OCEAN CURRENTS AND ICEBERGS.
Aweek 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 youngmen 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 thepangs 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 theearth 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 bornof 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 ofheat 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 theNorth 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 Seaand 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 theMississippi. 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 isthe 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 topile 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 variousagencies, 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 icepushes 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 southernhemisphere 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 mileslong 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 icebergrepresentsa transfer ofheat 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 warmervales 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.
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 toattempt 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 enjoyand 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.”
COMBUSTION.—COAL-BEDS.
Another Lord’s Day comes, and no change has taken place with the class which calls for mention. Ansel still walks in darkness, ready indeed on every occasion to manifest his concern for the salvation of his soul, diligent in reading the Scriptures, frequent in prayer, and giving yet no indication of a flagging of his avowed purpose to follow Christ, but he receives no comfort and peace. A painful and distressed interest is becoming more and more concentrated upon him. What will be the end of his groping in darkness? This cannot last always. Unless the hindrance, whatever it be, which prevents the exercise of faith, be seen and removed, Ansel will probably soon go back to his former careless state, and, it may be, become tenfold more obdurate than before. He will be likely, on theone hand, to become self-righteous from his supposed effort to come to Jesus, and, on the other, discouraged and despairing, feeling that for him effort is vain and salvation unattainable. While he remains in this state the very lapse of time is dangerous. All feel concerned for him, but no questions are asked, and the lesson goes on as usual.
“The method of transferring heat which we are now to examine is wholly different in principle from any which we have as yet considered. I refer to the production of heat by combustion. The transfer of heat by combustion cannot be compared for vastness with those great movements of heat which have before claimed our attention, yet for the comfort and well-being of the human race combustion is exceedingly important. Without that command of heat which combustion gives, man could not rise at best above the savage state, and in fact could hardly exist upon the earth. We smile at the Grecian myth that Prometheus stole fire from the gods and brought it to men in his reed staff, but fire is certainly worthy of being counted one of God’s great gifts. But whence comes the heat of combustion? Is it a new and originalgeneration of heat, or is it merely a transfer? Will some one explain this?”
“I don’t think that I can tell,” said Samuel. “I remember the principles you have given us about the nature and production of heat, but I do not know how to apply them to combustion.”
“I did not suppose that you would be able to explain all the phenomena of Nature at sight, yet the production of heat by combustion is not difficult to be understood. The burning of wood and coal is chiefly the union of oxygen with carbon. The oxygen of the air unites with the carbon of the combustible. The attractive force between oxygen and carbon is very strong. When they unite, the atoms of oxygen dash against the atoms of carbon with great violence. As they dash one upon another their motion is lost, but by the laws of transmutation of forces that lost motion reappears as heat; that is, the motion of the atoms as they fall the one against the other is changed to that vibration of the atoms which we call heat. The atoms of carbon, in their separation from oxygen, may be compared to weights suspended, ready to fall. Let once the cord be cut, and the weight falls and dashes against the earth; its motion in falling islost, and reappears as heat. So carbon is suspended, so to speak, waiting to unite with oxygen. But how is the weight raised? How is carbon brought into this state of suspense, waiting to dash upon oxygen and develop heat? That is not its natural state.
“Carbonic acid is found everywhere mingled in small proportions with the atmosphere. This carbonic acid is nothing else than carbon and oxygen united in the proportion of one atom of carbon to two atoms of oxygen. This is the natural state of carbon. This carbonic acid is the food of plants; it is this which supports all vegetable growth. The carbonic acid is absorbed by the leaves of plants and trees, and in the hidden laboratory of the leaf, by what process is one of the undiscovered secrets of Nature, the carbon is separated from the oxygen, the oxygen is discharged through the pores of the leaf, and the carbon is carried into the circulation to build up the fabric of the woody fibre. That which the most skillful chemist in the world cannot do, except by indirect processes and at a high temperature, the leaves are doing directly at the ordinary temperature. Vegetable growth is a deoxidizing process. To accomplish this anenormous force is requisite. To separate carbon and oxygen, a force is demanded which is able to overcome their powerful attraction. How shall we estimate the strength of this force? In order that they may unite, as in the explosion of gunpowder, solid rocks are torn asunder. The attraction of carbon and oxygen is strong enough to tear great rocks in twain. It is this attraction which sends the cannon ball and the shell like meteors of death upon their errands of destruction. This great force must be overcome; carbon must be separated from oxygen and built into trees. This is the lifting up of the weight. But whence comes the force necessary to accomplish this? From the sunbeam. The heat of the summer’s sun, employed as force, is used to deoxidize carbonic acid. Heat is used, and used up, in lifting the weight which in its fall shall generate again a like amount of heat. The combustion of wood produces the same amount of heat as was needful to separate its carbon from the carbonic acid of the air. Vegetable growth is thus a cooling process; heat is withdrawn from use as heat, and is employed as force. As force it has nothing to do with temperature. The summer’s heat, employed invegetable growth, reappears in the blazing billets of the kitchen fire. Heat is condensed and solidified, so to speak, and placed under man’s control. In this solidified form heat may be laid up in store or transported at pleasure.
