OCEAN CURRENTS AND ICEBERGS.
A week has passed since Mr. Hume made his frank confession. He went home
no lighter of heart than before, yet he felt in some respects different,
for he had attempted to do what was right in the sight of God. But he did
not feel the joy of sins forgiven. He had not looked upon Christ as a
Saviour for himself. He felt that God had distinctly set life and death
before him. His doubts were gone; the spiritual world was a reality;
Christ stood at his right hand and Satan at his left; he stood where the
path of destiny divided, the one path leading up to heavenly seats with
Christ, the other leading down to darkness and despair. A voice seemed to
be whispering in his ears, "This is the last call." He went to his chamber
determined, if possible, to settle the question of life or death before
he left the place and before he slept. He took his Bible, and on his knees
turned and read the Psalms at random. But the cloud of darkness only
gathered deeper. The words of David's penitential Psalm caught his eye:
"Against thee, thee only, have I sinned, and done this evil in thy sight."
He felt that these words of David were true in his case also. All his long
impenitence and bold unbelief had been against God. By night and by day,
for many a long year, before the sleepless eye of God, he had lifted up
his hand, almost defying the holy One, yet the lightning of God had not
smitten him. He wondered as much at the long-suffering of God as at his
own dreadful daring of the divine wrath. He had been taught better things;
he was trained to know the Scriptures and to go reverently to the house of
God, but he had turned from Christ and hope. He read on: "Deliver me from
blood-guiltiness, O God, thou God of my salvation." He felt that this
belonged to himself more than to David. David had shed the blood of
natural life, but he had destroyed the souls of men. He had stood chief
among unbelievers. He had led young men into infidelity. He had seen them
drink in his unbelief like water, throw off all restraint, and rush
headlong to ruin. He had wrought a work of evil which he could never undo,
and for which he could make no atonement. What was a confession in
comparison with the ruin he had caused? What could his confession do for
the young men already, perhaps, among the lost through his influence?
Could his late repentance call them back to life and hope? Would God
forgive and raise to heavenly heights a man who had dragged others down to
hell? Would it be possible that Christ should fill his soul with
blessedness while his victims were drinking the wine of the wrath of God?
A deep horror seized him. The darkness of eternal death seemed to enfold
him. Must he, then, after having caught a glimpse of life and joy, be cut
off from hope and be driven from God for ever? This would be just, but he
felt that he could not endure it. "O thou great and holy God," he prayed,
"I will ascribe righteousness to thee though thy righteous wrath shall
sink me to hell; but, O thou merciful God, my soul cannot endure thy
justice. The foretaste of thy wrath fills me with the pangs of eternal
death. O God, have mercy upon me. O God, blot out my transgressions.
Create in me a clean heart, and renew a right spirit within me. O Christ,
whom I have despised, cast me not from thy presence. Help me to submit to
thee. Help me to follow thee. Spare me that I may undo something of that
which I have done against thy glory and the souls of men. O Jesus, I can
do nothing to save myself. O Lord, have mercy on me, the chief of
sinners."
He read the invitations and promises of Christ, and prayed again. Again he
read and again he prayed. Little by little the promises of Christ stirred
a feeble faith in his heart; he felt that there was still hope for him,
and with the determination to cast himself upon the sure mercies of Christ
and to devote himself to his service, he threw himself upon his bed, and
being wearied almost to exhaustion, soon fell asleep. When he awoke it was
broad daylight. He had slept a sweet, refreshing sleep. But he was
refreshed not merely in body. He woke to a new world. His heart was filled
with sweet thankfulness. "How beautiful," he said, "is God's world! I
never saw it so before, but the earth and sky seem clothed in glory. But
most wonderful of all is God's goodness to me. I have rebelled against him
all my life, yet he has loved me and sought for my salvation, and now the
sunlight of his love has broken through the thick clouds of my sin, and a
day of hope and joy has dawned upon my life. Christ has indeed revealed
himself. Blessed be his holy name for ever and ever! What shall I render
unto the Lord for all his benefits? I will take the cup of salvation and
call upon the name of the Lord. I will pay my vows now in presence of all
his people. I will teach transgressors thy ways, and sinners shall be
converted unto thee."
All this was known to the people, for during the week Mr. Hume had spoken
of it in private and in public. He had told it to Mr. Wilton, and they had
rejoiced together.
