THE ANCIENT EPOCH.
“Where wast thou when I laid the foundations of the earth?”—_Job_
xxxviii. 4.
And now in right earnest let us begin our examination of the earth’s
crust. Some of the terms we may use will, perhaps, at first sight appear
repulsive from their novelty and difficulty; such words we will explain
as we proceed, and will only stay the student’s course to remark, that
there is a necessity for the use of the dead languages in the formation
of compound terms that are to become descriptive names, and in their
application to newly discovered objects. This necessity arises from the
fact that it is only in this way that scientific men of different
nations can understand the character of each other’s researches, and
compare notes with one another. A fossil is found, let us suppose, in
the lias formation; it proves to be the organic remains of some very
strange and anomalous creature. People go down to Lyme Regis to examine
it, and, in doing so, discover others. Comparative anatomists arrange
the dislocated parts and give them a name; this must be intelligible to
geologists on the Continent as well as in England; and therefore some
term descriptive of the animal, once the living possessor of these “dry
bones,” must be given, and finally it is called _ichthyosaurus_. Any one
in Russia, or Austria, or Italy, who happened to be acquainted with the
rudiments of Greek, would know at once the kind of animal referred to by
its very name, derived from _ichthus_, a fish, and _sauros_, a lizard.
This would indicate to all scientific men the nature of this remarkable
animal, of which we shall have to tell some stories by and by as full of
wonder as any modern or ancient book of marvels; while, if we had called
it _fish-lizard_, only those who understood English would know what we
meant. Our object is to simplify as much as possible every difficult
term that may be used; but while we solicit our readers to master each
difficulty as it rises, we hope they will not think that, when they have
read this little book, they are masters of Geology, our highest ambition
being only to impart a _taste_ for the science.
To return: our examination commences with the Plutonic rocks, so called
in memory of the well-known mythological god of the fiery or infernal
regions; and we take _granite_[14] as a type of these rocks, because it
is so familiar to all our readers. There are besides granite,
syenite,[15] greenstone, porphyry, basalt, and others, to dilate upon
which would defeat our purpose. Our object is to lay but a little at a
time upon the memory, and to let that little be well digested before we
pass from the thoroughly known to the unknown. Nothing but actual
examination can make the student familiar with the varieties of the
rocks of this very ancient epoch in the world’s history. Well, everybody
knows what granite is; they see it on the kerb-stones of the wayside, in
the hard paving of the London streets, in the massive slabs of London
and Waterloo Bridges, and elsewhere. “Granite!” exclaims the reader,
“everybody knows what granite is, and there is an end of it; you make as
much fuss about granite as Wordsworth did about his well-known primrose,
and the man who could see nothing but a primrose in a primrose.”
But there is a poetry and a history about granite upon which we are
going to dwell. This piece of granite which I hold in my hand is
composed of quartz, mica, and feldspar.[16] The quartz is white and
hard—I can’t scratch it with my knife; the mica is in glistening plates
or scales; and the feldspar is soft and greyish, and can easily be
scratched. Oh, if this granite could speak, what a story could it tell!
“To give it, then, a tongue were wise in man.” Let us try. “Once upon a
time, long, long ages ago, incalculable periods before Adam was placed
in possession of Eden, I, the granite, and my contemporaries, came into
being. Before us, this planet ‘was without form and void.’ A dark
chaotic period, of which I know nothing, preceded me. When I first
emerged into being, at the command of Him who laid the foundations of
the earth, this world was a barren, lifeless, uncultivated, uninhabited,
untrodden, seasonless waste. Here and there were undulations of land and
water, but all was bare, desolate, and silent: not a moss nor a lichen
covered the ancient skeleton of the globe; not a sea-weed floated in the
broad ocean; not a trace existed even of the least highly organized
animal or vegetable; everything was still, and with the stillness of
universal death. The earth was prepared, and the fiat of creation had
gone forth; but there was no inhabitant, and no beings endowed with life
had been introduced to perform their part in the great mystery of
creation.”[17] And the granite might go on to say—“Man! of three-score
years and ten, where wast _thou_ when He, my Maker and yours, laid the
foundations of the earth? Let me tell you what an important part I have
played in the history of your world’s formation. I rise to the highest
elevations, and form the sublimest pinnacles on the surface of the
globe, and without me your scenery would lose its grandeur and its
glory. But for me Albert Smith had never climbed Mont Blanc, nor
Humboldt Cotopaxi and Chimborazo; nor would the head of the famed
Egyptian Memnon[18] have been sculptured. You may see me giving to
Cornwall, Wales, and Scotland their most valuable minerals and metals.
In Europe
‘I am monarch of all I survey,
My right there is none to dispute.’
