OF THE PHENOMENA COMMON TO STRATIFIED
AND UNSTRATIFIED BODIES.
92. THE series of changes which fossil bodies are destined to undergo,
does not cease with their elevation above the level of the sea; it
assumes, however, a new direction, and from the moment that they are
raised up to the surface, is constantly exerted in reducing them again
under the dominion of the ocean. The solidity is now destroyed which
was acquired in the bowels of the earth; and as the bottom of the
sea is the great laboratory, where loose materials are mineralized
and formed into stone, the atmosphere is the region where stones are
decomposed, and again resolved into earth.
This decomposition of all mineral substances, exposed to the air,
is continual, and is brought about by a multitude of agents, both
chemical and mechanical, of which some are known to us, and many, no
doubt, remain to be discovered. Among the various aëriform fluids which
compose our atmosphere, one is already distinguished as the grand
principle of mineral decomposition; the others are not inactive, and
to them we must add moisture, heat, and perhaps light; substances
which, from their affinities to the elements of mineral bodies, have a
power of entering into combination with them, and of thus diminishing
the forces by which they are united to one another. By the action of
air and moisture, the metallic particles, particularly the iron, which
enters in great abundance into the composition of almost all fossils,
becomes oxydated in such a degree as to lose its tenacity; so that the
texture of the surface is destroyed, and a part of the body resolved
into earth.
93. Some earths, again, such as the calcareous, are immediately
dissolved by water; and though the quantity so dissolved be extremely
small, the operation, by being continually renewed, produces a slow
but perpetual corrosion, by which the greatest rocks must in time be
subdued. The action of water in destroying hard bodies into which it
has obtained entrance, is much assisted by the vicissitudes of heat
and cold, especially when the latter extends as far as the point of
congelation; for the water, when frozen, occupies a greater space than
before, and if the body is compact enough to refuse room for this
expansion, its parts are torn asunder by a repulsive force acting in
every direction.
94. Besides these causes of mineral decomposition, the action of which
we can in some measure trace, there are others known to us only by
their effects.
We see, for instance, the purest rock crystal affected by exposure
to the weather, its lustre tarnished, and the polish of its surface
impaired, but we know nothing of the power by which these operations
are performed. Thus also, in the precautions which the mineralogist
takes to preserve the fresh fracture of his specimens, we have a proof
how indiscriminately all the productions of the fossil kingdom are
exposed to the attacks of their unknown enemies, and we perceive how
difficult it is to delay the beginnings of a process which no power
whatever can finally counteract.
95. The mechanical forces employed in the disintegration of mineral
substances, are more easily marked than the chemical. Here again water
appears as the most active enemy of hard and solid bodies; and, in
every state, from transparent vapour to solid ice, from the smallest
rill to the greatest river, it attacks whatever has emerged above the
level of the sea, and labours incessantly to restore it to the deep.
The parts loosened and disengaged by the chemical agents, are carried
down by the rains, and, in their descent, rub and grind the superficies
of other bodies. Thus water, though incapable of acting on hard
substances by direct attrition, is the cause of their being so acted
on; and, when it descends in torrents, carrying with it sand, gravel,
and fragments of rock, it may be truly said to turn the forces of the
mineral kingdom against itself. Every separation which it makes is
necessarily permanent, and the parts once detached can never be united,
save at the bottom of the ocean.
96. But it would far exceed the limits of this sketch, to pursue
the causes of mineral decomposition through all their forms. It is
sufficient to remark, that the consequence of so many minute, but
indefatigable agents, all working together, and having _gravity_ in
their favour, is a system of universal decay and degradation, which
may be traced over the whole surface of the land, from the mountain
top to the sea shore. That we may perceive the full evidence of this
truth, one of the most important in the natural history of the globe,
we will begin our survey from the latter of these stations, and retire
gradually toward the former.
97. If the coast is bold and rocky, it speaks a language easy to
be interpreted. Its broken and abrupt contour, the deep gulfs and
salient promontories by which it is indented, and the proportion which
these irregularities bear to the force of the waves, combined with
the inequality of hardness in the rocks, prove, that the present
line of the shore has been determined by the action of the sea. The
naked and precipitous cliffs which overhang the deep, the rocks
hollowed, perforated, as they are farther advanced in the sea, and at
last insulated, lead to the same conclusion, and mark very clearly
so many different stages of decay. It is true, we do not see the
successive steps of this progress exemplified in the states of the same
individual rock, but we see them clearly in different individuals;
and the conviction thus produced, when the phenomena are sufficiently
multiplied and varied, is as irresistible, as if we saw the changes
actually effected in the moment of observation.
On such shores, the fragments of rock once detached, become instruments
of further destruction, and make a part of the powerful artillery with
which the ocean assails the bulwarks of the land: they are impelled
against the rocks, from which they break off other fragments, and the
whole are thus ground against one another; whatever be their hardness,
they are reduced to gravel, the smooth surface and round figure of
which, are the most certain proofs of a _detritus_ which nothing can
resist.
98. Again, where the sea coast is flat, we have abundant evidence of
the degradation of the land in the beaches of sand and small gravel;
the sand banks and shoals that are continually changing; the alluvial
land at the mouths of the rivers; the bars that seem to oppose their
discharge into the sea, and the shallowness of the sea itself. On
such coasts, the land usually seems to gain upon the sea, whereas,
on shores of a bolder aspect, it is the sea that generally appears
to gain upon the land. What the land acquires in extent, however, it
loses in elevation; and, whether its surface increase or diminish, the
depredations made on it are in both cases evinced with equal certainty.
99. If we proceed in our survey from the shores, inland, we meet
at every step with the fullest evidence of the same truths, and
particularly in the nature and economy of rivers. Every river appears
to consist of a main trunk, fed from a variety of branches, each
running in a valley proportioned to its size, and all of them together
forming a system of vallies, communicating with one another, and having
such a nice adjustment of their declivities, that none of them join the
principal valley, either on too high or too low a level; a circumstance
which would be infinitely improbable, if each of these vallies were not
the work of the stream that flows in it.
If indeed a river consisted of a single stream, without branches,
running in a straight valley, it might be supposed that some great
concussion, or some powerful torrent, had opened at once the channel
by which its waters are conducted to the ocean; but, when the usual
form of a river is considered, the trunk divided into many branches,
which rise at a great distance from one another, and these again
subdivided into an infinity of smaller ramifications, it becomes
strongly impressed upon the mind, that all these channels have been cut
by the waters themselves; that they have been slowly dug out by the
washing and erosion of the land; and that it is by the repeated touches
of the same instrument, that this curious assemblage of lines has been
engraved so deeply on the surface of the globe.
100. The changes which have taken place in the courses of rivers, are
also to be traced, in many instances, by successive platforms, of flat
alluvial land, rising one above another, and marking the different
levels on which the river has run at different periods of time. Of
these, the number to be distinguished, in some instances, is not less
than four, or even five; and this necessarily carries us back, like
all the operations we are now treating of, to an antiquity extremely
remote: for, if it be considered, that each change which the river
makes in its bed, obliterates at least a part of the monuments of
former changes, we shall be convinced, that only a small part of the
progression can leave any distinct memorial behind it, and that there
is no reason to think, that, in the part which we see, the beginning is
included.[29]
[Footnote 29: NOTE XVI.]
101. In the same manner, when a river undermines its banks, it often
discovers deposits of sand and gravel, that have been made when it ran
on a higher level than it does at present. In other instances, the same
strata are seen on both the banks, though the bed of the river is now
sunk deep between them, and perhaps holds as winding a course through
the solid rock, as if it flowed along the surface; a proof that it must
have begun to sink its bed, when it ran through such loose materials as
opposed but a very inconsiderable resistance to its stream. A river, of
which the course is both serpentine and deeply excavated in the rock,
is among the phenomena, by which the slow waste of the land, and also
the cause of that waste, are most directly pointed out.
102. It is, however, where rivers issue through narrow defiles among
mountains, that the identity of the strata on both sides is most easily
recognised, and remarked at the same time with the greatest wonder. On
observing the Potowmack, where it penetrates the ridge of the Allegany
mountains, or the Irtish, as it issues from the defiles of Altai,
there is no man, however little addicted to geological speculations,
who does not immediately acknowledge, that the mountain was once
continued quite across the space in which the river now flows; and, if
he ventures to reason concerning the cause of so wonderful a change,
he ascribes it to some great convulsion of nature, which has torn the
mountain asunder, and opened a passage for the waters. It is only the
philosopher, who has deeply meditated on the effects which action long
continued is able to produce, and on the simplicity of the means which
nature employs in all her operations, who sees in this nothing but the
gradual working of a stream, that once flowed over the top of the ridge
which it now so deeply intersects, and has cut its course through the
rock, in the same way, and almost with the same instrument, by which
the lapidary divides a block of marble or granite.
103. It is highly interesting to trace up, in this manner, the action
of causes with which we are familiar, to the production of effects,
which at first seem to require the introduction of unknown and
extraordinary powers; and it is no less interesting to observe, how
skilfully nature has balanced the action of all the minute causes of
waste, and rendered them conducive to the general good. Of this we
have a most remarkable instance, in the provision made for preserving
the soil, or the coat of vegetable mould, spread out over the surface
of the earth. This coat, as it consists of loose materials, is easily
washed away by the rains, and is continually carried down by the rivers
into the sea. This effect is visible to every one; the earth is removed
not only in the form of sand and gravel, but its finer particles
suspended in the waters, tinge those of some rivers continually, and
those of all occasionally, that is, when they are flooded or swollen
with rains. The quantity of earth thus carried down, varies according
to circumstances; it has been computed, in some instances, that the
water of a river in a flood, contains earthy matter suspended in it,
amounting to more than the two hundred and fiftieth part of its own
bulk.[30] The soil, therefore, is continually diminished, its parts
being transported from higher to lower levels, and finally delivered
into the sea. But it is a fact, that the soil, notwithstanding, remains
the same in quantity, or at least nearly the same, and must have done
so, ever since the earth was the receptacle of animal or vegetable
life. The soil, therefore, is augmented from other causes, just as
much, at an average, as it is diminished by that now mentioned; and
this augmentation evidently can proceed from nothing but the constant
and slow disintegration of the rocks. In the permanence, therefore,
of a coat of vegetable mould on the surface of the earth, we have a
demonstrative proof of the continual destruction of the rocks; and
cannot but admire the skill, with which the powers of the many chemical
and mechanical agents employed in this complicated work, are so
adjusted, as to make the supply and the waste of the soil exactly equal
to one another.
[Footnote 30: See Lehman, Traités de Phys. &c. tom. iii. p. 359. Note.]
