GEOLOGY. 
S3 8 
beings which cover loss elevated mountain* 
with their remains, may be considered as the 
source or origin of rivers and streams. 1 he 
water which falls on their summits, flows 
down in torrents by their lateral surfaces. Iji 
its course it wears away the soil upon which 
it incessantlv acts. It hollows out a bed, or 
a depth proportioned to the rapidity of its 
course, the quantity of its waters, and the 
hardness of the rock over which it flows; at 
the same time that it carries along with it 
portions and fragments of such stones as it 
loosens in its course. 
These stones, rolled along by the water, 
must strike together, and break off their pro- 
jecting angles: a process that must quickly 
have afforded those rounded flints which 
form the beds of rivers. These pebbles are 
.found to diminish in si/e, in proportion to 
the distance from the mountain which affords 
them ; and it is to this cause that Mr. Dorthes 
lus referred the disproportionate magnitude* 
of the pebbles which form our antient worn 
stones, when compared with those of mo- 
dern date ; for the sea extending itself for- 
merly much more inland, in the direction of 
the Rhone, the stones which it received from 
the rivers, and threw back again upon the 
shores, had not run through so long a space 
in their beds as those which they at present 
pass over. Thus it is that the remains of the 
Alos, carried along by the Rhone, have suc- 
cessively covered the vast interval comprised 
between the mountains of Dauphinyand Vi- 
varais ; and are carried into seas, which de- 
posit them in small pebbles on the shore. 
The pulverulent remains of mountains, or 
the powder which results from the rounding 
of these flints, are carried along with greater 
facility than tlv flints themselves : they float 
for a long time in the water, whose transpa- 
rency they impair; and when these same 
waters are' less agitated, and their course be- 
comes slackened', they are deposited in a line 
and light paste, forming beds more or less 
thick, °ancl of the same nature as that of the 
rocks to which they owe their origin. These 
strata gradually become drier by the aggluti- 
nation'of their principles ; they become con- 
sistent, acquire hardness, and form siliceous 
clays, silex, petrosilex, and all the numerous 
class of pebbles which are found dispersed in 
strata, or in banks, in the antient beds of 
rivers. 
The mud is much more frequently depo- 
sited in the inter Tices left between the round- 
ed flints themselves, which intervals it fills, 
and there forms a true cement that becomes 
hard, and constitutes the compound stones 
known by the name of pudding-stones and 
grit-stones ; for these two kinds of stones do 
not aopear to differ but in the coarseness of 
the grain which forms them, and the cement 
which connects them together 
We sometimes observe the granite sponta- 
neously decomposed. The texture of the 
stones ’which form it has been destroyed ; the 
principles or component parts are disunited 
and separated, and they are giadually earned 
awav by the waters. . . 
Water filtrating through mountains of pri- 
mitive rock, frequently carries along with it 
very minutely divided particles of quart/ ; 
and proceeds ’to form, by deposition, stalac- 
tites, agates, rock crystal, &c. 
These quartzose stalactites, differently co- 
loured, are of a formation considerably ana- 
logous to that of calcareous alabasters ; and 
we perceive no other difference between them 
than that of their constituent parts. 
II. Thus far we have exhibited, in a few 
words, the principal changes, and various mo- 
difications, to which the primitive rocks have 
been subjected. We have not yet observed 
either germination or life ; and the metals, 
sulphur, and bitumens, have not hitherto pre- 
sented themselves to our observation. Their 
formation appears to h<? posterior to the ex- 
istence of this primitive- globe ; and the al- 
terations and decompositions which now re- 
main to be inquired into, appear to be pro- 
duced by the class of living, or organized 
beings. 
On the one hand, we behold the numerous 
class of shell animals, which came the stony 
mass of our globe to increase by their re- 
mains. The spoils of these creatures, long 
agitated and driven about by the waves, and 
more or less altered by collision, form those 
strata and banks of limestone, in which we 
very often perceive impressions of those shells 
to which they owe their origin. 
On the other hand, we observe a numerous 
quantity of vegetables that grow and perish 
in the sea ; and these plants likewise, depo- 
sited and heaped together by the currents, 
form strata, which are decomposed, lose 
their organization, and leave all the princi- 
ples of the vegetable confounded with the 
earth v principle, it is to this source that the 
origin of pit-coal, and secondary schistus, is 
usually attributed ; and this theory is esta- 
blished on the existence of the texture ot de- 
composed vegetables wry usually seen in 
sehisti and coal, and likewise on the presence 
of shells and iish in most of these products. 
