James Keir and the Geology and Industry of the Black Country: Mineralogy of the South-west part of Staffordshire, 1798
Image: The Wren’s Nest from The Black Country – Sixteen Etchings of Scenes in the Coal and Iron District of South Staffordshire by Richard S Chattock
Text: Malcolm Dick
In 1845 most of the papers of James Keir (1735-1820) were destroyed in a house fire. Less is known about him compared to other Lunar men and there is still no major biography of him. Keir was, nevertheless, an important inventor and industrialist, making contributions to an understanding of gases, glass production, the manufacture of chemicals, metallurgy and coal mining.
Keir was interested in geology, a trait he shared with other Lunar figures – John Whitehurst, Matthew Boulton, Erasmus Darwin, William Withering and Josiah Wedgwood. They explored caves, collected fossils, investigated strata and speculated about the origins of minerals and the creation of the earth. Most of Keir’s adult life was spent in the Black Country where he acquired an intimate knowledge of its geography and geological landscape. In 1798 he wrote in the form of a letter to Stebbing Shaw, an account of the region entitled “Mineralogy of the South-west part of Staffordshire”. Shaw published it in his History of Staffordshire of 1798 and the text is reproduced here. Keir’s detailed and carefully observed account produced for the Black Country what Whitehurst had created for Derbyshire twenty years beforehand in 1778. Unlike Whitehurst’s An Inquiry into the Original State and Formation of the Earth, Keir did not provide the stratigraphical diagrams which made the earlier publication so original.
Keir outlined his intentions at the beginning by showing the connections between the geology of the area, local industry and wealth. The “valuable mines of coal, iron-stone, lime-stone, and clay” contributed to “the various and extensive trades” of South-west Staffordshire, “the foundation and prosperity” of towns such as Birmingham, Dudley, Wednesbury, Walsall, Bilston, Wolverhampton and Stourbridge and “the comfort and benefit of fuel” in nearby counties.
He described the “remarkable thickness” of the Black Country ten-yard seam of coal which stretched for seven miles with an average breadth of four miles. Keir also focused on the advantages of the iron ore, limestone and clay deposits which led to the building of furnaces, forges and foundries and the manufacture of guns, locks, screws and nails. Iron ore was the essential raw material, but limestone acted as a flux for blast furnaces, combining with impurities and speeding up the smelting process. Clay was turned into firebricks and moulds for metal products. He noted that the growth of canals stimulated demand outside the area and enabled markets to be reached.
Keir’s exploration of the geology of the area was substantially based on his own coal mine at Tividale, in the parish of Rowley Regis. He classified different types of coal, depicted methods of mining, located the extent of limestone deposits and described the ragstone channeled from the Rowley Hills. Towards the end of his article he considered explanations for the formation of coal deposits and the creation of local strata through volcanic action. Like Whitehurst, Keir contributed to the emergence of geology as a scientific subject.
Mineralogy of the South-west part of Staffordshire, by James Keir, esq. F.R.S.
IN compliance with your request, I will give you some account of the mineralogy of this Southern part of Staffordshire, and especially of those valuable mines of coal, iron-stone, lime-stone, and clay, to which not only the various and extensive trades and manufactures of this part of the country, and of those of the neighbouring towns, Birmingham, Dudley, Wednesbury, Walsall, Bilstone, Wolverhampton, and Stourbridge, owe their foundation and prosperity, but also the surrounding countries are, by means of the lately extended canals, indebted for the comfort and benefit of fuel. In drawing up this account (which the shortness of the time that your publication can allow prevents from being so accurate as I could wish) I shall endeavour to adapt it to the nature of your work, by confining myself to the great outlines and general principles of the subject, without descending to the minute descriptions of the mineralogist, or the technical distinctions of the miner.
The tract of country to which I wish to engage your principal attention is that which is distinguished by a bed of coal of remarkable thickness, generally ten yards, having been found at such depths as are within the reach of human industry and practical advantage. This tract extends from Bilstone, South-wards, to Bretiel-lane, Amblecott, and the Lye in the neighbourhood of Stourbridge, that is, about seven miles in length, and of various breadth, perhaps on an average about four miles. Thus, upon a very gross computation, this country may be estimated to contain about twenty-eight square miles; of which, however, a considerable part is covered by town ranges of mountains called the Dudley and Rowley hills, which pass through the middle of it, and prevent so much space as they occupy from possessing the benefit of coal-mines. This tract of land (through which the Birmingham canal, with its several branches, also the Netherton canal, and the Stourbridge and Dudley canal, pass, and give communication to the several collieries and other works,) comprehends the towns of Bilstone, Darlaston, Wednesbury, Dudley, Rowley, and Oldbury, together with the parishes of these towns, and those of Tipton, Sedgely, Gornal, and Netherton, with a little of the North-west part of the parish of West Bromwich, and also the several collieries about Dudley wood, Brettel-lane, Amblecott, and the Lye.
The abundance of coal, iron-stone, lime-stone, and clay, together with the intercourse opened by means of canals to distant parts of the kingdom, and particularly to the sea-ports of Bristol, Liverpool, and Hull, have, besides promoting the trade of the above-mentioned towns, induced the establishment of iron-furnaces, forges, and foundaries, and other extensive manufactories. The same advantages of coal and carriage give employment to a multitude of smiths and workmen, in forging iron into various goods, as guns, lock, screws, and above all, into nails. Of nails, the quantity manufactured in this district is perhaps greater than in any other equal part of the world; and, as this manufacture requires a very simple apparatus of a small heath, bellows, anvil, and hammer, it is executed at the workman’s own house, to each of which houses a small nailing shop is annexed, where the man with his wife and children can work without going from home: and thus an existence is given to an uncommon multitude of small houses and cottages, scattered all over the country, and to a great degree of population, independently of towns.
Such is the general description of the tract of country of the mineralogy of which I mean to give you some account. But it may be proper previously to observe, that, though I have confined myself within the limits of the bed of coal of ten yards in thickness, there are nevertheless other thinner beds of coal, of eight, six, and four feet in thickness, which extend themselves Northwards over a space at least as large as that which I have described. These thin beds commence at the distance of a few miles from the Northern termination of the ten-yard bed of coat, which ceases and crops out, as the miners say, that is rises abruptly to the surface of the ground, and appears no further in that direction. This cropping out of the thick coal is at Bilstone, Wednesbury, and Darlaston: and at a few miles to the North of these towns, the thin beds of coal begin to be found, and extend along the banks of the Wyrley and Essington canal, the neighbourhood of Walsal, Hayhead quarries, and of Lichfield, and in various parts of Cank wood. I shall hereafter give my reasons for believing that these thin strata rise from under the ten-yard coal.
