Snow-Making

One chilly morning last week, Vincent J. Schaefer of General Electric climbed into a light plane at Schenectady's airport. While his boss, Nobel Prizewinner Irving Langmuir, watched from a control tower, Schaefer told the pilot to fly to a cloud 50 miles away.

As the plane plunged into the cloud, Schaefer radioed back to Dr. Langmuir that he was about to begin. Then he carefully scattered six pounds of dry-ice pellets through the cloud in a belt three miles long. In two minutes flat the poisoned cloud was writhing with agonies so enormous that Dr. Langmuir could see them in faraway Schenectady.

From the cloud's upper surface great pustules of vapor arose. Out of its base poured streamers of snow. They evaporated before they could reach the ground, but Schaefer flew back to Schenectady in triumph. He had touched off the first man-made snowstorm.

Magic Pellets. Schaefer's cloud-poisoning act was the fruit of long, careful experiment. After much research, he learned how to turn the trick in miniature. First he cooled the air in a laboratory cold chamber (rather like a deep-freeze cabinet) to about 5DEG below zero, Fahrenheit. He breathed into the chamber and his breath condensed to fog. He made a magic pass with a single pellet of dry ice. The fog cleared, and glittering snowflakes drifted on to the chamber's floor. From this point it was easy to expand the process to full, outdoor scale.

Both the indoor fog and the outdoor cloud, explained Schaefer, were "supercooled"; their tiny droplets, though well below the freezing point, were liquid water, not ice. They wanted to freeze, but for some reason could not. The dry-ice pellets broke the deadlock. "An almost infinite number" of submicroscopic "ice seeds" formed near their surface. These grew into snowflakes at the expense of the water droplets. The supercooled cloud precipitated.

Planned Storms. The "latent heat" liberated by the freezing of the water produced turbulence in the cloud, spreading the reaction through its mass. Schaefer figured that a single pellet falling 2,000 feet through a cloud might produce several tons of snow. Snowmaking will not cure droughts over large areas. It cannot conjure moisture out of an atmosphere which contains too little to precipitate. But possibly farmers in irrigated districts may coax more snow to fall on the mountain areas which feed their ditches.

Big city governments will watch Schaefer with hope. New York, for instance, has paid over $7,000,000 in a single winter to clean snow from its streets. If artificial snowmaking proves effective, meteorologists will watch for supercooled clouds bearing down on a city. Airplanes will give them the dry ice treatment, making them dump their snow outside the city limits. Perhaps, if ski-minded, the weathermakers can shunt the snow to winter resorts.

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