is pretty well proved; for many pieces of coal, if ground thin and
subjected to the microscope, present a texture exactly such as can be
seen in wood of the present date, and not only the ordinary structure,
but in very many cases certain "dotted fibres," indicating that the
wood belonged to the order of cone-bearing trees (_Coniferæ_), and
there is but little doubt that the constant deposit of such wood and
its slow and gradual decay was the real source of all our coal. How
wonderful, and how good, is the foreknowledge of God! Just at a time
when the great forests of the earth are fast disappearing, and with
them the only other source of fuel for fires, this reserve of the
old forests, which was then useless, serves man as a most excellent
friend--more useful than gold or silver, more precious than diamonds
or rubies! But this world is one of perpetual change, and the coal
thus brought forth from the depths of the earth, is by man being
rapidly restored to the air from whence--thousands of years ago--it was
derived; and it is not coal alone which is thus being restored, but
every organic being in the whole creation, for at their decay they all
enter this vast mausoleum of the dead!
[Illustration]
THE EARTH.
[Illustration]
The Earth, considered as one of those spheres which circulate round
the sun amidst the wide expanse of the firmanent, holds but an
insignificant position among them, especially when compared with those
great and magnificent orbs, Jupiter and Saturn; but, in another point
of view, as the dwelling-place of all the animated beings, vegetables,
and minerals, with which we have any practical knowledge, it holds to
us a position in creation far above all the others.
It is upon the surface of this our earth that we behold in detail
those wonders of the Great Creator's hands, which must fill all
who contemplate and study them with enlarged ideas of His wisdom,
goodness, and power. We see the millions of stars sparkling in the
abyss of space, and our minds are so formed that we can measure and
gauge their distances and rates of travelling, their orbits and their
sizes, their weights, and the powers with which they attract and
influence each other; but we only contemplate a star as one bright and
beautiful object worthy to be one of the gems which the Almighty has
set in His crown of glory, or a lamp to light the halls of His infinite
habitation, but we still contemplate it as a single object; while on
the surface of the earth our Maker has permitted us to roam and search
out by what benevolent contrivances He has suited all things to the
comfort and welfare of His creatures. How His mercy and goodness are
extended amply to the most minute animalcule as well as to man, and how
His powers of construction are to be found in the most minute objects
which the microscope can display, as perfect as in the largest creature
we behold. It is here upon our earth that we perceive how the structure
and functions of all creatures are regulated and controlled by the
unerring laws which He has created, over which laws the creatures
have no control, and which if duly regarded and used according to the
faculties each has been gifted with, will return the greatest joy and
happiness their several natures are capable of, and secure all that
perfection of operation which their mechanical frames are suited to
perform; but before any description of the organised beings which
dwell on the earth can be given, it will be proper to enter into a
description of the earth itself, to see what sort of place God has
provided for them, and how through succeeding cycles of time He has
gradually perfected and prepared it for the reception of His last great
work, Man.
It is only a few miles below the surface of the earth that man has been
able to penetrate and examine, but reason comes to assist him where
examination fails, and it would have been but a few hundred yards only
that his labours could have extended had it not been that parts, which
are generally situated miles below the surface, are occasionally found
at or even raised above it, by some disturbing cause which operated in
times far back; so that man is able to examine on the surface parts
which he could scarcely dig down to.
The whole of the earth, its inhabitants, the air which surrounds it,
the waters upon its surface, and its vegetable products, are composed
of certain substances called elements, combined and united in certain
numbers and proportions. The following is a list of all known:--
METALLIC ELEMENTS.
Aluminium 13.7
Antimony 12.9
Arsenic 75
Barium 68.5
Bismuth 21.3
Cadmium 56
Calcium 20
Cerium 47
Chromium 26.7
Cobalt 29.5
Copper 31.7
Didymium *
Donarium *
Erbium *
Glucinium *
Gold 197
Ilmenium *
Iridium 99
Iron 28
Lanthanium *
Lead 103.7
Lithium 6.5
Magnesium 12.2
Manganese 27.6
Mercury 100
Molybdenum 46
Nickel 29.6
Niobium *
Norium *
Osmium 99.6
Palladium 53.3
Pelopium *
Platinum 98.7
Potassium 39.2
Rhodium 52.2
Ruthenium 52.2
Silicon 21.3
Silver 108.1
Sodium 23
Strontium 43.8
Tantalium 184
Tellurium 64.2
Terbinum *
Thorium 59.6
Tin 59
Titanium 25
Tungsten 95
Uranium 60
Vanadium 68.6
Yttrium 32.2
Zinc 32.6
Zirconium 22.4
NON-METALLIC ELEMENTS.
