Читать книгу A Study of Recent Earthquakes - Charles Davison - Страница 37

The interval between July 18th, 1881, when the last shock of that year was felt, and July 28th, 1883, was one of almost complete quiescence. Early in March 1882, a few slight shocks were noticed at Casamicciola. On July 24th, 1883, a watch hanging from a nail in a wall was seen to swing at 6 A.M. and 9 A.M., and, on the same morning, at about 8.30, a slight shock, accompanied by a rumbling sound, was felt at Casamicciola. Again, on the 28th, about a quarter of an hour before the great shock, one observer at Casamicciola states that an underground noise was heard, and that some persons in consequence left their houses.

Many assertions have been made with regard to variations witnessed a day or two before the shock in the hot springs, such as an increase of flow or temperature and changes in their volume and purity. Fumaroles are alleged to have burst out with violence, and even flames to have been seen. The statements, though widely quoted, can hardly be said to rest on satisfactory evidence. On the other hand, Dr. Johnston-Lavis arrived in the island within twenty-four hours after the shock, and, before another day had elapsed, he had examined most of the places where the phenomena were said to have occurred, but could find no remarkable change nor any signs of such having taken place. It is also known, as he remarks, that the temperature of the Ischian springs and fumaroles sometimes varies considerably without any earthquake following, that of the water of Gurgitello occasionally changing by as much as 30° or 40°. We may therefore, I think, conclude that, except for one or two shocks and underground noises too slight to cause general alarm, there were no decisive heralds of the great earthquake.