18 E^SUM^ OF SUBELIi's STUDY OF 



or about two miles, in breadth. It never happens, indeed, that a torrent 

 covers at any one time the entire surface of this ; but in going now here, 

 now there, it threatens continually every part of it, and after some floods 

 every part may be found to bear traces of its passage. Such are the 

 torrents when they debouch into the valleys. 



" When they are traced up into the mountain passes they are seen to 

 bury themselves in between steep cleft banks, which rise to the greatest 

 heights, and thus form deep gorges. These banks, constantly undermined 

 at the base, give way, and in their fall drag with them cultivated fields and 

 adjoining dwellings. When this water-course is traced up to the sources of 

 the torrents, the ground there is seen to be spread out like an amphitheatre. 

 It forms a sort of funnel, open to the sky, which receives waters from the 

 rains, from the snows, and from the thunder-storms, and precipitates them 

 rapidly into the gorge." By this gorge, as by the neck of a funnel, the water 

 is drawn off p.nd precipitated into the water-course opening upon the lit de 

 dejection, or bed of deposit. 



In giving additional details of the principal peculiarities or characteristics 

 of torrents, he says elsewhere, " When one casts an eye over a map of the 

 High Alps he- sees a country furrowed with innumerable water-courses, 

 which are spread over the ground in a kind uf confusion. It is an aspect 

 presented by all mountainous countries. Perhaps here the confusion is 

 more manifest because of the little regularity in the arrangement of the 

 mountain chains. These run in many different directions. They constantly 

 cross each other's lines, break into each other, and disturb the straight line 

 of the valleys. From these frequent intersections results a certain disorder 

 which has for a long time engaged the attention of geologists, but no satis- 

 factory explanation of the production of which has been produced. All the 

 larger water-courses flow into the Durance, the Bu6ch, and the Drao, 

 whereby are formed three distinct basins marked out by these rivers." In 

 a note, it is mentioned that by one author, to whom I shall afterwards have 

 occasion to refer — M. de Ladoucette, author of a work entitled Historie, 

 Topographie, A ntiquites, Usages, Dialects, des Hantes A Ipes — there are reckoned 

 five distinct basins ; and by another, M. Hericart de Thury, there are 

 reckoned eight ; but the number might be increased indefinitely by 

 considering every valley a basin. The three basins spoken of receive, he 

 says, all the water-courses of the department with the exception of some 

 insignificant streams which flow to the west. And he goes on to say, " When 

 the three rivers named are followed beyond the boundary of the department 

 they all three are seen to discharge their waters into the Rhone, the first 

 retaining its name to the confluence, the other two previously losing theirs. 

 And thus it appears that all the water-courses of the department of the 

 High Alps belong to the great basin of the Rhone, one of the five great 

 basins of France. Each of the three basins is traversed by a oreat valley 

 which rises by insensible "degrees to the col, or neck, in the mountain, where 

 it originates. It receives secondary valleys, into which descend other 

 valleys smaller still, which may again be seen subdivided in a similar 

 manner. These last being, like ramifications, indefinitely subdivided, 

 of which the secondary valleys are the brauohes, while the principal valley 

 forms the trunk. 



"All of these valleys, whatever be their comparative magnitude, their 

 relative rank, or their position, are watered or drained by a stream which 

 indicates the thalweg or direction of the inclination of the valley ; and if we 



