It has been stated already that there are fixed rules of weather, or, which is the same thing, that there are laws governing the motion of the winds; but we have added also, that there are a great many causes which disturb these rules, and therefore make any calculations in advance a sheer impossibility.
We have seen that these rules are called forth, 1st, by the course of the sun; 2d, by the circulation of the air from the poles to the equator and back again; and 3d, by the revolution of the earth, causing the trade-winds.
All these various items have been calculated correctly; and, owing to this, we have now a firm basis in meteorology. But in the next article, we shall see what obstacles are put in the way of this new science by other things; and the allowances to be made for these disturbances cannot be easily computed.
CHAPTER V.
AIR AND WATER IN THEIR RELATIONS TO WEATHER.
Let us now examine the causes which disturb the regular currents of air, and which render the otherwise computable winds incomputable, thus producing the great irregularities of the weather.
The main cause lies in this, that neither the air nor the earth is everywhere in the same condition.
Every housewife that but once in her life hung up clothes to dry, knows full well that air absorbs moisture when passing over, or through, wet objects. If she wishes to dry her clothes very quickly, she will hang them up where there is much wind. And she is perfectly right in maintaining that the wind dries clothes better than the quiet sunshine.
Whence does this come?