AN EFFECTIVE SERMON.
Mr. Wilton preached the sermon spoken of at the close of the last chapter the next Lord’s Day morning. The more he thought upon the matter and inquired the mind of the Spirit, the more he felt that for a purpose the Spirit was calling him to unfold again the authority of God and the conditions of salvation. He gave notice of his subject, and invited all good men to pray that he might be able, like a good and wise steward of the mysteries of grace, to bring forth out of the treasure-house things new and old, and that the word might prove as a nail fastened in a sure place by the Master of assemblies. Much prayer was offered, and the people came together in a spirit of unwonted solemnity and earnestness.
Mr. Wilton prayed to the glorified Redeemer for his blessing: “O thou exalted Christ, we assemble in thy name and by thine authority. Thou hast bidden us not forsake the assembling of ourselves together for thy worship and the preaching of thy gospel. By thy grace we enjoy another of these sacred days. By thy death thou didst purchase for thy people eternal redemption. Thou hast wrought out for them a great and glorious salvation. For thy great love wherewith thou hast loved us thou didst empty thyself of divine glories, and madest thyself a servant among servants, and didst suffer in the garden, and die upon the cross, and enter the grave. Now thou art exalted at the right hand of the Father, a Prince and a Saviour, to give repentance and remission of sins. O thou that judgest men, thy justice is great and glorious as thy mercies. Years ago we tested thy love, years ago we felt the shadow of thy wrath; our guilt made us afraid and we cried unto thee, and thou forgavest our sins, and didst shed abroad thy peace in our hearts. In these recent days thou hast brought other sinners to feel their guilt. They have seen thee upon the cross, and have been smitten with anguish,and have repented, and thou hast received them. Others are bowed down; they mourn; they feel themselves poor and needy; they confess thy justice; they feel the need of thy salvation; they walk in darkness; they grope and find no light; they look unto thee from a distance; but they do not come to thee, they do not follow thee. Wilt thou not draw them to thyself? Wilt thou not bow their pride of heart and turn their wills and make their hearts tender, gentle, and believing? Wilt thou not smite the rock, and cause the waters of penitent grief to flow? Lay thy cross, O Jesus, upon their shoulders and upon their hearts, that they may bear it after thee and share thy glory. Open thou their eyes that they may see eternal destinies and look upon thy divine glories, thy beauty, and thy tenderness. Let them follow thee and trust in thee, strengthened and comforted by thy rod and thy staff. O Christ, for thine eternal love with which thou hast loved us, reach down thine arm mighty to save and lift us up. Lord, save or we perish. And speak thou by thy servant to-day, and cause all that hear to recognize the message not as his, but as thine.”
He read as his text Acts xvi. 30: “Sirs, what must I do to be saved?”
He briefly recited the arrest, imprisonment, and release of Paul and Silas. “The salvation for which the jailer cried out was not deliverance from the dangers of the earthquake, nor from the displeasure of the Roman governor. This was the bitter cry of a soul sinking under a load of guilt and trembling at the thought of God’s impending wrath. Some of you can appreciate his feelings and his fears. Your sins against God and Christ and the Holy Spirit have risen up before you; they stare you in the face; they condemn you. You feel your guilt—not a light and trifling fault, but guilt deep and dark, such as creatures made in the image of God incur by rebellion against the blessed and holy Creator. The Holy Spirit has recited the divine law in your ears. Your consciences have heard that voice and echoed its condemnation. You desire to escape that divine displeasure; you desire to have the fires of guilt that burn in your consciences quenched. You cry out, ‘Men and brethren, what shall we do?’ The answer must be drawn from many parts of the Holy Scriptures.
“Understand, in the first place, that you are not to be saved by searching out some plan of salvation for yourselves. Ask for the old paths. ‘He that entereth not by the door, but climbeth up some other way, the same is a thief and a robber.’ ‘Other foundation can no man lay than that is laid.’ ‘There is but one name given under heaven among men by which we must be saved.’
“Understand also that it is useless to attempt to save yourselves by making yourselves righteous. You have tried, I doubt not, to make yourselves better. Perhaps you have resolved that you would not come to Christ till you can present yourselves in some degree worthy of his care. Have you succeeded in getting rid of your sins? Can you blot out your past sins? Can you erase the record which stands written in the book of remembrance on high? The law of God written in this Bible condemns you; God condemns you; you are condemned already for not believing in the name of God’s only begotten Son, the Lord Jesus from heaven. Can you change that condemnation by your feeble, fickle resolutions to reform? ‘Can the Ethiopian change his skin or the leopard his spots? thenmay ye also do good that are accustomed to do evil.’
