196 LIGHT SCIENCE FOR LEISURE HOURS. 



any earthquake-phenomena before observed. Other 

 earthquakes have indeed been followed by oceanic 

 disturbances ; but these have been accompanied by 

 terrestrial motions, so as to suggest the idea that they 

 had been caused by the motion of the sea-bottom, or 

 of the neighbouring land. In no instance has it ever 

 before been known that a well-marked wave of enor- 

 mous proportions should have been propagated over 

 the largest ocean -tract on our globe, by an earth - 

 shock whose direct action was limited to a relatively 

 small region, and that region not situated in the 

 centre, but on one side of the wide area traversed by 

 the wave. 



I propose to give a brief sketch of the history of 

 this enormous sea-wave. In the first place, however, 

 it may be well to remind the reader of a few of the 

 more prominent features of the great shock to which 

 this wave owed its origin. 



It was at Arequipa, at the foot of the lofty volcanic 

 mountain Misti, that the most terrible effects of the 

 great earthquake were experienced. Within historic 

 times Misti has poured forth no lava-streams ; but that 

 the volcano is not extinct is clearly shown by the 

 fact that in 1 542 an enormous mass of dust and ashes 

 was vomited forth from its crater. On August 13, 

 1868, Misti showed no signs of being disturbed. So 

 far as their volcanic neighbour was concerned, the 

 44,000 inhabitants of Arequipa had no reason to anti- 

 cipate the catastrophe which presently befell them. 

 At five minutes past five an earthquake shock was 



