the island appears to be flat, and to have but little elevation, while
Greenland and the great tracts of the northern regions beyond, deserve
more the name of glaciers, being almost entirely a mass of barren rocks
and snow.
The water-courses of these various great tracts of land are all
determined by the formation of the surface, but the amount of water
which is carried into the oceans by the rivers of any district is
always in proportion to the amount of vegetation in that district; thus
in Europe, Asia, and America, the number and extent of these correspond
with the great fertility of the soil, while the northern and western
part of Africa--the Great Desert--give off scarcely any of adequate
extent, the Nile appearing to receive its supply from the central parts
further south. The reason of it is this: wherever there is vegetation,
either in the form of grassy prairies or forests, there is also a great
reduction of temperature from the radiation and evaporation, and the
consequent formation of rain, dew, or snow, which falling on the ground
produces streams, &c.
Excepting the great tracts of land named, and islands too numerous to
be mentioned, the whole surface of the earth is covered with water,
the great divisions of which (called Oceans) are, the Arctic Ocean, to
the north of Europe, the Atlantic, between America, Europe, and Africa,
the Pacific between Asia and America, and the Indian Ocean between
Africa and Australia.
The foregoing is a very bare outline of the land and water covering the
surface; it may suffice, however, to call to mind the main features
of the earth as it is now disposed. There can be little doubt that
the great variety of climate, whether hot or cold, moist or dry, is
one of the greatest sources of happiness that can be well imagined;
it stimulates to research, travel, and inquiry into the works of God;
every change experienced tends to make man search for further change,
every new scene makes him compare it with others; and the acquirement
of a knowledge of places, and a general idea of the whole world,
expands his mind enables him to appreciate the good gifts he has
received, and affords a source of satisfaction beyond almost any other
kind of enjoyment.
THE WATERS.
[Illustration: SEA-COAST.]
How grand is the ever-moving ocean! how majestic its voice, how
terrible its anger! how beautiful every colour that is reflected from
its dancing spray, and how balmy the air which is wafted from its bosom
to refresh the heated earth, which, under the glare of a summer's
sun, seems parched with thirst. How refreshing to the senses is the
change from the dry heated grass on a midsummer day--from the dusty
roads--from the smoke begrimed town, smelling of dirt, and heated
by the reflection of the sun's rays from bricks and stones till it
becomes a furnace--from the close dark habitations of the city--from
the rattle, excitement, and continual noise of vehicles and human
voices--from the corroding cares and depressing influences attending
the fierce "battle of life"--to the cool and gentle breeze, "the wide
o'er-arching canopy of heaven," the murmur and ripple of the sea, to
the clear and exhilarating air, free from soot and laden with the odour
of the ocean--Oh what a desirable change! all human nature seems to
own it, and hasten to the shores of the great watery world, that they
may contemplate one of the greatest and grandest of God's works with
admiration and thankfulness, and be re-animated by its health-giving
powers.
It is a wonderful sight, and one which fills our minds with reflection;
here we see many of the laws of nature exemplified on a great scale.
The laws of gravity keep the surface of the ocean perfectly spherical
as a whole, while those of equilibrium keep it in constant and
ever-varying motion, the laws of attraction produce the tides, and
those of reflection and refraction cause its surface to assume all
sorts of colours and tints.
"Great art thou, Ocean, and unknown
The creatures springing into life from thee,
Earth's farthest shores full proudly thou dost own,
The cradle of thy wave from iced to torrid zone."
