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Piffer, a work of equal ingenuity and curiosity, on which the proportional height of all the mountains comprehended in it from the present level of the lake of Lucerne is accurately delineated, and the mountains themselves composed of the very kind of rock which principally constitutes them. To a philosophical eye the inspection of this curious model is alone worth a journey to Lucerne.

To give examples, in the new continent, of similar appearances of former lakes no longer existing, it may not be amiss to quote some observations of Mr. Thomson, Secretary of Congress, on viewing the passage of the Potowmac river through the blue ridge forming one of the long valleys closed to the north and south between several parallel ridges of the Virginian mountains. They have been already transcribed by Dr. Hutton for a different purpose. The broken and rugged faces of the mountain on each side of the river; the bed of the river for several miles below, obstructed and filled with the loose stones carried from this mound; in short, every thing on which you cast your eye evidently demonstrates a disrupture and breach in the mountain, and that, before this happened, what is now a fruitful vale was formerly a great lake, which might have here formed a mighty cascade, or had its vent by the Susquehanna, where the blue ridge seems to terminate. Besides this, there are other parts of this country which bear evident traces of a like convulsion. From the best accounts ! have been able to obtain, the place where the Delaware now flows through the Kittatinny mountain, a continuation of what is called the North Ridge, was not its original course, but that its passage was through what is now called the Wind-gap, seyeral miles to the westward, and above an hundred feet higher than the present bed of the river. This Wind-gap is about a mile broad, and the stones in it such as seem to have been washed for ages by water running over them. Should this have been the case, there must have been a lake behind thåt mountain ; and, by some uncommon swell in the waters, or by some convulsion of nacure, the river must have opened its way through a different part of the mountain, and, meeting there with

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less obstruction, carried away with it the opposing mounds of earth, and deluged the country below with the immense collection of waters to which this new passage gave vent. There are still remaining, and are daily dilcovered, innumerable instances of such a deluge on both sides of the river, after it passed the hills above the falls of Trenton and reached the champaign. On the New Jersey fide, which is flatter than the Pennsylvania side, all the country below Croswick hills seems to have been overflowed to the distance of from ten 10 fifteen miles back from the river, and to have acquired a new soil by the earth and clay brought down and mixed with the native land. The spot on which Philadelphia stands evidently appears to be made ground. The different strata through which they pass in digging for water, the acorns, leaves, and sometimes branches, which are found above 20 feet below the surface, all seem to demonstrate this.

Dr. Hutton thinks this statement and view of things far from corroborating that sudden convulsion conjectured by the judicious observer from fo many concurring testimonies. His system requires him to reject all such ; and he here fees nothing but the rivers gradually excavating the several valleys between these parallel ridges, and conveying their spoils during an infinity of ages through these gaps to the sea. It is rather curious to find an author confidently quoting such apparent marks of a convulsion, either sudden or such as might be effected in no great length of time, as proofs of an infinitely now degradation. It seems he should at least have thewn the impossibility or improbability of lakes having once filled those valleys. But no; the author is himself convinced, and sees not the necessity of convincing others. Such is the very natural fascination of predetermined system. It is said that some small part of the rocks forming the fall of Niagara has lately tumbled in. The violence of such a stream rushing over them, and that corroding power of waters fo frequently the theme of Dr. Hutton, may certainly from time to time detach one fragment after another, and thus, in a few thousands instead of millions of years, level down this great barrier without occafioning any material damage in the sub

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jacent countries. Earthquakes have not been experienced for many years in those parts; but soon after the French first settled in Canada, very tremendous ones were felt. Dr. Hutton will then allow it possible, that an earthquake may even at once effectuate the destruction of the whole mound which now sustains lake Erie. It is devoutly to be hoped that such catastrophe may not take place, as in that case lake Ontario and the river St. Lawrence would be so swelled as to overflow all the countries around them, to the probable destruction of their now numerous inhabitants. But {hould this head be, either gradually in the course of many centuries, or by convulsion at once, suddenly disrupted, it is evident that the lake above it, and all the great western lakes communicating with it, would be successively or instantly drained either of the whole or of great part of their waters.

