TRANSLATIONS AND SELECTED ARTICLES. 261 
place gradually. The same rolled materials were seen in it, 
sand, gravel, and blocks, precisely as in the actual deposits of 
the torrent. There are a great many little differences in the constitu- 
tion of the torrent from one year to another, but it is evident that in 
the end there is a compensation, and that when we go on to 
consider the series of centuries and the whole of the cone, as 
we do here, the influence of these temporary variations, depending 
_on meteorological variations, disappear entirely, leaving apparent 
only the average and regular growth of the cone. We must also. con- 
sider, that the alluvium of the torrent is fed by the degradation of the 
surface of its hydrographical basin, which necessarily contributes 
much to regulate the growth of the cone. This hydrographical basin 
is itself regular enough, and although its surface is much inclined, it 
does not present land slides or other accidents, which could have 
troubled the course of the torrent. The partial denudation of the 
-hydrographical basin in modern times, may have accelerated a little 
the superficial degradation ; but if this effect has been sensible, which 
is doubtful enough, an augmentation would result from it, and not a 
diminution of the dates which we are going to deduce. Modern em- 
bankments having driven the torrent a little to one side, towards the 
right shore, on the inclining or north flank of the cone, the alluvium 
has concentrated itself on this side, and has since then more forcibly 
raised the surface of the soil, since it could no longer reach the 
southern fall of the cone. The documents preserved in the archives of 
Villeneuve, prove that these embankments date from the year 1710, 
. and their recent date is confirmed by the small thickness in the coyer- 
ing of vegetable earth on the incline of the cone protected by the 
dykes ; there was not, where the culture of the earth had not intervened, 
more than two or three inches (six to nine centimetres), including 
. the length occupied by the radicle of the turf. In this southern plane, 
thus protected by dykes, the works of the railway brought to light 
three layers of ancient earth, situated at different depths, and which 
had each in its time formed the surface of the cone. They were 
regularly intercalated in the gravel of the alluvium of the torrent, and 
exactly parallel to each other, and to the present surface of the cone, 
which was itself quite straight, and regularly inclined four degrees, 
following the line of the sharpest descent. It is evident that this parall- 
elism of the layers between themselves and the present surface, 
proves, in the most direct manner, the regularity with which the cone 
has grown. The first of these ancient layers of vegetable earth, was 
