DISTUKBANCES IN THE OCEAN. 165 



ticular area, we must bear in mind that it lies in the line 

 of Iceland, the west coast of Scotland, the Azores, Canaries, 

 Cape de Verd Islands, St. Helena, and other places, all of 

 which, if not at present in volcanic activity, shew evidence 

 of having been so within recent times. The connection 

 between volcanic action and earthquakes will be again 

 referred to. 



Sea waves. — Although in the above-mentioned in- 

 stances sea waves have not been noticed, it is by no means 

 uncommon to find that destructive earthquakes have been 

 accompanied by waves of an enormous size, which, if the 

 earthquake has originated beneath the sea, have, subse- 

 quently to the shaking, rolled in upon the land, to create 

 more devastation than the actual earthquake. It may, 

 however, be mentioned that a few exceptional cases exist 

 when it is said that the sea wave has preceded the earth- 

 quake, as, for example, at Smyrna, on September 8, 1852. 



Again, at the earthquake in St. Thomas, in 1868, it is 

 said that the water receded shortly before the first shock. 

 When it returned, after the second shock, it was sufficient 

 to throw the U.S. ship ' Monagahela ' high and dry.^ 



Another American ship, the ' Wateree,' was also lost in 

 1868 by being swept a quarter of a mile inland by the sea 

 wave which inundated Arequippa. 



Much of the great destruction which occurred at the 

 time of the great Lisbon earthquake was due to a series of 

 great sea waves, thirty to sixty feet higher than the highest 

 tide, which swamped the town. These came in about an 

 hour after the town had been shattered by the motion of 

 the ground. 



The first motion in the waters was their withdrawal^ 

 which was sufficient to completely uncover the bar at the 

 mouth of the Tagus. At Cadiz, the first wave, which was 

 * Am. Jour. Sci. vol. xlv. p. 133. 



