EARTHQUAKES IN GEOLOGY 



Pacific. At Samoa the height of the waves varied from 

 six to twelve feet ; in New Zealand from three to twenty 

 feet ; in Japan from five to ten feet. 



When a wave reaches shallow water it piles itself up 

 to a height, as any one knows who has watched the 

 waves coming in on the sea-shore, so that the height 

 of a wave measured on the tide-gauge of a seaport is 

 a good deal greater than that of the height of the wave 

 when it is far out on the ocean. In fact, the mid-ocean 

 height of the wave is likely to be inches while the in- 

 shore wave is measured in feet. An illustration of this 

 can be seen on the coast of Cornwall, where sometimes, 

 on quite a calm day the sea that looks so still breaks 

 on the shore in big rollers. We cannot tell exactly how 

 high an earthquake wave may be in mid-ocean, but we 

 know it cannot usually be very great, though it travels 

 at great speeds sometimes as much as five miles a 

 minute, or three hundred miles an hour. 



Thus we should not expect that ships far out at sea 

 would often notice seaquakes unless the quake took place 

 very near them. There are, however, some instances. 

 Captain Gales, of the ship Florence Nightingale, reported 

 that on January 25th, 1859, while near St. Paul's Rocks, 

 not far from the Equator, " we felt a strong shock of an 

 earthquake. It began with a rumbling sound like distant 

 thunder and lasted about forty seconds. I was quite well 

 acquainted with earthquakes, as I had experienced a good 

 many on the west coast of America, but never had I felt 

 so severe a one. Glass and dishes rattled so vigorously 

 that I was surprised to find them uninjured. A good 

 K 145 