To return then to the district which it is proposed to describe. In order to obtain a distinct idea of the mineralogy of this country, it will be proper to point out previously certain prominent features on the surface of the ground. Of these, the first that we ought to attend to is that range of lime-stone mountains which begin to rise on the Northern part of this tract of land near Wolverhampton and Bilstone, and extend themselves in a Southern direction to the town of Dudley, which is situated on the slope of the last of this chain of mountains, namely, on that which is rendered conspicuous by the fine ruin of a large antient castle belonging to viscount Dudley and Ward, and commanding by its bold projecting situation a widely-extended view.
The second great remarkable feature of this country is another range of mountains which begin to rise from the side of Dudley opposite to the lime-stone hill, and proceed nearly in the same direction, but a little more turned towards the East. This might be considered as a continuation of the former range, if their very different aspect, and the different nature of the Basaltic rock, of which they are composed, did not produce a striking distinction. This range of mountains proceeds from Dudley through Rowley, whence they are called Rowley hills, and, dividing into two branches, terminates in a valley between Old-bury and Hales-Owen.
Besides these two ranges of mountains, there are two detached hills, which, because they have an influence on the inclination or position of the coal, deserve notice. These are the hills on which Wednesbury church stands, and that which is near the village of Netherton.
It is an important fact, the knowledge of which tends greatly to the understanding of the inclination of the coal and other strata, that generally this inclination corresponds with that of the nearest lime-stone hill; that is, these strata rise in the same direction, though not in the same degree, as the hill or be of lime-stone rises. Now the range of mountains from Dudley towards Wolverhampton is formed of rocks or beds of lime-stone elevated to a high pitch on each side, and inclining so to each other, that by their approach they form an oblong ridge near their tops, not unlike the roof of a house. In the same manner the coal and its accompanying strata, lying to the East and West of these mountains, rise or crop up on both sides in directions corresponding with those of the neighbouring lime-stone elevation; so that, generally, the nearer a pit is sunk to a lime-stone hill, the coal is found at a less depth. I say generally, for, besides the irregularity of the surface of the ground from the greater or less thickness of the measures superincumbent on the coal, and which do not shew the same uniformity and correspondence as the coal and its adjacent strata, I shall afterwards shew that the coal itself is subject to very singular irregularities of position and inclination.
This general correspondence of the inclination of the coal with that of the lime-rocks is further confirmed by the two following circumstances:
1. The West side of the range of lime-stone hills is steeper than the East side; and , accordingly, the coal on the West side dips also more rapidly, and is sooner out of the reach of miners than the coal on the East side; which latter side, therefore, furnishes the principal collieries.
2. The lime-stone hill, that is at the Northern extremity of the range, does not appear to be elevated on both sides in the manner in which have described the general formation of those hills; but on the East side only. And, accordingly, the coal also is found on that side only; as if the elevation of the rock on the Western side had not been sufficiently great to make it appear above ground, or to raise the coal to such a height as to bring it within the reach of miners.
I have mentioned that the bed of coal does not extend over the lime-stone hills; but it seems to have broken off near their base; and it skirts their Eastern and Western sides, in some places its termination appearing above ground, but generally covered with earth. As this termination is not by gradual diminution, but abrupt and at once, like a fracture, we cannot from this circumstance, and from the corresponding inclination of the coal and lime-stone strata, avoid inferring, that the same convulsion which broke through and raised the strata of lime-stone into the form of mountains, must have also broken and raised the superincumbent strata, of which coal is one; and that these strata, being softer than the rock, were thrown off, or, having been shattered, have long since been washed away by the flood; so that now no vestige remains of the convulsion upon these hills but the solid ribs of lime-stone which form the mountains, and which have been able to resist the action of air and water.
Upon a first view of the subject, it may perhaps surprise that I have mentioned the coal as being superincumbent on the stratum of limestone; whereas the high mountains are formed from this stratum, and the coal is only found at greater or less depths in the lower grounds. But whoever would form just notions of the strata of any varied country must keep in mind that valuable observation of Mr. Mitchell, in his paper upon Earthquakes, Philosophical Transaction for the Year 1760; namely that those mountains which have been formed by the disruption and elevation of their component rock, as all mountains composed of lime-stone strata are, (which disruption and elevation he attributes to some violent explosion or earthquake) do actually consist of those strata which in the plains are covered with many other incumbent strata, and consequently are originally the lowest of all that we know. As I have not an opportunity of illustrating this observation by a section of the strata, I will endeavour to exemplify it, and to shew how the strata, originally inferior, are now in some parts so elevated as to form mountains, in the following manner: take half a dozen or a dozen common cards, and place them lengthwise on the rise of an inclined plane so that the upper cards shall slide by their gravity, or be drawn downwards a little over the lower cards; thus the card originally lowest will now be the highest upon the plane, and its upper end will represent that part of the stratum of lime-stone which forms the mountains, whilst its lower end will appear to immerge under the other cards towards the lower part of the inclined plan representing the valley. The next highest cards upon the plane will represent the strata of earth and iron-stone intervening between the lime-stone and coal. The succeeding card will represent the coal itself; and the remaining cards will represent the several beds of earth and rock that lye between the coal and the surface of the ground.
In the same manner as the coal rises, or crops, up to the sides of the great range of lime-stone mountains, so it also follows the direction of the detached hill above mentioned; namely, that on which the church at Wednesbury stands, and that near the village of Netherton. In some intermediate place between the lime-stone range and Wednesbury, on the East side, and between that range and Netherton hill, on the West side, the coal lies nearly level, and from thence rises on both sides towards the respective hills. This position of the coals is called by the colliers a Trough. It is proper to observe, that though the coal follows the direction of all the known lime-stone hills, and of the two detached hills above mentioned (which I suspect are lime-stone elevations*), it must not be supposed that the coal follows the direction of inclination of the surface of the ground in general, the ordinary risings of fallings of which it seems to have no correspondence with. How the coal is affected with relation to the range of the Rowley or Basaltic hills, has not been fully ascertained, excepting that it certainly does not crop out along the skirts of these hills, as it does along the lime-stone range; whence the colliers have formed their opinion that it passes under and through these hills. It is certainly to be found at the foot of them on both sides, at moderate depths, and does not there crop out. Therefore we may suppose that it passes a certain way further under them; but whether it completely passes through from side to side without interruption is a question that cannot be with certainty ascertained, but which I shall consider more fully, after I have related the facts that are known respecting the coal and other strata.
OF THE STRATA OR MEASURES BETWEEN THE SURFACE OF THE GROUND AND THE COAL.
