m EARTH, 
grounds pervaded by the great river, as the dales are to 
the vale in the fyftem which he has furveyed. Confe- 
quently, all thofe Jlreams have fixed channels, determined 
by the original form of the furface of our continents ; and, 
fince natural caufes aft always in the fame manner, by the 
fame circumflances, he cannot doubt that clear data for 
the calculation of the age of our continents, are to be found 
along many of thofe Jlreams. 
In the courfe of his furvey, our obferver has taken 
notice of another clafs of phenomena, which appears to 
him clearly expreffive of the little age of our continents. 
He has found, in the upper parts of his Jyfiem, fcattered 
eminences, confiding of deep decaying rocks, which, from 
their fituation, mud have condantly been out of the reach 
of every podible Jlream, ever fince their origin as dry land ; 
along which he has found undidurbed Jlopes, formed of 
fallen materials, and rifing againd their abrupt and dill 
decaying fides. That obfervation recalls to his mind 
many elevated plains, which alfo, ever fince they have 
exided, mud have been above the level of every Jlream ; 
and on which, however, rife inhibited hills or hillocks, 
compofed of Jlony firata, which, dipping one fide into the 
ground, prefent their abrupt feftio'ns on the oppofite fide. 
That clafs of phenomena drikes him as a very important 
one: for tho fe -eminences mud have exided in a date of 
decay from the origin of our continents ; and the rubbiih 
accumulated under their deep furfaces fometimes bears 
no refemblance to the furrounding foil. There then pro- 
grrffes of cffcEls may be obferved, unmixed with, foreign 
caufes of any importance ; and the above general formula, 
for finding time pajl by lajling operations , may be applied 
to thofe grounds with more accuracy than Aong Jlreams. 
The fpirit of drift analyfis being thus raifed in our ob¬ 
ferver, he conceives ladly this general idea, that all the 
caufes which have afted on the furface of our continents, 
ever fince they have exided, being known, and the nature 
of their effefts being alfo determined, thofe ejfeEls mud be 
cafily didinguilhed from what exided before they took 
place ; and that confequently, a number of fitch effefts , 
(not only of different natures, as proceeding from diffe¬ 
rent caufes, but even without any conneftion with each 
other, excepting that of time,') might afford didinft chro¬ 
nometers, which, by their reunion, would lead to a natu¬ 
ral chronology, overlooked till now, from a precipitate 
decifion that it was not to .be found. 
J have now, fir, under the affumed charafter of an 
obferver, given you a (ketch of my own hidory, in a 
courfe of condant obfervation for-above forty years. I 
conceived, very early, the importance of an exact deter¬ 
mination of the changes which have happened to our con¬ 
tinents, from the time of their exidence as dry land-, and 
very foon alfo I perceived, that curfory obfervations 
could not afford any certain refults in that refpeft. I 
then began to fix my attention on thofe parts of the 
mountains, or other high grounds, which, from their 
.elevation above every podible (either pad or prefent) 
Jlream, could not iiave been affefted, at any time, but by 
the direft aftion of rain or fnovj, and by their immediate 
confeqtiences. There, however, frequently finding the 
fame great excavations, which, in lower grounds, are 
vaguely attributed to running waters, the fallacy of this 
lad idea druck me ; and I fird concluded, that thofe ex¬ 
cavations exided from the origin of one- continents. There 
alfo I could dudy, without any podible midake, the ef- 
feftsof all the immediate caufes which have afted on the 
abrupt parts of the furface of our continents, ever fince 
they have exided ; namely, the tendency of thofe parts 
to moulder down by the effefts of the weather-, the pro- 
grefs of that decay ; its tendency to an end, when the rub- 
bifh is undidurbed ; the caufes that can didurb it; and 
the maximum of their effefts. That preliminary dudy 
enabled me, afterward, to didinguifli, in other places, 
the real effefts of running waters, from the effefts of 
other caufes, which are only rendered effeftual by certain 
original dates of the grounds, eafily traced back; and from 
that fingle diferiminatioft of caufes, light fucceeded to 
the obfeurity in which the phenomena of the furface of 
the earth had been involved by forne geologids : for then, 
rendered attentive to origins and progrejfes of natural ope¬ 
rations on our dry land, 1 found many different claffes of 
them, which fix its origin at a time not very remote. 