Boron 10.9
Bromine 80
Carbon 6
Chlorine 35
Fluorine 18.9
Hydrogen 1
Iodine 127.1
Nitrogen 14
Oxygen 8
Phosphorus 32
Sulphur 16
Selenium 39.5
By this list it will be perceived that the greatest number of the
elements are metals, but most of these are very rare and met with but
in certain localities, making up but a very insignificant part of the
earth's surface, while others (never found in nature, as metals) in
combination with oxygen forming "earths" compose the greater part of
its bulk. But of all the elements, oxygen (a gas) is the most widely
diffused, and constitutes rather more than one half of the whole earth,
thus it forms 1/5th of the air, 9/10ths of the water, of the various
earths and rocks about 1/2, and in all organised beings about 3/4.
Of the metallic elements, those which form the greater bulk of the
earth are--
Silicon.
Aluminium.
Calcium.
Magnesium.
Potassium.
Sodium.
These never exist in nature as metals, but combined with oxygen forming
the following earths and alkalies:--
Silica }
Alumina } EARTHS.
Lime }
Magnesia }
Potassa } ALKALIES.
Soda }
These four "earths" form about eighty-five per cent. of the whole
bulk of this globe, the remainder being made up of water (composed of
eight parts oxygen and one part hydrogen), of "salt," both as rock or
crystal-salt, and dissolved in the water of the sea, of the ores of
different metals (metals in union with oxygen, sulphur, &c.), and of
the remains of former vegetation, existing as coal.
Silica is composed of 21.3 parts of silicon with 24 of oxygen, it is
that earth which constitutes a great part of almost every soil, and
forms sand, sandstone, and flint, it enters largely also into the
formation of granite and the other primitive rocks; when pure it is
called "quartz" or "rock-crystal" and is often found in large and
beautiful masses. Silica, in different forms, contaminated and coloured
by different metallic oxides, &c., forms that class of stones known as
"agate," "Scotch pebble," "carnelian," &c., and in the form of flint is
found nearly pure, forming "nodules" or rounded masses lying in layers
in the chalk cliffs on our coasts, the origin of these nodules of flint
is very obscure, but they are by many attributed to the petrifaction of
sponges, &c., the general form of which they often retain as well as
their internal structure, which may be seen when viewed in thin slices
by means of the microscope. Pure silica is a white insoluble powder,
and is much used by the makers of porcelain to mix with their other
ingredients.
Alumina consists of 41.1 parts of aluminium in combination with 24
parts of oxygen, it is the earth which forms the basis of all clays,
loams, and slates, it is in its pure state perfectly white but in most
clays is coloured brown or blueish by oxide of iron, many of our most
beautiful gems, as the ruby, sapphire, and emerald, consist chiefly of
crystallised alumina coloured by oxide of iron, chromium, &c., this
earth like silica enters largely into the composition of the primitive
rocks.
Lime is another of the earths which form a great part of all soils;
it consists of 20 parts calcium with 8 of oxygen. Unlike the two
preceding earths, it exists only in union with some acid. When united
to carbonic acid it forms limestone, chalk, marble, &c., and when in
a crystallised state "Iceland spar." The various kinds of limestone
are largely used as building-stones, and any of them when burnt yields
lime or "quick-lime" as it is generally called, which is capable of
uniting with a certain portion of water, giving out a considerable
amount of heat during the combination. Lime is often found in union
with sulphuric acid, forming gypsum or Plaster of Paris, in combination
with phosphoric acid it forms the basis or earthy part of the bones of
animals, and is found in some of the tissues of plants.
Potassa consists of 39.2 parts potassium in union with 8 oxygen, it
constitutes about 12 per cent. of the granites and basalts (primitive
rocks) in union with silica and alumina, it is also found in the fluids
of many vegetables in union with carbonic, oxalic, and other acids.
Soda consists of twenty-three parts sodium with eight oxygen, it
however does not exist in this form in nature, but in union with
chlorine instead of oxygen, constituting chloride of sodium or common
salt, this substance forms strata of considerable extent in some
localities and being soluble has no doubt been washed out by the rains
from many other places and has thus communicated saltness to the waters
of the ocean. The other metallic elements exist chiefly in those forms
of earth called "ores" being metals in union with oxygen, sulphur, &c.,
or are found in the metallic state, as gold, platinum, &c., it is from
these ores that most of our useful metals are procured by the process
called smelting, as in the case of iron, copper, lead, tin, &c. All
the substances known result from the combinations of the elements, but
these elements do not chemically combine in all proportions, but in
certain definite quantities only; these quantities or proportions are
signified by the numbers attached to each element in the list given,[1]
and the union of these substances must be in the proportion of these
numbers (or multiples of them) only, all superfluity of the substances
combined remaining in a state of mere mechanical mixture. For example,
if six parts of carbon (charcoal) made red-hot be plunged into a jar
containing twenty parts of oxygen, it will unite with sixteen parts
only of the oxygen (a multiple of eight), and form twenty-two parts of
carbonic acid, the extra four parts of oxygen still remaining as oxygen
mixed with the carbonic acid; and if into this carbonic acid twenty
parts of lime be put, it will unite with the twenty-two of carbonic
acid, forming forty-two of carbonate of lime, still leaving the four
parts of oxygen untouched. Had forty parts of lime been put into the
mixture, instead of twenty, still only forty-two of carbonate of lime
would have been formed, and the other twenty parts (like the four of
oxygen) being superfluous, would still have remained as lime, mixed
with the carbonate of lime. These combining quantities are called the
"equivalents" of the substances.