Having given a general survey of the coal country, I shall now proceed to a more detailed account of the strata and substances under ground, their relative situation, their irregularities of position, fractures or fissures, and whatever circumstances may seem to deserve most notice in a mineralogical or commercial view.
The number and thickness of the measures above the coal are so various and different in different places, that they scarcely deserve to be considered a regular strata, and have nothing of that uniformity which the beds of coal have, which are similar, at least in a very considerable degree, in thickness, quality, and
* I suspect, from this correspondence of inclination of the coal and of Wednesbury and Netherton hills, that these hills are lime-stone elevations, although this stone does not appear on the surface relative position, over the whole extent of the country. The irregularity in the thickness and number of the measures above the coal, occasions a great difference in the depth of the pits in different places. In some places the coal has been got at the surface of the ground in open quarries, and in other fields the pits are 140 yards deep. The strata containing iron ore (called iron-stone), and those which consist of a finer kind of clay, called fire-clay, pipe-clay, and pot-clay, from its power of resisting heat, and its fitness for making tobacco pipes and glass-house pots, are the next in order with regard to uniformity of thickness and position. As to the other intervening masses of rock, bind, clunch, and especially those upper earths which consist of red and yellow particles, they vary so much and so irregularly, that they frequently differ not only in the same field, but even at the distance of a few yards, and therefore no general account can be given of their order, number, or thickness. The kinds, however, of the measures are generally the same throughout the coal country, and of these a notion may be formed from the following list of measures found in digging a coal-pit in Tividale colliery, in the parish of Rowley, in 1797.
OF THE MAIN-COAL
The main coal consists of divisions, and indeed may be considered as a number of beds differing regularly in quality and thickness, and separated from each other by very thin partitions, which in some places are wanting, so that it has been generally mentioned as a single bed of coal of extraordinary thickness. These divisions or beds are distinguished by peculiar names, which, together with their thickness, are given below.
* Roach is a coarse ferruginous earth or clay, differently coloured and veined, red and yellow. It seems to me to consist of the decomposed particles of the basaltic rock, called here Rowley Rag, of which the Rowley hills are formed, with other alluvial matter.
† The rock, so called from its hardness, is white, and consists of a mixture of siliceous and argillaceous earths; which earths are mixed in different proportions. The rock has the largest proportion of siliceous earth. Next to this, are the rock-binds, which have more argillaceous earth, and consequently are softer than the rock. Then the clunch-binds have still less siliceous earth; and, lastly, clunch has the least of this latter earth, and is the softest. The clunch and clunch-binds shiver into flakes when exposed to the weather. The rock-binds, and still better the rock, retain their texture. The rock is subject to crack or fissures, through which the water flows; and it is chiefly from these fissures in rock that the water of mines issues. Thin lamin_ of coal are often laid horizontally in the rock, and frequently there is thin coal in the form of large broad leaves of aquatic plants, running in all directions through the rock.
‡ Clunch is a smooth soft earthy matter, which, on exposure to the weather, falls into shivers or flakes. It evidently consists chiefly of argillaceous earth, and contains more or less of the siliceous earth. I have not analysed it, and therefore do not know more of its contents. Sometimes it has a reddish or yellowish colour, and is then called by the colliers wild; but when it is of proper bluish or greyish colour, it is said to be kind; by which epithets the colliers express their observation that coal is generally found accompanied with clunch and other measures that are of white, black, bluish, and grey, colours, but very seldom with such as are red or yellow. The former colours are therefore said to be kind; and the latter are called wild, as being irregular and accidental.
Clunch generally contains balls of iron-stone.
_ Smutt is a mixture of coal and clunch.
_ This thin coal (called the Two foot Coal, though it is seldom thicker than eighteen inches) is the first regular bed of coal. It is too thin to be of any use.
** Fire-clay, called in some places Pipe-clay, from its having been made into tobacco-pipes, for which purposes it is not now used, not being white enough.
†† A parting is a small quantity, generally of clunch or soft earth, that separates the more considerable beds from each other. From these interstices between the strata or divisions of the coals itself generally proceeds the inflammable gas or air that incommodes the miners.
‡‡ Broach-coal is a coal of very good quality, which sometimes is got, but generally neglected, not being thought sufficiently thick to furnish a large enough quantity of big coals to render the working of it profitable.
__ The measure called Penny-earth is a clunch which contains a considerable quantity of balls, or nodules of iron-stone; for the sake of which pits are sunk in the neighbourhood of Wednesbury.
|||| Chance-coal is a name given to accidental masses of coal, which are not regular strata.
*** A smooth schistus, rendered black probably from its vicinity to the coal.
THE NAMES OF THE BEDS OF THE MAIN-COAL
The coal, including the partings, which are more various in their thickness than the coal, generally exceeds ten yards. But even the coal varies in the thickness of its several beds in some degree, though it every where preserves the distinction of different beds. A very extraordinary variation occurs in one instance. The two upper beds of the main coal, namely, the roof-coal and top-slipper, separate from the rest of the coal at Bloomfield colliery, and the separation grows wider and wider in a Northern direction, till at length these two beds, which when thus separated acquire the name of the Flying Reed, crop out to day and are lost, which the lower part of the coal proceeds on to Bilstone, where consequently it has only the thickness of about eight yards.
The interval between the two upper measure, or flying reed, and the lower part of the main coal, is filled up with soft clunch at the place of separation, which clunch assumes a harder texture, and at last is changed to rock that strikes fire with steel.
OF THE MEASURE BELOW THE MAIN-COAL
The measures which generally known under the main-coal, which in some place are dug for the sake of the iron-stone and glass-house pot-clay, and sometimes for the vein of the coal, called heathing-coal, are as follows.
|1. Dark clunch, generally about||0||1||6|
|2. Light-coloured clay, with small round iron-stone, called White Grains||0||2||6|
|3. Main iron-stone mine, that is, iron-stone balls or nodules, involved in clunch. Of this mine there are three distinct measures,||1||0||0|
|4. Table-batt, a smooth, level-faced, schistus. Sometime thicker,||1||0||0|
|5. White clay, containing white iron-stone,||1||0||6|
|6. Heathing-coal, in three distinct layers. Good coal,||2||0||0|
|7. Measures of clunch and white rock, to the pot clay, which is about sixteen or twenty yards below the main-coal, at the Lye, where it is principally got, the clay being there nearer the surface of the ground, and of a better quality, than in most other places which have been tried. This is the clay which takes its name from Stourbridge, its nearest town; and, from its quantity of resisting violent heat without melting, or even losing its strength and form, and consequent fitness for making pots to contain melted glass, is the principal cause of the establishment of a very considerable manufactory of the various kinds of glass, flint, bottle, and window glass, in the vicinity of Stourbridge, and in the town of Dudley.
