 

 lities situated outside Europe, and noted for the frequency or intensity 

 of their earthquakes. In order to do so in a summary manner I have 

 detailed the points through which these great circles pass, printing in 

 thick type the known earthquake localities, and in italics those known 

 only on account of volcanic action. 



No. 2.— EAST CAPE MADAGASCAR. 



Antigonil Bay. 



Astone and Cosmoledo Islands. 



Abyssinia, , . . Near Gondar. 



Nile, . . . .At Syene, First Cataract, Mineah. 



Mediterranean Coast, . Arabs Gulf. 



Candia, .... Near Cape Sidero. 



Sporades. 



Eubcea Island, . (Twelve miles east of). 



Killodroini Island. 