“The grandest application of this principle is seen in the formation of the coal-beds. At some early period in the unmeasured ages past, the temperature of the earth must have been much higher than it now is; the air was filled with moisture, and carbonic acid abounded. As a consequence, there was an enormous vegetable growth. This, as we have seen, is a heat-consuming process. The heat is withdrawn from the air and employed in deoxidizing the carbonic acid. This vast vegetable growth—enormous ferns and coniferous trees—fell, and was swept by rivers or by floods into valleys, or the beds of lakes, or the sea; the sediment of the waters covered it, and there, shut up from the air and subjected to a heavy pressure, this vegetable mass underwent a slow transformation. Peter, have you ever seen a coal-pit? I do not mean a coalmine, but that which charcoal-burners call a coal-pit.”
“I have seen them many a time.”
“Tell us, then, how wood is burned to coal without being burned up.”
“The wood is set on end, closely packed in the shape of a mound, and then covered with earth. Fire is kindled in the middle of the pile, and just enough air admitted through air-holes at the bottom to keep up a slow burning. It burns just fast enough to heat and dry the wood without burning it up.”
“The same process,” said Mr. Wilton, “went on in the formation of the coal-beds, but very much more slowly. Under the pressure of earth and water the vegetable deposits lie smouldering, not for a few days, but probably for ages, till nothing but the carbon remains, and that pressed into a solid mass heavy as stone. Veins of coal are found interspersed with layers of earth and rock, layer above layer, and these layers are commonly not level, but more or less inclined and sometimes broken. This shows that a deposit of driftwood was made, then a deposit of sand or clay, then another deposit of vegetable material and another layer of earth. At length, by internal convulsions, the whole surface was raised from beneath the waters, and in due time the coal-veins were laid open, and the coalbrought out for the use of man. Then the force so long pent up and held in suspense is set free; the stored-up heat of the geologic ages is brought out for use. The excess of heat in that ancient period is handed down to these later times. How sublime this transfer of heat! It carries us back, in imagination, to the ‘heroic ages,’ so to speak, of the history of creation. By other methods heat is treasured up for a day or a year: by this method it is kept in store for myriads of ages. We see that the same natural forces were working in those early ages as to-day, and the same benevolent Creator was arranging the affairs of the world for man’s advantage. The sunbeam which streamed upon the earth long ages before man was created is to-day smelting ores, driving machinery, dragging ponderous trains of loaded cars, and ploughing the seas with freighted keels. This seems like a fairy-story or a dream, but instead of that it is the soberest of philosophic and scientific truth.
“We ought also to notice the internal heat of the earth. This has been handed down from the day of creation, it would seem, till the present. No new principle is seen in the earth’s internalfires, but a sublime illustration of the storing up of heat in a hot body and its slow radiation.
“The origin of the internal heat of the earth we can only conjecture. Perhaps God created the various elements separate, uncombined, and allowed them then to combine according to their natural affinities. This sublime conflagration of all the elements of the earth would generate the highest temperature which could be produced by combustion. The elements would melt with fervent heat; everything which could be vaporized by heat would be turned to vapor. Then radiation of heat would begin. Vapors would sink to fluids and fluids turn to solids; a hard crust would be formed on the surface of the globe through which the heat of the still molten mass within would be slowly conducted and escape. Upon this internal heat the earth depends in no small degree for its temperature. The heat generated perhaps upon the day of creation helps now to render the earth habitable.
