Some sections of our country have special kinds of wind that are peculiarly their own, notably Colorado, Wyoming, and Montana where the chinook reigns. This phenomenon belongs only to the cold season and only to the coldest days of it. It is a warm wind that begins to blow without much warning from the southern quarter. It is caused by a body of cold air suddenly falling from a great height. As it falls its descent heats it and it causes a rise in the temperature of the surrounding locality that greatly exceeds any rise from other causes. The increase in temperature will be as much as forty degrees in fifteen minutes. This sudden dry heat is a great snow-eater. If it were not for the chinook the snow-blanket would stay so much longer on the cattle ranges that they would be useless as such. In northeastern sections of our country and Canada the warm winds blowing in from the ocean at the approach of a cyclone do away with the snow rapidly but with nothing like the speed of the chinook. Another phenomenon of the air that is of tremendous benefit to man is the sea-breeze. During the intense heat of a hot wave the wind may shift to the east in Boston and in fifteen minutes coats are comfortable. Such a shift may bring relief to a strip of land two hundred miles wide along our entire eastern seaboard. The sea-breeze is explained by the fact that the land cools more quickly than the sea and also warms more easily. During the whole forenoon of a summer's day the sun has been pouring upon land and sea, but the land-air has become much hotter than the air over the sea. It rises and the sea-air rushes landward. By midnight the land has cooled off even more than the sea and the heavier air now presses out to sea again. On every normal day this balancing process takes place. If it doesn't conditions are abnormal and chances are that mischief is brewing. This ebb and flow of warmer and cooler air is, on a small scale, exactly what is happening on a vastly larger field of operations between cyclone and anticyclone. And it is the dominance of the anticyclone with its prolonged rush of air from the northwest that interrupts the sea breeze for two or three days in winter, as the cyclone prevents the night land breeze from taking place when it is central off the eastern coast. The exchange of air between mountain side and valley is similar to the land-and-sea breeze. The rarer air on the mountain side heats faster by day and cools faster by night than the denser air in the valley. Therefore during the day it rises and the valley air rushes up to take its place; during the night it cools and sinks into the valley. This is a great help when one is shut up in a secluded valley for several days and cannot get a good view of the skies. The atmosphere is acting properly and will remain settled so long as the air blows up your ravine for most of the day, and turns about sundown and blows out and down the ravine like a flood of refreshing water.