Fixing the Sky (12 page)

Espy viewed the atmosphere as a giant heat engine. According to his thermal theory of storms, all atmospheric disturbances, including thunderstorms, hurricanes,
and winter storms, are driven by steam power. Heated by the Sun, a column of moist air rises, allowing the surrounding air to rush in. As the heated air ascends, it cools and its moisture condenses, releasing its latent heat (this is the “steam power”) and producing rain, hail, or snow. Espy emphasized, correctly, the importance of knowing the quantity of vapor in the air, “for it is from the latent caloric [or heat] contained in the vapor that all the force of the wind in storms is derived. It is only when the dew-point is high that there is sufficient steam power in the air to produce a violent storm; for
all storms are produced by steam power
.”
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His theory was well received by many scientists of his time, including a committee of the French Academy of Sciences chaired by François Arago. The convective theory is now an accepted part of meteorology, and for this discovery Espy is well regarded in the history of science.

Espy strayed from the scientific mainstream when he promoted his idea that significant rains of commercial importance for agriculture and navigation could be generated by cutting and burning vast tracts of forest. He believed the heat and smoke from these fires would create huge columns of hot air, producing clouds and triggering precipitation, much like the effects of volcanic eruptions. He listed five scientific reasons why setting large fires should produce rain: (1) experiments showed that expanding air cools dramatically, and (2) under certain conditions of high humidity forms both a visible cloud and significant amounts of precipitation; (3) chemical principles indicated that the “caloric of elasticity” (a venerable term for latent heat) released in the condensation of this vapor is immense, equal to about 20,000 tons of anthracite coal burned on each square mile of cloud extent. Espy's convective theory further held that (4) this release of heat would keep the cloud buoyant, lower the barometer, and “cause the air to rush inward on all sides toward the center of the cloud and upward in the middle, thus continuing the process of condensation of vapor, formation of cloud, and generation of rain.”
¹⁰
Espy derived his final point empirically by collecting observations and testimonials to the effect that (5) air does indeed rush inward on all sides toward the center of the region where a great rain is falling and upward into the cloud.

Espy explained that three things can prevent rains from accompanying great fires: (1) winds, (2) excessive moisture, and (3) stability of the upper levels of the atmosphere. He released small balloons and tracked their flight in order to get a sense of the winds, and he used a hygrometer to measure atmospheric moisture and estimate its changes with height. Stability was more of a problem, for as he observed, in the present state of science, the levity of an upper stratum of air could not always be known. Correspondents, friends, and even a congressman laughed at Espy when they heard of his proposal to make rain, but he assured
them that science was on his side. He even ventured a prediction of how the experiments might turn out in favorable conditions and felt there was no disgrace in desiring to see a great experiment made. He anticipated that his labors would be crowned with success.

In 1838 Espy petitioned the U.S. Senate to reward him in proportion to his ability to make rain by burning woodlands. James Buchanan (D-Pennsylvania) apologized to his colleagues for the “strange petition” he was about to present, but assured them that it came from “a very respectable and scientific man” with excellent references and credentials:

Buchanan supported the petition based on Espy's scientific reputation, but “scarcely knew himself what to say about it.” Senator John J. Crittenden (W-Kentucky) “doubted very much, whether, even if this thing was possible, it would be a good policy to encourage the measure.” He thought that no mortal should have the power that Espy professed to have and no one could take the Ohio River under his special protection:

The senators, obviously enjoying the discussion, pointed out that no citizen should be empowered to hoard up the clouds and vapors or to dispense them at will. Buchanan's motion failed, and Espy's petition lay on the table. That year, and for several years following, Espy looked closer to home, seeking, but
failing to receive, government support for rainmaking. “Magnificent Humbug” opined the
Genesee Farmer
. According to the
Boston Quarterly Review
, “The public at large think of him as a sort of madman, who fancies that he can produce artificial rain.”
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Espy's magnum opus,
The Philosophy of Storms
(1841), includes a long section titled “Artificial Rains,” in which he compiled testimonies of rainfalls accompanying volcanic eruptions and large fires: “The documents which I have collected on this subject, if they do not prove that the experiment will succeed, do at least prove that it ought to be tried.”
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Espy concluded that if a large body of air is forced to ascend in a column, a large self-sustaining cloud will be generated and cause more air to rise up into it to form more cloud and rain. He argued that this was certainly the case in volcanic eruptions and should also be the case for great fires. He cited the mysterious connection between volcanoes and rain as noted by the famous geographer and explorer Alexander von Humboldt, who observed that sometimes during a volcanic eruption a dry season changed into a rainy one. Thus he argued that the rainmaking effects of a giant forest fire should mimic those of a volcanic eruption.

