Atmospheric electricity

“ It seems, therefore, that the chief cause of a condition of negative atmospheric electricity is storm, and especially thunder-storms, and that at all other times positive atmospheric electricity prevails. In very many cases this change to negative electricity takes place shortly before the storm approaches; during its progress there may be—especially in thunder-storms—rapidly-repeated alternations of positive and negative conditions, followed by an equilibrium, or by positive electricity. ”

“ None of the theories which endeavor to explain the source of the electricity of the air are satisfactory. Professor Tait, in a recent lecture, is of the opinion that evaporation is the source. Under the influence of the sun's heat, this operation of nature is conducted on an immense scale, and seems to him to be competent to furnish the supply of atmospheric electricity. ”

“ But the law of electric repulsion shows us at once that, as soon as the drops in a cloud are sufficiently electrified, at least the greater part of their charge must pass to the boundary of the cloud. When this occurs, the nature of the further behaviour of the charge presents no difficulty. The reason for our singularly complete ignorance of the source of atmospheric electricity seems to lie in the fact that it can only be discovered by means of experiments made on a scale very much larger than is attainable with the ordinary resources of a laboratory. ”

“ During fog, rain, hail, sleet, snow, and thunderstorms, the electrical state of the air undergoes many variations. The intensity of the electricity increases with hot weather following a series of wet days, or of wet weather coming after a continuance of dry days. The atmospheric electricity, in fact, seems to depend for its intensity and kind upon the direction and character of the prevailing wind, under ordinary circumstances. It has an annual and a diurnal variation. There is a greater diurnal change of tension in winter than in summer. ”

“ After having made careful observations on atmospheric electricity for about a quarter of a century in a country where meteorological changes are more regular and less capricious than in our own island, there is no one whose deductions are more deserving of our attention; the more so as he considers that he has combined his researches into a definite law. His first fact is this: If within a distance of about fifty miles there is no shower of rain, hail, or snow, the electricity is always positive. ”

“ Lightning-Rods, when well constructed, often prevent violent discharges of atmospheric electricity. They have pointed prongs at the top, which allow the negative of the earth (which is being attracted by the cloud when it is positively charged) to pass quietly into the air above ”

“ When Franklin demonstrated that the air is in a permanent condition of electrification even when the sky is clear, people began to study not thunder alone but the general electrical state of the atmosphere. And ever since meteorological observatories have made it a practice to register every day the degree and nature of atmospheric electricity by the use of very ingenious instruments. ”

“ 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. ”

“ There can be little doubt that overhead conductors if connected with the earth play an important part in the distribution of atmospheric electricity. Lord Kelvin, in a recent paper, said that the difference of potential he obtained between the earth and an insulated burning match placed nine feet above the ground was from two hundred to four thousand volts. ”

“ 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. ”

“ We are compelled by the results of the present experiments to conclude that a more rapid discharge of electricity into the atmosphere takes place in sunlight than in darkness from the surfaces of the earth, which is composed of mineral particles charged, as the positive sign of the slope of atmospheric potential indicates, with negative electricity. ”

“ 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. ”

“ 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. ”

“ Thunderstorms are accompanied by darkness, the result of the intense shadow of peculiar thick clouds charged with electricity, whose height varies from 30 yards to 3 miles. The air is never free from electricity. Snow, sleet, hail, and “luminous rain” are frequently indications of great electrification. The atmospheric electric charge is usually positive, and is probably the result of evaporation, but clouds themselves are more generally negative. ”

“ The density of electricity on the peaks, projecting so far above the general level of the earth's surface, is greater than elsewhere; hence they possess a power to discharge like points on an electrified conductor. The air and aqueous vapor become surcharged with electricity; and only a slight condensation, sufficient merely to form clouds without rain, serves to produce discharges of lightning. With heavy gusts of wind the charged air is removed, and a fresh supply is provided into which the peak again pours its electricity. ”

“ I hold that by the law of electric energy the sun is not a thermal or heating engine as the astronomers proclaim, but is an electric generator and is not hot, and that the sun's rays, neither where they originate or where they act are hot, but they come to the earth as cool currents of electricity, which generate heat near the earth's surface by coming in contact with an opposite electricity and the resistance and friction of its atmosphere. ”

“ The tendency is then for the electrified molecule to rise in the atmosphere, thereby accumulating a store of electricity in the higher atmosphere, the movements thence tending toward the poles. As rarefied air and gases are good conductors, being like a vacuum, the electricity will find little resistance at the poles, in returning to the earth. It can either return in disruptive discharges like storms, or in slow discharges in the form of continuous currents, as in the polar aurora. ”

“ There is no place of the earth or sea where the electric fire may not be collected, by making a communication between it and the rubber of an electric machine. Therefore, considering 121that the whole earth is moist, and that moisture is a conductor of electricity, and that every part of the earth must thus communicate with another, it is certain that the electric matter must diffuse itself as far as the moisture of the earth reaches ”