[Footnote 1: See the list of the elements at page 45; those
which are distinguished by an asterisk, are elements of which the
"equivalents" are not known.]
Upon examining various portions of the earth's surface, they will be
found to differ in character from each other; in one place perhaps
sandy soil will be found, in another, hard rock, in a third, clay, in
a fourth, chalk, and so on. Now, if this examination were carried no
further, it might well be presumed that each of these kinds of soil
were continued downwards into the earth for an indefinite distance,
but upon digging (as in sinking a shaft or well) it is found that the
stratum of soil upon the surface is soon passed through, that others
in succession present themselves and that this succession of strata
is not a matter of chance, but (with certain restrictions) follows in
invariable order. It is true some strata are occasionally not present,
and that others replace them; but yet (taken altogether) there is the
same order of succession everywhere found. The following diagram (fig.
1) gives the section of these strata from the earth's surface to the
granite which is the lowest of all formations and through which no
one has ever penetrated. The figures give an approximation to their
average thickness in feet. These strata do not all run in a direction
parallel to the surface of the earth, or else it would result that the
surface would everywhere be made up of the highest, but they have been
contorted and heaved up into mounds or depressed; and the granite has
often been pushed upwards, carrying with it all the upper strata to a
certain extent, at last thrusting quite through them all and presenting
itself above the surface, forming in this way the tops of many very
high mountains, Mont Blanc for instance. Such a mountain if cleft from
the summit to the base would present a section similar to that shown
in fig. 2, and thus it occurs (contrary to what would at first thought
be supposed) that the highest ground is generally formed of the lowest
strata, while the valleys are nearly always covered with the latest
formations, which is partly owing to the elevating process before
alluded to, and partly to the winds, rains, &c., tending to carry away
and wash down every kind of soil from the upper ground and deposit it
in the lower.
[Illustration: FIG. 1.--DIAGRAM SHOWING THE POSITIONS AND RELATIVE
THICKNESSES OF THE STRATA.]
[Illustration: _Granite_ FIG. 2.]
[Illustration: FIG. 3.]
[Illustration: FIG. 4.]
[Illustration: FIG. 5.]
Fig. 3 represents strata in a state called by geologists
"conformable," which name is applied when the strata follow their
natural or regular succession, whether this retains its horizontal
position, or, as in fig. 4, assumes a position more or less
vertical, which frequently happens from the subsidence of one
part or the elevation of another; but they are sometimes found in
the state represented in fig. 5, and in which they are said to be
"unconformable." Such strata after having been tilted out of the
horizontal have had other strata deposited upon them, which again
may be more or less contorted from the same causes. The regularity of
strata is often interrupted by what are called "faults" or "dykes,"
which have arisen from some part of the earth sinking down or another
part being raised up, producing a fracture through all the strata and
causing those on either side of this fault or fracture to occupy a
situation not corresponding to those on the opposite, as in fig. 6, but
yet to be found at a higher or lower elevation, and it is nearly always
found that these strata are raised on that side to which the line of
fracture inclines, as in the figure. These faults are often sources of
great annoyance to the miner, who finds a sudden termination to the
seam of coal or ore that he is working. The cracks are generally filled
with some primitive rock, as basalt, rising from beneath while in a
liquid state and filling up the interstices; it will often happen that
the faults thus filled will have veins of the same rock branching out
and not only filling up cracks but forcing its way between the various
strata, thus interposing a stratum of basalt quite out of its proper
position and altering, by the effects of the heat communicated, the
character of the strata in juxtaposition; this is shown in fig. 7.
[Illustration: FIG. 6.]
Upon a close examination of the various strata which form the crust of
the earth, it is found that each has its own peculiar character; some
have resulted from the accumulation of matters deposited at the bottom
of ancient seas, others in the beds of rivers or fresh-water lakes, or
again others (as the coal formation) from the accumulation of vegetable
matters; further, these strata do not only differ in structure and
composition, but also in the remains of animals and plants found in
them; for there is scarcely any kind of soil (above the primary rocks)
in which abundant remains of these have not been found. It will now be
proper to give a description of them in succession, beginning at the
lowest or primary, _granite_.