104. Before we take leave of the rivers and the plains, we must remark
another fact, often observed in the natural history of the latter, and
clearly evincing the former existence of immense bodies of strata, in
situations from which they have now entirely disappeared. The fact here
alluded to is, the great quantity of round and hard gravel, often to be
met with in the soil, under such circumstances, as prove, that it can
only have come from the decomposition of rocks, that once occupied the
very ground over which this gravel is now spread. In the chalk country,
for instance, about London, the quantity of flints in the soil is every
where great; and, in particular situations, nothing but flinty gravel
is found to a considerable depth. Now, the source from which these
flints are derived is quite evident, for they are precisely the same
with those contained in the chalk beds, wherever these last are found
undisturbed, and from the destruction of such beds they have no doubt
originated. Hence a great thickness of chalk must have been decomposed,
to yield the quantity of flints now in the soil of these countries; for
the flints are but thinly scattered through the native chalk, compared
with their abundance in the loose earth. To afford, for example, such
a body of flinty gravel as is found about Kensington, what an enormous
quantity of chalk rock must have been destroyed?
105. This argument, which Dr Hutton has applied particularly to the
chalk countries, may be extended to many others. The great plain of
Crau, near the mouth of the Rhone, is well known, and was regarded
with wonder, even in ages when the natural history of the globe was
not an object of much attention. The immense quantity of large round
gravel-stones, with which this extensive plain is entirely covered,
has been supposed, by some mineralogists, to have been brought down
by the Durance, and other torrents, from the Alps; but, on further
examination, has been found to be of the same kind that is contained
in certain horizontal layers of pudding-stone, which are the basis of
the whole plain. It cannot be doubted, therefore, that the vast body of
gravel spread over it, has originated from the destruction of layers
of the same rock, which may perhaps have risen to a great height above
what is now the surface. Indeed, from knowing the depth of the gravel
that covers the plain, and the average quantity of the like gravel
contained in a given thickness of rock, one might estimate how much of
the latter has been actually worn away. Whether data precise enough
could be found, to give any weight to such a computation, must be left
fer future inquiry to determine.[31]
[Footnote 31: NOTE XVII.]
106. In these instances, chalk and pudding-stone, by containing in
them parts infinitely less destructible than their general mass, have,
after they are worn away, left behind them very unequivocal marks of
their existence. The same has happened in the case of mineral veins,
where the substances least subject to dissolution have remained,
and are scattered at a great distance from their native place. Thus
gold, the least liable to decomposition of all the metals, is very
generally diffused through the earth, and is found, in a greater or
less abundance, in the sand of almost all rivers. But the native place
of this mineral is the solid rock, or the veins and cavities contained
in the rock, and from thence it must have made its way into the soil.
This, therefore, is another proof of the vast extent to which the
degradation of the land, and of the rock, which is the basis of it,
has been earned; and consequently, of the great difference between
the elevation and shape of the earth's surface in the present, and in
former ages.
107. The veins of tin furnish an argument of the same kind. The
ores of this metal are very indestructible, and little subject to
decomposition, so that they remain very long in the ground without
change. Where there are tin veins, as in Cornwall, the tin-stone or tin
ore is found in great abundance in such vallies and streams as have
the same direction with the veins; and hence the _streaming_, as it is
called, or washing of the earth, to obtain the tin-stone from it. Now,
if it be considered, that none of this ore can have come into the soil
but from parts of a vein actually destroyed, it must appear evident
that a great waste of these veins has taken place, and consequently of
the schistus or granite in which they are contained.
108. These lessons, which the geologist is taught in flat and open
countries, become more striking, by the study of those Alpine tracts,
where the surface of the earth attains its greatest elevation. If we
suppose him placed for the first time in the midst of such a scene,
as soon as he has recovered from the impression made by the novelty
and magnificence of the spectacle before him, he begins to discover
the footsteps of time, and to perceive, that the works of nature,
usually deemed the most permanent, are those on which the characters
of vicissitude are most deeply imprinted. He sees himself in the midst
of a vast ruin, where the precipices which rise on all sides with
such boldness and asperity, the sharp peaks of the granite mountains,
and the huge fragments that surround their bases, do but mark so many
epochs in the progress of decay, and point out the energy of those
destructive causes, which even the magnitude and solidity of such great
bodies have been unable to resist.
109. The result of a more minute investigation, is in perfect unison
with this general impression. Whence is it, that the elevation
of mountains is so obviously connected with the hardness and
indestructibility of the rocks which compose them? Why is it, that a
lofty mountain of soft and secondary rock is no where to be found; and
that such chains, as the Pyrenees or the Alps, never consist of any
but the hardest stone, of granite for instance, or of those primary
strata, which, if we are to credit the preceding theory, have been
twice heated in the fires, and twice tempered in the waters, of the
mineral regions? Is it not plain that this arises, not from any direct
connection between the hardness of stones, and their height in the
atmosphere, but from this, that the waste and _detritus_ to which all
things are subject, will not allow soft and weak substances to remain
long in an exposed and elevated situation? Were it not for this, the
secondary rocks, being in position superincumbent on the primary, ought
to be the highest of the two, and should cover the primary, (as they
no doubt have at one time done,) in the highest as well as the lowest
situations, or among the mountains as well as in the plains.
110. Again, wherefore is it, that among all mountains, remarkable for
their ruggedness and asperity, the rock, on examination, is always
found of very unequal destructibility, some parts yielding to the
weather, and to the other causes of disintegration, much more slowly
than the rest, and having strength sufficient to support themselves,
when left alone, in slender pyramids, bold projections, and overhanging
cliffs? Where, on the other hand, the rock wastes uniformly, the
mountains are similar to one another; their swells and slopes are
gentle, and they are bounded by a waving and continuous surface. The
intermediate degrees of resistance which the rocks oppose to the causes
of destruction, produce intermediate forms. It is this which gives to
the mountains, of every different species of rock, a different habit
and expression, and which, in particular, has imparted to those of
granite that venerable and majestic character, by which they rarely
fail to be distinguished.
111. The structure of the vallies among mountains, shows clearly to
what cause their existence is to be ascribed. Here we have first a
large valley, communicating directly with the plain, and winding
between high ridges of mountains, while the river in the bottom of it
descends over a surface, remarkable, in such a scene, for its uniform
declivity. Into this, open a multitude of transverse or secondary
vallies, intersecting the ridges on either side of the former, each
bringing a contribution to the main stream, proportioned to its
magnitude; and, except where a cataract now and then intervenes,
all having that nice adjustment in their levels, (99.) which is the
more wonderful, the greater the irregularity of the surface. These
secondary vallies have others of a smaller size opening into them;
and, among mountains of the first order, where all is laid out on the
greatest scale, these ramifications are continued to a fourth, and
even a fifth, each diminishing in size as it increases in elevation,
and as its supply of water is less. Through them all, this law is in
general observed, that where a higher valley joins a lower one, of the
two angles which it makes with the latter, that which is obtuse is
always on the descending side; a law that is the same with that which
regulates the confluence of streams running on a surface nearly of
uniform inclination. This alone is a proof that the vallies are the
work of the streams; and indeed what else but the water itself, working
its way through obstacles of unequal resistance, could have opened or
kept up a communication between the inequalities of an irregular and
alpine surface?
112. Many more arguments, all leading to the same conclusion, may
be deduced from the general facts, known in the natural history of
mountains; and, if the Oreologist would trace back the progress of
waste, till he come in sight of that original structure, of which
the remains are still so vast, he perceives an immense mass of solid
rock, naked and unshapely, as it first emerged from the deep, and
incomparably greater than all that is now before him. The operation
of rains and torrents, modified by the hardness and tenacity of the
rock, has worked the whole into its present form; has hollowed out
the vallies, and gradually detached the mountains from the general
mass, cutting down their sides into steep precipices at one place,
and smoothing them into gentle declivities at another. From this has
resulted a transportation of materials, which, both for the quantity
of the whole, and the magnitude of the individual fragments, must seem
incredible to every one, who has not learned to calculate the effects
of continued action, and to reflect, that length of time can convert
accidental into steady causes. Hence fragments of rock, from the
central chain, are found to have travelled into distant vallies, even
where many inferior ridges intervene: hence the granite of Mont Blanc
is seen in the plains of Lombardy, or on the sides of Jura; and the
ruins of the Carpathian mountains lie scattered over the shores of the
Baltic.[32]
[Footnote 32: NOTE XVIII.]
113. Thus, with Dr Hutton, we shall be disposed to consider those great
chains of mountains, which traverse the surface of the globe, as cut
out of masses vastly greater, and more lofty than any thing that now
remains. The present appearances afford no data for calculating the
original magnitude of these masses, or the height to which they may
have been elevated. The nearest estimate we can form is, where a chain
or group of mountains, like those of Rosa in the Alps, is horizontally
stratified, and where, of consequence, the undisturbed position of the
mineral beds enables us to refer the whole of the present inequalities
of the surface to the operation of waste or decay. These mountains,
as they now stand, may not inaptly be compared to the pillars of earth
which workmen leave behind them, to afford a measure of the whole
quantity of earth which they have removed. As the pillars, (considering
the mountains as such,) are in this case of less height than they
originally were, so the measure furnished by them is but a limit, which
the quantity sought must necessarily exceed.
114. Such, according to Dr Hutton's theory, are the changes which the
daily operations of waste have produced on the surface of the globe.
These operations, inconsiderable if taken separately, become great, by
conspiring all to the same end, never counteracting one another, but
proceeding, through a period of indefinite extent, continually in the
same direction. Thus every thing descends, nothing returns upward; the
hard and solid bodies every where dissolve, and the loose and soft no
where consolidate. The powers which tend to preserve, and those which
tend to change the condition of the earth's surface, are never _in
equilibrio_; the latter are, in all cases, the most powerful, and, in
respect of the former, are like living in comparison of dead forces.
Hence the law of decay is one which suffers no exception: The elements
of all bodies were once loose and unconnected, and to the same state
nature has appointed that they should all return.
115. It affords no presumption against the reality of this progress,
that, in respect of man, it is too slow to be immediately perceived:
The utmost portion of it to which our experience can extend, is
evanescent, in comparison with the whole, and must be regarded as the
momentary increment of a vast progression, circumscribed by no other
limits than the duration of the world. TIME performs the office of
integrating the infinitesimal parts of which this progression is made
up; it collects them into one sum, and produces from them an amount
greater than any that can be assigned.
116. While on the surface of the earth so much is every where going to
decay, no new production of mineral substances is found in any region
accessible to man. The instances of what are called petrifactions, or
the formation of stony substances by means of water, which we sometimes
observe, whether they be ferruginous concretions, or calcareous, or,
as happens in some rare cases, siliceous stalactites, are too few
in number, and too inconsiderable in extent, to be deemed material
exceptions to this general rule. The bodies thus generated, also, are
no sooner formed, than they become subject to waste and dissolution,
like all the other hard substances in nature; so that they but retard
for a while the progress by which they are all resolved into dust, and
sooner or later committed to the bosom of the deep.
