Captain Dutton made a careful study of the observations collected by himself and others concerning this earthquake, and came to the conclusion that the Charleston wave traveled with unusual speed, for its mean velocity was about 17,000 feet a second. The focus of the disturbance was also ascertained. Apparently it was a double one, the two centres being about thirteen miles apart, and the line joining them running nearly the same distance to the west of Charleston. The approximate depth of the principal focus is given as twelve miles, with a possible error of less than two miles; that of the minor one as roughly eight miles.
The Charleston earthquake was felt as a tremor of more or less force through a wide area, embracing 900,000 square miles, and affecting nearly the whole country east of the Mississippi. It is said that the yield of the Pennsylvania natural gas wells decreased, and that a geyser in the Yellowstone valley burst into action after four years of rest. The movement of the earth-wave was in general north and south, deflected to east and west, and the snake-like fashion in which rails on the railroad were bent indicated both a vertical and a lateral force.
This earthquake has been attributed to various causes, but geological experts think that it was due to a slip in the crust along the Appalachian Mountain chain. There is a line of weakness along the eastern slope of this chain, characterized by fissures and faults, and it was thought that a strain had been gradually brought to bear upon this through the removal of earth from the land by rains and rivers and its deposition in thick strata on the sea-bottom. It is supposed that this variation in weight in time caused a yielding of the strata and a slip seaward of the great coastal plain. Professor Mendenhall, however, thinks it was due to a readjustment of the earth’s crust to its gradually sinking nucleus.
CHAPTER XVIII.
The Volcano and the Earthquake, Earth’s Demons of Destruction.
To most of us, dwellers upon the face of the earth, this terrestrial sphere is quite a comfortable place of residence. The forces of Nature everywhere and at all times surround us, forces capable, if loosened from their bonds, of bringing death and destruction to man and the work of his hands. But usually they are mild and beneficent in their action, not agents of destruction and lords of elemental misrule. The air, without whose presence we could not survive a minute, is usually a pleasant companion, now resting about us in soft calm, now passing by in mild breezes. The alternation of summer and winter is to us generally an agreeable relief from the monotony of a uniform climate. The variation from sunlight to cloud, from dry weather to rainfall, is equally viewed as a pleasant escape from the weariness of too great fixity of natural conditions. The change from day to night, from hours of activity to hours of slumber, are other agreeable variations in the events of our daily life. In short, a great pendulum seems to be swinging above us, held in Nature’s kindly hand, and adapting its movements to our best good and highest enjoyment.
But has Nature,—if we are justified in personifying the laws and forces of the universe,—has mother Nature really our pleasure and benefit in mind, or does she merely suffer us to enjoy life like so many summer insects, until she is in the mood to sweep us like leaves from her path? It must seem the latter to many of the inhabitants of the earth, especially to the dwellers in certain ill-conditioned regions. For all the beneficent powers above named may at a moment’s notice change to destructive ones.
THE WIND IS A DEMON IN CHAINS
The wind, for instance, is a demon in chains. At times it breaks its fetters and rushes on in mad fury, rending and destroying, and sweeping such trifles as cities and those who dwell therein to common ruin. Sunshine and rain are subject to like wild caprices. The sun may pour down burning rays for weeks and months together, scorching the fertile fields, drying up the life-giving streams, bringing famine and misery to lands of plenty and comfort, almost making the blood to boil in our veins. Its antithesis, the rainstorm, is at times a still more terrible visitant. From the dense clouds pour frightful floods, rushing down the lofty hills, sweeping over fertile plains, overflowing broad river valleys, and, wherever they go, leaving terror and death in their path. We may say the same of the alternation of the seasons. Summer, while looked forward to with joyous anticipation, may bring us only suffering by its too ardent grasp; and winter, often welcomed with like pleasurable anticipations, may prove a period of terror from cold and destitution.