A Treatise on Geology/Chapter 11
CHAP XI.
THE favour with which geology has been received
into the circle of modern science, is mainly attributable
to its all-pervading and expanded harmony with other
branches of study, with popular sources of intellectual
enjoyment, and important commercial and agricultural
applications. Public taste changes from time to time
its objects of special attention, but not capriciously nor
unjustly; and geology has been advanced rapidly
during the last 10, 20, and 30 years, because its march
had been previously retarded, and because in its progress
all other parts of the great contemplation of
nature were deeply interested. The preceding pages
have given illustration of the real and mutual dependence
of geology, and the parts of human study which
relate to the living forms, habits, and history of plants
and animals,—the energies resident in and acting
among the atoms of matter—the forces which operate
in the air and water above, and in the rocky depths
below the surface of the earth—the constitution and
phenomena of the planets, and the state of the ethereal
spaces in which suns and planets move, at distances
which are beyond expression and conception. Considered
in these aspects, geology is a boundless study;
and yet only the indolent will turn away from its
allurements, since every part of its truths is full of
rare and profitable results.
It is sometimes, not very fairly, objected to modern geology, that the superior accuracy and power of research which it has turned on the ancient mysteries of nature, has been purchased at the cost of the plainness and accessibility which it is imagined should attend the interpretation of phenomena so obvious as those in the crust of the earth: but in reality no branch of the study of external nature is less loaded with technical impediments. The thousands of organic remains which have been cited as witnesses of the ancient character of land and sea, are called by the names which have been assigned them by zoology and botany; the mineralogist has given the titles of rocks and individual minerals; chemists and mechanicians supply the laws of corpuscular actions and movements among the larger masses of matter; and all these parts of knowledge must enter into the consideration of any one who may think himself equal to propose a general geological theory. But equal difficulties and not greater facilities belong to the highest paths in every other branch of knowledge; while in the collecting of facts for the foundation and confirmation of such a theory, men of ordinary mental power and application can hardly fail to be usefully and most agreeably occupied; nor do they need, for this valuable purpose, to become profoundly versed in any other art or science than that of observation.
At the same time it is to be stated, that observations
of most value in every field of human inquiry, have
been made by those whose minds, previously directed
to the true bearings of the questions in progress, have
been ready to perceive and embrace the occasion of
adding new and appropriate truths to the stock already
gathered. It is therefore most important that as much
of the interpretation of geological phenomena as can be
correctly advanced, should be openly and frequently
communicated to the public at large; since by this
means the mass of ignorance and prejudice, which it is
the function of science to remove, will be attacked at
all points, and thousands of valuable facts disclosed in
railways and canals, in wells, collieries, and mines, will
be saved from that oblivion into which all the merely
experimental acquirements of practical men too easily
and quickly fall.
There is, besides, another class of persons to whom these remarks may be useful. The body of mere travellers who now hurry over the globe on the wings of steam, would be converted into valuable pioneers for the yet unexplored wastes of geology, could they be made to see and feel the power which is possessed by every voyager to contribute, though not so abundantly as the prince of travellers, Humboldt, to the stores of natural science. In meteorology, magnetism, zoology, and botany, as well as geology, the officers of the army and navy have begun to distinguish themselves; and it is with a view to extend this honourable love of knowledge, by showing some of the popular and economical applications of geology, that the following remarks and suggestions are written.
Aspect of the Earth's Surface.
Most unjustly has Natural History been accused of favouring merely minute and curious inquiries into the small, parts of creation, and of neglecting the larger views and contemplations which delight the man of taste and refined feeling. Whoever reads the works of Pallas, Humboldt, White, or, to come more nearly to our subject, converses with Sedgwick or examines the pages of Lyell, will acknowledge the error of this misrepresentation. Mr. Murchison in his work now published[1], has vindicated geology from this aspersion, and, while exploring with extraordinary zeal and minuteness the recesses of the border of Wales, has stopped to admire the feudal ruins and trace the smiling landscapes of that interesting region. Often has it occurred to ourselves, while traversing other districts not less rich in curious geological truth, to rejoice in the new knowledge and deeper love of nature which an investigation into the ancient causes of the present aspect of the land and sea had imparted; the puny hammer has dropped from our hands while contemplating the mighty waste produced by atmospheric variations on rocks which in our monumental buildings have stood the injuries of a thousand years; and we have turned from the perishing granite of Arran, or the bleached and weathered limestones of the Wye or the Meuse, to compare these proofs of partial and slow decay with the deep chasms and wide valleys which now diversify the surface of the land, and to inquire whether the same causes long continued, or other causes operating with greater intensity, have given to the earth this
"Pleasure situate in hill and dale."
