sonry, and they course across the sky at higher speed than man can travel. A locomotive can travel a mile in thirty-seven seconds, a fast yacht in about twice that time, and a swift torpedo boat in one hundred and ten seconds. The upper clouds move with an average velocity of a mile in thirty-six seconds, and have been observed moving as rapidly as a mile in eighteen seconds. Equally remarkable are the plastic walls of these aerial reservoirs. No courses of heavy stone and mortar are to be found; but in their stead drops of water so minute that a thousand of them side by side would not extend farther than one inch. If the temperature
Alto-cumulus.
was low during the building of the cloud, the water drops are changed into ice spicules and snowflakes.
From such reservoirs the rain falls as a rule harmlessly. A collapse, which rarely occurs, is known as a cloud-burst. Then, the deluge destroys life and property, sweeping all before it.
If we were able to control the valves and vents of this tremendous pump-reservoir, we could cause rain at will and shut off the downpour at pleasure. But hardly yet may we hope to master the rain. Rain-makers of our time bang and thrash the air, hoping to cause rain by concussion. They may well be compared to impatient children hammering on reservoir walls in a vain endeavor to make the water flow. Rain-control is a scientific possibility. Successful rain engineers will come in time, we