Nothing is generally known under the above mentioned measures, the work of the miners never having proceeded further. But an opportunity was given a few years ago of discovering all the intermediate strata between the main coal and the lime-stone, by the late Lord Dudley and Ward, who ordered a canal to be made from Tipton green to his lime-quarries, in the Dudley castle hill, which passed under a part of the lime-stone hill. By this very considerable undertaking, all these intermediate strata were cut through as they were cropping up to the hill, and were observed to lye in the following order and thickness*.
From the above account, which I have no doubt is near the truth, though perhaps not minutely distinctive in the term of wild measures, it appears that that there are under the heathing-coal no less than four beds of coal, making in all a thickness of about twelve yards. I have already suggested my opinion that these are the beds of coal, which are found and worked in a considerable tract of country that extends
* The list these intermediate strata between the main-coal and lime-stone was given to me by the late Mr. Hurst, agent to lord Dudley, who superintended the work.
THE NATURAL HISTORY
Northwards from Bilstone, Wednesbury, and Darlaston, toward Walsall, and along the Wyrley and Essington canal. My reason for this opinion is, that the main-coal rises there towards the North, and crops out at the three towns above mentioned, Bilstone, Wednesbury, and Darlaston, after which it is no longer found in that direction; but a few miles beyond these towns, the thin beds of coal begin to be found rising in the same Northern direction, and accordingly give all the indication that the subject admits that they are continued from below the main-coal. The same thin beds have sometimes been found in the interval between the cropping of the main-coal, and the Dudley limestone hills, but are little noticed, as being of small value in comparison with the main-coal; however, as I thought they must exist there, I made enquiry, and was informed that they had been found sometimes, and in one instance worked, but that the colliers mistook them for the thin coals which lye above the main-coal.
From the accounts given of the measures above and below the main-coal, it appeared that in several of them, especially in those of clunch, the ore of iron, called in this country iron-stone, is found. Of these several beds, two only are worked for the ore; namely, that which lyes immediately under the broach coal, and that which lyes under the main-coal. In the neighbourhood of Wednesbury the former bed is worked, and in other parts of the country the latter is the more considerable. The iron-stone is generally got in coal works after the coal has been extracted; particularly where it lies at a moderate depth from the surface of the ground, that the expence of sinking pits may be less.
Iron-stone, when dug, is put up in masses called Blooms, the dimensions of which are three feet by four feet, with a height of 22 inches; and the weight is estimated at 35 hundred, each hundred being 120 pound. Sometimes 1000, or 1200, of such blooms are got from one acre of good mine. The quantity of iron-stone now got is sufficient to keep at work about fourteen smelting furnaces in the coal country, which produce annually about 18000 tons of pig iron; all of which, and more from other countries, is worked up in the foundries and forges of this neighbourhood.
SUBSTANCES OCCASIONALLY INTERMIXED WITH THE COAL
1. Pyrites is found chiefly in the measure called Brassil. It is known to be a compound of sulphur and iron. The quantity found in the coal of this country is very small in comparison of that which is mixed with the coal of Shropshire and some other countries.
2. Lead-ore, of the kind called Galena, is sometimes found spread in extremely thin leaves or plates upon the coal; but the quantity is too small either to do good or harm.
3. Spars, calcareous, and gypseous, chiefly the latter, in very thin plates, are to be seen sometimes on the coal. When the gypseous spar abounds, its vitriolic acid forms with the coal in the fire a sulphur, which blacksmiths observe is injurious to their iron. They therefore avoid making use of coal which has the sparry appearance.
OF THE QUALITY OF THE COAL, AND METHOD OF WORKING IT
The coal of this country is of that kind which does not cake, as that from Newcastle upon Tyne, and several other English coals, do; that is, its small pieces do not conglutinate in the fire; but, as it is stronger in texture, and consequently not so apt to be broken in small pieces in getting, and in carriage, that caking quality is not requisite. It kindles more readily, and makes a pleasanter fire, requires less trouble in management, and makes less dust, than the caking coals; and, in consequence of these properties, preferable for chamber fires. It is also a good coal for all kinds of metallic processes.
There is a considerable difference in the quality of the different beds or measures of the main coal. The first, or upper bed, called the Roof-floor, is generally left as a roof to support the earth or clunch above it from falling. The second bed, called the Top-slipper, and the third and fourth beds, which, together, are called the White-coal, are reckoned the best for chamber fires. Next to them in goodness are reckoned the eleventh and twelfth beds, called Sawyer and Slipper. After them come the eighth, ninth, and tenth, called the Foot-coal, Stone-coal, and John-coal. The tows and benches are preferred for making the coaks with which iron-ore is smelted; and therefore are generally reserved for the furnaces. They do not kindle and flame so vividly as some of the foregoing measures; but they give a more durable and stronger hear. These two measures contain the largest proportion of fibres resembling charcoal. The part of the brassil measure which contains pyrites is generally laid aside, or used only for burning bricks or lime. The humphries, being the lowest measure, is that which is cut away in order to let those above it fall down, and therefore most of it is reduced to small coal called Sleck.
The same beds of coal do however vary inn their quality in different coal-fields, and even different parts of the same field. In general the collieries on the East side of the Dudley and Rowley hills yield better coal than those on the opposite side. The coal is liable to different accidents. Sometimes it appears broken and crushed into small pieces, and is then called Mucks. Sometimes a bad quality of a very peculiar nature affects a greater or less tract of coal, the limits of which are distinctly defined from the good coal on each side. Coal of this kind is called Black, from its want of lustre. It gives less flame and burns less vividly, than the good coal. I expect that if it were distilled it would yield less tar or oil. Among the singularities to which our coal is liable, I must mention one, which though of no commercial consequence, will nevertheless be reckoned curious by the mineralogist. It is a species of coal which I have often observed in the cracks of the superincumbent rocks and strata, which, though very bright and shining in its appearance, gives little or no flame; in which respect it is similar to Kilkenny coal, and the Welch culm. But there is a circumstance in its texture which is peculiar, or which at least has not been observed by mineralogist; which is, that the coal is embedded in small cubical cells, formed by thin planes of calcareous spar intersecting each other at right angles. Mr. Buffon indeed mentions a kind of coal dug at Alais and in other parts of Languedoc, which contains so much powder of calcareous earth mixed with it, that it is burnt for the sake of the lime which is left; but there is no reason to suppose from his description that the Languedoc coal possessed that singularity of texture which I have described. Busson, Hist. Naturelle des Mineraux, tom. i.
