Hector.—On Earthquakes and Wave Phenomena. 43 
giving strong support to the view advanced in the lecture before the New 
Zealand Institute, that the primary cause of 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, F.G.S., to the Daily Southern Cross 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 Francisco, 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 wave 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 Pacifie 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.” *F. W, Horton.” 