“Be assured also that it does not belong to you to change your own hearts. ‘Ye must be born again;’ ‘except a man be born again he cannot see the kingdom of God.’ But that second birth comes not of blood, nor of the will of the flesh, nor of the will of man, but of God. ‘Ye must be born again, but ye must be born of the Spirit.’ Notice that the wordsavedis in the passive voice. Sinners do not save themselves; they must be saved by another; they must be saved by one able to save, by one almighty to save, from the wrath of God and from sin, by one able to do for those who trust in him all that they need to have done in order to make their salvation complete and glorious. Christ is able to do this. The crucified and risen Christ is exalted a Prince and Saviour, to give repentance and remission of sins. The word of God says, ‘To give,’ and he rejoices to give.
“On one point we must pause and dwell with special clearness. Every anxious sinner must not only feel his guilty and lost condition, but he should also thoroughly understand what he means when he asks what he must do to be saved.He should see to it that he wants that salvation which Jesus gives.
“In the Scriptures the sinner who would be saved is called upon to return to God. He has gone astray. He must retrace his steps. What is meant by this? I mean that man’s sin consisted at first and consists to-day in saying, ‘I will,’ and ‘I will not,’ in opposition to the will and command of God. God said, ‘Thou shalt not;’ man said, ‘I will.’ God says, ‘Thou shalt;’ sinners say, ‘I will not.’ If a sinner is to be saved from sin, this opposition must cease. When God says, ‘Thou shalt not,’ the sinner must reply, ‘I will not,’ and when God says, ‘Thou shalt,’ the sinner must answer, ‘I will.’ The sinner’s ‘will’ and ‘will not’ must agree with God’s ‘shall’ and ‘shall not.’ In place of your self-will you must put God’s will; that is, repentance, a turning about, a returning to God. But remember, salvation, if it be real and thorough, is not submission for an hour, a day, or a year, but submission for ever and ever. It is submission without condition and without limits.
“The sinner says, ‘This is a hard saying,’ this utter and boundless denial of self-will and selfishness. But is it hard that the creature shouldyield to the Creator, that ignorance should yield to wisdom, that selfishness should yield to love, that sin should yield to holiness, that poor, lost, wretched, fallen man should yield to the eternal and ever-blessed God? It is only by yielding that his will is brought into sweet harmony with the will of God, and that he can be a sharer of the divine blessedness.
“Your views on this point should be clear and distinct. If you wish only to be saved from the penalty of your sins, you do not desire the salvation which Jesus gives. He saves his people, not in their sins, but from their sins. If, however, you really wish for his full and glorious salvation, you will desire that your will may be wholly subdued to the will of God. You will be found ready to unite in the memorable prayer of the Lord Jesus, ‘Not my will but thine be done.’ Salvation implies the giving up of self-will and a reverent submission to the will of God.
“Other sinful passions oppose the grace of God, but chiefly as helpers and supporters of self-will. Pride and vanity strengthen self-will. Turbulent fleshly lusts urge on and back up self-will. Fear of man, fear of danger, andunbelief are but props of self-will. When ‘my Lord Will-be-will’ submits, the town of Mansoul returns to her rightful allegiance.
“The question at issue between God and the sinner, the question of self-will or submission, is often contested around the performance of some single definite duty. The Holy Spirit often presents to the convicted sinner’s conscience some single duty and presses its performance. That duty is a test of the feelings and desires of the sinner’s heart. So the Spirit understands it, so the sinner often understands it. As, in the garden of Eden, God gave to Adam a test command, so does he now press upon the conscience of convicted sinners test duties to show them what they are. That which is required may be important, exceedingly important, in and of itself, or it may be in itself of very little consequence, but in every case the duty is all-important and its performance absolutely essential, because the Spirit has laid it upon the sinner’s conscience. It will show whether he wishes for salvation from sin or not.
