have
occasioned sudden changes upon the surface, in having removed immense
quantities of the solid body, and in having deposited parts of the
removed mass at great distances from their original beds. Others again,
in acknowledging the natural operations which we see upon the surface of
the earth, have only supposed certain occasions in which the consequence
of those natural operations have been extremely violent, in order to
explain to themselves appearances which they know not how to reconcile
with the ordinary effects of those destructive causes.

The theory of the earth which I would here illustrate is founded upon
the greatest catastrophes which can happen to the earth, that is, in
being raised from the bottom of the sea, and elevated to the summits of
a continent, and in being again sunk from its elevated station to be
buried under that mass of water from whence it had originally come. But
the changes which we are now investigating have no farther relation to
those great catastrophes, except in so far as these great operations of
the globe have put the solid land in such a situation as to be affected
by the atmospheric influences and operations of the surface.

The water from the atmosphere, collected upon the surface of the earth,
forms channels to itself in running towards the sea or lower ground; and
it is these channels, increasing in their size as they are diminished in
number by the uniting of their waters, that give so clear a prospect of
the operations of time past, and prove the theory of the land being in a
continual state of decay, and necessarily wasted for the purpose of this
world. Every description, therefore, of a river and its valleys, from
its sources in the mountains to its mouth where it delivers those
waters to the sea, is interesting to the present theory, which is the
generalization of those facts by which the end or intention of nature is
to be observed. M. Reboul, in a Memoir read to the Academy of Sciences
at Paris in 1788, has given a very distinct view of the _Vallee du Gave
Bearnois dans les Pyrenees_; there are many things interesting in this
memoir; and I shall now endeavour to avail myself of it.

"Le torrent qui porte le nom de Gave de Pau parcourt depuis sa source
pres des limites de l'Espagne, jusqu'a la petite ville de Lourde, une
vallee qui se dirige du sud au nord sur une longueur d'environ dix
lieues. Cet espace, qui forme son lit dans l'interieur des Pyrenees,
ressemble moi