TORRENTS OP THE HIOH ALPS. 35 



soatherly winds, so much so that sometimes in two days' time the breaking 

 up is finished and the whole of the snow has disappeared, this is one 

 powerful cause of disintegration more energetic there than elsewhere ; but 

 it is trifling compared with others, — in illustration of which he refers to the 

 clear blue sky of the High Alps, a district in which fogs, and mists, and 

 long-continued drizzling rains are unknown, though these are throughout a 

 great extent of France the normal characteristics of the atmosphere during 

 six months of the year. " Nothing," says he, " can equal the purity of the 

 air, the unchanging serenity of the heavens, there. But this dryness of the 

 air and this cloudless sky are dearly purchased, for the rains, if less frequent, 

 are the more tremendous." 



M. Dugied, author of a Memoire entitled Prcgd, de hoisement des Basses 

 Alpes, to which I shaU afterwards have occasion to refer more in detail, 

 says, in writing of this, — " It is thus that it comes to pass that the Alps 

 are sometimes months, sometimes years, without rain. Then all at once 

 the clouds gather as if from all points of the horizon, pile themselves up as 

 if pressed by opposing winds, and empty themselves in torrents which sweep ' 

 away everything in their course." 



M. SureU says, — " It is an admited fact that the quantity of water which 

 falls annually in a mountainous country— other things being equal — is 

 greater than in the country of the plains. It is also an admitted fact that 

 the quantity is augmented as we approach the tropics. It follows that 

 there ought to fall here a quantity of rain equal at least to what falls in the 

 same time in Paris. But while the faU in Paris is distributed over a period 

 of sis months, here the whole quantity is used up in some few rain-storms." 

 This makes all the difference ; and thus, to some extent, is the soil made 

 more mobile than it is elsewhere, and of this the following illustration is 

 given : — 



" There is a transition point very remarkable where the climate changes 

 all at once from that of Provence to that of the north ; it is the col dti 

 Laterat. In proportion as we rise towards this neck, in ascending the 

 valley of the Durance, and then that of the Guisanne, its a£3uent, we see 

 the serenity of the heaven disturbed, and rainy days become more and more 

 frequent. When the neck is passed, and we penetrate into the gorge of 

 Mallaval, dug out by the Komanche, in following this water-course into the 

 country called the Oysan, which is a portion of the department of Jahre, 

 there the change of climate is complete. The rains are extremely frequent, 

 and instead of falling in what seem like thunder-plumps they are prolonged, 

 and fall continuously as drizzling rain. The air is almost constantly moist, 

 and loaded with clouds. One sees the mists creeping over the sides of the 

 mountains, to catch upon the projecting rocks, and often to envelope the 

 vaUey completely. In a word, we have entered the climate of the north, 

 the same as prevails at Grenoble, and which differs in a striking manner 

 from that of Embrun, where fogs are a phenomenon almost unknown, 



" From this difference in the climate foUow corresponding differences in the 

 action of torrents. The mountains which enclose the valley of the Bomanche 

 present in many parts the same kind of ground as do those of the basin 

 of Embrun; it is a flaky, black, calcareous earth, remarkable for its excessive 

 friability. But this same soil, which in the Embrunais is furrowed by a 

 multitude of formidable torrents, shows in the Oysans only a few torrents, 

 almost effaced, without energy, and in no repect to be compared with those. 

 In the latter coimtry the mountains are seen clothed on the steepest slopes 



