always found upon
the junction of the alpine with the level countries. Such an appearance,
I am inclined to think, may be found in the Val d'Aoste, near Yvree. M.
de Saussure describes such a stone as having been employed in building
the triumphal arch erected in honour of Augustus. "Cet arc qui etoit
anciennement revetu de marbre, est construit de grands quartiers d'une
espece assez singuliere de poudingue ou de gres a gros grains. C'est une
assemblage de fragmens, presque touts angulaires, de toutes sortes de
roches primitives feuilletees, quartzeuses, micacees; les plus gros de
ces fragmens n'atteignent pas le volume, d'une noisette. La plupart des
edifices antiques de la cite l'Aoste et de ses environs, sont construits
de cette matiere; et les gens du pays sont persuades que c'est une
composition; mais j'en ai trouve des rochers en place dans les montagnes
au nord et au-dessus de la route d'Yvree."

We may now come to this general conclusion, that, in this example of
horizontal and posterior strata placed upon the vertical _schisti_ which
are prior in relation to the former, we obtain a further view into the
natural history of this earth, more than what appears in the simple
succession of one stratum above another. We know, in general, that all
the solid parts of this earth, which come to our view, have either
been formed originally by subsidence at the bottom of the sea, or been
transfused in a melted state from the mineral regions among those solid
bodies; but here we further learn, that the indurated and erected
strata, after being broken and washed by the moving waters, had again
been sunk below the sea, and had served as a bottom or basis on which to
form a new structure of strata; and also, that those new or posterior
strata had been indurated or cemented by the consolidating operations
of the mineral region, and elevated from the bottom of the sea into the
place of land, or considerably above the general surface of the waters.
It is thus that we may investigate particular operations in the general
progress of nature, which has for object to renovate the surface of the
earth necessarily wasted in the operation of a world sustaining plants
and animals.

It is necessary to compare together every thing of this kind which
occurs; it is first necessary to ascertain the fact of their being a
prior and posterior formation of strata, with the mineral operations
for consolidating those bodies formed by collection of