Jacques Wardlaw Redway

“ Matter may be changed in physical form, but it cannot be annihilated. Thus, the coal in the fire-box is changed to carbon dioxide, a gas, instead of a solid; but the chemist may separate the carbon from the oxygen. Nothing, not even the energy, is lost; to nature nothing can be added, and from nature nothing can be taken away.
Properties of Matter.—All forms of matter have certain properties—volume, density, weight, etc., in common. ”

“ When the sun’s warmth converts these to vapor the absorbed heat becomes latent heat, and no longer appears as sensible heat. This fact furnishes another reason why the air over desert regions, as well as the ground surface itself, becomes heated to a higher degree. [5]
Conditions of temperature exercise a great control, not only over civilization, but over the distribution of life itself. Humanity may overcome its environment so far as temperature is concerned—man can command fire, food, and fuel to be brought to him; but other forms of life cannot rise superior to conditions of temperature. ”

“ Within the storm area the winds acquire a spiral motion, whirling upward contra-clockwise as they approach the updraught. The whirl brings warm and moist air from a southerly region to the easterly side of the low, where the air is colder and the temperature nearer to the dew-point—that is, to condensation. For this reason, most of the precipitation is on the east and south sides of the low. On the west side colder and drier air is blowing from the west and the northwest and, being colder, is drawn into the updraught to a less extent or perhaps, not at all. ”

“ When a low is crossing the mountains it is in a region of dry air; therefore it does not possess much energy. When it has crossed the Rocky Mountains it is in a region where both the absolute and the relative humidity are greater. Therefore it is apt to develop a much greater energy; for the latent heat set free by the condensation of water vapor is the fuel of a cyclone. The northerly cyclone usually traverses the Great Lakes, where the increased humidity imparts greater precipitation, finally moving out into the Atlantic. As a rule, the rainfall of such storms is not very heavy. ”

“ Just as water, by seeking its own level, acquires an even and uniform pressure, so the electricity of the air seeks an even and uniform potential. If a body of cold, dry and highly charged air flows into a region of low potential, or into one oppositely charged, an interchange, or flow of electricity, results. ”

“ Local Winds.—The local winds of a region appeal to a community more forcibly than do the general movements. One may not appreciate the fact that the habitability of a region depends very largely upon the general movements of the air; but no one can fail to realize the importance of a hot blast, a blizzard, a tornado or a sand storm—or, indeed, of any occasional storm wind that may injure growing crops and destroy property. ”

“ Fog and cloud are the most striking examples of condensation on a large scale; in weather science it is commonly called volume condensation. One cannot readily make a distinction between fog and cloud; in general, fog is cloud on the ground, while cloud is fog high in the air. When the blue sky becomes white, the change in color is due to condensation—perhaps water dust, perhaps ice dust. If the condensation thickens, distant objects become blurred by the accumulated condensation; a moisture-haze, quite distinct in color from the blue dust-haze, occurs. ”

“ It is the desire of the Weather Bureau to prevent loss by forewarning. The district forecasters do not strain points for high percentages of verification. A row of failures may be discouraging; a mistake against the forecaster may make him a target of derision; but a mistake which results in loss of life is irreparable. Therefore, in making forecasts, it is “safety first.”
Those who make intelligent use of Weather Bureau predictions realize that forecasts are not insurance policies. ”

“ Fog is generally regarded as the chief factor in the impairment of visibility, but the various other factors cannot be arranged in an inflexible order. A desert simoon may impair visibility quite as much as the worst fog; but simoons are rarely in the van of transportation, while fog is practically coincident with every line over which commerce is carried. On the other hand, though the blurring of outlines by refraction, and the slight discoloration of the air by a dust haze may reduce transparency, neither one is a menace to safety. ”

“ And if they intercept and retard the passage of heat coming to the earth, they also retard radiation from the earth at night. In other words, the amount of insolation—that is, of solar heat—received at the earth’s surface is quite as variable as is the daily range; indeed, it is the highest expression of the daily range. At sea level dry air does not always indicate warm days and cool nights; but at levels of 5000 feet or more this is the rule rather than the exception. At any level, changes in temperature are more rapid in dry than in moist air, and the reason therefor is obvious. ”

