ATLAS is the historical and geographical name of an extensive mountain-system in North Africa, which, though not inhabited by a manufacturing race, produces many sub stances useful in the Arts. On the low plains at the southern foot of the mountains, and within its lower ranges, the date palms cover extensive tracts ; the higher lands abound in gum trees, almonds, olives, and other produc tions of the hotter countries ; the lower table lands produce apples, pears, cherries, walnuts, apricots, and other fruits, common to the southern countries of Europe; and, proceeding higher up the ranges, the plains are covered with pines of an immense size, with a species of oak, called the belute, with ferns, elms, mountain ash, and several species of juniper. Higher up, large forests of firs form the prin cipal vegetation.
Rich mines of different kinds exist in that Lateral range which separates the province of Suse from the countries on the river Draha ; it abounds especially in iron, copper, and lead. Ketewa, a district east of Tarudaut, contains rich mines of lead and brimstone ; and salt petre of a superior quality abounds in the neighbourhood of Tarudant itself. Other mines of iron, copper, antimony, lead, and a Little silver and gold, are met with in various parts. Salt and sulphur are also found. ATMOMETER, an instrument employed to measure the quantity of exhalation from a humid surface in a given time. The instru
ment to which the name is usually applied is one invented by Professor Leslie, consisting of a very thin ball of porous earthenware, two or three inches in diameter, to which is ce mented a long tube of glass, marked by a dia mond with divisions, each of which is capable of containing as much liquid as would, if spread over the outer surface of the ball, cover it with a film equal in thickness to the part of an inch. The open end of the tube is fitted with a brass cap and a leather collar; and when in use the instrument is filled with distilled or boiled water, and suspended verti cally with the ball downwards, the end of the tube being perfectly closed with the cap and collar. The water then percolates through the porous ball precisely in proportion to the evaporation from its outer surface, of which its waste in the tube forms an accurate indica tion. The vacuous space above the water in the tube becomes, during the operation, gra dually filled with air which enters through the porous ball. When the tube becomes empty, the cap is removed to refill it. This instru ment is not only useful in meteorological ob servations, but is also capable of being applied with advantage in chemical operations, and in the application of science to agriculture.