INTERIOR LAND CHANGES. 415 



It was calculated by the writer of the memoir, that the flood for the first four miles 

 swept along at the rate of twenty miles an hour, nearly the speed of a locomotive, and 

 furnished about 300,000 cubic feet of water every second an efflux five times greater 

 than that of the Rhine at Basle. In six hours and a half, it arrived at the Lake of Geneva, 

 having passed into the Rhone, a distance of forty-five miles. Among the physical 

 alterations effected by this debacle, there was the deposition of a stratum of alluvial matter 

 over the whole of the lower part of the Val de Bagnes. This was several feet in thickness, 

 and Avas so distributed that roads were obliged to be cut through it in some places, as 

 when the snows have blocked up our thoroughfares. There was the transportation of an 

 immense number of isolated masses of rock to a considerable distance, some of which must 

 have been many tons in weight. One of these, fairly projected out of the gorge of the 

 valley into the plain, measured twenty-seven paces round, twelve feet in height, and 

 twelve feet across in one direction, and even larger masses bore indubitable marks of 

 having been in motion. For some time the course of the Dranse fluctuated, and when at 

 last it settled down into a channel, it was one widely diffei-ent from that which had before 

 been followed. Captain Hall visited Martigny a few weeks after this visitation, and 

 found every land-mark obliterated under one uniform mass of detritus, which had levelled 

 all distinctions in a '' sweeping and democratic confusion." 



The removal of loose materials, the tearing up of fragments of rock, and their 

 transportation to a distant site, transpire under the action of those temporary torrents 

 which are produced by heavy rains in mountainous districts. The pen of Captain Hall 

 has sketched in a lively manner a specimen of their vigour as exhibited in the high lands 

 behind the town of Funchal in the island of Madeira. The whole of the upper part of 

 the mountain is split into crevices, in some instances deep enough to be called ravines, or 

 in the larger cases even valleys, which have been cut by the rapid rush of the descending 

 currents. Many of these crevices run into one another, so that when the rain falls in 

 any quantity, the whole series are set in operation at once, like so many gigantic sluices, 

 to conduct the water into the main channels which convey it into the sea. In less 

 precipitous countries, the minor streams take some time to collect their waters ; but at 

 Madeira, where the hills are steep, the whole is done almost at a blow, and with an 

 impetuosity that seems formidable to eyes unaccustomed to it. A few hours after a heavy 

 rain has commenced, the torrents are all at work. Behind Funchal, the side of the 

 mountain is indented by a valley of considerable dimensions, into which a number of 

 ravines run, and bring down the discharges of rain from the highest ridges of the island. 

 This is frequently the bed of a torrent, filled to the depth of twenty feet, partly with 

 water and partly with stones, many of them of great dimensions, and moving together 

 with a noise like continuous loud thunder. The angle which the bed makes with the 

 horizon is sufficient to cover the surface of the stream with waves more tumultuous than 

 those of the Canadian rapids, bearing along rocks with the utmost velocity, which the 

 St. Lawrence would not cause to budge an inch. Sometimes huge blocks are jerked half 

 out of the stream by the violence with which they are dashed against one another, or 

 against some opposing angle of the channel, the bottom and sides of which, every time 

 the torrent is in action, undergo an amount of wear and tear which effects great changes 

 in the course of years. The writer before referred to describes this torrent, when in full 

 play, as the grandest thing possible, requiring an effort of considerable resolution to 

 advance to its brink, and far surpassing the surfs, breakers, and rapids, in any part of the 

 world, in the impression of irresistible power it makes upon the senses. The roar is such 

 that hardly any elevation of the voice can make two persons audible to one another, 

 though standing side by side, while the ground trembles in a manner indicating the 

 enormous weight passing over the surface. Soon after the rain ceases, this immense 



