Atmosphere. The fluid or gas which we feel on passing our hand through it, and whose force is visible in a high wind. It is 820 times less dense than water, but its elastic pressure or reaction is equal to 15 lbs. to the square inch, which is also the weight or action downward ; and it is composed of about one part oxygen, and four parts nitrogen or azote. All space is filled with gas, but the passage of the earth through it, and its rotation at the same time, condenses the rare gas of space into an atmosphere, which it the surface of the earth is such as we find it, but is rarer and rarer as we ascend, till at the height of forty-five miles, it no longer reflects light; nor is it capable of keeping clouds in suspension above two or three miles. The energy of the oxygenous part of the atmosphere transferred is the cause of fire, combustion, animal heat, and life. In volume the atmosphere consists of 79 parts of azote or nitrogen ; of 21 of oxygen, of 1.33 of aqueous vapour, and of 0.1 of carbonic acid. In weight, 76.6 of azote; 233 of oxygen; 083 of aqueous vapour ; and 0-15 of carbonic acid gas.