The intellectual enjoyment of contrasted scenes, far from being diminished by the application of scientific methods of research into the causes of their differences, is, in fact, very incomplete without such addition; and few persons really do feel gratification in contemplating the beauties of nature, or the miracles of art, who have not learned to associate with the mere perceptions of form and colour, circumstances of higher and deeper interest for the mind.
Outline of Land and Sea.
One of the circumstances most obvious to a geologist, but most unintelligible to an ordinary observer, is the real and necessary dependence of the form and aspect of the earth's surface on the quality and arrangement of the rocky materials beneath. If the reader will place before him a coloured geological map of the British Islands[2], he will easily perceive the truth of this statement, by comparing the outline of the coast with the geological structure. There is a remarkable tendency in the English and Scottish coasts to run out into long points and retire into bays in lines more or less directed from south-west to north-east, as the long projections of Cornwall, Cardiganshire, Carnarvonshire, the Isle of Man, Galloway, Isla, the Hebrides, Orkneys, Aberdeenshire, Norfolk, plainly denote. The direction from N.E. to S.W. is the most prevalent one in England, Wales, and Scotland; in Ireland, several directions of strata appear, and the tendency to form promontories and bays is correspondingly varied.
Passing to more precise inquiry, we find that the position of the rocks in anticlinal and synclinal axes is a fertile source of local and general irregularity of outline. The Hebrides may be viewed as the tops of one long anticlinal range of gneiss mountains; nearly parallel to these are the loftier chains of the North-western Highlands, from Mull to Caithness, and the broader band of the Grampians, both running out into vast projections; while between these severally, in synclinal lines and newer strata, are a parallel channel of the sea, and a parallel vale which unites the opposite bays of the Moray Frith and Loch Linnhe. Another anticlinal ridge in a north-east and south-west direction forms the Lammermuir and other mountains from St. Abb's Head to the Mull of Galloway, and between these and the Grampians sinks the synclinal axis of the retiring coasts of the Forth and Clyde. In all there cases, the outline of land and sea is obviously the necessary result of the intersection of parallel ridges and hollows by the general sea line.
Farther south we find, on the eastern coast, the influence of unequal hardness in the rocks which front the sea. The straight line of the Northumberland coast presents a series of carboniferous rocks which waste slightly and equally; the hollow at the mouth of the Tees is in soft and perishing red sandstones and clays; the prominent points of Whitby Abbey, Scarborough Castle, and Flamborough Head are feebly guarded by oolitic limestones and sandstones, and hard chalk; while the bays of Filey and Bridlington are excavated principally in diluvial clays and sands. Vast areas of clays underlay the wide levels of the Fens of Lincolnshire and Cambridgeshire, which mark the ancient in draught of the North Sea; while the chalk of Norfolk and Kent makes hold projections on each side of the tertiary clays and sands of the Basin of London. Here, however, we have again to notice the influence of the position of the strata; for the Thames passes to the sea in a synclinal trough, and thus its deep indentation is readily explained. The Straits of Dover and Boulogne depend for their narrowness on the anticlinal ridge of the Weal den; parallel to this is the anticlinal fault of the Isle of Wight and Purbeck, by which these districts are extended east and west; and between the two runs the Hampshire trough, which is now filled in the deepest parts by the channel of the Solent.
It appears unnecessary to extend these remarks on the outline of the land and sea, since every where the same principles give equally certain explanations both on a large and small scale. We may therefore turn to consider the interior of a country like England.
Undulations of the Interior.
Geographers have noticed, as a fact of frequent occurrence, the prevalence of bold coasts and high land on the western sides of continents and islands, and of sandy shores and low countries on their eastern boundaries. This is true with regard to a large part of the American continent, England, Norway, Hindostan, and other districts; and it may hereafter be found of importance in geological theory. In England, the existing information on the distribution of strata, and lines of subterranean movement, is quite sufficient to give the clue to this peculiarity of structure, and at the same time to explain the exceptions to the general rule.
