Ralph S. Tarr

“ Material is constantly being eroded from some and piled upon others. The time finally comes when they snap or spring, and, striking the rocks above, send out an earthquake shock. Quarrymen frequently feel a slight shock, and immediately after hear a report, showing that the strain in some rock has been relieved. ”

“ The kind of rock on which one is standing, loose gravels greatly diminishing: the force of the shock. The destructiveness of earthquakes depends rather upon the suddenness of application than the amount of motion. In that at Rio Bomba, it is reported for a fact that a man was hurled across a stream a distance of one hundred feet, and landed on an elevation fifty feet higher than his original position. It is an undoubted fact that objects are frequently thrown great distances. ”

“ The earth is constantly quivering, some point on the surface being the seat of a slight quake nearly every moment of the day. By far the larger number of these are of little intensity, being felt only by delicate instruments, and the majority of cases come from volcanic regions. ”

“ So few facts are known, that we can neither draw deductions nor even determine the causes. It is reported, however, that earth-quakes more commonly occur at night, and that they are more abundant in winter than in summer. ”

“ AT the present time the earth seems to be in a state of great seismological action. Different parts of the world have recently been disturbed by earthquakes which have caused wide-spread destruction. Those in Spain, which began December 24th, and have lasted, with slight interruption, down to the time of writing, have been among the most destructive of recent earthquakes. Over two thousand people have been killed, many more wounded, and thousands of houses destroyed. ”

“ It can be conceived, then, that such rocks must be in a constant state of strain ready to relieve themselves at any favorable moment. Let us suppose that we have a long board held down on each end by a bank of earth. ”

“ Another theory is, that earthquakes are due to volcanic action. The passage of the immense quantities of gas which escape from volcanoes must necessarily cause shock after shock. This gas, under pressure of thousands of pounds, is contained in a subterranean boiler, from which it is continually trying to escape. ”

“ In some cases the cavern theory may apply, but these are rare, and can usually be determined, so that in any region not volcanic the third theory is the most probable. This accounts for the fact that earthquakes are much more frequent and violent in mountain-regions of recent origin. The Appalachian, which are the oldest mountains in America, are, therefore, very free from earthquakes, because the rocks have, as a rule, long since relieved themselves ”