Rain Dates Nearly 400 battles were fought during the Civil War, though rarely on rainy days, when it was hard to move cannons and horses over soggy ground, Charles Hosler says. Eventually people noticed that it frequently rained after the fighting had ceased. In 1870 a civil engineer proposed that the wartime explosions themselves had provoked the rain, suggesting a key to rainmaking. To test the notion, Congress funded experiments in the 1890s; they failed, and their leader, R. G. Dryenforth, became known as Major Dryhenceforth. Hosler says that since battles were generally fought under rainfree skies, it only makes sense that a rainy day would follow many a sunny-day fight.
Make Mud, Not War In 1966 the 54th Weather Reconnaissance Squadron of the U.S. Air Force engaged in an aggressive cloud-seeding program over North Vietnam, Laos, and Cambodia. By lacing clouds with silver iodide, the military hoped to extend the monsoon season and increase the amount of mud along the paths and roads of the Ho Chi Minh Trail, restricting enemy movement. The initial project reported positive results, and the effort was continued from 1967 to 1972 under the code name Operation Motorpool. Although some inside the operation said their attempts to “make mud, not war” impeded the movement of enemy supplies, evidence for that is “unverifiable.”
Asphalt Earth In the 1960s Esso Oil (now part of Exxon Mobil) proposed that coating the earth with black paving materials like asphalt would increase air temperature enough to spur formation of cumulus clouds and encourage rain. To test the idea, the company planned to spray a 20-square-mile patch of asphalt on Venezuela’s Paraguaná Peninsula. But the project was halted before it even began when a Venezuelan government official questioned the company’s motives for the project. Asphalt, it turned out, was a by-product of Esso’s Venezuelan oil refinery—and the government watchdog suspected that the company wanted to use the asphalt within the country chiefly to avoid export taxes.
Gumming Up the Sky One of the strangest weather-related substances in recent times could be Dyn-o-Gel, a polymer powder purportedly able to absorb 1,500 to 2,000 times its weight in water by transmuting into a gel. Dropped into thunderstorms or hurricanes, Dyn-o-Gel was said by its manufacturer, the Florida-based Dyn-o-Mat, to absorb enough water vapor to destabilize a storm. Despite the hype during much of the 1990s, the product was never tested on a large scale because it would have had to be dropped by the trainload to have any real impact.