The gravitational pull of the earth holds the Atmosphere attached to the earth. A column of air exerts weight in terms of pressure on the surface of the earth . The weight of the column of air at a given place and time is called air pressure or atmospheric pressure . Atmospheric pressure is measured by an instrument called a barometer . ( Fortin’s barometer and Aneroid barometer I) Atmospheric pressure is measured as force per unit area. The columnar distribution of atmospheric pressure is known as the vertical distribution of pressure. Air pressure decreases with an increase in altitude but it does not always decrease at the same rate. Dense components of the atmosphere are found in its lowest parts near the mean sea level. The temperature of the air , the amount of water vapor present in the air, and the gravitational pull of the earth determine the air pressure of a given place and at a given time. These factors are variable with a change in height. The rate of air pressure decreases with an increase in altitude. Hence, Statement 2 is incorrect.