EAR 
of thofe proceeding from higher grounds, have palled 
farther. Thefe grounds lie in wide parts or the dales, 
which parts originally were hollow ; and there alfo, as 
jn the vale, the /lopes, produced by the decay of the (ides, 
defeend without interruption, from the upper abrupt 
parts (if any remain) down to the horizontal foil: thofe 
fopes were formed originally round ('mall lakes, in which 
the fpread water had no power to difturb them ; and 
thofe lakes have been filled, firft with fragments, and then 
with fand-, the-whole proceeding from above: but in 
greater declivities and narrower pafiiiges, many of the 
Jlopes are divided in their height by abrupt fedtions ; the 
diigheft and vnoft ancient parts being in decay, and new 
fopes having been formed under them. This is found 
in very deep parts of the chafm, which receive a great 
abundance of water in times of flood, and are much wider 
xiverhend than in the bottom. In fitch parts of the dales, 
the firft fopes produced by their decaying fides could 
only be preferved fo long as they did not obftrudt the 
courfe of the water : for when they came to meet, from 
fide t® fide, they were foon deftroyed, and their materials 
were carried away by the dream. Such demolitions were 
frequent, as long as the trough remained too narrow to 
contain a moderate quantity of water: but thereby the 
decay of the Tides was more rapid, as they remained un¬ 
covered with jlopes ; and the paflage widened : but when, 
by thofe repeated deriiol i i ions of the Jlopes, they were re¬ 
tired to fuch a diftance, as to be out of the reach of com¬ 
mon floods, they rofe againft the decaying rocks, and 
vegetation binding their furface, it tvas no longer fufeep- 
tible of Aiding down. However, thofe firft fettled fopes 
•were not yet fafe ; in extraordinary floods they were at¬ 
tacked at the bottom, and afterwards, while they were 
increafing in height, from the continued decay of the 
rocks above, their abrupt fections mouldered by the 
weather: tltence fopes under fopes, the lowed of which 
were from time to time attacked by great torrents , till 
they were removed out of their reach. 
Such are the general claftes of fucceflve operations, 
which our obferver clearly traces on the Tides of his 
dales ; and their varieties in different parts, may gene¬ 
rally be affigned to determinable differences in the origi- 
nal fate of thofe parts. Some rocks, for inftance, peep¬ 
ing here and there out of the (loping grounds, betray the 
original ruinous date of thofe fides, and (hew evidently 
that the chafm has been the effeift of a convulfion : im- 
menfe pieces of rock were, at firft, either projefting out 
of the broken (ides, or heaped againft them ; and now 
they are almoft buried in a quantity of rubbifh, which is, 
or will be in time, bound together by vegetation. In every 
part where thofe (loping grounds have already their bale 
out of the reach of torrents, they are covered with ver¬ 
dure: the rain, which they can only receive from the 
air, finks into their porous foil ; and being collefted in 
millions of internal channels, it only helps to feed the 
fprings. The moift part of thofe grounds, though from 
a long time covered with vegetation , ftill receives rubbifh 
from the deep upper parts; but mofs, herbaceous plants, 
and fhrubs, bind fucceffively thofe layers of new foil into 
a tenacious cruft, unimpairable by the weather. This is 
the caufe why fo few large fragments of the ftill decaying 
parts of the dales are now carried down to the general 
receptacle : the fragments which, in their firft fall, attain 
the bed of the torrents, or thofe which are ftill torn by 
thefe from their banks, if- propelled as far down as the 
vale, fttbfide there, forming promontory-like accumula¬ 
tions over the general level. Nothing then, bat fand, is 
now, in thegreateft flood, floated by any of the f de-torrents, 
when they meet together in the vale ; and the whole 
quantity of that fand, which cannot remain fufpended in 
water that moves (lowly, as does that of the vale, is de- 
polited on the overflowed grounds. 
Our obferver has now accompli(hed the different pur- 
pofes for which he had undertaken that exaft furvey of 
a certain extent of grounds, which, from the origin of 
Vol. VI. No. 342 . 