The ocean is full of life, both vegetative and animal; myriads of
both classes have their natural habitation in the sea, and the shore
is often, after a gale, strewed with curiosities well worth the
contemplation of those who devote their minds to thought. How many
varieties of sea-weed have you gathered? perhaps twenty; not three of
them are sea-weed at all! they are living animals, either zoophytes or
molluscs, every branch of that "_flustra_" contains a thousand living
beings, every spray of "_sertularia_" as many more, that other piece
is the "_bugula neretina_" and also owns a colony of animals: the next
is indeed a member of the vegetable kingdom, its beautiful crimson
colour makes it a conspicuous object, and there are many specimens of
the same plant, but of all shades of red, crimson, and purple, it
is the "_plocamium coccineum_." And thus it is with every object we
view, a knowledge of it brings us to respect and admire it more and
more as that knowledge increases, and none more so than some of the
productions of the sea. It is here we find specimens of the star-fish,
the sea-urchin, and other radiata. Shells of all kinds--both living and
dead--belonging to the various tribes of mollusca; crabs, shrimps, and
other crustaceans, besides the endless varieties of pebbles and other
specimens of worn-down rock, the effects of constant attrition.
If we turn from the shore and gaze upon the horizon, what a marvellous
object it is--ever receding as we recede, ever rising as we rise, and
never nearer nor farther away. This rising of the horizon, so as to be
always opposite to our eyes, is because the higher we are up the more
we see. On looking at the horizon we do not look on a perfect level,
(if we did, being above it, of course we could not see it at all)
but the depression of the line of vision is so slight as to be quite
unable to be appreciated; yet, small as it is, it enables us to see a
considerable space of the ocean, and the higher we rise--at the same
angle--the more we see. The edge of the horizon also appears curved,
being higher in front of us than on either side. This is only so in
appearance, for if any one were to place a piece of string (stretched
tightly between the hands) before his eyes, and bring it up till it is
on a level with the horizon, he would soon see that the string and the
horizon were both perfectly straight and exactly corresponding with
each other.
From the horizon we turn round and look at the chalk cliffs, those
white walls from which our native isle has received the name of
"Albion." How were they produced? by the constant lashing of the
restless waters, which are constantly wearing them away; but they are
beautiful objects, full of marvels and records of bygone ages, when
their tops were at the bottom of the deep seas.
The sea is a general name given to all the greater collections of water
throughout the world, although, in a restricted sense, it is applied
to those tracts of water of a secondary size, as the Black Sea, the
Baltic, and the Mediterranean, the term "ocean" being applied to the
larger tracts of water, as the Atlantic Ocean, the Pacific Ocean, &c.
All the great oceans and seas unite, and, in reality, form one great
world of waters, spread out and covering all the lower parts of the
earth, the term "lake" being applied to collections of water surrounded
by land, although the Caspian Sea retains the name of sea, and some of
the great lakes of America may well deserve such a name.
The waters of the sea fill up all the lower parts of the earth, so
that, almost without exception, the land is higher than the water, and
as the land in some places rises but a few feet, and in others as many
thousands, so, beneath the sea, the land sinks in many places but a few
feet, and in others perhaps as many thousands as it is known to rise
above it. The sea always maintains the same general level, although in
past ages the land has risen and fallen, sometimes in one place and
sometimes in another; indeed, the same process is taking place every
day, but in so slow a manner that centuries are required to make any
great alteration; while some tracts of land are being encroached on
by the action of the waves, others are being added to and elevated by
accumulations of mud and sand, or raised by the action of earthquakes
and volcanoes, which throw up under the sea, as well as on the land,
vast quantities of melted earth or lava, forming strata known to
geologists as basalt, tufa, &c., or eject showers of ashes and dust in
such prodigious quantities as to cover many hundred square miles of the
earth's surface. It was by one of these showers of ashes from Vesuvius
that the cities of Herculaneum and Pompeii were buried. So that, as a
whole, although the sea is continually altering slowly its position,
yet it pretty equally maintains the same elevation. At first thought it
may be supposed that the rivers constantly flowing into the sea would
alter its level, for some are so large that millions of tons of water
are brought by them into the sea every hour, and there are thousands
of rivers and rills which, night and day, pour in their tribute of
waters; but God has wisely and kindly arranged these things (like all
others) so that they shall afford us innumerable comforts, and yet
not raise up the sea so that it shall cover the land, for it requires
but a moment's consideration to be convinced that all this water which
flows into the sea must first have been abstracted from it, and it is
in this way--when the winds blow over the sea, they absorb or take up a
certain quantity of the vapour which continually rises from it; for air
absorbs a certain quantity, and a certain quantity only, of the vapour
of water; but this quantity is determined by certain circumstances,
for instance, the warmer the air, the more it will absorb, the less
the pressure on the air, the more it will absorb, and the drier the
air, the more it will absorb, that is, the less moisture it has already
got, the more will be required to make up that quantity which the other
circumstances permit it to contain. Now, what takes place if a warm,
dry, light current of wind blows over the sea, landward? Why, all the
vapour given off by the sea, to the amount of millions of gallons, is
absorbed and carried inland by the wind or current of the air, and this
continues onward, laden with moisture, until it meets with one of the
several circumstances which shall cause it to be incapable of holding
the quantity of moisture which it has already got; for instance, it
meets with another current of air colder than itself, these mingle,
the vapour of water is condensed by the cold, and a cloud is formed.