“I used to hear a Christian relate an experience like this. While the Spirit of God was striving with him and conviction of sinwas heavy upon him, he felt a clear impression that he ought to go to his barn, and there at one certain place upon the hay-mow kneel and pray. His self-will rose in rebellion, chiefly, it would seem, because it was laid upon his conscience as a duty. But his distress grew upon him. He went to his barn and stood at another place and tried to pray, but no light or peace came; his sense of his sins grew heavier. How could it be otherwise? He went to the spot where he thought that he ought to go, and stood and prayed. Still no peace came, but increasing sense of sin. At length he thought, ‘Why should I not? Why not give up my own will? Why not pray that God’s will may be done?’ He yielded, he kneeled at the place where he had thought he ought to kneel, and there he first felt peace before God. This was a singular experience. Perhaps a man more intelligent and better taught in the Sacred Scriptures would never have such a thing pressed upon his conscience. But the battle of self-will is commonly fought around some single definite duty. That duty may be a confession of wrong done to a neighbor, or conversation with an impenitent associate, or a public confession of sin before thegreat congregation. Whatever it may be, it shows the sinner his heart and leads him to decide to follow his own will just as he had always been accustomed to do, or it will lead him to pray earnestly that he may be enabled in everything to bow his will to the will of God. He will want the full salvation which Jesus in his grace brings men—salvation from the penalty of sin and deliverance from its power.
“I draw no bow at a venture and speak not doubtfully when I say some of you are standing face to face with duties pressed upon you by the Holy Spirit. Your self-will, supported by pride, and fear of man, and unbelief, and Satanic temptation, refuses to yield. The yoke of Christ seems to you like bondage. The cross is supremely heavy. You draw back from it, and refuse to bear it. I cannot take away the cross which the Spirit bids you bear. I dare not do it; I will not do it. As the messenger of Christ, I repeat the voice of the Spirit and lay the duty, whatsoever it may be, upon your consciences. Do you really and honestly wish to be saved from sin? Then you will yield to the Spirit’s kind and gracious movings; you will yield humbly but heartily. If, however, you wantsomething else than the salvation which Jesus gives, what can you expect but perplexity, difficulty, darkness? I beseech of you, deal truly and faithfully with yourselves on this point.
“To those who wish really to be saved I have good news to proclaim. There is a Saviour such as you need. Trust in Jesus as your Saviour. Place the whole work of your salvation in his gracious hands. Christ saves sinners just such as you are. The faith which you are but to exercise is nothing else than your confidence, by which you entrust yourselves to him. Faith has no saving virtue in itself, but it is the hand by which the sinner takes hold of Christ. With this duty few of you will have any great difficulty. When once you wish to be saved from sin and are ready to submit to the will of Christ, you will have no reluctance to take him for your Saviour. You believe that Christ is a divine Saviour. If saved at all, you expect to be saved by him who died on Calvary. Hardly for the world would you resign your opportunity of coming to Christ and receiving his grace. You believe that Jesus is the Christ, the Son of the living God, the great sacrifice for sin. It remains that you should gladly accept what heoffers and follow him as loving, trusting disciples.
“Follow the Spirit, and you will be led to Jesus and will come speedily to the joy of salvation; resist the Spirit, and you grope in boundless darkness and fall upon the dark mountains.
“In the Holy Scriptures the question of the text is asked and answered many times. Hardly any two answers are alike. Are there different conditions and different duties required of different men? By no means. But the Holy Spirit adapted the answer to the different spiritual states of the various inquirers. The answer is made to each questioner’s heart. A self-righteous young man came to Jesus asking, ‘Good Master, what good thing shall I do that I may inherit everlasting life?’ Jesus answered, ‘Keep the commandments: thou shalt do no murder; thou shalt not commit adultery; thou shalt not steal; thou shalt not bear false witness; honor thy father and thy mother; and thou shalt love thy neighbor as thyself.’ The young man answered, ‘All these have I kept from my youth up; what lack I yet?’ Jesus said, ‘If thou wilt be perfect, go sell that thou hast, and give to the poor, and thou shalt have treasure in heaven, andcome, follow me.’ The young man went away sorrowful. Jesus knew his self-righteousness, and gave him answers which opened that young man’s eyes to see himself. He gave him a test command, and the young man’s revulsion from that duty showed that, notwithstanding his self-confident claim to righteousness, his riches filled all his heart. If your hearts are filled with the love of the world, you must put your possessions out of your hearts and follow Jesus.
“Nicodemus also came making the same inquiry. He must have asked something like this, for Jesus answered such a question. ‘Ye must be born again; ye must be born of the Spirit,’ said Jesus. Nicodemus was looking for a legal salvation by outward formal services, but Christ gave him to understand that salvation involves a great spiritual renovation wrought by the Holy Spirit, by which men old in sin become new creatures and enter the kingdom of God as little children. He taught him thus that salvation was only from God. If any of you are looking for a cloak of self-righteous religious duties which you can put on, be assured that true religion springs from a work of God wrought in the heart. You must be born again by thepower of the Holy Spirit. You must become new creatures in Christ Jesus.
