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of them I expect, that by their example, they will excite curiofity and attention to numberless objects, not fo ftupendous, but equally important in the hiftory of the earth.
7. Lofty and abrupt ranges of pyramidal rocks are the wonderful borders of the icy valleys of the Alps, and every part of them is in continual decay. If decay and propulsion of materials by running waters, had been the caufes of the vast excavations manifefted by the fections of the frata all around, every channel of the waters thence proceeding, would be levelled with rubbish for, the neceffary effect of running waters propelling broken materials, is to fill up with them every hollow place, till all the grounds which they pervade, being reduced to a regular flope, they wander over thole fpread materials. Let us then confult attentively the phenomena on that firft leading question.
8. There is hardly any water that runs in those immense high valleys of the Alps: the waters that come down their steep fides, from rain or thaw of fnow, pafs immediately under the accumulated ice which fills them; where, conftantly stopped in the points of bearing of the ice upon the ground, they filtrate more than they run. This is a first view of the object, which, in the very theatre of the greateft past devaftations, excludes completely the idea, that they have been produced by running waters; and the other following facts, will only illuftrate that peremptory exclufion. 1ft, A part of the waters that come out of thofe valleys, falls in cafcades, from the edges of fteep rocks, over lower grounds: if waters, thus iffuing from under the ice, had contributed to produce the vacancies now exifting between the upper ridges, the rubbish carried off, accumulating up to thofe rocks, would have long ago prevented cafcades, as it has happened in many parts of thofe mountains, where rubbish is really carried down." 2dly, In the lower outlets of the icy valleys, the water comes out of the ice in the fame manner as fome celebrated ftreams, Arethusa, Vauclufe, and others, come out at once from under fome rock or hillock; that water has no open channel, till it has cleared the ice, and being firft filtered through its crevices, it never brings out any other materials than coarfe fand: furely, the immenfe quantity of materials miffing in the upper parts, cannot have been carried away through fuch channels. 3dly, When those waters, being united in the first lower valleys, begin to form torrents, they often meet with narrow cuts, where they ftill undergo repeated falls between broken rocks; and thefe are the only paffages through which any water can have come out of the fame extent of high grounds, ever fince the exiftence of our continents: now, if the materials miffing in the upper valleys had been carried away by waters, that immenfe quantity of rubbish would have either ftopped or widened thofe paffages, and reduced the whole length
of the channel to an equal declivity. Laftly, If it were objected, that the rubbish has been carried down by degrees to wider places, we should then come to a decifive proof of the contrary, from a fact which I have ftated in my former letter; many hollow places, now lakes, are pervaded by fome of thofe accumulated waters ever fince they ran; there the whole quantity of the rubbish which they have propelled, has remained, and it amounts to nothing, compared with the vacancies above.
9. I have begun this particular furvey of our continents, by diftinct and well known parts of the great scene of ruin and devastation exhibited in the Alps; not on account of their great vacancies between eminences compofed of broken and mouldering ftrata, which is a common phenomenon on the furface of our continents; but because of the peremptory proofs which we have in those parts, that running waters have had no share in the ruinous state of our mountains; and that confequently their chafms exifted, from the beginning of the prefent land, which was before in the bottom of the fea; and now I fhall give you a fimilar demonftration, in refpect of abrupt eminences.
10. None of the deeply diffected tops of the immenfe ridge. of the Alps, can be affected by any water, except that of immediate rain or thaw of fnow, which, trickling down the rifing grounds in a thousand rills, never unites on them in any stream capable of disturbing large or weighty materials; and confequently, the operations of the various caufes defigned by the collective word weather, may be obferved there unmixed with any fenfible effect arifing from the impulse of running waters. Now, Sir, thofe immenfe obelifks, which no continental caufe can have produced, are as fhattered as any part of the valleys where torrents are raging; and the only alteration produced on them by the weather, an alteration which ftill continues at a great rate, is that of foftening their abrupt furfaces, without any fenfible loss of their materials, which accumulate round the fteep grounds whence they fall.
