EXCAVATION BY TORRENTS. 
251 
Tlie simple measurement of the cubical contents of the semi¬ 
circular hillock which he climbed before he entered the gorge, 
the structure and composition of which conclusively show 
that it must have been washed out of this latter by torrential 
action, will often account satisfactorily for the disposal of most 
of the matter which once filled the ravine. 
It must further be remembered, that every inch of the 
violent movement of the rocks is accompanied with crushing 
concussion, or, at least, with great abrasion, and, as you follow 
the deposit along the course of the waters which transport it, 
you find the stones gradually rounding off in form, and dimin¬ 
ishing in size, until they pass successively into gravel, sand, 
impalpable slime. 
as from a centre, in different directions, like the ribs of a fan from the 
pivot, each carrying with it its quota of stones and gravel. The plain 
below the point of issue from the mountain is rapidly raised by newly 
formed torrents, the elevation depending on the inclination of the bed and 
the form and weight of the matter transported. Every flood both increases 
the height of this central point and extends the entire circumference of 
the deposit. The stream retaining most nearly the original direction moves 
with the greatest momentum, and consequently transports the solid matter 
with which it is charged to the greatest distance. 
The untravelled reader will comprehend this the better when he is in¬ 
formed that the southern slope of the Alps generally rises suddenly out of 
the plain, with no intervening hill to break the abruptness of the transition, 
except those consisting of comparatively small heaps of its own debris 
brought down by ancient glaciers or recent torrents. The torrents do not 
wind down valleys gradually widening to the rivers or the sea, but leap at 
once from the flanks of the mountains upon the plains below. This ar¬ 
rangement of surfaces naturally facilitates the formation of vast deposits at 
their points of emergence, and the centre of the accumulation in the case 
of very small torrents is not unfrequently a hundred feet high, and some¬ 
times very much more. 
Torrents and the rivers that receive them transport mountain debris to 
almost incredible distances. Lorentz, in an official report on this subject, 
as quoted by Marschand from the Memoirs of the Agricultural Society of 
Lyons, says: “ The felling of the woods produces torrents which cover 
the cultivated soil with pebbles and fragments of rock, and they do not 
confine their ravages to the vicinity of the mountains, but extend them 
into the fertile fields of Provence and other departments, to the distance 
of forty or fifty leagues .”—Entioaldung der Gebirgc, p. 17. 