The importance of the final refult of thofe obferva¬ 
tions has made me defirous to facilitate them to others, 
by fketching a plan of refearches, and pointing out the 
objefts which are to be examined. That dudy is, in a 
great degree, almod within the reach of every man; for 
there is hardly any country which does not afford-fome 
of the claffes of phenomena, which may lead to the age 
of our continents ; and I have known from experience, 
what intered fuch a fixed and endlefs object of obferva¬ 
tion can fpread on the fuppofed lod hours of travelling or 
airing. After a little pradtice in that kind of obfervation, 
the effefts of the principal caufes which have afted on 
every part of our land, may eafily be didinguilhed : the 
effefts produced by each of thofe caufes, in former times, 
have left clear monuments : their prefent operations are 
feen ; and the whole together affords various meafures of 
time, which I (hall next explain. 
The following-are the principles of invedigation which 
may enable us to difeover the time when our continents 
began to ex id.—id, To find out fuch effefts as could only 
begin at that time, but mud neceffarily have begun then. 
—2d,To determine the mode of aftion of the caufes which 
produce thofe effefts. —3d, Toexamine, whether the whole 
of the operations thus determined, may be known ; by en¬ 
deavouring to difeover what was the date of things in 
thofe parts of our continents at their origin. —4th, To com¬ 
pare the parts oi thofe effefts which have been performed 
within the memory of men, with the whole of what lias 
been produced .—5th, To direft the fame inquiry to vari¬ 
ous claflesof effefts having thofe determined charafters, in 
order to find out whether the feparate deduftions drawn 
from them, coincide in refpeft of the tiyie when their va¬ 
rious caufes began to aft on our new-born continents. 
Whatfoever be the clafs of geological phenomena which 
we examine with that view, the principles of enquiry are 
the fame. It is evident, for indance, that all the waters 
which unite in one main fream, arriving ladly at the fea, 
proceed from a fet oj grounds, whofe declivities tend to¬ 
wards that common receptacle : and that no material al¬ 
teration can have happened to that fet from the beginning ; 
fince, for the production of any change in that refpeft, 
the original high boundaries of the various fyjlems of 
grounds, thus didinguilhed, ought fird to have been de- 
ftroyed; while thofe high lands are the very parts of our 
continents where the aftion of running waters is at its mi¬ 
nimum, and confequently incapable of producing any ef- 
fential alteration in thofe boundaries. That incontrover¬ 
tible propofition puts a dop to all wandering conjeftures : 
each of the various fyjlems of grounds whence a main 
Jlream proceeds, is the fame that it was at the origin of 
our continents: and by fetting out from that fird relult of 
theory and obfervation, I have clearly determined two 
didinft caufes of alteration in the original fate of thofe 
fyfiems ; one proceeding from the decay of their feep parts ; 
the other from the aftion of running waters. The effefts 
of thofe two only caufes of dedruftion, are as didinft 
as the caufes themfelves ; their accumulation, from the 
time when they began, is very confpicuous; and their 
progrefs in a given time, is traced by monuments. From 
thofe very intelligible phenomena, I have already demon- 
drated that our continents have undergone but very linall 
and well-determined alterations ; and in my prefent en¬ 
quiry into their age, I (hall begin by the fame phenome¬ 
na, in which we (hall find various kinds of chronometers. 
Let us return to the highed boundaries between feparate 
fyfems of running waters on our hemifplrere ; namely, the 
tops of the Alps. There we find immenfe ruins of firata , 
the mod part of which, being turned up, form the tow¬ 
ering fummits of thofe mountains. The chaotic date of 
thofe 