“On the day of Pentecost the great company of men ‘out of every country under the whole heaven,’ while listening to Peter’s pungent address, cried out, ‘Men and brethren, what shall we do?’ ‘Repent and be baptized, every one of you, in the name of the Lord Jesus, for the remission of sins,’ answered Peter. Here were men who had a hand in crucifying Christ, or if they had no active share in that deed of darkness, they had consented to his death; they were partakers of the crime; very likely they had cried, ‘Crucify him, crucify him.’ They saw their sin, and were pricked in the heart. Well might they repent of their rejection and crucifixion of their promised Saviour, the Son of God, from heaven. Others were devout men who had come to Jerusalem to worship. Like Simeon they may have waited long for the consolation of Israel. How easy for them to enroll themselves among the followers of Christ! All alike are commanded after repentance to put on Christ by baptism. That burial with Christ was the symbol of their dying and living again—of their dying unto sin and living again unto God. Thesame duties are enjoined upon you. Repent of your long rejection of the grace of God and his Son Jesus Christ, and before God and men devote yourselves to his service by a public confession of Christ in baptism.
“The jailer of Philippi was taken in the midst of his sins. He was holding the servants of Christ in his dungeon. He knew for what offence they had been seized, and he made himself a partner in the crime of persecuting them by the zest with which he thrust them into the inner prison and made their feet fast in the stocks. His conscience was ill at ease. Then came the earthquake’s shock, and he felt as if called to stand face to face with his Judge. His soul was pierced through and through with a sense of guilt. ‘What must I do to be saved?’ he cried in the bitterness of his conviction. ‘Believe on the Lord Jesus Christ, and thou shalt be saved,’ answered Paul. This is the answer to all of you who are well convicted of sin and have given up all self-righteous hopes. Christ saves you. Look to Christ, ask Christ; whosoever comes to him he will in no wise cast out. Will you not come to him? Will you not trust his promises and commit yourselves to hishands to be saved? He waits to bless you. He delights to be gracious. To save sinners he lived among men, and died and has ascended. His hands are full of gifts. He comes to you, and stands and knocks at the door of your hearts. Will you bolt the door? There is joy in heaven over repenting sinners. This alone of all earthly transactions carries joy to Christ and the angels. Accept of Christ, and earth and heaven will throb with a common joy.”
These words were listened to with most earnest attention, for at that time Christ and heaven were realities in the minds of men, and salvation was a living issue. Mr. Wilton spoke as an earnest man, without cant or circumlocution, pressing upon men of thought and conscience the great concerns of eternity. The full result of this discourse will be known only when the opening of the books at the last day shall reveal it, but the beginning of the result was seen in the evening prayer-meeting. When the invitation was given for anxious persons to make known their feelings, both Ansel and Peter arose, and confessing in few words that the Spirit of God had been striving with them,and that they had been resisting the Spirit, said that now they were determined to resist no more, and asked Christians to pray for them that they might be able to submit fully to the Lord Jesus and trust entirely in him. Then there was a pause. Mr. Wilton was just on the point of rising to close the meeting when Mr. Hume rose to his feet. After a sudden start of surprise, a deep hush passed over the congregation, and in the midst of deepest silence Mr. Hume said:
“I have been more than merely an impenitent man: I have been an unbeliever; I have been an infidel. I have not only tried to disbelieve the Holy Scripture, but I have actually disbelieved. I have thought myself wiser than the word of God. I do not mean that I have enjoyed peace, that my conscience has been at rest, and that I have been happy in my unbelief. Three months ago I began to grow more than usually discontented with myself. Questions which I counted settled and put to rest for ever came back to trouble me. A hundred times a day the questions came, What if there be a God who holds me responsible? What if there be a future life and a judgmentday? What if Christ be the Son of God? Why such questions should haunt me day and night I could not tell. I have learned to believe that the Spirit of God was speaking to me. This restlessness brought me to the church for half a day. If my object was to gain rest in unbelief, I could not have done worse. My old arguments were unavailing to break the force of the truths preached. The questions which had been sounding in my ears and echoing in my heart began to change to solemn affirmations: ‘There is a God;’ ‘There is a day of judgment;’ ‘Appointed unto man once to die, and after that the judgment;’ ‘Christ is risen.’ Texts of Scripture learned in my boyhood and forgotten long years ago came back fresh to my memory. But I will not stop to rehearse to you all my struggles of mind for two months past. For a few weeks you have seen me here. I determined that I would try to find Christ if he manifests himself to men in these latter days. For two weeks I have tried to pray, but I have found no satisfaction. Christ has not manifested himself. My darkness has grown deeper and deeper. I have sometimes almost determined to abandon all thought of Christ and throwmyself back again upon my former unbelief. But I could not lay down the subject.