“That the earth was once in a fluid state and has lost a portion of its heat by radiation is indicated by several facts. It is one of the received beliefs among geologists that at some period in the past the temperature of the earthwas much higher than it now is. The animals and plants which flourished during the ages when the coal-fields were deposited show that sea and land were warmer than at present. It is believed that the change of temperature has taken place on account of the cooling of the earth from radiation. The rate of radiation is so slow, however, that no farther sensible change of temperature can take place for thousands of generations.
“The form of the earth also indicates that it was once fluid. The earth is an oblate spheroid, a flattened sphere, and has that degree of flatness which a fluid mass would assume if revolving at its present rate. The earth swells at the equator and rises thirteen or fourteen miles above the sea level at the poles. The waters of the ocean move freely and take the same form as if the whole globe were fluid, and the solid parts of the earth have the same degree of convexity, which shows that it took its form from its own rotation upon its axis while in a fluid state. This would also show that in the primal ages, when the earth was in a plastic or fluid state, it had the same rate of rotation as at present.
“The lifting up of the mountain ranges alsois best explained by supposing that the earth was once molten. The earth cooled, a crust was formed, and by farther cooling and contraction of the molten mass within the crust wrinkled and formed mountain chains. Thus the higher temperature of the geologic ages, the form of the earth as if it were a revolving fluid mass, and the corrugation of its surface—these, joined with its present internal heat, point to the fact that it was once molten and fluid to its surface. The benefits of this heat laid up in store on the day of creation we still enjoy.”
“Before the class is dismissed,” said Mr. Hume, “I should like to say a few words.”
“I have nothing farther to say to-day,” answered Mr. Wilton, “and we should be glad to hear you now. Say on.”
“I wish only to say that these lessons have led me to such thoughts of God’s wisdom and goodness as I never had before. Of course it is not strange that this should be the case with me. I now look at everything with new eyes. It is not merely this one element of heat in Nature that moves my admiration, but I have been led to consider a thousand things in which the goodness of God is shown. My thoughts of thedivine goodness are as fresh and interesting to me as my impressions of his righteousness and holiness are startling. For years I have tried with might and main to look upon the dark side of the world and to exaggerate its physical evils. I have searched for disorder and want of adaptation. As long as I misunderstood the purpose of the creation, I thought I was successful in impugning the wisdom of the arrangements of this physical world. While I supposed that the earth must needs be the Creator’s masterpiece in beauty and pleasantness and all manner of perfections, designed just to give sensual pleasure to its inhabitants, I could find, or thought I found, many faults in the Creator’s work. Now I withdraw all my former charges. My eyes are opened. The rougher elements of man’s life will henceforth have a new meaning to me. I see that God seeks not so much present pleasure for men as their holiness. He lays a solid foundation for their happiness. He seeks to render men blessed by bringing them into likeness and union with himself. These are new views to me, and I thank my heavenly Father that this new light has dawned upon me. I feel now that I can bear the ills of this lifecheerfully, understanding that the Lord is using them as a means of spiritual discipline. It seems to me as if this lower world and man’s lowly life were already glorified by a beam of light falling from heaven. I hope that my young friends have been as much profited as I have been.”
“I rejoice with you, Mr. Hume. ‘We know that all things work together for good to them that love God.’ This light has shone upon me for many years.”
ECONOMY OF HEAT.
In this final lesson I wish,” said Mr. Wilton, “to bring before you some general views of the whole subject of the agency and management of heat.
“When Jesus had fed the five thousand men upon the mountain side by the Sea of Galilee, he said to his disciples, ‘Gather up the fragments that remain, that nothing be lost.’ The Christ who spoke these words was the same Christ by whom ‘all things were created that are in heaven and that are in the earth, visible and invisible.’ These words inculcate the propriety of saving, the very opposite of extravagance and wastefulness. The same prudent economy we find in all God’s works. Nothing is wasted. God provides bountifully; he is not stinted in his works; we find nothing narrow or mean; his resources are ample for all his undertakings. Perhaps acareless observer might charge him with prodigality and wastefulness. The wilderness rejoices in beauty and fertility upon which no human eye gazes, and which supplies no human want.
