The Elements of Geology

is formed or extended, or slip from time to time along a growing fault, produces a j

the main shock passed beneath the city. Houses swayed to and fro, and their heaving floors overturned furniture and threw persons off their feet as, dizzy and nauseated, they rushed to the doors for safety. In sixty seconds a number of houses were completely wrecked, fourteen thousand chimneys

of greatest disturbance, which lay above the focus, a few miles northwest of the city, the surface shock traveled outward in every direction, with decreasing effects, at the

e is transmitted through the elastic medium of the air. Each earth particle vibrates with exceeding swiftness, but over a very short path. The swing of a particle in

e medium. In the deep, hot, elastic rocks they speed faster than in the cold and broken rocks near the surface. Th

through the body of the earth at the rate of about three hundred and fifty miles a minute, and more slowly round its circumference,

n from the sides of mountains and hills, and cracks may be opened in the surface deposits of plains; but the transient shiver

t. In 1822 the coast of Chile was suddenly raised three or four feet, and the rise was five or six feet a mile inland. In 1835 the same

l shifting reached a maximum of twenty feet. Fences, rows of trees, and roads which crossed the fault were broken and offset. The latitude and longitude of all points over thousands of square miles were changed. On each side of the fau

agration which destroyed $500,000,000 worth of property. The destructive effects varied with the nature of the ground. Buildings on firm rock suffered least, while those on deep alluvium were severely shaken by the undulations, like water waves, into which the loose material was thrown. Well-braced steel structures, even of the largest size, were earthquake proof, and buildings of ot

r New Madrid, Mo. Much of the area was converted into swamps and some into shallow lakes, while a region twenty miles in diameter was bulged up athwart the channel of th

e been instances where the displacement has been sufficient to set the entire Pacific Ocean pulsating for many hours. In mid ocean the wave thus produced has a height of only a few feet, while it may be two hundred miles in

ibuted over the globe. As we might infer from what we know as to their causes, earthquakes are most frequent in regions now undergoing deformation. Such are young rising mount

The Highlands of Scotland are crossed by a deep and singularly straight depression called the Great Glen, which has been excavated along a very ancient line of disl

ccurred in the three years ending with 1901. They originate, for the most part, well down on the eastern flank of the earth fold w

ns and even the collapse of the roofs of caves. The earthquakes which attend the eruption of volcanoes are local, even in the case of the most violent volcanic p

p. Volcanic earthquakes are particularly shallow, and probably no earthquakes known have started at a greater depth than fifteen

f an earthquake to be greater in

were found driven into the ground, and chimneys cru

ppled over on the roof. Should you infer that the

tures hanging on the east and the west walls of a room? h

illars, or "monuments," are common. What inference could you draw as to