117. We are not, however, to imagine, that there is no where any means
of repairing this waste; for, on comparing the conclusion at which
we are now arrived, viz. that the present continents are all going
to decay, and their materials descending into the ocean, with the
proposition first laid down, that these same continents are composed
of materials which must have been collected from the decay of former
rocks, it is impossible not to recognise two corresponding steps of
the same progress; of a progress, by which mineral substances are
subjected to the same series of changes, and alternately wasted away
and renovated. In the same manner, as the present mineral substances
derive their origin from substances similar to themselves; so, from the
land now going to decay, the sand and gravel forming on the sea shore,
or in the beds of rivers; from the shells and corals, which in such
enormous quantities are every day accumulated in the bosom of the sea;
from the drift wood, and the multitude of vegetable and animal remains
continually deposited in the ocean: from all these we cannot doubt,
that strata are now forming in those regions, to which nature seems
to have confined the powers of mineral reproduction; from which, after
being consolidated, they are again destined to emerge, and to exhibit a
series of changes similar to the past.[33]
[Footnote 33: NOTE XIX.]
118. How often these vicissitudes of decay and renovation have been
repeated, is not for us to determine: they constitute a series, of
which, as the author of this theory has remarked, we neither see the
beginning nor the end; a circumstance that accords well with what
is known concerning other parts of the economy of the world. In the
continuation of the different species of animals and vegetables that
inhabit the earth, we discern neither a beginning nor an end; and,
in the planetary motions, where geometry has carried the eye so far
both into the future and the past, we discover no mark, either of
the commencement or the termination of the present order.[34] It is
unreasonable, indeed, to suppose, that such marks should any where
exist. The Author of nature has not given laws to the universe, which,
like the institutions of men, carry in themselves the elements of their
own destruction. He has not permitted, in his works, any symptom of
infancy or of old age, or any sign by which we may estimate either
their fixture or their past duration. He may put an end, as be no doubt
gave a beginning, to the present system, at some determinate period;
but we may safely conclude, that this great _catastrophe_ will not
be brought about by any of the laws now existing, and that it is not
indicated by any thing which we perceive.
[Footnote 34: NOTE XX.]
119. To assert, therefore, that, in the economy of the world, we see
no mark, either of a beginning or an end, is very different from
affirming, that the world had no beginning, and will have no end. The
first is a conclusion justified by common sense, as well as sound
philosophy; while the second is a presumptuous and unwarrantable
assertion, for which no reason from experience or analogy can ever be
assigned. Dr Hutton might, therefore, justly complain of the uncandid
criticism, which, by substituting the one of these assertions for the
other, endeavoured to load his theory with the reproach of atheism and
impiety. Mr KIRWAN, in bringing forward this harsh and ill-founded
censure, was neither animated by the spirit, nor guided by the maxims
of true philosophy. By the spirit of philosophy, he must have been
induced to reflect, that such poisoned weapons as he was preparing
to use, are hardly ever allowable in scientific contest, as having
a less direct tendency to overthrow the system, than to hurt the
person of an adversary, and to wound, perhaps incurably, his mind, his
reputation, or his peace. By the maxims of philosophy, he must have
been reminded, that, in no part of the history of nature, has any mark
been discovered, either of the beginning or the end of the present
_order_; and that the geologist sadly mistakes, both the object of his
science and the limits of his understanding, who thinks it his business
to explain the means employed by INFINITE WISDOM for establishing the
laws which now govern the world.
By attending to these obvious considerations, Mr Kirwan would have
avoided a very illiberal and ungenerous proceeding; and, however he
might have differed from Dr Hutton as to the _truth_ of his opinions,
he would not have censured their _tendency_ with such rash and
unjustifiable severity.
But, if this author may be blamed for wanting the temper, or neglecting
the rules, of philosophic investigation, he is hardly less culpable,
for having so slightly considered the scope and spirit of a work which
he condemned so freely. In that work, instead of finding the world
represented as the result of necessity or chance, which might be looked
for, if the accusations of atheism or impiety were well founded, we
see every where the utmost attention to discover, and the utmost
disposition to admire, the instances of wise and beneficent design
manifested in the structure, or economy of the world. The enlarged
views of these, which his geological system afforded, appeared to Dr
Hutton himself as its most valuable result. They were the parts of it
which he contemplated with greatest delight; and he would have been
less flattered, by being told of the ingenuity and originality of his
theory, than of the addition which it had made to our knowledge of
_final causes_. It was natural, therefore, that he should be hurt by
an attempt to accuse him of opinions, so different from those which he
had always taught; and if he answered Mr Kirwan's attack with warmth or
asperity, we must ascribe it to the indignation excited by unmerited
reproach.
120. But to return to the natural history of the earth: Though there be
in it no _data_, from which the commencement of the present order can
be ascertained, there are many by which the existence of that order may
be traced back to an antiquity extremely remote. The beds of primitive
schistus, for instance, contain sand, gravel, and other materials,
collected, as already shown, from the dissolution of mineral bodies;
which bodies, therefore, must have existed long before the oldest part
of the present land was formed. Again, in this gravel we sometimes find
pieces of sandstone, and of other compound rocks, by which we are of
course carried back a step farther, so as to reach a system of things,
from which the present is the third in succession; and this may be
considered as the most ancient epocha, of which any memorial exists in
the records of the fossil kingdom.
121. Next in the order of time to the consolidation of the primary
strata, we must place their elevation, when, from being horizontal, and
at the bottom of the sea, they were broken, set on edge, and raised to
the surface. It is even probable, as formerly observed, that to this
succeeded a depression of the same strata, and a second elevation,
so that they have twice visited the superior, and twice the inferior
regions. During the second immersion, were formed, first, the great
bodies of pudding-stone, that in so many instances lie immediately
above them; and next were deposited the strata that are strictly
denominated secondary.
122. The third great event, was the raising up of this compound body of
old and new strata from the bottom of the sea, and forming it into the
dry land, or the continents, as they now exist.[35] Contemporary with
this, we must suppose the injection of melted matter among the strata,
and the consequent formation of the crystallized and unstratified
rocks, namely, the granite, metallic veins, and veins of porphyry and
whinstone. This, however, is to be considered as embracing a period
of great duration; and it must always be recollected, that veins are
found of very different formation; so that when we speak generally, it
is perhaps impossible to state any thing more precise concerning their
antiquity, than that they are posterior to the strata, and that the
veins of whinstone seem to be the most recent of all, as they traverse
every other.
[Footnote 35: NOTE XXI.]
123. In the fourth place, with respect to time, we must class the
facts that regard the detritus and waste of the land, and must
carefully distinguish them from the more ancient phenomena of the
mineral kingdom. Here we are to reckon the shaping of all the present
inequalities of the surface; the formation of hills of gravel, and
of what have been called tertiary strata, consisting of loose and
unconsolidated materials; also collections of shells not mineralised,
like those in Turaine; such petrifactions as those contained in the
rock of Gibraltar, on the coast of Dalmatia, and in the caves of
Bayreuth. The bones of land animals found in the soil, such as those
of Siberia, or North America, are probably more recent than any of the
former.[36]
[Footnote 36: NOTE XXII.]
124. These phenomena, then, are all so many marks of the lapse of
time, among which the principles of geology enable us to distinguish
a certain order, so that we know some of them to be more, and others
to be less distant, but without being able to ascertain, with any
exactness, the proportion of the immense intervals which separate them.
These intervals admit of no comparison with the astronomical measures
of time; they cannot be expressed by the revolutions of the sun or of
the moon; nor is there any synchronism between the most recent epoch as
of the mineral kingdom, and the most ancient of our ordinary chronology.
125. On what is now said is grounded another objection to Dr Hutton's
theory, namely, that the high antiquity ascribed by it to the earth,
is inconsistent with that system of chronology which rests on the
authority of the Sacred Writings. This objection would no doubt be of
weight, if the high antiquity in question were not restricted merely to
the globe of the earth, but were also extended to the human race. That
the origin of mankind does not go back beyond six or seven thousand
years, is a position so involved in the narrative of the Mosaic books,
that any thing inconsistent with it, would no doubt stand in opposition
to the testimony of those ancient records. On this subject, however,
geology is silent; and the history of arts and sciences, when traced
as high as any authentic monuments extend, refers the beginnings of
civilization to a date not very different from that which has just been
mentioned, and infinitely within the limits of the most recent of the
epoch as, marked by the physical revolutions of the globe.
On the other hand, the authority of the Sacred Books seems to be but
little interested in what regards the mere antiquity of the earth
itself; nor does it appear that their language is to be understood
literally concerning the _age_ of that body, any more than concerning
its _figure_ or its _motion_. The theory of Dr Hutton stands here
precisely on the same footing with the system of COPERNICUS; for
there is no reason to suppose, that it was the purpose of revelation
to furnish a standard of geological, any more than of astronomical
science. It is admitted, on all hands, that the Scriptures are not
intended to resolve physical questions, or to explain matters in no
way related to the morality of human actions; and if, in consequence
of this principle, a considerable latitude of interpretation were not
allowed, we should continue at this moment to believe, that the earth
is flat; that the sun moves round the earth; and that the circumference
of a circle is no more than three times its diameter.
It is but reasonable, therefore, that we should extend to the
geologist the same liberty of speculation, which the astronomer and
mathematician are already in possession of; and this may be done,
by supposing that the chronology of MOSES relates only to the human
race. This liberty is not more necessary to Dr Hutton than to other
theorists. No ingenuity has been able to reconcile the natural history
of the globe with the opinion of its recent origin; and accordingly
the cosmologies of Kirwan and De Luc, though contrived with more
mineralogical skill, are not less forced and unsatisfactory than those
of Burnet and Whiston.
126. It is impossible to look back on the system which we have thus
endeavoured to illustrate, without being struck with the novelty and
beauty of the views which it sets before us. The very plan and scope
of it distinguish it from all other theories of the earth, and point
it out as a work of great and original invention. The sole object of
such theories has hitherto been, to explain the manner in which the
present laws of the mineral kingdom were first established, or began to
exist, without treating of the manner in which they now proceed, and by
which their continuance is provided for. The authors of these theories
have accordingly gone back to a state of things altogether unlike the
present, and have confined their reasonings, or their fictions, to a
crisis which never has existed but once, and which never can return.