“Since I began to try to pray I have felt, faintly at first, like the whisper of a suggestion, but becoming clearer and stronger, like a voice from heaven, that I must in this congregation confess my former state and the feelings which I have had. It seemed to me that I could not do this. It seemed easier to die than to stand up here and confess that my belief, which I had pressed upon others and had boasted of as better than the gospel, had given me no peace. To-day I have been made to understand that the Spirit of God has set me face to face with this confession. I have seen what it means to be saved—that my self-will must die or I must bid adieu to Christ and hope. I cannot live and die hopeless. I cannot rest my head upon unbelief. I confess to you that all my thoughts have been wrong. My beliefs and my unbelief have done me no good. My whole life has been enmity and opposition to the Holy Spirit. I will try to oppose the Spirit no more. I know not what the Spirit may lay upon me, I know not how soon I may break my resolution, but I now feel that I want to be saved from sin, andcannot do otherwise than follow the Spirit though I dwell in darkness for ever. If Christ reject me I cannot complain, but if you think there is hope for one who has so despised the grace of God, I entreat you to pray for me.”
It is needless to say that from scores of family altars and closets supplications went up to God that night for the salvation of Mr. Hume and Ansel and Peter, and men prayed especially that Mr. Hume, who for years had been such a tower of strength to the ungodly and the dread of Christians, might be saved for the glory of Christ and the confounding of unbelievers. Those prayers were heard. When the report of that meeting and that confession went out through the community, unbelievers were silent. It was as if the God of battles had emptied his quiver into the hearts of his enemies.
TRANSFER OF HEAT IN SPACE.
We now turn our attention,” said Mr. Wilton, “to a new theme. In the vicissitudes of day and night and of summer and winter heat is transferredin time. We now are to look at the arrangements by which heat is transferredin space. But since the transfer of heat in space requires more or less of time, the means employed are such as suffice to accomplish both objects. Heat is treasured up and carried away to distant regions, and delivered up for use as occasion demands.
“In a previous lesson the inclination of the earth’s axis was spoken of. By this means the northern hemisphere of the earth is turned somewhat toward the sun during one half of the year, and receives a correspondingly larger portion of heat, while during the other half of the year the southern hemisphere is turned towardthe sun and is warmed. This inclination of the earth’s axis to the plane of its orbit gives us the change of seasons.
“The change of seasons is manifestly designed for the welfare of man. Along with the genial warmth of summer, fruits and grains and the comforts of life are carried far toward the poles, into regions which otherwise would be desolate with perpetual frost. But these extremes need to be softened; otherwise, the violence of the changes would prove destructive rather than beneficent. The severity of these annual changes of temperature is ameliorated by some of the grandest movements and arrangements upon our globe. These arrangements we have in a very imperfect way already examined.
“But there are other inequalities of temperature besides those of day and night, summer and winter. Passing from the equator toward the poles, every degree of the earth’s surface passed over causes the sun to sink one degree from the zenith toward the horizon, and gives a corresponding lower temperature, till within the polar circles for a part of the year the sun is entirely hidden and winter reigns without a rival. The temperature of the sea differs fromthe temperature of the land; the sun comes nearer to one hemisphere than the other, and remains longer north of the equator than south. These and many other differences upon the earth give to different parts of the world every possible variety of temperature and climate. These differences of temperature upon sea and land, from zone to zone and from hemisphere to hemisphere, are equalized or ameliorated by many agencies, but chiefly by a transfer of heat in space, a transfer of heat from place to place.
“I do not need to tell you that while we in the northern hemisphere are enjoying the warmth of summer the southern hemisphere is enduring the severities of winter, and in turn, when winter comes to us, summer smiles upon the nations that live south of the equator. You also remember that the orbit of the earth is not an exact circle, but an ellipse, that is, what is sometimes called in common language a long circle. For this reason the earth is three millions of miles nearer the sun in one part of its orbit than when in another part. Can you tell us, Peter, at what season of year the earth is nearer the sun?”
“In midwinter, or about the first of January.I have always remembered it because it seemed so strange to me, when I learned it, that the sun should be nearest the earth at the coldest season of the year.”
