Geology and Mineralogy considered with reference to Natural Theology/Chapter 19
CHAPTER XIX.
Proofs of Design in the Dispositions of Strata of the Carboniferous Order.
In reviewing the History and geological position of vegetables
which have passed into the state of mineral coal, we
have seen that our grand supplies of fossil fuel are derived almost exclusively from strata of the Transition series.
Examples of Coal in any of the Secondary strata are few
and insignificant; whilst the Lignites of the Tertiary formations,
although they occasionally present small deposites of
compact and useful fuel, exert no important influence an
the economical condition of mankind.[1]
It remains to consider some of the physical operations on the surface of the Globe, to which we owe the disposition of these precious Relics of a former world, in a state that affords us access to inestimable treasures of mineral Coal.
We have examined the nature of the ancient vegetables from which Coal derives its origin, and some of the processes through which they passed in their progress towards their mineral state. Let us now review some further important geological phenomena of the carboniferous strata, and see how far the utility arising from the actual condition of this portion of the crust of the globe, may afford probable evidence that it is the result of Foresight and Design.
It was not enough that these vegetable remains should have been transported from their native forests, and buried at the bottom of ancient lakes and estuaries and seas, and there converted into coal; it was further necessary that great and extensive changes of level should elevate, and convert into dry and habitable land, strata loaded with riches, that would for ever have remained useless, had they continued entirely submerged beneath the inaccessible depths, wherein they were formed; and it required the exercise of some of the most powerful machinery in the Dynamics of the terrestrial globe, to effect the changes that were requisite to render these Elements of Art and Industry accessible to the labour and ingenuity of man. Let us briefly examine the results that have been accomplished.
The place of the great Coal formation, in relation to the other series of strata, is shown in our first section (Pl. l. Fig. 14.) This ideal section represents an Example of dispositions which are repeated over various areas upon the crust of the Globe.[2]
The surface of the Earth is found to be covered with a series of irregular depressions or Basins, divided from one another, and sometimes wholly surrounded by projecting portions of subjacent strata, or by unstratified crystalline rocks, which have been raised into hills and mountains, of various degrees of height, direction and continuity. On either side of these more elevated regions, the strata dip with more or less inclination, towards the lower spaces between one mountain range and another. (See Pl. 1.)
This disposition in the form of Troughs or Basins, which is common to all formations, has been more particularly demonstrated in the Carboniferous Series, (See Pl. 65. Fig. 1, 2, 3.) because the valuable nature of beds of Coal often causes them to be wrought throughout their whole extent.
One highly beneficial result of the basin-shaped disposition
of the Carboniferous strata has been, to bring them all to
the surface around the circumference of each Basin, and to
render them accessible, by sinking mines in almost every
part of their respective areas; (See Pl. 65. Figs. 1, 2, 3.)
An uninterrupted inclination in one direction only, would
have soon plunged the lower strata to a depth inaccessible
to man.
The Basin of London, (Pl. 68.) affords an example of a similar disposition of the Tertiary strata reposing on the Chalk. The Basins of Paris, Vienna, and of Bohemia, afford other examples of the same kind. (See Pl. 1. Figs. 24—28.)
The Secondary and Transition strata of the central and North Western districts of England, are marginal portions of the great geological Basin of Northern Europe; and their continuations are found in the plains, and on the flanks of mountain regions on the Continents.[3]
These general dispositions of all strata in the form of Troughs or Basins have resulted from two distinct systems of operations, in the economy of the terraqueous globe; the first producing sedimentary deposites, (derived from the materials of older rocks, and from chemical precipitates,) on those lower spaces into which the detritus of ancient elevated regions was transported by the force of water; the second raising these strata from the sub-aqueous regions in which they were deposited, by forces analogous to those whose effect we occasionally witness, in the tremendous movements of land, that form one of the phenomena of modern Earthquakes.
I am relieved from the necessity of entering into details respecting the history of the Coal Fields of our own country, by the excellent summary of what is known upon this interesting subject, which has recently been given in a judicious and well selected anonymous publication, entitled The History and Description of Fossil Fuel, the Collieries, and Coal Trade of Great Britain. London, 1835.
