same rock not parallel to each other; but crossing and cutting through each other at various angles. When that happens, one of the veins always passes on without interruption, while the other is cut in two, and the parts of it separated from each other. Now it is impossible to avoid concluding, from the whole phenomena of veins, that the rocks in which they occur existed before them. It follows, irresistibly, from the fact just mentioned, that the veins themselves were not formed all at once, but at different periods; and the way in which they cross furnishes us with the key to determine their relative ages. That vein which passes without interruption through another must be newer than that other; and the vein which is interrupted, and its parts separated, must be the older of the two.

7. Every substance has been found in veins, which constitutes a part of all the various rocks composing the crust of the earth. The rocks themselves, each in its turn, fill various veins. On the other hand, every substance hitherto found in veins has been found also in rocks. Hence, with respect to constituents, there is no difference between veins and rocks.

8. All the rocks which constitute the crust of the earth, and which have been described and named by mineralogists, with scarcely a single exception, occur also in veins. Now it deserves particular attention that the veins filled with rocks are just as regular in respect to position as the rocks themselves, with portions similar to which they are filled. The order which they observe is this. Every rocky vein (if I may be allowed the expression) occurs in rocks nearer the central nucleus than the formation of which it constitutes a part. Or, in other words, veins filled with a particular formation are always found under that formation, and never above it. Thus in the primitive rocks we find veins of transition and floetz rocks; but in the transition rocks, we never find veins of any primitive formation, but only of transition and floetz rocks; and, lastly, in the floetz formatious we never find veins either of primitive or transition rocks, but only of floetz rocks. The same invariable rule holds good with respect to the individual formations of all the great classes.

Farther, when two veins of different formations intersect each other, that which is filled with the formation nearest the nucleus is always cut through by the other.

The veins then follow the same invariable order with respect to position that the rocks do, and there is clearly a connection between them; but we know, from the facts already stated, that the veins must have been formed at different times. Now as the order in which they intersect each other is precisely the order of the position of the different formations, it follows irresistibly that the order of position is likewise the order of the formation of all the different rocks which compose the crust of the earth.

Here, then, we come to the knowledge of a fact of the utmost importance, that the rocks have been deposited in succession, that those nearest the central nucleus have been deposited first, and the others in the order of their position. Hence it follows that the language of the Wernerian geognosy is not hypothetical, since the formations must actually have been formed in the order of the classes; the primitive first, the transition next, the floetz next, and the alluvial last of all. The same holds good with the individual formations. Hence the terms older and newer, as applied to position, are perfectly correct. Granite is demonstrably the oldest, and floetz trap the newest, of the rocks.

9. Besides the rocky veins, many others occur not precisely similar to any beds hitherto discovered in the great mass of rocks; though it is neither impossible nor improbable that such beds may exist. Considerable progress has been made in classify ing these veins, which is the first step towards an accurate knowledge of them. When veins are composed of the same constituents disposed in the same order, they are called veins of the same formation. It has been already shown that several very complicated veins, exactly similar in every particular, occur in countries at great distances from each other, clearly indicating a correspondence in their formation.

In this paper I have thrown together some of the most important facts respecting veins, in order to draw the attention of the geognosts of this country to the study of them. They constitute the phenomena from which by far the most important data, relative to the way in which the crust of the earth has been formed, may be drawn. In some subsequent essays, which I shall occasionally insert in this journal, I shall throw together the documents by which the truth of the most important of the preceding facts has been ascertained.

ARTICLE V.

An Account of the dreadful Accident which happened at Felling Colliery, near Sunderland, on May 25th, 1812.

Extracted from an introductory account prefixed to The Funeral Sermon preached on the occasion, and published, by the Rev. John Hodgson.

(With a plan of the Colliery.)

FELLING is a manor in the chapelry of Heworth, and parish of Jarrow, about a mile and a half east of Gateshead, in the county of Durham. It contains several strata of coal, the

uppermost of which were extensively wrought in the beginning of the last century. The stratum called the High-main, was won in 1779, and continued to be wrought till the 19th January, 1811, when it was entirely excavated.

The present colliery is in the seam called the Low-main. It commenced in October, 1810, and was at full work in May, 1811. Messrs. John and William Brandling, Henderson, and Grace, have each a fourth share, both in its royalty and in the adventure they have also a lease from the Dean and Chapter of Durham, of a large extent of coal, lying on the south and east of the manor of Felling.

The working or down-cast shaft, marked A on the annexed plan, is called the John Pit, and is situated on the north side of the Sunderland road, and half way between Felling Toll-bar and Felling Hall. It is 204 yards deep, and furnished with a machine or steam-engine for drawing the coal, and with an engine called a whim gin, wrought by horses, and of use in letting down and drawing up the workmen, when the machine chances to be crippled, or repairing: and when it lies idle on pay Saturdays and on Sundays. Here is also a high tube of brick-work, employed in assisting ventilation while this shaft was sinking, and-till the communication by the narrow boards and the drifts was opened between the two shafts: since that it has been of no use.

The up-cast, or air furnace shaft, is called the William Pit. It is on an eminence 550 yards south-west of the John Pit, and is distinguished by a whim gin and a lofty tube of brick-work. This shaft is 232 yards deep.

