ARTESIAN FOUNTAINS, or AR TESIAN WELLS. (Fr. Puits Artaiens.) Vertical perforations of the exterior crust of the earth, of small diameter, and fre quently of great depth, through which subterraneons water arises to the sur face, often forming abundant and ele vated jets. The name Artesian is derived from Artois, a province of France, where especial attention has been given to this means of obtaining water ; but it ap pears, from sufficient historical evidence, that wells of this kind were perfectly well known to the ancients. Niebuhr cites a passage from Olympiadorns, who flourished at Alexandria about the mid dle of the sixth century, in which it is stated that when wells are dug in the Oasis to the depth of two hundred, three hundred, or sometimes five hundred yards, rivers of water gush out from their orifices, of which the agriculturists take advantage to irrigate their fields. The oldest Artesian well known to exist in France is in the ancient convent of the Chartrenx, at Lillers in Artois. It is said to have been made in 1126. Others exist at Stuttgart, of great antiquity, though their dates cannot be fixed with pre cision. The inhabitants of the great de sert of Sahara appear also to have been long acquainted with this mode of ob taining water, and the Chinese are said (but the truth of the statement is ques tionable) to have practised it for thou sands of years.
Various conjectures have been made as to the source of the water which comes from the Artesian wells. It was long believed that the water of the sea must necessarily penetrate by way of infiltra tion into the interior of the continents, and at length form large bodies of sub terraneous waters, which, excepting for capillary influences, wofild not rise above the general level of the ocean. Another opinion, maintained by Aristotle, Seneca, Carden, and even Descartes, was, that the subterrancous water, from which the sources of rivers and springs are sup plied, is the product of the condensation of aqueous vapors ascending from the interior parts of the earth in consequence of the central heat. But these hypo
theses are founded on mere conjecture, unsupported by the slightest evidence, and consequently merit no attention. The simplest and most natural explana tion is, that the water of wells, of Artesian fountains and rivers, is sup plied by the rain which falls on the sur face at a higher elevation, and which penetrates through the pores and fissures of the ground till it meets with some im permeable stratum, or is collected in subterranean reservoirs. It has been objected that springs are sometimes situ ated on or near the summits of moun tains, which could not be supplied in this way ; but on an attentive examina tion of all the circumstances—that is to say, on measuring accurately the extent of surface at a greater elevation than the spring, and comparing it with the quan tity of rain that falls annually in the same climate, it has been found, in every instance, that the aqueous deposition from the atmosphere exceeds the supply from the spring. It is computed that not more than a third part of the rain which falls in the valley of the Seine is conveyed to the sea by the river ; the remaining two-thirds support vegetation, supply fountains and springs, or are re turned to the atmosphere by evapora tion. The immense bodies of water which some continental rivers roll towards the ocean are but a small part of the rain which falls in the surrounding countries.
The average fall of rain in these lati tudes is about 40 inches of rain, or about 3,500 tons of water deposited in the course of the year on every acre. In sandy districts this rain-water penetrates like as through a sieve. In mines sunk in limestone rocks the water increases in the galleries very remarkably after a fall of rain.
Assuming, then, that the subterra neous water is supplied from atmospher ical deposition, it remains to be explained how it arrives at the situation it occupies in the interior of the earth, and by what forces it is raised from great depths to the surface.