It appears that the formation of pyrites ought 
in part to be attributed to the decomposition 
of vegetables : it exists in greater or less 
abundance in all sehisti and coal. A wooden 
shovel has been found buried in the deposi- 
tions of the river De Ceze, converted into 
jet and pyrites. The decomposition of ani- 
mal substances may be added to this cause ; 
and it appears to be a confirmation of these 
ideas, that we find many shells passed to the 
state of pyrites. 
Not only the marine vegetables form con- 
siderable strata by their decomposition ; but 
the remains of those which grow on the sur- 
face of the globe ought to be considered 
among the causes or agents which concur in 
producing changes upon that surface. 
We shall separately consider how much is 
owing to each of these causes ; and shall 
follow the effects of each, as if that came 
alone was employed in modifying and attir- 
ing our planet. 
1 . The secondary calcareous mountains are 
constantly placed upon the surface of the pii- 
mitive mountains; and though a few solitary 
observations present a contrary order, we 
ought to consider this inversion and derange- 
ment as produced by shocks which have chang- 
ed the primitive disposition, it must be ob- 
served also, that the disorder is sometimes 
merely apparent ; and that some naturalists of 
little information have described calcareous 
! mountains as inclining beneath the granite, 
because tins last pierces through the envelope, 
I rises to a greater height, and leaves at its 
j feet, almost beneath it, the calcareous re- 
mains deposited at its base. 
Sometimes even the limestone fills to a 
very great depth the crevices or clefts form- 
ed in the granite. The writer of this article 
has seen in Gevaudan, towards Florae, a pro- 
found cavity in the granite filled with calca- 
reous stone. This vein is known to possess 
a depth pf more than 150 fathoms, with a 
diameter ot about two or three. 
It likewise happens frequently enough that 
such waters as are loaded with the remains of 
the primitive granite, heap them together, 
and form secondary granites, which may ex- 
ist above the call areous stone. 
These calcareous mountains are decom- 
posed by the combined action of air and 
water; and the product of their decomposi- 
tion sometimes forms chalk or marie. 
The lightness of this earth renders it easy 
to be transported by water; and this fluid, 
which does not possess the properly of hold- 
ing; it in solution, soon deposits it in the form 
of gurhs, alabasters, stalactites, &c. Spars 
o\se their formation to no other cause. 
Their crystallization is posterior to the origin 
of calcareous mountains. 
Waters wear down and carry away calca- 
reous mountains with greater ease than llie 
primitive mountains : their remains being 
very light, are rolled along, and more or less 
worn. The fragments of these rocks are 
sometimes connected by a gluten or cement 
of the same nature; from which process cal- 
careous grit and breccias arise. These cal- 
careous remains formerly deposited them- 
selves upon the quartzose sand ; and the 
union of primitive matter, and secondary 
products, gives rise to a rock of a mixed nalui e. 
2. The mountains of secondary schistus 
frequently exhibit to us a pure mixture of 
earthy principles, without the smallest ves- 
tige of bitumen. These rocks afford, by ana- 
lysis, silex, alumina, magnesia, lime in the 
state of carbonate, and iron ; principles which 
are more or less united, and consequently 
accessible in various degrees to the action of 
such agents as destroy the rocks hitherto 
treated of. 
The same principles, when disunited, and 
carried away by waters, give rise to a great 
part of the stones which are comprised in the 
magnesian class. The same elements, worn 
down by the waters, and deposited under cir- 
cumstances proper to facilitate crystallization, 
form the schorls, tourmaline, garnets, &c. 
We do not pretend bv this to exclude and 
absolutely reject the system of such natu- 
ralists as ’attribute the formation of magne- 
sian stones to the decomposition of the pri- 
mitive rocks. But we think that this forma- 
tion cannot be objected to for several of 
them, more especially such as contain mag- 
nesia in the greatest abundance. 
It frequently happens that the secondary 
sehisti are interspersed with pyrites ; and, in 
this case, the simple contact of air and water 
facilitates their decomposition. Sulphuric 
acid is thus formed, which combines with the 
various constituent principles of the stone; 
whence result the sulphates of iron, of mag- 
nesia, of alumina, and of lime, which efflo- 
resce at the surface, and remain confounded 
together. Sehisti of this nature are wrought 
in most places where alum-works have been 
established ; ■and the most laborious part of 
this undertaking consists in separating the 
sulphates of iron, of lime, and of magnesia 
from each other, which are mixed together. 
Sometimes the magnesia is so abundant that 
