Page:Popular Science Monthly Volume 77.djvu/164

158 before it was generally known." Another woman, in poor health, ascribed the peculiar feeling that she experienced to an attack of heart disease, and sank frightened in bed. Experiences of this kind have been noted in other earthquakes and appear to be due to a morbidly excitable condition of the ill-defined and unspecialized sense of general well being. Some people perceived the earthquake chiefly through the sense of touch, as when a man, seated in a chair and resting his legs on a railing, "felt his legs shake," or as when a chief of police, also seated, felt that his chair shook. In several other cases the earthquake was likewise merely "felt." No doubt the sense of touch entered as an important element in a far greater number of instances when mention is made that something shook, trembled, quivered or rocked, or when there was a jar or a tremor. The sense of equilibrium or of poise was evidently involved in the case of a man who felt "dizzy," and in the case of people who "wabbled on the streets," in cases where occupants of houses noted a "heaving," "rocking" or a "swaying" motion, and when people "were thrown down," or "nearly tumbled over," or "found difficulty in keeping on their feet."

The reports mention only five instances of sounds accompanying the earthquake. Such sounds are general in the mesoseismal area in all severe earthquakes in all parts of the world, except in Japan, and one noted seismologist believes that their absence in that country is due to a racial inability among the Japanese to hear sounds of very low pitch. The general absence of sounds in the Illinois earthquake is readily accounted for by its comparative weakness. It was faintly audible only in three epicentral tracts. Some parties claim to have heard a distinct rumbling before the shock in Dubuque. In Waukegan one man described the quake as a rush of wind, and said that he had heard it. This swishing noise is one of the many known characteristic forms of earthquake sounds. In Springfield, 111., a faint rumbling was heard, and a janitor in one of the school buildings in Peoria made a similar observation. One man heard a sound like the "bumping of a locked door." This is another variation of earthquake noises, which, when more powerful, resemble volleys of musketry and artillery, and which, like the other noises, originate under the ground. Many observations involve sounds which are, as it were, proxies of the quake, induced by secondary events, such as the rattling of windows and dishes, the crash of falling brick and the like. The student of earthquakes depends, as we have seen, on such noises for much of his information on the progress of the earth waves in the peripheral region of the disturbed area.

The sense that gives us the most reliable information on earthquakes, as on most other physical phenomena, is the sense of sight. Visible earth waves are, however, rarely seen except in severe disturbances. It is uncertain whether they appeared anywhere in this case.