t les lits sont plus
on moins sensibles et inclines, et d'une grande durete. Leurs parties
constituantes sont un mica argilleux dont les lames ou les parties sont
plus ou moins grandes et brillantes et diversement colorees: elles sont
traversees de filons et de veines meles de rognons et de globule de
quartz ordinairement blanc, quelquefois vitreux, transparent, opaque ou
grenu: nous n'y avons vu des granits que sur le penchant de la montagne;
ils y etoient isoles et roules. Quelqu'un qui aura plus de temps, plus
de loisir, decouvrira peut-etre d'ou ces masses proviennent[21]."

[Footnote 21: M. de Saussure, in his 2d volume of Voyages dans les Alpes,
has shown the origin of these travelled granites, and traced the way by
which they have come.]

We have here a picture of one of those valleys which branch from, or
join the main valley of the Rhone. In this subordinate valley, there is
the most evident marks of the operations of water hollowing out its way,
in flowing from the summits of the mountains, and carrying the fragments
of rocks and stones along the shelving surface of the earth; thus
wearing down that surface, and excavating the solid rock. On the summit
of the mountain, again, there is an equal proof of the operation of
water and the influences of the atmosphere continued during a long
succession of ages. It is impossible perhaps to conjecture as to the
quantity of rock which has been wasted and carried away by water from
this alpine region; the summits testify that a great deal had been above
them, as that which remains has every mark of being the relicts of what
had been removed, and moved only by those operations which here
are natural to the surface of the earth. Let us now abstract any
consideration of that quantity above the summits of those mountains, as
a quantity which cannot be estimated; and let us only consider all the
cavity below the summits of those ridges of mountains to have been
hollowed out by those operations of running water which we now have in
view.

In taking this view of the mountains on each side which supply the water
of the Rhone, what an immense quantity of stones, of sand, and fragments
of rock, must have travelled in the bed of that river, or bottom of
that valley which receives the torrents coming from the mountains! The
excavation of this great valley, therefore, will not be found any way
disproportionate to that which is more evident in the branches; and,
though the experien