"Certainly," the Forecaster answered, "otherwise we wouldn't be able to tell the precipitation of a region at all. There is a regular instrument for it, called a shielded snow-gauge. This is like a rain-gauge, boys, only it stands ten or twenty feet above the ground, to avoid surface drifting. The snow caught is melted and expressed as so many inches of precipitation. Sometimes the depth of snow is measured by thrusting a measuring stick down to the ground. "Of course, that's not nearly all that the Weather Bureau has to do with snow. In the northern states, especially of the Pacific Coast, snow surveys are of great importance. The Weather Bureau often sends men to determine the amount of snow that has fallen over a given area, in order to find out how much water may be expected. This is needed in flood forecasts and irrigation projects. Some of our men, boys, can tell you thrilling tales of their expeditions on snow-shoes up snow-covered slopes where there is never a trail. "Railroads whose tracks run through the regions of heaviest snowfall build snowsheds to keep their lines from being buried in avalanches, and these sheds are built to withstand pressures calculated by the Weather Bureau. Where drifting occurs and the railroad tracks are being covered with the drifting snow, it is the combined snow and wind records of the Weather Bureau which form the basis for the work of the rotary-snow-plow. "Even so, boys, the value of the work of the Weather Bureau in snow surveys is very small compared with the importance of frost warnings. These save the country tens of millions of dollars every year, especially in the fruit sections." "You mean by smoking them?" queried Ross. "Father heard about that a couple of years ago and bought a lot of fire-pots for his orchard." "How did he succeed?" asked the Forecaster. "He didn't succeed at all," the boy answered. "There were only two bad frosts that spring, and both times the evening before had been so warm that no one suspected that there would be frost before morning. The one night that he did start the fires, it turned warm towards midnight and we wouldn't have needed the fires any way. Old Jed Tighe, who's got the biggest fruit farm here, has made fun of Father's fire-pots ever since." "Now, if your father had received the Weather Bureau's frost warnings in advance," the Forecaster said, "he wouldn't have wasted fuel on the night that there wasn't a frost and he wouldn't have let his crop freeze on the nights that the temperature really did drop below the danger point. For example, boys, if the League of the Weather had been in existence at that time and could have given good frost warnings, all that crop would have been saved, wouldn't it?" "Yes, sir," said the boys, "it would." "Of course," the Forecaster continued, "a really progressive fruit-grower ought to make himself partly independent of the Weather Bureau. He can put up frost-alarm thermometers." "What are they, sir?" asked Anton.