On Some of the Differences in the Deposition of Coal

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77 after carefully drying, these were subiected without previous annealing to the heat of an intensely heated air furnace, and when thoroughly heated to the temperature of the furnace, suddenly withdrawn and exposed to a current of cold air. The following table shews the result obtained in each case :— ABCDEFGHIKL Degree of power of ) resistance to change )• 53664354634: of temperature. ) On comparing the results of these experiments, it appears obvious that those clays in which, according to the analysis given, the minimum amount of oxides of iron, and the alkaline earths is present in their composition, are the best adapted to resist fusion, or crack on being exposed to any sudden change of temperature; desiderata most essential for the purposes they have to be applied to. It is now universally admitted by chemists that clays are definite chemical compounds of silica, alumina, and water, the composition of such consisting of one equivalent of alumina combined with two of silicic acid, and two of water, and thus the various other bodies with which they are found associated are mere mechanical mixtures, to be regarded only as impurities; the presence of these substances materially impairing the qualities of the clays in which they are present.

ON SOME OF THE DIFFERENCES IN THE DEPOSITION OF COAL. BY SAMUEL BAINES, ESQ., OF LIGHTCLIFFE. Coal is of such paramount importance to this, or even any district, that it woidd be a work of supererogation to dilate upon the fact. It would not be too much to say that we owe more to coal for the prosperity of our country than to that boasted Anglo-Saxon variety of the proud Caucasian family of man, to which we belong. Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

My remarks will apply more particularly to the West York shire Coal Field, though I think, with slight variations, they are applicable to all; * the prevailing opinion being that all coal has been changed by heat into the many varieties of stone coal, of Yorkshire ; cannel coal, of Lancashire; culm, of Wales ; or anthracite, of mineralogists. The major part of Yorkshire coal is the slate coal of mineralogists. Having on a former occasion advanced the opinion that the Yorkshire Freestone is an estuary deposit, it being but a continuous member of the coal series, further research confirms that opinion, and goes to convince me that the Yorkshire Coal Field and its intermediate strata is one large estuary deposit; one of the strongest evidences being the general thinning of the respective strata to the east, which would bear out the idea that some large sluggish river or rivers had quietly deposited the contents of their turbid waters from the North-west by West. I know of no supposition but that of an estuary deposit, to account for the basin or spoon shape of coal formations, except the extravagant one of satellites, that have fallen to our earth as their primary. The loose floated materials becoming more solid would have a tendency to settle in the middle (as there would be less support in the centre) as we have often seen the basset edge left behind at a greater angle, the change must be allowed to be great and complete between the finishing deposition of the sandstone grit and the commence ment of the coal series. From whatever quarter the debris that forms the carboniferous sandstone of this district came, I think it must have been worn on some beach, by powerful drifts, rapid currents, glacial deposits, or the wild dash of some primeval ocean's successive storms, and perhaps the tidal billows of a comparatively inland sea. To me there seems no need to call in any great astronomical change to bring about a more settled state of things. The currents of this inland sea or estuary, by which the Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

79 granitic debris has flowed, and met the river water in uproar ious contention, would consequently agitate the very bottom at every ebb and flow of its tide, by which some change in the currents of the oceanic deposited debris of the rivers might begin to form a sandbank at the very junction ; and where these forces were equal, or their powers exhausted, this sand bank or bar would have a tendency to check the force of both. We have seen similar efiects in the change of currents in the drifting of snow. The continual accumulation would shut out the ocean, and convert the river waters into a sluggish estuary; and all future deposits would be supplied from the river or rivers through the varied deposits of more than 600 yards of strata, alternating with sandstone, shale, coal, and ironstone, &c. Just in proportion to the gain of the sandbank on the river's current, would be the dry land or the estuary covered with water. I think this is sitfficient to account for the varied strata without the hypothesis of an alternate earthquake, or volcanic upheaval and submergence. There is no need of an upheaval to cause dry land, as the silt deposited from the rivers would raise the delta, and a little addition to the sandbank or slight submergence would put the delta under water again. I have a great objection to multiply causes in nature when we have daily before us adequate phenomena. It has been customary to account for the coal strata by upheavals and depressions, but there is no evidence of violence from the deposit of the sandstone grit until the last member of the coal series was finished. The only evidence of upheaval is at the Permian period, when the backbone of England, as it is sometimes termed, was raised. No doubt it was at this period when our coal series was so disrupted. There is no appearance of any erupted matter in the Yorkshire Coal Field; but there are trap dykes in the Northumberland and Durham series. I have no wish to go into the salt or freshwater origin of the intermediate shales, Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

