lime-stone. It runs hence through the greatest part of Herefordshire, generally preserving the same direction and dip. It passes into Shropshire, where, from Mr. Aikin's observations, it appears to pass under the coal-fields. It forms a great part of Cheshire ; and, according to Mr. Aikin, contains the salt springs of Droitwich, &c. and the salt deposit of Northwich. I have followed it into Brecknockshire and Monmouthshire. The lime-stones which shut in the coal-fields every where lie upon it. These I shall denominate mountain lime-stones, for the sake of distinction. They may be traced from a few miles S. of Ross to Chepstow, forming the beautiful cliffs which overhang the Wye, and in a conformable position with the subjacent sand-stone, dipping to the S. W. In general the sand-stone consists of fine grains of quartz, with a little argil, and a variable quantity of oxide of iron and mica: but in the hills, and on approaching the lime-stone, its constituents are differently disposed. At the bottom of a hill we often find the common red sand-stone; higher up, a stratum of pudding-stone, containing rounded pieces of quartz, large masses of which in loose blocks cover the declivities; then there are beds of a whitish stone, the iron and mica disappearing, which makes a good building stone, but near these there is a thin bed consisting almost wholly of oxide of iron, and others almost entirely of mica. All these varieties occur in a hill near Ross, called Herol Hill. On the top of it the mountain lime-stone appears; and about a hundred yards further a pit is open, when the lowest bed of the forest coal rises near to the surface of the ground.

This red sand-stone formation is concealed near the Severn by the red marl rock and the Lyas lime-stone; but it appears again near Bristol, forming the basis on which the Somersetshire coal basin rests, of which Mr. Gilby has given an excellent account in the Philosophical Magazine for last November. I have seen it lying under the lime-stone near Axbridge, at the southern edge of this basin. This formation would appear every where to rest upon the

* Mr. Horner considered the Malvern Hills as affording countenance to the Huttonian theory. He observes, that the position of the stratified rocks seems to indicate that they were lifted up by a force from beneath. But if he had traversed the country to the westward of these hills, he would have found that the strata have generally a similar position, and even dip at a much greater angle, at the distance of 12 or 14 miles from the Malvern Hills. The absence of the stratified rocks on the eastern side may be accounted for by supposing that a submarine current flowed down the present Vale of Severn at the era when the rocks in question were deposited. Many indications may be found of the existence of such a cuirent; but if none could be produced, surely the hypothesis is fully as admissible as the ejection of the granite masses from the abyss of Tartarus.

+ It is very strange that, after all that has been said concerning this salt formation, we are yet without any satisfactory account of the stratum in which it occurs. Dr. Holland, in the first volume of the Geological Transactions, says, that it is subordinate to the sand-stone of the independent coal formation. Mr. Aikin, in the same volume, informs us that they belong to the old red sand-stone; and Mr. Horner, as 1 perceive by the abstract of his late memoir on the southeastern part of Somersetshire, given in the last number of the Annals, assiga them to the newer argillaceous sand-stone termed red mar).

transition rocks. I have mentioned its relation to those near Malvern. Mr. Aikin informs us that it rests, in Shropshire on highly elevated strata of grey-wacke; and I observe, by the last number of your Annals, that Mr. Horner has found it lying on the same formation near the Quantock Hills, in Somersetshire.

The red sand-stone is supposed to contain no organic remains. I believe, however, that I have seen traces of entrochites in it. The mountain lime-stone which rests upon it contains the fossils enumerated above, and which agree so remarkably with those of the transition formation. It often resembles the transition lime-stone in its texture, but is less crystalline, and has much thicker beds.*

From these considerations I think it is evident that the rocks belonging to the independent coal formation follow the old red sandstone in the geological succession, and are more ancient than any other member of the floetz series.

But further, we may almost venture to assert that the succeeding formations in the system of Werner have no existence in this country, and that the order of floetz rocks, from the old red sand-stone up to the chalk which form the greater part of South Britain, bear very little analogy to the succession pointed out by that celebrated naturalist.

I have stated that the strata above-mentioned dip most commonly towards the S. W. The coal, together with the micaceous sandstone and the argillaceous stone which forms the roofs, &c. of the coal seams, dip conformably; but this, as well as the general incli tion of the subjacent rock, is subject to variations. The whole commonly incline at a very perceptible angle. Over these rocks are deposited a series of strata which lie very nearly parallel to the plane of the horizon.