Dr Hutton, on the other hand, has guided his investigation by the
philosophical maxim, _Causam naturalem et assiduam quærimus, non raram
et fortuitam_. His theory, accordingly, presents us with a system of
wise and provident economy, where the same instruments are continually
employed, and where the decay and renovation of fossils being carried
on at the same time in the different regions allotted to them, preserve
in the earth the conditions essential for the support of animal and
vegetable life. We have been long accustomed to admire that beautiful
contrivance in nature, by which the water of the ocean, drawn up in
vapour by the atmosphere, imparts, in its descent, fertility to the
earth, and becomes the great cause of vegetation and of life; but now
we find, that this vapour not only fertilizes, but creates the soil;
prepares it from the solid rock, and, after employing it in the great
operations of the surface, carries it back into the regions where all
its mineral characters are renewed. Thus, the circulation of moisture
through the air, is a prime mover, not only in the annual succession
of the seasons, but in the great geological cycle, by which the waste
and reproduction of entire continents is circumscribed. Perhaps a more
striking view than this, of the wisdom that presides over nature, was
never presented by any philosophical system, nor a greater addition
ever made to our knowledge of final causes. It is an addition which
gives consistency to the rest, by proving, that equal foresight is
exerted in providing for the whole and for the parts, and that no
less a care is taken to maintain the constitution of the earth, than
to preserve the tribes of animals and vegetables which dwell on its
surface. In a word, it is the peculiar excellence of this theory, that
it ascribes to the phenomena of geology an order similar to that which
exists in the provinces of nature with which we are best acquainted;
that it produces seas and continents, not by accident, but by the
operation of regular and uniform causes; that it makes the decay of one
part subservient to the restoration of another, and gives stability to
the whole, not by perpetuating individuals, but by reproducing them in
succession.
127. Again, in the detail of this theory, and the ample induction on
which it is founded, we meet with many facts and observations, either
entirely new, or hitherto very imperfectly understood. Thus, the veins
which proceed from masses of granite, and penetrate the incumbent
schistus, had either escaped the observation of former mineralogists,
or the importance of the phenomenon had been entirely overlooked. Dr
Hutton has described the appearances with great accuracy, and drawn
from them the most interesting conclusions. At the junction of the
primary and secondary strata, the facts which he has noted had been
observed by others; but no one I think had so fully understood the
language which they speak, or had so clearly perceived the consequences
that necessarily follow from them. He is the first who distinctly
pointed out the characters which distinguish whinstone from lava, and
who explained the true relation that subsists between these substances.
He also discovered the induration of the strata, in contact with veins
of whin, and the charring of the coal in their vicinity. His theory
also enabled him to determine the affinity of whinstone and granite
to one another, and their relation to the other great bodies of the
mineral kingdom.
To the observations of the same excellent geologist, we are indebted
for the knowledge of the general and important fact, that all the hard
substances of the mineral kingdom, when elevated into the atmosphere,
have a tendency to decay, and are subject to a disintegration
and waste, to which no limit can be set but that of their entire
destruction; that no provision is made on the surface for repairing
this waste, and that there, no new fossil is produced; that the
formation of all the varied scenery which the surface of the earth
exhibits, depends on the operation of causes, the momentary exertions
of which are familiar to us, though we knew not before the effects
which their accumulated action was able to produce. These are facts in
the natural history of the earth, the discovery of which is due to Dr
Hutton; and, should we lay all further speculation aside, and consider
the theory of the earth as a work too great to be attempted by man, we
must still regard the phenomena and laws just mentioned, as forming a
solid and valuable addition to our knowledge.
128. If we would compare this theory with others, as to the invisible
agents which it employs, we must consider, that fire and water are the
two powers which all of them must make use of, so that they can differ
from one another only by the way in which they combine these powers.
In Dr Hutton's system, water is first employed to deposit and arrange,
and then fire to consolidate, mineralize, and lastly, to elevate
the strata; but with respect to the unstratified or crystallized
substances, the action of fire only is recognised. The system having
least affinity to this is the Neptunian, which ascribes the formation
of all minerals to the action of water alone, and extends this
hypothesis even to the unstratified rocks. Here, therefore, the action
of fire is entirely excluded; and the Neptunists have certainly made a
great sacrifice to the love of truth, or of paradox, in rejecting the
assistance of so powerful an auxiliary.[37]
[Footnote 37: NOTE XXIII.]
129. In the systems which employ the agency of the latter element, we
are to look for a greater resemblance to that of Dr Hutton, though
many and great marks of distinction are easily perceived. In the
cosmologies, for example, of LEIBNITZ and BUFFON, fire and water are
both employed, as well as in this; but they are employed in a reverse
order. These philosophers introduce the action of fire first, and
then the action of water, which is to invert the order of nature
altogether, as the consolidation of the rocks must be posterior to
their stratification. Indeed, the theory of Buffon is singularly
defective: besides inverting the order of the two great operations
of stratification and consolidation, and of course giving no real
explanation of the latter, it gives no account of the elevation, or
highly inclined position of the strata; it makes no distinction between
stratified and unstratified bodies, nor does it offer any but the most
unsatisfactory explanation of the inequalities of the earth's surface.
This system, therefore, has but a very distant resemblance to the
Huttonian theory.[38]
[Footnote 38: NOTE XXIV.]
130. The system of LAZZARO MORO has been remarked as approaching nearer
to this theory than any other; and it is certain, that one very
important principle is common to them both. The theory of the Italian
geologist was chiefly directed to the explanation of the remains of
marine animals, which are found in mountains far from the sea; and it
appears to have been suggested to him by the phenomena of the _Campi
Phlegræi_, and by the production of the new island of _Santorini_
in the Archipelago. He accordingly supposes, that the islands and
continents have been all raised up, like the above-mentioned island,
from the bottom of the sea, by the force of volcanic fire: that
these fires began to burn under the bottom of the ocean, soon after
the creation of the world, when as yet the ocean covered the whole
earth: that they at first elevated a portion of the land; and in this
primitive land no shells are found, as the original ocean was destitute
of fish. The volcanoes continuing to burn, under the sea, after the
creation of animated nature, the strata that were then raised up by
their action were full of shells and other marine objects; and, from
the violence with which they were elevated, arose the contortions and
inclined position which they frequently possess.[39]
[Footnote 39: Dé Crostacei, et degli altri Marini Corpi, che si trovano
su' Monti: di Ant. Lazzaro Moro. Venezia. 1740.]
This system is imperfect, as it makes no peculiar provision for the
consolidation of the strata, which, according to it, as well as the
Neptunian system, must be ascribed to the action, not of fire, but of
water. No account is given of the mineralization of the shells found
in the strata, or of the difference between them and the shells found
loose at the bottom of the sea; and no distinction is made between
stratified and unstratified substances. But, with all this, Lazzaro
Moro has certainly the merit of having perceived, that some other power
than that which deposited the strata, must have been employed for their
elevation, and that they have endured the action of a disturbing force.
131. From this comparison it appears, that Dr Hutton's theory is
sufficiently distinct, even from the theories which approach to it most
nearly, to merit, in the strictest sense, the appellation of _new_ and
_original_. There are indeed few inventions or discoveries, recorded
in the history of science, to which nearer approaches were not made
before they were fully unfolded. It therefore very well deserves to be
distinguished by a particular name; and, if it behoves us to follow
the analogy observed in the names of the two great systems, which at
present divide the opinions of geologists, we may join Mr Kirwan in
calling this the PLUTONIC SYSTEM. For my own part, I would rather
have it characterized by a less splendid, but juster name, that of the
HUTTONIAN THEORY.
132. The circumstance, however, which gives to this theory its
peculiar character, and exalts it infinitely above all others, is
the introduction of the principle of pressure, to modify the effects
of heat when applied at the bottom of the sea. This is in fact the
key to the grand enigma of the mineral kingdom, where, while one
set of phenomena indicates the action of fire, another set, equally
remarkable, seems to exclude the possibility of that action, by
presenting us with mineral substances, in such a state as they could
never have been brought into by the operation of the fires we see at
the surface of the earth. These two classes of phenomena are reconciled
together, by admitting the power of compression to confine the volatile
parts of bodies when heat is applied to them, and to force them,
in many instances, to undergo fusion, instead of being calcined or
dissipated by burning or inflammation. In this hypothesis, which some
affect to consider as a principle gratuitously assumed, there appears
to me nothing but a very fair and legitimate generalization of the
properties of heat. Combustion and inflammation are chemical processes,
to which other conditions are required, besides the presence of a high
temperature. The state of the mineral regions makes it reasonable
to presume, that these conditions are wanting in the bowels of the
earth, where, of consequence, we have a right to look for nothing but
expansion and fusion, the only operations which seem essential to
heat, and inseparable from the application of it, in certain degrees,
to certain substances. Though this principle, therefore, had no
countenance from analogy, the admirable simplicity, and the unity,
which it introduces into the phenomena of geology, would sufficiently
justify the application of it to the theory of the earth.
As another excellence of this theory, I may, perhaps, be allowed to
remark, that it extends its consequences beyond those to which the
author of it has himself adverted, and that it affords, which no
geological theory has yet done, a satisfactory explanation of the
spheroidal figure of the earth.[40]
[Footnote 40: NOTE XXV.]
133. Yet, with all these circumstances of originality, grandeur,
and simplicity in its favour, with the addition of evidence as
demonstrative as the nature of the subject will admit, this theory
has probably many obstacles to overcome, before it meet the general
approbation. The greatness of the objects which it sets before us,
alarms the imagination; the powers which it supposes to be lodged
in the subterraneous regions; a heat which has subdued the most
refractory rocks, and has melted beds of marble and quartz; an
expansive force, which has folded up, or broken the strata, and raised
whole continents from the bottom of the sea; these are things with
which, however certainly they may be proved, the mind cannot soon
be familiarized. The change and movement also, which this theory
ascribes to all that the senses declare to be most unalterable, raise
up against it the same prejudices which formerly opposed the belief
in the true system of the world; and it affords a curious proof, how
little such prejudices are subject to vary, that as Aristarchus, an
ancient follower of that system, was charged with impiety for moving
the everlasting Vesta from her place, so Dr Hutton, nearly on the same
ground, has been subjected to the very same accusation. Even the length
of time which this theory regards as necessary to the revolutions of
the globe, is looked on as belonging to the marvellous; and man, who
finds himself constrained by the want of time, or of space, in almost
all his undertakings, forgets, that in these, if in any thing, the
riches of nature reject all limitation.[41]
[Footnote 41: NOTE XXVI.]
The evidence which must be opposed to all these causes of incredulity,
cannot be fully understood without much study and attention. It
requires not only a careful examination of particular instances, but
comprehensive views of the whole phenomena of geology; the comparison
of things very remote with one another; the interpretation of the
_obscure_ by the _luminous_, and of the _doubtful_ by the _decisive_
appearances. The geologist must not content himself with examining
the insulated specimens of his cabinet, or with pursuing the nice
subtleties of mineralogical arrangement; he must study the relations of
fossils, as they actually exist; he must follow nature into her wildest
and most inaccessible abodes; and must select, for the places of his
observations, those points, from which the variety and gradation of her
works can be most extensively and accurately explored. Without such an
exact and comprehensive survey, his mind will hardly be prepared to
relish the true theory of the earth. "_Naturæ enim vis atque majestas
omnibus momentis fide caret, si quis modo partes atque non totam
complectatur animo_".[42]
[Footnote 42: PLIN. Hist. Nat. lib. vii. Cap. i.]
