in length, and varies in width from four to seven miles. It contains the thickest bed of coal in Great Britain. (See page 105.) There is a narrow coal-field on the north-eastern border of Wales, extending from Mostyn in Flintshire, to Chirk in Denbighshire. There are also a few smaller coal-fields on the north-eastern side of Herefordshire, which extend into Shropshire. The Clee Hills, near Ludlow, contain, on their sides, two or three small detached coal basins. The summits of these lofty hills are capped with basalt.

The coal basin of the Forest of Dean, is the next considerable repository of coal: it presents, perhaps, the most perfect model of a coal basin of any in Great Britain; the coal strata occupy a space of about ten miles in length, and six in breadth: the millstone grit and the transition limestone on which they lie, may be distinctly observed cropping out, on its northern and western boundary.

In Somersetshire and Gloucestershire there is a considerable coalfield on each side of the river Avon its greatest extent is about twenty miles, and its greatest ascertained breadth about eleven miles; but it is covered in many parts by the secondary strata, consisting of red marl and lias. The deepest coal mine in England is in this coalfield; the depth of the pit at Redstock, near Bath, being 409 yards.

The greatest repository of coal in our island is that which extends on the northern side of the Bristol Channel, 100 miles in length, and varying in breadth from five to twenty miles. Further information respecting many of the English coal-fields will be found in Chap.VIII.

A considerable part of the middle district (coloured green in the map), which is not occupied by the coal formations above enumerated, is covered by the red marl and sandstone, described in Chap. XI. As the sandstone of this formation often covers the coal strata, it becomes an object of great interest to landed proprietors in the midland counties, who have estates at no great distance from the coal districts, to ascertain whether coal may not extend under the red marl and sandstone. Some observations on this subject are given (pages 121 and 122), which the author is persuaded deserve the attention of landed proprietors. The search for coal under the red marl and sandstone in Somersetshire has been eminently successful; and coal has in some instances been found, by sinking through both lias and red sandstone.

The principal repositories of rock salt, and the strongest springs of brine, are situated in the red marl of Cheshire, and near Droitwitch, in Worcestershire. (See p. 172.) In this formation the principal beds of gypsum are found: it is frequently associated with rock salt. (See Chap. XI.)

One of the most remarkable features of the middle district, is the occasional occurrence of various rocks (in situ) of granite, slate, and sienite, belonging to the class of primary or transition rocks: they rise through the secondary strata, and appear, from various circumstances, to have once occupied a considerable portion of the midland counties, extending from Leicestershire to Warwickshire, Worcestershire, Gloucestershire, Somersetshire, and Devonshire. The secondary strata of England, from lias to chalk (coloured yellow in the map), are pretty fully described in Chaps. XII., XIII, and XIV. The more recent or tertiary strata (coloured brown in the map, and marked 22),

are described in Chaps. XVI. and XVII. The basalt dyke of Cleveland, which runs through the North Riding of Yorkshire into Durham, is described, with other basaltic rocks in England, in Chap. IX., and the alluvial beds, marked 1 1 1, are described in Chap. XXI. A description of many of the mining districts of England and Wales will be found in the chapter on metallic veins.

It now remains to notice the sections in different parts of England. A seetion, to possess much value, should be made as nearly as possible along the true line of the dip and rise of the strata. We possess no true line of dip in England, which passes through all the different classes of rock; and it is only misleading the reader, to represent the succession of rocks out of their true situation. The section of the secondary strata, with a small portion of the tertiary, given at page 160, represents the succession of the different secondary formations, from chalk to the lowest new red sandstone, taken in a line from the chalk hills north-west of London, to the transition rocks south of the Malvern Hills, in Herefordshire. But in this line, the lower red sandstone, and magnesian limestone are wanting.

