Earthly minded

Earth'-pea, n . ( Bot . ) See LATHYRUS. Earthquake, ( érth'kwāk ,) n. A shaking, heaving, trembling, or concu ive action of the solid crust of the earth. From the impo ibility of obtaining direct observations, all attempts at explaining the cause of earthquakes must be only theoretical. All theorists agree as to the connection between E. and volcanoes, and the cause of both of these phenomena is probably the same. Though the earth is now considered to be a solid ma , instead of a thin crust enclosing a molten sphere, as formerly entertained, this does not prevent the po ibility of small deposits of liquid rock occurring here and there, though more probably fluidity may arise from some relief of pre ure lowering the melting point and permitting the rocks to liquefy, perhaps with explosive force. There is much reason, however, to believe that E. and volcanic phenomena are largely due to the intrusion of water into greatly heated regions, its expansion into steam, with a consequent tremor of the earth's surface and subsequent opening of a volcanic vent. It is probable that some earthquakes are due to the sinking of sections of strata, forming what are known geologically as faults. The great Charleston earthquake (1886) has been ascribed to this cause. The history and occurrence of E. in by-gone ages is of great interest to the geologist. They seem to have occurred at all times, and to have altered the surface of the globe in all parts, forming new lakes and river-courses. and sweeping away old ones; changing hills into valleys, and raising ridges of mountains out of level plains. No part of the earth is free from them. They are, however, most prevalent in the neighborhood of volcanoes, and their frequency and violence seem to be connected race have been destroyed by these convulsions. When an E. occurs, observers state that the shock has at first a distinct vertical direction, coming from below upwards, but afterwards the direction of the motion becomes gradually more horizontal, till it ceases. This motion is evidently caused by an earth-wave, or undulation of the solid crust of the earth. These waves must move very rapidly, often not lasting at any point more than a second of time. When E. occur near the shore, the raising of the earth of course affects the sea, and immense tidal waves sweep over the land, often at a great distance from the shore, with irresistible fury. The E. of 1868 at the Sandwich Islands and along the W. coast of S. America, ranks among the most destructive on record. In Peru, from Calloa to Iquique, the whole coast was left in a complete state of ruin. Entire cities were destroyed. Immense tidal waves swept in upon the coast. It is est. that 30,000 lives were lost in S. America by this E. In October of the same year a violent shock was felt at San Francisco, Cal. May, 1877, an E. occurred on the coasts of Peru and Bolivia nearly as destructive as that of 1868. Iquique, Cobija, and several other towns, were almost destroyed, and several hundred lives lost. In 1883 an E. occurred in Java and Sumatra, destroying many towns and from 40,000 to 75,000 inhab.; in 1886 Charleston, S. C., was largely ruined by an E. , with a lo of over 40 lives and abt. $5,000,000 of property, and in 1877 serious E's occurred in S. France and Italy. E's operate to raise the land, thus opposing the destructive tendency of the aqueous agencies, which ince antly labor to wear away the continents.