This consists of minute particles of water suspended in--not absorbed
by--air; these particles gradually collect, and down falls the rain
on to the earth. This drains off from the surface, forming rills,
which collect as they descend, by their own weight, into the lowest
channels of the ground, and form into streams and rivers, and back
into the sea comes the water which the air had taken away, with this
difference, that it is free from salt and fit for the many uses to
which fresh water alone can be applied; when the vapour rises from the
sea, none of the saline matters rise with it, for, although the water
is volatile, yet they are not, and this is the whole source of fresh
water. It is distilled in the great laboratory of Nature, and gives
nourishment to all the living beings who dwell on the land and in the
rivers and lakes; or the rain may sink into the earth and be carried
for miles and miles under ground, running through some porous stratum,
such as gravel, until it flows out in the form of a spring, bubbling up
amongst flowers and weeds, and forming the source of some river, which
receiving the rain and all the springs in the country through which it
flows, finds its way back into the ocean at last.
[Illustration: MOUNTAIN STREAM.]
This is the way in which all rivers and streams are formed. An enormous
extent of land thus drained gives rise to thousands of rills, which
collect into streams of goodly size, meandering through valleys and
pouring their tribute of waters into a main stream, which at last
accumulates by additions to its course, and becomes one of those great
water-courses which form the highway through a continent. The Amazon,
Hoang-Ho, Ganges, Nile, Danube, and Volga, may be cited as some of
the greatest water-courses and highways of civilisation. These great
rivers are navigable for large ships, even for many hundreds of miles,
and it is most fortunate that this navigation is so seldom impeded
by falls; for these, although among the grandest and most beautiful
objects of nature, yet put a stop to the navigation of a river which
would otherwise be passable for hundreds of miles further. Rivers
which run through districts subject to periodical rains, or those
whose sources lead from mountain slopes where vast quantities of snow
are deposited in winter which melts on the approach of summer, are at
such seasons of the year suddenly augmented, and generally overflow
the banks and inundate the country for miles. This is in many cases a
very great misfortune, as it spoils the land, reducing it to a swamp,
but not in every case; the overflowing of the Nile brings down with
it a great quantity of fertilising vegetable matter, and serves to
manure the whole district, for the soil being extremely porous and the
heat great, the moisture is soon got rid of, and hence it was a custom
of the Egyptians to celebrate the rising of the Nile by feasts and
ceremonies.
Lakes are formed in the same way as rivers, but, being surrounded by
high land, have no outlet for the waters so that they may flow back
into the sea. If a lake were about to be formed it would be in this
way--the rain descending on the surrounding high lands would run in
rills to the lowest part, and there collect, forming a pool which would
gradually increase in size as the water flowed into it, this increase
continuing until the surface became so large that the evaporation from
it exactly equalled the supply, it would then extend no further, but
remain a permanent lake or inland sea, giving off vapour to refresh the
surrounding country, and again receiving it back by streams and rivers,
as does the ocean.
