Hectoe. — On ILarniqiiaJces and Wave Phenomena. 43 



giving strong support to the yiew advanced in tlio lecture before the New 

 Zealand Institute, that the primary cause o£ earthquakes is an influence ex- 

 ternal to our planet, so that earthquakes are to be considered as the remote 

 cause rather than the effect of volcanic phenomena. 



The following remarks on the earthquake wave were communicated by- 

 Captain Hutton, E.G-.S., to the Daily Southern Gross newspaper: — 



" The earthquake wave that crossed the Pacific Ocean in August, from 

 Peru to Australia, is, I believe, the largest wave of its class yet recorded ; 

 the only ones that can at all compare with it being the one caused by the 

 earthquake at Lisbon in 1755, which was propagated across the Atlantic to 

 the West Indies, a distance of 3,500 miles ; and the more recent one of 

 December, 1854, caused by the great earthquake in Japan, and which 

 traversed the North Pacific to San Prancisco, a distance of 4,500 miles. 



" The wave that lately visited our shores appears to have originated 

 somewhere about lat. 20° S., and long. 70° "W., at 5 p.m. on the 13th of 

 August, according to the reckoning at the place, or at 9 a.m., 14th of 

 August, according to our time. The first v^^ave reached New Zealand at 

 4 a.m. on the 15th of August, having therefore travelled about 6,700 miles in 

 nineteen hours, or at the rate of 5*87 miles a minute. The three waves 

 reached us at three-hour intervals, and must, therefore, each have been about 

 1,000 miles in breadth. The velocity at which waves travel over the ocean 

 depends upon the depth of the water, and varies as the square root of the 

 depth, so that the deeper the water the quicker the wave will travel. The 

 wave raised by the earthquake at Lisbon travelled to the Barbadoes at the 

 rate of 7'8 miles a minute, while it went to London at very little more than 

 two miles a minute. Professor Airy has shown that a fixed relation exists 

 between the breadth of a wave, its velocity of progress, and the depth of 

 the water on which it travels. The earthquake wave of December, 1854, was 

 217 miles in breadth, and travelled at the average rate of 6'1 miles per 

 minute, from which Professor Bache concluded that the mean depth of the 

 North Pacific was 2,365 fathoms, or 14,190 feet. In the same way, by the 

 progress of the tidal wave, the Atlantic from 50° N. to 50° S. has been 

 calculated to have a mean depth of 22,157 feet. 



" Applying the same theory to the late wave, we find that the South 

 Pacific has an average depth of only 8,721 feet, or not quite 1,454 fathoms ; 

 or, in other words, the South Pacific is much more shallow than either the 

 North Pacific or the Atlantic. This fact, if it should hereafter be established, 

 has a very important bearing both on geology and the geographical distribu- 

 tion of plants and animals, which, however, it would be quite out of place 

 to enlarge upon here. 



" Auckland, 6th October, 1868." " P. W. Hutton," 



