HOW CHALK IS MADE
“Peace, moaning Sea, what tale have you to tell,
What mystic tidings, all unknown before?
Whether you break and thunder on the shore,
Or whisper like the voice within the shell,
O moaning Sea, I know your burden well!”
LEWIS MORRIS.
“The tiny cell is forlorn,
Void of the little living will.”--TENNYSON.
One of the tasks carried on in Ocean waters is Chalk-Building.
The “White Cliffs of Albion” and those also of Gaul are vast masses of
chalk, containing layers of flint, and mixed with many other materials,
but chiefly composed of the crumbling white substance, which is
familiar to all who live near the North and South Downs.
This formation stretches a long way. The heights of Salisbury are of
chalk. The Chiltern Hills are of chalk. The Yorkshire Wolds are of
chalk. It is found in Norfolk; it is found in Kent; it is found in
Surrey; it is found in Sussex. There are chalk-beds in France, in
Germany, in other parts of Europe--not to speak of Asia--which, with
those of Great Britain, extend through many hundreds of miles.
And wherever these masses of chalk are found, there we know that, once
upon a time, the land lay under ocean-waves.
For Chalk, like Sandstone, was not formed on dry land. It could not be
formed on dry land. It was built--it could only be built--under the
sea, to be in later ages uplifted as dry land.
During those far-back days, when the chalk-beds of Europe were being
made, a different state of things prevailed from that of the present.
By far the greater part of Europe must have lain under water, from
which the summits of the Alps, the Pyrenees, and other mountains
emerged as groups of islands. Great Britain must have been chiefly or
entirely hidden.
So far I have spoken of sandstone and chalk together. But a marked
distinction--a _vital_ distinction--exists between the two.
In the mode of their building they may be alike. In the materials of
which they are built they are utterly different.
If a lump of chalk is examined by the chemist, its principal substance
is found to be Carbonate of Lime.
Now there is something very remarkable about Carbonate of Lime. It is
absolutely different from the materials of which sandstone and granite
are made. Wherever we stumble upon carbonate-of-lime, there we are on
the track of LIFE. And the moment that we touch upon LIFE, even in its
simplest and lowest forms, we rise to a higher level.
Hitherto, in this subject of the Mighty Deep, we have had to do
with things inanimate; things without consciousness; things blindly
controlled by the forces of nature. In the story of ocean-waters, of
ocean-salt, of ocean-rivers, of icebergs and ice-floes, Life has no
part. There is no life in a grain of sand, no life in a granite rock.
But here, suddenly, we are arrested. Here, in the composition of Chalk,
we come across a difference. Here, at one step, we pass over a vast
dividing chasm, and stand face to face with that which has Life.
Not indeed that which lives now, but with that which did live, the
signs of which may better help us to understand Life in the present.
Is this so new? Have we not already in former chapters found tokens of
creatures which once existed, of fossil remains embedded in rock?
Yes; but that was not the same. Fossil remains are discovered in many
kinds of stratified rock. Here we are not concerned with separate
remains, buried in masses of chalk, but with the actual substance
of chalk itself. The mere building of it, as earlier told, closely
resembles the building of sandstone. Chalk, like sandstone, was formed
in past ages out of tiny particles, carried by ocean-waves, dropped
upon ocean’s bed, slowly consolidated, then gradually upheaved.
Particles of----
Ah, there we reach the great distinction!
Not particles of inanimate mineral substances, such as grains of
quartz. No; but particles which once formed the habitation of living
creatures. More than this--particles which once shared in the Life of
the beings with which for the time they were in touch. Infinitesimal
specks, often so minute as to appear only as fine dust to man’s unaided
sight; yet real organic remains, each one of which has been the home of
an active animal.
A lump of chalk is a mass of densely packed tiny fossil shells, more
or less crushed and broken. It has been reckoned that a cubic inch of
chalk probably holds at least one million shells.
Try to imagine what this means. The work of the Ocean in building solid
sandstone, from unnumbered myriads of myriads of grains of sand, is
marvellous enough. But here we have something far more wonderful.
Here we have rocks and cliffs, ranges of hills and extents of country,
to a great degree composed of almost invisible sea-shells, so small, so
numerous, that a million or more of them may be packed into one little
cubic inch of space, while the chalk-beds lie through hundreds of miles.