With the exception of the anticlinal ridges of the Isle of Wight and the Wealden, a swelling under the Yorkshire oolites, and the great faults of the valley of the Tyne, no subterranean disturbance of great importance breaks the easy slope of the secondary strata in the eastern parts of England. But on the western boundary of the island, a very different scene appears. Bold anticlinal axes, and other dislocations without number, undulate the stratification of Cornwall and Devon, South and North Wales, the western sides of Derbyshire, Yorkshire, and the almost insulated group of the Cumbrian mountains; and these include the points of greatest elevation, and the ridges of boldest rocks, both inland and on the sea coast, which England has to boast.
Most of the great dislocations here noticed occurred in early geological periods, and besides the local elevations which they have imparted to the western districts of England, they had the effect of entirely changing the bed of the sea, in such a manner as to cause general slopes to the eastward, which were not reversed during the whole subsequent periods of geology. Hence arises another peculiarity in physical geography, which has been long known to inquirers and surveyors, viz. the alternation of ridges and hollows, on lines directed north-eastward and south-westward through a large portion of the secondary as well as primary districts of England.
To describe instances of so well known a truth would be very unnecessary; but we may remark in North Wales the alternation of the Menai Straits, the Snowdonian Chain, the Bala Vale, and the Berwyn Mountains, all ranging north-east and south-west, as very illustrative of the fact and the explanation. In South Wales Mr. Murchison has traced the same connection of anticlinal axes and hilly ground; the great hollow which crosses Devonshire from west to east, is formed in a trough of the strata between the Dartmoor and Exmoor ridges; Mendip is an anticlinal rock ranging east and west; Malvern, a narrow chain passing north and south; Charnwood Forest runs west north-west.
The effect of these various elevations on the ancient strata in the western parts of England, is sensible in the very general declivity to the east or south-east which belongs to the carboniferous, oolitic, and cretaceous strata. And as among these the materials present unequal resistance to the atmospheric agents of destruction, and waste unequally, long chains of limestone hills alternate with wide parallel vales of clay, and render a journey from London to Bath, Worcester, or Newark, a succession of similar vales and hills. One tertiary vale, one cretaceous ridge, one or more vales in clay, alternating with as many ridges of oolite, are crossed on each of these roads in the same order of succession. These parallel vales are frequently, though not always, filled for parts of their length by great rivers, like the Isis or the Thames; and investigation easily shows that the hollows are not the result of fluviatile action, but of some earlier and greater force of nature, which excavated the wide vale in which the river now finds a narrow channel. There can be little room for doubt that the currents and tides of the sea, in action at the time of the elevation of the land from its ancient level, were the instruments by which the softer strata were worn away, and thus, with a considerable approach to accuracy, we may assert, in general terms, that by direct and indirect effects, the leading features of the earthy surface are distinctly referrible to the force of interior heat.
Scenery.
The charm of rural landscapes, the romantic pleasure of mountain prospects, and sequestered dells and waterfalls, is but feebly appreciated by those who, unacquainted with the principles of art, have not learned to perceive in all the works of nature the operation of law, and to trace in all the diurnal aspect of creation the effect of many preceding revolutions. The greater features of physical geography are explained by subterranean movements and their consequences; the minuter proportions, which are the proper province of pictorial art, are partly due to other circumstances. The richness or desolation of countries, besides the obvious influence of elevation and climate, proximity to the sea, or snowy mountains, is not a little dependent on the chemical quality, and texture of the subjacent rocks, for these, by their decomposition, have furnished, in general, the soil; which does not indeed feed, but is a channel of nutrition for the vegetable world.
