£00 E A R T II. 
turf; it varies according to local circumflances ; but not 
according to the elevation ; for, c ceteris paribus, 1 have found 
it fenfibly of the fame thicknefs on the lowed and hi.gheft 
grounds; a diredt proof, that-thbfe diverfely elevated parts 
of our continents were not Incceflively, bur at once, aban¬ 
doned by the Jia. In the places where no particular caufe 
has either didurbed or forwarded vegetation, that vegetable 
layer is about eighteen inches thick. This then is the 
whole produfl: of that particular operation, begun at the 
origin of our continents. 
There are many ways by which we can find a modulum 
for concluding, from the above phenomenon, the age of 
our continents-, but I (hall confine myfelf to one, as fiiflori- 
cal monuments are the means of obtaining it. In the un- 
didurbed heaths of Germany, and efpecially upon barren 
hills of great extent, are found numbers of tumuli, or bu¬ 
rial-places of the fird and dill rambling inhabitants of 
the country: I have had the opportunity of fearching 
fome of them ; they are heaps of earth and dones, cover¬ 
ing urns, in which are found remains of bones and allies. 
In the places where a great many of thofe tumuli are on 
the fame fpot, there is often fomething like an altar, 
formed of two upright dones with one acrofs on the top ; 
and in fearching round thofe places, fome indcuments 
have been found made of flint and in the form of knives. 
Thofe heaps of moved foil are now covered with vegeta¬ 
tion-, and tile vegetable layer under the turf differs fo little 
in thicknefs from that of the neighbouring undiflurbed 
grounds, that if we did not confider that a certain length 
of time was requifite before vegetation could be generally 
fpread, we (liould be led to refer the origin of our conti¬ 
nents to a very tittle didance beyond the epocha when 
thofe tumuli v.ereheaped. 
It lias been agitated among philofopiiers, whether or 
not the hijlory of arts and fciences can throw any light on 
the degree of the antiquity of mankind. I have no doubt 
in refpedt of the affirmative; if we only didinguifh what 
human underdanding can difeover by following the con- 
fequences of fome axioms, (as in geometry and mechanics,) 
and what may be concluded from confpicuous and well- 
obferved phenomena (a^in adronomy) ; from what cannot 
be attained by long obfervations and experiments, tranf- 
mitted from one generation to another, pading through 
many errors afterwards corrected (as in natural pliilofo- 
phy and natural liidory). But this would lead me too 
far; therefore I fhall confine myfelf to one objedt, that of 
- the progrefs of agriculture : and as I have dated many fadls 
of that clafs in my Letters on the Hijlory of the Earth and 
of Man, I (hall now only mention the general refults of 
my observations in that refpedt. I mud here didinguilh 
two dates of culture as now obferved upon our continent ; 
one of which relates to their completely inhabited parts, 
where the origin and progrefs of fettlements are fo much 
effaced, that it would be very difficult, if not impodible, 
to trace them by immediate obfervation : the other of 
countries in which the inhabitants are very few in com- 
parifon to the extent of the land, but where they are in- 
leafing in number, in proportion as culture is gaining 
over grounds never cultivated before : which lad cafe is 
that of the greated part of Afia, and of much of the 
north-ead of Europe: here the progrefs of culture and fet¬ 
tlements is very didindt, and the following are the general 
faffs obfervable in that refpedt. 
In all thofe countries there are certain centres of culture , 
or more ancient fettlepients ; which, with fubordinate cen¬ 
tres of different degrees round them', are, in the wildernefs, 
like the fydems of celefial bodies in Jpace. The main centre 
of culture and fettlement fird exided, and from that have 
fprung colonics, which have been new .centres afterwards 
themfelves furrounded by fubordinate fettlements. Hence 
the origin of didindt nations, or of the fird empires, with 
their fubdivifions, into provinces, diftridts, commons, 
and private lets cf families ; which fubdivifions have been 
aided by the main centre, or at lead have enjoyed through 
it the protedting power of the whole fyjlem. The Imallelt 
fubdivifions, like the fmall branches of trees, are thole 
which, by inceffant endeavours to extend culture, contri¬ 
bute the mod to aggrandize the empire, and to increafe the 
drength of the other branches and of the dem itfe-lf. 