Ansel and Peter had also regularly presented themselves at every meeting
as anxious inquirers desiring the grace of God. Peter had also on his
knees said from the heart, "Here, Lord, I give myself away," and had
received the assurance that his sins were forgiven. The Spirit of God
witnessed with his spirit that he was born of God. He began at once to
use all his influence to bring his young friends to Jesus. The addition of
two such workers as Mr. Hume and Peter, each moving in his own circle of
acquaintances, gave a fresh impulse to the religious interest, which was
now becoming deep and pervasive. Especially had Mr. Hume's conversion, so
clear and positive, confounded those who had sat "in the seat of the
scornful," and many came in now for the first time to see for themselves
what it could be that had mastered their cold, clear-headed leader in
unbelief.
But Ansel still walked in darkness. He had talked with Mr. Wilton, but no
light had entered his mind. He said that he thought he had submitted in
all things to the will of God. He was becoming impatient that Christ had
not come to him as to others. This was their condition as they came
together upon the Lord's Day. They all understood each other, and had no
need now to ask questions or make explanations. Mr. Wilton believed that
the study of God's works would not interrupt the working of the Holy
Spirit, and therefore went on with his lesson as usual.
"We have already spoken of the transfer of heat from the torrid to the
temperate and frigid zones by the agency of winds and watery vapor. These
carry heat chiefly in a latent condition. But great movements of heat take
place in a sensible state. In this transfer of heat, also, water is the
great carrier. The winds and vapor go freighted with latent heat above,
and the waters and wind go freighted with sensible heat below. We will
first examine the operation of the ocean currents.
"Not only do rivers run through the lands and hasten to the sea, but in
the midst of the oceans rivers are flowing in comparison with which the
Mississippi, the Amazon, and the Yang-tse-kiang are rippling brooklets.
The earth is belted by these ocean streams traversing the seas. An ocean
current, called the Gulf Stream, issues from the Gulf of Mexico between
the Florida coast and the Bahama islands. It flows northward off the coast
of the United States, gradually increasing in breadth and spreading over
the Atlantic Ocean. It is deflected by the New England coast and the great
shoals off Newfoundland, called the Grand Banks, or else by another
current flowing southward from Baffin's Bay, and strikes across the North
Atlantic, bathing the shores of the British islands and reaching even to
Iceland.
"The general outline of the ocean currents is this: issuing from the South
Pacific, a current flowing eastward splits upon Cape Horn. The western
portion, called Humboldt's current, flows northward along the western
coast of South America, and is swallowed up and lost in the great
equatorial current of the Pacific. This is a broad current flowing
westward and covering the entire space between the tropics. Striking upon
the eastern shores of Asia, this equatorial current divides, one part
flowing northward along the coast of Asia, the other finding its way
through the many islands, sweeping across the Indian Ocean, and flowing
down the eastern shore of Africa on each side of Madagascar. Doubling the
Cape of Good Hope, the current continues in a north-westerly direction
across the Atlantic. Striking upon Cape St. Roque, this current again
divides; a part flows south and a part pours into the Caribbean Sea. From
the Caribbean Sea it issues as the Gulf Stream, of which I have already
spoken. This Gulf Stream impinges upon the western coast of Europe, and
pours partly into the North Sea and partly flows south off the western
coast of Africa, completing thus the circuit of the Atlantic. The currents
of the Indian and of the great Southern Oceans are as yet very imperfectly
understood. Of all the ocean streams the Gulf Stream is most famous and
best understood. I shall therefore use this as an illustration of the
agency of ocean currents in conveying heat and modifying climate.
"The waters of the Caribbean Sea are heated by the tropic sun to
eighty-eight degrees. From these heated waters the Gulf Stream issues
salter and warmer, and of a deeper blue, than the waters of the
surrounding sea. Its greatest velocity as it issues from the gulf is a
little more than three miles per hour. As it flows northward its velocity
diminishes, its breadth becomes greater, and its depth less. It covers
thus with its warm waters a broad belt of the Atlantic Ocean, and extends
its influence to the most northern part of Europe. You can judge of the
amount of heat which is removed from the tropics when I tell you that the
unmeasured flood of the Gulf Stream would swallow up three thousand rivers
like the Mississippi. This one ocean stream is many times greater than
all the rivers of the world. We feel the warmth of the Gulf Stream with
every wind that blows from the sea. To this the British isles owe their
mild, moist climate and perennial greenness, and by its influence a winter
in Iceland, upon the Arctic circle, is no more rigorous than a winter in
Montreal, twenty-one degrees nearer the equator. But what is the Gulf
Stream, though it be fifty fold greater than all the rivers of the world,
in comparison with the whole sum of the ocean streams? Upper currents and
under currents fill the sea. They meet the explorers of the sea
everywhere. The navigator drops his measuring line, and finds it swept
away and drawn out by unseen currents. All these movements of the waters
are in favor of the equalization of temperature. The cooler waters of the
frigid and temperate zones are mingled with the heated waters of the
tropics and exchanged for the equatorial waters. The transfer of heat
would not be greater if broad rivers of molten lava were flowing from the
equator to the poles.
