Of all nature’s tools, water is the most useful. Mountains are carved by it; valleys are shaped; plains spread out; shore lines eroded, and the whole aspect of the earth modelled and reformed through the agency of this great instrument. Water, when it floats in the atmosphere as clouds, tempers the blazing heat of the summer sun, and it likewise tempers the icy blast of wintry winds when northern shores are bathed by currents from southern seas. Whole areas of the earth’s surface are rendered mild and equitable in climate by the modifying effect of great water masses. Deserts bloom when life-giving water is brought to their thirsty soil and irrigation changes barren waste to fertile farm land. In these, and many other ways, water modifies our weather, affects our every-day life, and transforms the earth before our eyes.