GEOLOGY. 297 



and January. The earth passes its perihelion about the last day of December. 

 His theory is, that an increasing condensation of the matter of the globe, and 

 its contraction as it approaches the sun, augments necessarily the tension of 

 the fluid mass embraced within its crystalline or consolidated crust. A repuls- 

 ive action necessarily ensues between the molecules of the molten mass, and 

 the mobility of this mass so acts, here and there, as to rupture the crust and 

 allow the melted earth to insinuate itself between strata, or vertically through 

 the entire crust, in the form of dykes, or to be forced out of volcanic openings. 



NOTICE OF EARTHQUAKE WAVES ON THE PACIFIC COAST OF 



THE UNITED STATES. 



The following communication was presented to the American Association, 

 Providence, by Professor A. D. Bache. 



On the 23d of December, 1854, at 9 A.M., an earthquake occurred at 

 Simoda, on the island of Xiphon, Japan. The harbor was first emptied of 

 water, then came in an enormous wave which again receded. (It appeared 

 that the whole character of the harbor of Simoda, previously surveyed by the 

 Powhatan, had been changed by the earthquake.) A report from the Bonin 

 Islands is not sufficiently exact to use for our main purpose, but points to 

 Simoda as the center of disturbance. (Simoda, according to the Rev. Mr. 

 Jones, is volcanic ; Bonin appears not to be.) Now the Coast Survey has 

 three self-acting tide-gauges at Astoria, on Columbia River, San Francisco 

 and San Diego. They record the rise of the tide on a cylinder turned by 

 a clock. The apparatus is protected more or less from the oscillations that 

 wind waves would cause, which only cause a trembling of the index or 

 stylus. The gauge at Astoria was but slightly affected by the earthquake 

 Wave, owing to the bar on the river and the distance it had to ascend. 

 At San Francisco, 4,800 miles from Simoda, the wave arrived 12 hours 

 16 minutes after the beginning of the earthquake. A series of seven waves, 

 each about half an hour in duration, or 35 minutes, each series succes- 

 sively smaller, and separated by a quiet time of an hour from the preceding, 

 was recorded at San Francisco. At San Diego the wave had traversed 

 5,200 miles in 12 hours 38 minutes, and produced likewise a series of seven 

 waves,, each nearly corresponding to those at San Francisco, but the second 

 series stronger than the first and third. In height they were less, the highest 

 at San Francisco being *7 of a foot, at San Diego '6. The waves at San Diego 

 could not have come from San Francisco, as they would have arrived much 

 later. These waves would have escaped detection by ordinary observation, 

 being 39 feet in height only on the average at San Diego, and 44 feet at San 

 Francisco. Three series are distinctly traceable at San Francisco, the highest 

 wave being 65 feet hi height on a tide falling two feet. The time of oscilla- 

 tion there was 33 minutes, and at San Diego 30 minutes. The violence of 

 the earthquake was so great at Simoda, in Japan, as to raise a wave some 30 

 feet high, there, and 15 feet at Peel's Island, about 500 miles to the southward. 

 The velocity with which a wave travels depends on the depth of the ocean. 

 The second and third series were but repetitions of the first wave that had 



13* 