T H. 193 
our continents, mud have been drained by the f.me'fet of 
channels. The firft of ihofe purpofes was to dilcover, from 
the prefent (late of thofe grounds, and the caufe aiding 
on them, the date in which (hey were when they came 
out of the fea ; and he has found that they were to be in¬ 
terfered by great chafms, the (ides of which weie abrupt, 
and fufceptible of decay by the natural caufes acting on 
our continents. His fecond purpofe was, to afcert a in the 
real effects of running waters in that area, and to diftin- 
guifh them from thole which may col!e£tivelv be affigned 
to the vjeather ; and in this refpeft he has found, id. 
That a great impetuofity is necelfary for f reams to carry 
along any materials heavier than fand. 2dly. That a 
great declivity is required to produce that impetuofity. 
3dly. That thofe waters being the refult of collected 
rain, become only impetuous by being allembled in fettled 
channels. 4thly. Tlvat before thofe firearm, once fettled, 
can propel any loofe materials, thefe mud fall in then- 
way, by caufes foreign to their own impulfe. 51h 1 y. 
That loofe materials can only come into the beds of 
f reams, by falling from feep grounds lying along them. 
6thly. That when, either at firft or in time, the falling 
fragments of feep grounds find a fuitable fpace for accu¬ 
mulation, they form fopes, which rife againft the abrupt 
furfaces, and at lad ((op their decay. 71h 1 y. That if, for 
want of a proper fpace, thofe fopes are at firft deniolifhed 
by f reams, they themfelves, with the decaying grounds, 
retire thus by degrees to greater diftances, till, placed at 
lad out of the reach of their aggreffors, they are covered 
by vegetation. Laftly, That it is only during that fettling 
of the fides of their channels, that impetuous f reams have 
loofe materials to drive along; that thofe materials, pro¬ 
pelled in great declivities, fubfide in every hollow place, 
or are fpread in wide fpaces which have lefs declivity; 
and that the fe £1 ions of thofe f dirnents exhibit at prefent 
the fucceflive work of running waters in time pad. 
The third and fundamental purpofe of our obferver, 
in analyfing thofe operations, was to difeover whether it 
were poffible, by their help, to go back, with fonte degree 
of certainty, to the time when they began , and confe- 
quently to the origin of our continents-, and he is now 
fatisfied that this view may be attained by a general for¬ 
mula, whofe conditions, as pointed out by his fyfian of 
grounds, are the following: id. A certain original fate 
of things, to be traced up from the known caufes which 
could alter it. 2dly. A meafurable quantity of alteration, 
already produced by thofe caufes. 3d 1 y. Continued altera¬ 
tions produced by the fame caufes, the quantity of which, in 
the life of a man, may be meafurable. Laftly, (as a check 
over thofe points, when it is in the nature of the object,) 
a certain quantity of alteration, ftill to be performed in 
feme parts, to reduce them to the fame unalterable (late 
already produced in other parts. This he conceives to be 
an incontrovertible manner of inquiring into the age of our 
continents: and though he finds it (till difficult to deter¬ 
mine, with a certain degree of accuracy, thofe quantities, 
which are to ferve as co-efficients in his formula-, yet lie 
conceives clearly, from the date of things in that refpetft, 
as exhibited in every part of his fyflem of grounds, that 
what has vaguely been alleged for afligning a very great 
antiquity to our land, is void of any fort of foundation. 
The only certain way of finding general laws in a clafs 
of phenomena, is to begin by fixing on a well-determined 
phenomenon of the clafs, and then analyfing it accurately. 
This our obferver has done ; and thereby he finds him- 
felf warranted to conclude, that all the diftinT congeries 
of channels, interfering every fyfem of grounds, of what¬ 
ever extent, whofe waters proceed at lad to the fea in 
one fream, were, like that of his fyjtem , original feries of 
chafms, or of other forts of hollow tracks; and that, in the 
fame circumftances, the fame operations .-which he has 
obferved, mud have taken place in thofe fyflems: for a 
great river is only a congeries of lefs ones, fimilar to 
that which came out of his vale-, and the private fyfiems 
of grounds .whence thefe fmall rivers proceed, are to the 
3 D grounds 
