The greatest difficulty with water is that it will not "stay put"-- it is continually on the move.

The same perpetual circulation, with change of form, but without loss of substance, which is taking place in the engine and in our bodies, is taking place in the world around us.

The water from the ocean, the lakes, and the rivers is continually evaporating under the heat of the sun and rising in the form of vapor, or invisible steam, into the air.

There it becomes cooler, and forms the clouds; and when these are cooled a little more, the vapor changes into drops of water and pours down as rain, or, if the droplets freeze, as snow or hail.

The rain falls upon the leaves of the trees and the spears of the grass, or the thirsty plowed ground, soaks down into the soil and "seeps" or drains gradually into the streams and rivers, and down these into the lakes and oceans, to be again pumped up by the sun.