ces strewed with slippery and cutting fragments mark the mountains of common slate, so have the grauwacke rocks peculiarities by which they are recognised, and which are no where more evident than in the rounded summits that embosom Derwentwater, as represented in the annexed cut. In their forms, tints, and outlines, there is something

indescribably delightful, and they present that rare union of the sublime and beautiful, of which no better idea can be formed, than that suggested by Mr. Burke's comparison : "Sublime objects are vast in their dimensions; beautiful ones comparatively small; beauty should be smooth and polished; the great, rugged and negligent; beauty should shun the right line, yet deviate from it insensibly; the great, in many cases loves the right line, and when it deviates, it often makes a strong deviation; beauty should not be obscure; the great ought to be dark and gloomy; beauty should be light and delicate; the great ought to be solid and even massive." These qualities of that which is sublime, well apply to the rocks I have before described, and, when blended with the parallel definition of the beautiful, furnish a just notion of the aspect of those now under consideration.

2094. The varieties of MOUNTAIN LIMESTONE (the TRANSITION LIMESTONES of the Wernerians) are the substances that next occur. They are frequently seen immediately incumbent upon clay-slate, and are further distinguished from primitive limestone, or statuary marble, by having a less decidedly crystalline texture. Where this rock lies directly upon slate, it contains few organic remains; but where red sandstone is interposed between it and the slate-rocks, or in proportion as it is distant from the primary and slate-rocks, the relics of organization become more frequent. It then abounds in remains of corals and zoophytes, which now are not known to exist. It often is traversed by veins of calcareous spar, and presents a great variety of colours. It is abundant in Devonshire, South Wales, Derbyshire, and Yorkshire. At Plymouth this rock is seen immediately incumbent upon slate, in a quarry between the Dock and the Town. Its colours are red and grey, streaked with white crystalline veins. It is also seen to great perfection in the Breakwater quarries at Oreston.

2095. Slate districts often present very curious inflexions and incurvations of their strata. The slate at Plymouth, and the grauwacke of Clovelly in the north of Devon, and the killas upon the coast of Cornwall near Charlestown, are in many places very singularly contorted; and sometimes small undulations present themselves in the laminæ, exactly resembling those left by the ebbing tide upon a gently reclining sand-bank. These appearances may, perhaps, be referred to the action of water upon the materials before they were consolidated.

2096. Limestone strata are also very remarkable for the inflexions and curvatures, referred, not very satisfactorily, by Dr. Hutton to their having been in a soft state at the time they were disturbed from their horizontal position. There are some very curious instances of these curvatures noticed by Saussure; one, in particular, on the road from Geneva to Chamouny, where the small stream of Nant D'Arpenay forms a cascade by falling over a perpendicular surface of limestone rock; the strata are bent into regular arches, with the concavity to the left; while in another neighbouring mountain they turn to the right; so that a verticle section of the two would present the figure of S. The top of Benlawers in Perthshire, and the coast of Berwickshire, with many other districts in Scotland, present instances of these singular contortions. Dr. Hutton has given a plate of the bent strata in Berwickshire, from a drawing made by Sir James Hall. I cannot here follow Dr. Hutton and his sagacious commentator through their arguments founded upon these phænomena, they attempt to prove that the undulated strata have received their peculiarities upon level ground; that they have then been elevated, hardened, and often bent and contorted during these processes; and that their irregularities as to position, and their fractures and dislocations have thus occured, and do not result, as the opposite school would have it, from the falling in of caverns, a position which they assume as at once accounting for such appearances, and for the retreat of the ocean. Hutton considers the land to have been raised, Werner supposes the waters to have retreated

2097. The aspect of a country of mountain limestone is peculiar, and generally extremely picturesque. The hills, which, in this country at least, are not very lofty, abound in precipices, caverns, and chasms; and, when upon the coast, form small promontories, and jut out in low but grotesque pillars. The even surfaces are covered with a stinted turf, but the rifts and cracks contain often a soft rich soil in which stately timber trees flourish. The chasms of limestone rocks are often filled with a fine clay, which has, perhaps, sometimes been derived from the decomposition of shaly strata, or sometimes deposited from other causes in the fissures, and the singularities of aspect, and much of the beauty of this rock, is referable to these peculiarities. Thus, upon the banks of the Wye, large and luxuriant trees grace the abrupt precipices, and jut forth from what appears a solid rock. Their roots are firmly attached in some crevice filled with a favourable soil. Sometimes rivers force their way through the chasms; at other times they are empty, and the roofs ornamented by nature's hand with ncretions of white and glistening spar, which seem like

the rewed sculpture of Gothic architecture.

The views of Dovedale, and of Matlock and its vicinity; and the caves of Castleton, are admirably illustrative of the scenery of mountain limestone. Pont-Neath Vaughn, in Glamorganshire, is full of its beauties; and the panorama of Swansea Bay, seen from the Mumbles Point, furnishes a pleasing, characteristic, and perhaps unrivalled, prospect of these rocks.

The banks of the Avon too, in the vicinity of Chepstow, are of mountain limestone. The rock is there impregnated with bitumen, and hence exhales a peculiar and fetid odour when submitted to the blows of the axe or hammer. This is by no means uncommonly the case where the limestone rock, as in the present instance, is in the vicinity of coal. The following sketch may serve to give some idea of the appearance of the mountain limestone of Dovedale, in Derbyshire.

