"Sometimes the drops are very small indeed, although too heavy for the air to hold. They fall as extremely fine rain, which we call mist.""You have not yet explained the dew on the grass," said Norah, "although you said the tumbler of cold water told you all about it.""This is the way teacher explains that to us," said Willie. "He says that often after a warm day the air near the earth becomes suddenly cold at night. The evaporation is still going on rapidly, but as the vapor is formed it is condensed on the cold surface of the ground, the grass, and the leaves of plants, just as the vapor in the room condensed on the cold tumbler. This forms drops of dew."SUMMARY
Invisible vapor is always rising from the earth. It becomes visible when it is condensed. If the air around us is cold the vapor condenses into a fog. It usually rises and floats away before it condenses, and then forms a cloud. When the cloud condenses into actual water, it drops as rain. Vapor condenses on the cold earth and forms dew.
Lesson 15
Birds-Their Legs and Feet