Very little study appears to have been given the soils of Algeria. It has been stated that there are vast areas of light, sandy soils, and also extensive tracts of marls, clays, and alluvial soils.[1] Gypsum is an important element in the soils, both those of the oases and probably of the open desert also; it occurs in great quantity in the large chotts of the desert, along with common salt and other salts. In the soils of the oases it acts as a cementing material, “uniting the finer soil-grains into aggregates which give the soil a much more sandy appearance than would be suspected from the results of mechanical analysis.” At Laghouat and at Ghardaia a light-colored, hard substance, closely resembling the “caliche” of the southwestern United States, was seen incrusting stones, filling cracks in rocks and crevices between rocks, and in places forming a stratum, horizontally placed (15 cm. more or less in thickness) underneath the superficial soils. This is extremely hard and can be broken or cut with difficulty. In the valley of the M’Zab, where it constitutes a heavy substratum, it appears to be impervious to water. This hardpan is used as threshing floors by removing the superficial soils. An unexpectedly small amount of sand was observed over the route traversed. Near the southern edge of the High Plateau a sand belt was encountered and a long stretch of low dunes was seen leading to the eastward, which were said to reach nearly to Bou Saada; and again at Laghouat there are dunes to the east of town as well as to the west. Low dunes were seen in the valley of the Oued M’Zab, and sand mountains, possibly 250 meters high, were passed on the way from Ghardaia to Ouargla. Between Ouargla and Touggourt, also, sand was encountered and the way lay across about 12 miles of low dunes; to the north of Touggourt dunes are also to be seen; and finally, some sand is to be found in the neighborhood of Biskra. Although, thus, relatively little sand was met, much of the entire portion of southern Algeria is covered by sand. Large areas of sand-covered country lie to the east of the Oued Rirh, and especially southeast of Touggourt, and also to the west of Ghardaia there is said to be a large dune-covered territory. For the most part, however, the surface of the plains crossed is covered with large or small stones, mingled with which, or beneath which, there is a rather fine clay-like soil. This constitutes the hamada, or stony desert, of which the largest portion of the surface of the Sahara is probably composed. Where stones are largely absent and the soil is fine, usually of fluvian origin, the formation is known as “reg.” Reg desert was encountered at and north of Ouargla, in the drainage of the Igharghar or its tributaries, and south of Biskra. The latter may not, strictly speaking, be reg, but a wide-stretching bajada, and the soil is probably only in small part deposited by rivers. =CLIMATE OF ALGERIA.=