If we draw another line across England, through Durham and Cumberland, from the German Ocean, near Sunderland, to the Irish Channel, (see section, Plate VII.) we may observe the magnesian limestone a forms the uppermost rock of the series; all the secondary strata above this formation are here wanting; it is, however, probable that they may once have extended into the German Ocean, in the order represented at page 160. The magnesian limestone A lies unconformably upon the coal strata, which rise to the west B B; at x the strata are broken by the Burtreeford Basalt Dyke. cc represents the lower beds of the coal strata, with mountain limestone; they terminate at the mountain called Cross Fell, 5. The lower part of this mountain is composed of mountain limestone and greywacke; a little to the west, the beds are broken, by nearly vertical beds of trap and sienite. In the Vale of Eden is Penrith Beacon, 4. This vale is covered by beds of conglomerate and red sandstone. The lofty mountains, ɛ E, that surround the lakes of Cumberland and Westmoreland, are skirted by beds of mountain limestone; but the higher mountains are chiefly composed of slate, felspar, porphyry, and greywacke. Granite occurs at the base of Skiddaw and Saddleback, and at Coldback Fell. 1, is Sea Fell, the highest mountain in this group; 2, Skiddaw; and 3, Helvellyn. Farther west we come upon the coal strata of Whitehaven, dipping west, and covered by unconformable secondary strata. Some of the more remarkable rocks in the mountains round the lakes

are described in Chap. VII. Plate II. fig. 4, represents the arrangement of the strata in the central part of England, passing in a line nearly east and west, through the low granite range at Charnwood Forest, in Leicestershire: e, on the right-hand side of the plate, represents lias resting on red marl and sandstone, a. The granite and slate rocks are represented, b b c c, partly covered by horizontal beds of red marl and sandstone: d d are the coal strata, near Whitwick, much elevated as they approach the Forest Hills. A little out of the line of section, are represented the elevated beds of mountain limestone at Breedon and Clouds Hill, part of which limestone is contin

ued to the Forest Hills at Grace Dieu. For a more particular account of this section, see Chaps. X. and XXII.; and for an account of the sections near Dudley, in Staffordshire, see Chap. VII.

This brief sketch of the geology of England, with the references to the map, sections, and chapters in this volume, may suffice to give the reader a general view of the geology of England, and the situation of its principal mineral repositories. I shall subjoin an account of the thermal waters of England, and of a few celebrated thermal waters on the Continent, and a table of the height of mountains.

Height of some of the most remarkable Mountains and Hills in England and Wales.

ON THE THERMAL WATERS OF THE ALPS.

THIS paper was published by the Author in the "Philosophical Magazine and Annals," January 1827; and a nearly similar account was given in his "Travels in the Tarentaise," in 1823. The thermal waters of the Alps had before been regarded as merely local and unconnected phenomena, scarcely deserving the notice of geologists.

When we approach a range of lofty mountains, like that of the Pennine Alps, and observe the calcareous strata on the outer part of the range, bent and contorted in various directions; when we further observe beds of limestone and pudding-stone alternating and placed in an elevated position, as we advance to the central part of the range; and that the beds of granite in the central part are frequently vertical; we feel assured that their present contorted or vertical position, is not the original one. The opinions of geologists have been much divided respecting the cause or causes that have elevated mountains, and given a vertical position to beds that once formed the bottom of the ocean. Those who maintain that subterranean heat has expanded and broken the solid crust of the globe, and has raised from vast depths the ancient bed of the ocean, appeal to a cause that is known to exist, and which seem sufficient to explain most of the various appearances which Alpine regions present.

