EARTHQUAKES OF 1881. bll 



two or three weeks ago, and the recent shakings of the ground felt in New Hamp- 

 shire and other places in the country, indicate that the disturbing forces are yet 

 active in widely separated portions of the globe. In fact, the history of earth- 

 quakes show that when once a wide circle of commotion has been established, 

 several years must pass before the internal forces exhaust themselves. The 

 earthquakes that began in 181 1 lasted until 1813. They were very frequent 

 in the Mississippi and Ohio Valleys, and north of Cincinnati the shocks occurred 

 for months at the rate of twenty or more a day. The farmers became so accus- 

 tomed to them that they hardly stopped to lean on their hoes while an earthquake 

 was shaking the corn-fields. This recalls Humboldt's account of his experience 

 in South America in the beginning of the present century. He traversed regions 

 in which earthquakes were so common that the inhabitants no more thought of 

 taking account of their number than Europeans think of counting the showers of 

 rain. 



One of the most interesting things about earthquakes is their tendency to 

 group themselves into periods. The present earthquake period began three or 

 four years ago, and some supposed that it had reached its culmination last fall 

 when Agram was overthrown. But the shocks increased in force until the terri- 

 ble disaster at Casamicciola occurred in March last. This, in turn, was supposed 

 to be the climax of a series of violent terrestrial commotions that, beginning in 

 Peru in 1879, within a few months circled the earth. About a month later, how- 

 ever, came the great Chios earthquake, one of the most destructive on record; 

 and this so far remains the crowning disaster of the present earthquake cycle. 

 But the return of the shocks at Agram, and the indications of continued commo- 

 tion in various parts of the earth show that another calamity of the same kind 

 may happen any day. 



Ordinarily, earthquakes are confined to countries in the neighborhood of 

 volcanoes. But in periods of unusual activity, like the present, they sometimes 

 occur in places where -^they are least expected. In the valleys of the Hudson, 

 the St. Lawrence, the Ohio and Mississippi, shocks have been felt this year. Ex- 

 actly what relation exists between volcanoes and earthquakes men of science are 

 trying to find out. It seems to be settled that they both result from the same 

 general cause. Whether the whole interior of the earth is a molten mass (a 

 theory that has fallen out of favor of late), whether it contains reservoirs or 

 pockets of molten rock under volcanic districts, or whether the phenomena of 

 volcanoes or earthquakes are the result of some force not yet understood, makes 

 little difference except so far as knowledge of the facts may enable science to 

 master the laws that govern terrestrial disturbances. The significant fact, how- 

 ever it may be explained by theory or observation, is that the ball upon which 

 we live, instead of being a dead, inert mass, a type of stability, is heaving under 

 the strain of interior forces, which, though too insignificant, so far as human ob- 

 servation goes, to produce outbursts comparable to those in the sun or some of 

 the larger planets, yet suffice at times to overthrow great cities, to burst moun- 

 tains asunder, and to destroy at one stroke many thousands of human beings. 



