Even today, there is a good deal of mystery about the formation of hail and many people think there are ways of preventing it or causing the storm to make little hailstones instead of big ones and thus having much less destruction. Hail causes many millions of dollars worth of damage every year in the United States and almost any effort to reduce the losses seems to be justified. Scientists believe that hailstones are very small in the beginning but grow in size as they go up and down several times in the thunderstorm clouds. Even in hot weather, it is very cold in the top layers of one of these great clouds. Raindrops freeze and in falling gather more water or snow in these high regions. Soon they are caught in rising air currents and carried up into freezing temperatures again. On each trip up and down, another layer of water or snow gathers on the outside and is frozen. At last the multi-layered stones become so heavy that they fall to the ground, in spite of rising currents, and as they leave the cloud they come down with great rapidity and may beat crops to the ground, batter automobiles, break glass and bruise and sometimes kill livestock. A hailstone the size of a baseball falling many thousands of feet is a very dangerous thing. For many years after the hail-shooting experiments, it was thought that nothing could be done about it except to carry hail insurance. Then, shortly after World War II, scientists of the General Electric Company announced that they had conducted some successful experiments in controlling the weather and this led to efforts to control rainfall, prevent hail, and stop hurricanes. The man who started this new effort at weather control was Vincent Schaefer. He observed the weather on top of Mt. Washington, in New Hampshire, a place where it is very cold and windy in winter. The observatory is fastened to the solid rock of the mountain top by steel cables, to keep it from being blown off. Vast quantities of ice accumulate on the building. Snow comes down in great quantities at times but is generally carried by high winds which have reached terrific speed, on one occasion going up to 231 miles an hour. Conditions there are in some respects like the weather in the top of a big thunderstorm.