Let any one compare, for example, the glorious trees and rich pastures of the vales of Severn and Avon, situated on lias and red marl, with the stunted oaks and poor herbage of a great part of the broad vale of York, which is filled by gravel drifted upon the same red marls and lias; or, in the vale of York itself, contrast the finely wooded and fertile region about Thirsk, where these strata come to the day, with the naked plains between North Allerton and the Tees, and he will see the importance of attending to geology in estimating the agricultural condition of a country. Through a great part of England, the various ranges of secondary limestones have characters of outline and surface by which they may be fully represented in a painting. Whoever has admired the Sussex Downs, or Yorkshire Wolds, will seldom fail to recognise, in other situations, those broad, rounded, and gracefully swelling hills melting into gentle hollows, that smooth short herbage, and that pleasing though dry and treeless surface, which belongs to the chalk of most parts of England. Different from these, in many respects, are the tracts of the Gloucestershire and Oxfordshire oolites, with their tabular summits and intervening woody vales of clay, and the older limestones below the coal wear other and bolder aspects, and all are different from the intersecting outlines and rugged surfaces of the primary strata of slate, mica schist, and gneiss.[3]
But besides these general characters of district scenery, it is a familiar truth that every different kind of rock has peculiar forms in the mass, particular arrangements of the structural lines, and even modes of wasting, and vegetable accompaniments, which are often attended to as pictorial effects, but which furnish to the geologist the further enjoyment which arises from inquiry into the cause. By a knowledge of the divisional structures of rocks[4], a geologist can very frequently determine at a distance the nature of a rock, distinguish basalt from slate, limestone from sandstone; and thus his sphere of gratification from scenery is enlarged, his perception of the minuter shades and lights of the landscape become more vivid, and his memory of pa&t combinations more enduring.
It is needless to pursue this subject. Who has ever imagined that the ruins of a rich monastic edifice are less admired by the architect who strives to discover the principles of its construction and the theory of its decoration, or the antiquarian who searches the records of its overthrow, than by those who merely gaze on these masterpieces of the building art, without striving to penetrate the mystery which time and the ravages of man have gathered round the ancient aisles and turrets? Geologists are, as Cuvier felt and said, "antiquaries of a new order," and their enjoyment of the fair scenes of the earth which typify the will of their Creator, partakes of the same high and solemn character which belongs to the intelligent contemplation of the noblest monuments of ancient art.
Economical Applications of Geology.
Agriculture.
Agriculture, which, of all branches of human industry, seems most directly dependent on the qualities of soil and substrata, has been hitherto very little benefited by the progress of geological science. Perhaps the expectations of those speculative farmers who desire to turn to good account the discoveries of botanical physiology, vegetable chemistry, and geology, require some better direction to attainable objects, than botanists, chemists, or geologists, are likely to furnish. That plants, by growing frequently on the same spot, poison the soil for themselves, though not for other plants, appears a reasonable generalization of well known facts: that certain successions of crops are best fitted for particular soils, is incompletely known by experience, and may be turned to a profitable account by the union of botanical and chemical research.
The chemical quality of soils, to judge from a superficial examination, appears to be of real importance. Why else, amidst the heather which covers thousands of acres in the moorlands of the north of England, should there appear not one plant of Dutch clover, though upon the removal of the heath, and the application of quick lime, this plant springs up in abundance? Why else does Cistus belianthemum love the calcareous soil, the oak delight in stiff clay, the birch and larch flourish on barren sand? Yet, to all the conclusions drawn from facts of this nature, exceptions arise, and the relation of the soil to moisture appears quite as fertile and general a source of difference of vegetation and productiveness, as any peculiarity of chemical constitution. We once took the pains to notice every species of plant growing on a purely calcareous soil 2000 feet above the sea, on Cam fell in Yorkshire, and among them all, it appeared that not one was commonly supposed peculiar to limestone.
It appears to us that it is chiefly by their various power of conducting moisture from the surface that rocks of different kinds influence the soil above them; and this is a circumstance which is sometimes interesting to the farmer, for another reason. It is. not doubtful that in many cases there is a possibility of draining land which is under laid at some small depth by a jointed calcareous rock, just as by sinking a few feet in a mining country, through clay to limestone, the whole drainage of a mine may often be passed downwards, through the natural channels of the rocks.