The first or lowest of these is that which Messrs. Townsend and Farey denominate red ground and red marl. It has, if I mistake not, been confounded with the old red sand-stone. Its composition varies; sometimes it is an argillaceous sand-stone, but without mica, and destitute of that slaty form which characterizes the older sand-stone. I never saw it contain any rounded pieces of quartz. In some places it becomes a marl rock, consisting chiefly of carbonate of lime. This is the case on the banks of the Severn, where it contains a bed of gypsum.† According to Mr. Townsend, the

*This resemblance accounts for the disagreement we find among high authori ties on the subject of these lime-stones. Mr. Werner, in his little book on veins, mentions the lime-stone rocks at the peak in Derbyshire twice: once he calls them transition rocks, and once affirms that they are floetz. M. Brochant says they are transition, and I understand that Mr. Jameson considers them as floetz.

I scarcely need observe that I have not mentioned these strata for the sake of claiming the discovery of them, but merely with the view of making some remarks on their order, and the relation which their succession bears to the series of M. Werner. A very accurate account of these formations is already before the public, in the paper of Mr. Gilby above referred to; and an extensive collection of interesting facts respecting these and other newer floetz rocks in South Britain is contained in the work of the Rev. I. Townsend, who mentions that he derived bis first information concerning them from Mr. W. Smith.

magnesian lime-stone of Derbyshire and the North of England belongs to this formation.

Above this is the Lyas lime-stone enclosed in a bed of clay. This stratum abounds in shells. In this respect it agrees with the second floetz lime-stone of Werner, which is called in Germany muschel kalkstein. It contains pentacrinites, which are considered as peculiar to this stratum. I have, however, found them in the oolite rock in Gloucestershire, but the Lyas is their proper abode, and they gradually disappear in the succeeding formations. It is here also that those large heads and bones are discovered which have been supposed to be the relics of crocodiles. They are of several species. The remains which Mr. Johnson, of Bristol, has collected, proves that some of them at least belong to an unknown marine animal. From the account which M, Cuvier has given of the cliff at Honfleur, containing the remains of crocodiles, I think it is highly probable that it belongs to the Lyas stratum. He mentions two species which nearly resemble the gavial. If any of your correspondents has seen the rock at Honfleur, and will favour us with an account of it, which may enable us to ascertain its identity with the Lyas lime-stone rock, it will throw an additional interest on these remains. All the other fossils occurring in this stratum are oceanic, among which are ammonites often three feet in diameter.

The Lyas formation is very extensive in South Britain. It is well known at Lyme and Chasmouth on the south coast, and traverses the island towards the German Ocean. I have been informed that it occurs in Anglesea.

Above the Lyas is the extensive calcareous formation containing the oolite or roestone. This cannot be, on account of its position, the roogenstein of Werner, which is subordinate to the second sandstone, and therefore below the muschel kalkstein.

Above this several other rocks are enumerated by Mr. Townsend, which I have not traced. Over these is the upper stratum of sandstone, which supports the chalk formation.

On the whole, I think it appears that there is very little conformity between the floetz series of Werner and that which occurs in South Britain; but the older formations, as far as they are yet known, coincide with his system. We may observe that the travellers, who in distant regions of the earth have been so powerfully struck with the conformity of geological phenomena with the observations of the Saxon Professor, as Humboldt and Von Buch, have chiefly directed their attention to the older formations. I am not aware that any disciple of the Freyberg school has detected the succession of floetz rocks, as detailed by Werner, beyond the limits of Germany.

But if we are to admit any reasons grounded on speculative geology, an universal conformity in the primitive and transition formations is quite as much as can be expected. At the period of the deposition of the last, the waters of the ocean are supposed by

Werner to have subsided, and to have formed separate basins or seas. The subsequent deposits must have varied according to local circumstances. Therefore some variety in the succession of floetz rocks rather confirms than invalidates the Wernerian theory of the earth. I have the honour to be, Sir,

Sketch of a General Theory of the Intellectual Functions of Man and Animals, given in reply to Drs. Cross and Leach. By Alexander Walker.*

SIR,

(To Dr. Thomson.)

