brated rock-salt mountain at Cordova, which is nearly 300 feet high. The salt alternates with parallel beds of clay, gypsum, or sand. Near the same place is a promontory of red salt, 660 feet high, and nearly solid throughout. The whole Island of Ormuz, in the Persian Gulf, is said to be a solid mass of fossil salt. In South America the salt mines are numerous; and some are found in Peru, at an elevation of 10,000 feet above the sea; but even in these elevated regions, it is always associated, as in other countries, with secondary and diluvial formations of lime-stone, clay, sand, sea shells, &c.

As to the origin of these remarkable deposits, we may conclude, from the accompanying phenomena, that the salt has been deposited in hollows, on the retreat of the diluvial waters, and that the moisture has been evaporated or drained off in the course of subsequent periods.

That the waters of the ocean are found to be more richly impregnated with salt, the greater the depth from whence they are taken, is a fact which has long excited the remark of philosophers; and it appears highly probable that, from the greater specific gravity of salt water, a very extensive deposit of solid salt may take place in the greatest depths of the ocean itself. The reflux current in the Mediterranean sea is easily accounted for on this principle, that, as the waters are forced into it by the winds and the tides, and a great evaporation takes place from its inland surface, the impregnated salt water sinks, and being constantly supplied by the entering current, the lower strata, heavily charged with salt, are forced out again into the ocean, at a depth far beyond our observation.

We have a most interesting illustration of this fact, in an account given (in the 18th number of the Edinburgh Journal of Agriculture,) of the opening of the lake of Lothing, at Lowestoft, in Suffolk, on the 3d of June, 1831, when the new harbour was first entered by sea-borne vessels. The salt water entered the lake with a strong under current, the fresh water running out, at the same time, to the sea, upon the surface. This fresh water was raised to the top by the irruption of the sea water beneath, and an immense quantity of yeastlike scum rose to the surface. The entire body of water in the lake was elevated above its former level; and on putting down a pole, a strong under current could be felt, bearing it from the sea. At one place, there was a perceptible and clearly defined line, where the salt water and the fresh met, the

former rushing under the latter; and upon this line, salt water might have been taken up in one hand, and fresh in the other.*

Mr. Cox, in describing the salt mines of Wielitska, near Cracow, in Poland, says, that the latter city is completely undermined, and stands, as it were, on pillars of salt. The strata of the whole mine are described minutely by M. Guetard, who says, that the upper surface, like a great part of Poland, is sand, then follows clay, occasionally mixed with sand and gravel, containing fossil animal remains; and the third stratum is calcareous rock, or gypsum; from all which circumstances he very naturally concludes, that this spot was formerly covered by the sea, and that the salt was deposited from its evaporated waters. All the above extraneous formations being evidently diluvial, like those at Paris, guide us to the exact period of this, and all other salt deposits.

It only now remains for us to take a general view of the coal formations, and endeavour to discover whether there is any analogy between them and those we have already been considering. The first striking circumstance in the coal fields, is, that they have no connection with primitive rocks, but, on the contrary, are always found in secondary and plain countries. They lie amongst sand-stones, clay-slates, and calcareous rocks, but have, in no instance, been found below chalk, which is one of the best defined secondary formations immediately preceding the deluge, as has already been shown. It is true, that in the unreasonable systems of general and continuous stratification over the whole globe, which so much prevail in the geology of the present day, coal is made to lie far beneath chalk, and is, consequently, supposed to be a formation of a much earlier period. Calculations have accordingly been made, as to the probable depth of coal beneath chalk; assuming, as a fact, that the dip of the coal strata continues in the directions we now find them to lie in different coal fields. Such calculations will be elsewhere shown to lead only to error and confusion.

The following passage in an able article of the Edinburgh Encyclopædia, on the geology of England, will serve to show, in the clearest manner, the general nature of the coal

*Great quantities of fresh water fish perished on this occasion; one pike, however, of 20lbs. weight, had found time enough to devour a herring, which was found entire in his stomach.

fields of our own country; and all similar fields may be traced to similar situations, by extending our views on a sufficiently large scale, and not being misled either by the dip of the strata, or by the nature of the embedding rocks.

"The principal coal fields, in the northern part of this district, lie in Northumberland and Durham; the West Riding of Yorkshire; and in Derbyshire. The strata of coal terminate a few miles north-east of the town of Derby, but make their appearance again to the south of the Trent, in Leicestershire, near Ashby de la Zouch: on the south-east, they terminate at Charnwood Hills; while, on the south-west, a thick bed of coarse breccia and gravel separates them from the coal fields in the county of Warwick."-England, p. 713.