“Yes, one is reminded by it of the humorous argument that the sun must emit cold instead of heat, because when we are at the point of the earth’s orbit which is nearest the sun it is winter, and the higher one ascends upon mountains toward the sun, the colder he finds it. But this nearness of the sun while south of the equator would naturally give the southern hemisphere a warmer summer than the northern. For this there is a beautiful compensation. The earth passes through her orbit more rapidly when nearer the sun, and that half of her orbit is also smaller, so that, as the result of this, the sun remains north of the equator about eight days longer than in the southern hemisphere. The sun is nearer while in the southern hemisphere, but the summer is shorter. That which the southern hemisphere gains in distance it loses in time, and that which the northern loses in distance it gains in time.
“The nearness of the sun while south of the equator, the shortness of the summer, and thecorresponding distance of the sun and length of the winter would tend to give the southern hemisphere great extremes of heat and cold, a short and hot summer and a long and cold winter. For this also there is a most interesting compensation in the comparative amount of land and water north and south of the equator. Much more than one-half of the dry land lies in the northern hemisphere. This would tend to give the northern hemisphere extremes of heat and cold. South of the equator there is comparatively little land and much water, which tends to give the southern hemisphere evenness of temperature. The inequalities of the earth’s orbit and the earth’s motion in its orbit we find counterbalanced by the arrangement of land and water upon the earth’s surface.
“In connection with this we may notice still another compensation in the elevation of the lands by which the burning heat of the torrid zone and the rigors of the colder zones are more or less diminished. The greater the elevation of any region of country, the cooler must be its climate. Physical geographers like Baron von Humboldt and Guyot have made calculationswhich show that those grand divisions of the earth which lie in the hot regions of the earth are most elevated above the sea level. South America lies higher than North America, Asia is more elevated than Europe, and Africa is more elevated than Asia. The continents rise as they approach the equator and sink toward the sea level as they come nearer the poles. As these colder lands approach the water level their valleys sink beneath the sea, their coast lines become deeply indented with bays and gulfs, and lakes abound. Thus the warmer waters of the sea are interspersed among the cooler lands, and the temperature of the lands is raised. The very elevation of the continents and the configuration of the lands have a providential relation to the temperature and climate of the world. We cannot suppose that arrangements like these, so aptly fitted to the needs of man, came by chance. In the unmeasured ages past, while this earth was in preparation for man, God had the beneficentendin view; nay, in the very beginning, the whole plan and its beautiful completion was had clearly in mind. Millions of ages ago the great Creator tenderly considered the comfort and well-being of thehuman race, the latest born of his creatures, in these last ages.
“As a general statement, the torrid zone receives an excess of heat, while the frigid zones receive too little, and the temperate zones, lying between, receive, at different times and places, sometimes too little and sometimes too much. The providential arrangements for equalizing temperature are, then, chiefly arrangements for conveying heat from the overheated tropical regions and scattering it over the temperate and polar regions. First among these means we will notice thetrade-winds, or, as for the sake of brevity they are often called, ‘the trades.’ Will you tell us, Samuel, how winds are caused?”
“The air is heated at some place and expands; it becomes lighter and rises, while the colder air around rushes in to fill its place.”
“You use the words which are commonly employed in explaining the origin of winds, and very likely your idea is right, but the language needs a little correction. The warm air does not rise of its own accord, so to speak, but is pressed upward. The warm air is expanded; it presses outward and upward; the same weight of warm air occupies more space than cold air;the warm air rises and overtops the surrounding air, and then flows off in order to reach the common level. The column of warm air is lighter than the cooler air, and cannot balance it; consequently, the cold air sinks down, pressing the warm air upward. In this manner an ascending current of warm air is formed, and also currents of cold air flowing from every direction toward the warm centre. These currents continue until the temperature of the air is equalized.
“The atmosphere is commonly believed to be forty-five or fifty miles in height, though some men have estimated its height as very much less than this, while others believe it to be six or seven hundred miles in height. Are we to suppose that the column of heated air reaches to the top of the atmosphere?”
“I think not,” answered Mr. Hume. “The rarefaction of the lower part of the column renders the whole column lighter than the air around, and the warm air, as we know by the movements of the clouds, after rising a little way, spreads off in every direction, forming upper currents corresponding to the currents below, but moving in the opposite direction.”
“Only a few days ago,” remarked Peter, “I saw in the same part of the sky clouds moving in exactly opposite directions, and others which seemed to be standing still. I knew how one layer of clouds might be moving north and another layer moving south, but I did not understand why some should be standing still.”