There is scarcely a spot known on the surface of the earth, which does
not show strong evidence of having, at some former period, been the
bed or bottom of some sea or lake. Some of these evidences may be seen
in the strata or layers of earth forming the sides of the cliffs which
abut on the sea-shore, and which could not have been produced by any
other agency; these strata contain so many marine shells and other
matters peculiar to the sea, that the fact does not admit of doubt that
they were there produced. These same strata are met with throughout
the land; in sinking wells and mines, the same strata are cut through,
and have a known and uniform succession, with but few exceptions; the
cliffs, however, are the most convenient places to see these strata.
That the same process of alteration in the position of the water and
land is still going forward, is shown by many evidences, such as towns
which were once on the sea-shore, being now some distance from it, as
the City of Norwich, and in other cases the reverse. The chalk cliffs
at Dover, Ramsgate, &c., show the action of the sea in the corroded
state they present, and slips or falls of great masses which have been
undermined by the sea, are frequently occurring.
[Illustration: CLIFFS, SHOWING STRATA.]
The ancient town of Ravenspurn, at which Henry IV. landed, has entirely
disappeared, and others, recorded to have been situated on the shore,
have now only their names left. The parts of the shore most rapidly
corroded by the sea, are those composed of sand, chalk, and clay,
while those composed of the harder kinds of sandstone or of granite,
have been but little wasted away, so that they project and form the
headlands, while in many cases deposits of mud have extended them.
There are many other causes which determine the elevation or depression
of the land, besides the action of the sea and earthquakes, such as
winds, frosts, &c.
[Illustration: CHALK CLIFFS, DOVER.]
[Illustration: GREAT WAVES AT SEA.]
[Illustration: DEAD CALM.]
The slightest movement of the air communicates motion to the surface of
such a great sheet of water as the sea, and this motion is gradually
increased till one ripple meets another, and the power of both goes
to form the next, so that they acquire a very considerable size;
when a gale of wind blows, the rolling of the waves far out at sea
becomes terrific, and they rise like mountains, chasing one another
over the wide ocean. But sailors rather like a smart breeze, and more
especially did they a few years ago, when the wind was all they had
to depend upon for onward progress. In those days a calm which would
sometimes last for weeks together was to them most fearful, for it was
often a source of great distress and privation, especially if short of
provisions; the sea would then look like a great pool of stagnant water
covered on the surface with sea-weed and animalculæ, and fearful it
must have been when food was failing, and no hope of progressing but
the springing-up of a wind. But, in these days, with the assistance
of steam, a calm is the very time in which most progress is made,
and there is no doubt but a time will come when it will be matter of
wonder that men could ever have trusted to so uncertain an element as
the wind; yet, if it were not for the winds, currents, and tides, the
sea could not maintain its state of purity, for its saltness is not
sufficient to prevent the growth of fungi and all sorts of animalculæ,
which, from their decay, would produce noxious gases and be most
injurious to animal life. Its constant motion alone prevents this,
and the spores and germs are tossed about until destroyed and eaten
up by the inhabitants of the deep who devour every kind of organic
matter which is deposited in the sea, and thus it is that the waters
of the ocean are so bright and clear that an object can be seen at a
considerable depth.
