194 PLEASANT WAYS IN SCIENCE. 



breadth (measured from crest to crest, or from trough to 

 trough). Were it otherwise, indeed, the progress of a wave 

 forty or fifty feet high (at starting, and thirty-five feet high 

 after travelling 6000 miles), at the rate of 500 miles per 

 hour, must have proved destructive to ships in the open 

 ocean as well as along the shore-line. Suppose, for instance, 

 the breadth of the wave from crest to crest one mile, then, in 

 passing under a ship at the rate of 500 miles per hour, the 

 wave would raise the ship from trough to crest that is, 

 through a height of forty feet in one-thousandth part of an 

 hour (for the distance front trough to crest is but half the 

 breadth of the wave), or in Itss than four seconds, lowering it 

 again in the same short interval of time, lifting and lowering it 

 at the same rate several successive times. The velocity with 

 which the ship would travel upwards and downwards would 

 be greatest when she was midway in her ascent and descent, 

 and would then be equal to about the velocity with which a 

 body strikes the ground after falling from a height of four 

 yards. It is hardly necessary to say that small vessels sub- 

 jected to such tossing as this would inevitably be swamped. 

 On even the largest ships the effect of such motion would be 

 most unpleasantly obvious. Now, as a matter of fact, the 

 passage of the great sea-wave in 1868 was not noticed at all 

 on board ships in open sea. Even within sight of the shore 

 of Peru, where the oscillation of the sea was most marked, 

 the motion was such that its effects were referred to the 

 shore. We are told that observers on the deck of a United 

 States' war steamer distinctly saw the " peaks of the mountains 

 in the chain of the Cordilleras wave to and fro like reeds in 

 a storm ; " the fact really being that the deck on which they 

 stood was swayed to and fro. This, too, was in a part of 

 the sea where the great wave had not attained its open sea 

 form, but was a rolling wave, because of the shallowness of 

 the water. In the open sea, we read that the passage of the 

 great sea-wave was no more noticed than is the passage o! 

 the tidal-wave itself. " Among the hundreds of ships which 

 were sailing upon the Pacific when its length and breadth 



