Rainmaking Scientific rainmaking was started b

Rainmaking
   Before 1946, rainmakers were either liars or honest people who happened to have good luck.  Scientific rainmaking was started in that year by Vincent J.  Schaefer, a scientist at the laboratories of the General Electric Company in New York State.  His success was the result of a lucky accident that changed years of failure into victory.
   During World War Ⅱ , Dr. Irving Langmuir, a scientist, was hired by the General Electric Company to study how and why ice forms on the wings of airplanes. He and a young assistant named Schaefer went to a mountain in the state of New Hampshire, where snowstorms are common and cold winds blow.
   While in New Hampshire, Langmuir and Schaefer were surprised to learn that often the temperature of the clouds surrounding then was far below the freezing point, and yet ice did not form in the clouds. After the War, Schaefer experimented with a machine that created cold, moist air similar to the air found in clouds. To imitate the moist air of a cloud, Schaefer would breathe into the machine. Then he would drop into the freezer a bit of powder, sugar, or some other substance. For weeks and months he tried everything he could imagine.  Nothing happened. No crystals of ice were formed. None of the substances would serve as the center of a snow crystal or raindrop.
   One July morning, Schaefer was dropping in bits of various substances and watching the unsuccessful results. A friend suggested that they go to eat lunch, and Schaefer gladly went with him. As usual, he left the cover of the freezer up, since cold air sinks and would not escape from the box.
   Returning from lunch, Schaefer was beginning to perform his experiments again when he happened to look at the temperature of the freezer. It had risen to a point higher than that required for ice crystals to remain solid. The warm summer weather had arrived without his noticing it. He would have to be more careful in the future.
   There were two choices now. He could close the cover and wait for the freezer itself to lower the air temperature, or he could make the process occur faster by adding dry ice, a gas in solid form that is very, very cold. He chose the later plan. He decided to try a container of dry ice.
   AS he dropped the steaming white dry ice into the freezer, he happened to breathe out a large amount of air. And there, before his eyes, it happened! In the ray of light shining into the freezer, he saw tiny pieces of something in his breath.  He knew immediately that they were ice crystals. Then he realized what had happened! He had made ice crystals by cooling the breath so much that the liquid had to form crystals! Schaefer called to his helpers to come and watch. Then he began to blow his breath into the freezer and drop large pieces of dry ice through it to create crystals which became a tiny snowstorm falling slowly to the floor of his laboratory.