The Scandinavians, the Hartz mountains, the Alps, and the Pyrenees are
mine; nor is my territory less in Asia, Africa, the great Americas, and
in the becoming great Australia; and thus, by my deeply rooted
foundations and my vast extension, I constitute the framework, solid and
immoveable, of this ‘great globe and all that it inherits.’”
Thus, at any rate, the granite might speak, nor would there be one word
of vain boasting in it. Having beard it, or fancied we heard it, which
amounts to the same thing, let us soberize ourselves, and put granite
into the third person. There are no fossils in granite and the other
Plutonic and volcanic rocks; even supposing any forms of life to have
been in existence at the period to which we are referring, the action of
fire has annihilated all their remains. We should not therefore expect
in Cumberland and Cornwall, nor in those parts of Devonshire where
granite prevails, to find the fossils peculiar to other formations with
which in time we hope to make familiar acquaintance. But though
destitute of interest in this respect, how great is its importance and
interest in those economic uses which have the geologist for their
guide, and the whole family of man for their beneficent operations!
“Many varieties of granite are excellent as building stones, though
expensive in working to definite forms. Some of the most important
public works of Great Britain and Ireland, France and Russia, are of
this material. In selecting granite, those varieties in which the
constituent minerals and the scales of mica are superabundant, should be
avoided; and, as a practical test, it is wise to notice the country
immediately around the quarry, as the sandy varieties rapidly
disintegrate,[19] and form accumulations of micaceous sand. The Hayter
or Dartmoor granite, the Aberdeen granite, the Kingstown (Dublin)
granite, some beds of the Mourne or county of Down granite, and the
Guernsey or Channel Island granite, are well known for their excellence.
In some of the quarries the bedding of the granite is more defined than
in others; and wherever this is the case, or where marked cleavages or
joints prevail, the work is much facilitated. Many old Egyptian works
and statues were formed of granite, and it is still used for colossal
works, as it takes a fine polish. For example, the great fountain shell,
or vase, before the Museum at Berlin, and the pedestal of Peter the
Great at St. Petersburg, are of the northern granite, being sculptured
from erratic blocks. The splendid Scotch granite columns, in the
vestibule of the Fitzwilliam Museum at Cambridge, are beautiful examples
of a modern application of this rock to the arts.”[20]
It is also in the Plutonic or igneous rocks that almost all the metals
are found; and here we have our first illustration of that order to
which we shall frequently call attention; an order as exquisite as can
be found in the drawers of a lady’s cabinet, forbidding the thought that
anything observable at the present time, in the bowels or on the surface
of the crust of the earth, can be attributed to the violent diluvial
action of the Noachian deluge. The diagram below represents an ideal
section of a mining district.
[Illustration:
SECTION OF A MINING DISTRICT.
]
Here the metalliferous vein, we may suppose, has cropped out on the
surface of the ground, or, as the miners say, has “come above grass.”
Let us now suppose that the position of this vein of ore, copper, lead,
or tin, has been ascertained—that is, how it runs, whether from north to
south, or from east to west—and also that the “captains” of the mining
district around have given their opinion as to the extent and thickness
of this underground vein. The next thing is to obtain this mineral
wealth. For this purpose shafts (_a a a a_) must be sunk, which must
reach the vein at a certain depth; then will probably follow cross-cuts
(_c c c_), called adit levels (technically an “additt”), driven, as may
be seen, at the lowest convenient point above the level of the highest
water of the valley; and these, in connexion with the shaft, will serve
the purpose of draining the mine and carrying the ore above ground. It
will also be seen, by reference to the diagram, that the shafts of a
mine do not always correspond; sometimes they are sunk vertically to
meet the vein, sometimes they are commenced in the very outcrop itself.
On this matter the best geological lesson is a visit to Cornwall, where
the student will see that everything depends on the locality of a mine,
the nature of the slope of the hill, or the character of the rock in
which the vein appears, and so on. “The act of sinking a perpendicular
shaft downwards to a depth where it is calculated the lode should be
cut, may seem to require little further skill than is necessary to
determine correctly the spot on the surface where the work is to
commence. But the process in this way is exceedingly tedious; and in a
mine at work, where many galleries already existing are to be traversed,
much greater rapidity is desirable. In such a case the shaft is sunk in
several _pieces_ (see diagram below), or, in other words, the sinking is
commenced at the same time in different levels; and no small skill is
required to lay out the work, so that the different portions of the
shaft thus formed may exactly fit when they are joined together. An
exceedingly small error of measurement, in any one of these various and
dark subterranean passages, would, in fact, be sufficient to throw the
whole into confusion; but such an accident rarely happens, although
works of the kind are common in the Cornish mines.”[21] As an
illustration of the immense quantity of water in the mines, we may
add—and this is almost as startling as any romantic fiction—that the
various branches of the principal level in Cornwall, called “the Great
Adit, which receives the waters of the numerous mines in Gwennap, and
near Redruth, measure on the whole about 26,000 fathoms, or nearly
thirty miles in length; one branch only, at Cardrew mine, extends for
nearly five miles and a half, and penetrates ground seventy fathoms
beneath the surface. The water flows into a valley communicating with a
small inlet of the sea, and is discharged about forty feet above
high-water mark.”[22] In this method about forty millions of tons of
water are raised by steam-power out of the mines in Cornwall.