‘Full many a gem of purest ray sereneThe dark unfathomed caves of ocean bear;Full many a flower is born to blush unseen,And waste its sweetness on the desert air.’
Rich fruit grows ruddy and golden in the autumnal sun only to fall and decay. How small a part of the seeds which might germinate and reproduce the parent plant ever fulfill this their legitimate object! But this is not waste. As for the beauty with which the unpeopled wastes are smiling, we know not what other beings besides man ‘grow glad at the sight.’ Fruits and grains and seeds were appointed as much to nourish the animal kingdom as to reproduce plants and trees. And that which decays is not wasted. The oak lifts high its leafy arms and does battle with the tempests for a century, and then having served its purpose in Nature, if man does not call it to the higher mission of serving his purposes, Nature begins to pull down the structure she has reared andrebuild the elements in other forms—such forms as man perchance may need. The fruit that falls and decays is not wasted; it shall blush with golden tints in other forms and in other years. God pulls down the old that he may build the new. The same elements appear and reappear in a thousand shapes. There is endless change, but no waste. This sentiment, ‘Gather up the fragments, that nothing be lost,’ which is proclaimed throughout all Nature, is uttered most emphatically in the management of heat. God has provided most bountiful stores of heat, but has left no heat to go to waste. Will you, Mr. Hume, suggest one of the general arrangements for the economical use of heat?”
“I think that the arrangement for economizing heat which ought to be mentioned first is the confinement of heat to the locality where it is needed.”
“Will you explain that a little farther, Mr. Hume?”
“All living creatures are confined near the surface of the earth. They penetrate only a few feet into the earth and soar a few hundred feet above it. Heat is therefore confined to theregion of the earth’s surface. It penetrates but a little way below the surface, and when warm air rises into the higher regions, heat becomes latent. The higher parts of the atmosphere are cold, and in the empty spaces of the heavens the temperature is we know not how low. God has provided for heating only that part of the world which needs to be heated. I think you spoke of this in some one of the earlier lessons.”
“Perhaps I did. But I refer to it again to call especial attention to the idea of the economical use of heat. Who will mention another method by which heat is economized?”
No one answered.
“I asked the question, but did not expect an answer. God shows economy in the use of heat by accomplishing many different results by its agency. I do not mean that the same identical heat accomplishes different results at the same time. The same force cannot accomplish two works. As man cannot spend his money and at the same time keep it, no more can heat be used and not used up in that form. The heat which raises the temperature can do nothing else at the same time, and when it is employed asforce it ceases to affect temperature. But by this one agency of heat the Creator brings very various works to pass. Heat expands bodies, relaxes cohesive attraction, and brings the chemical affinities into activity. By this means the elements of Nature are subdued to human uses, seeds germinate, all the processes of vegetable life go on, and digestion and nutrition are carried forward in the bodies of animals. By the agency of heat the winds blow, the deep waters of the ocean circulate, clouds are formed, dew and rain refresh the earth, rivers flow, and all the activities of life fill the world. The employment of one agency for the accomplishment of so many works indicates economy in the expenditure of force and means. Moreover, the same heat appears and reappears again and again, passing from the sensible to the latent form and back again, asserting itself alternately in raising the temperature and as active force. A beam of heat falls upon our world: it is partly absorbed by the earth, and warms it. A part of that warmth is used in setting the chemical affinities in action in the sprouting of seeds; a part warms the air by conduction; a part is radiated, and being stopped by the vapor in theair, warms it; the heat of the air is partly used in the evaporation of water: the vapor formed is condensed and waters the earth, and gives out the heat by which it was formed; that raises the temperature of the air; a part of it is used in deoxidizing carbonic acid and building up the forests; the forest tree falls by the woodman’s axe, is burned for fuel, and gives out its heat again, or if it falls and decays, the result is the same; the heat given out by combustion cooks the laborer’s dinner and warms his room, or it goes out again, and is used in preparing food for the growing wheat; that wheat is used for food, and by slow combustion in the blood the heat is again evolved, the body is warmed, and the chemical operations of digestion and nutrition are maintained; the heat is radiated or conducted from the body into the atmosphere, and again raises the temperature and goes to do other work. At last, so far as our earth is concerned, it escapes into the stellar spaces, and goes to bless other worlds. In all these operations no heat-force is frittered away and wasted and lost. This is one of the accepted doctrines of physical science. Heat is used bountifully, but economically and without waste.