sandstones, &c., of the carboniferous strata. No doubt there are both. The fossil pecten of the Halifax and Sheffield bottom coal shales, denotes a mixture at least of saltwater, and the enormous mass of freshwater mussels, of the middle coal and ironstone beds of Shelf and Low Moor, are a strong evidence of the strata having been deposited in a lake or inland sea. I think the major part of the vegetation from which coal has been derived, has grown upon dry land, or in swampy lagoons, similar to the Cypress Swamps of the Delta of the Mississippi, described by Sir Charles Lyell ;* also in Mr. Hawkshaw's Heminis- cences of South America ; and the researches of Mr. E. W. Binney, who, with praiseworthy industry, has laboured to explain those curious trees, the Lepidodendron and Sigillaria, of which the coal is so largely composed in the Lancashire and Yorkshire beds. I suspect, however, the annual fall of the foliage has contributed more to the deposit than the stems themselves, the reed-like calamite has evidently been a water-plant, from its being found in such abundance in the black shale, rather than in the coal itself, though there are beds of coal on the Continent, largely composed of cala- mites.f Mr. Binney says, "where the plants grew and the strata " in which they are found, were no doubt deposited under water " and shew no evidence of being dry land ;" p. 162. " The " presence of the remains of bivalve shells and fish in cannel " coal clearly proves that it was formed under the water;" p. 163. " In the upper new red sandstone, of Western Bank, " near Runcorn, in Cheshire, we have the first evidence hitherto " discovered of dry land in England." Again he remarks, " There is no positive evidence of dry land before the tertiary " period." Sir R. I. Murchison observes, " It may be weU to " state that there is no geological difierence between stone * P. 334. of his Manual. + Manchester Philosophical Society, see vol. 13, p. 1C7. Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

" coal and culm or bituminous and common coal. They " are in fact mere mineral varieties of the same sub- " stance which occur in formations accumulated at "the same period."* Sir 0. Lyell, in his Manual, p. 333, quoting Liebeg and Bischoff, says, " The disengage- " ment of all the gases gradually transforms ordinary or " bituminous coal into anthracite; to which the various *' names of splint, glance, culm, and many others have been " given." Liebeg, in his Chemistry, gives the following analysis of Mineral coal: " Hydrogen 13, carbon 24," and states that it " appears to be produced by long-continued de- " composition of wood or wood-coal, by which carbonic " acid and water, and carburetted hydrogen are separated; " when the whole of the hydrogen is removed in the form " of carburetted hydrogen the residue must be anthracite, " which is nearly pure carbon." Professor Johnston, in his inaugural address to this Society, said " Cannel coal con- " tained one atom more water than cokeing coal," which is very correct. Dr. A. A. Hayes, United States, in a paper read at the Dublin Meetiag of the British Association, in 1857, has evidently been struck forcibly with the dLflS.culty to account for the conversion of bituminous coal into anthra cite. No coal tar being found in the vicinity of the beds, how is the absence of this material to be accounted for but by supposing that it has been originally a different kind of deposit ? Dr. Hayes details a course of experiments to illustrate his opinions, but the experiments were performed under a light atmosphere of gases, whereas the bituminous coal has an enormous weight of superincumbent strata. This, to me, appears a fatal objection to his experiments in proving the change of the coal after being deposited, as there should be springs of natural bitumen or petroleum near the cannel beds, if this theory be true.

