“Upon so many circumstances wisely adjusted and nicely blended,” said Mr. Wilton, “does the temperature of the earth depend. The intensity of the sun’s heat, the dimensions of the earth’s orbit, the constitution of our atmosphere in the subtlest qualities and relations of its elements, and the material, structure, and color of the earth’s crust,—on all these and many other things which I cannot stop to mention depends the temperature needful for the well-being of the inhabitants of this globe. I beg your pardon, Mr. Hume, but allow me to ask whether such a combination of agencies and conditions, uniting to work out good for man, does not seem to you quite superhuman and worthy of a wise and good Creator?”
“I cannot deny it, sir,” he replied; “I am not prepared to make any objections. There are many things painful to man in the vicissitudes of heat and cold, and if I were to make a world, I suppose I should leave them out, or perhaps make the world upon a very different plan. But I am not prepared to affirm that any changes which I could make would be improvements, though I have thought until recently that more of knowledge and power, and perhaps more of chance, too, than of wisdom and goodness, were displayed in the works of Nature. But I must confess my opinion has been much modified.”
“I think your change of mind is in the right direction, and I am glad that it is so. We learn the secrets of Nature and appreciate her spirit much better when we come as reverent questioners than when we come with preconceived notions and a patronizing air. I can well understand your feelings and state, for I myself have traveled over the same ground. My eyes were once dazzled with the glories of science; I worshiped at the shrine of natural laws. But I have learned that God is greater than Nature, the Creator is mightier than the creation. Nature has no mind or purpose apart from the plan and will of the supreme Architect and Ruler, and this inner plan and purpose of Nature is seen only in the government and discipline of our sinful race. I shall greatly rejoice for you and with you if you shall go on to the same end which I have reached.”
“I shall much rejoice if I reach some satisfactory and peaceful conclusion.”
“To understand the management of heat,” said Mr. Wilton, “we must take note of the differences and fluctuations of terrestrial temperature. The sources of heat are constant. The sun sends out its flood of heat uninterrupted and changeless for ever. The internal fires of the earth give an even inward heat. Mechanical and chemical agencies are active everywhere. These sources of heat do not fluctuate, flaming up and dying away, yet temperature is the most variable of all inconstant things. In passing from equator to pole we go from torrid to frigid, from everlasting summer to everlasting winter. And not only this, but in the same region the temperature never remains the same for even twenty-four hours. The thermometer may pass from forty degrees above to thirty below zero in a very few hours. We must first consider the agencies by which these inequalities are produced. Ansel may mention the first of these.”
“The shape of the earth,” said Ansel.
“How does the form of the earth operate to produce inequality of temperature?”
“The earth is a sphere, and the rays of the sun fall upon it in nearly parallel lines. Upon the centre of the hemisphere which is turned toward the sun the rays fall perpendicularly, the sun is directly over head, while toward the edges of the hemisphere, on account of the curvature of the earth’s surface, the rays fall more and more slanting, as if the sun were sinking toward the horizon.”
“What is that inequality of temperature which is produced by the shape of the earth?”
“The five zones,” answered Peter.