THE NATURAL HISTORY
I shall not by any means pretend to give you the art of mining, which admits of great mechanical detail, and much knowledge derived from experience. I shall only observe that the uncommon thickness of this coal occasions a considerable difference in the method of working it from those employed at Newcastle, Shropshire, and other countries, where, instead of ten yards, the veins of coal are only four, five, six, seven, or eight feet thick. In order to support excavations ten yards high, it is necessary to leave very large pillars of coal, eight or ten yards in diameter, which pillars vary
however in size and frequency, according to the strength of the roof or stratum over the coal, and the firmness of the foundation on which they stand, as well as the soundness and strength of the coal itself. The manner then of getting the coal is what the colliers call by stalls, that is, by alternate pillars and excavations, which pillars are not afterwards hollowed out as is the Northern collieries. Consequently a much larger proportion if the coal is left ungot in our collieries. It is generally reckoned that one third part of the coal if left in the pillars, and that about another third is small coal, part of which is made into coaks, another part is consumed by the fire-engines belonging to the colliery and other works in the neighbourhood, and the rest is left in the pit. Accordingly there remains only about one third of the mine to be sold as large, marketable coal. This mode of getting the coal differs still more from the method called long work, practised in Shropshire, and in the thin mines adjacent to this country; in which method no pillars of solid coal are left; but the roof is supported during working by buttresses, of which the outsides are made of wood and large coal, and the insides are filled with the small coal or fleck.
The great height of the coal makes it necessary to cut and make it fall, at several different operations. When the pits are sunk, and communications made with the engine-pit for the water to run toward it, and also gateways or roads made for the conveyance of coal to the shaft of the pit, the colliers begin to get coals by working a stall. This they do by cutting out the lower bed called the Humphries, the length of their stall, ten, twelve, or fourteen yards; and when they have thus removed the foundation of the coal to a certain breadth, they then loosen its adhesion to the sides by cutting as high as the beds called Slipper and Sawyer, which accordingly make the first fall of coals; the Stone-coal makes the second fall; the John-coal or Slipps makes the third; the Foot-coal makes the fourth; the Brasil makes the fifth; the Benches and Tow-coal make the sixth; the Lombs make the seventh; the Jays make the eighth; the Top-slipper the ninth; and the Roof is seldom cut, but only as much of it got as drops spontaneously, and can be safely collected. It is the facility of separation, by means of the parting between the beds of coal, that principally getting this very thick mine from the ordinary thin mines, we may easily conceive the greater difficulty, expence, danger to workmen, and waste of mine, which attends the collieries of this country, and which considerably diminish the advantage arising from the greater quantity. To the above-mentioned disadvantages we may add the frequency of fires spontaneously kindling our pits from the great quantities of small-coal or fleck which are left there, not only because there is not sale for the whole of it, but also because it is only by means of heaps of fleck that the colliers can reach to cut the upper beds of the coal; the fall of which is also thus shortened, and the breaking of the coal into small pieces thereby prevented. But in thin mines this fleck may be raised above ground; and where the coal is of a caking quality, it is saleable. Having shortly mentioned the peculiarities which attend our collieries, I shall not enter upon what is common to all others; as, the methods of boring and sinking, of giving a free and permanent passage of the water from the different parts of the colliery to the engine-pit, where it is discharged; of producing a circulation of the external air through all the passages and openings of the mine, for the respiration of the colliers, and for discharging the fixed, azotic, and inflammable, airs, which fill these spaces. Of these airs, the inflammable alone is the produce of the mines; into which it comes through the cracks and fissures of the coals and rocks, and is abundantly produced from heaps of small coal. The fixed and azotic airs are yielded by the respiration of the miners, and by the burning of the candles. Modes have been lately introduced of winding up the coals from the bottom of the pits by small fire-engines, instead of horses; and of conveying the coals to the wharfs along iron-rail roads.
The quantity of coals raised weekly on the banks of the Birmingham canal, and its several branches between Birmingham and Wolverhampton, is computed at 15,000 tons, of which about 8000 tons are sent to Birmingham and beyond; 2000 tons towards Wolverhampton and the Severn; and 5000 tons are supposed to be consumed in manufacturers, towns, and villages, near the canal. There are also about 1200 tons carried weekly upon the Stourbridge and Dudley canal, which makes with the foregoing quantities a total of 16,200 tons of coal raised weekly from the coal pits of this district; to supply which consumption, upwards of fifty acres of mine must be worked annually. Dr. Plot tells us that in his time, about a century ago, there were generally twelve or fourteen collieries, each of which yielded from two to five thousand tons of coals annually, which at an average is about 45,500 tons annually, not equal to the present produce of three weeks.
OF THE LIME-STONE
The range of lime-stone hills extends from Dudley in the direction nearly of North-north-west. It consists of oblong hills, of which the West sides are, like those of most mountains, the steepest. The most conspicuous are, Dudley-castle hill, Wren’s-nest hill, and Sedgeley hill. The construction of the two former is that of several large beds of lime-stone, standing, on the West and East sides of the hills at a very steep inclination, corresponding with the external surface, in opposite directions, till they meet and rest against each other along the summit or ridge of the hills. But the last mentioned hill, which terminates the range at its Northern extremity, shews these beds of lime-stone inclined on the Eastern side only, as I have already mentioned; though it is possible they may exist also on the other side, but not sufficiently elevated to be seen externally.
The lime-stone beds consist of thin layers of the thickness from three to eight inches. In the centre of the hills there are large indefinite masses, called Crog, or good lime-stone. The beds are separated from each other by substances called Ratch and Bavin, which seem to be a mixture of calcareous and argillaceous earths. Immediately under the surface of the ground, detached masses of good limestone are found inveloped in loose earth; which masses are called turf-stone.
Some of these beds, like other lime-stones, contain abundance of petrified shells, of which some account is given by M. Dacosta in the Philosophical Transactions, vol. XLVIII. Among these shells there is nothing singular, but one very fossil representation of an animal, called by workmen a locust, “THE NATURAL HISTORY.
by others, the Dudley fossil, and by those naturalists who designate by peculiar names those petrified shells, although the same species are not known to exist now, at least in our climate, Pendiculus marinus trilobos and Anthropomorphites. The same fossil is said to be found in Caermarthenshire, and in the bishoprick of Paderborne, in Germany. See Lloyds Letter to Rivinus, and Bruckman’s Epistola Itineraria.
The lime-quarries in these hills yield to their noble proprietor a large revenue.