One of the most obvious sources of advantage to the farmer from an acquaintance with the distribution of mineral masses, is the facility with which in many instances the injurious effect of small springs coming to the surface may be obviated. The theory of the earth's internal drainage is so simple, that every man of common sense would be able to drain his lands upon sure principles, or else to know precisely why it cannot be drained, if he were to become so much of a geologist, as to learn what rocks existed under his land, at what depth, and in what positions. Springs never issue from stratified masses, except from reservoirs some how produced in jointed rocks—and at the level of the overflow of these subterranean cavities. Faults in the strata very frequently limit these reservoirs, and determine the points of efflux of the water. Let those faults be ascertained, or the edge of the jointed rock be found, the cure of the evil is immediate. But some geological information is needed here; and landed proprietors, who think it less troublesome to employ an agent than to direct such a simple operation, may at least profit by this hint, and choose an agent who knows something of the rocks he is to drain.
The same knowledge which guides to a right general method of draining, conducts to a clear and almost certain method of finding water by wells, and enables an engineer to predict with much probability, whether, at what depth, in what quantity, and even of what quality, water will be found. Why is water so generally found by deep wells at London and Paris? Why is it often so abundant in these wells? Why is it often of pure quality, though in the descent small quantities of impure water are frequently penetrated? Because under both these capitals, the open, jointed, purely calcareous chalk strata, in great thickness, converge with opposite dips, and collect the water, which, upon the perforation of the superincumbent masses of clay, &c., rises with much force, and continues to flow, unless drained by other of these "Artesian" wells. This method of obtaining water is now commonly known, but deserves to be far more extensively practised in agricultural districts, where natural springs of pure water are rare blessings.
Another thing, probably of importance to agriculturists, is the discovery of substances at small depths which, if brought to the surface, would enrich, by a suitable mixture, the soil of their fields. This is very strongly insisted on by sir H. Davy in his Essays, and considering how easy a thing it is for a landowner to ascertain positively the series of strata in his estate, it is somewhat marvellous that so few cases can be quoted, except that of sir John Johnstone, bart. of Hackness, near Scarborough, in which this easy work has been performed.
Finally, in experiments for the introduction of new systems and modes of management, with respect to cattle and crops, it will be of great consequence to take notice of the qualities of the soil, substrata and water, for these undoubtedly exercise a real and perhaps decisive influence over the result.
Construction of Roads, Railways, Canals, &c.
In planning and executing public works, such as canals, railroads, and common roads, a knowledge of the rocky structure of a country ought to be considered indispensable, and the boring rod is in continual requisition. But the engineer, who is also a geologist, will find it a surer method of research, to trace the systems of strata across miles of country, than to merely feel by the chisel at so many points of a line. To fix the line of a road is the problem, and a knowledge of the geological structure of the country on a large scale is one of the grand data for a true solution of it. When the line is fixed, the practical man will need minuter information than geology can give, but there will be many occasions for the exercise of this science where tunnels, and deep cuttings often show loose sands and other formidable things unexplored by the boring-rod, though not beyond the expectation of a geologist.
The choice of a line of country for canals may often be rightly governed, by attending to the series of strata, and the dislocations to which they are subjected. For thus the summit levels may often be conducted in argillaceous tracts, or in synclinal hollows, where not only no waste of water need be dreaded, but by suitable trials fresh supplies may be had at moderate depths from the surface.
Building Materials.
The assistance which Geology can render to the architect in the choice of building materials is considerable, but not easily defined. Indeed, it is rather because a geologist of experience has necessarily directed his attention to the various degrees of resistance to decay, which rocks of different kinds present, than by any deductions from pure geology, that he can materially aid researches in this respect. There is no doubt that very great benefit would result to the building art, if the whole kingdom were surveyed by geologists and architects, for the purpose of determining generally the occurrence and qualities of stone suited for great and costly edifices. In such a survey it would be proper to inquire how far the indications of durability presented in natural sections were corroborated by the evidence of ancient buildings; and a complete investigation would require further the examination of the chemical quality, mechanical strength, thickness, and other circumstances of the several beds of a rock.
The importance of this caution will be evident when we state that Roman sculptures remain at Bath and York, executed in oolite, magnesian limestone, and millstone grit, which yet retain all their characteristic perfection, while other Bath oolite, magnesian limestone, and gritstone have perished in churches and houses in less than 100 years. The reason is, that the different beds of a rock are of very unequal value, and here the geologist or scientific mason will have their claim to attention.
