E A R T H. 
180 
feat object will be only thofe parts of the Alps where a 
fnfficient vegetation can reach, and which inclofe com- 
pletely that part which I fet afide for the prefect. It is 
certain that every fieep rock is falling down fader or flower; 
and thefe are the fragments which you think ar e propeltid 
along the inclined furface of the earth , to be delivered into the 
lea by the moving vjater : let us then follow their courfe. 
It is evident, that the fragments of tumbling rocks nntft 
fir ft accumulate under them, and rife there in a flope, 
which I Hi all call talus ; a word ufed in fortification, for 
that fort of doping grounds which have the 'natural de¬ 
clivity of loofe materials rolling over one another. Ta- 
lufes of that fort are found now- on.all the fides of every 
ridge of the Alps-, and they may be divided into three 
claffes, in refpedt of their forwardnefs. The firft clafs is 
under rocks , ftill very high, and decaying very faft. 
Thefe talufes are almoft barren ; the conftant fall of new 
rubbifh prevents vegetation from covering them : they 
are known to increafe both in extent and in height, and 
by increafing in this laft dimenfion, they tend to cover 
the fteep furface of their rocks. The fecond clafs is un- 
dei rocks which, either originally were only fteep at their 
upper part, or were much difpofed to crumble down. 
Thefe talufes, though ftill barren towards the top, are, 
more or lefs, covered with vegetation in their lower parts; 
for here the acceflion of new materials is lefs frequent, 
the larger fragments only roll down, and by their ac¬ 
quired velocity, they extend the bafe of the talus. There 
the fliade produced between the large materials, preferves 
more moifture; mofs begins to cover them, and it be¬ 
comes the receptacle of the feeds of other plants, whole 
decay forms a firft ftock of vegetable earth between the 
ftones. Then ligneous plants alfo begin to grow ; and, 
•when vegetation is fo eftablifhed, it fights its way up, co¬ 
vering and binding fitcceflively the new falling materials. 
Laftly, a third clafs of talufes is found under rocks, whole 
decay is nearly, or entirely, at an end. Here vegetation 
lias got up to the remaining veftiges of the rocks-, which, 
if no longer decaying, are themfelves covered with mofs. 
There are frequently many rows of thofe talufes at dif¬ 
ferent heights on the fame fides of high mountains: in 
that cafe the upper ones undergo the fate of the rocks 
over which they are forming. Sometimes the operation 
ends in a fuccelfion of Jlopes. and terraces ; and, in fome 
ether cafes, the whole fide of the mountain is reduced to 
one Angle Jlupe. Various forts of vegetations cover thofe 
talufes; under Ihiveritig rocks they are generally covered 
with grafs and a few llirubs : if their materials, though 
fmall, are not in flakes, they are moltly covered with 
flirubs ; and, where the materials are larger, trees are the 
dominant products of the foil. In the immenfe talufes of 
the Alps, there are frequently three diftinft zones, deter¬ 
mined by their elevation, and alfo by the flze of the ma¬ 
terials ; the lowermoft are forefts, the middle ones are 
thickets, and the uppermoft are paftures. That operation 
is, either finifhed or going on, within and all round fteep 
mountains; and, when it is completed, both in the large 
valleys and in the external parts, it produces an ever- 
lafting fecuri ty againft further demolitions by vuind and 
rain. For the whole of that ground is covered by vege¬ 
tation, and flocked with vegetable earth-, and this ought 
to be torn oft’, before any of the fragments under it could 
be moved : while, on the contrary, the quantity of that 
earth is conftantly increafing by the decay of plants, 
whofe roots, in the mean time, bind the materials more 
and more. Thefe talufes, to which every fteep mountain 
has been, or tends to be, reduced, cannot have then any 
aggrelfors but men and f reams-, and I will examine the 
operations of both. 