Their beds would then exhibit either much diminished lakes, or valleys, in a short time not unfruitful, traversed by one or more rivers. ln a certain term of years, no other natural proofs would remain of the existence of former lakes than such traces as are now discoverable in the paffages of the Potowmac and Delaware rivers, and in the countries below them. Such surely may be the very natural fate of every lake suspended high above the general level, without the necessary intervention of millions of

years. In times inmediately subsequent to the deluge, when all nature was yet in the full paroxysm of convulsion, it is more than probable that such unrecorded accidents did happen ; and to such many actual appear. ances must be referred.

(lb) Page 372. From the observations I have made, particularly on the ascents of Mount Jura from Franche Comté, the basons of many formerly-existing lakes are very likely to have been frequently mistaken for the remnants of volcanos by those philosophers who, prepoffeffed with the idea of finding every where their traces, have without hesitation adopted them as the craters of antient eruptions. Extensive level plains, although in a circular form, furrounded by moderatę eminences broken down in one part only, and that always towards the descent, present, however, very different aspects from the mouths of volcanos. On this ascent of Mount Jura many of these' of various extent, but less spacious towards the summit, are to be reInarked one above another. The breaking down of the mounds of one of these uppermof lakes would necessarily occasion the rupture of all the lower reservoirs thus suddenly overcharged, nearly, as it appears to have happened, in the same direction. I do not know that there are any volcanic appearances on the fides of these basons; but, if there were, it would not exclude their formerly being filled with water, which their remarkably level bortoms without any tunnel-like appearance clearly indicate. In the neighbourhood of so much water favourable to the kindling of volcanic fires, earthquakes may have contributed to break down their banks. That asliftance seems, however, neither neceffary nor probable, from the above. mentioned similar direction of the ruptures. These delightful oval or circular meadows, encircled by Noping banks covered with wood, repeated at various stages, form the most beautiful and pleasing variety I ever beheld. I have no doubt but many such emptied basons of former lakes, very natural to have existed after a general inundation, and to have difappeared from the consequences of various accidents at various' times, are frequently taken for volcanic craters by those who have adopted the fystein of formation by fire. The attribution of many of these to water excludes not, however, frequent and undoubted indications of volcanic fires. The multiplicity of waters in the early periods succeeding the deluge inake these but the more probable, and both are likely to have then exifted in countries where neither lakes nor volcanos now remain.

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(cc) Page 3734 Mr. Monnet in his Mineralogy assures us, that a great cavity filled with water, when a certain gallery in the mines of Sainte Marie aux Mines in 'Alsace was abandoned, was found, after 50 years when that gallery was again opened, filled with transparent quartz. As Mr. de Buffon informs us, there is a species of earth on the Pharos of Messina which petri3 H

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fies with astonishing rapidity. To form it into mill-stones, no other opera tion is necessary but, after having cleared away about two feet of soil, com kneed the under-stratum and form it into the shape required, and then cover it loofely again with the fume foil. In a year's time the mill-stone is found perfectly hardened. The hardness of coble and pebble stones occae fions them to be generally looked upon as stones of very antient petrification: this is, however, often not the case. In the dried bed of a torrent in Italy, I reinember to have gathered in a fhort time, as I walked along it, a number of specimens of pebbles of very different degrees of hardness and formation from that which still received the impression of the finger, or easily crumbled when pressed, to that degree which furpasses the hardness of most other kinds of stones. These new-moulded pebbles, frequently interfected by veins of different colours, perfectly resembled others in the completest degree of induration. Clays, thus rounded and gradually hardened, are easily to be found in the bed of every torrent exposed to be sometimes filled with waters, and at other times laid dry. The petrifying qualities of many waters are too well known to be insisted upon. One instance of the abundance and minuteness of stony particles contained in waters, and of the celerity with which they superinduce a stony incrustation, is worthy to be recorded. It is mentioned by Mr. Dietrich, the late philosophic mayor of Strasburg, and inserted by Mr. de Buffon in his Natural History of Minerals. By the ingenious management of the waters of Santo Filppo on the mountain Santa Fiora near Sienna, Doctor Leonardo Vegni has contrived, to take off the impression of medals and bassi relievi, by incrustation ; even casts have been taken from buftos, and he hopes at length to be able to take off whole statues. Any porous substances may be impregnated both inwardly and outwardly with these sediments ; and if the animal or vegetable substance which serves as a mould should decay, the remaining concretion will appear a true petrification of the body itself, though it has really been only incrusted, interiorly as well as exteriorly. If woods or shells are thrown into these quickly-accumulating concretions, they will be as completely petrified within them, as we sometimes find such sub

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