We have yet to ascertain the causes of the many local winds prevailing both on the ocean and the land, and which do not appear to be influenced by any such general principle as the Trades or the Monsoons.

The force of air in motion gives us the gentle breeze, the gale, or the whirlwind.  At one hundred miles an hour it prostrates forests.  In the West Indies, thirty-two pound cannon have been torn by it from their beds, and carried some distance through the air.  Tables of the velocity of winds are familiar to our readers.

Let us next advert to the connection of the atmosphere with Vapor and Evaporation.  The vapor rising from the earth and the sea by evaporation, promoted by dry air, by wind, by diminished pressure, or by heat, is borne along in vesicles so rare as to float on the bosom of the winds, sometimes a grateful shade of clouds, at other times condensed and gravitating in showers of rain.  Thus it enriches the soil, or cools the air, or reflects back to the earth its radiated heat.  At times the clouds, freighted with moisture, present the most gorgeous hues, and we have over us a pavilion more magnificent than any ever constructed by the hand of man.  These clouds are not merely the distilleries of rain, but the reservoirs of snow and hail, and they are the agents of electric and magnetic storms.

Notwithstanding their variety, clouds are easily classified, and are now by universal consent distinguished as follows.

In the higher regions of the air we look for the Cirri, the Curl Clouds.  They are light, lie in long ranges, apparently in the direction of the magnetic pole, and are generally curled up at one extremity.  They are sometimes called Mackerel Clouds.  They are composed of thin white filaments, disposed like woolly hair, feather crests, or slender net-work.  They generally indicate a change of weather, and a disturbance of the electric condition of the atmosphere.  When they descend into the lower regions of the air, they arrange themselves in horizontal sheets and lose much of their original type.  The Germans call them Windsbaeume, or wind-trees.

The Cumulus is another form of cloud, which floats along in fleecy masses, in the days of summer, but dissolves at night.  Sometimes it resembles a great stack or pile of snow, sometimes it has a silvery or a golden edge, as if we saw a little of the lining.  Sometimes they lie motionless in the distance, and are mistaken by mariners for land.  They rest upon a large base, and are borne along by surface-winds.  Their greatest height is not more than two miles.  They carry large quantities of moisture with them, and, when preceding rain, fall rapidly into other shapes.

The Stratus, or Fall Cloud, is horizontal in its figure, lies near the earth, and its length is usually greater than its breadth.  It floats in long bands with rounded or sharpened points, and is seen rising from rivers or lakes, at first as a fog.  In the morning it indicates fine weather.  The Fall Cloud never discharges rain.