“ To apprehend clearly the nature of this auroral action on the wires as distinguished from that of a thunderstorm, it must be premised that the voltaic or chemical electricity used for telegraphic purposes is of low tension, continuous flow, and perfectly controllable; whereas the free electricity of the atmosphere is of high tension, exploding with vivid light when it finds a conductor, and “dying in the very moment of its birth.” ”

“ Further, when evaporation takes place from an electrified locality, the rising vapor must carry away a charge of electricity by convection, as air and dust carry away electricity from a charged conductor. The condensation of this vapor increases its potential, and, if sufficiently rapid, gives rise to electrical displays. It is a fact of recent establishment that "northern lights" occur in various high latitudes only with southerly winds, which come laden with moisture and probably with electricity. ”

“ It appears, then, that except when the moisture of the air is being condensed, there is no unusual development of electricity. These, results are in accordance with the experiments of Palmieri and others, which show that aqueous vapor in condensing develops positive electricity. No unusual development of electricity has ever been detected by him in a cloud when no rain is falling. ”

“ These facts make the electric light far more wholesome than gas for the illumination of music-halls, churches, or other places of concourse. In a recent trial in the Town Hall at Birmingham, the employment of gas raised the temperature of the atmosphere thirty-eight degrees in three hours, while the building was equally well lighted with electricity for seven hours with a rise in temperature of only two degrees. ”

“ On these accounts we suppose electrified bodies discharge their atmospheres upon unelectrified bodies more easily and at a greater distance from their angles and points than from their smooth sides.—Those points will also discharge into the air, when the body has too great an electrical atmosphere, without bringing any non-electric near, to receive what is thrown off: For the air, though an electric per se, yet has always more or less water and other non-electric matters mixed with it ”

“ The atmosphere is constantly charged with positive electricity,—electricity furnished by the vapors that rise from the sea, especially in tropical regions,—and, on the other hand, the earth is negatively electrized. ”

“ Christie are also mentioned by Noad, who quotes from Oersted’s treatise on “Thermo-Electricity” the statement of the Danish philosopher “that the most efficacious excitation of electricity upon the earth appears to be produced by the sun, causing daily evaporation, deoxidation and heat, all of which excite electrical currents.” ”

“ Change of temperature also influences conductivity.” Page 63, “When using induction machines, the moisture of the air often causes experiments to fail, especially before large audiences. The atmosphere becomes saturated with moisture, and it is often impossible to get the machine in working order.” Several desiccating devices are mentioned by the authors of this work, as used with such machines, to prevent such dissipation or conduction of electricity from the machine into space by the aqueous vapor of the atmosphere. ”

“ The precipitation of vapor-particles into cloud-particles and the agglomeration of these into rain-drops enormously increase the electrification, as the potential of a free charged sphere is proportional directly to the quantity of electricity on it and inversely to its radius. The separation of these highly charged particles of air and water is effected by gravity and the diffusion of gases which would cause the air-particles to escape from among the mass of precipitated vapor to the less highly electrified air above. ”

“ On land, where wires are carried on the tops of poles, the air itself is a sufficient insulator. A few glass rings at the points where the wire passes through the iron staples by which it is supported, and the insulation is complete. But in the sea the electricity would be instantly dissipated, unless some material could be found which should insulate a conductor sunk in water, as completely as if it were raised in air. But what could thus inclose the lightning, and keep it fast while flying from one continent to the other? ”

“ The electric wind in the neighbourhood of the point is sometimes very rapid, but it soon loses its velocity, and the air with its charged particles is carried about with the general motions of the atmosphere, and constitutes an invisible electric cloud. When the charged particles come near to any conducting surface, such as a wall, they induce on that surface an electrification opposite to their own, and are then attracted towards the wall, but since the electromotive force is small they may remain for a long time near the wall without being drawn up to the surface and discharged. ”

“ They thus form an electrified atmosphere clinging to conductors, the presence of which may sometimes be detected by the electrometer. The electrical forces, however, acting between charged portions of air and other bodies are exceedingly feeble compared with the forces which produce winds arising from inequalities of density due to differences of temperature, so that it is very improbable that any observable part of the motion of ordinary thunder clouds arises from electrical causes. ”

“ The friction of any electric upon another awakens it. The friction of the belts upon the drums in cotton factories does it quite freely. Every stroke of India rubber upon paper as you erase a pencil mark excites electricity. The blowing of air upon glass does the same. So, also, does the blowing off of steam from an engine. Electricity has been excited even upon ice by rubbing it when cooled down to 13° below zero. Experiments upon the air have shown that there is usually some free electricity in it, the atmosphere being generally in a positive state, especially when the air is dry and clear. ”