The most remarkable accumulations of this important vegetable production in England are in the Wolverhampton and Dudley Coal Field, (Pl. 65, Fig. 1,) where there is a bed of coal, ten yards in thickness. The Scotch Coal field near Paisley presents ten beds, whose united thickness is one hundred feet. And the South Welsh Coal Basin (Pl. 65, Fig-2,) contains, near Pontypool, twenty-three beds of coal, amounting together to ninety-three feet.
In many Coal fields, the occurrence of rich beds of iron ore in the strata of slaty clay, that alternate with the beds of coal, has rendered the adjacent districts remarkable as the site of most important Iron foundries; and these localities, as we have before stated, (p. 65,) usually present a further practical advantage, in having beneath the Coal and Iron ore, a substratum of Limestone, that supplies the third material required as a flux to reduce this ore to a metallic state.
Our section, Pl. 65, Fig. 1, illustrates the result of these geological conditions in enriching an important district in the centre of England, near Birmingham, with a continuous succession of Coal mines, and Iron foundries. A similar result has followed from the same causes, on the north-east frontier of the enormous Coal basin of South Wales, in the well-known Iron foundries, near Pontypool and Merthyr Tydfil,[4] (See Pl. 65, Fig. 2.) The beds of shale in the lower region of this coal field are abundantly loaded with nodules of argillaceous iron ore, and below these is a bed of millstone grit capable of enduring the fire, and used in constructing the furnaces; still lower is the limestone necessary to produce the fusion of the ore. Pl. 65, Figs. 1, 2.
The great iron foundries of Derbyshire, Yorkshire, and the south of Scotland, afford other examples of the beneficial results of a similar juxtaposition, of rich argillaceous iron ore and coal.
"The occurrence of this most useful of metals," says Mr. Conybeare,[5] “in immediate connexion with the fuel requisite for its reduction, and the limestone which facilitates that reduction, is an instance of arrangement so happily suited to the purposes of human industry, that it can hardly be considered as recurring unnecessarily to final causes, if we conceive that this distribution of the rude materials of the earth was determined with a view to the convenience of its inhabitants."
Let us briefly consider what is the effect of mineral fuel, on the actual condition of mankind. The mechanical power of coals is illustrated in a striking manner, in the following statement in Sir J. F. W. Herschel's admirable Discourse on the study of Natural Philosophy, 1831, p. 59.
"It is well known to modern engineers that there is virtue in a bushel of coals, properly consumed, to raise seventy millions of pounds weight a foot high. This is actually the average effect of an engine at this moment working in Cornwall.
The ascent of Mont Blanc from Chamouni is considered, and with justice, as the most toilsome feat that a strong man can execute in two days. The combustion of two pounds of coal would place him on the summit."
The power which man derives from the use of mineral coal, may be estimated by the duty[6] done by a pound, or any other given weight of coal consumed in working a steam engine; since the quantity of water that the engine will raise to a given height, or the number of quarters of corn that it will grind, or, in short, the amount of any other description of work that it will do, is proportionate to that duty. As the principal working of mineral veins can only be continued by descending deeper every year, the difficulty of extracting metals is continually on the increase, and can only be overcome by those enlarged powers of draining which Coal, and the steam engine, alone supply. It would be quite impossible to procure the fuel necessary for these engines, from any other source than mineral coal.
The importance of Coal should be estimated, not only by the pecuniary value of the metals thus produced, but by their further and more important value when applied to the infinitely varied operations and productions of machinery and of the arts.
It has been calculated that in this country about 15,000
steam engines are daily at work; one of those in Cornwall
is said to have the power of a thousand horses,[7] the power
of each horse, according to Mr. Watt, being equal to that
of five and a half men; supposing the average power of
each steam engine to be that of twenty-five horses, we
have a total amount of steam power equal to that of about
two millions of men. When we consider, that a large proportion
of this power is applied to move machinery, and
that the amount of work now done by machinery in England,
has been supposed to be equivalent to that of between
three and four hundred millions of men by direct labour,
we are almost astounded at the influence of Coal and Iron
and Steam, upon the fate and fortunes of the human race.