134. If indeed this theory of the earth is as well founded as we
suppose it to be, the lapse of time must necessarily remove all
objections to it, and the progress of science will only develope its
evidence more fully. As it stands at present, though true, it must be
still imperfect; and it cannot be doubted, that the great principles
of it, though established on an immoveable basis, must yet undergo
many modifications, requiring to be limited, in one place, or to be
extended, in another. A work of such variety and extent cannot be
carried to perfection by the efforts of an individual. Ages may be
required to fill up the bold outline which Dr Hutton has traced with so
masterly a hand; to detach the parts more completely from the general
mass; to adjust the size and position of the subordinate members; and
to give to the whole piece the exact proportion and true colouring of
nature.
This, however, in length of time, may be expected from the advancement
of science, and from the mutual assistance which parts of knowledge,
seemingly the most remote, often afford to one another. Not only
may the observations of the mineralogist, in tracts yet unexplored,
complete the enumeration of geological facts; and the experiments of
the chemist, on substances not yet subjected to his analysis, afford a
more intimate acquaintance with the nature of fossils, and a measure
of the power of those chemical agents to which this theory ascribes
such vast effects: but also, from other sciences, less directly
connected with the natural history of the earth, much information may
be received. The accurate geographical maps and surveys which are now
making; the foundings; the obsevations of currents; the barometrical
measurements, may all combine to ascertain the reality, and to fix the
quantity of those changes which terrestrial bodies continually undergo.
Every new improvement in science affords the means of delineating more
accurately the face of nature as it now exists, and of transmitting, to
future ages, an account, which may be compared with the face of nature
as it shall then exist. If, therefore, the science of the present times
is destined to survive the physical revolutions of the globe, the
HUTTONIAN THEORY may be confirmed by historical record; and the author
of it will be remembered among the illustrious few, whose systems
have been verified by the observations of succeeding ages, supported
by facts unknown to themselves, and established by the decisions of a
tribunal, slow, but infallible, in distinguishing between truth and
falsehood.
====================================
NOTES AND ADDITIONS.
====================================
NOTES AND ADDITIONS.
NOTE I. § 2.
_Origin of calcareous rocks._
135. IT has been asserted, that Dr Hutton went farther than is stated
at § 2, and maintained all calcareous matter to be _originally_ of
animal formation. This position, however, is so far from being laid
down by Dr Hutton, that it belongs to an inquiry which he carefully
avoided to enter on, as being altogether beyond the limits of
philosophical investigation.
He has indeed no where treated of the _first origin_ of any of the
earths, or of any substance whatsoever, but only of the transformations
which bodies have undergone since the present laws of nature were
established. He considered this last as all that a science, built on
experiment and observation, can possibly extend to; and willingly left,
to more presumptuous inquirers, the task of carrying their reasonings
beyond the boundaries of nature, and of unfolding the properties of
the chaotic fluid, with as much minuteness of detail, as if they were
describing the circumstances of a chemical process which they had
actually witnessed.
The idea of calcareous matter which really belongs to the Huttonian
Theory, is, that in all the changes which the terraqueous globe has
undergone in past ages, this matter existed, as it does now, either
in the form of limestone and marble, or in the composition of other
stones, or in the state of corals, shells, and bones of animals. It may
be true, that there is no particle of calcareous matter, at present
existing on the surface of the earth, that has not, at some time, made
a part of an animal body; but of this we can have no certainty, nor is
it of any importance that we should. It is enough to know, that the
rocks of marble and limestone contain in general marks of having been
formed from materials collected at the bottom of the sea; and of this
a single cockle-shell, or piece of coral, found included in a rock, is
a sufficient proof with respect to the whole mass of which it makes a
part.
The principal object which Dr Hutton had in view when he spoke of the
masses of marble and limestone, as composed of the calcareous matter
of marine bodies,[43] was to prove, that they had been all formed
at the bottom of the sea, and from materials there deposited. His
general conclusion is, "That all the strata of the earth, not only
those consisting of such calcareous masses, but others superincumbent
upon these, have had their origin at the bottom of the sea, by the
collection of sand and gravel, of shells, of coralline and crustaceous
bodies, and of earths and clays variously mixed, or separated and
accumulated. This is a general conclusion, well authenticated by the
appearances of nature, and highly important in the natural history of
the earth."[44]
[Footnote 43: Theory of the Earth, vol. i. p. 23, 24.]
[Footnote 44: Theory of the Earth, vol. i. p. 26.]
136. In his Geological Essays, Mr Kirwan says, that "some geologists,
as Buffon, and of late Dr Hutton, have excluded calcareous earth from
the number of the primeval, asserting the masses of it we at present
behold to proceed from shell-fish. But, in addition to the unfounded
supposition, that shell-fish, or any animals, possess the power of
producing any simple earth, these philosophers should have considered,
that, before the existence of any fish, the stony masses that inclose
the bason of the sea, must have existed; and, among these, there is
none in which calcareous earth is not found. Dr Hutton endeavours to
_evade_ this argument, by supposing the world we now inhabit to have
arisen from the ruins and fragments of an anterior, without pointing
at any original. If we are thus to proceed _in infinitum_, I shall not
pretend to follow him; but, if he stops any where, he will find the
same argument equally to occur."[45]
[Footnote 45: Geol. Essays, p. 13.]
The argument here employed would certainly be conclusive against any
one, who, in disputing about the _first origin_ of things, should deny
that the calcareous is as ancient as any other of the simple earths.
But this has nothing to do with Dr Hutton's speculations, which, as has
been just said, never extended to the _first origin_ of substances,
but were confined entirely to their changes; so that what he asserts
concerning the calcareous rocks, is no more than that those which we
now see have been formed from loose materials, deposited at the bottom
of the sea. It was not therefore in order to _evade_ Mr Kirwan's
argument, as the preceding passage would lead us to believe, that he
supposed the world which we now inhabit to have arisen from the ruin
and waste of an anterior world; but it was because this seemed to him
a conclusion which necessarily followed from the phenomena of geology,
and it was a conclusion that he had deduced long before he heard of Mr
Kirwan's objections to his system. Instead of an _evasion_, therefore,
any one who considers the subject fairly, will see, in Dr Hutton's
reasoning, nothing but the caution of a philosopher, who wisely
confines his theory within the same limits by which nature has confined
his experience and observation.
It is nevertheless true, that Dr Hutton has sometimes expressed himself
as if he thought that the present calcareous rocks are all composed of
animal remains.[46] This conclusion, however, is more general than the
facts warrant; and, from some incorrectness or ambiguity of language,
is certainly more general than he intended. The idea of calcareous
rocks, on which he argues throughout his whole theory, is precisely
that which is stated in the preceding article.
[Footnote 46: Theory of the Earth, vol. i. p. 23.]
NOTE II. § 6.
_Origin of coal._
137. The vegetable origin of coal seems to be sufficiently proved by
the reasoning in § 5. and 6.; and that reasoning will appear still
more satisfactory, from what is said at § 28. and 29., concerning the
consolidation of this fossil. Dr Hutton has treated both of the matter
of coal and of its consolidation. Part. I. Chap. 8., of his Theory of
the Earth [47].
[Footnote 47: Vol. i. p. 558, &c.]
The notion, however, that coal is of vegetable origin, is not peculiar
to this theory, but has been for some time the prevailing opinion.
Buffon supposes this mineral to be formed from vegetable and animal
substances, the oil and fat of which have been converted into bitumen
by the action of acids.[48] A fundamental mistake, however, is
committed by this author, and by M. GENSANNE, (author of the natural
history of Languedoc,) on whose observations he greatly relies, in
considering coal as consisting of bitumen united to earth, thus
omitting the only ingredient essential to coal, namely the carbon or
charcoal. This may truly be considered as the essential part, because
coal may exist without bitumen, as in the instance of blind coal, but
not without charcoal.
[Footnote 48: Hist. Nat. des Mineraux. tom. i. p. 429, 4to edit.]
Another theory of coal, very analogous to Dr Hutton's, is that of
ARDUINO, professor of mineralogy at Venice, in which he supposes it
formed from vegetable and animal remains from the land and sea, but
chiefly from the latter.[49] This theory of coal is contained in Dr
Hutton's, in which the animal and vegetable remains must be supposed
to come both from the earth and the sea. It seems to be without any
good reason that Arduino considers the sea as the chief source of these
materials. His remarks, however, are very ingenious, and deserving of
attention.
[Footnote 49: Saggio Fisico-mineralogico del Sig. Giov. Arduino; Atti
di Siena, tom. v. p. 228, 281, &c.]
These accounts of the origin of coal are all nearly the same; it is
in what relates to the distinction between the common coal, in which
there is no ligneous structure, and those varieties of it in which that
structure is apparent, and again in explaining the consolidation of
both, that the theory laid down here is peculiar.
138. Some other mineralogists refer one of the ingredients of coal
to the vegetable kingdom, but not the other. Unable to resist the
conviction which arises from the fibrous structure of parts of strata,
and even entire strata of coal, they have supposed, that wood, which
had been somehow buried in the earth, or perhaps deposited at the
bottom of the sea, had become impregnated with bitumen, which last,
however, they consider as of mineral origin. This appears to be the
opinion of Lehman; and also of some very late writers. There seems,
however, to be hardly less reason for referring the origin of one part
of coal to the vegetable or animal kingdom than another. The two last
are certainly capable of furnishing both the carbonic and bituminous
parts; and therefore, to derive these from different sources, is at
least a very unnecessary complication of hypotheses.
139. Another explanation of coal, very different from any of the
preceding, has lately been advanced and set up in opposition to the
Huttonian Theory. Mr Kirwan,[50] the only mineralogist, I believe, who
has attempted to derive both the carbonic and bituminous matter of coal
from the mineral kingdom, distinguishes between wood coal and mineral
coal, and gives a theory entirely new of the formation of the latter.
Wood coal is that in which the ligneous structure is so apparent, as to
leave no doubt of its vegetable origin; mineral coal is that in which
no such structure can be discovered, and is the same which Dr Hutton
derives from the vegetable juices, and other remains, comminuted,
dispersed, carried into the sea, and there precipitated, so as to
unite with different proportions of earth, and to become afterwards
mineralized.
[Footnote 50: Geol. Essays, essay vii. p. 290.]
These two species of coal, which the Huttonian theory considers as
gradations of the same substance, Mr Kirwan regards as perfectly
distinct, constituting two minerals, of an origin and formation
entirely different. He therefore endeavours to ascertain the
distinguishing characters of each, considered geologically.