OF ROWLEY HILLS
These mountains, twelve in number2, extend from Dudley, in a South-east direction, to the parish of Hales Owen, where they terminate. They consist, as far as can be seen, of a peculiar dark-bluish grey stone, called Rowley rag, and of a reddish-yellow and sometimes bluish coarse clay, called Roach, without any sensible admixture of sand, lime-stone, or other earth. The stone or rag, when dug for mending roads and sometime exposed to air and moisture, decomposes into a reddish powder: and in the hills and fields at the bottom of the hills under the turf and soil, are to be found great quantities of pieces of rag, buried in this coarse roachy clay, which pieces are more or less decomposed, according to their thickness, or the time they have lain; some a quarter of an inch into their substance, and some thin pieces so completely destroyed that it can be barely seen that they have been rag. It appears to me, that this coarse clay, which abounds in such quantities in the hills and adjoining plains, is nothing but decomposed rag-stone. The stone, from its analysis and external properties, is of the kind called Basaltes or Trapp. It is in large masses in the mountains, of a quadrilateral form, with perpendicular and horizontal joints or cracks, standing on their edges, and generally inclined from South-west to North-east, as I have been informed. This position and these joints give the resemblance of a ladder, whence this kind of stone has received the name Trapp, which in the Swedish language signifies a ladder. In these basaltic masses balls of the same matter, composed of concentric coats, are frequently found.
The rag-stone has been accurately analysed by Dr. Withering, who found that 1000 parts of it contained 475 parts of siliceous earth, 325 argillaceous earth, and 200 calx of iron. But this iron seems to me to be in a very small degree of calcination, from the dark blue colour of the stone, from the rusty colour it assumes on being exposed to a further state of calcination by air and water, and from the magnetic property of the mountains, which , as Dr. Plot observed, turned the needle 6o from its proper direction. This magnetic property has been since observed in several Basaltic mountains, particularly in the Giant’s causeway, in Ireland, and very remarkably in a basaltic columnar mountain, called Compass hill, in the island Cannay, one of the Hebrides, described by George Dempster, esq. in the Transactions of the Society of Antiquaries in Scotland, vol. I.
OF THE FRACTURES AND DISLOCATION, CALLED FAULTS, OF THE COAL AND ACCOMPANYING STRATA; WITH SOME CONCLUSIONS AND CONJECTURES RESPECTING THE FORMATION OF COAL, LIMESTONE, AND BASALTIC HILLS.
I have in the beginning of my letter represented the coal and its accompanying strata, as rising up to the lime-stone hills, and to Wednesbury and Netherton hills (which I think are probably lime-stone at their foundation), and in general towards the extremity of the coal country, where they crop out to day and are lost. But this is to be understood in a very general consideration of the position of the coal and strata through the country at large; for in fact it is subject to many and great local irregularities, to sudden risings or fallings, and to fissures, sometimes small, and sometimes of a greater extent, by which the stratum of coal is broken and cracked, and its inclination altered, in various ways. These irregularities occasion much difficulty and disappointment to the workers of mines, especially where the fracture is considerable, and the fall of the coal on one side of it so great that it cannot be worked upon the level of the engine-pit, and consequently the water cannot be drained by means prepared for it.
The fractures or fissures are of various lengths, from a few yards to one or more miles; and the fall, or trapping down (as it is sometimes called), of the coal and other contiguous stata, on one side of the fracture, below the corresponding strata on the other side, is from a few inches to 60, 80, or 100 yards. When there is no intervening matter between the two faces of the fracture, it is called a slip, and these faces, which have the same corresponding obliquity of direction, shew a smoothness and polish which they seem to have acquired by the force with which they have been rubbed against each other. To these smooth surfaces the colliers give the name of gloss-faces. But when the fracture and fall are considerable there is generally an interval or space between the two corresponding faces, which space is filled up with some argillaceous matter, or more frequently with rock, which is called a fault*. This fault has the same oblique direction as the faces of the fracture, and extends through the strata to unknown depths. The coal which has been thus interrupted, and which has fallen below its former level, generally proceeds in the same, or nearly the same, inclination; that is, it continues to rise or dip nearly towards the same point of the compass as it did on the other side of the fault, though not always with the same rapidity. There are, however, exceptions to this rule. At least there is one very remarkable instance of a great fault near Bilstone, where the inclination or dip of the coal is quite reversed by the fault. The rock which composes the faults of this country is white, and consists of argillaceous and siliceous earths; but in some other countries the fissures, not only of coal but also of other strata, are filled up with basaltes, or whin-stone, and are called Whin-dykes, in the Northern parts of this island. See a curious account of the whin-dykes which intersect the stata in some parts of Scotland, by Mr. Milles, Phil. Trans. 1790.
Various opinions have been formed respecting the formation of coal. Some consider it as an argillaceous schistus impregnated with bitumen; which indeed may be the case with some species; which, however, ought rather to be called bituminous schistus than coal; in the best kinds of which there is too little argil-
*Their names beginning with those nearest Dudley, are Corney, Tansley, Bare Cook’s Rough, Ash or Cox’s Rough, Turner’s Pearl, Hailstone, Timmins, Rowley, and Whitworth.
*The word Fault, in this sense, seems to be derived from Faille, which has the same significance in the country of Liege, whence it is probable we received the art of working coal-mines, as those in Liege are the most antient of any in Europe, Faille evidently comes from faillir, to fail; because at these faults the coal fails, or is interrupted. Hence probably the expression “to be at a fault,” when we can proceed no further with any kind of work.
“THE NATURAL HISTORY
laceous matter to consider it as an essential part of its composition. The most generally received opinion is, that vegetable matter is converted into coal; but we know no similar fact or experiment form the analogy of which we can infer the possibility of such a conversion. I believe, indeed, that if all, or most coals, the vestiges of vegetable fibres, like the charcoal of burnt leaves, are to be seen, not, however, forming the whole substance of the coal, but interspersed as thin laminae between the thicker more shining bituminous layers of the coal. We know also that in all coal-mines, the superincumbent strata of clunch and rock contain abundance of vegetable impressions, chiefly of reeds and broad leaves, like the stems and foiliage of aquatic plants. The substance or body of the reed is sometimes rock and sometimes iron ore, and its surface is only covered with a thin coat of coal, as if the rocky or ferruginous matter, which filled up the space which had been occupied by the decayed vegetable, had by the contraction of drying left an interval, which was afterwards filled up by a bitumen, whether that bitumen came in a liquid form, or in the state of a distilled and condensed vapour, or whether it was the remaining oil and resin of the plant hardened by age, that is, according to late experiments, by absorption of air. But in the coal itself, we do not find any form of plants or any vegetable trace, but those resemblances which I have mentioned to the fibres of charcoal, which cross each other in all directions, and, by their want of gloss, are distinguished form the more bituminous parts of the coal. These fibres, however, are not in quantity real charcoal, but true fossil coal. How much, then, these vegetable matters, which originally formed the bed which is now the coal, have contributed to the formations of this substance, is a question very difficult to determine; whether by some operation unknown to our chemists, they have been compressed into a substance apparently so different from
them, or whether they have done little but furnish by their decay spaces into which the bitumen might be collected and deposited, that might have been raised or distilled from inferior beds of vegetable or animal matter by subterranean heat, or which might have been ejected from the bowels of the earth in a fluid state, and insinuated itself into those spaces formed by decayed vegetables; as the same fluid bitumen has been seen by late observers to be thrown out of Vesuvius. Some kinds of coal are entirely free from vegetable vestiges, and are an uniform compact bitumen. Such is that which is to be found in the cavities of calcareous rocks. According, then, to this opinion, which seems to me to be more convenient space for the insinuation of this ejected or distilled bitumen than the more solid strata.
