Composition of atmosphere *Composition of the atmosphere* The earth's atmosphere is a multilayered gaseous envelope which surrounds the earth for all sides and is attached to the earth's surface by it.(earth's) gravitational force. The air is a mechanic mixture of several gases. Basically, the atmosph is composed of three major constituents, (1) gases (2) water vapour, and (3) aerosols * Gases:- The gaseous composition of the atmosphere consists of two categories of gases e.g. (i) constant or permanent gases, and (ii) variable gases. It may be mentioned that the study of atmospheric gases started in the 18th century when carbon dioxide was discovered and studied in 1752 followed by the discovery of gaseous nitrogen (N J by Rutherford in 1772 and was named as mephitic air. The oxygen atmosphere in parts per million (ppm), parts per billion (ppb) and percent by volume. The following gas laws have been formulated from time to time