140. But here the leading distinction, implied in all the rest, that
the two kinds of coal are never found in the same bed, but always in
different situations, and with different laws of stratification, is
expressly contradicted by matter of fact. Coal, as is said above, with
its ligneous texture quite apparent, and coal with no such structure
visible, are often found in the same seam, are brought up from the same
mine, and united in the same specimen. I have a specimen from a bed of
coal, in the Isle of Sky, found under a basaltic rock, consisting of a
ligneous part, which graduates into one in which there is no vestige
of a fibrous texture, and in which the surface is smooth and glossy,
with a fracture almost vitreous. The upper part of the specimen is
therefore perfect wood coal, and the under part perfect mineral-coal,
in the language of Mr Kirwan; at the same time that the transition from
the one to the other is made by insensible degrees. This specimen,
were it perfectly solitary, is sufficient to prove the identity
of the two species of coal we are now speaking of, and to show,
that the difference between them is accidental, not essential. The
specimen, however, is far from being solitary; the number of similar
appearances is so great, as hardly to have escaped the observation
of any mineralogist. Mr Kirwan admits, that wood coal is often found
under basaltes;[51] but what is essential to be remarked is, that, in
this instance, we have both the wood coal and the common mineral-coal,
lying under that rock, and the one passing gradually into the other It
appears, indeed, that many of the facts which Mr Kirwan produces, in
treating of what he calls _carboniferous_ soils, are quite inconsistent
with the distinction he would make between wood-coal and mineral
coal.[52]
[Footnote 51: Geol. Essays, p. 310.]
[Footnote 52: _Ibid._ p. 311.]
141. It is, however, true, that there are instances in which the wood
coal, or fossil wood, as it is usually called, forms entire beds, quite
unconnected with the ordinary coal, and stratified in some respects
differently. Such is the Bovey coal in Devonshire, the wood-coal in the
north of Ireland, and perhaps the Surturbrandt of Iceland. With respect
to the Bovey coal, it does by no means answer to one of Mr Kirwan's
remarks, viz. that late observations have ascertained, that no such
parallelism of the beds, as in mineral coal, nor even any distinct
number of strata is found. In the Bovey coal, the number of strata is
very well defined, by beds of clay regularly interposed; but as to the
extent of these beds, the coal having been worked only at one place,
and by an open pit, without any extensive subterraneous excavation,
nothing is known with certainty.
In the Bovey coal too, I must observe, though its beds have the
ligneous structure very distinct, the clay interposed between these
beds, which is but little indurated, contains a great deal of coaly
matter, in the form of thin flakes, interspersed through it. So far as
I know, there are no mineral reins nor shifts, nor any bed of indurated
stone, that accompany this coal; so that, though one can not doubt of
its vegetable origin, some doubt may be entertained concerning the
nature of the mineralizing operations, to which it has been subjected
The consideration of these, however, does not belong to the present
argument; and the peculiarities of this semi-mineralized coal, as it
may be called, have nothing to do with the general question, whether
wood coal and mineral coal are the same substance; about which
question, if the gradations are properly considered, I think, no
reasonable doubt can remain.
142. One of Mr Kirwan's objections to the vegetable origin of coal,
is founded on this fact, that there is, in the museum at Florence, a
cellular sandstone, the cells of which are filled with genuine mineral
coal. "Could this (adds he) have been originally wood?"[53] The answer
to the interrogatory proposed here as a _reductio ad absurdum_, is,
that most undoubtedly it may have been wood. Sandstone with charred
wood, that is, with wood coal in it, is not an uncommon phenomenon in
coal countries. I have seen a specimen of this kind from the Hales
Quarry, near Edinburgh, consisting of a piece of charred wood, imbedded
in sandstone; the wood was much altered, but the remains of its fibrous
structure were distinctly visible. This affords a perfect commentary on
the specimen in the Florence cabinet.
[Footnote 53: Geol. Essays, p. 321.]
143. If then it be granted, as I think it must, that the two kinds of
coal we have been speaking of are of the same origin, it is not very
necessary to enter on a refutation of Mr Kirwan's theory with respect
to either of them. His account of the formation of mineral coal,
however, is so singular, that it cannot be passed over without remark.
Mr Kirwan supposes, 1mo, That natural carbon was originally contained
in many mountains of the granite and porphyritic order, and also in
siliceous schistus; and might, by disintegration and decomposition, be
separated from the stony particles. 2do, That both petrol and carbon
are often contained in trap, since hornblende, which has lately been
found to contain carbon, very frequently enters into its composition.
"My opinion (adds he) is, that coal mines, or strata of coal, as well
as the mountains in which they are found, owe their origin to the
disintegration of primeval mountains, either now totally destroyed,
or whose height and bulk, in consequence of such disintegration, are
considerably lessened; and that these rocks, anciently destroyed,
contained most probably a far larger proportion of carbon and
petrol than those of the same denomination now contain, since their
disintegration took place at so early a period.[54]
[Footnote 54: Geol. Essays, p. 328, &c.]
"By the decomposition of these mountains, the feldspar and hornblende
were converted into clay; the bituminous particles, thus set free,
reunited, and were absorbed, partly by the argil, but chiefly by the
carbonaceous matter, with which they have the greatest affinity. The
carbonic and bituminous particles, thus united, being difficultly
miscible with water, and specifically heavier, sunk through the moist,
pulpy, incoherent argillaceous masses, and formed the lowest stratum,"
&c.
Such is Mr Kirwan's theory of the formation of coal, and nobody I think
will dispute the originality of it.
144. To enter on a formal refutation of an opinion so loaded with
objections, would be a task as irksome as unnecessary. A few
observations will suffice.
The notion of the great degradation of mountains, involved in this
hypothesis, is the part of it to which I am least disposed to object.
But I cannot help reminding Mr Kirwan, that the effects of waste are
not supposed less in this, than in Dr Hutton's theory; and that he has
assumed the very principle, of which that theory makes so much use,
though he has reserved to himself, as it should seem, the right of
denying it, when it does not accord with his system. It is indeed worth
while to compare what is said concerning the degradation of mountains,
in the above quotations, and still more fully in the book itself, with
what is advanced concerning their indestructibility, in another passage
of the same volume:[55]
[Footnote 55: Page 436.]
"All mountains are not subject to decay; for instance, scarce any of
those that consist of red granite. The stone of which the Runic rocks
are formed, have withstood decomposition for two thousand years, as
their characters evince," &c.
"Basaltic pillars, in general, bid defiance to decay," &c. He goes on
to deny every step of the degradation of land, by which it is wasted,
carried into the sea, and spread out over its bottom, though all these
are necessary _postulata_ in his theory of the formation of coal. One
can be at no loss about estimating the value of a system, in which such
gross inconsistencies make a necessary part.
145. The quantity of hornblende and siliceous schistus, necessary to
be decomposed, in order to produce the coal strata presently existing,
is enormous, and would lead to an estimate of what is worn away from
the primeval mountains, far exceeding any thing that Dr Hutton has
supposed. It is true, that Mr Kirwan, never at all embarrassed about
preserving a similitude between nature as she is now, and as she was
heretofore, lays it down, that the part of the primeval mountains
which is worn away, contained much more carbon than the part which is
left behind. This, however, is an arbitrary supposition; and since, in
this system, such suppositions are so easily admitted, why may we not
conceive, in the primeval mountains, a more copious source of carbonic
matter than hornblende or siliceous schistus? We have but to imagine,
that the _diamond_ existed among these mountains in such abundance, as
to constitute large rocks. This stone being made up of pure, or highly
concentrated carbon, the adamantine summits of a single ridge, by
their decomposition, might afford a carbonic basis, sufficient for the
coal beds of all the surrounding plains.
146. We may also object to Mr Kirwan, that the siliceous part of
the mountains has not been chemically dissolved; it has been only
abraded and worn away. Mechanical action has reduced the quartz to
gravel and sand, but has not produced on it any chemical change.
The carbon, therefore, could not be let loose. Experiment, indeed,
might be employed, to determine whether the siliceous matter of the
secondary, and of the primary strata contains this substance in the
same proportion.
Again, a more fatal symptom can hardly be imagined in any theory, than
that, when the circumstances of the phenomena to be explained are _a
little_ changed, the theory is under the necessity of changing _a
great deal_. Now, this is what happens to Mr Kirwan's theory, in the
attempt made to explain by it the stratum of coal described in the
_Annales de Chimie_,[56] as cutting a mountain of argillaceous strata
in two, at about three-fourths of its height. This stratum, Mr Kirwan
says, must have been formed by _transudation_ from the superior part
of the mountain,[57] Besides that this is a gratuitous supposition
of a thing, without example, it involves in it an absurdity, which
becomes evident the moment the question is asked, What occupied the
place of the coal-bed before the transudation from the upper part of
the mountain? Has the _liquid coal_, as it percolated through the upper
strata, expelled any substance from the place it now occupies? or has
it been powerful enough to raise up, or to float, as it were, the upper
part of the mountain?
[Footnote 56: Tom. xi. p. 272.]
[Footnote 57: Geol. Essays, p. 338.]
The situation of this bed of coal is not singular, and its formation
is easily explained on Dr Hutton's theory. It is part of a stratum of
coal, which has been deposited, like all others, at the bottom of the
sea; from whence certain causes, of very general operation, have raised
it up, together with the attending strata: these strata have since
been all cut down, and worn away by the operations of the surface; and
the mountain, with the coal stratum in the middle of it, is a part
of them which has been left behind. There is no wonder, that a coal
stratum should be found alternating with others, in a mountain, any
more than in the bowels of the earth, and no more need of a separate
explanation.[58]
[Footnote 58: This stratum of coal, which is described by HASSENFRATZ,
is remarkable for being in a mountain which rests immediately on
primary schistus and granite.]
147. After all, it may be asked, for what purpose is it that so
many incongruous and ill supported hypotheses are thus piled on one
another? is it only to avoid ascribing the carbonic and bituminous
matter of coal to a substance in which we know with certainty that such
matter resides in great abundance, in order to derive it from other
substances, in which a subtle analysis has shown, that it exists in a
very small proportion? Such reasoning is so great a trespass on every
principle of common sense, not to say of sound philosophy, that, to
bestow any time on the refutation of it, is, in some degree, to fall
under the same censure.
NOTE III. § 7.
_Primitive mountains._
148. The enumeration of the different kinds of primary schistus, at
§ 7, is not proposed as at all complete. It will be less defective,
however, if we add to it _talcose schistus_, and _lapis ollaris_ or
_potstone_.[59]
[Footnote 59: Kirwan's Mineralogy, vol. i. p. 155.]
149. The rocks called here by the name of primary, were first
distinguished, as forming the basis of all the great chains of
mountains, and as constituting a separate division of the mineral
kingdom, by J. G. LEHMAN, director of the Prussian mines. See his
work, intituled, _Essai d'une Histoire Naturelle des Couches de la
Terre_.[60] These rocks were regarded by Lehman as parts of the
original nucleus of the globe, which had undergone no alteration, but
remained now such as they were at first created; and, agreeably to
this supposition, he bestowed on them, and on the mountains composed
of them, the name of primitive. He remarks, nevertheless, their
distribution into beds, either perpendicular to the horizon, or highly
inclined, and the super-position of the secondary and horizontal
strata. However mineralogists may now differ in their theories from
Lehman, they must consider this distinction as a great step in the
science of geology, and very material to the right arrangement of the
natural history of the earth.
[Footnote 60: Tom. iii. p. 239, &c. The French translation is in 1759,
but the original preface is dated at Berlin, 1756.]