* Silurian Systetn, vol. 1, p. 371. F Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021 82

Sir C. Lyell, in his Second Visit to America, vol. 1, p. 286, says, " I found on visiting the various localities of the " natural coke, that it was caused by the vicinity or contact " of volcanic rocks, greenstone, and basalt, as in the Durham " coal field." Mr. Buddie writes, ia the Transactions of the Jfatural History Society of Newcastle and Durham, vol. 1, p. 13, " That in some cases a cinder dyke converts the coal for " one him.dred yards into coke or smudge coal." Mr. Foster, in the same work, p. 48, remarks, " That the " coke should be specifically heavier than the coal," but accounts for it " from the extreme pressure it was under " when the Trappean dyke changed it, and passed other " matters into it as the gases were driven off." Mr. H. D. Rogers, in his work on the Geology of Pennsylvania, vol. 2, p. 809, says, " The causes of the different " degrees of de-bituminisation of the coal in different parts " of their range, I am disposed to attribute to the prodigious " quantity of intensely-heated steam and gaseous matter " emitted through the crust of the earth, by the almost ** infinite number of cracks and crevices which must have " been produced during the undulation and permanent " bending of the strata." Dr. Bevan, in the Geologist, vol. 2, p. 80, says, " I cannot " help imagining that the changes have been caused by trap • " rocks, far below the surface!^ and that the gradual disap- " pearance of the anthracitic tendency has been simply the " diminishing distance from the heat which has caused the ^ " change/ north crop coal anthracitic, while the '*upper " measures'are bituminous. I consider the reason to be that " the changes were subsequent to the deposition of the lower " measures, and prior to the upper ones." The authors of the Fossil Flora remark that three or four species of plants go to the formation of coal. One-half may Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

83 be said to be ferns, some firs, a few palms, a few species xm- known, and no exogens. One never differs in opinion, but with regret, from the ever-honoured name of Humboldt, but I do think a century is too long for the deposition of eight French lines; and, on the other hand, a century is too short for the nine-inch bed of coal at Bolton, with the large trees grown upon it. Mr. E.. Hunt says, " Without the light of the sun, no " tropical plant can be produced." But perhaps there may be some little error in requiring one great phenomenon to do what a great number of little disturbing causes may have effected. We know that the sun's rays are not required to produce that luxuriant, though it may be pale and almost flowerless, flora of our present woods, beneath the rich spreading oaks, elms, and ashes, on the steep slopes of our shaded glens, in the shadow of our dark pointed rocks, where the rays of the sun never shone, where annually rises the brake or common fern, with a variety of other annuals to the height of a man, and with a luxuriant compactness that makes it difficult to wade through them in the beginning of autumn. And if you work down to the roots of the present growing ferns, it will be found that many years are required to produce their partial decomposition. Perhaps rivers from the tropics, having connection with a similar stream to the gulf stream, hot springs, and certainly a more moist and extra quantity of carbon in the highly--charged atmosphere, may probably -produce these so-called tropical plants. But from whatever phenomena, causes, or length of time coal is in forming, I think the variety of minor disturbing causes is more consistent than calling to our aid the axial changes of our planet; for however slow we consider the formation of coal to have been, we must allow a very rapid deposition in some cases of the intermediate strata of shale and sandstone, as also bands of coal. For instance, the large fossil tree at Y2 Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

