om this very good observator, and from M. de Luc[23].

[Footnote 23: Vid. Discours sur l'Histoire Naturelle de la Suisse,
passim; _but more particularly under the article of Route du Grindle_
wald a meiringen _dans le pays de Hasti:_ Also Hist: de la Terre, Lettre
30. p. 45, et Lettre 31. page 68, etc.]

I will now only mention one from this last author, which we find in the
Journal de Physique, Juin 1792.

"Entre Francfort et Hanau, le mein est borde sur ses deux rives, de
collines dans lesquelles la _lave_ se trouve enchassee entre des
_couches calcaires_. Ces _couches_ sont tres-remarquables par leur
contenue, qui est le meme au-dessus et au-dessous de la _lave_, et qu'on
retrouve dans les _couches_ d'une grande etendue de pays, ou, comme
d'ordinaire, on voit leurs sections abruptes dans les flancs de
collines, mais sans _lave_, excepte dans le lieu indique."

The particular structure of those lime-stone strata, with the body of
basaltes or subterraneous lava which is interposed among them, shows
evidently the former connection of those two banks of the river, by
solid matter, the same as that which we see left there, and in the
flanks of those hills. That which is wanting, therefore, of those
stratified masses, in that great extent of country, marks out to us the
minimum of what has been lost, in having been worn by the attrition of
travelled materials.

I would now beg leave, for a moment, to transport my reader to the other
side of the Atlantic, in order to perceive if the same system of rivers
wearing mountains is to be found in that new world, as we have found it
in the old.

Of all the mountains upon the earth, so far as we are informed by our
maps, none seem to be so regularly disposed as are the ridges of the
Virginian mountains. There is in that country a rectilinear continuity
of mountains, and a parallelism among the ridges, no where else to be
observed, at least not in such a great degree.

At neither end of those parallel ridges is there a direct conveyance for
the waters to the sea. At the south end, the Allegany ridge runs across
the other parallel ridges, and shuts up the passage of the water in that
direction. On the north, again, the parallel ridges terminate in great
irregularity. The water therefore, that is collected from the parallel
valley, is gathered into two great rivers, which break through those
ridges, no doubt at the most convenient places, forming two great gapes
in the _blue ri