11. When a long continued inattention to certain objects of nature, has rendered man infenfible to them, he commonly remains fo, till fome object of the fame clafs, but of a great magnitude, roufes his attention. Our foft vales, their rich meadows, their rifing grounds covered with verdure up to picturesque rocks, have been in all ages attracting fpots for men ; there were the firft fettlements, and there till the traveller flackens his pace: but we do not expect to receive any important inftruction from thofe objects, and not being confulted, they remain filent. If the decaying ornaments of the bordering hills, thofe racks boldly projecting with endangered trees over them, excite fome degree of aftonishment, it is foon diffipated by the vague idea, that time paft has no bounds; and if fome APP. REV. VOL. III. attention
attention is given to caufes, without which, time effects nothing, the innoxious ftream, meandering in the vale, is charged with devaftations, from which the vale itfelf is fuppofed to have proceeded: nothing, in that curfory manner of ftudying nature, ftops the fpirit of fyftem; the fpace is wide open before the prefumed thief; and his accomplice, as receiver of the boundlefs fucceffion of thefts, is no less than the ocean:—but in the great ridges of mountains, there are immenfe excavations, bordered alfo by ruin-like eminences; and we are abfolutely fure, that the materials miffing in thofe valleys, have not been carried into the occan.-Here imagination is stopped, and the aftonishment of reafon begins.-I fhall now fuppose, that some attentive men, roufed by that first fact, and conceiving great doubts on what has been maintained by fome geologifts on the operations of running waters, is refolved to obferve for himfelf.
12. Our obferver comes first into one of thofe vales, fo numerous on our continents, where rapid flopes, covered with verdure and furmounted by cbrupt rocks, are the winding borders of a space, the bottom of which is levelled and pervaded by a clear stream. Nothing in that quiet fcene raises the idea of devaftation; but our obferver knows, that the now pacific water, fometimes fwells, becomes turbid, overflows the meadows, and that, in fome of its floods, it has produced great havock in the neighbouring grounds; and as this is the caufe referred to by fome geologifts, he will not form any judgment on its effects, till he has fome opportunity to fee it at work. This may happen in autumn, when all the furrounding grounds having been foaked by a long continuance of heavy rain, the flood is greater than ufual: rapid and turbid torrents rufh out from all fides; the clear river is changed into a muddy pool, which covers the bottom of the vale; and trees carried down by the stream, are figns of a violent attack on fome parts of the neighbouring grounds.
13. Thofe unwelcome changes of fcene may have lodged in many minds a prejudice which they might remove: nobody is fond of going in queft of knowlege, during fuch an inaufpicious state of the elements: but our obferver is refolute; and notwithstanding the inclemency of the weather, and the badness of the roads, he approaches the fcene, where the wet and weakened grounds are attacked by the raging waters. In going up the main inundation he meets with muddy torrents, rufhing from recefles of the vale; and there being ftopped, he climbs by the fides of those waters, in order to examine their operations, and to find a paflage higher up. There he firft obferves, that thofe fwoln rills are only made turbid, because their channels are ftill too narrow for the quantity of water gathered in them: for, the fides of the fort of trough in which thole channels confift, are
Ropes, formed of loofe materials fallen from the abrupt incumbent rocks; and the unufual bulk of the rapid water which now paffes in that trough, caufes the bafe of thofe flopes to be attacked, and fome of their materials to be carried away. There alfo he obferves, that all the trees now ftanding on the upper parts of thofe flopes, muft tumble down fucceffively for the loofe grounds on which they have grown are undermined; and the steep fections of thofe grounds, though out of the reach of the torrents, are gradually demolished by the weather; thereby forming new flapes under thofe which are now decaying. It is efpecially from thofe attacks of the water on loofe grounds, that it is made turbid; but at the fame time he obferves, that all the gravel fo torn, fubfides as foon as the water comes to wider and lefs inclined parts of the channel, and that meer duft is carried down into the main flood. Laftly, In fome widened parts of thofe channels, he obferves, that the new flopes formed under the ruinous ones, are, even in that extraordinary weather, out of the reach of the torrents; and he may judge, that, when every other part of the bottom of those troughs fhall be made wide enough to contain the fame quantity of water in a fixed bed, the flopes, covered again with verdure, will remain unimpaired. Thefe fide torrents are the feeders of the main flood below, and the fame operations take place along the course of every one of them, up to the remoteft rill, which is then alfo become a torrent.