[Illustration:
EAST WHEAL CROFLY COPPER MINE, CORNWALL.
]
Here, then, we have seen two of the economic uses of geology in
connexion with _granite_ alone; and as we think of these mineral
treasures, requiring only the labour and skill of man to bring them out
for his service and for the civilization of the world, our boast is in
our native land, which, though insular and small, combines within itself
everything needful to develop its three sources of national
wealth—mining, manufactures, and agriculture—to their highest point. Our
boast is not the warrior’s boast, which Shakspeare puts into the mouth
of one of his heroes—that this our isle is
“That pale, that white-faced shore,
Whose foot spurns back the ocean’s roaring tides,
And coops from other lands her islanders”—
but rather that, without impropriety or irreverence, the words of Holy
Writ may as legitimately be applied to Great Britain as to Palestine. It
is a land wherein “thou shalt eat bread without scarceness, thou shalt
not lack anything in it; a land whose stones are iron, and out of whose
hills thou mayest dig brass.[23] When thou hast eaten and art full, then
thou shalt bless the Lord thy God for the good land which He hath given
thee.” (Deut. viii. 9, 10.)
But before we bring this chapter on granite and its kindred rocks to a
close, we must glance at one more purpose served by this Plutonic rock.
Here is a teacup, and here is a piece of granite: the one comes from
Cornwall, the other is made in Staffordshire or Worcestershire. What
relation have they to each other? If it were not thought _infra dig._,
we should say the granite is the parent of the teacup. In Cornwall,
especially in the neighbourhood of St. Austel, the writer has lately
visited what are called the China clay works. “The granite is here in a
state of partial decomposition. In some localities, this _growan_”
(Cornish for disintegrated granite) “is tolerably firm, when it
resembles the Chinese _Kaolin_, and, quarried under the name of China
stone, is extensively employed in the potteries. This is ready for the
market when cut into blocks of a size convenient for transport; but the
softer material, which is dug out of pits, and called _China clay_, or
_porcelain earth_, requires a more elaborate preparation for the purpose
of separating the quartz, schorl, or mica from the finer particles of
the decomposed feldspar. This clay is dug up in _stopes_ or layers,
which resemble a flight of irregular stairs. A heap of it is then placed
upon an inclined platform, under a small fall of water, and repeatedly
stirred with a _piggle_ and shovel, by which means the whole is
gradually carried down by the water in a state of suspension. The heavy
and useless parts collect in a trench below the platform; while the
China clay, carried forward through a series of _catch-pits_ or tanks,
in which the grosser particles are deposited, is ultimately accumulated
in larger pits, called _ponds_, from which the clear supernatant water
is from time to time withdrawn. As soon as these ponds are filled with
clay, they are drained, and the porcelain earth is removed to _pans_, in
which it remains undisturbed until sufficiently consolidated to be cut
into oblong masses. These are carried to a roofed building, through
which the air can freely pass, and dried completely for the market. When
dry they are scraped perfectly clean, packed in casks, and carried to
one of the adjacent ports, to be shipped for the potteries.”[24] As
furnishing some idea of the extent to which this business is carried on,
it may be added that 37,000 tons of this China clay are annually shipped
from the south-west of England to the potteries, the value of which is
upwards of £50,000, while the number of working men and women thus
employed is beyond calculation. This is one of the practical results of
geology. This is one of the things which geology, once a neglected and
unpopular science, has done for our comfort and welfare. “A hundred
years ago, it does not seem that any part of this China clay was made
use of, or that this important produce was then of any value
whatever.”[25]
We bring this chapter to a close. Granite and its kindred rocks should
stand associated with an actual history and poetry, not inferior to the
history and poetry of man’s own handiwork; and we believe geology, so
often regarded with dread by the uninitiated, will soon be considered
worthy a patient and painstaking investigation. Remembering that geology
is still an incomplete science, and that we have much yet to learn
concerning the laws of organic and inorganic matter, we should be modest
in the maintenance of any theory, while thankful for the acquisition of
any fact. “We have yet to learn whether man’s past duration upon the
earth—whether even that which is still destined to him—is such, as to
allow him to philosophise with success on such matters; whether man,
placed for a few centuries on the earth as in a schoolroom, has time to
strip the wall of its coating and count its stones, before his PARENT
removes him to some other destination.”[26]