Page:The New International Encyclopædia 1st ed. v. 06.djvu/678

EABTH LODGE. 590 EARTHQUAKE. ing type. Earth lodges abound also in the mid- dle latitudes of South America, as well as in many parts of Asia and l^urope. Tacitus {(ler- maiiia, xvi.) spoak.^ ot eartli lodges among the Germans. fSuhtcrrancan galleries e.xist in those parts of Scotland. Ireland, and England where tjaelic speech is prevalent. Hence these prehis- toric remains are thought to have been of Celtic origin. They consist of a principal chamber, often with rooms on the sides and reaching the depth of fifty feet or more. The walls are said to be of stones laid up dry and the roofs of slabs are often not more than a foot beneath the surface. Relies of Roman origin are found in some, and it cannot be jiositively allirmcd who built them. Whole cities in Russia are under the ground. In .Japan, especially in the north, and in Korea, earth lodges were formerly in use. One of the most interesting phases of this type of habita- tion culminates in the dome-shaped snow hut of those Eskimo who lie away from any timljcr- supply. Across the northern portion of the earth the tribes live under sod a part of the year. These subterranean abodes arc built of wood and covcri'd with earth. In Arctic America, wlicrc driftwood abounds, the Eskimo make a strong framework of logs over which earth is heaped. The chambered tomb or dolmen is mere- ly the earth lodge for the dead; the snow dome, prototype and forerunner of the most imposing architectural feature, is the climax of the earth lodge for the living. EARTHLY PARADISE, The. A series of narrative piicm^ by William Jlorris, modeled on Chaucer's Canterbury Talcs and publi.shed in 1808-71. The separate poems are mythological stories told by Norwegian voyagers in search of an earthly paradise. EARTHNTTT. A popular name for the tu- bers of icrtiiiii uiiibcllifcnms ])laiits, i)articuliirly Carum bulboiastanuni and Conopodium llexuo- sum, which are common in most parts of Europe. Names of the same signification are given to them in a number of European languages, i'ig- nut is another connnon English name, because pigs are very fond of them. They are also called earth-chestnut, from their resemblance in taste and qualities to chestnuts. They are wholesome and nutritious, and form an article of trade in Sweden, and have sometimes been recommended as worthy of more attention than they liavc yet received. Carum feruhrfolium likewise affords tubers, which are used as food in Greece. The somewhat similar tubers of other umbelliferous plants, as (Enanthe pimpinelloides and Charo- phyllum tuberosum, are sometimc^j also used for food. The name earthnut is sometimes extended to other small ttiberous roots of similar quality, although i)riiduced by plants wi<lcly remote in the botanical system, as .pies tuberosa and Lathyrus tuberosus. Cyperus rotundus. Arachia hypoga'a. etc. EARTHQUAKE. A term applied to any tremor or shaking of the solid crust of the earth due to natural subterranean concussion. Earthqvmkes vary in intensity from tremors so slight as to be observed only by the most deli- cate instruments, to violent destructive shocks. 'hile the more violent shocks are not of fre- quenl occurrence, except in certain localities, slight tremors are shown, by the delicate instru- ments now used, to be of surprising frequency. The earth is indeed anything but a terra firtna. The succession of plu-nomcna recorded in nota- ble earllu|uakcs is lirst a trembling, next a severe shock or several sliocks in quick succes- sion, and then a trembling, gradually, but rapid- ly, becoming insensible. Noises of sundry kinds usually precede, accompany, or succeed the earthquake. These have been likened to the howling of a storm, the growling of thunder, the clanking of iron chains, the rumbling of heavy wagons along the road, the shattering and crash- ing of enormous masses of glass, etc. Such noises are conducted through the ground, through the sea. or through the air. Through the ground they travel for the greatest dis- tances ; cases being known where they have traveled nearly 200 miles. An earthquake begins at some point of sub- terranean shock, called the centrum or focus, and travels in waves, with gradually diminish- ing energy, in every direction from this point. It has been determined that these foci are com- n.onl.y at dcjHlis of 8 or 10 miles below the sur- face, and rarely as dee|) as 25 or 30 miles. This determination is based on the fact that at the epiccntum over the locus the shock is felt as a vertical movement, while away from this point the shock comes to the surface obliquel.v. The angle at which the shock emerges from the ground is determined by the results of the shocks on walls and buildings. Aith a. number of such observations at various situations, the point of origin of the earthquake may be located. The earthquake shock is transmitted through rock in two waves: one, the compression wave, vi- brating parallel to the direction of transmission: and the other, the distortion wave, vibrating normal to the direction of transmission. The former has the greater velocity. The waves are of small amplitude: the ground moves upward or downward, or obliquel.v. or horizontally, usually through a very small fraction of an incli, and seldom through a space of more than two or tlirec inches. The destructiveness of the earth- quake is dependent more on velocity than on amplitude of the wave-movement. With great velocit.y a movement of a snuill fraction of an inch is sulHcient to shatter brick buildings. As to the velocity of earthquake waves. Professor Milne, one of the leading investigators of earth- quakes, concludes that "difVerent earthquakes, altlKMigh they may travel across the same coun- tr.'. have verv variable velocities, varying be- tween several Inindrcds and several thous;inds of feet per second : that the same earthquake travels more quickly across districts near to its origin than it does across districts which are far re- moved; and that the greater the intensity of the shock, the greater is the velocity." The num- ber of shocks in an earthquake and the length of time-interval between them vary between wide limits, The cities of Caracas and Lisbon were destroyed in a few minutes, while the Calabrian earthquake, beginning in 178:!. continued for four years. The structure and nature of the rocks through which the earthquake shock is transmitted have an effect on the transmission of earthquake waves, causing numerous deflections and delays. It has been noted that localized areas are some- times not sensibly affected, while surrounding areas feel the movement. Also, shocks which are not felt at the surface have been felt in