Think of continuous piles of these shells, many hundreds of feet in
thickness, all built out of the dead shells of dying millions of tiny
creatures. Deep, deep below the surface, where waves had no power,
where currents were sluggish, fell a ceaseless gentle rain of these
minute shells. Life had fled from each jelly inhabitant; its brief day
was over; and the empty shell went quietly down, whether from near the
surface or from lower depths, till it reached the ocean-bed. There it
lay, forming part of a gathering sticky ooze or mud, which in later
times should be slowly hardened into chalk.
But the greater wonder has yet to be told about these shells--these
tiny highly-finished constructions.
Not only did a speck of living jelly once inhabit each shell. That
speck of living jelly actually MADE the shell.
Not deliberately. Not with intention. Not even consciously. The
“making” is in no sense to be confounded with voluntary effort, with
the labour which means exertion and fatigue. It was as instinctive, as
involuntary, as the “making” of bones in your body and mine.
“But we do not make our bones,” somebody may protest, with a touch of
indignation.
Undoubtedly, in a sense, we do. The jelly-speck does not more surely
“secrete” its shell, than a man “secretes” his skeleton. Personal will
has not to do with the task in either case, beyond the taking in of
necessary food; and neither man nor jelly-speck may claim any credit on
the score of the pattern worked out.
We have all seen a garden-snail, carrying lightly upon its back
its shell or “house,” or outside skeleton. That shell is formed
of carbonate-of-lime. In the snail’s slimy body exists a small
manufactory for producing or “secreting” carbonate-of-lime. The
materials are obtained by the snail through its food. The deposits
of it--made as the snail’s nature, certainly not the snail’s
reason--dictates, grow into a sheltering framework for its protection.
In a Dictionary we may find the strict meaning of this word “secrete.”
It is given as--“to hide; to conceal; to deposit in some secret or
private place; to separate from the blood in animals, or from the sap
in vegetables, and elaborate into a new product.”
One cannot deny that the word, though used for all such “elaborations,”
is more appropriate in the case of a man’s hidden and private framework
of bones, than in a snail’s or jelly-creature’s outside shell.
That which the garden-snail so deftly does, is done also by countless
billions of minute jelly-specks in the ocean; though with the latter
the mechanism is far simpler, because the animal belongs to a far lower
and more primitive type.
Still, simple though the apparatus may be, the tiniest of these
jelly-specks has power to separate lime from ocean-waters, to unite it
with carbonic acid in its own frame, to form carbonate-of-lime from
the two, and to build of the manufactured carbonate-of-lime a shell for
its own use.
Thenceforward, for a little space, the jelly-speck lives in that shell,
and feeds in that shell, and then it dies in that shell. When it exists
no longer, down sinks the lifeless skeleton, to serve a new purpose at
the bottom of the sea.
No mere shapeless lumps are these shells, flung together without care
or plan. Each one, however infinitesimal in size, is a delicate and
elaborate construction; each one shows the carrying out of a definite
and beautiful plan. A different design serves for each species and kind
of jelly-speck--not for each individual.
Such Design we must ascribe to a Mind lying beyond that which we see;
not to the jelly-speck itself, which acts as an unconscious architect,
working automatically, as you and I work in the early growth and later
renewal of our bony frameworks, the “secreting” of our skeletons.
No chance tossing together of particles of carbonate-of-lime could
result in the exquisite forms, the intricate patterns, of these little
shells; still less, in such patterns being faithfully reproduced by
millions of living jelly-specks, each according to its own class or
variety.
For all this the present tense is as true as the past tense.
Those white cliffs along the coast were formed ages ago. But the ocean
is working still, building still, piling grains of sand together still,
heaping specks of mud together still, and laying shells, shells,
shells, together still, in amounts beyond all reckoning.
Chalk-building went on in ages past; it goes on now; and doubtless it
will go on in centuries to come.
Not only beyond reckoning, but beyond imagination, are the enormous
multitudes of these creatures, which live and die in the ocean, forming
their shells, and adding their skeletons to the ever-growing pile below.
Over a large part of the Atlantic bed, as over other Ocean-beds too,
lies a thick ooze. When this was first brought to the surface, in
soundings that were made before the laying of the earliest Atlantic
cable, it was supposed to mean a thin deposit of no particular
importance.
Then a deep-sea dredge, plunged into the ooze, carried away half-a-ton
of it, and men began to realise what its presence might mean. By a long
succession of soundings, its true nature became slowly manifest.