But, in whatever manner coal may have been formed, an important inference may be drawn from the uniformity of the several beds composing the ten-yard coal, in respect to their qualities, thickness, and relative position over an extent of many square miles; namely that the coal has been formed all over the country at the same time, and likewise upon the level ground; for, what but the greatest regularity of surface could have given such uniformity to the deposition of the vegetable matter, which either formed the coal, or gave occasion and place for its formation? But a level surface of great extent must be accompanied with a marsh, from the want of defluxion to the waters; and, from the great abundance of the impressions of the stems and leaves of aquatic plants, it may be inferred that such had actually been the state of the surface of the ground when these beds were formed in which the coal afterwards existed. The formation of coal must therefore be referred to a very remote period even in the history of the earth, as it must have preceded the existence of mountains, and of those inequalities of surface, which are essential to the life of all but aquatic animals and vegetables. The shells of marine animals seem to have furnished the substance of those immense beds of lime-stone which envelope the earth; and when these beds were, by the gradual and successive accumulation of these animal exuviae, sufficiently elevated to the surface of the sea, or above it, they might then give a foundation for vegetable production; in the same manner as islands are now forming in the East Indies by the continental accumulation of coral beds. Phil.Trans. vol. LVII.
Another important inference, which perfectly corresponds with the former, may be drawn from the abrupt termination or cropping out of coal along the sides of the lime-stone hills, and from its existence on both sides (though not on the hills themselves) of equal thickness, and similar in the disposition and quality of the different beds; namely, that the coal had once been continued across the space now occupied by these hills, and consequently that the formation of these hills was posterior to the formation of the coal. It appears also, from the rearing of the beds of limestone, and their broken and irregular position, that their present from and state could not have been the effect of any gradual operation of nature, but of some sudden and violent effort or earthquake. Neither could this elevation and rupture of the inferior strata by effected without the elevation and rupture of the superior strata, among which is the coal, which accordingly does now appear to be still more disturbed and broken into minuter fragments, in proportion as it is of less solid texture than the stone. That part of the coal more particularly which immediately lay upon the ridge of the elevated country, that is, where the hills now appear, would be most shattered, and, being by its elevation most exposed to the action of winds and floods, would in time be worn and washed away, and leave nothing but the harder rock which now remains.
When the elastic vapour and air, that were the immediate cause of the earthquakes and elevation of the strata, began to lose their force, either by escape at the fractured tops, or by condensation from cold. The weight of the incumbent strata would incline them to subside; and this subsistence, being resisted more in some places, and in others less, by the greater or less cohesion, and support, would occasion still greater irregularity in the fractures; and to this cause, no less than to the elevation, I am inclined to impute those frequent and extensive fissures, and sudden depressions of the coal, which I have described as being known under the names of
Faults, Falls, and Slips.
In consequence of the unequal elevation and subsidence of the coal, many irregular vacuities must have been left, which afterwards have been filled up with argillaceous and rocky matters that have been washed into them, and become more or less consolidated. And, accordingly, these matters do now appear in the forms which they received from these vacuities, corresponding in the irregularity of their surface to the disjointed bottom of the coal, and forming in some places rocky ridges, which seem to rise up into the coal, the thickness of which is there diminished: or to spread itself horizontally between the beds of coal, which are accordingly in those places separated to a greater or less distance. The colliers generally express themselves as if the disposition and thickness of the coal had been regulated by the rocky bottom; but, in my opinion, the reverse of this notion is the truth.
The most singular and extensive vacuity in the coal of this country, now filled up with clay and argillaceous rock, is that occasioned by the separation of the two upper beds of the main-coal, which I have already mentioned under the name of the Flying-reed, and which begin to part from the lower beds of the coal at
“”THE NATURAL HISTORY.
Blomfield colliery, form whence they continue to diverge for several miles till they drop out at the surface, and are lost before they arrive at Bilstone. The separation of strata originally contiguous, and the subsequent interpolation of adventitious matter, is a very curious fact in the history of the earth. A remarkable instance of this kind is observed in many parts of the Peak of Derbyshire, where extensive beds of road-stone are inserted between strata of limestone, the corresponding fissures and metallic veins of which (not being continued through the interposed road-stone) demonstrate the original contiguity of those strata. Mr. Mitchel ascribes the great extent of earthquakes to the greater facility with which the elastic fluid forces its passage between the horizontal strata, which have but small cohesion to each other than it could effect the transverse rupture of these strata, which, however, it must break through, by degrees, before it can discharge itself.
