246 DEVASTATIONS OCCASIONED BY T0EEENT9. 



landslip which overwhelmed and covered to the depth of seventy feet the 

 town of Plurs, in the valley of the Maira, on the night of the 4th of Sep- 

 tember 1618, sparing not a soul of a population of 2,430 inhabitants, is one 

 of the most memorable of these catastrophes, and the fall of the Rossberg, 

 or Eufiberg, which destroyed the little town of Goldau in Switzerland, and 

 450 of its people, on the 2nd of September 1860, is almost equally cele- 

 brated. In 1771, according to Wessely, the mountain-peak Piz, near 

 Alleghe in the province of Belluno, slipped into the bed of the Cordevole, a 

 tributary of the Piave, destroying in its fall three hundred and sixty lives. 

 The rubbish filled the valley for a distance of nearly two miles, and, by 

 damming up the waters of the Cordevole, formed a lake about three miles 

 long, and a hundred and fifty feet deep, which still subsists, though 

 reduced to half its original length by the wearing down of its outlet. 



"The important provincial town of Veleia, near Piacenza, where many 

 interesting antiquities have been discovered within a few years, was buried 

 by a vast landslip, probably about the time of Probus, but no historical 

 record of the event has survived to us. 



" On the 14th of February 1855, the hill of Belmonte, a little below the 

 parish of San Stefano in Tuscany, slid into the valley of the Tiber, which 

 consequently flooded the village to the depth of fifty feet, and was finally 

 drained ofi' by a tunnel. The mass of debris is stated to have been about 

 3,500 feet long, 1,000 wide, and not less than 600 high. 



" Occurrences of this sort have been so numerous in the Alps and Apen- 

 nines, that almost every Italian mountain commune has its tradition, its 

 record, or its still visible traces of a great landslip within its own limits. 

 The old chroniclers contain frequent notices of such calamities, and Giovanni 

 Villani even records the destruction of fifty houses, and the loss of many 

 lives, by a slide of what seems to have been a spur of the hill of San 

 Giorgio in the city of Florence, in the year 1284. 



" Such displacements of earth and rocky strata rise to the magnitude of 

 geological convulsions, but they are of so rare occurrence in countries 

 still covered by the primitive forests, so common where the mountains have 

 been stripped of their native covering, and, in many cases, so easily expli- 

 cable by the drenching of inoohesive earth from rain, or the free admission 

 of water between the strata of rocks — both of which a coating of vegetation 

 would have prevented — that we are justified in ascribing them for the most 

 part to the same cause as that to which the destructive effects of mountain 

 torrents are chiefly due — the felling of the woods. 



" In nearly every case of this sort, the circumstances of which are known 

 — except the rare instances attributable to earthquakes — the immediate 

 cause of the slip has been the imbibition of water in large quantities by 

 bare earth, or its introduction between or beneath solid strata. If water 

 insinuates itself between the strata, it creates a sliding surface, or it may, 

 by its expansion in freezing, separate beds of rock, which had been nearly 

 continuous before, widely enough to allow the gravitation of the super- 

 incumbent mass to overcome the resistance afforded by inequalities of face 

 and by friction ; if it find its way beneath hard earth or rock reposing on 

 clay or other bedding of similar properties, it converts the supporting 

 layer into a semi-fluid mud, which opposes no obstacle to the sliding of the 

 strata above. 



" The upper part of the mountain which buried Goldau was composed of 

 a hard but brittle conglomerate, called naydfiue, resting on an unctuous 