“Even the inequalities and variations of temperature must be counted economy in the use of heat. The heat of midday is not needed at all hours, and therefore it is not always provided; the heat of summer is not always useful, and is therefore not given; a higher temperature for a part of the year and a part of the day is necessary, and is bestowed. The smallest amount of heat is so disposed as to accomplish the largest result. Keep in mind, then, the economical aspect of God’s management of heat.
“I would also have you remember how few are the principles involved in all the ways and means for transporting heat and equalizing temperature. All the various phenomena which we have examined can be brought under two general principles. The first principle or method is the heating and cooling of bodies. Bodies absorb heat; they part with their heat by conduction or radiation. If they are heated and cooled without change of place, heat is transported in time, but not in place. If the body be removed from one place to another between the heating and the cooling or between the cooling and the heating, heat is transported in both time and space. This applies alike tosolids, liquids, and gases; each one is a carrier of heat in proportion to its specific heat.
“The second principle or method is the transportation of heat by the change of sensible to latent heat and its restoration to a sensible state. Under this principle there are four cases:
“1. Heat is employed in the evaporation of liquids, and is restored again to use as affecting temperature by the condensation of the vapor.
“2. Heat is employed in liquifying solids, and becomes latent thereby, and returns to the sensible state when the liquid solidifies. These two principles find their grandest application in the changes of water: of this application I have chiefly spoken; but they apply also to other bodies—to metals as well as to liquids.
“3. Heat is rendered latent in the expansion of gases from removal of pressure, and latent heat becomes sensible by the compression of gases.
“4. Heat is employed in the deoxidation of carbonic acid or other combinations of oxygen, and is evolved in combustion. While in the latent condition, heat may be kept without loss for an unlimited period of time or transported from equator to pole. By the various applicationsof these two general principles, all the different methods of equalizing temperature are determined.
“I would have you remember also that these processes for transporting heat and modifying temperature are not confined to the regular changes of days and seasons and the permanent differences of zones, but apply to every possible difference of temperature. One minute the sun shines out in full splendor; the next, a cloud hides his face and cuts off his fervent beams; the methods employed to soften the heat of the one minute and the chill of the next are the same which equalize the temperature of the seasons. Evaporation carries off the heat from the seething tropics, evaporation carries off the excess of heat from the bodies of animals and men. The same methods are equally efficient upon the grandest and upon the smallest scale.
“In this connection let me give one or two illustrations of the delicacy with which general principles adapt themselves to the minutest circumstances. When the earth is wet, it is fitting that evaporation should go on rapidly and remove the excess of water, but when the ground is drier, it is fitting that evaporation should bechecked and the remaining moisture spared. This result is secured not merely by the lack of moisture at the surface, but also by the decreased capacity of the earth for absorbing heat. A dark color absorbs heat more readily than a lighter color, and the earth becomes, as a general rule, darker when wet; and lighter when dry. Moist earth, therefore, receives heat more readily than dry earth, and the excessive moisture is the more rapidly carried off by evaporation.
“Another more interesting illustration is presented by the odor of flowers. In its place I told you that watery vapor hinders the radiation of heat from the earth. Dark heat is absorbed by it. The same is true of other gases, and also of the odors of fragrant substances. A bed of flowers fills the air around with odors. By these odors much of the heat radiated by the earth is stopped. By this means the air around the blooming flowers is warmed. The invisible fragrance raises the temperature and secures for the blooming plants a more genial atmosphere. The Lord provides for the flowers when most of all they need to be cherished by a congenial warmth.
“This completes what I have to say to you upon the subject of heat. I might have gone far more into particulars, and extended these lessons over six months instead of three. We started with the design of finding out whether the works of Nature have anything to say about a wise and good Creator. We could not examine the whole circle of God’s works, and therefore chose a single department—that of heat. I will leave yourselves to decide whether we have found marks of divine wisdom and goodness, whether Nature has had anything to say tousabout a Creator.”
