Jacques Wardlaw Redway

“ 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. ”

“ 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. ”

“ 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 a case of this sort the high potential is local—that is, it is confined to the mass of dry desert air, and this mass of air is practically a great condenser which has been charged to a potential much higher than that of the air surrounding. In time—from twelve to forty-eight hours—the high electric charge disappears, and the potential sinks to normal. The question—“How can the air, which is composed mainly of gases, become a condenser and hold a charge of electricity?”—is not difficult to answer. The static charge of an electrified body practically is on the surface of the body. ”

“ A ray of light impinging upon a piece of black cloth is said to be absorbed. If only a part of the ray is absorbed, the rest being reflected, the parts of the ray reflected produce the sensation of color.
If a ray of light is passed through a wedge-shaped prism the component parts of the ray are unequally bent or refracted, and reach the eye in a series of colors. Red is the least refracted; violet suffers the greatest refraction. A ray of white light, therefore, is not of a “bundle” of wave-lengths of the same magnitude, but a bundle of an infinite number of rays of different wave-lengths. ”

“ When a layer of air rests quietly on another the plane of contact, if below the observer, reflects the sky in much the same manner as does a body of water. An object at this plane is seen both upright and inverted, thereby forming a mirage. If the plane of contact is materially above the eye of the observer the inversion occurs in the air. ”

“ A strong updraught of air and the shattering of rain- drops are among the features necessary to produce free electricity. The updraught of air is almost always a noticeable feature, and this takes place conspicuously in the cumulus thunder-head. Ordinarily the base of the cumulus cloud is less than I mile in height; but the updraught that precedes the thunder-storm, and is a potent cause of it, carries the cauliflower head of the cloud to a height of 4 or 5 miles. It is within this head that the potential electricity of the raindrops is changed to kinetic or free electricity. ”

“ If the air of a warm, moist summer afternoon becomes still and oppressive and if cumulus clouds increase in size, a thunder-storm is very likely to follow; and if a nearby cumulus expands vertically into a thunder-head the storm is pretty certain to follow, somewhere or other in the vicinity. The thunder-head may be visible every where within a radius of 25 miles, but the storm path may be a narrow strip not more than 30 miles in length. The path of the thunder-storm, like that of the tornado, is determined by the circulation of the cyclone in which it is formed. ”

“ The discharge merely follows the line of least resistance. The zig-zag discharge, with sharp angles and saw-teeth points, once patronized by artists in order to give effect to their illustrative work, has never been discovered in photographs of lightning discharges. The most extraordinary effects of lightning are the dark flashes occasionally caught in photographs of lightning.
Sheet lightning is generally regarded as the reflection of distant flashes from the surface of clouds. On various occasions the exchange of electricity takes the form of a bluish glow between the earth and a low cloud. ”

“ On rare occasions a tertiary bow may be seen between the observer and the sun.
The colors of the rainbow vary in intensity and in quality. Red is always in evidence outside the primary and inside the secondary bow; orange, yellow and green are commonly though faintly observable; blue is sometimes seen; but violet is rarely if ever observable. The strength and the sequence of the colors depends mainly on the size of the drops, but partly on their distance and the number of them.
Each observer sees his own rainbow, and each rainbow is
Refraction of light passing through rain-drops. ”

“ The slight rise of the barometer in the morning is the diurnal pressure wave. The jump in pressure in the afternoon is the characteristic “thunder-storm nose” which usually is found on barograph records of thunder-storms. An expert observer does not need to refer to his daily reports to find the records of thunder-storms; the barograms show them in most instances. The rise in pressure occurs when the descending wind lifts the warmer air above it. A second “nose” appears about
A thunder-storm nose. ”

“ A shower in one part of the sky and sunshine in another, the observer being between, are requisite for rainbow formation; and this condition, in most parts of the world, is confined to summer showers.
Mirage.—Owing to changes in temperature the density of the air varies almost constantly at different heights. Rays of light passing through air of varying density are bent differently with each change of density. An observer looking at a distant object sees the object with distorted outlines. An elliptical sun at sunset is very common ”

“ Occurrence of Thunder-storms.—Roughly speaking, the lower the latitude of moist regions, the greater the frequency of thunder-storms. In general, of two regions of the necessary warmth, one having moist air and the other dry air, the former is more likely to be visited by thunder-storms. They are more prevalent in the United States than in Europe; they are more prevalent in the southern part of the United States than in the northern part, so far as the region east of the Rocky Mountains is concerned. ”

“ Humphreys states, “the updraughts within a cumulus cloud frequently must break up, at about the same level, innumerable drops, which, through coalescence, have grown beyond the critical size and thereby according to Simpson’s experiments, produce electrical separation within the cloud itself. Under the choppy surges of a thunder-storm, the drops may undergo disruption and coalescence many times, and with each disruption a correspondingly increased electrical charge. Hence, once started, the electricity of a thunder-storm rapidly grows to a considerable maximum. ”

“ Under ordinary conditions the electricity of the air is positive in relation to the ground and the oceans. Its potential does not vary greatly, being rather higher in winter than in summer—a change which might be considered normal. During rainfall or snowfall the potential usually is unsteady, varying rapidly between positive and negative. ”

“ With warm, moist air on the south side of a low, thunder-storms may be expected; and if one has formed, its path may be predicted with reasonable exactness. In the hands of a trained observer a barograph is a most useful aid. ”

“ Safeguards Against Lightning.—The destructive effects of lightning in the United States are chiefly loss of life and loss from fire. Loss of life occurs usually when lightning strikes trees under which people and animals have taken shelter. Trees are the objects most frequently struck. Wooden buildings when struck are apt to take fire instantly, but cases are on record which show that wet shingles and weather boards may be ripped off without further damage. Among structures, oil tanks stand first in the likelihood of destruction by lightning. ”

“ Rainbow.—The rainbow against a dark gray background of cloud is one of the most beautiful objects in nature. It may be seen as a full circle against spray thrown into the air, or against a mist. The rainbow of the summer shower consists of a bright arc near the horizon and usually a fainter arc above. The radius of the bright, or primary bow is about 42 degrees of arc; that of the upper or secondary bow is not far from 52 degrees of arc.
The rainbow is best observed when the sun is not more than 45 degrees above the horizon; it forms in the side of the sky opposite the sun. ”

“ Every substance must possess surface and the molecules of the gases composing the air are not an exception; neither are the dust particles floating in the air; therefore they act as condensers, receiving and discharging electrons. ”

“ The layman also may forewarn himself with a reasonable degree, if not of certainty, at the least, of probability. An aneroid barometer, if watched closely, may be serviceable; unless intelligently used it is of doubtful service to any but a trained observer. ”

“ Church spires and large barns are frequently struck, and isolated buildings are regarded as a far greater risk than city buildings; indeed, in the compactly built areas of a city the risk from lightning stroke is negligible.
Lightning rods afford the best protection against lightning. ”

“ Ether wave indicator, Meteorological Laboratory. The wire at the upper right of the spark gap leads to the aerial. The lower binding post of the condenser leads to the ground. The coherer is shown above the bell hammer. affect the potential of the air materially, but it affects the conductivity greatly. Dry air is a poor conductor; and dust particles, unable to discharge their load of electricity, are strongly repellant and remain suspended in the air, sometimes for several days. ”