When warmer air-currents are cooled by being transported into colder regions, or from any other refrigerating cause, a great part of their moisture generally condenses into small vesicles, but very little heavier than the surrounding atmosphere, which then becomes visible under the form of clouds, those great beautifiers of our changing skies, that frequently trace such picturesque, gorgeous, or singular groups and landscapes in the aërial regions. The inhabitants of countries where the heavens are monotonously serene, may well envy us the charms of a phenomenon which in some measure affords us compensation for so many disagreeable vicissitudes of the weather. Who that has admired at sunset the light clouds so beautifully fringed with silver and gold, or glowing with the richest purple, and loves to follow them in all their wonderful and fantastic transformations, will deny that they are the poesy and life of the skies, the awakeners of pleasing fancies and delightful reveries?
Thin wreaths of clouds have been observed, by travellers that have ascended the most elevated mountains, floating high above the peak of Chimborazo or Dhawalagiri, and thus shows us to what an amazing altitude the emanations of ocean are carried by the ascending air-current.
Sometimes when light clouds pass into a warmer atmosphere, they gradually dissolve and vanish; more frequently the accumulating moisture, too heavy to continue floating in the air, or condensed by electrical explosions, descends upon the earth in rain, which, with few exceptions, visits every part of the globe, either in its liquid form or congealed to snow or hail. But the quantity of rain which annually falls in different regions is very unequal, and strange to say, it is not most considerable in those countries whose climate enjoys an unenviable notoriety for its clouded atmosphere and the great number of its rainy days. In the tropical regions it is generally only about the time of the summer solstice that abundant showers of rain fall regularly every afternoon, while the rest of the year, the sky is uninterruptedly serene; but during the short period of the rainy season, a far greater quantity of water is precipitated upon the earth, than in the temperate zones.
While on the island of Guadaloupe, the annual quantity of rain amounts to 274·2 French inches, and to 283·3 at Mahabuleshwar, on the western declivity of the Ghauts, which, as far as has hitherto been ascertained, is the place where most rain descends; only from 35 to 40 inches fall on the western coast of England, where the skies are chronically weeping.
It is a remarkable circumstance that the annual quantity of rain which falls in the same place remains about the same from year to year; so that by an admirable balancing of conflicting influences, nature seems to have provided for stability in a province which of all others might be supposed most open to the caprices of chance.
Having thus followed the exhalations of ocean to the end of what may be called the first stage of their journey, and seen them descend in a condensed form upon the surface of the dry land, I will now accompany them in their ulterior progress to the bosom of the seas. A great part of them have many transformations and changes to undergo ere they can accomplish their return; repeatedly rising in vapours from the solid earth, and falling in showers upon its surface; or circulating through the tissues of organic life: but after all these intermediate stages and delays, they ultimately find their way into rivulets or streams, which after many a meander restore them to the vast reservoir from which they arose.
The waters that descend upon solid rocks, or fall in large quantities upon abrupt declivities, immediately flow into the brooks or rivers; but when they gently and gradually alight upon a porous soil, they are absorbed by the earth, and, displacing in virtue of capillary attraction, and of their superior weight, the air which fills the interstices between its solid particles, sink deeper and deeper until they meet with a solid and impenetrable stratum. If this forms a hollow basin, they naturally settle in the cavity; whence they are slowly displaced by fresh accessions and evaporation; but if its deepest declivity lies somewhere near the surface, they gradually gush forth under the form of sources or springs, having unequal distances to perform before they can reach the orifice. If no fresh supply of water falls, ere the most distant particles have reached their journey's end, the source dries up: but if new atmospheric precipitations continually take place, the source is perennial, although naturally of unequal strength at different times.
The temperature of springs varies from icy coldness to boiling heat. Cold springs arise when the waters, by which they are fed, descend from high mountains or do not penetrate a great way into the bowels of the earth; but if the filtering waters reach a depth which is constantly of a higher temperature, they then gush forth in the form of warm or even boiling springs.
A crowd of agreeable associations attaches itself to the idea of sources and springs, for they are generally both pleasing and useful to man. How we long in summer for the refreshing waters of the cool fountain issuing from the mountain side, and murmuring through the woods. The lover of nature spends hours near some solitary spring, and forgets the flow of time, as he observes the bubbling and listens to the sweet music of its crystal waters. A luxuriant vegetation marks their progress, though all around be burnt up by the scorching sun. Along their margin many a wild flower blooms, and herbs and shrubs and trees rejoice in a more vivid green, and statelier growth. There also congregate such members of the finny race, as delight in cooler streams of untainted purity, and birds love to build their nests among the sheltering foliage. Thus a little world forms around the gushing spring, and shows on a diminutive scale, how all that lives and breathes depends upon the liquid element for its existence.