Asia. It is difficult to determine in what part of Asia the highest temperature occurs, as data from many parts are meager. It is known however that extremely hot weather prevails in India and Arabia. Siberia, however, experiences the coldest weather to be found anywhere in the world. At Werchojansk, in that country, a temperature of 90.4° below zero was observed in January, 1884, while the average temperature for the whole month was 69.4° below zero.
The coldest weather of the world is not found at the North or the South Pole, as many suppose, but rather at the center of vast continents, far from the modifying influence of oceans.
Australia. In extreme heat the interior of Australia is fairly comparable with northern Africa, Persia, Afghanistan, and northern India, where every year maximum temperatures of 115° occur, and where, at times, an extreme heat of 120° or 125° is experienced in the shade.
We now know that the forceful, dominating peoples come out of the regions where the heat is not so great as to debilitate, nor the cold so fierce as to deaden the mental and the physical faculties; but rather from the region of the thoroughfare of the great circum-polar storm tracks, where there are frequent changes of weather from sunshine to clouds, and where there is a fairly wide difference in temperature between night and day and between winter and summer. For the best coördination of the mental and the physical faculties, so as to produce the most efficient composite of man, the temperature should range between 45° and 50° at night and between 65° and 70° during the day, with about sixty-five to seventy per cent. of relative humidity. Some day we will artificially create the exact conditions of temperature and moisture needed for patients in hospitals and sanitaria. Science is persistently seeking means to increase comfort and prolong life.
CHAPTER XV
CONDENSATION
HOW HAZE, RAIN, SNOW, HAIL, FROST, CLOUD, AND FOG ARE FORMED
Haze is what might be called diluted cloud or fog; it differs from them only in the degree of its density. One may see several miles through a haze, because the minute particles of spheres of water or ice are far apart in comparison to what they are in fog or cloud.
Raindrops vary in size from O.03 to O.20 of an inch in diameter. Each drop is composed of literally millions of minute specks of water that have condensed each about a minute mote of dust. These motes are a million of times below anything that may be seen with the most powerful microscope. Recall what is said in [Chapter IV] about the size of the molecules in water: if a raindrop were enlarged to the size of the earth, the molecules of which it is composed would be no larger than a baseball, and the smallest of them no larger than tiny green peas. Without free surfaces upon which condensation may begin there can be no rainfall. Dust motes furnish these surfaces; without them air may be supersaturated without condensation occurring except where it comes in contact with solid matter. The little spherical masses of water join together so as to form raindrops in some manner not well understood. When enough of them coalesce so that the weight of the drop is too heavy to be supported by the motions of the air it falls to the ground, or is evaporated by the warmer and drier lower air. Raindrops form mainly in the stratum between one and three miles above the earth. It is seldom that the stratum of air next the earth is saturated, even during rainfall. One might evaporate millions of gallons of water and find no dust as a residue, or at least nothing visible to the human eye, so infinitesimal are the motes of condensation. As high as thirty millions have been shown to exist in a single cubic centimeter of air ([Chapter IV]), and a million times that number could occupy such space without being visible, and the dust mote is composed of molecules, and the molecules of atoms. It is impossible for the human mind to grasp the idea of the degree of smallness to which the atom attains, and when one tries to conceive of the electrons from which the atom is built up, he must try to think of them not as objects but as the place or condition where matter slowly fades away into nothing; as the place possibly where matter is transmuted into electrical energy and ceases to exist.
The raindrop cannot be formed at great altitudes because the vaporous atmosphere is confined to low levels by temperature. At 100°, which often exists at the bottom of the atmosphere, air at saturation contains 19.77 grains the cubic foot; at 80°, 10.93; at zero, .04; and at -40°, which always may be found at about four and one half miles high, air cannot contain in excess of .01 of a grain. Raindrops are mainly caused by the cooling of air down to its dew point.