150. Several mineralogists have agreed with him in the supposition,
that these rocks are a part of the original structure of the globe, and
prior to all organized matter. Of this number is PALLAS;[61] and also
DE LUC, who applies the term _primordial_ to the rocks in question,
and considers them as neither stratified nor formed by water.[62]
In his subsequent writings, however, he admits their formation from
aqueous deposition, as the Neptunists do in general, but holds them to
be more ancient than organized bodies.
[Footnote 61: Observations sur la Formation des Montagnes.]
[Footnote 62: Lettres Phys. Sur l'Histoire de la Terre, tom. ii. p.
206.]
151. PINI, professor of natural history at Milan, has denied the
stratification of primitive mountains, in a memoir on the mineralogy
of St Gothard, and in another on the revolutions of the globe.[63]
His reasonings are opposed by SAUSSURE,[64] and are certainly, in
many respects, very open to attack. They proceed on a comparison
between the division of rocks, by what is called the planes of their
stratification, and their division by transverse fissures: two
things, which he thinks so much alike, that they ought not to be
referred to different causes; and, as the one cannot be regarded as
the effect of aqueous deposition, so neither should the other. This
is a very fallacious argument, because it confounds two things that
are essentially different; and, instead of inquiring about a matter
of fact, inquires about its cause. The truth is, that the dispute has
arisen from not distinguishing the granite from the schistus mountains,
and from involving both under the name of primitive. M. Pini seems
to be in the right, when he holds the granite of St Gothard to be
unstratified; but it is without any good reason, that he would extend
the same conclusion to the schistus of that mountain. CHARPENTIER, and
Saussure, in his last two volumes, contend even for the stratification
of granite.[65]
[Footnote 63: Memoria sulle Rivoluzioni del Globo Terrestre; Memorie
della Societa Italiana, tom. v. p. 222, &c.]
[Footnote 64: Voyages aux Alpes, tom. iv. § 1881.]
[Footnote 65: See NOTE XV. on Granite.]
As the consent, if not universal, is very general for the
stratification of the primary schistus, and the fact itself abundantly
obvious, in almost all the instances I have ever met with, I have not
considered it as necessary to enter here into any argument on this
subject.
NOTE IV. § 8.
_Primary strata not primitive._
152. An account of the facts referred to § 8, may be found in Hutton's
Theory, vol. i. p. 332, &c. To what is there said, of the shells
contained in the primary limestone of Cumberland, I must add, that
I have since had an opportunity of verifying the conjecture, that
the limestone rock, in which the shells were found, near the head of
_Coniston_ Lake, is part of the same body of strata, where shells were
found, in a quarry between Ambleside and Low-wood. The limestone of
that quarry contains several marine objects; it is in strata declining
about 10° from the perpendicular, toward the S. E., and forms a belt,
stretching across the country from N. E. to S. W.
In a quarry where the argillaceous schistus, on the south side of this
limestone belt, is worked for pavement, are impressions of what I think
may safely be accounted marine objects; they have the form of shells,
are much indurated, and full of pyrites. They seem to be of the same
kind with the impressions said to be found in a slate quarry, near the
village of Mat in Switzerland.[66]
[Footnote 66: Hutton's Theory, vol. i. p. 327.]
Another spot, affording instances of shells in primary limestone, is
in Devonshire. On the sea shore on the east side of Plymouth Dock,
opposite to Stonehouse, I found a specimen of schistose micaceous
limestone, containing a shell of the bivalve kind: it was struck
off from the solid rock, and cannot possibly be considered as an
adventitious fossil.
Now, no rocks can be more decided primary than those about Plymouth.
They consist of calcareous strata, in the form either of marble or
micaceous limestone, alternating with varieties of the same schistus,
which prevails through Cornwall to the west, and extends eastward into
Dartmoor, and on the sea-coast, as far as the Berry-head. These all
intersect the horizontal plane, in a line from east to west nearly;
they are very erect, those at Plymouth being elevated to the north.
Though, therefore, the remains of marine animals are not frequent among
the primary rocks, they are not excluded from them; and hence the
existence of shell-fish and zoophytes, is clearly proved to be anterior
to the formation even of those parts of the present land which are
justly accounted the most ancient.
153. The rocks which contain sand or gravel, which are of a granulated
texture, must also be considered as carrying in themselves a testimony
of the most unequivocal kind, of their being derived from the
_detritus_ and waste of former rocks. Now, the fact stated in the text,
concerning sand found in schistus, most justly accounted primary,
might be exemplified by actual reference to many spots on the earth's
surface. A few such will be sufficient in this place.
St Gothard is a central point, in one of the greatest tracts of primary
mountains on the face of the earth, yet arenaceous strata are found in
its vicinity. Between Ayrolo and the Hospice of St Gothard, Saussure
found a rock, composed of an arenaceous or granular paste, including in
it hornblende and garnets. He is somewhat unwilling to give the name
_gres_ to this stone, which M. Besson had done; but he nevertheless
describes it as having a granulated structure.[67]
[Footnote 67: Voyages aux Alpes, tom. iv. § 1822.]
Among the most indurated rocks that compose the mountains of this
island, many are arenaceous. Thus, on the western coast of Scotland,
the great body of high and rugged mountains on the shores of Arafaig,
&c. from Ardnamurchan to Glenelg, consists, in a great measure, of a
granitic sandstone, in vertical beds. This stone sometimes occupies
great tracts; at other times it is alternated with the micaceous, or
other varieties of primary schistus; it occurs, likewise, in several of
the islands, and is a fossil which we hardly find described or named
by the writers on mineralogy. Much, also, of a highly indurated,
but granulated quartz, is found in several places in Scotland, in
beds or strata, alternated with the common schistus of the mountains.
Remarkable instances of this may be seen on the north side of the ferry
of Balachulish, and again on the sea-shore at Cullen. At the latter,
the strata are remarkably regular, alternating with different species
of schistus. At the former, the quartz is so pure, that the stone has
been mistaken for marble.
These examples are perhaps sufficient; but I must add, that in the
micaceous and talcose schisti themselves, thin layers of sand are
often found, interposed between the layers of mica or talc. I have
a specimen, from the summit of one of the highest of the Grampian
mountains, where the thin plates, of a talcky or asbestine substance,
are separated by layers of a very fine quartzy sand, not much
consolidated.
The mountain from which it was brought, consists of vertical strata,
much intersected by quartz veins. It is impossible to doubt, in this
instance, that the thin plates of the one substance, and the small
grains of the other, were deposited together at the bottom of the sea,
and that they were alike produced from the degradation of rocks, more
ancient than any which now exist.
154. In the Neptunian system, as improved by WERNER, an attempt is made
to take off the force of such instances as are produced in § 8, 9, and
152, &c. by distinguishing rocks, as to their formation, into three
different orders, the primitive, the intermediate, and the secondary,
or, to speak more properly, into primary, secondary, and tertiary. The
same mineralogist distinguishes, among the materials of these rocks,
between what he terms chemical and mechanical deposits. By mechanical
deposits, are understood sand, gravel, and whatever bears the mark of
fracture and attrition; by chemical deposits, those which are regularly
crystallized, or which have a tendency to crystallization, and in which
the action of mechanical causes cannot be traced. This distinction
is founded in nature, and proceeds on real and palpable differences;
but the application made of it to the three kinds of strata just
enumerated, seems by no means entitled to the same praise.
The primitive rocks contain, it is said, none but chemical deposits,
and are entirely composed of them: the intermediate contain a mixture
of both, and also some vestiges of organized bodies: the secondary
consist almost entirely of the mechanical, or of the remains of such
bodies, with little of the chemical. The first of these, then, are held
to contain no mark or vestige whatsoever of any thing more ancient
than themselves, and are, in the strictest sense, primeval, or formed
of the first materials, deposited by the immense ocean which originally
encompassed the globe.
After them were formed the intermediate, mostly consisting of chemical
deposits, but containing also some animal remains, and some spoils from
the land, subjected to the various kinds of destruction, which even
then made a part of the order of nature. These rocks, it is alleged,
are chiefly argillaceous, are less indurated than the primary, and not
intersected by veins of quartz.
The secondary were formed from the remains of the other two, and
contain more mechanical deposits than any other.
This sketch of what I understand to be Werner's opinion concerning the
different formation of the strata, is chiefly taken from a view of his
system, in the _Journal de Physique_ for 1800.
155. The main objection to the distinction here made between the
primary and the intermediate strata, is founded on the facts that
have been just stated. The sandstone of St Gothard is from a country
having every character of a primary one in the highest perfection. The
instances I have mentioned from the Highlands of Scotland, are from
mountains, less elevated indeed than the Alps, but where the rock is
micaceous, talcose, or siliceous, in planes erect to the horizon, and
intersected by veins' of quartz. The shells from Plymouth are from a
rock, that Werner would, I think, admit to be truly primitive. Those
from the lakes, also, are from the centre of a country, occupied by
porphyry, schorl, hornstone-schistus, and many others, about the order
of which there can be no dispute. It is true, that in this tract
there are argillaceous strata, of the kind that might be accounted
intermediate, were they not interposed among those that are certainly
primary; and this very intermixture shows, how little foundation there
is for the distinction attempted to be made between the formation of
the one and of the other. If there is any principle in mineralogy,
which may be considered as perfectly ascertained, it is, that rocks
similarly stratified, and alternated with one another, are of the same
formation.
Hence we conclude, that there is _no order of strata yet known_, that
does not contain proofs of the existence of more ancient strata. We see
nothing, in the strict sense, primitive. It must be understood, that
what is here said has no reference to granite, which I do not consider
as a stratified rock, and in which neither the remains of organized
bodies, nor sand, have I believe been ever found; though some
instances will be hereafter mentioned, where granite contains fragments
of other stone, viz. of different kinds of primary schistus.
To the instances of sand involved in primary schistus, I might have
added many from the rocks of that order on the coast of Berwickshire,
of which mention is so often made in these Illustrations; but I wished
to draw the evidence from those rocks that are most unequivocally
primary, and to which the Wernerian distinction of _intermediate_ could
not possibly be applied.
If any one assert, as M. De Luc has done, that sand is a chemical
deposit, a certain mode of crystallization which quartz sometimes
assumes, let him draw the line which separates sand from gravel; and
let him explain why quartz, in the form of sand, is not found in
mineral veins, in granite, nor in basaltes, that is, in none of the
situations where the appearances of crystallization are most general
and best ascertained.
NOTE V. § 10.
