Among other manuscript notices of M. Fournel, I possess a vertical geological profile, which gives all the inflexions and inclinations of the strata, representing a section of the surface the whole way from Philippeville on the coast to the Desert of Sahara, at a spot not far from the Oasis of Biscara. The direction of the line on which the barometric measurements were taken is south 20° west; but the elevations determined are projected, as in my Mexican profiles, on a different plane,--a north-south one. Ascending uninterruptedly from Constantine, at an elevation of 332 toises (2122 Eng. feet), the culminating point is found between Batnah and Tizur, at an elevation of only 560 toises (3580 Eng. feet). In the part of the desert situated between Biscara and Tuggurt, Fournel has had a series of Artesian wells dug with success (Comptes Rendus de l’Acad. des Sciences, t. xx. 1845, p. 170, 882, and 1305). We learn from the old accounts of Shaw, that the inhabitants of the country knew of a subterranean supply of water, and relate fabulous tales of a “sea under the earth (bahr tôht el-erd).” Fresh waters flowing between clay and marl strata of the old cretaceous and other sedimentary deposits, under the action of hydrostatic pressure form gushing fountains when the strata are pierced (Shaw, Voyages dans plusieurs parties de la Berbérie, t. i. p. 169; Rennell, Africa, Append. p. lxxxv). That fresh water in this part of the world should often be found near beds of rock salt, need not surprise geologists acquainted with mines, since Europe offers many analogous phenomena.