“ The determination of mean pressure over each of the two hemispheres is more important than that of the mean pressure of the earth as a whole. The fact that the pressure over the southern hemisphere is lowest at the time when it is highest over the northern hemisphere, and vice versa, indicates the shifting of an enormous volume and weight of air from one hemisphere to the other, twice a year. ”

“ If a mass or a wave of air accumulates over a given locality the pressure increases; conversely, if a depression, or a trough, occurs, the pressure decreases. As the observer goes from sea level to a higher altitude the pressure decreases also. At an altitude of 19,000 feet, a height occasionally reached by airmen, the pressure is about half of that at sea level.
The pressure of the air may be determined by weighing it; it is much more convenient to compare it with a column of mercury which balances it. A balance constructed for this purpose is a barometer. ”

“ Gravity is a property of matter that exists apparently throughout the known universe. The apparent fact that matter in masses attracts all other matter in masses is practically all that is known of the essence of it. ”

“ In going from convectionally still air into an updraught, he gets a “bump.” The same result is apparent if, while traversing a downdraught, he strikes still air.
It has been noted that the air ranges itself in layers differing in density, temperature, and moisture content. In many cases an acquired sense born of experience enables the airman to discern these layers and to adjust the wings of his plane in encountering them. Frequently a sheet of smoke or dust separates two cloud layers and experience has taught how to avoid or how to penetrate it.
Air is either going up or coming down. ”

“ Experience will teach the observer the value of popular weather signs and traditions. The experience of out-of-door men whose employments are affected by weather conditions should not be tossed lightly aside. Perhaps the explanation of their reasoning may not bear critical analysis; the results, on the other hand, are apt to have a high value. Weather science now has treatises of inestimable value, but no book from which weather knowledge may be obtained surpasses wind and sky. ”

“ Even the apparently quiet cloud is always in motion within itself. Rising currents of moist air, chilled by its own expansion, cause condensation of the vapor into cloud matter. The coalescence of cloud matter into mist and droplets results in their fall to a lower level, where they are again vaporized; and the vapor, in turn, rises in the updraught. All this is constantly changing and disturbing the electric potential. When, however, the updraught is strong enough to shatter the drops into mist, the potential becomes so high that the violent discharges constitute the thunder-storm. ”

“ Experience has taught the meteorologist that conditions in mid-air of the troposphere, in many instances, are the key to conditions at the surface. They are far more important in air flight; for the airman encounters bumps and holes, both of which are due to sudden inequalities in temperature. The airman and the navigating officer of the airship are likely to encounter cross-winds, the updraught of thunder-storms, and the vagaries of cloud-formation; these, too, are due to irregular conditions of temperature, all of which must be understood and reckoned with in flight. ”

“ The dead calm of tropical seas is the real beginning of the West Indian hurricane. The air, moist almost to the dewpoint, is heated next the surface until it becomes more buoyant than the colder air above it. Finally the unstable equilibrium is overcome and an updraught occurs. The warm air of the updraught is chilled by its expansion and its moisture is condensed. ”

“ If the rain-drops fall through a stratum of air below freezing temperature and strike an object whose surface is also below freezing temperature a varnish of ice will be formed, and it is likely to increase in thickness so long as precipitation continues. When the temperature is very slightly above the freezing point, and the surface air is dry, it is possible that rapid evaporation may chill the varnish of water below the freezing point and change it to ice. Rain-drops in the air may be chilled to a temperature several degrees below the freezing point ”

“ To the airman there is no difference between fog and cloud, so far as the impairment of visibility is concerned. For the greater part, a pilot may fly above stratus clouds if the air is not clear below them; and airmen usually can find plenty of room under the alto-stratus clouds of an overcast sky. But an airman who has once encountered a cumulo-nimbus cloud, or even large masses of low cumulus clouds, is not apt to repeat the experience. In many cases both fog and cloud may be avoided; but one cannot avoid a fog when it shrouds a landing place. ”

“ The floating dust motes of the air are factors of great meteorological importance. They are the nuclei upon which the water vapor of the air condenses. Dense clouds of volcanic dust act as a screen preventing much of the sun’s heat from reaching the earth. The dust particle is the normal nucleus for the cloud particle. The flying, or windblown dust, though a highly important physiographic agent, is not a factor of importance in meteorology. ”

