LIGHT SCIENCE FOR LEISURE HOURS. 



expresses it, explosive) force which is only to be looked 

 for immediately above the centre of concussion. 



Yet the consideration of the evidence afforded by 

 the news we have just published seems at first sight 

 somewhat opposed to this view, and to point rather to 

 a seat of disturbance lying considerably to the west of 

 the Peruvian shores. e At Chala,' says our informant, 

 ( the sea receded, and a wave rose fifty feet, and re- 

 turned, spreading into the town a distance of about a 

 thousand feet. Three successive times everything 

 within range was swept away, followed by twelve 

 shocks of earthquake, lasting from three seconds to 

 two minutes.' The arrival of great sea-waves before 

 the land-shocks were felt seems decisively to indicate 

 that the seat of disturbance lay beneath the ocean and 

 not beneath the land. We are disposed to believe, 

 however, that in the confusion of mind naturally 

 resulting from the occurrence of so terrible a catas- 

 trophe, the sequence of events may not have been 

 very closely attended to, for in other places the arrival 

 of the great sea- wave is distinctly described as follow- 

 ing the occurrence of the earth-shock. At Arica, for 

 example, a considerable interval would seem to have 

 elapsed before the terrible sea-wave, which has always 

 characterised Peruvian earthquakes, poured in upon the 

 town. The agent of the Pacific Steam Navigation 

 Company, whose house had been destroyed by the 

 earth-shock, saw the great sea-wave while he was 

 flying towards the hills. He writes : ( While passing 

 towards the hills, with the earth shaking, a great cry 