"Another agency for the transfer of heat is the movement of ice, and
especially of icebergs."
"Will you not tell us," said Samuel, "how these ocean currents are
produced? I can understand how winds are formed, but I do not see that
these streams in the sea could be formed in the same way."
"I designed to speak of this, but for the moment it had slipped from my
mind: I am glad that you called my attention to it. I do not expect,
however, to give a full and satisfactory account of their origin. If I
should do this, I should succeed where every other man has failed. I shall
not attempt a full explanation. By some means or other, the waters of the
ocean are thrown out of equilibrium, and these currents are plainly an
effort to restore the balance or equilibrium of the waters. Many
influences and agencies conspire to disturb the equilibrium of the sea.
The attractions of the sun and moon are constantly counteracting the
attraction of the earth and lifting the waters, so to speak, above their
natural level. The tides produced by these attractions of the sun and moon
are the immediate cause of some of the minor local currents. The winds set
the waters in motion, tending to pile them up in one place and leave the
sea below its natural level at another. The effect of strong winds in
piling up the waters, even upon our great lakes, is very considerable. A
heavy east wind upon Lake Erie has been known to drive the waters toward
the western end of the lake so much as to leave Niagara River above the
falls almost dry. On the other hand, a heavy west wind drives the waters
eastward, and produces almost a flood in the river. The influence of
constant winds like the 'trades' acting upon an immense expanse of water
must be very much greater. Unequal evaporation tends to destroy the
balance of the waters. In the colder regions the evaporation is very
little, while within the tropics it amounts to about half an inch daily,
or fifteen feet per annum. The head of the Red Sea is two feet lower than
its mouth on account of evaporation. This unequal evaporation causes also
an unequal saltness, and consequently an unequal weight. The fresher and
lighter water cannot balance an equal bulk of salter and heavier water.
When once currents are started the revolution of the earth upon its axis
would affect them, just as the rotation of the earth affects the
trade-winds. Now, all these various agencies, and perhaps many others,
combine their influence to destroy the equilibrium of the waters of the
ocean. They unite and interweave their influence in a thousand ways beyond
all human calculation. The result is the ocean currents. But how much is
due to one cause and how much to another in the present state of knowledge
no man can tell. Only for a few years have the phenomena of ocean currents
been made the object of scientific observation and research. But the
effect of ocean currents in modifying climate is well understood, and the
modification of climate means nothing else than the transfer of heat. This
is all that I have to say of the rivers of the sea, and if there are no
more questions, we will now look at the movement of heat caused by
icebergs."
No question was asked, and Mr. Wilton continued:
"In polar regions there must be an immense formation of ice. Except in the
oceans, the movements of water are chiefly movements of water in the
condition of ice. Only for a small part of the year could water exist
unfrozen. Immense regions of the Antarctic continent seem to be covered
with one broad glacier. The ice pushes down into the sea until,
undermined by the dashing of the waves, it breaks off, and enormous
fragments are launched upon the deep waters. Sir James Ross saw in the
southern ocean a chain of such icebergs extending as far as the eye could
reach from the mast-head, many of them from one hundred feet to one
hundred and eighty feet in height and miles across. Captain d'Urville saw
one thirteen miles long and one hundred feet high. Its bulk was so vast
that though the waves were dashing against it not a tremor was
perceptible. Astronomic observations could be made from it as if it were
solid rock rooted in the heart of the earth. In the same manner icebergs
are formed in the northern ocean also. How much heat is given out in the
freezing of water?"
"About one hundred and forty degrees," answered Peter.
"In the formation of icebergs, then, heat is given out nearly sufficient
to boil an equal quantity of cold water. The icebergs float away toward
the equator. They come down from Baffin's Bay till they meet the Gulf
Stream off Newfoundland. In the southern hemisphere they come ten degrees
nearer the equator. As they float toward the tropics they slowly melt, and
in their melting they exact from the air and the sea where they melt the
same amount of heat which they gave up in their freezing. If they melted
at the same place where they froze, there would be no transfer of heat.