“ Perhaps the white sky might not be called cloud; but if the condensation increases until the color becomes a dark gray, by common consent it is "cloud" in the air, or "fog" if it extends to the ground. The distinction is merely one of degree. Fog and cloud are examples of condensation; but until the droplets coalesce into drops that fall to the ground they are not precipitation. ”

“ The telescope and the spectroscope have shown that the matter entering into the composition of other visible bodies in the universe does not differ from that which composes the earth. Many of the chemical elements that compose the earth have been discovered in the sun and other heavenly bodies, and no chemical element has been discovered in any heavenly body that does not occur in the earth. Air and water vapor occur on the planet Mars, and it is not unreasonable to assume that the meteorology of this planet has much in common with the meteorology of the earth. ”

“ Billow-cloud levels may be a serious problem to the airman, not because they interfere with visibility, but because occasionally they do not do so. When billow clouds are in sight the airman may fly above them or below them. If the two wind layers have about the same degree of humidity there may be no clouds to indicate the position of the plane of contact. Once within this plane, the airman experiences a series of disconcerting bumps, due to the quick transition from one billow to another; sometimes he finds it difficult to rise to the upper layer of air. ”

“ The origin and source of atmospheric electricity is still a problem to be solved; so also is the origin of earth electricity. To the best of human knowledge, the earth is constantly giving off negative electricity, and receiving none in return, except that which is brought down by rain, or by snow, or by lightning strokes which pass from the clouds to the earth. ”

“ And while fog turbulence is slight, cloud turbulence may be very great, and this is notably the case with cumulus, and cumulo-nimbus clouds.
It is not easy to draw the line between fog and mist. Inasmuch as the droplets of mist are much larger than those of fog, they do not scatter so much light; moreover, measured per cubic unit of air, there are not so many of them. At times one may see a gray moisture haze in the direction of the horizon. A little experience enables one to distinguish it from a dust haze. It is never thick enough to impair seeing materially. ”

“ Temperature and Radiation.—Very dry, clear air permits the sun’s rays to pass readily to the earth with but little perceptible loss—that is, dry, clean air is diathermous to the heat rays that impart the feeling of warmth to living bodies. [4] The heat is in turn absorbed by the earth. Earth temperature at the surface, or to a depth of an inch or two, may be many degrees higher than that of the air. Thus, in desert regions, pieces of metal lying on the ground in the sun become so hot they cannot be held in the hand. ”

“ In solids, the cohesion is usually strong, so that more or less force is required to sunder the mass—that is, to separate the molecules. The resistance of cohesion is usually expressed in such terms as tension, torsion, shearing, etc. In the liquefaction of a solid, or the vaporization of a liquid, the force employed to overcome cohesion is measured in terms of heat. For instance, in the liquefaction of ice, about 147 times as much heat is required to change ice at 32° to water at 32° as will raise the temperature of the same weight of water one degree Fahrenheit in temperature. ”

“ The falling rain—and also the hail which occasionally attends a thunder-storm—cools the air through which it passes and the cold air sinks to the earth with a considerable velocity. As it reaches the earth the down-rush plows underneath the warm, moist air in front of the storm, lifting it and thereby aiding the updraught. As the cold air spreads over the ground its velocity is great enough to raise clouds of loose dust that almost always precede the fall of rain. ”

“ In flying from an adverse wind into a wind blowing in the direction in which the plane is moving, the drop is real but the downdraught is apparent merely.
There are actual downdraughts, however, which the airman is certain to encounter—because air going up must be balanced by air coming down. Just as water pours over a perpendicular ledge, forming thereby a cataract, so air is usually pouring over a steep scarp in a similar manner. The air over a plateau is apt to be colder than that several hundred feet below. More certainly it will be colder if it has traversed great fields of snow. ”

“ When the cloud is opposite the sun the surfaces facing the observer have a greater brilliance than the margins of the protuberances. When the light falls aslant, as is usually the case, these clouds throw deep shadows; when, on the contrary, the clouds are on the same side of the observer as the sun, they appear with bright edges.
True cumulus has well-defined upper and lower limits, but in strong winds a broken cloud resembling cumulus is often seen, in which the detached portions undergo continual change. ”