ply examples, I ihall only offer what has fallen under
my obfervation in France ; the river Alier at its fource,
about half a league from Varenne, contains a great variety
of pebbles, of Led and yellow quartz, o f the fame nature
as thofe in the fields in its neighbourhood; but I
could not difcover one o f thefe pebbles in this river,
when it paffes by Moulins, where nothing is feen but
coarfe fand.
The Loire at its fource runs over an immenfe quantity
o f fmall pebbles, lower down, none are to be feen
when it paffes by Nevers, where the bed of the river con-
fifts of fand and large pebbles the fame as the adjacent
fields.
There is a great deal of pebble and flint in the river
Jonne, before and after it paffes by Sens, becaufe its
banks are covered with it from Joigny. The Jonne enters
into the Seine above Paris, and yet I do not believe
any body has ever feen one of thefe pebbles go through
the Pont neuf, and what is more, nobody has ever feen the
Seine bring any fort of limy pebble along with it in paf-
fing through Paris, either round or of any other fhape.
What happens in the Rhone is ftill more conclufive,
and as feveral writers have fpoken of it, and of the Lake
o f Geneva in a manner which is incomprehenfible to me,
I ihall
I ihall briefly relate what I have feen. A valley flanked
on one fide in part by the Alps, and on the other by
Mount Jura, forms the Lake of Geneva, which is about
ei ghteen French leagues in length: a fmall river with
a great many brooks falling from the mountains on
its fides fill the cavity o f the valley, and the water
which overflows, forms the river Rhone near the city;
as its depth there, is lefs than in the centre, and the
water extremely limpid and tranfparent, the pebble is
feen at the bottom covered with mois ; the waters even
with the higheft winds never moving them from thefirft
fpot where they fell in. The Rhone after it has quitted
the lake runs for fome leagues over a bed of pebble, and
then enters a narrow gorge formed by two rocks cut perpendicularly,
then paffes by the mountain of Credo,
at whofe foot the river difappears, for reafons very different
from thofe With refpeft to the Guadiana.
The Credo mountain is a compofition of fandy earth
full of round ftone, from its fummit to a confiderable
depth. There is another iimilar mountain oppofite to
it in Savoy, likewrfe full of fandy, limy pebble, granite,
and flint; the Rhone paffes between thefe two mountains
:: as the bails of the Credo confifts of ftrata of limy
rock of different degrees of hardnefs, the waters in courfe
of time have eaten their way through fuch beds as happened
to be of a fofter nature than thofe above and below,