Espy scoured the literature for supporting evidence. He cited Martin Dobrizhoffer, an Austrian Jesuit evangelist in South America who wrote that he witnessed the tribes of the Abipones in Paraguay producing rain (in an admittedly very rainy climate) by setting fire to the plains. He also cited the practice of American Indians burning the prairies to produce rain, and he called for his correspondents to send in reports and testimonies of similar instances supporting his theory. An observer in Louisiana wrote that a conflagration in the long grass in the prairies of that state was soon followed by rain.

In 1845 Espy issued a circular letter “To the Friends of Science” with specific details of his rainmaking plan. He proposed a massive experiment along the Alleghany Mountains (a region quite familiar to him): “Let forty acres ... be fired every seven days through the summer in each of the counties of McKean, Clearfield, Cambria, and Somerset, in Pennsylvania; Alleghany in Maryland; and Hardy, Pendleton, Bath, Alleghany, and Montgomery, in Virginia.” Espy anticipated the effects of upper-air wind shear by recommending that woodlots several miles apart be fired, “so that the up-moving column of air which shall be formed over them may have a wide base, and thus may ascend to a considerable height before it may be leaned out of perpendicular by any wind which may exist at the time.”
¹⁴

He also proposed an even larger, continental-scale project that involved simultaneously firing masses of timber in the amount of 40 acres every 20 miles,
every seven days, along a line of 600 or 700 miles in the western United States along the Rocky Mountains. Espy predicted that the
probable
outcome of this managed system would be regular, gentle, and steady rains sweeping across the entire country like clockwork for the benefit of farmers and navigators. Here is how Espy explained his plan:

Espy presented the testimonies of eyewitnesses who saw both clouds and rain produced by fires. The good citizens of Coudersport, Pennsylvania, including attorneys, judges, and ministers, attested that both clouds and rain were produced by the burning of a fallow field in July 1844. Similar phenomena had attended a prairie fire in Indiana the previous summer. Surveyor George Mackay claimed to have stimulated convective showers in Florida by cutting and burning “exceedingly inflammable” saw grass: “We often fired the saw-grass marshes afterward ; and whenever there was no wind stirring, we were sure to get a shower.”
¹⁵
Apparently, a number of farmers in Florida were in the habit of setting grass fires to produce rain when they planted their corn. A forest fire in Isle Royale, Michigan, in 1846 produced similar results, as did extensive forest fires in Nova Scotia and, apparently, coal burning in the industrial city of Manchester, England.

Perhaps the most striking eyewitness testimony of “steam power” of the atmosphere being kindled by a great fire was sent to Espy by the Reverend J. D. Williamsom, who was hiking with a companion on a mountain summit near Keene, New Hampshire, in July 1856: “The weather was excessively hot. Not a cloud was to be seen, nor was there a breath of wind stirring. Looking to the southeast at a distance of some five or six miles, I saw a fire just kindled in a fallow of some acres in extent. The column of smoke ascended perpendicularly and unbroken.”
Williamsom, who was familiar with Espy's theory, remarked to a companion that the fire should soon produce rain unless disturbed by upper currents:

For his work in mapping and forecasting and for his tireless promotion of rainmaking, Espy earned the derisive sobriquet “the Storm King.”

The year Espy moved to Washington, the popular magazine writer Eliza Leslie published a short story in
Godey's Lady's Book
called “The Rain King, or, A Glance at the Next Century,” a fanciful account of rainmaking a century in the future, in 1942. In the story, Espy's great-great-grand-nephew, the new Rain King, offers weather on demand for the Philadelphia area. Various factions vie for the weather they desire. Scores of alfalfa farmers and three hundred washerwomen petition the Rain King for fine weather forever, while corn growers, cabmen, and umbrella makers want consistent rains. Fair-weather and foul-weather factions apply in equal numbers until the balance is tipped by a late request from a highsociety matron desperately seeking a hard rain to muddy the roads and prevent a visit by her country-bumpkin cousins.

When the artificial rains come, they satisfy no one and raise widespread suspicions. The Rain King, suddenly unpopular because he lacks the miraculous power to please everybody, takes a steamboat to China, where he studies magic in anticipation of returning someday with new offerings. “Natural rains had never occasioned anything worse than submissive regret to those who suffered inconvenience from them, and were always received more in sorrow than in anger,” Leslie wrote. “But these artificial rains were taken more in anger than in sorrow, by all who did not want them.”
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Leslie's short, humorous fantasy revealed a dramatic and instantaneous change in public attitudes “precipitated” by artificial weather control. Although Leslie was no meteorologist, her tale “showed a far better grasp of weather's
human dimensions and of the pitfalls of weather control than anything Espy ever wrote.”
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Since then, however, the intractable human dimensions of weather and climate control have taken a backseat to the technical schemes of optimistic rain kings and climate engineers with relatively simple ideas, or at least angles.