"It is on the rivers," (says Mr. Webster,) "and the boatman
may repose on his oars; it is in highways, and begins to
exert itself along the courses of land conveyances; it is at
the bottom of mines, a thousand (he might have said, 1800)
feet below the earth's surface; it is in the mill, and in the workshops of the trades. It rows, it pumps, it excavates, it
carries, it draws, it lifts, it hammers, it spins, it weaves, it
prints."[8]
We need no further evidence to show that the presence of coal is, in an especial degree, the foundation of increasing population, riches, and power, and of improvement in almost every Art which administers to the necessities and comforts of Mankind. And, however remote may have been the periods, at which these materials of future beneficial dispensations were laid up in store, we may fairly assume, that, besides the immediate purposes effected at, or before the time of their deposition in the strata of the Earth, an ulterior prospective view to the future uses of Man, formed part of the design, with which they were, ages ago, disposed in a manner so admirably adapted to the benefit of the Human Race.
- ↑ Before we had acquired by experiment some extensive knowledge of the contents of each series of formations which the Geologist can readily identify, there was no à priori reason to expect the presence of coal in any one Series of strata rather than another. Indiscriminate experiments in search of coal, in strata of every formation, were therefore desirable and proper, in an age when even the name of Geology was unknown; but the continuance of such Experiments in districts which are now ascertained to be composed of non-carboniferous strata of the Secondary and Tertiary Series, can no longer be justified, since the accumumulated experience of many years has proved, that it is only in those strata of the Transition Series which have been designated as the Carboniferous Order, that productive Coal-mines on a large scale have ever been discovered.
- ↑ The Coal Formation is here represented as having partaken of the same elevator movements, which have raised the strata of all formations towards the mountain Ridges, that separate one basin from another basin.
- ↑ The section (Pl. 66. Fig. I.) shows the manner in which the Strata of the Transition Series are continued downwards between the Coal formation and the older members of the Grauwacke formation through a series of deposites, to which, Mr. Murchison has recently assigned the name of the "Silurian system.". This Silurian System is represented by No. 11, in our Section, Fig. I. The recent labours of Mr. Murchison in the border counties of England and Wales have ably filled up what has hitherto been a blank page, in the history of this portion of the vast and important Systems of rocks, included under the Transition series; and have shown us the links which connect the Carboniferous system with the older Slaty rocks. The large group of deposites to which he has given the appropriate name of Silurian system, (as they occupy much of the Territory of the ancient Silures,) admits of a four-fold division, which is expressed in the section Pl. 66. Fig. 1. This section represents the exact order of succession of these Strata in a district, which must henceforth be classic in the Annals of Geology.
In September, 1835, I found the three uppermost divisions of this system, largely, developed in the same relative order of succession on the south frontier of the Ardennes, between the great Coal formation and the Grauwacke. See Proceedings of the Meeting of the Geological Society of France at Mézieres and Namur, Sep. 1835, (Bulletin de Ia Société Géologique dc France, Tom. VII.) The same subdivisions of the Silurian system, maintain their relative place and importance over a large extent of the mountainous district of the Eifel, between the Ardennes and the Valley of the Rhine; and are continued East of the Rhine through great part of the duchy of Nassau. (See Stiffts Gebirgs-Karte, von dem Herzogthum-Nassau. Wiesbaden, 1831.)
- ↑ In the Transactions of the Natural History Society of Northumberland, Durham, and Newcastle, vol. i. p. 114, it is stated by Mr. Foster, that the quantity of iron annually manufactured in Wales is about 270,000 tons, of which about three-fourths are made into bars, and one-fourth sold as pigs and castings. The quantity of coal required for its manufacture will be about five tons and a half, for each ton of iron. The annual consumption of coals by the iron works will therefore be about 1,500,000 tons. The quantity used in the smelling of copper ore imported from Cornwall, in the manufacture of tin plate, forging of iron for various purposes, and for domestic uses, may be calculated at 350,000 tons, which makes altogether the annual consumption of coal in Wales 1,850,000 tons. The quantity of iron manufactured in Great Britain in the year 1827 was 690,000 tons. The production of this immense quantity was thus distributed,
TONS. FURNACES. In Staffordshire 216,000 95 Shropshire 78,000 31 S. Wales 272,000 90 N. Wales 24,000 12 Yorkshire 43,000 24 Derbyshire 20,500 14 Scotland 36,500 18 690,000 284 - ↑ Geology of England and Wales, p. 333.
