A MIGHTY SEA- WAVE. 



177 



she would shine with a lustre exceeding that of 

 Mars when in full brightness in the midnight sky 

 about thirty times, and all her features would, of 

 course, be seen with correspondingly-increased 

 distinctness. Moreover, the oceans of our earth 

 are so much larger in relative extent than those 

 of Mars, covering nearly three-fourths instead of 

 barely one-half of the surface of the world they 

 belong to, that they would appear as far more 

 marked and characteristic features than the seas 

 and lakes of Mars. When the Pacific Ocean, in- 

 deed, occupies centrally the disk of the earth 

 which at the moment is turned toward any planet, 

 nearly the whole of that disk must appear to be 

 covered by the ocean. Under such circumstances 

 the passage of a wide-spreading series of waves 

 over the Pacific, at the rate of about 500 miles 

 an hour, is a phenomenon which could scarcely 

 fail to be discernible from Venus or Mercury, if 

 either planet chanced to be favorably placed for 

 the observation of the earth — always supposing 

 there were observers in Mercury or Venus, and 

 that these observers were provided with powerful 

 telescopes. • 



It must be remembered that the waves which 

 spread over the Pacific on August 13-14, 1868, 

 and again on May 9th-10th last, were not only 

 of enormous range in length (measured along 

 crest or trough), but also of enormous 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 traveling 6,000 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 in- 

 stance, 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 from trough to 

 crest is but half the breadth of the wave), or in 

 less 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 up- 

 ward and downward 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 subjected to such tossing 

 as this would inevitably be swamped. On even 

 the largest ships the effect of such motion would 

 48 



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 dis- 

 tinctly 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 gieat 

 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 pas- 

 sage of the great sea-wave was no more noticed 

 than is the passage of the tidal wave itself. 

 "Among the hnndreds of ships which were sail- 

 ing upon the Pacific when its length and breadth 

 were traversed by the great sea-wave, there was 

 not one in which any unusual motion was per- 

 ceived." The inference is clear that the slope 

 of the advancing and following faces of the great 

 wave was very much less than in the case above 

 imagined ; in other words, that the breadth of 

 the wave greatly exceeded one mile — amounting, 

 in fact, to many miles. 



Where the interval between the passage of 

 successive wave-crests was noted, we can tell the 

 actual breadth of the wave. Thus, at the Samo- 

 an Isles, in 1868, the crests succeeded each other 

 at intervals of sixteen minutes, corresponding to 

 eight minutes between crest and trough. As we 

 have seen that, if the waves were one mile in 

 breadth, the corresponding interval would be only 

 four seconds, or only 120th part of eight minutes, 

 it would follow that the breadth of the great 

 wave, where it reached the Samoan Isles in 1868, 

 was about 120 miles. 



Now, a wave extending right athwart the Pa- 

 cific Ocean, and having a cross-breadth of more 

 than 100 miles, would be discernible as a marked 

 feature of the disk of our earth, seen, under the 

 conditions described above, either from Mercury 

 or Venus. It is true that the slope of the wave's 

 advancing and following surfaces would be but 

 slight, yet the difference of illumination under 

 the sun's rays would be recognizable. Then, also, 

 it is to be remembered that there was not merely 

 a single wave, but a succession of many waves. 

 These traveled also with enormous velocity ; and 

 though at the distance of even the nearest planet 

 the apparent motion of the great wave, swift 

 though it was in reality, would be so far reduced 



