A MIGHTY SEA-WAVE. 193 



The oceans and continents of our earth must be clearly 

 discernible from her nearer neighbours among the planets 

 from Venus and Mercury on the inner side of her path 

 around the sun, and from Mars (though under less favour- 

 able conditions) from the outer side. When we consider, 

 indeed, that the lands and seas of Mars can be clearly 

 discerned with telescopic aid from our earth at a distance of 

 forty millions of miles, we perceive that our earth, seen from 

 Venus at little more than half this distance, must present 

 a very interesting appearance. Enlarged, owing to greater 

 proximity, nearly fourfold, having a diameter nearly twice as 

 great as that of Mars, so that at the same distance her disc 

 would seem more than three times as large, more brightly 

 illuminated by the sun in the proportion of about five to two, 

 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 appeal 

 as far more marked and characteristic features than the seas 

 and lakes of Mars. When the Pacific Ocean, indeed, occu- 

 pies centrally the disc of the earth which at the moment is 

 turned towards any planet, nearly the whole of that disc 

 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 favourably 

 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 

 9-10, 1876, were not only of enormous range in length 

 (measured along crest or trough), but also of enormous 