As certain trees will bear the ocean air even in our unfavourable climate and others not, so with stone; it is not equally durable in all situations, but yields variously and unequally to carbonic acid, smoke, dampness, and salt vapours. Most wisely, therefore, has a commission been issued to determine, in the case of the new houses of parliament, the best material for this national work, and we trust that this symptom of reviving attention to the importance of scientific advice in guiding the skill of our workmen, may be the harbinger of a more frequent reference of questions unsuited for the decision of statesmen, to those persons who have, by a life of study, qualified themselves to give opinions useful to their country.
Coal and other Mineral Products.
Two things have been established by geological research in opposition to the contracted "experience" of colliers, and it is difficult to say which is most important. First, it is perfectly ascertained that coal is limited in Europe and America, almost absolutely, to one portion of the series of strata. Secondly, it is demonstrated, that coal occurs in abundance and of excellent quality beneath large tracts of country where few or no indications of its existence appear at the surface. In the practical working of coal which has been discovered, geological principles may often be useful in determining its probable extent, but their main value is in the discovery of coal in new situations, and the arresting of costly and fruitless trials for coal, where it cannot be found.
In both of these points of view, geology appears in
that favourable light when, compared with mere " practical knowledge," that science always occupies when compared
to those branches of experience which it includes.
A landowner in one of the midland counties, as Northamptonshire
or Oxfordshire, where fuel is dear, is naturally
anxious to "discover" coal, and being completely
ignorant of geology, or blindly credulous in what is
called "practical" knowledge, sends for a workman, or
"borer," from some coal district, to "find" the coal.
A workman from some distant establishment is often
preferred, and great alarm is felt lest the opinion of
this oracle should be unfairly biassed by the influence
of the nearest coal proprietors. Such a workman might
be able to give in his own country a right opinion as to
the cheapest mode of working a bed of coal, the best
mode of walling a pit, and, perhaps, even the proper
position for a bore-hole. But when he is carried to the
oolites and lias of Northamptonshire and Oxfordshire, he
is expected to decide on a question of even national importance,
and to influence a landowner, perhaps already
impoverished, in the desperate venture of searching for
coal at the cost of many thousand pounds, merely because
the ditches yield blue clay (which the collier calls "metal")
or a bit of jet! At the same time the youth of
Oxford and Cambridge receive accurate and admirable
instructions from the lips of gifted men; lectures are
given in every philosophical institution; geological maps
and books are offered in every window; and all these
various modes of scientific caution are urged in vain: the
pit is sunk, and the landowner is ruined, merely by the
honest error of a workman set to a task beyond his experience.
Is this a harsh picture? Let the recollection of
old trials at Bruton in Somerset, and Bagley Wood near
Oxford, the more recent folly at Northampton, and the
failures of Kirkham and many other localities in the
north of England, serve as a warning to inconsiderate
persons in other districts. There may not always be
found a geologist, willing to turn away from his
delightful studies, to avert the ruin which can only fall
on those who disregard the plainest truths of geology.
In countries where coal has long been worked, almost every district is explored at least nearly to its boundaries. This is at present the case in England—indeed, generally in Europe; and, consequently, it may be thought that the time has gone by for the geologist to be of service, and the future is to be in trusted to coal viewers and workmen. When coal viewers become geologists, (and this is now very generally the case with men of eminence in that profession), the question of the future extension of our coalfields will be in safe hands; but in all cases, and at all times, this is a geological question. Only sixteen years ago, (it is in our own memory,) a valuable estate in Durham was pronounced to be devoid of coal, "because it was situated on the magnesian limestone," and might have been sold under this opinion, but that a geologist of celebrity, Dr. William Smith, showed the falsity of the reasoning, reported favourably of the probability of finding good coal in abundance beneath the property, and advised the proprietor to work it. That estate is now the centre of a rich and well explored mining tract, all situated beneath the magnesian limestone, and this result was the fruit of scientific geology, not "practical" coal-viewing, though the professional mine-agents of the North of England are DOW employed in extending its benefits.
This fact is one of a large class; and it more particularly deserves attention, because the magnesian limestone overlying the coal of Durham is united in one system of rocks with the red sandstones of Cheshire and Staffordshire, beneath which, as beneath the magnesian limestone of Durham, the coal appears to dip, and the red marls of Somersetshire, under which it is largely worked. Is there a coalfield below the great Cheshire plain?