IN the 26th number of your Annals of Philosophy, was announced a discovery of the use of the cerebellum and spinal marrow by Dr. Cross;-in the 27th number, Dr. Leach stated "that the same facts, or facts that lead to similar conclusions, were published in Lettres de Hufeland à Portal, 1807, and Anatomie du Systême Nerveux, &c. par Gall et Spurzheim ;-in the 28th number, I, conceiving that Dr. Leach meant to ascribe these discoveries to Gall and Spurzheim, denied that they were contained in the work referred to; t-and in the 29th number, Dr. Leach says, "Permit me, Sir, to assure you that the letter from Hufeland to Portal contains precisely the same opinion respecting the use of the cerebellum as that given by Mr. Alexander Walker and Dr. Cross; but he there adds, that he had quoted Gall and Spurzheim's work only as stating these opinions to be erroneous; and, while he asserts that my anatomical and physiological statements are" inaccurate, suppositious, and at variance with nature," he gives the results of his own recent examinations"-the conclusions which he draws after having "carefully examined the structure of the spinal mass of nerves." §

66

* Though this communication is rather too long for the Annals of Philosophy, we have given it a place, that every one of the Gentlemen concerned in this dispute may be upon a footing; but as the object of the Annals of Philosophy is not controversy, the Editor trusts that they will see the propriety of letting this subject rest where it is.-T.

+ Certainly when a Gentleman has said "that facts which lead to similar conclusions were published" in a particular work, meaning thereby to give them priority over another statement, it is most natural to suppose that such was the eriginal source of these facts; and, at all events, the conclusion is unavoidable that they are there considered as facts-the term which Dr. Leach employs. Annals of Philosophy, vol. v. p. 346.

Ibid. p. 345.

Now, Sir, however unimportant it may seem to Dr. Leach to investigate the origin of these statements, it seems otherwise to me, who imagine myself to have rather a deeper interest in them; and (though, in reply to this Gentleman, I shall not imitate him in the littleness of perpetually repeating his list of Christian names, as he has done my one; nor, ignorant though I am of him, shall I, like Dr. Cross, designate him as one Dr. Leach; for these are tendencies to personality, which is the bane of rational discussion ;) yet I shall blend the question of the discovery of these facts with that of their absolute truth. The question of the discovery of the circulation of the blood has not been deemed unimportant: I cannot reckon that which regards the circulation of nervous action less so; and into that question the use of the cerebellum enters. This, Dr. Leach will perhaps say is a comparison of very little men with great ones : be it so; but it is not a comparison of very little things with great ones; and to things alone do I wish to attend. No one will venture to say, that the general functions of the brain and cerebellum are less important than that of the heart.

With regard, then, Sir, to the cerebellum, as Dr. Leach, though he begs to be "permitted to assure you that Hufeland thinks it the organ of volition," has not quoted that writer's expressions, or, what is of more importance his reasons for such a conclusion, I cannot comment on them. If, however, I may judge of the accuracy of this ascription to Hufeland, by the additional assertion which Dr. Leach now makes as to Willis also having thought so, the conclusion will be most unfavourable to the Doctor's accuracy. Dr. Leach, then, adds that "Willis considered the cerebellum as the source of voluntary power." Now, Sir, it is an absolute fact, that Willis asserts the very opposite of this: he says it is the organ of involuntary power. "The office of the cerebel," says he, 66 seems to be for the animal spirits to supply some nerves, by which involuntary actions, which are made after a constant manner unknown to us, or whether we will or no, are performed."* And now, Sir, I hope you will permit me also to assure you, that I am not a little surprised that any Gentleman, after accusing another of inaccuracy, and referring with such confidence to his own "recent examinations," should have made so untrue a statement, in order to ascribe to an old author new observations. After this, I should be glad, indeed, to see Hufeland's statement, and his reasons for the conclusion alluded to; and, should that writer advance any proofs that the cerebellum is the organ of volition, or rather of those impulses which cause all muscular action, I shall of course readily resign to him the honour or disgrace of the opinion, and shall only regret that my reading has not been as extensive and as "accurate "" that of Dr. Leach.

as

I am willing, however, to grant something in favour of Willis :—

On the Brain, chap. xv.