The ooze was found to be composed chiefly of tiny rounded shells,
called “Globigerina,” which belong to a larger class, known as
“Foraminifera.” And the white chalk of our British cliffs is made
principally of Foraminifera shells.
This last name springs from two Latin words, meaning “I bear a hole.”
The Foraminifera shells bear many holes. Each is in shape a tiny
collection of rounded compartments, usually not more than sixteen in
number; and each compartment has numerous minute holes in its walls.
Its inhabitant, a speck of jelly, is one of the least of living
creatures, belonging to the great Division of “Protozoa,” or “First
Animals.” None rank below them, for they are on the first or lowest
rung in the ladder of life.
A jelly-speck has no head, no limbs, no stomach, not even a mouth. It
can take in food at any part of its soft body. When it wishes--and
apparently even a jelly-speck can _wish_, which at once separates it
from inanimate materials--it makes a temporary tentacle or “foot,” by
pushing out a slender filament of its own substance through one of the
tiny holes in its shell. Whence the name “Rhizopod.”
Not all the Foraminifera specks live in the same kind of sheltering
skeletons. Some construct delicate domes or many-chambered discs of
sand-grains, joined together with enough carbonate-of-lime to act as
building-cement. Such skeletons are called “tests,” to distinguish them
from “shells” proper.
Hardly anything can be more remarkable than the way in which these
tests are put together by mere specks of jelly, alive indeed, but
without parts, without development, without understanding. How and why
they should choose from one place, each the especial materials which go
to form its own kind of “test,” is one of the mysteries in Nature for
which Science has no explanation. We can but look and marvel.
One kind of jelly-speck will use the larger grains of quartz, arranging
them, and joining them into a bottle-shaped test or shelter.
Another, in the same spot, belonging to a different species, will
select tinier grains of the same substance, and will build out of them
a rounded sphere, exquisitely modelled, with tiny holes at intervals
for the protruding “limbs.”
Another, of yet a different species, picks out the minutest of
sand-grains and of bits of sponge-spicules, and knits them together,
without any cement, into delicate white globes, “like homœopathic
globules,” giving to each a single opening.
And still another, of again a different species, forms a test of divers
compartments, with a tiny doorway leading from each into the next.
Behind all these extraordinary constructions lies a MIND. But--_not_
the mind of the jelly-speck!
Soft oozes, formed chiefly of Foraminifera and other shells, varying
in size from a pin’s head to almost invisible specks--though some few
kinds are larger--cover immense reaches of the ocean-bed, extending, it
is said, over fifty millions of square miles.
Yet they are not found everywhere below the sea. Near to Continents,
if they exist they are lost sight of amid the masses of sand and mud
carried down from the land. And in the profounder abysses of the ocean
they are lacking.
This last fact was long a puzzle. If the waters above were swarming
with live Foraminifera, the dead shells of which must be ever pouring
in a quiet rain to the ocean-bed, why should not the same ooze be found
there, as elsewhere?
That the waters above, at least in all warmer climates, do swarm thus,
is certain. Towards north and south, in colder seas, they rapidly
lessen; but in tropical regions, and in warm ocean-streams their
numbers are legion. Yet, from depths beyond about two miles, the ooze
was not brought up.
One explanation can be given; and it is that of the strong dissolving
power of sea-water. After a depth of about two miles, the delicate
little shells fail to resist that power. Once at the bottom, they might
be covered up and preserved; but they cease to exist _en route_ thither.
So in this as in many other instances, we see opposite forces at
work. The one force is perpetually undoing what the other force is
perpetually doing. Innumerable multitudes of living creatures are at
work, taking lime from the water, and constructing carbonate-of-lime.
But the ocean is ever seeking to re-dissolve that carbonate-of-lime.
Another difficult question as to the ooze was--whether the shells of
which it is mainly made were those of Foraminifera living in the deep
sea, far down below the surface, or of Foraminifera living near the
surface. Able men took both sides of the discussion, some ascribing the
ooze entirely to deep-sea jelly-specks, others ascribing it entirely to
surface jelly-specks.
The question cannot be said yet to have met with complete settlement.
But here once more it seems that both sides have been partly in the
right.
There are Foraminifera which live only at great depths, and there are
Foraminifera which live only near the surface. The ooze is found to
consist of shells belonging to both kinds, though it may be that the
surface species carry away the palm in point of greater multitudes.