with those before mentioned, and a careful examination would no doubt detect numerous anticlinal and synclinal lines running across the country, with an approximately N. and S. direction. An anticlinal line, running N. and S. by Wetley Rocks and Cellar Head, certainly separates the Cheadle coal-field from that of the Potteries for some distance, as by Cellar Head shale may be seen, containing a bastard limestone, at the top of the hill, the gritstone dipping rapidly from it on either hand. How far, however, this line may run to the S. is unknown, on account of the overlying beds of the new red sandstone concealing the carboniferous rocks from our inspection. On the other hand, the position of synclinal lines in this direction, or lines towards which the rocks bend downwards, is marked by the position of the coal-fields themselves, which of course lie in troughs formed by the bending downwards of the gritstone rocks on which they rest. The small patch of coal measures mentioned before as occurring at Goldsitch, lies in a deep hollow of the gritstone rocks, which rise rapidly from under it on every side into lofty hills, more especially to the W. and S. on which sides the summits of the hills exhibit great beds and ledges of rock, whose rapid dip towards the valley may be seen a mile or two off. The coal measures themselves, of course, follow the position of the rocks on which they rest, and, being horizontal in the centre of the basin, crop out on every side at an angle of 30°, except towards the N. where they are cut off by a fault. One bed of coal is here worked, which for a short distance is five or six feet thick: there are two others, neither of which exceed two feet. The northern part of the Cheadle coal-field, about Kingsley, contains three beds of coal, the thickest of which is three feet; the beds are very nearly horizontal, what slight inclination there is being towards the N.W. S. of Cheadle, however, and about Delph Houses, five beds of coal are worked, the uppermost of which is six feet thick, the whole section having a thickness of one hundred and six yards, and over this part the inclination is S.W. the beds dipping at the rate of one in nine. At Dilhorne, I believe, similar beds are worked, but they here crop both to the N. and W. shewing that the anticlinal line mentioned before as passing by Cellar Head, throws out the beds on this side, and thus far, at least, produces a real separation between the Cheadle and Pottery coalfields.

Concerning that far more extensive district, the Pottery coalfield, I regret that all the information I was able to procure is exceedingly scanty, owing partly to my own want of time, and partly to an absurd jealousy which still lurks in that district, with respect

sures.

to affording the inquirer any information on the subject. From what I could collect, the beds of coal are very numerous, and several of them upwards of six feet in thickness; but, if the different accounts were correct, great changes must take place, both in the thickness of the different beds, and the distances between them in different parts of the field. Mr. Heath, of Kidcrew, was kind enough to give me a section of the Hurecastle tunnel, in which a total thickness of upwards of three thousand feet of coal measures was cut through, containing twenty-eight beds of coal, whose thickness was altogether between sixty and seventy feet, and in which section neither the highest nor the lowest known beds are included. As, however, no mention is made of the occurrence of faults, I think there must probably be some mistake, and that some faults must have been unobserved by which a repetition of some of the beds was occasioned, producing this apparently enormous thickness of meaThe position of the beds in this coal-field is highly remarkable. Along the whole of the eastern portion, from Biddulph, through Burslem and Hanley, to Lane End, the beds dip west at an angle of 33°, on the average; but on proceeding two or three miles in that direction the beds are found to rise again, and in the country between Newcastle and Kidcrew they dip to the east at a similar angle. On the extreme western boundary of the district, however, they again recover their westerly dip, and plunge under the new red sandstone plain of Cheshire. About Kidcrew and Talk-o'-theHill the beds are greatly broken and shattered, one portion lying horizontal, perhaps, whilst its immediate neighbours dip E. or W. at the rate sometimes of eleven inches in twelve, or nearly 45°.* The direction of the chief line of fracture coincides with that of the ridge of hills called Mole Cop, Congleton Edge, and Cloud; and on examining these we find still stronger evidence of the action of the disturbing power. Along the W. side of Mole Cop, the upper beds of the mountain limestone begin to shew themselves near the base of the hill, and are worked at one or two points, having the shale above them, which is capped by the millstone grit. These two latter rocks compose the remainder of the ridge, their beds dipping to the E. and forming a clear escarpment to the W. Along this part of its course, then, the elevating force has not merely tilted the beds into a highly inclined position, and left them leaning against each other, as it were, for support, but has broken them clean through

* The workmen call the E. and W. inclinations "the Staffordshire dip" and "the Cheshire dip" respectively.

and lifted those on the E. side up into the air, while those on the W. remain buried at an unknown depth below the plain of Cheshire. If we compare the position of the rocks (such as it appears from even these brief notices) on the western side of the Penine chain,* with that of the same beds on the eastern, we shall be struck with the remarkable preponderance in the magnitude of the faults and dislocations of the former over those of the latter. This violently fractured state of the rocks on the western side of the district, and their comparatively undisturbed condition over the eastern portion, is true for the whole of this great range, and the ridge of Mole Cop is but a minor representation of Cross Fell.