“Do you imagine, Peter, that the upper and lower currents of air, moving in opposite directions, come sharply together, the one sliding against the other?”
“I think not,” said Peter.
“Supposing, then, as is certainly true, that a stratum of still air lies between the upper and lower winds, does not that explain how certain clouds might be standing still while the others were moving?”
“I might have thought of that myself.”
“But how does this carry heat from the warmer region to the colder regions around?” asked Ansel. “I see how the colder air coming in would cool the warm region, and how the warm ascending air would carry away the excess of heat, but how do the cooler regions get the advantage of this heat?”
“That is just what I was on the point ofexplaining. Do you remember what was said about the production of cold by expansion and of heat by compression?”
“I remember that if air be rarefied by removing pressure from it, its temperature falls: I think you said that a part of its sensible heat becomes latent; and if air be compressed, its temperature rises. I have seen experiments with the air pump and condenser to prove this.”
“That principle explains the transfer of heat by winds. If the heated air rose to the upper regions, and there radiated its heat, nothing would be gained; the heat would be simply radiated into space. But as the warm air rises pressure is more and more removed from it; it expands; its sensible heat becomes latent and is thus kept from radiation; its temperature falls, but not from loss of heat. This rarefied air forms the upper current flowing away from the heated centre. In due time this air must come to the surface of the earth again. Whenever this takes place the air is brought again under pressure; it is compressed, and its latent heat becomes again sensible. Heat is thus transferred from the warmer region to the colder in a latentcondition, so that it cannot be lost. We must now apply this to the trade-winds. What are the trade-winds, Mr. Hume?”
“They are regular winds blowing from a little north and south of the tropics of Cancer and Capricorn south-west and north-west toward the equator.”
“These winds are calledtrade-winds,” continued Mr. Wilton, “on account of their great advantage to trade or commerce. The regular and steady sweep of these winds bears the merchantmen rapidly and safely on their way. The formation of ‘the trades’ is easily explained. By the intense heat of the sun under the equator the air is greatly expanded and rarefied; the heated air rises along the whole line of the equator; from both sides the cooler air presses in, is heated, and rises; thus steady winds are formed from the tropics, or a little beyond the tropics, toward the equator. If the earth had no rotation upon its axis, these winds would blow directly toward the equator, exactly south and north. The rotation of the earth gives the trade-winds their oblique, south-west and north-west direction. Suppose that a single particle of air at the tropic of Cancer starts upon its journey toward theequator. At its starting it has the same motion eastward as the surface of the earth at that place, that is, about nine hundred and fifty miles per hour. But as it moves on southward the degrees of longitude become longer and the motion of the earth’s surface becomes more rapid, till at the equator its motion is one thousand and forty miles per hour. But the particle of air we are watching is not fastened to the earth’s surface, and as the earth moves more rapidly the nearer we come to the equator, the particle of air falls behind, that is, the air moves southward and eastward, but the earth moves eastward more rapidly than the air, so that the air falls behind and seems to be moving westward. The result is that the air upon the earth’s surface moves south-west. That which takes place with a single particle takes place with the whole body of the air, and that which takes place north of the equator takes place south of it also, producing north-west winds. On reaching the equator the winds from the north and the south meet and stop, forming the equatorial calms, and mingling together, they rise into the higher regions. In rising, the air bears away heat from the torrid zone, and this heat, rendered latent by the expansion of the air,is carried north and south by the upper currents as far as the limits of ‘the trades.’ In due time these upper currents descend and their latent becomes sensible heat, and is used in raising the temperature. Mr. Hume, can you suggest any method by which we can estimate the amount of heat which is carried north and south by the return trades?”
“I know of no method, except to estimate the amount of heat necessary to raise that flood of air which pours in from the temperate zones to the equatorial heat. That immense amount of heat must, nearly all of it, be carried away to the temperate regions.”
“This is the general explanation of the trade-winds. You must understand, however, that, in certain regions and under certain conditions, the trades are liable to interruption or change of direction. Desert regions within or near the tropics give rise to local winds which overpower the trades. In Southern Asia, while the sun is north of the equator, the land becomes so much hotter than the sea under the equator that the trade-wind is overpowered and reversed, forming a wind which blows to the north-east instead of the south-west. But this is only a beautifulflexure, so to speak, of a general arrangement for the greater advantage of a particular region. By this means the summer winds of Southern Asia come from the sea. Northern winds would have been dry. Prevailing northern winds would have made the whole of Southern Asia a desert; but the south-west monsoons come from the Indian Ocean laden with vapor, and render Southern Asia a very garden for fertility.