I have already mentioned that the coal does not crop out in its approach to the Rowley hills, as it does to the Dudley lime-stone hills; and, consequently, that it does not pass uninterruptedly from one side to the other, as the colliers generally believe, but which cannot be ascertained, on account of the mass of earth and basaltic stone which form these hills. The formation of these basaltic hills is much more difficult to explain that that of the lime-stone hills. for we know that the latter are part of strata which extend themselves horizontally over a great tract of country, but which in some particular places are elevated from their inferior situation by some violent convulsion, of which we see manifest indications, both in their own dislocated state, and in that of the superincumbent strata. But with regard to the stone of which Rowley hills consist, we do not know of any such inferior stratum, by the elevation of which these hills could have been formed. We are certain that no such inferior stratum, by the elevation of which these hills could have been formed. We are certain that no such stratum does exist between the surface of the ground and the limestone; for we have, by sections of the earth, discovered what these strata are; and, besides, if the Rowley stone were a stratum originally lying above the lime-stone, and which had been afterwards elevated, as the lime-stone is elevated in the Dudley hills, we should on that supposition see, all along the lime-stone hills, this basaltic stone, or Rowley rag, as it is called, cropping out, as we now see the coal; which is certainly no where the case. If on the other hand, the rag were a solid stratum, originally lying below the limestone, which had afterwards been by earthquake broken and raised into the from of these Rowley hills, we should now see, all along the sides of these hills, not only the lime-stone, but also the coal and other superior strata, cropping out; not the smallest vestige of which appears. It may be imagined that these basaltic mountains are alluvial, that is, formed by deposition of matter washed down from former higher mountains, which have been thus confirmed; for certainly no such now appear. But, besides, the improbability of these higher mountains being washed away entirely while the lower ones remain, there is an argument which appears to me satisfactory that these hills are not alluvial; for the matter of which they consist had been so much exposed to air and water as they must have been on that supposition, it would now appear in the calcined, decomposed, and discoloured state, which it so readily acquires upon such exposure. If it be pretended that basaltic hills are of the kind which mineralogists have thought proper to call primitive, that is, anterior to all other formation or change on the surface of the earth, this pretension will be defeated by the consideration that the coal lyes under these, and, in a great number of instances, other basaltic rocks; and, consequently, that their formation is posterior to that coal, which, containing so many vegetable impressions, cannot be considered as primitive. But, if these basaltic hills cannot have been formed by the elevation of any solid stratum above or below the limestone, nor by alluvion, nor be primitive, I do not know any other mode of formation that can be supported by analogy, excepting that by means of matter ejected in a fluid state from the bowels of the earth, through a chasm of its surface; whether that fluidity was the consequence of fusion by fire, or of water mixed with the smaller particles of earth; after which ejection, the fluid matter may have been consolidated, either by cooling, or by gradual evaporation and dying. But, as no such basaltic fluid matter exists between the surface of the ground and the lime-stone stratum, it is evident that it must have come from under this stratum; which it could not do without producing an elevation and rupture of the lime-stone; that is to say, unless the elevation and rupture of the lime-stone, which constitutes the range of the Dudley hills, be continued nearly in the same direction, though with less elevation, under the basaltic hills. Impressed with this opinion of the probability of the continuation of the lime-stone elevation under the Rowley hills, and of the subsequent formation of these hills by ejection of the fluid matter, I made enquiry respecting such facts and appearances, as might furnish indications tending to confirm or refute this theory. The result appeared in favour of it.
1. The lime-stone and basaltic mountains are so nearly in the same line, as I have already remarked, they might be considered as the same range, if their aspect and quality did not differ. Dudley stands between the two ranges, or rather on the slope of the Castle-hill, which is the Southernmost extremity of the lime-stone hills. Between Dudley and Cawney-hill, which is the nearest of the basaltic range, there is a neck or ridge of land sloping to the East and West, on both sides of which, but not on the ridge itself, coal has been found. In this respect, then, this ridge, although the lime-stone does not break out on the surface, corresponds with the lime-stone range, of which there seems to be a probability that it is the continuation.
2. In digging a subterraneous tunnel on the South-west side of ht Rowley hills, to form a part of the Netherton canal, some lime-stone and marine vestiges were found.
3. The coal at Oldbury, which is not far from the foot of the Rowley hills, rises towards those hills as it does generally towards lime-stone hills, and not towards Dudley hills, these last being at a much greater distance.
4. Near the Southern extremity of the Rowley hills, in a valley between Oldbury and Hales-Owen, that is, in a line of continuation of the Rowley and Dudley hills, a lime-stone quarry was opened some years ago, but was discontinued on account of the stone not being of the best quality; but it was certainly lime-stone, and used as such.
These facts give the strongest indications, that the lime-stone elevation and fracture are continued under the Rowley hills; and that they might give an issue to any fluid matter that might be ejected.
The formation of basaltic rocks has been the subject of a controversy which has been agitated with great zeal by mineralogists, some of whom consider them as lava thrown out of a volcano, and others as the produce of watery deposition; and the advocates for these two different opinions have been disinguished by the names, Vulcanists and Neptunists. The celebrated Bergman ascribes the basaltic matter to ejection
“”THE NATURAL HISTORY.
from volcanos, but he does not consider this matter as a lava melted by fire, but a mass of earthy particles softened and diluted with water, which afterwards has become dry and consolidated. This controversy seems to have derived additional importance and interest from the striking property which has basaltic stone possesses of assuming sometimes a columnar, and frequently also as articulated form, which it exhibits, to the admiration of mankind, in those magnificent and stupendous structures, the Giant’s Causeway in Ireland, the island Staffa, the extinct volcanos of Auvergne, and in many other parts of the earth, and which have lately been traced in Vesuvius and Etna. The subject is too large, and the controversy too intricate, for this place. I have elsewhere shewn the analogy which subsists between the controversy and spherical basaltic stones, and the artificial crystallizations which I had observed in glass; and thence inferred the possibility of the formation of the former by fusion and very gradual cooling. But I now confine my attention to the local appearances, and to deductions from them. I must not venture into the extensive field of comparison and illustration, which the mineralogy of other countries would afford, and which would shew that the same analogy and relation that subsist here between coal, lime-stone, and basaltes, extend very generally, though with considerable variation of circumstances. I will only add one further observation on the basaltes of this country, which is likewise generally applicable; namely, that the spontaneous decomposition, or gradual destruction of this stone, is no less worthy of attention than its formation. For basaltes, like lava, and other stones of a similar composition, is remarkably subject to be decomposed by the action of water and air, and to fall into a powder or coarse clay, called Roach, consisting, like the stone itself, of argillaceous, siliceous, and ferruginous particles. These particles, by further exposure and decomposition, and by different mechanical and chemical, may have been separated and converted into the various clays, more or less pure, rocks, clunch, and iron-stone, with which this country abounds. When we see the alteration on the surface of this stone which the exposure of a few weeks produces, we cannot doubt that the continued effects of many succeeding ages must have been very great; and that much of the circumjacent ground must have been derived from this source; while the different beds of coal seem to shew the successive periods of vegetation and alluvion.
Such, sir, are the only conclusions and conjectures which have been suggested by observing and reflecting on the existing facts and appearances of this country. If I should have too much indulged my imagination, I shall only have fallen into the same error, which has misted all others who have before me treated on the theory of the earth; and which it is the more difficult to avoid, as the circumstance of the early ages of the world when the great changes happened, must have been very different from those now exhibited to our observation; which is therefore insufficient to enable us, with strictness of reasoning, to investigate Nature in her primitive grand operations. Nevertheless, I may apologize for the attempt in the words expressed by the great Leibnitz on a similar occasion: Magnarum rerum etiam tenuis notitia in pretio habetur*.
I am , sir,
Your most obedient servant.
June 14, 1798.
Continue browsing this sectionJames Keir and the Geology and Industry of the Black Country: Mineralogy of the South-west part of Staffordshire, 1798
Sources and Further Reading
Molliet, Mrs Amelia, Sketch of the Life of James Keir (London, 1868).
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