In deducing from the examination of its structure a geological history of the district, the same remarks will apply to N. Staffordshire as to Derbyshire. We have, however, in Staffordshire, more striking evidence of the period intervening between the formation of the carboniferous system and the upper part of that of the new red sandstone, and of the great forces, both of dislocation and degradation, which were at work in the interval, than can be seen in Derbyshire. The fact of the new red sandstone running up the valley of the Dove and lying for several miles along that of the Churnet, following their windings, and resting with its horizontal beds against their broken and eroded banks, shews in the most striking manner that the carboniferous rocks had been elevated and disturbed, and these very valleys had been scooped out in them, before the deposition of the new red sandstone. The valleys seem, indeed, as if they had been arms of the sea running, like some of the Scotch lochs, into the dry land,† during the new red sandstone period, before which they must have been deeper than they are at present. During this period they were filled with new red sandstone up to a certain height, which at some subsequent period has itself suffered from an eroding cause, and the beds of the present rivers have been thus formed. These facts are important, as teaching us to look to a very ancient period for the beginning, at least, of those deep dales and ravines which cut through the mountain limestone and other hard rocks, and whose erosion seems impossible by any forces with

* The Penine chain is a term given by Phillips and Conybeare to the great central ridge of hilly country that runs from Derbyshire and Staffordshire to the borders of Scotland.

It is by no means meant positively to assert that the hills of Staffordshire and Derbyshire were dry land during this period, though several arguments might be brought forward to render such an idea probable.

which we are acquainted, unless acting through very long periods of time.

Concerning the very important practical question of the extension of the coal-measures beneath the new red sandstone districts, I am not at present prepared to offer any thing farther than was stated in the last number, except that some facts I met with tended to confirm me in the opinion of the present boundaries of the coal-fields, when ending abruptly against the new red sandstone, having been formed by denuding and eroding forces acting before the deposition of that rock, rather than by direct fractures and dislocations having marked them out, either before or since. If this opinion should be correct, the existence of coal measures beneath any part of the new red sandstone can only be determined by direct experiment, since we have no means of inferring to what depth eroding forces may have acted. It is, at all events, a circumstance well worthy of cautious examination before entering into an expensive undertaking in search of coal beyond the present fields.

OBSERVATIONS ON THE NATURE OF HEAT.

THE word heat, as used in common language, expresses a cause and its effect; it expresses the sensation of heat and the cause of that sensation hence philosophers, to avoid looseness of speech, have determined to strip the word of its two-fold meaning, and to confine it to the sensation, while, for the cause, they have framed a new word, viz. caloric. This distinction, I conceive, will appear sufficiently important to adopt it in the following remarks.

When the attention is first drawn to this subject, it may possibly be thought an easy matter to determine the nature of a principle so universal as caloric; but that men of the greatest fame in science differ in opinion upon its nature, will be ample refutation of the simplicity of the question. At present there prevail two opinions: the one is, that caloric is a subtle fluid, capable of entering into bodies and of being emitted from them; the other, that it is merely caused by the motion excited among the particles of matter; or, in other words, the one holds that caloric is material, while the other, that it is merely a property of matter. In entering upon this inquiry, it

will be necessary to consider how far caloric corresponds with our ideas of matter; then, which of the hypotheses gives the most plausible explanation of the phenomena dependent upon caloric.

If we adopt the opinion, as many do, that whatever is capable of acting upon our senses is material, the question is at once settled; but, to give greater scope to the argument, it will be better to fix upon some characteristics common to all matter, and then to find if there is any thing in caloric resembling or approaching to these. Extent and impenetrability are chosen as the indisputable characteristics of all material objects. The first implies, that every atom of matter must occupy space; the second, that no two atoms can occupy the same space in the same precise instant of time. "Were this latter proposition otherwise," says Sir John Leslie, "each body,or atom might be successively absorbed into the substance of another till the whole frame of the universe, collapsing into a point, were lost in the vortex of annihilation."

; or

Does this general and common characteristic of matter, extent, apply to caloric, or does caloric occupy space? It decidedly occupies space for most bodies, by an increase of density, give out caloric; or it is a general law, with a very few exceptions, that bodies passing from a larger to a smaller bulk evolve caloric the reverse, bodies passing from a smaller to a larger bulk necessarily absorb, or take in, caloric. Thus, according to the experiments of Mr. Watt, water, by conversion into steam, is enlarged about 1800 times. It may be urged that this is all very plain when caloric is viewed in connection with matter; but does it occupy space unconnected with matter, as we can conceive an atom or a number of

atoms of any elementary substance to do? This question certainly cannot be answered with the same clearness as that respecting caloric in connection with material objects. That it can, however, be answered in the affirmative, will be abundantly evident to any unbiassed mind who considers the following fact: the transmission of caloric in vacuo, as shewn by Pictet, by placing a thermometer in the exhausted receiver of an air-pump; and by Count Runiford, by placing the same in a Torricellian vacuum, the most perfect that can be found. Now, whatever passes through a complete void naturally occupies a portion of that, unless it be analogous to mental phenomena, which few would be willing to admit of caloric. Therefore, with the idea that caloric is material there is nothing preposterous in saying that extent is one of its essential properties.

The other essential property of matter is impenetrability, or that

VOL. IX., NO. XXVI.

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