- ↑ The number of pounds raised, multiplied by the number of feet through which they are lifted, and divided by the number of bushels of coal (each weighing eighty-four pounds) burnt in raising them, gives what is termed the duty of a steam engine, and is the criterion of its power. (See an important paper on improvements of the steam engine, by Davies Gilbert, Esq. Phil. Trans. 1830, p. 121.)
It is stated by Mr. J. Taylor, in his paper on the duty of steam engines, published in his valuable Records of Mining, 1829, that the power of the steam engine has within the last few years been so advanced by a series of rapid improvements, that whereas, in early times, the duty of an atmospheric engine was that of 5,000,000 pounds of water, lifted one foot high by a bushel of coal, the duty of an engine lately erected at Wheal Towan in Cornwall, has amounted to 87,000,000 pounds; or, in other words, that s series of improvements has enabled us to extract as much power from one bushel, as originally could be done from seventeen bushels of coal. Thus, through the instrumentality of coal as applied in the steam engine, the power of man over matter has been increased seventeen fold since the first invention of these engines; and increased nearly threefold within twenty years.
There is now an engine at the mines called the Fowey Consols in Cornwall, of which Mr. Taylor considers the average duty, under ordinary circumstances, to be above 9,000,000; and which has been made to lift 97,000,000 lbs of water one foot high, with one bushel of coals.
The effect of these improvements on the operations of mines, in facilitating their drainage, has been of inestimable importance in extracting metals from depths which otherwise could never have been reached. Mines which had been stopped from want of power, have been reopened, others have been materially deepened, and a mass of mineral treasure has been rendered available, which without these engines must have been for ever inaccessible.
It results from these rapid advances in the application of coal to the production of power, and consequently of wealth, that mining operations of vast importance, have been conducted in Cornwall at depths till lately without example, e. g. in Wheal Abraham, at 242 fathoms, at Dolcoath at 235 fathoms, and in the Consolidated Mines in Gwennap at 290 fathoms, the latter mines giving daily employment to no less than 2,500 persons.
In the Consolidated Mines, the power of nine steam engines, four of which are the largest ever made, having cylinders ninety inches in diameter, lifts from thirty to fifty hogsheads of water per minute, (varying according to the season) from an average depth of 230 fathoms. The produce of these mines has lately amounted to more than 20,000 tons of ore per annum, yielding about 2,000 tons of fine copper, being more than one seventh of the whole quantity raised in Britain. The levels or galleries in these mines extend in horizontal distance a length of about 43 miles. (See J. Taylor's account of the depths of mines, third report of British Association, 1833, p. 428.)
Mr. J. Taylor further states, (Lond. Edin. Phil. Mag. Jan. 1836, p. 67) that the steam engines now at work in draining the mines in Cornwall, are equal in power to at least 44,000 horses, one sixteenth part of 3 bushel of coals performing the work of a horse.
- ↑ When Engineers speak of a 25 horse Engine, they mean one which would do the work of that number of horses constantly acting, but supposing that the same horses could work only 8 hours in every 24, there must be 75 horses kept at least to produce the effect of such an Engine.
The largest Engine in Cornwall may, if worked to the full extent, be equal to from 300 to 350 horse power, and would therefore require 1000 horses to be kept to produce the same constant effect. In this way it has been said than an Engine was of 1000 horse power, but this is not according to the usual computation.
Letter from J. Taylor, Esq. to Dr. Buckland.
- ↑ As there is no reproduction of Coal in this country, since no natural causes are now in operation to form other beds of it; whilst, owing to the regular increase of our population, and the new purposes to which the steam-engine is continually applied, its consumption is advancing at a rapid accelerating rate; it is of most portentous interest to a nation, that has so large a portion of its inhabitants dependent for existence on machinery, kept in action only by the use of coal, to economize this precious fuel. I cannot, therefore, conclude this interesting subject without making some remarks upon a practice which can only be viewed in the light of a national calamity, demanding the attention of the legislature.