All the accounts which are given of tire progrefs of 
culture in Afa, correfpond in that refpedt with what I 
have obferved in the wilderneffs of the north-ead of Eu¬ 
rope. I may give that name to countries, which, when 
only known from maps or political hidories, may 'appear 
wholly cultivated and intirely inhabited; while in fact: 
they are, what I have deferibed before, lets of centres of 
culture in the zoild heath. The original fettlements were 
modly along main f reams, and in the parts of their courfe 
were a great extent of fdiments, fird gathered, had been 
abandoned by the rivers, when they were fettled in deeper 
channels. Thofe rich foils, producing abundant and 
lading padure, dopped fome rambling diepherds, who 
fixed there, by fird contriving fome fort of huts, and 
planting round them the fruit-trees and particular plants, 
which, growing fpontaneoudy in other places, had been 
a part of their food. A more fedentary life increafed 
their families; they found a fatisfaction, before unknown 
to them, in their focial intercourfe ; and the fird endea¬ 
vours of thofe fettlers towards culture, were produced by 
their defire of remaining together. That wifli, naturally- 
excited by the enjoyment of mutual fervices, was in¬ 
creafed by the neceflity of guarding againd invaders the 
effects of their labour, which had produced a greater 
and a more permanent fertility : therefore, in proportion 
as they multiplied, they augmented the number of habi¬ 
tations on the fame fpot; till at lad, as they alfo occu¬ 
pied more land, they found it inconvenient to carry on 
culture at too great a didarjee. Then they began to form 
colonics beyond their convenient fphere of activity ; affid- 
ing them in their did fettlement, and remaining bound 
to them by the reciprocal ties of frienddiip, mutual be¬ 
nefit, gratitude, and common fecurity. 
The extent of the grounds whofe natural fertility had 
produced thofe nurferies of men being limited, they at 
lad were obliged to fend colonies to greater didances: they 
then looked round for rivulets, dales, borders of foreds, 
and other defirable fpots, with favourable means of com¬ 
munication between the multiplying rifew fettlers ; and, 
at lad, when thofe refources were alfo exhauded, their 
increafed power and indudry prompted them to extend 
culture over the lei's fertile grounds between them, and 
at greater didances. One of the pradtices of higheft an- 
tiqui'.y in thofe difficult fettlements was, that of drfl 
choolingthe mod convenient fpot at fome didance, often 
very great; and after having cut a ditch round the deter¬ 
mined place, and raifed its internal lide with the mate¬ 
rials taken from if, to enrich the enclofed land by the 
vegetable layer belonging to the neighbouring grounds, as 
far as they conveniently could get it. Thofe ftript fpots 
are foon covered with'a new vegetation, and the cattle, 
grazing on them, keep down the young heath ; by which 
means they fometimes become tolerable padure : the 
more remote parts remain wild, and they lerve only for 
rambling flocks of Iheep, and for great quantities of bees, 
which feed on the bloom of the heath. For all thofe 
undertakings, the new fettlers were fird affided by their 
families, and afterward by the government and by the dock 
of difeovered means : then the fuccefsful colonies helped 
their own families round them. By thofe means, the in* 
dealing difficulties on lefs favourable lands were com. 
penfated by the increafing power of the protedfing centres , 
and by the progrefs of the arts of agriculture. 
Thofe endeavours have never ceafed from the earlieft 
times; they go on, in thofe numerous parts of our conti¬ 
nents where the cultivated grounds are dill like Jlands in 
wilderneffs ; and the progrefs from each original centre of 
culture may be traced back, by only obferving what is 
going on in its d;irts, and round each of its fird didant 
fettlements. None of thofe Jyfhms of culture are at red, nor 
can be found to have (topped at any time : they are 
thriving 