_Transportation of the
materials of the strata._
156. The great transportation or _travelling_ of the materials of the
strata, supposed by Dr Hutton, has been treated as absurd by some
of his opponents, particularly De Luc and Kirwan. These philosophers
seem not to have observed, that their own system, and indeed every
system which derives the secondary strata from the primary, involves
a transportation of materials, hardly less than is supposed in the
Huttonian theory, and a degradation of the primeval mountains, in
many instances much greater. To form some notion of this degradation,
it must be recollected, that the primeval mountains, which furnished
the materials of the secondary strata in the plains, cannot have
stood in the place now occupied by these plains. This is obvious; and
therefore we must necessarily regard the secondary strata as derived
from the primitive mountains which are the nearest to them, and of
which a part still remains. This part is sufficient to define the
base of the original mountains; and the quantity of the secondary
strata which surround them may help us to make some estimate of their
height. Let us take, for instance, the extensive tract of secondary
country about Newcastle, where coal mines have been sunk through a
succession of secondary strata, to the depth of more than a thousand
feet. This secondary country may be considered as comprehending almost
the whole of the counties of Northumberland and Durham, and probably
as extending very far under the part of the German Ocean which washes
their coasts; and the whole strata composing it must be derived, on
the hypothesis we are now considering, from the Cheviot Hills, on one
side, and from those in the high parts of Westmoreland and Cumberland
on the other, comprehending the Alston-Moor Hills, and the large group
of primary mountains, so well known from the sublime and romantic
scenery of the _Lakes_. Now, the mountains which stood on this base,
had not only to supply the materials for the tract already mentioned,
on the east, but had also their contingent to furnish to the plains on
the west and north; the Cheviots to Roxburghshire and Berwickshire;
the Northumberland mountains to the coal strata about Whitehaven, and
along the sea coast to Lancashire. On the whole, we shall not exceed
the truth, if we suppose, that the secondary strata, at the feet of the
above mountains, are six or seven times more extensive than the base
of the mountainous tract. If then we take the medium depth of these
secondary strata to be one thousand feet, it is evident, that the mass
of stone which composes them, if it were placed on the same base with
the primitive mountains, would reach to the height of six thousand
feet. This is supposing the mass to preserve the breadth of its base
uniformly to the summit; but if it be supposed to taper, as mountains
usually do, we must multiply this six thousand by three, in order to
have the height of these primeval mountains, which, therefore, were
originally elevated not less than eighteen thousand feet; in height,
therefore, they once rivalled the Cordilleras, and are now but poorly
represented by the hills of Skidaw and Helvellyn. It were easy to show,
that this estimate is still below the result that strictly follows from
the Neptunian hypothesis; but it is unnecessary to proceed further,
than to prove, that the principle of the degradation of mountains, is
involved in that hypothesis to an excessive and improbable degree; and
that the supporters of it, have either been guilty of the inconsistency
of refusing to Dr Hutton the moderate use of a principle, which they
themselves employ in its utmost extent, or of not having sufficiently
adverted to the consequences of their own system.
157. The formation of secondary strata from the degradation of the
contiguous mountains, on close examination, is subject to many
other difficulties of the same kind. Mountains of secondary strata,
and nearly horizontal, are found in this island of the height of
three thousand feet. Such are Ingleborough, Wharnside, and perhaps
some others on the west of Yorkshire. The whole chain, indeed,
for secondary mountains, is of great elevation. The strata are of
limestone, and of a very coarse-grained sandstone, alternating with it.
No mountains can more clearly point out, that the strata of which they
consist were once continued quite across the vallies which now separate
them; and hence, if the materials of those strata were indeed furnished
from any contiguous primitive mountains, the latter must have been, out
of all proportion, higher than any mountains now in Britain.
158. Thus, a great degradation of the primitive mountains, and of
course a great travelling of their materials, is proved to make a
necessary part of the Neptunian theory. The extent of this travelling
or transportation may be rendered more evident, if we apply a similar
mode of reasoning to larger portions of the globe. The north-west of
Europe furnishes us an instance of a very extensive tract of secondary
country, comprehending the greater part of Britain, the whole of
Flanders and Holland, part of Germany, the northern provinces of
France, and probably the bed of the German Ocean, at least for a great
extent. Within this circle almost all is secondary, and on the sides
of it all round are placed ridges or groups of primitive mountains,
namely the mountains of Auvergne, at least in part, and going round by
the east, the Alps, the Vosges, the Hartz, the Highlands and Western
Islands of Scotland, the hilly countries of Cumberland, Wales, and
Cornwall. This zone of primitive mountains, on the supposition of the
Neptunists, must have risen up in the form of islands in the great
ocean, that originally covered the earth, forming a kind of circular
Archipelago, including in its bosom a sea, which was from seven to
five hundred miles in diameter. Over the whole of this extent, the
_detritus_ of the above mountains must have been carried, in order to
form the flat interjacent countries which are now exposed to our view.
Such then, even on their own supposition, is the extent to which the
Neptunists must admit that the materials of the primeval mountains were
transported by the ocean.
159. This transportation of materials, may not be so great as that
which is involved in Dr Hutton's theory, but is such as should make the
enemies of his system consider, how nearly the principles they _must_
introduce, agree with those that they _would_ reject. This is one
fact, out of many, which shows, that there is at present a much nearer
agreement between the systems of geology, than between their authors.
160. To these facts, demonstrating the great transportation of fossils
in some former conditions of the globe, we may add another, recognised
by all mineralogists. The animal exuviæ contained in limestone and
marble, are often known to belong to seas, extremely remote from the
countries where they are now found. In the chalk-beds of England, in
the limestones of France, a great proportion of the petrifactions
belong to the tropical seas, and appear to have been brought from the
vicinity of the equator. Buffon observes, that of the fossil shells
found in France, it has been disputed, whether the foreign are not
more numerous than the native; and, though he is himself of opinion
that they are not, it is evident that they must bear a considerable
proportion to the whole.[68] In the petrifactions of Monte Bolca, near
Verona, where the impressions of fish are preserved between the laminæ
of a calcareous schistus, one hundred and five different species have
been enumerated, of which thirty-nine are from the Asiatic seas, three
from the African, eighteen from those of South, and eleven from those
of North America.[69] Similar observations have been made on the marine
plants, and the impressions of vegetables, found in rocks, in different
parts of Europe. At St Chaumont, near Lyons, is found an argillaceous
schistus, covering a bed of coal, every lamina of which is marked with
the impressions of the stem, leaf, or other part of some plant; and it
happens, says M. FONTENELLE, by an unaccountable destination of nature,
that not one of these plants is a native of France. They are all ferns
of different species, peculiar to the East Indies, or the warmer
climates of America. Here also was found the fruit of a tree, which
grows only on the coasts of Malabar and Coromandel.[70]
[Footnote 68: Buffon, Théorie de la Terre, art. 8.]
[Footnote 69: Saussure, Voyages aux Alpes, tom. iii. § 1535.]
[Footnote 70: Mém. De l'Acad. Des Sciences, 1718, p. 3 and 287; and
1721, p. 89, &c.]
The same holds of the bodies of amphibious animals which now make a
part of the fossil kingdom. The head and the bones of crocodiles have
been found in the island of Shepey, at the mouth of the Thames; and the
remains of an animal of the same species, but of a variety now peculiar
to the Ganges, have been discovered in the alum rocks on the coast of
Yorkshire.[71] These proofs of the transportation of materials by the
sea, have the advantage of involving nothing hypothetical, and of being
equally addressed to the geologists of every persuasion.
[Footnote 71: Phil. Trans. vol. l. p. 688. CAMPER denies that the
remains here mentioned belong to the crocodile, or any amphibious
animal, and refers them to the balænaæ. He passes the same judgment on
those fossil bones from St Peter's Mount, near Maestricht, which have
been supposed to belong to the crocodile; he looks on them as belonging
to whales, though of an unknown species. In this Mount, so famous for
its petrifactions, he finds many specimens of bones, which he thinks
belong to the turtle. Phil. Trans. vol lxxvi. p. 443. The opinion of an
author, so well skilled in comparative anatomy, must be regarded as of
great weight: if it takes from our argument in one part, it adds to it
in another, and the acquisition of the turtle makes up abundantly for
the loss of the crocodile.]
On this subject I cannot help observing, that the accurate comparison
of the animal exuviæ of the mineral kingdom, with their living
archetypes, is not merely a curious inquiry, but is one that may lead
to important consequences, concerning the nature and direction of the
forces which have changed, and are continually changing, the surface of
the earth.
161. These remarks I have thought it proper to add to the proofs of the
composition of the present from former strata, in order to show, that
the great transportation of materials involved in that supposition, is
not only conformable to the hypothesis of the Neptunists concerning
the secondary strata, but is also proved by the most direct evidence,
independently of all hypothesis. All this reasoning regards the ancient
state of the globe. Whether such a travelling of stony bodies makes
a part of the system now actually carrying on, will be considered in
another place.[72]
[Footnote 72: See NOTE XIX.]
NOTE VI. § 13.
_Mr Kirwan's notion of precipitation._
162. The Neptunist who has provided the means of dissolving the
materials of the strata, has only performed half his work, and must
find it a task of equal difficulty to force this powerful menstruum
to part with its solution. Mr Kirwan, aware in some degree of this
difficulty, has attempted to obviate it in a very singular way. First,
he ascribes the solution of all substances in water, or in what he
calls the chaotic fluid, to their being finely pulverised, or created
in a state of the most minute division. Next, as to the deposition, the
solvent being, as he acknowledges, very insufficient in quantity, the
precipitation took place, (he says,) on that account the more rapidly.
If he means by this to say, that a precipitation without solution
would take place the sooner the more inadequate the menstruum was to
dissolve the whole, the proposition may be true; but will be of no
use to explain the crystallization of minerals, (the very object he
has in view,) because to crystallization, it is not a bare subsidence
of particles suspended in a fluid, but it is a passage from chemical
solution to non-solution, or insolubility, that is required.
If, on the other hand, he means to say, that the solution actually took
place more quickly, and was more immediately followed by precipitation,
because the quantity of the menstruum was insufficient, this is to
assert, that the weaker the cause, the more instantaneous will be its
effect.
Of two propositions the one of which is nugatory, and the other absurd,
it is not material to inquire which the author had in view.
NOTE VII. § 16.
_Compression in the mineral regions._
163. It is worthy of remark, that the effects ascribed to compression
in the Huttonian Theory, very much resemble those which Sir ISAAC
NEWTON supposes to be produced in the sun and the fixed stars by
that same cause. "Are not," says he, "the sun and fixed stars great
earths, vehemently hot, whose heat is conserved by the greatness of
the bodies, and the mutual action and reaction between them, and the
light which they emit; and _whose parts are kept from fuming away,
not only by their fixity, but also by the vast weight and density of
the atmospheres incumbent upon them, and very strongly compressing
them_."[73]
[Footnote 73: Newton's Optics, Query 11.]
164. The fact of water boiling at a lower temperature under a less
compression, is sufficient to justify the supposition, that bodies may
be made by pressure to endure extreme heat, without the dissipation
of their parts, that is, without evaporation or combustion. A further
_postulatum_ is introduced in Dr Hutton's theory, namely, that compound
bodies, such as carbonate of lime, when the compression prevents their
separation, may admit of fusion, notwithstanding that the fixed part
may be infusible when separated from the volatile. This assumption is
supported by the analogical fact of the fusion of the carbonate of
barytes, as mentioned in the text.