“It seems to me,” said Samuel, “that if the works of Nature do not show God’s goodness and wisdom, it would be hard to tell what works would show them. I think I shall always, after this, look upon the earth and sky with more interest than I have ever felt in them before; I shall always look upon them as having something to do with God.”
“We certainly ought,” said Mr. Wilton, “to study Nature in such a manner and with such a spirit that we shall be led to reverence and worship the Creator. Some very good men are afraid of scientific study, as if there weresomething in it to draw men from belief in the Scriptures and the Jehovah revealed in them; and it cannot be denied that not a few unbelievers have tried to find a foundation and a defence for their infidelity in scientific studies; but such men are not made skeptics by earnest and reverent study of God’s works: they were unbelievers before and aside from physical studies, and they only try to glorify their rejection of the Bible and Christ by deifying science and the creation and holding them up in opposition to inspired revelations. If ever you find the works of God separating you from God, you may know at once that you misunderstand those works or come to them with a wrong spirit. ‘The undevout astronomer,’ it has been said, ‘is mad,’ and the same might, with good reason, be said of every undevout student of physical science.
“In selecting heat for our examination, I did not take the only rich department of Nature’s works. The practical chemist would find a richer and broader field of research, and so would the anatomist and animal physiologist, the geologist, or the physical geographer. I purposely chose a comparatively narrow field,in order that our course of study might not become wearisome by its length. You will find ample scope in the fields of natural science for your largest powers, and enough to carry your thoughts reverently to the great Creator and Governor.
“In one respect the study of Nature resembles the study of the Sacred Scriptures. It is a revelation; it is an embodiment of God’s thoughts; in it God has expressed himself; and Nature, by most suggestive symbols and types, teaches much more moral truth and spiritual sentiment than some men think. In the brute creation it gives us, in pantomime, all the virtues and graces and all repulsive vices and cruel passions. To this book of Nature we ought to come without prejudice, reverently inquiring what is written therein. We must study it thoroughly and interpret it as we interpret the written word, comparing Scripture with Scripture. It is a great attainment to be able to read and understand the thoughts of God embodied in his works.
“In another respect, the book of Nature and the Sacred Scriptures have very little in common. The Bible is occupied pre-eminently withmoral duties and spiritual relationship. Its great themes are sin and salvation. Christ is the great central truth. One might compare the Scriptures to a picture in which one central figure seizes every eye, and by whose radiance the whole picture is filled with light, and that central figure is Christ; or we might compare the Bible to a sublime oratorio, the glorious symphony of the ages; through it all is heard one strain, sweetly exultant as angel voices, faintly heard at first amid the sadness of the fall, but rising still above the terrific bass of Sinai and its ever-repeating echoes, growing more clear and strong upon the harps of the prophets, till its rapturous beauty pours itself triumphant along the plains of Bethlehem. In this revelation of salvation from the guilt and ruin of sin the Bible stands alone. Upon this subject Nature is silent. Salvation by Christ is the gem enshrined in the Scriptures. But what is the setting for this gem? The works of God on the earth and in the heavens. The prophets were men in sympathy with Nature. How David sung the praises of the divine handiwork!—‘O Lord, how manifold are thy works; in wisdom hast thou made them all.’ ‘The heavens declare the glory ofGod and the firmament showeth his handiwork. Day unto day uttereth speech, and night unto night showeth knowledge. There is no speech nor language where their voice is not heard.’ How Christ unfolded the deepest spiritual truths by the symbols of Nature! But if the casket be so worthy, what shall be said of the gem which is enshrined within? That is the pearl of great price. To that book which speaks in no doubtful voice of deliverance from sin let us turn with increasing reverence; and above all, let us come to him who came to reveal our God, who came to be as well as to make a revelation of God, being himself ‘the brightness of his glory and the express image of his person.’ I am glad that you all now feel that you know him whom to know is everlasting life.”
From these words of Mr. Wilton you will conclude that Ansel has at length found rest in Christ. In another brief chapter I will tell you of his experience, and then bid you adieu.