Low Moor could not have lived for the enormous time necessary for the deposition of all these surrounding strata, if not quickly deposited. It makes no difference whether the tree grows from the black bed coal, or is j&oated as a snag, with its heavy roots keeping it upright.* I think the most consistent theory to illustrate the forma tion of coal is in the low marshy islands, or level delta, in the mouths or estuaries of large rivers, similar to the Mississippi and Ganges, whose deltas are forming more than 300 miles out in the ocean, in a basin-shaped depression, as if the centre had receded. That it has been an extremely quiet deposit is evinced from there being no water-worn pebbles as large as an ordinary pea. Again, that the forests and under-wood have frequently grown on or near the place where they were submerged, there is I think sufficient evidence; as also that the vegeta tion was only partially decayed; and few evidences occur of a force of stream to float vegetable matter anything like the timber rafts of some of the large rivers of the present day. If there had been a sufficient force of stream it would have brought coarser materials than we find in our shales. By a careful examination, I believe it is quite possible to prove what coal is deposited from water, which is removed a short distance from where it grew ; and what has been embedded, comparatively dry, on the very place where it flourished. A stream, at the fall of the leaf, may float the decayed vegeta tion out to any varying distance without being decomposed, and the water may quietly filter through a similar deposit, and leave the accumulation of several seasons' leaves, in a

* Since this paper was read, it has been ascertained that the top of the tree was originally broken off at the period of the deposition of the shale, with which the interior is filled up, shewing very evidently that the vegetable tissues had been decomposed and washed away, leaving the bark to be converted into coal, and the centre a hollow cavity to bo filled up by the material which was last deposited. The main strata which surrounds the tree in sandstone. Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

85 scries of layers, as they get interrupted in their progress among the weeds, trees, and under-wood. In some places the water would, of necessity, be highly impregnated with decomposed vegetable matter, sufficient to destroy the lives of any small fish. The sedgy edges of different lagoons or marshes may be sufficiently open to allow the teeth or scales, or other remains of fish to pass through, as is found in camiel coal. As regards the formation of bituminous coal, however, a familiar illustration is furnished by observing a large hay rick which has been put together when the grass was too much saturated with moisture, owing to rain, after having been cut. In this state it is more liable to ferment than from the effects of its own sap, and in such instances the centre of the mass, if examined, will have the appearance of bituminous coal, similar to the Bradford better bed. Upon the top of this coal is from four to six inches of stone coal, which is a distinct deposit, and from water, self-evidently from this fact amongst others, that the upper part of the formation has more mineral matter in it than the lower. There is a gradation in the amount of silty matter which the water mixes with the surrounding vegetation, and con sequently a diversity is found in the composition of coal and the accompanying shales. AVhen some kinds of coal are burnt there remains what is provincially termed " white trub," of about one-third the original bulk, containing a greater amount of shale, and less carbon. In the shale above, when burnt, the residue is a fine red laminated material, so useful for macadamizing roads. In other cases, a fine laminated blueish shale remains, containing numerous impressions of leaves. When the coal and shales exhibit an even and laminated appearance, and split with smooth flat cleavage, containing impressions of leaves, I am of opinion that the vegetable masses have been floated in water a greater or less distance without sufficient chemical or mechanical action to decompose Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