Over each pit two iron pullies were suspended on a kind of scaffold, called the shaft-frame. In these ran the ascending and descending ropes. The pullies over the John Pit were six feet in diameter, and weighed nine cwt. a-piece. Those in which the rope of the gin of the John Pit ran, were fixed on a crane, which turned them over or from the shaft as occasion required.

As there are no feeders of water in the strata below the high main, the low main coal is kept perfectly dry by tubbing the watery seams with a circular casing of oak wood, formed into pieces resembling the fellies of a wheel: this contrivance has the appearance of the ashlar work of a well, and saves the expense of a steam-engine for drawing water. The white lines on the plan represent the excavated parts: the broadest of them are called boards, and those that cross them at right angles are walls. The two narrow lines which run north and south, on the east side, are called double winning head-ways, and the narrow lines between them, stentings: the two lines on the west side of the William Pit are also double winning licad-ways. The two

boards on the north are termed the narrow boards: they were the parts first excavated, and were made for the purpose of opening a communication for the atmospheric air between the two pits: the lines between the west end of the narrow boards and the William Pit, are called drifts. The inclined plane board is ́ marked P P on the plan.

The parallelograms formed by the boards and walls, are called pillars: they are solid masses of coal left to support the roof of the mine, and are each 26 yards long, and eight yards broad.

The single black lines in the walls and stentings represent stoppings, and the double lines trap-doors, each of which are placed to divert the current of atmospheric air through proper channels. The stoppings are made of brick and lime; and in this colliery, were strengthened on each side with a wall of stone. The trap-doors are made of wood: each of them is attended by a boy about seven, eight, or ten years old; and they are seldom used but in the avenues leading from the working shaft to the workings. At the circle N, the air crossed the waggon-way, and at M, the way to the stable, over arches of brick. The walls which have stoppings in them, are called sheth-walls, and those that are open, loose-walls.

In all large collieries the air is accelerated through the workings, by placing a large fire, sometimes at the bottom, and sometimes at the top of the up-cast shaft, which in these cases is covered over and connected with a furnace tube or chimney, by an arched gallery of brick from 40 to 60 feet in length. In this colliery the furnace was about six feet from the bottom of the tube.

The first course of the air, after descending the John Pit, was under the arch M, up the inner narrow board and the stable board S, to the trap-door at the head of the narrow boards; then down the board next south of the stable board; and so afterwards up two boards and down other two, till it traversed the newly formed sheth or set of workings, branching from the southernmost part of the double-headways on the east from thence it passed over the two arches up the outer board of the narro v boards, to the most westerly sheth of boards, and after fanning them, found its way down the crane board, along the drift to the William Pit, through which it ascended into the furnace, and thence, charged with noxious vapours, into the open air.

From this explanation it will easily be perceived that the purity and wholesomeness of a coal-mine has no reference to its depth. If the air be conducted through all parts of a mine, as here described, and no falls from the roof occur to prevent its visiting every corner, the old excavations, which are called wastes, will be constantly ventilated by as pure air as the boards in which the

men are at work-each part of the mine will be uniformly wholesome; but when obstructions occur, and are not speedily removed; when the fire in the furnace shaft is neglected; or when care has not been taken to place the stoppings and trapdoors in proper places, or the trap-doors are carelessly left open, or stoppings fall down,-in all these cases accumulations of firedamp* (called stythe by the colliers), immediately commence in

* NOTE BY THE EDITOR.-What is called fire-damp in coalmines is the carbureted hydrogen gas of chemists, as I have ascertained by direct experiments. It is composed of

Carbon
Hydrogen.

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28

100

or of two atoms of hydrogen, and one of carbon. I have been informed that it always exists in coal-mines, mixed with carbonic acid; and all the specimens of it which I have ever procured for the purpose of examination, contained a mixture of that gas. Hence I conceive that fire-damp is formed by the action of coal upon water. The water is decomposed, two atoms at once. All the oxygen combines with carbon, and forms carbonic acid; while all the hydrogen unites likewise with carbon, and forms carbureted hydrogen, or fire-damp.

I never could succeed in making any mixture of fire-damp and common air explode. It only burnt rapidly, with a blue flame, and little noise; but when mixed with oxygen gas in the proper proportion it explodes with great violence. Suppose we take 100 measures of pure carbureted hydrogen gas, it will not explode unless the oxygen present amount to 105 measures, and it ceases to explode whenever the oxygen amounts to more than 227 measures. Hence it would seem that whenever the fire-damp in mines amounts to th of the bulk of common air present, it will be apt to explode with a candle; and that whenever it exceeds th of the air, it will no longer be capable of exploding. All proportions between and will explode.

We are not acquainted with any means of preventing the formation of this gas; but it certainly might be prevented from accumulating, by ventilating the mine properly. If the usual method of fires, &c. be insufficient, nothing would be easier than to pump the air out of the mine, by means of an engine; and this would secure a perfect ventilation at all times, unless we suppose the workmen culpably negligent. I would advise the overseers of coal-mines, where fire-damp exists, to learn the method of analysing the air of the mine, in order to know when the fire-damp approaches to

th of the air, that they might be aware of their danger, and have it in their power to take the requisite precautions to prevent it. The process to be followed is very simple: it would not require any expensive apparatus, and might be perfectly learned in two or