If this question is to be answered without the boring rod, none but geologists can venture to speak; nor of these, any but those who have studied the peculiar character and relations of the coalfields which border the red sandstone plain in Lancashire, Shropshire, Staffordshire, and Flintshire; or have ascertained the truth in analogous situations, such as the district bordering the coalfields of Leicestershire and Warwickshire.
Perhaps there is a coalfield beneath parts of the Cheshire plain. This may be plausibly argued, from the fact that all the bordering coalfields dip beneath that plain; and the probability of the inference is greatly strengthened by the circumstance (first ascertained by the author of this volume) that the limestone beds which lie in the upper part of the Lancashire coal tract are identical with those previously described by Mr. Murchison from the coalfield of Lebotwood, near Shrewsbury. This limestone is of a peculiar quality, yields peculiar fossils, and lies in connection with coal-beds yielding peculiar plants, at both these distant points; circumstances which go far to prove, not perhaps the entire contiguity of the rock from point to point, but its contemporaneous deposition in one and the same coal basin. It is, therefore, probable that that coal basin is really continuous under parts of the Cheshire plain of red sandstone. Whether it will be worth while to sink for this coal is not a question for geology to answer; but if the attempt is to be made, geological investigation alone can indicate the proper situation for the trial.
Geologists must not be deterred, by the neglect which too frequently has attended their recommendations, from calling on "practical men" to consider and make profitable use of their discoveries and reasonings. Few of their important announcements have really been unproductive; the seed which they have sown, though favoured with little cultivation, has, in the end, grown up to be fruitful of good.
If any one should say geology makes no such prophetic announcements our collieries are extended without the aid of science, our iron works are supplied with the raw material by the experience of the workmen, and our gold comes by accidental discovery let him be reminded of the well-known fact that, had geology been believed, the date of the opening of our greatest northern collieries would have been earlier by several years; let him be assured, that had practical application kept equal pace with geological theory, we should not have been startled, in 1851, by the discovery of immense bands of ironstone which were measured and described more than twenty years before; and let it be added, that because geology has of late years made itself heard, even from a distance, and because the principles of this science have been kept in view in the field, gold will in future be looked for in the places where it is likely to be found. A few words respecting the ironstone and the gold.
The lias shales of the Yorkshire coast are of a greater
thickness, and contain a greater variety of valuable
substances, than those of the south of England. Besides
the jet, cement stone, and alum shale, there are
bands of ironstone, sometimes amounting to sixteen feet
in thickness, of quality equal to the average of the carbonates
of a coal district. They lie toward the upper
part of the lias deposits, above a certain series of sandy
beds with peculiar and characteristic fossils, and below
certain other beds extensively worked for alum. The
stone can be obtained at so small a cost, that about
2s. 6d. a ton is a remunerating price to the adventurer.
It is in such, immense quantity that an acre will yield
from 20,000 to 50,000 tons, and it may be opened in a
line of coast and a line of inland cliffs, at many points,
and for very many miles of outcrop. Railways are
now laid to it, furnaces are built near it, and hundreds
of thousands of tons of it are set in motion annually
from the hills of Cleveland. This great activity is of
sudden growth, one of the wonders of 1851. It was
said, what was geology doing, that this vast treasure of
iron has been left for the practical man to discover?
We reply, this ironstone was measured, its exact geological
place marked, and its prominent localities designated,
in printed type and coloured sections, more
than twenty years previously![5]
And, in regard to gold, the case is stronger. Constantly brilliant in its natural aspect, occurring in many river beds, easily fusible, remarkably ductile, and exempt from rust, it was known and valued from the earliest ages, and was probably the very first of all metals tried in the fire and moulded by the hammer. Gold has been gathered in every quarter of the globe, in every age known to history and tradition. Scythia and India—the Tagus and the Po—the Hebrus, the Pactolus, and the Ganges—gave their gold to Rome, as they had given to earlier masters. Yet not all this immense experience, sharpened by the "auri sacra fames," produced philosophical views of those co-ordinate phenomena by which the presence of gold could be predicated in new situations. It was simply a matter of trial and error. At last it came under the domain of geology, and was treated as a geological problem. The usual consequence followed—experience became science, and further discoveries were anticipated by theory.