That the constant currents of the sea prevent the formation and growth
of sea-weed, is clearly shown by the great "Sargasso Sea," or tract of
weed (_Fucus natans_), called the Gulf-weed. This great tract embraces
thousands of square miles, and is situated in the very middle of the
Atlantic Ocean, where there are but few currents; but surrounding it
is the Gulf-Stream, an enormous current of water running at a regular
rate of four or five miles an hour. This Gulf-Stream is supposed to be
caused by the same laws and influences which determine the trade-winds,
namely, a constant rarefaction of the water at the tropical parts of
the earth, and a corresponding condensation at the Arctic portions,
for warm water is much lighter than cold, and when the waters of the
tropical regions become lighter the heavier waters of the cold regions
pressing down more forcibly tend to raise them above their proper
level; they therefore flow towards those very parts which have sunk
down by their contraction, and a constant current takes place--this
current is the Gulf-Stream. It runs from the Gulf of Mexico northwards
towards Newfoundland, turning by Iceland towards the British Isles, by
France and Spain, onwards to the coasts of Africa and South America,
the West Indies, and again to the Gulf of Mexico, although the return
current does not go by the name of Gulf-Stream. This great stream of
water warmed by the tropical sun serves the same two purposes described
under the section "Air" as being fulfilled by the trade-winds,
namely, a circulation and distribution of the superfluous heat of the
equatorial regions, warming the northern countries and cooling by the
return of under-currents those in the tropics. The fogs of Newfoundland
are caused by the great current of warm water entering the cold region
and carrying with them surface-currents of moist air, which the cold
condenses into fog, just as the breath is visible in a cold atmosphere.
England owes its moist and mild climate to the same cause.
The sand which lies upon the sea-shore is produced by the action of the
waves constantly dashing against the earth and rocks of the coast, and
is mostly composed of what chemists call "silex," or silica, which is
a chief constituent of most rocks and earths; these, being worn down
by the action of the waters, form sand. The fragments of these rocks
(especially granite) and those which contain silica in the form of
minute crystals, are soon rolled and rubbed together until they are
ground to powder, but it is doubtful whether any sand exists at the
bottom of the deep seas far from shore, as the waters there lie--and
must have laid--perfectly quiet ever since they were seas, for the
greatest storm that ever rages does not affect the tranquility of
the sea more than a few fathoms beneath its surface, so that a stone
dropped in the middle of the Atlantic Ocean, could be picked up after
a hundred years exactly where it fell, were it possible for any to
find out the spot and descend; but the bottom of some deep seas, as in
the antarctic regions and the north Atlantic Ocean (as the soundings
between Ireland and America have lately shown), is covered to an
unknown depth with what had been supposed to be sand, but which is not
sand at all, but a wonderful collection of minute shells and coralines,
which to the unassisted eye have the appearance of sand. They are
the silicious shells and coverings of minute vegetables and animals,
these creatures, being coated with silica (a substance indestructible
by age and the action of water), fall to the bottom of the sea and
there accumulate in such countless myriads that they form this fine
substance, long mistaken for sand, but between which, in reality, there
is a marked distinction, the one being formed by the disintegration and
grinding-up of rocks, the other the product of organic life; this, when
it has accumulated for ages, will, in all probability, form some island
or part of a continent, and be the site perhaps of some magnificent
city, reared upon a foundation of these minute wonders of the deep,
whose skeletons will have become consolidated into a hard and compact
stone, of which its houses and churches will, in all probability, be
built.
This is not imagination, as such occurrences have really taken
place--all our chalk cliffs and downs constitute part of an immense
stratum. Now, every grain of this chalk contains and is made up of
thousands of minute shells and corals. These chalk downs were once the
bed of some ocean which, in all probability, was filled up by their
remains.
What are the railroads and works of men's hands compared with this? Of
this chalk (hardened by pressure into limestone) most of our public
buildings are constructed, or (changed by pressure and heat into
marble) our statues of great men have been carved. What a mockery to
choose marble as the medium of rendering our heroes immortal--itself
the very type of mortality, being formed by the death of millions of
creatures.
In Dr. Carpenter's work on the microscope occurs the following:--
"Thus, when we meet with an extensive stratum of fossilised
_Diatomaceæ_, in what is now dry land, we can entertain no doubt that
this silicious deposit originally accumulated either at the bottom of
a fresh-water lake or beneath the waters of the ocean, just as some
deposits are formed at the present time, by the production and death of
successive generations of these bodies, whose indestructible casings
accumulate in the lapse of ages, so as to form layers, whose thickness
is only limited by the time during which this process has been in
action.