Curiosities of Heat

al, all in their places. They find the subject increasing in inte

hension. 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

rd in answering questions, and therefore answered only when personal

gest the answer. Ansel, what pa

man goes up upon the lofty mountains or i

the polar regions the line of perpetual freezing comes down to the sea level. What would be the effect, Ansel, if the atmosphere

h. With the temperature twenty or fifty or seventy d

ce suggested. The atmosphere is diathermic, that is, it permits the luminous heat from the sun to pass directly through it without heating the air, but the solid earth stops the heat by absorption, and is warmed by it. The warm surface of the earth imparts, in turn, its heat to the atmosphere resting upon it. This warm air, being expanded by the heat received, becomes lighter than the cold air around, and rises, or rath

in Providence, R. I. The day was bleak and chilly, and the sky entirely covered with clouds. The aeronauts were expecting a chilly voyage. The balloon shot like an arrow toward the zenith, and in five minutes was completely hidden by

the snow or ice remaining still frozen at a little distance, as if the sticks and straws were warm and had melted them? Have you not seen a dark-colored boa

t many times," said Peter, "and

ard, the heat is absorbed, the dark body is heated and in turn warms and melts the ice. In the same manner the atmosphere is warmed. The heat-ra

ark heat almost completely. In a smaller degree watery vapor does the same. Gases and vapors thus serve as blankets to keep the earth warm. The heat of the sun, being luminous heat, penetrates the atmosphere with its vapors and foreign gases, and falls upon the earth almost without loss, but, being absorbed b

their efficiency is no less admirable than their simplicity. Arrangements like these show that the Creator had a definite object in

we could fly like a bird from the equator to the poles, and look down upon the ever-changing animal and vegetable life as we pass! How the luxuriant vegetation and flaunting colors of the tropics would shade off into the scantier vegetable life and more sober hues of the temperate zones, and these in turn die out and disappear in polar barrenness! We should see the lion and tiger give place to the bear and the wolf, the elephant and camel to the ox and horse, and these to the white bear and reindeer. This sublime p

lly disastrous. Man indeed transfers animals from their natural habitat by protecting them from the extremes of temperature, but this is, of course, no exception to the general principle of which I am speaking. A change of only a few degrees in the mean annual temperature wo

I think upon the inten

mportant, for if the intensity of the sun's heat were doubled, the temperature of the earth would be increased only twofold; whereas, if the earth were brought to one-half its present distance from the sun, the heat would be increased four times. Heat being one of the radiant forces, its intensity diminishes in proportion to the square of the

upon our atmosphere. Can you tell us, Ansel, how the

sun to fall upon the earth almost undiminished in force. If the air were so constitute

sed. Simple gases are diathermic. The atmosphere is therefore made up of two simple gases, oxygen and nitrogen, not chemically combined, but mixed together. Compound gases intercept the passage of heat. Ammonia, composed of hydrogen and nitrogen chemically united, almost wholly stops it. Even oz

gen, vapor of sulphur were substituted? What if hydrogen were put in the place of nitrogen? The two elements would combine in sudden combustion or explosion, and the atmosphere itself would perish. But nitrogen is a substance so sluggish and inert that it can be brought into union with oxygen only

n certain qualities of the earth's surface. I

rom the solar heat. A dark soil absorbs heat more readily than a soil of lighter color, and a wet soil, on account of the high specific heat of water, requires more heat to raise its temperature than a dry soil. The mineral elements of the soil and its compactness or porosity also help to make up its capacity for receiving and retaining heat. The color and constitution of the soil sometimes go far toward mak

ubtlest 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 inha

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

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

I reach some satisfactory

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 onl

f the earth,

earth operate to produce i

urned toward the sun the rays fall perpendicularly, the sun is directly over head, while toward the edges of the hemisphere, on acc

temperature which is produce

ones," answ

edgewise to the fire. Upon the torrid zone the sun shines perpendicularly, upon the temperate zones obliquely, and upon the frigid zones still more obliquely, and during a part of the year the sun is entirely hidden. In proportion as the rays of heat fall obliquel

of the earth

along with the light. The heat of the sun is not withdrawn from the earth, but one-half of the earth's surface is constantly turned away from its influence. This must produce a daily

xis and the revolution of the earth aro

sun, while in the opposite part of the year the south pole is in like manner brought into the light and heat. This causes the sun to appear to move to and fro, north and south, twenty-three degrees, twenty-seven minutes, and twenty-three seconds from the equator in either direction. The tropics, or turning-places, mark the limits of the sun's northern and southern journey. Everywhere between the tropics the sun, at some period of the year, passes through the zenith, that is, exactly overhead at noon. North and south of the tropics the sun seems to rise higher in summer and to sink lower in winter. In summer the sun at midday

than south of it. Our summer, therefore, is eight days longer than the summer of the southern hemispheres, and our winters are correspondingly shorter. These differences tend, however, to balance each other, for while the southern

that the temperature is more even upon the se

s with heat more slowly than the land, and its absorption or radiation causes a smaller variation of temperature. The result is, therefore, that the sea is cooler in summer and warmer in winter than the land, and the average ocean temperature is lower than the mean continental temperature. The land receives heat more readily and parts with it more rapidly; the fluctuati

d upon mountains, th

mean elevation than another. One region or tract of country lies sloping toward the sun, another is inclined from it. The effect in the one case is the same as if the sun were brought more nearly overhead; in the other case, the sun is depressed tow

e portion of the earth's surface and shut out the heat of the

ny one think of another cause

the unmeasured cycles of the past, the gradual cooling

ress of the race, could hardly have been formed, and at the temperature of the carboniferous periods, when the coal-beds were deposited, the human race could with difficulty have survived. The h

helping the culture of men and nurturing the domestic virtues? We might almost say that her winter evenings have been the making of New England. But periods of heat are needed for bringing fruit and grain to ripeness. What variety and richness of productions for the use of man the different zones furnish! The supply of man's wants would be comparatively meagre if we had but one zone, even though we had our choice of the zones. But every zone is necessary for the perfection of the temperate zones. That we may have the warmth of summer in the temperate zones we must have the torrid zone. That we may have the tonic cold of the temperate zones we must needs have the severity of polar winters. I do not mean that the Creator could not devise a world that should not have these painful extremes, yet enjoy the advantages of the temperate regions. But that w