But they are formed in the polar regions; they give out their heat in the
frigid zone, while they melt and absorb a like amount of heat from the
temperate zones. In this manner the polar regions are exchanging with the
temperate zones ice for water. They borrow water, rob it of its latent
heat, and send it back in the form of ice. The temperate zones supply the
needed heat and bring the ice back to the form of water, when the polar
regions again borrow it, seize upon its heat, and again send it back in
the form of ice mountains. The effect is the same as if thousands of
railroad trains were transporting water to the frigid zones, leaving it
there to freeze and give up its one hundred and forty degrees of latent
heat, and bringing it back in the form of ice. Let us estimate the bulk of
one such iceberg as that seen by Captain d'Urville. It was thirteen miles
long and one hundred feet high, and we will suppose that it was four miles
broad. Standing out from the water one hundred feet, it must have sunk at
least eight hundred feet below the surface. This would give us the
enormous bulk of (1,304,709,120,000) one trillion three hundred and four
billions seven hundred and nine millions one hundred and twenty thousand
cubic feet of ice. The burning of one pound of coal will generate heat
sufficient to melt about five and a half cubic feet of ice. To melt one
such iceberg would require more than one hundred and eighteen millions of
tons of anthracite coal. This is the amount of heat given out in the polar
region by its freezing. This is the amount of heat transported from the
warmer to the colder regions. But what is one iceberg to the thousands
which drift yearly from the frigid zones toward the tropics?
"But even this hardly represents the entire transfer of heat by the agency
of icebergs. The icebergs are formed from the snows of polar storms, and
these are formed from the condensation and freezing of vapors. In the
process of condensation one thousand degrees of heat are given out. Every
iceberg _represents_ a transfer of heat sufficient to boil more than six
times its weight of ice water.
"One marked illustration of the effect of icebergs we ought to notice.
Down through Baffin's Bay icebergs are constantly floating. They are borne
on southward till, in the still waters of the Grand Banks, between the
polar current and the Gulf Stream, they float around and melt and
disappear. To these melting icebergs the chilliness and unfailing fogs of
the Grand Banks are due; and not only this, but the very existence of the
Banks is supposed to be due to the deposit of sediment, sand, earth, and
stone brought by polar ice.
"I have spoken only of the polar glaciers and the icebergs formed by their
pushing off into the sea. But the same transfer of heat is taking place,
on a very much smaller scale and within narrow limits, by the glaciers of
the Alps and every other mountain glacier. The glaciers are nothing else
than rivers of ice. Snow falls upon the mountain tops and valleys of the
mountain sides from age to age. The snow slowly changes to the structure
of ice, and by its enormous weight flows down through the gorges of the
mountain sides, till in the warmer vales below it melts and disappears.
We have not time to go into a full examination of all the interesting
phenomena of glaciers, but this one point you will notice and remember:
these rivers of ice--for they flow like rivers--cool the valleys and tend
to warm the mountain tops; of course upon the tops of the mountains there
can be no accumulation of heat, because, standing out into the eternal
coldness of space, and swept by winds for ever, and exposed by the
thinness of the air to a rapidity of evaporation unknown at the sea level,
heat is caught up and borne away in a moment.
[Illustration: TRANSPORTATION of HEAT.
Page 288.]
"This closes this department of our theme. I might have gone much more
into details and given you great stores of particular facts and figures,
but they would have added nothing to your understanding of the subject,
and we can hardly afford to devote our Lord's Day to mastering the details
of the natural sciences. We have now looked at some of the methods by
which the extremes of heat and cold, in day and night, in summer and
winter, and in the tropics and polar regions, are mitigated. The same
principles operate upon the smallest and upon the largest scale. If there
is need for me to attempt in a formal way to awaken in you admiration for
the wisdom and goodness of God shown in all these beneficent arrangements
for equalizing temperature, our study has been largely in vain. We have
only to remember that all these contrivances are the Lord's designs. He
created the world; he endowed matter with its qualities and forces, and he
gave it these qualities and forces for the purpose of using it as he has
used it. He planned all those contrivances by which he secures the comfort
and the good of man, and the fact that these natural agencies are fitted
for moral uses in recovering sinners to holiness and blessedness is but
the culmination of its adaptation to the uses of man.
"This, however, does not complete our course of study. A few other points
will demand our attention for two or three more lessons. But while we go
on with our studies of Nature, remember that the physical was created for
the sake of the spiritual; the spiritual is more important. Let us not
subvert the divine order and sink the high purpose of the creation to mere
material agencies and contrivances. To know God is greater and better than
to understand Nature. That we might know and enjoy and glorify the
Creator was the object of our creation. We cannot express it in better
language than that employed in the old catechism: 'The chief end of man is
to glorify God and enjoy him for ever.' That term 'for ever' includes the
present life as well as the future. We ought to know, enjoy, and glorify
God to-day. I hope that another week may find Ansel with some happy
experience in this matter."