“The next great agency for equalizing temperature between the torrid and temperature zones is the formation and condensation of vapor. This comes in here, because it depends for its efficiency upon the agency of winds. More than once this method of conveying heat from place to place has been hinted at, but deferred till we came to the proper place to speak of winds.
“The trade-winds, passing over from a colder to a warmer climate, are constantly accumulating vapor. Under the equator the annual evaporation from the surface of the ocean is set down at fifteen feet, or half an inch daily. The formation of this vapor consumes heat which would boil more than eighty feet of ice water. The vapor thus formed is borneupward by the ascending current of heated air. On reaching the higher regions a portion of it is condensed and forms a belt of clouds around the earth. This belt of clouds along the equator is known as the ‘cloud-ring.’ This cloud-ring shields the belt of calms from the burning rays of the sun and sends down almost incessant rains. But does not that condensation which forms the cloud-ring set free latent heat, and thus intensify the great heat of the equator? Latent heat becomes sensible, but it is given out into the ascending current of air, and serves only to give it another lift till by expansion of the air it again becomes latent. The heat is simply transferred from the vapor to the air. The vapor which remains uncondensed is borne away on the wings of the return ‘trades’ to the south and to the north, and in due time is condensed and returns to the earth as rain; the heat which is given out by its condensation, wherever and whenever it is condensed, is given over as latent heat to the keeping of the air, and is passed back for use whenever the air descends to the earth.
“Vapor gathered from sea or land is everywhere exerting this equalizing influence upontemperature. Does the temperature rise in any place? Vapor is formed. Every moist body begins to give up its moisture, and the excess of heat is employed in turning this water into vapor. This is the method by which perspiration cools man or beast; whether it be insensible perspiration from the invisible pores of the skin, or perspiration standing in beady drops upon the face of the toiling laborer, vapor is formed and heat is carried away. Have you not noticed on close, muggy days when nothing dries, showing that very little vapor is forming, that perspiration seems to have no cooling effect? It oozes from the skin, but does not evaporate, and hence does not carry off the surplus heat. Animals like dogs and oxen, that do not become wet with perspiration, do not bear heat well; they soon pant and loll, attempting to get rid of the excessive heat through the moist breath and open mouth.
“The sum-total of heat transferred by this agency is too great for comprehension. Look at the Amazon rolling to the ocean a flood broad as an arm of the sea. That great river is brought from the Atlantic Ocean on the shoulders of the trade-wind. As the vapor is slowly lifted by therise of the land from the sea level to the summits of the Andes, it is condensed, and falls as rain. Well is it for South America that the Andes were thrown up on the western coast, for the winds west of the mountains are dry as a pressed sponge, and the most of that narrow slope is barren and desolate. South America would be a desert if the Andes ran along the eastern coast. Look at the Mississippi, and the great rivers of Europe, and the matchless rivers of Southern Asia. All the rivers of the world represent only thewastageof the rain which falls upon the land after supplying the wants of the vegetable kingdom and keeping the lands moist. All this water is lifted into the air by heat, and every movement of vapor is a movement of heat. Every particle of vapor goes freighted with heat. Every cloud driven across the sky represents the transfer of heat, and every transfer is in the direction of equalization. Everywhere the tendency is to equilibrium. Nature has no processes for transferring heat from colder to warmer regions.
“We may form a conception of the amount of heat transferred by the agency of vapor by estimating the amount of heat-force required toevaporate the water which forms our rain-clouds and lift them into the upper regions. According to a calculation of Mr. Allen, late of Providence, to evaporate one-eighth of an inch of water daily from that belt of the surface of the earth lying within the tropics, and raise it five thousand feet high, requires 4,700,000,000 horse-power, or one hundred and thirty times the effective force of the whole human race, reckoning it at 250,000,000 able-bodied men. But the actual evaporation from the sea within the tropics is believed to be about half an inch daily—four times as great as Mr. Allen’s supposition.
“I see, however, that our time is nearly exhausted, and I wish before closing to revert to that more important theme upon which I spoke this forenoon. I do not know how the truths preached interested or affected you, nor do I now wish to have you tell me. I wish only to say that, as the sermon was preached at your request, I hope it proved applicable to you, and that you will give the truths presented earnest attention. Consider them well, and make your conclusions known this evening.”
The conclusion which the evening made known, you, reader, have already learned.