In opposition to this theory, it is asserted that there are no remaining vestiges of the action of subterranean fire in the Alps: but this I am convinced is erroneous. It is true that from near the source of the Rhone, to the foot of the Little St. Bernard, there does not occur any known rock of a volcanic character, with the doubtful exception of some rocks in the valley of Sass, and in the Valorsine. I have examined various parts of this range on the northern side of the highest mountains in the Alps, along a line of one hundred and twenty miles; and though I could discover no indications of the action of subterranean heat in the rocks themselves, I was greatly surprised to observe the numerous thermal springs that are abundantly gushing out at the feet of the primary mountains, near the junction of the mica-slate, or the dark schist passing into the mica-slate, with the lowest calcareous beds of that vast series of limestone strata, which forms the outer ranges of the Alps. Numerous as these hot springs are on the northern side of the Alps, and not unfrequent on the southern side also, it appeared to me remarkable, that they had hitherto been regarded as isolated phenomena; and that their geological position had not been noticed. It is true, some of the warm springs in the Valais and in Savoy had been long known and visited. But the greater number has been discovered since Saussure published his Voyages dans les Alpes; and it appears probable, that they would every where be found near the junction of the primary and secondary rocks, were it not for éboulements that have covered them with a heap of ruins, or that torrents from the glaciers have mixed with them, and reduced their temperature. Since I visited Savoy in 1821 and 1822, another considerable warm spring has been discovered near the village of Chamouni, at the foot of a glacier; and in 1820 several thermal springs were discov ered in that branch of the Alps which extends to Grenoble.

I shall here briefly enumerate the principal known thermal waters in the Pennine Alps, and add some observations and inferences, which I trust will be acceptable to several of your readers.

NATERS, in the Haut Valais.-The warm spring rises under a rock of mica-slate on the north side of the Rhone. The temperature when I visited the place was 86° Fahrenheit; but it is variable, from the intermixture with surface-water. At the time of the great earthquake at Lisbon, in 1755, the mountain above the spring, I was informed, opened, and threw out a considerable quantity of hot water.

LEUK, in the Haut Valais,-situated in a deep gorge on the northern side of the Rhone. There are twelve springs, varying in tempe rature from 117° to 126°. These springs have been long known, and are visited by patients from various parts of Europe.

THE VALLEY OF BAGNES, in the Bas Valais.-The warm springs in this valley were buried under a heap of débris from the fall of part of a mountain, which destroyed the baths, the village of Bagnes, and 120 inhabitants, in the year 1545. The name of the valley is obviously derived from the baths. The temperature of the water unknown.

CHAMOUNI. The thermal waters at this place have been discovered since I visited Chamouni in 1821. I have received no account of the temperature; baths have recently been erected. The situation is near the junction of mica-slate, with the lowest beds of secondary limestone.

ST. GERVAISE, situated in a deep gorge on the north-east side of Mont Blanc. The thermal water rises near the junction of mica-slate and limestone. The temperature 94° to 98°. This spring was discovered about the year 1806: it is very copious. Baths have lately been erected, and are much frequented.

AIX LES BAINS, in Savoy ;-the temperature from 112° to 117°. The thermal waters rise in great abundance from two springs, situated at the foot of a lofty calcareous mountain, and are near the bottom of the great calcareous formation that forms the outer range of the Alps: there are also numerous hot springs in the vicinity, which the Sardinian government will not allow to be opened. Of the mode of douching at these baths, I have given a particular account in the first volume of my Travels in Savoy, Switzerland, and Auvergne. The thermal waters of Aix were well known to the Romans.

MOUTIERS, in the Tarentaise.-The thermal waters rise in great abundance from the bottom of a nearly perpendicular mass of limestone. From the position of this rock, and its connection with those on the opposite side of the valley, in which the hot springs rise, I have no doubt that it is the lowest calcareous bed in that part of the Alps; but its junction with mica or talcose slate is not here seen. The thermal waters of Moutiers, contain about two per cent. of saline matter, chiefly common salt. The process of extracting it, I have described in the Philosophical Magazine, vol. lxiii. p. 86.

BRIDA, in the Tarentaise.-The thermal waters of Brida were noticed in the ancient records of Savoy, but they were covered during a sudden inundation of the valley, and their situation was concealed for many years. In the summer of 1819, another inundation, occasioned by the breaking down of the side of the glacier, laid open the spring