"Although, as we have already remarked, the red sandstone rock cuts off the coal fields in general, yet, in some parts of Lancashire, and the western counties, detached coal fields are surrounded by it. All the strata of coal, and ironstone, in South Wales, are deposited in a lime-stone basin, the form of which is an irregular oval, in length 100 miles, and, where broadest, 18 or 20 miles. The upper stratum of coal is at the depth of 50 or 60 fathoms; the succeeding strata lie deeper, and are accompanied with paralleled strata of iron ore: the lowest strata at the centre range are from 600 to 700 fathoms deep." (This depth has, of course, not been found from actual measurement: 700 fathoms is not far from a mile; and it may be doubted, as is elsewhere shown, whether any secondary formations extend to so great a depth.) "In this basin there are 12 strata of coal from three to nine feet thick, and eleven others from eighteen inches to three feet, making in all 95 feet of coal. The lime-stone that forms the substratum of this mineral deposition, appears on the surface all along the boundary of the basin, and is supposed to have an underground connexion, from point to point."-Edin. Encyclop. England, p. 714.

Nothing can be clearer than this account: and it appears certain, that as in the case of the Paris basin, this lime-stone formed the bed of the antediluvian sea, on which the diluvial deposits of coal, clay, iron-stone, and free-stone, were alternately laid at the same period. This being admitted, we have a natural means of accounting for the various inclinations in the parallel strata of such diluvial deposits. For, in the first place, they must have followed any inclinations that might have existed in the bed on which they were laid;

and, in the next place, we cannot conceive so great a mass of very moist materials becoming drained of their moisture, and settling down into a dry and hard state, by their own weight, without subsiding more in one place than in another; and we can thus account for those derangements in coal and other strata which always occasion trouble, and often much expense to the miner; and are called by the technical and provincial names of troubles, hitches, nips, slips, &c.

If any additional proof were wanting of the formation of coal having been occasioned by terrestrial vegetable substances, deposited by marine action, we should find it in the presence of the impressions of fish and shells in the strata of coal in Leicestershire. It may be said, that, as coal is called by geologists a fresh water formation, these aquatic fossils most probably belong to fresh water lakes; but this reasoning is not consistent with numberless other facts, exhibited in the coal strata, and which fully prove their connection with the sea.

There occurs also in the coal districts another difficulty, which is not so easily accounted for, although we may form some indistinct idea of it. This is, the solid dyke of a different mineral, which sometimes completely intersects the strata, and appears to have been injected, as it were, into a fissure occasioned by the subsidence above explained. We discover something analogous to these dykes, in the remarkable beds of solid flint, which intersect the strata of chalk, in every direction.* These dykes of flint, though they never

* During a residence of some time in a chalk district, on the coast, I have had an opportunity of paying some attention to the formation of flint; a subject which has never yet been duly explained, and which will, probably, long continue a problem in mineralogy. With regard to the actual composition of flint, I consider it clearly to be a petrified fluid drained from the calcareous mass, in a moist state. The perfect fluidity of flint, at one period of its formation, is distinctly proved, by the fossil shells often completely embedded in its substance, or preserved in the most perfect manner, attached to its surface. Shells, in a very complete state of preservation, and of the most fragile nature, are often found neatly filled with pure flint, even when at a distance from any bed, or nodule, of that matter, from which we might have concluded them to have been accidentally filled, like melted lead into a mould. This fluid matter, however, evidently did not follow the general laws of fluids, by retaining a horizontal surface; for I have, in my collection of fossils, some shells of echini, which I found to be half filled with chalk, and half with flint; the latter, with a rounded surface, and in a sloping position. The flint, in these specimens, is, also, quite unconnected with the only two

extend to the thickness often found in the coal strata, are spread both laterally and vertically over a very considerable space. They are distinctly proved to be a formation subsequent to the chalk itself; and appear, like all flints, to be the petrified calcareous fluids drained from the whole mass in the course of pressure. It is not easy to account for the manner in which the strata of the chalk were sustained, and kept asunder, whilst the petrifaction of this juice was going on; but this, like many other such difficulties in mineralogy, does not affect the general question; nor ought the dykes of the coal fields to be advanced in opposition to the general principle of formation which we have now been considering.

orifices by which the liquid matter could have entered from without; it would, therefore, appear to have originated within the shell. And this idea is further confirmed, by finding, in other beautiful and perfect specimens, filled with flint, that the substance is gently rounded outwards at the orifices, as if pressed in a thick gummy state from within; instead of being hollowed inwards, as lead is, when poured into a mould from without. I have also found, occasionally, that those nearly spherical nodules found in the chalk, are sometimes hollow, and contain, in the cavity, a yellow calcareous liquid, of the consistency of cream, and perfectly tasteless. The elongated and irregularly pointed nodules, are often found in the form of hollow tubes; within which, are sometimes minute crystals, and at other times, the matter has shot into long and delicate fibres, like hair, curiously interwoven. All these appearances in flint, distinctly prove it to have been a fluid, subsequent to the deposition of the chalk in which it is now found; and that it may, perhaps, properly be termed the juice of the calcareous mass, in the course of dessication, converted into stone, by those unaccountable chemical laws, which now govern the mineral world. The cause of the singularly irregular cavities in which the flints have been formed, and of their horizontal stratification in the chalk, must, for the present, remain subjects of conjecture alone; but, like the dykes in the coal strata, or the grottoes and fissures in lime-stone rocks, they do not in the least affect the general question.