For not only were observations having the character of scientific generalization published many years before the late discoveries, but public attention was distinctly called to their practical application, and a certain country was definitely indicated as likely to be highly productive of gold, and worthy to be explored for that metal. This was done by Sir Roderick Murchison—one who might well be excused, by the variety and importance of his explorations, if he had left wholly to others the care of pointing out the economical application of them.
But, after surveying the Ural, and publishing, in 1844, his critical observations on the old mines of that "hyperborean" district, he took several occasions publicly to declare the general views to which they had conducted him; made a special comparison of the Ural with the eastern chain of Australia (1844); invited the Cornish miners to emigrate to New South Wales and dig for gold on the flanks of the "Australian Cordillera," where gold had been found in small quantity, and in which, from its similarity to the Ural, he anticipated that it would certainly be found in abundance (1846); and presented a note on the subject to the British Colonial Minister (1848).[6]
Facts like these are unanswerable; but do they not teach us that it is of the utmost importance to connect more closely the theory and the practice, the intellect and the hand; to place the treasures of science within the grasp of experience; to bring together the Murchisons and the Hargraves, the men of thought and the men of action, so that right ideas may become fruitful deeds, and patient labour be encouraged to undertake enterprises which science shows to be of good omen. The lectures which are now in course of delivery on Australian gold at the Museum of Practical Geology, are a step in this direction. A Mining School is established there. If it produce the fruits which are expected from such an institution, many benefits will accrue to humanity; knowledge will be diffused among classes who know how to value it; industry will be better guided and better rewarded; our miners will not breathe the slow poison of mephitic air, nor perish by hundreds through the explosion of inflammable gas.
It appears unnecessary to extend these proofs of the value of geological principles to the agricultural and mercantile interests of a nation. One of the most obviously useful applications of science is in the colonies sent forth by a commercial people; and perhaps no more important service could be rendered to Australia or Canada, than by accurate geological surveys, such as are now proceeding steadily in several of the United States of America.[7]
This is, however, not the place to advocate plans of this nature; nor can it be expected that recommendations for colonial advantage will be much regarded in times when even the laborious surveys of the geology of England have been, till lately, left entirely to the generous self-devotion of individuals. It cannot be expected that costly works, like that on the "Silurian System" and some others we could name, produced at private expense, should be numerous; yet, except on the scale of illustration adopted in these volumes, they are inadequate for their object, and unsatisfactory even to their authors. One step has, however, at length been taken: the Ordnance Survey has been rendered in some degree serviceable to geology, both in England and Ireland; and the officers who conduct this noble work are both able and desirous to make it a geological as well as geographical monument.
Let this truly national labour be completed; let the Mining Districts be illustrated by maps on a larger scale; let a system be introduced by which invaluable mining records, now perishing in the unsafe custody of individuals, shall be preserved for the benefit of this and future times: the public will reap incalculable advantage, and geologists will advance nearer to completeness the bases of their speculations. This is all, or nearly all, the encouragement which Geology needs from a government; or rather, these are the most obvious modes of giving to the community a foretaste of the benefits which this science is destined to bestow. Strong in its fundamental facts, corroborated in its inferences by the progress of all collateral branches of the study of Creation, linked in union with the highest forms of scientific truth, and grasping at objects full of the noblest interest for man, and the most reverential thoughts toward the Maker and Preserver of the Universe, nothing but the general decay of the human intellect will permit Geology to languish, till the Natural History of the ancient earth be known to its modern occupier Man.
- ↑ The Silurian System, in two volumes 4to.
- ↑ One recently published by the author of this volume, at a moderate price, may be used for this and other purposes of reference.
- ↑ See on this subject the remarks which accompany each system of strata in Vol. I.
- ↑ See Vol. I. p. 62.
- ↑ Illustrations of the Geology of the Yorkshire Coast (1829.). See also an earlier description of these iron stones in Young and Bird's Survey (1822).
- ↑ See Trans. Roy. Geog. Soc., xiv. p. xcix. Trans. Roy. Geol. Soc. of Cornwall (1846.), p. 324., and Rep. of Brit. Assoc. 1849.
- ↑ This passage is left as it was written some years ago, for the purpose of remarking that the appointments which it suggested are now made—Mr. Logan is surveying Canada, and Mr. Stutchbury is engaged in Australia.