The inhabitants of the mountains, both w ithin and round 
them, make great ufe of the lower parts of thofe talufes, 
when they are compofed of an arable foil; and this is in¬ 
evitably brought down by culture. If the hufbandman 
has a fnfficient fpace at the bottom of the Hope, he does 
«ot trouble himieif with that effect of his work: for the 
parts of the flope which lie does not cultivate, as being 
too high, follow by degrees the parts that lubflde by cul¬ 
ture : and the only confequence of the operation is, that 
the whole talus tends to acquire a fmaller degree of de¬ 
clivity. But if, either by other proprietors, or for want 
of room in the bottom, the cultivator is confined to a 
certain fpace, then begins his care for the prefervation of 
the foil : he flops the fmaller materials by ditch.es, and 
the larger by walls. In vineyards, where the culture 
has the greateft tendency to level the Hope, the vine-dref, 
fer extends further his care : his yearly work in winter 
is to bring up on his back the foil that he has brought 
down by digging downwards. Through thefe precau¬ 
tions, prompted to each individual by felf-intereft, thofe 
bulwarks of mountains are as fafe in the hands of men as 
we have feen them in the hands of nature. 
Streams will at firft appear more powerful agents for 
the deftruftion of mountains ; but let us fo.llow their 
operations, and begin from the high valleys, where Hid¬ 
den torrents are formed, at every heavy rain, and great 
thawing of the fnow. Thefe violent freatns dafh againft 
every talus, which, in extending itfelf, has reached their 
bed. As long as a torrent can bend its courfe round fuch 
projections, it is only repelled ; but by their increafe 
there comes a moment when, falling upon them with 
great violence, it undermines them, and produces at 
once a great Aiding down of the furface of the talus, even 
though fometimes already covered with trees. Thefe 
momentary dams force the water to rife ; but its increaf¬ 
ing weight at laft breaks them ; and the impetuofity with 
which it falls, favoured by the ufiially great declivity of 
thofe narrow valleys, gives it the power of driving along 
the moft part of thole materials which had been accu¬ 
mulated gradually within its reach. Here, fir, you might 
fay with reafon, “ the .travelling materials are purfued hy 
the moving water, and propelled along the inclined fur- 
face of the ground: ” but they only travel for a Ihort time: 
in every hollow place, or in any part where the torrent 
can fpread, it lofes the power of driving them ; thereby 
are filled up all the deep parts of its bed, and all the fi- 
nuofities of the valley through which it runs; and if, 
when every part of that valley is levelled in its breadth, 
and reduced to an equal declivity, the talufes are not yet 
retired to a proper di(lance and fettled there, the new ac¬ 
cumulated materials are propelled by the torrent down 
to fome large valley, where at laft they are flopped ; for 
there the torrent can fpread without bounds. At the be¬ 
ginning of thofe operations, cafcades were formed in many 
of thofe outlets frorrunarrow valleys into large ones ; but 
now, in moft parts, the materials brought down by the 
torrents, which have been accumulated there in the form 
of very obtufe femi-cones, reach the entrance of the defiles, 
and the torrents flow over them. Not one of the frag¬ 
ments of the high parts of the mountains comes out of 
them but through fuch a pallage ; confequently we have, 
in thofe femi-cones, the whole of the rubbifh that does 
not remain in the upper parts ; and we fhall not lofe fight 
of it, nor even of the dufr, which is carried away at firft 
by the torrents. 
Thefe fecondary accumulations of fragments, proceed¬ 
ing front the high regions of great mountains, are very 
confpicuous in their large valleys; and they are now of 
the three claffes already deferibed in refpeit of the prir 
mary talufes. In the parts where the torrents continue to 
produce great havoc above, the femi-cones are ftill barren; 
a continual recruit of new materials, in times of great 5 
floods, prevents vegetation. When the great demolitions 
above are become rare, vegetation begins to take poffef- 
fion of tlie parts which the torrent, by dividing itfelf in 
many branches upon the flope, has abandoned. Laftly, 
in many places, where every great revolution in the up¬ 
per valleys is at an end, the torrent ,.confined in various 
furrows that it has formed, leaves full fcope to vegeta¬ 
tion, upon a foil which yields to all forts of culture. 
There hamlets and villages are built, near the lefs tur- 
z bulentj 
