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 a[Pg 306] careless 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 serene
The 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 and[Pg 307] rebuild 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 the[Pg 308] region 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 as[Pg 309] force 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 the[Pg 310] air, 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.
[Pg 311]“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 to[Pg 312] solids, 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 ............