14. Our obferver has now entered on a diftinct field; or what I fhall call hereafter, a distinct fyftem of grounds; in which he is fure, that, ever fince the origin of our continents, all the rain-water that has not immediately funk into the foil, must have followed the fame courfe which it now purfues. He knows every part of that fet of grounds where the rain-water, by gently following oppofite declivities, divides itself between that fyftem and the next grounds which feed other Rivers, without any power of altering their original boundaries; and thence he traces in his mind, the first gathered rills, the forms of their various channels, the places of their meeting, many spots where they fall abruptly, and many where they abate their courfe. Comparing, then, what he has now obferved of the effects of a heavy and lafting rain in that area, with its effects on other high grounds of equal extent, but whofe declivities are regular and fmooth, he is ftruck with the idea, that the first small rills produced by the first rain which fell on his fyftem, could not have gathered, fo as to form thofe diftinét Streams which he has obferved, if that area had not previously been interfected by deep furrows trending to a lower place: for, rain-water, the fource of all our continental waters, has not the power of driving heavy materials, till it has acquired bulk and velocity;
velocity; and being once fettled in a channel, it cannot have any materials to drive along, except what may fall in its way. Now, the first of thofe circumstances must arife from previously wide and deep interfection of the ground, which alfo must have a great declivity; and the laft can only proceed from originally abrupt and decaying fides of thofe excavations. Thence the prefent regular ftate of fo many high grounds, which, though loofe, are not interfected by chafms on any of their declivities: their furface was originally even, and the firft fmall rills of the rain-water, remaining conftantly feparate on that furface, have never acquired the power of digging dales and vales bordered with fteep fides. Such is the firft general confequence derived by our obferver, both from his prefent remarks, and from all the facts which they recall to his mind; and on that previous point, he concludes finally, that attributing the deep channels which interfect his fyftem of grounds, to the waters which are now feen pervading it, would be, taking for the effect of streams, the very cause of almost every diftinct stream on our continents from their beginning; namely, original hollow tracks.
15. A first fettled point in fuch inquiries, is a first step that may lead farther. Our obferver now intends to examine, what has been the real effect of running-waters, for altering the origi nal form of his fyftem; and in that inquiry he firft compares the fides of the vale with its lower ground. The inundation which he has obferved, notwithstanding its excefs, did not reach the flopes of loofe materials, formed on the fides of that vale, under the vertical fections of the upper grounds; confequently, the fireams cannot have had any thare in the form of thofe fides; they were originally fteep and crumbling, and their rubbifh has fucceffively formed thofe fpes now covered with verdure-but fince thofe fides were originally abrupt, it is not in the nature of things, that they could then inclofe an horizontal ground: fuch a chafm was to have an irregular bottom, and must have extended below the prefent level; confequently, that horizontal ground, extending from hill to hill in the bottom of the vale, must confift of loofe materials carried down by the fide-torrents. When our obferver forms that conjecture, the fream is confined in its ufual bed, and much reduced by long dry weather from that circumstance, a deep fection of the ground is left uncovered on the banks of the Aream, and there his conjecture is confirmed; for the upper part of that ground is meer fand, and the fragments of the fiony ftrata which compete the neighbouring hills, are feen in the loweft parts of the fection.
16. That fucceffion in the fediments compofing the horizontal ground of the vale, points out to our obferver a fort of chronometer; by comparing that fucceflive work of the freams,