We have, during many years witnessed the disgraceful and almost incredible fact, that more than a million chaldrons per annum, being nearly one-third part of the best coals produced by the mines near Newcastle, have been condemned to wanton waste, on a fiery heap perpetually blazing near the mouth of almost every coal-pit in that district.
This destruction originated mainly in certain legislative enactments, providing that Coal in London should be sold, and the duty upon it be rated, by measure, and not by weight. The smaller Coal is broken, the greater the space it fills; it became, therefore, the interest of every dealer in Coal, to buy it of as large a size, and to sell it of as small a size as he was able. This compelled the Proprietors of the Coal-mines to send the large Coal only to market, and to consign the small Coal to destruction.
In the year 1830, the attention of Parliament was called to these evils; and pursuant to the Report of a Committee, the duty on Coal was repealed, and Coal directed to be sold by weight instead of measure. The effect of this change has been, that a considerable quantity of Coal is now shipped for the London Market, in the state in which it comes from the pit; that after landing the cargo, the small coal is separated by screening from the rest, and answers as fuel for various ordinary purposes, as well as much of the Coal which was sold in London before the alteration of the law.
The destruction of Coals on the fiery heaps near Newcastle, although diminished, still goes on, however, to a frightful extent, that ought not to be permitted; since the inevitable consequence of this practice, if allowed to continue, must be, in no long space of time, to consume all the beds nearest to the surface, and readiest of access to the coast; and thus enhance the price of Coal in those parts of England which depend upon the Coal-field of Newcastle for their supply; and finally to exhaust this Coal-field, at a period, nearer by at least one-third, than that to whichit would last, if wisely economized, (See Report of the Select Committee of the House of Commons, on the state of the Coal Trade, 1830, page 242, and Bakewell's Introduction to Geology, 1833, page 183 and 543.)
We are all fully aware of the impolicy of needless legislative interference; but a broad line has been drawn by nature between commodities annually or periodically reproduced by the Soil on its surface, and that subterranean treasure, and sustaining foundation of Industry, which is laid by Nature in strata of mineral Coal, whose amount is limited, and which, when once exhausted, is gone for ever. As the Law most justly interferes to prevent the wanton destruction of life and property, it should seem also to be its duty to prevent all needless waste of mineral fuel; since the exhaustion of this fuel would irrecoverably paralyze the industry of millions. The tenant of the soil may neglect, or cultivate his lands, and dispose of his produce, as caprice or interest may dictate; the surface of his fields is not consumed, but remains susceptible of tillage by his successor; had he the physical power to annihilate the Land, and thereby inflict an irremediable injury upon posterity, the legislature would justly interfere to prevent such destruction of the future resources of the nation. This highly favoured Country, has been enriched with mineral treasures in her strata of Coal, incomparably more precious than mines of silver or of gold. From these sustaining sources of industry and wealth let us help ourselves abundantly, and liberally enjoy these precious gills of the Creator; but let us not abuse them, or by wilful neglect and wanton waste, destroy the foundations of the Industry of future Generations.
Might not an easy remedy for this evil be found in a Legislative enactment, that all Coals from the Ports of Northumberland and Durham, should be shipped in the state in which they come from the Pit, and forbidding by high penalties the screening of any Sea-borne Coals before they leave the port at which they are embarked. A Law of this kind would at once terminate that ruinous competition among the Coal owners, which has urged them to vie with each other in the wasteful destruction of small Coal, in order to increase the Profits of the Coal Merchants, and gratify the preference for large Coals on the part of rich consumers; and would also afford the Public a supply of Coals of every price and quality, which the use of the screen would enable him to accommodate to the demands of the various Classes of the Community.
A farther consideration of national Policy should prompt us to consider, how far the duty of supporting our commercial interests, and of husbanding the resources of posterity should permit us to allow any extensive exportation of Coal, from a densely peopled manufacturing country like our own; a large proportion of whose present wealth is founded on machinery, which can be kept in action only by the produce of our native Coal Mines, and whose prosperity can never survive the period of their exhaustion.