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With the exception of platina, mercury, molybdena, and the five bodies so little known and apparently so little useful, tellus reum, tantalium, colunibium, and cerium, Cornwall affords indications of all the metals.
On the whole, this paper, though with some defects as a mix neral survey, contains a great deal of valuable information, and manifests in the author much diligence and research. We cannot help thinking, that the Wernerian geology is faulty, in directing the attention of the mineral surveyor to some favourite points, and withdrawing it from the rest. The order in which the strata succeed, seems to be the great ohject to which the mineralogists of that school are inclined to attend; and the order fixed on by Werner being very precise and very different, we imagine, from that which nature has adopted, the person who would reconcile the one with the other has abundance of work upon his hands. The junction of the rocks with one another, particularly of the stratified with the unstratified, their inclination to the horizon, the line in which they intersect it, the space which strata of a particular kind occupy, and the heights to which they ascend, --these, as well as the mineralogical characters, ought to be diligently examined.
The use Dr B. has made of the barometer, we think extremely laudable; and we hope, that an instrument, calculated to give such valuable information, not only concerning the mountains themselves, but the position of particular minerals, will, by and by, be considered as an essential part of a geological apparatus. The compass for measuring the bearings of the strata, and the dinometer * for estimating their dip, are still more important and we regret to find them so rarely employed in the present survey. A map of Cornwall, with the points marked where par, ticular observations were made, would have added much to the value of this communication.
Dr Berger, as a foreigner, has a claim to indulgence ;-and being, perhaps, not quite familiar with our language, he might, when his knowledge depended on the information of others, be occasionally deceived. It adds much to the value of his obser vations, that his eye has been accustomed to the sight of rocks and of mountains, where they appear on the greatest scale, and in their noblest forms. He has been trained to the sci ence he pursues, among the Alps of Switzerland; and, born in a land of liberty and independence, he has taken refuge in the
only * A very ingenious instrument, contrived by the Right Honourable - Lord Webb Seymour, for measuring at opçe both the inclination and the bearing of any stratum,
only country where they now exist ;-and where he hopes that the girdle of the ocean, and the spirit of the people, are a security against that oppression which the bulwark of his native mountains was unable to resist.
A very interesting paper on the mineralogy of Shropshire, by Arthur Aikin esq., is the eighth in this collection.
It seems that a vertical section through the Wrekin, in the direction of west by north, and east by south, intersects the great coal field of Shropshire, on the east side of the mountain, and two smaller formations of the same mineral on the west. The former lyes between the base of the Wrekin, and a branch of the old red sandstone; which, proceeding southwards from the great body of that rock, which occupies so large a portion of Cheshire and the country to the north, divides the coal fields of Shropshire and Staffordshire from one another. Against this sandstone, the coal field first mentioned seems to abut, on the east side, dipping towards it at an angle of about 6o. Under the coal lyes a body of limestone strata, dipping also toward the red sandstone.
The coal formation is composed of the usual series of rocks, which are most completely seen at the Madeley coalery, where a pit is sunk to the depth of 729 feet, through 86 beds, which compose the whole of the formation.
The first 30 strata are composed of sandstone, fine grained, with mica, and thin plates of coal.' The 31st and 33d are coarse grained sandstone, remarkable for being penetrated by petroleum. They are together 15 feet thick, with a bed of sandy slate clay, 4 feet thick, interposed between them. These are what furnish the petroleum spring at Coalport.
The first coal forms the 9th bed from the surface, at the depth of 102 feet, and is not more than 4 inches thick. The first bed that is worked, is a five feet coal, at the depth of 490 feet, But the greatest deposit of coal is lower down, consisting of 9 beds, the aggregate thickness of which is about 16 feet. The rock upon which the coal formation rests, is for the most part limestone, which is nearly horizontal at the eastern extremity of the above section, but rises, with a considerable elevation, as it approaches the high country about the Wrekin. There are two fractures in these beds, that run parallel to one another; and on the west side of them the limestone beds are more eleyated that on the east. It would seem, from Mr Aikin's description, that there is no decisive character contained in the rocks themselves, by which it can be determined whether this is to be ascribed to the forcible elevation of the strata at one end, or their depression at the other. There is another range of limestone, farther to
the west, and parallel to the former. It is very full of tubulites, and other coralline remains. In this limestone, the elevated portion has an intimate connexion with an unstratified greenstone, which lyes under it, at the point where it is most elevated.
An important geological question here occurs. Are these beds, or are they not, in the position in which they were first deposited ? That they are not in that position, appears to be supported by the impossibility of a bed of sandstone being deposited on a plane at an elevation of between 30° and 40°, in such a manner as to constitute an extensive stratum of an uniform thickness. The position, also, of the tubulites, which pierce through the marl, is a subsidiary argument of no small weight. These tubes, some of which are scarce an eighth of an inch in diameter, with a length of twelve inches, are perpendicular to the plane of the stratum ; and therefore, when that plane makes an angle of 40° with the horizon, the coralline tubes must make with it an angle of 50°, a situation not at all agreeable to the class of animals to which they belong, as they always affect a vertical position. It remains to discover, whether, in this body of rock, the elevation of one end, or the depression of the other, is most probable. The former supposition seems to derive great probability from this, that where the beds of limestone and sandstone are most elevated, a great mass of greenstone lyes immediately under them. • Is it not, therefore, probable, says Mr Aikin, that the greenstone has occupied the situation · which it now holds, posteriorly to the formation of the strati
fied rocks between which it is at present found? But though • the above facts,' adds he, should be considered as justifying
the hypothesis of the active agency of the greenstone, and consequently its fluidity, I am by no means prepared to affirm
that this fluidity was that of igneous fusion; for neither the o sandstone, nor the limestone, nor even the crumbling clayey
marl, appear to me to have undergone the smallest alteration • by the contact, or close vicinity of the greenstone.
