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Magic Tool. Here apparently was a tool of almost miraculous potency. Like dry ice, silver iodide could be injected into clouds from a plane; it could also be sent up as a smoke of fine particles from a generator on the ground. When the G.E. men considered its possibilities, they were appalled. If all the earth's supercooled clouds were turned into rain at once, what would happen to the world's climate? Langmuir estimated that only 200 pounds of silver iodide would be enough to seed the earth's entire atmosphere. The G.E. men dandled their newfound silver iodide, an innocent-looking yellow powder, and wished it were not quite so easy to spray it into the air.
With such a handy device available, they also foresaw a prospect of endless legal problems. Langmuir and his co-workers had already had one forewarning. In the winter of 1946, Langmuir's men gave the dry ice treatment to a mass of clouds near Schenectady. Snow started falling. It fell & fell. The storm had all the usual effects of a blizzard: snarled traffic, accidents, a drop in business for department stores. It would be hard to prove that the dry ice was responsible (if it was), but the incident gave G.E. a serious scare. The big, rich company would be a tempting target for damage-suit lawyers.
General Electric was much relieved when the Army got into the game with its Project Cirrus in 1947, borrowed Langmuir and Schaefer as advisers, later moved many of their operations to New Mexico, where the air is pure, where clouds often come singly and where the people quite sincerely welcome rain. Says Dr. Chauncey G. Suits, director of research: "G.E. has disassociated itself legally from rainmaking in the fanciest ways it can think of."*
Heated Debate. Langmuir's chief interest in New Mexico has been cumulus louds, the tall, billowing formations which sometimes turn into thunderstorms. In much of the U.S. they cause most of the summer rainfall. During New Mexico's summer rainy season (which is not very rainy), there are plenty of towering cumulus clouds, but about nine out of ten of them march magnificently across the sky and vanish without shedding a drop. Near Albuquerque in July 1949, Langmuir performed an experiment that is still debated heatedly and at length in meteorological circles. He started his silver iodide generator early on a morning when the Weather Bureau had predicted no substantial rain. Then he watched developments with a radar.
At 8:30 a.m. a cloud started growing 25 miles away downwind. When the cloud reached 26,000 feet, it suddenly spurted, bulging upward at 15 m.p.h. Soon a radar echo showed that the cloud was full of rain or snow. Heavy rain fell near the Manzano Mountains. A short while later, a second cloud showed a similar convulsion and also produced heavy rain.
Langmuir insisted that both these thunderstorms formed in the "trajectory" of his silver iodide particles and at about the time when the particles must have been entering their bases. He therefore took credit for the rain they dropped as well as for other rain from later storms.