"You will keep in mind that this supply of heat is also a supply of mechanical force. The coal-fields are an exhaustless storehouse of heat and power. They warm the dwellings of man and drive millions of engines working with the strength of Titans for human welfare. "In this bountiful supply of heat to warm the earth and serve human needs must we not see a kind design on the part of the Creator? God has provided that which the world needs. He has provided without stint or limit. The general heating of the globe he accomplishes by his own power. He has provided for human culture, development, and happiness by placing stores of heat under man's control. He has furnished scope and means and encouragement for achieving greatness and goodness. He has put man in the condition which a wise father would desire for his son. "In our next lesson we will look at the preservation and distribution of heat, some of the primary elements and arrangements upon which the temperature of the earth depends." CHAPTER VII. PRESERVATION AND DISTRIBUTION OF HEAT. Another Lord's Day comes, and the members of the class are, as usual, all in their places. They find the subject increasing in interest after leaving the review of the laws and principles of heat. "A week ago," said Mr. Wilton, "we looked at the chief sources of heat. These are the sun, the internal heat of the earth, chemical action, in which combustion is most important, electrical action, and mechanical action, or 'living force.' The amount of heat furnished from these sources is above all comprehension. The Creator seems bountiful even to prodigality in supplying heat for the needs of the world and the uses of man. But with all this largeness of supply the provision would prove wholly inadequate if it were not prudently husbanded and all the avenues of waste carefully closed. Men of ample incomes sometimes come to want from too free expenditure. Their incomes are large, but their expenses are larger. So it would prove in respect to heat if Nature were not as prudent in saving as she is bountiful in providing. Will some one mention some of the general methods by which the waste of heat is prevented?" No one answered. Mr. Hume did not think it best to put himself forward in answering questions, and therefore answered only when personally addressed. The others were silent because they had nothing to say. "I see that I shall have to suggest the answer. Ansel, what part of the atmosphere is warmest?" "The bottom, I suppose, for the higher a man goes up upon the lofty mountains or in a balloon, the colder he finds the air."