2098. Mountain limestone is an excellent material for building, and many of its varieties are sufficiently indurated to receive a good polish, and are thus employed for ornamental purposes, being cut into vases, chimney-pieces, and the like. Where they abound in corals, and other organic remains, these frequently add to their beauty.

The colours of transition limestone are various, but its essential constituent part is always carbonate of lime. The black variety known under the name of Lucullite*, or black marble, has long been admired, and is often tastefully manufactured and ornamented by etching upon its surface. It is found in Derbyshire, Sutherlandshire, and Galloway, and appears to derive its colour from carbonaceous matter.

All these limestones are converted into a more or less pure quick lime by the operation of a red heat, and are thus often valuable as affording manures, and for other purposes.

2099. The next rock that occurs in point of succession, is RED SANDSTONE. It often rests upon slate, and then, from its position has

* A name given to the marble in consequence of the admiration bestowed upon it by Lucius Lucullus. Vide Plinii Hist. Nat., 36. 8.

acquired the term of old red sandstone. But a similar substance, or nearly so, also is found lying upon mountain limestone, in which case it has been called red marl, or new red sandstone.

Entering upon this substance, we come upon distinctly stratified ground; it is very abundant in England, especially in Lancashire, Cheshire, Staffordshire, Shropshire, and Worcestershire; and indepen dent of its embowelled treasures, for it is connected with coal and rock salt, its surface is generally favourable to vegetation, and its soil sufficiently luxuriant. It consists principally of siliceous particles, and oxide of iron, with some argillaceous earth, and more or less calcareous matter. Its beds are often of great thickness, as may be seen in the quarries; it is much used as a building stone, but moulders in consequence of the action of air and moisture upon the oxide of iron. It often contains particles of mica, and fragments and pebbles of old rocks. 3000. Red sandstone rocks are seen in some parts of Britain in great beauty and perfection, especially where they occur on the coast, or are intersected by rivers. At Ilfracomb, the old red sandstone of the Somersetshire coast is seen lying upon slate; and the junction is interesting to the geologist, the sandstone becoming somewhat slaty, and the slate having a tendency to a granular fracture. The following sketch of Hawthornden, near Edinburgh, shows the characteristic features of the red marl rock, or newer red sandstone; and the ancient castle, with its dungeons and vaults, is constructed of this material. Ridges

of red sandstone, containing mica and fragments, sometimes accompany primary rocks, of which a very singular instance occurs upon the banks of Loch-Beauly, near Inverness; a high range of granite is there bordered by a breccia, very like that of the bed of the Fyers; and a low ridge of red sandstone, of which the valley is also composed, accompanies the series, and seems the detritus of the more ancient and lofty formations.

3001. The slates, grauwackes, and limestones, are in this country the principal seats of the metallic ores; and they form scenery which,

gradually decreasing in grandeur and sublimity, increases in softness, variety, and luxuriance. In the lowest sandstone formation, we meet with a variety of bodies of the utmost importance in our arts and manufactures.

3002. A substance which occurs in abundance in many parts of the red strata, is gypsum or sulphate of lime, known also under the name of plaster-stone, selenite, and alabaster. Near Tutbury in Staffordshire, and near Nottingham, it is found in blocks and veins; and lately a variety, new in England, has been found, called Anhydrite. These minerals constitute valuable materials for the ornamental manufactures of Derbyshire.

3003. In the county of Cheshire the red sandstone contains immense beds of common salt, most abundant in the valley of the Weaver, and near Middlewich, Northwich, and Nantwich; it is accompanied by gyp

sum.

The first stratum was discovered about 150 years ago, in searching for coal. It begins about 30 yards from the surface, and is 25 yards thick; below this, and separated from it by 10 or 12 yards of indurated clay, is another bed of salt, the extent of which is unknown; in many places it is nearly pure, in others tinged with oxide of iron and clay. This pit is at Northwich; and at other places there are very abundant brine springs. A most remarkable circumstance in the Northwich mine is the arrangment of the salt, giving rise to an appearance something like a mosaic roof and pavement, where it has been horizontally cut. The salt is compact, but it is arranged in rounded masses, five or six feet in diameter, not truly spherical, but each compressed by those that surround it, so as to have the shape of an irregular polyedron. The Wernerians regard the salt as having merely crystallized here from its aqueous solutions; the Huttonians consider the water to have been evaporated by heat. The large pit at Northwich presents a very singular spectacle when duly illuminated; it is a circle of nearly two miles in circumference, the roof is supported by massive pillars of salt, and the effect is heightened by the variety of colours it presents*.

3004. Coal is the most important product of these middle strata. What is called a coal field, or district, or sometimes a coal basin, may be regarded as a concavity, varying greatly in extent, from a few to many miles, and containing numerous strata or seams of coal of very various thickness, alternating with sandstone, clays, and soft slate or shale containing impressions of vegetables and sometimes the remains of fresh water shell-fish. The parallelism of these strata is generally well preserved. The whole arrangement is seldom any where quite horizontal, and never vertical, but almost always more or less inclined. Beneath each stratum of coal, there is often one of soft clay, or clunch, which rarely contains the organic remains of the overlying shale: and although the alternating strata of coal be very numerous, it is seldom that more than three or four will afford profitable occupation to the miner. The upper seam is commonly broken and impure, and few beds, less than two or three feet in thickness, are followed down to any conconsiderable depth. The depth of the mines will of course greatly vary, according to the inclination of the strata, the time they have been