In recent years another explanation has been offered for the alleged production of rain by explosions; viz., that the smoke and gases arising from an explosion increase condensation by increasing the number of “nuclei” in the atmosphere. As we have seen, however, in considering the natural formation of rain, the number of condensation nuclei normally present in the atmosphere is so great that it must be diminished, rather than increased, before drops as large as raindrops can be formed. Moreover, the nuclei required for the condensation of water vapor, including molecules of highly hygroscopic gases, are given forth in abundance by great manufacturing centers, yet these places do not have a heavier rainfall than the surrounding country. Pittsburgh, for example, is actually one of the driest places in Pennsylvania.
One obvious reason why rain often follows a battle is that battles are frequently fought in regions where rain normally occurs every two or three days, on an average, whether in peace or war. In northern France, for example, where the battles of the World War were plenteously interspersed with showers, meteorological records show that the average number of rainy days per annum is upward of 150. The drenching rains that made “Virginia mud” a byword during the American Civil War gave great currency to the belief in “rain after battles,” Here, again, we have accurate weather records to help us dispel a fallacy. Thus at Richmond rain falls on 122 days in an average year, at Lynchburg on 124 days, and at Petersburg on 105 days.
There is, however, a particular reason why rain is rather more likely to occur soon after a battle than shortly before one; viz., the fact that intervals of fair weather, with consequent dry roads, are used by commanders in carrying out the movement of troops that precede an engagement. By the time such arrangements, often occupying several days, are completed, the “spell” of fine weather is likely to be over, and a rainstorm is due in accordance with the normal program of nature.
The most famous undertaking in the history of rain-making—and one which has had an incalculable effect in fostering the credulity of the public with respect to similar enterprises—was that carried out by General Robert Dyrenforth on behalf of the United States Government in 1891. Congress voted appropriations amounting to $9,000 for these experiments, and Dyrenforth was appointed a “special agent” of the Department of Agriculture to direct them. After some preliminary trials in the suburbs of Washington, the experimenters proceeded to a ranch near Midland, Texas. Here a few balloons filled with a mixture of oxygen and hydrogen, as well as several sticks of dynamite carried up by kites, were exploded in the air, but the only explosions of considerable magnitude were set off on the ground. The experiments continued over a period of three weeks and in some cases showers fell within a few hours after an explosion, but, in spite of the somewhat favorable tone of the official report, the consensus of scientific opinion was that the undertaking was a failure, while the views of the public at large were divided. The attitude of the Government is sufficiently indicated by the fact that it has never since undertaken experiments in this line. The one tangible outcome of this affair was that a crop of private rain-makers sprang up all over the country, and to this day the example set by the official experimenters is cited in support of every sort of harebrained scheme for juggling with the weather.
In 1911 and 1912 the late C. W. Post, of breakfast-food fame, expended many thousand pounds of dynamite in efforts to produce rain in Texas and Michigan. Showers undoubtedly occurred in conjunction with Post’s experiments, but conditions favoring their occurrence were plainly indicated on the current daily weather maps, and they had been duly forecast by the Weather Bureau.
The professional rain-maker does not generally resort to the expensive process of bombarding the clouds. His methods most frequently involve the use of chemicals, and the details are shrouded in mystery. For example, about a quarter of a century ago one Frank Melbourne, known as “the Australian rain-maker,” enjoyed great celebrity and coined money by his exploits in this field. His plan was to shut himself up in a barn, freight car, or other structure, and manipulate his chemicals and electric batteries for hours or days. Naturally rain sometimes came after these operations, but as often it did not.
Several of the methods that have been suggested from time to time for producing rain are sufficiently discredited by the fact that the expense of putting them into execution would more than offset any benefits derived from the rain, if the experiments proved successful. Thus one genius, observing the deposit of water on the outside of an ice pitcher in a warm room, proposed to set up a barrier packed with ice in the path of moisture-bearing winds. Another plan occasionally suggested is to sprinkle the atmosphere aloft with liquid air or liquid carbon dioxide, in order to lower the temperature, by the rapid evaporation of these substances, below the point of condensation. A third proposal is to create a local updraft of air by means of powerful fans or blowers, thus imitating the convectional process by which clouds and rain are formed in nature.
Lastly, various plans have been suggested for altering the electrical condition of the upper atmosphere—for example, by electrical discharges from balloons—on the assumption that rainfall might thus be promoted. This assumption, however, is not consistent with known facts as to the relation between atmospheric electricity and the condensation of atmospheric water vapor.
While in America a vast amount of money has been wasted on futile experiments in rain-making, far more has been spent in Europe on schemes for averting hailstorms. Methods of accomplishing this purpose have varied from age to age. In antiquity it was the custom to shoot arrows or hurl javelins toward the gathering clouds in the hope of frightening them away. In the Middle Ages ecclesiastical or occult agencies were invoked; “hail crosses” (such as are still seen in the Tyrol) were erected; and the ringing of church bells was considered efficacious against both hail and lightning, as is shown by the inscriptions found on many old bells.
The custom of firing cannon at the clouds to avert hail began centuries ago in Styria and northern Italy, and it was well established in France before the Revolution. Toward the end of the eighteenth century, however, another method of hail protection was introduced in France, whence it spread over the rest of Europe. This consisted in setting up tall, metal-tipped poles, imitated from lightning rods. It was supposed that these poles, which were known as paragrêles, would draw the electric charge from the clouds and thereby (though nobody could say why) would prevent the formation of hailstones. This device, though reported on unfavorably by the French Academy of Sciences, gained great popularity. One of its advocates, writing in 1827, states that more than a million paragrêles were at that time in use in France, Switzerland, Italy, Austria, Bavaria, and the Rhine country. The vogue enjoyed by these contrivances is said to have come to a sudden end when a tremendous hailstorm not only devastated the fields and vineyards they were supposed to protect, but also knocked down a great number of the rods themselves.