222 LIGHT SCIENCE FOR LEISURE HOURS. 



this time three considerable waves rolled in upon the 

 town. But clearly these waves must not be compared 

 with those which in other instances had made their 

 appearance within half an hour of the earth-throes. 

 There is little reason to doubt that if the separate 

 oscillations had reenforced each other earlier, Callao 

 would have been completely destroyed. As it was, a 

 considerable amount of mischief was effected ; but the 

 motion of the sea presently. became irregular again, and 

 so continued until the morning of August 14th, when 

 it began to ebb with some regularity. But during the 

 14th there were occasional renewals of the irregular 

 motion, and several days elapsed before the regular 

 ebb and flow of the sea were resumed. 



Such were among the phenomena presented in the 

 region where the earthquake itself was felt. It will 

 be seen at once that within this region, or rather 

 along that portion of the sea-coast which falls within 

 the central region of disturbance, the true character of 

 the sea-wave generated by the earthquake could not 

 be recognized. If a rock fall from a lofty cliff into a 

 comparatively shallow sea, the water around the place 

 where the rock has fallen is disturbed in an irregular 

 manner. The sea seems at one place to leap up and 

 down ; elsewhere one wave seems to beat against 

 another, and the sharpest eye can detect no law in the 

 motion of the seething waters. But presently, outside 

 the scene of disturbance, a circular wave is seen to 