[Illustration: FIG. 7.]
This appears to be the result of the cooling and crystallisation of
that molten mass which many circumstances (hereafter to be mentioned)
point out as making up the great body of the earth. Granite differs,
in various places, in colour and quality (the varieties are known as
"sienite," "porphyry," "greenstone," &c.), but still retains its own
distinctive characters; it is a hard, crystalline rock, consisting of
"felspar," "mica," and "quartz," in separate crystals, but mechanically
blended; its chemical composition as a whole is silica, alumina,
and potassa, with small quantities of lime and oxide of iron. This
granite is met with everywhere, if the outer crust of the earth be
penetrated to a sufficient depth; it however frequently exists on the
surface, having no strata below it, and in some places overlies other
strata--this, and the fact that cracks and crevices of some of the
lower strata are filled up with granite, which could only have taken
place while it was in a liquid state, as in fig. 8, together with
evidences of the effects of calcination, and other changes producible
only by extreme heat, all around those parts and in the strata
immediately overlaying the granite, point out that it was once in a
state of fusion.
Above the granite formation, in many places, especially in Norway and
Sweden, there is a stratum of rock called _gneiss_, which consists of
the same ingredients as granite in a slightly altered form. Granite
will often pass into gneiss gradually, and this again into those slaty
formations which rest upon it and come next in the series. These
consist of mica-slate, hornblend-slate, and chlorite-slate or schist,
a name given to all those rocks of a slaty structure which have a
cleavage or capability of being cleft into thin laminæ or slices (hence
their applicability to the purposes of building, forming excellent
roofing materials, &c.).
[Illustration: _Granite_ FIG. 8.]
All these rocks have received the name of "primary," they have no
appearance of being stratified or deposited in layers, which appearance
seems to be in all cases the result of having at some time been
suspended in water and thence deposited gradually as mud, sand, &c.,
time, pressure, and heat having afterwards altered their consistence.
All these consist of the earths described as composing granite,
but combined in different proportions. Above these rocks there is
a formation of a totally different composition, namely crystalline
limestone, commonly known as marble; this consists wholly of carbonate
of lime or lime in union with carbonic acid, and its crystalline state
appears to have been produced by long-continued heat and pressure.
This limestone is by many ranked amongst the primary rocks, although
it differs so entirely in its composition which exactly resembles a
formation presently to be described (the chalk); however, if this be
classed with the primary rocks, then it may be fairly said that all
above have resulted from their disintegration and reunion in different
forms, by the action of water and vital forces of different kinds. The
state of the earth at the close of this the "primary period" may now
be considered.
The early history of our globe forms one of the great problems of
geology, but there is evidence enough upon which to form conclusions
and show that the earth had undergone some great and varied changes
embracing immense periods of time, and if the sciences of astronomy,
chemistry, mathematics, &c., be brought in to assist the inquiry, some
plain facts become evident. Astronomy shows us orbs circulating round
the sun (the planets), strictly analogous to our earth, and furnishes
us with their densities; these are found to be various, ranging from
about six times the density of water to half its density. The planets
appear to be at different stages of condensation, and it is not
unreasonable to suppose that our earth was once of no greater density
than the lightest of them. The inner ring of Saturn is probably in a
liquid state, for it is transparent. The substance of which comets
are composed is a vapour, so rare and thin that it cannot be compared
in density to our atmosphere even, and yet these comets preserve
their identity, circulating through immense realms of space with
prodigious rapidity. Thus astronomy presents analogies in favour of
the supposition that the earth was once gaseous, or at all events of
much less density than at present; but mathematical inquiries go much
further, and furnish almost proof that the earth was once (if not now)
in a liquid state, for the exact form which a liquid ball would assume
upon rotating at the rate which the earth does, is exactly that which
the globe is found by measurement to possess.
Chemistry has ascertained that the heat of the earth is far greater
than any tract of the heavens through which it passes; that this heat
could not have been communicated by the sun's rays, for had it been
so the surface would be hotter than the interior, the very reverse of
which is found to be the fact, and the deeper we go down the higher
the temperature is. Chemistry shows further that this heat can be
completely accounted for by the condensation and solidification of the
earth itself; for the condensation of all gases into liquids, and of
liquids into solids, causes a very large portion of latent caloric to
become sensible, for example, any quantity of a gas at 60 deg. suddenly
reduced to a smaller bulk, would have a temperature higher than 60
deg. A little contrivance has long been in use for obtaining fire by
this process, consisting of a cylinder and piston, the rod of which
if struck down sets fire to a piece of German-tinder. It is probable
that all fire, and every alteration of temperature, are due to this one
cause alone.