26 EisuMf OP surbll's study op 



and the same thing may be observed in all rivers, each of which has a 

 character of its own. 



Sometimes the swelling occurs gradually ; the waters rise ; clear at first, 

 they become more and more turbid, and then throwing their strength into 

 their velocity, rolling along stones which strike each other with a dull 

 sound, they end at last by overflowing their banks, and then begin the 

 ravages and additions to the deposit in the bed de ddjection. 



At other times they come suddenly, and all at once is seen instead of 

 water the black lava-like flow of stones, the slow progression of which has 

 nothing like to the flow of liquid. 



'' At other times, again, we find the torrent falls like thunder. It is 

 announced by a rumbling roar in the interior of the mountain range, and 

 at the same time a furious wind escapes from the gorge. These are the 

 precursory signs. In a few instants the torrent appears in the form of an 

 avalanche of water, rolling before it a heaped-up mass of blocks of stones. 

 This enormous mass forms a moving barrier, and such is the violence of the 

 impulse that the stones may be seen leaping before the waters become 

 visible. The hurricane which precedes the torrent is accompanied by efiects 

 still more surprising It makes stones fly in the midst of a whirlpool of 

 dust ; and there have been seen sometimes on the surface of a dry bed 

 blocks moving as if propelled by some supernatural force. 



All these statements, incredible as they may appear, are attested by 

 a host of cases. I quote some of these, but I shall afterwards have occasion 

 again to call attention to the subject. 



" In 1837 several carriers, and at the same time a Conductuer des Fonts 

 et Chaussees, were stopped during a storm at the place where the torrent 

 La Oouche crosses the highway. No. 94. The torrent was then dry. All 

 at once a whirlpool of dust descended along the river-bed, and before their 

 eyes some lumps of stone cleared the road at a bound. 



" In 1821 the roadway of the bridge at Boscodon was swept away by a 

 blast of wind coming with fury from the gorge of the torrent. Immediately 

 the waters arrived, tearing along between the abutments of the dismantled 

 bridge. This event occurred within ten minutes after the Prefect of the 

 Department had passed, and under the eyes of a great number of country 

 people engaged in harvest work in the field above. The Prefect, question- 

 ing the fact, caused several of these people to appear before him, when he 

 questioned them, and held a kind of formal inquiry, which established all 

 the details which have been reported. 



"At Guillestre, in 1836, there was a frightful overflow of the stream 

 Rif-Bel, which flows through the middle of the market-town. Several 

 persons were standing near a bridge, listening to the noise made in the 

 mountain, when an enormous stone was, without apparent cause, thrown to 

 their feet, more than 4 metres, 13 feet, above the bed of the stream. 



" The torrent of the Moulettes, which threatens the market-town of 

 Chorges, overflows every year, and it gives every time an opportunity of 

 verifying facts of the kind stated. In July 1838, a little rain having fallen 

 on the summits of the mountain, this drew some of the inhabitants on to 



the embankment to see the torrent. Soon the blast of wind the avant- 



courier of what was coming— made the stones roll with such violence that 

 all these people, drawn thither by curiosity, drew back in haste. In a 

 moment the embankment which they had just quitted fell down as it were 

 BO to speak, under their heels. It was a massive wall built of stone and 



