202 LIGHT SCIENCE FOR LEISURE HOURS. 



must have been so situated that either the wave was 

 diverted from Callao, or more probably two waves 

 reached Callao from different sources and at different 

 times, so that the two undulations partly counteracted 

 each other. Certain it is that although the water 

 retreated strangely from the coast near Callao, inso- 

 much that a wide tract of the sea-bottom was un- 

 covered, there was no inrushing wave comparable with 

 those described above. The sea afterwards rose and 

 fell in an irregular manner, a circumstance confirming 

 the supposition that the disturbance was caused by two 

 distinct oscillations. Six hours after the occurrence of 

 the earth-shock, the double oscillations seem for awhile 

 to have worked themselves into unison, for at 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 appear- 

 ance within half an hour of the earth-throes. There 

 is little reason to doubt that if the separate oscillations 

 had reinforced 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 14, 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 



