Meteorology: The Science of the Atmosphere

by Charles Fitzhugh Talman

In support of such a bold assertion it might be pointed out that we already control the weather to a certain limited extent. When the horticulturist burns orchard heaters to protect his fruit from frost he certainly alters the weather for a few hours over a small area of the earth. If there were any practical justification of the process, the temperature of the air over an entire State, for example, could be raised throughout the winter, with appreciable effects on agriculture. The difference between heating a single orchard for a night and heating a State for a season is one of degree, and not of principle.

The climate of a city is, through causes dependent upon man, materially different from the natural climate of the surrounding country. Every dwelling provided with heating arrangements enjoys an artificial summer amid the blasts of winter. Local control of the winds is exemplified in the planting of thousands of miles of trees as windbreaks in the prairie regions of our Middle West. By moderating the winds this process has a marked effect on temperature and evaporation and is so beneficial to crops that in the aggregate it furnishes a striking example of successful “weather-making” by mankind. Analogous methods, perfectly feasible with means already at our disposal, would change the whole climatic aspect of large areas of the earth’s surface.

The question “Can we make it rain?” may be answered in the affirmative by those who are neither impostors nor victims of self-delusion. The deposit of spray from the spout of a teakettle might, without much stretching of terms, be described as a miniature artificial rainstorm; but much bigger showers, in nowise different from those occurring in nature, can also be produced artificially. Huge clouds have often been observed to form over forest fires and other great conflagrations. These clouds, composed of water drops, tower far above the smoke cloud, and are identical in character and mode of origin with the cumulus and cumulo-nimbus clouds formed by currents of moist air rising from the heated ground on a summer day. There are several well-authenticated cases in which rain has been seen to fall from such clouds, and these showers have sometimes been so heavy as to extinguish the fires that generated them. Hence, given favorable conditions of humidity, temperature and wind, mankind can certainly produce a rainstorm (and perhaps a thunderstorm into the bargain) by the relatively simple process of building a big fire.

Unfortunately the vast majority of methods whereby man has attempted to regulate the weather have no such rational foundation as those we have just mentioned. Some are wholly superstitious, others are purely empirical, and yet others are based upon ideas that their promoters suppose or pretend to be scientific, but that are actually fallacious.

In the history of superstitious practices weather-making plays a prominent part. Sir J. G. Frazer, in that great storehouse of myth and folklore, “The Golden Bough,” says: “Of the things which the public magician sets himself to do for the good of the tribe, one of the chief is to control the weather and especially to insure an adequate fall of rain. In savage communities the rain-maker is a very important personage; and often a special class of magicians exists for the purpose of regulating the heavenly water supply.” Frazer devotes ninety pages of his work to a rapid survey of the superstitious methods of controlling the weather that have found credence among the various races of mankind. These range all the way from the most complicated ceremonies to the summary expedient of throwing a passing stranger into a river to bring rain.

The sailor who whistles or scratches the mast to raise a wind is merely keeping up a quaint custom, in the efficacy of which he may or may not put some lingering faith, but which the world at large long since ceased to take seriously. When, however, a vessel master attempts to disperse a waterspout by firing a cannon at it, he is doing what nine educated persons out of ten would probably do under the circumstances. Yet one process is no more futile than the other, and both are based on superstition. Ages ago sailors sought to frighten waterspouts away by pointing knives at them, or by shouts and the clashing of swords, and the use of cannon originally embodied the same idea of terrifying the watery monster. It is our purpose in the present chapter to describe especially several processes of weather-making which, while not obviously chimerical from the point of view of the layman, have been more or less positively discredited through the scrutiny of men of science.

The efforts of modern weather-makers have been directed especially to two objects; viz., the production of rain and the prevention of hailstorms. In the United States a certain amount of ingenuity has also been devoted to the task of dispelling tornadoes. Some years ago a device for the latter purpose was patented, consisting of a box, containing explosives, mounted on a pole and erected a mile or so to the southwestward of the village to be protected from these unwelcome visitors. The force of the wind was expected to detonate the explosives by driving a movable board against percussion caps. The inventor believed that a violent explosion would disperse the passing tornado funnel. Apart from the fact that a single installation of this character, or even several of them, would seldom happen to be at exactly the right spot to explode close to the relatively small vortex of a tornado, the effect of the explosion, even in the very heart of the storm, would certainly be negligible. The energy that keeps the tornado in action is supplied continuously from a level far above the earth, while the disturbance due to the explosion would be only momentary. Above all, the energy developed in any discharge of explosives that the community could afford to pay for would be quite insignificant compared with that which prodigal nature supplies to the tornado.

The same disproportion between the giant forces at work in the atmosphere and the pygmy forces at the disposal of mankind is a point that is overlooked in most attempts at weather-making.

The widespread belief that rain can be produced by explosions rises so far above the level of ordinary popular delusions that it has sometimes led to large expenditures of money on the part of drought-ridden communities and even of national governments. Perhaps the most remarkable example of official confidence in the efficacy of this process was that furnished some years ago by the Volksraad, or legislative assembly, of the Transvaal, which passed a law forbidding the bombardment of the clouds to produce rain, on the ground that the rain-makers were thwarting the will of the Almighty!

One manifestation of the belief in question is found in the common assertion that rain is the usual sequel of battles. This idea originated, however, long before the invention of gunpowder. It is mentioned by Plutarch and other writers of antiquity. Whatever superstition or crude process of reasoning may have first given support to this notion in the popular mind, the explanation now commonly advanced is that the condensation of moisture is promoted by the concussion due to cannonading, or that the drops already condensed and constituting the clouds are jostled together by the same disturbance, with the result that they coalesce and fall as rain. There is no ground for such assumptions. As was once pointed out by the late Professor Simon Newcomb, the effect of a violent explosion upon a body of moist air a quarter of a mile distant is about the same as that which the clapping of one’s hands would produce upon the moist air of the room in which the experiment is performed. Again, if we stand in the steam escaping from a teakettle and clap our hands we shall not produce a shower, though we jostle the water drops much more than the explosion does at a distance of a quarter of a mile.