A MIGHTY SEA-WAVE. 179 



the ocean itself, a view which seems to find support in 

 several phenomena of recent Peruvian earthquakes. 



Although we have not full information concerning the 

 great wave which in May, 1876, swept across the Pacific, 

 and northwards and southwards along the shores of the 

 two Americas, it may be interesting to consider some of 

 the more striking features of this great disturbance of the 

 so-called peaceful ocean, and to compare them with those 

 which have characterized former disturbances of a similar 

 kind. We may thus, perhaps, find some evidence by which 

 an opinion may be formed as to the real seat of subterranean 

 activity in this region. 



At the outset it may be necessary to explain why I 

 have asserted somewhat confidently that the tides have 

 nothing whatever to do with this great oceanic wave. It 

 is of course well known to every reader that the highest 

 or spring tides occur always two or three days after new 

 moon and after full moon, the lowest (or rather the tides 

 having least range above and below the mean level) occur- 

 ing two or three days after the first and third quarters ol 

 the lunar month. The sun and moon combine, indeed, 

 to sway the ocean most strongly at full and new, while they 

 pull contrariwise at the first and third quarters ; but the 

 full effect of their combined effort is only felt a few days 

 later than when it is made, while the full effect of their 

 opposition to each other, in diminishing the range of the 

 oceanic oscillation, is also only felt after two or three 

 days. Thus in May, 1876, the tidal wave had its greatest 

 range on or about May 16, new moon occurring at half- 

 past five on the morning of May 13 ; and the tidal wave 

 had its least range on or about May 8, the moon passing 

 her third quarter a little after eleven on the morning of 

 May 4. Accordingly the disturbance which affected the 

 waters of the Pacific so mightily on May 10, occurred two 

 days after the lowest or neap tides, and five days before 

 the highest or spring tides. Manifestly that was not a time 

 when a tidal wave of exceptional height could be expected, 