86 the fibres and tissues. In the fermentation or chemical change that takes place in the process of crystallization, it is pretty evident electricity or magnetism has formed the cleavage in coal, as it runs very exact to 15 degrees west of the present magnetic pole; but the magnetic pole varies, and all the coal series are the same where this particular cleavage is distinct. It is well known, from a variety of experiments, that some plants decompose sooner in water than others; and hard-wood trees sooner than firs, fema, &c. The partially decomposed fibre of the hard-wood trees would, in some cases, be floated; in others left in the stagnant waters. These stagnant ponds would be very similar to those described by Hawkshaw, in his Reminiscences of South America, " where, in the commencement of a fresh, the turbid waters " were poured out as black as ink." In the regular mass of cannel coal, the crystalline structure so conspicuous in cokeing coal is wholly wanting, according to Lindley and Hutton, as quoted by Dr. Buckland. But this is not quite correct, as the crystalline structure is present, but changed into crystals of a larger size, which gives the idea that the vegetables have not been deposited in a mass but partially decomposed. I am of opinion that stone or cannel coal has been formed by a quantity of water charged with decaying vegetable matter, submerging a district in which partially decomposed and growing vegetables were present, and con taining a sufficient amount of acid to cause active fermenta tion, similar to the swamps described by Hawkshaw, for the wavy or undulated appearance of the coal indicates such a kind of action to have been in operation. I have seen a somewhat similar process going on in a partially stagnant pond, where a sufficient amount of vegetable decomposition had taken place for the liberation of gases that would support flame on the surface ; when this pond had been dried up I have seen, by cutting a section of the black sediment at Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021 87 the bottom, that it had the appearance of stone coal, and the properties of shale. A further illustration is afforded in a lower pond or lake, where the water has been dried up, and the lighter vegetable matter floated away by the upper stream. Some of the aquatic grasses have become imbedded in the mud or sediment, and there remain to undergo a further change under pressure, or become in process of time fossilized. Dr. Bevan speaks of the lower measures in the South Wales coal field as being anthracite, and the upper as being bituminous. At Popplewell, near Low Moor, however, just the reverse of this occurs, as below the anthracite there are four beds of bituminoTis coal, and in the cannel coal-bed there are two partitions of bituminous shale, which evidently indicate that the former has been deposited at three distinct periods. It is very common for one kind to run into the other, and it is this gradual transition that disproves the igneous agency suggested by Professor Rogers; and to me his steam theory is no explanation of the difficulties to be solved in accounting for the origin of the different varieties of coal, for when the materials are hermetically sealed up it is impossible on either theory to produce the change which is observable. At the bottom of one of the cannel coal-beds at Wigan, there is a bed of shale from one to two inches in thickness, and beneath this one or two inches of bituminous coal. In the neighbourhood of Batley there is a considerable amount of ironstone in the shales, which is almost composed of shells,—commonly called the cockle shell roof by the miners, and the mussel band of the geologists; this particular roof being over so many of the cannel beds, some of the miners imagine one is a necessary accompaniment of the other. The Middleton coal has also a similar roof. The prevalent idea is that bituminous coal was the only kind originally deposited; and that stone coal, anthracite, cannel, culm, splint, and glance coal, are the effects of heat Downloaded from http://pygs.lyellcollection.org/ by guest on October 2, 2021

88 changing the bituminous to the above-mentioned kinds. If so, we should naturally expect the coal near breaks to be more altered, whereas we laiow there is no diflference. When the water has been off for a few years, the admission of air through the interstices changes the colour of the iron pyrites from white to yellow. Now as we always find the pjTites to be white in fresh cuttings, it is demonstrative evidence that the metaUiferous deposit has never been exposed to the action of the atmosphere. Mr. H. D. Rogers,* says, " The striking fact that we " nowhere, not even in the most dislocated and disturbed " districts of the anthracite coal field, find any traces of true " igneous rocks, that by their contiguity to the coal coxdd " have caused the loss of its bitumen, is a circumstance in their " geology which goes far to confirm the truth of the hypothesis." We know from experience that cannel or stone coal is preferred for our domestic gas-manufactories, because it contains more pure carbon and hydrogen than bituminous coal does. If then it had been changed by heat, the hydrogen woidd have been driven ofi" at this early period, which we know is not the fact. Where trap dykes have been known to come up through or near the coal, it has either converted it into coke, cinder, or smudge coal; and where it has only disturbed and broken up the coal strata into small patches, and then mixed it up with other materials, allowing steam and water to pass through, there is no anthracitic tendency. I do not think, therefore, from my observations and a careful consideration of the subject, that when once bituminous coal is deposited, and a subsequent strata laid upon it, that it can be con verted into cannel coal by any process in nature with which wo are conversant, but that it is a distinct and original deposit from water, * Gcologj' of Pennsylvania, vol. 3, p, 801*.