The section, as it proceeds to the westward, encounters the grauwacke, elevated towards the north-west, at an angle of 50°; over which lye the strata of red sandstone, elevated at an angle of 10° towards the north-east. These two kinds of strata, there fore, make with one another an angle which it would require a trigonometrical calculation to determine, from the data which Mr Aikin has given, but which may be nearly taken at 59°; which, therefore, is the angle which the sandstone makes with the grauwacke. At Welbach, near the western extremity, is a patch of coal strata, contained in a hollow between the grauwacke
and the old red sandstone. On one side, therefore, this coal must be considered as resting immediately on a transition rock, from which, on the Wernerian system, it is represented as extremely distant. On the whole, we must consider this paper as drawn up with great care and impartiality; so that it is not easy say,
whether it be to the Plutonic or Neptunian system that the author most inclines. The only thing that can render a particular theory not only innocent but useful in the hands of an observer, is a disposition to mark, with equal diligence, the facts that are favourable, and those that are adverse to his
So far as one can discover from the present Memoir, Mr Aikin may be said to possess this degree of candour; and it is difficult, perhaps, to bestow on him a higher praise. We have seen proposals by the same gentleman, for a mineralogical sur-vey of the county of Salop; and, from the specimen given along with the proposals, as well as from that of which we have been just giving an account, we cannot but ardently wish for the success of his undertaking.
The next paper to which we shall advert, is by Leonard Horner, esq. ; and contains a very distinct, and apparently very accurate account of the Mineralogy of the Malvern : Hills; a ridge well known, in the south-west part of Worcestershire. The central part of this range, and nearly the whole of the eastern side, consist of different compounds of felspar, hornblende, quartz, and mica, disposed in very irregular forms. Granite is one of these compounds, and appears to be less rirregular than the rest. It is sometimesi found in the highest parts of the hills; but prevails chiefly in the lower parts, where it forms veins which traverse the other rocks.
The stratified rocks which occupy the country to the westward, rise to a considerable height on the side of the range. The - most northern hill in the range is called the End-hill
, and is composed of granite. : On the End-hill, also, but higher than the granite, there is a rock of a purplish brown colour, com
posed of hornblende and felspar, with a little quartz. It would probably be ranged, Mr Horner says, with the greenstone of Werner ; but we rather think with the svenite. On the north side of the same hill, á rock occurs, made up nearly of equal parts of hornblende and epidote.
The North-hill, near the former, and somewhat to the west of it, contains also granite. The Worcestershire Beacon is another of the most remarkable points in this range, and is an aggregate rock, consisting of small angular and rounded fragments of quartz and felspar, cemented by a ferruginous base. VOL. XIX. NO. 37,
At the top, this hill consists almost entirely of granite ; and on the eastern side, greenstone is the prevailing rock. The relative position of the different rocks is not, however, sufficiently explained ; and it may be, that the thick coat of vegetable mould by which the ridge is mostly covered, does not allow it to be ascertained.
The Swinet-hill is one of the most remarkable points in the Malvern chain ; and the upper part of it is composed of a granite, more distinctly characterised than the greater part of those found in this district. It is, however, very different from an alpine granite. The mica is in minute specks, and in very small quantity: The rock is not stratified. Thus it appears, that the ridge, or the highest points in the range, are composed of granite, and other unstratified rocks. On the west side strata occur ; some of coarse-grained sandstone, others of a compact quartz sandstone; one of these is said to be found in thin layers, with a bearing parallel to the direction of the range, but dipping towards the east, at an angle of about 60°. On this side, also, lower down, is a limestone ridge, that dips to the west, at an angle of about 40°. The strata, indeed, all along, seem to be in a very erect position. There are also argillaceous slaty strata, bearing north and south, with an elevation of 65° westward, or towards the Leadbury hills, a low ridge, which, at the distance of about two miles, runs parallel to the Malvern hills.
The direction of the stratified rocks is, with a few exceptions, parallel to that of the range; but there is great irregularity in the dip. The strata nearest the unstratified rocks dip at a considerable angle towards the west; though, in some places, they dip in an opposite direction, that is, toward the hill; and they were observed in this position at the greatest height to which they ascend.
I'he two sides of the Malvern ridge are in many respects considerably unlike. On the east side, a level plain extends for many miles; and the streams that rise on the sides of the ridge run directly eastward to the Severn. On the west side, there is a constant succession of hills; and the streams run, not at right angles to the ridge, but rather in the direction of it;-some to the south, and others to the north. The strata on the west side are considered by Mr Horner as belonging to the order of Transition rocks. The remarkable variations that occur in their direction and dip, make it probable that they have been forcibly elevated from the horizontal position in which they were originally deposited, and thrown into the different situations in which they are now found. We must remark of Mr