In the second layer there were found the remains of the mammoth, rhinoceros, cave-bear, cave-hyena, cave-lion, reindeer, and seven other species. Indiscriminately mixed with these bones were found many flint knives, but chiefly from the lowest part of the ochreous cave-earth, varying in depth from ten inches to thirteen feet. The antiquity of these cannot be doubted, from the simple fact, even if there was no other, that in close proximity to a very perfect flint tool was discovered the entire left hind leg of a cave-bear, and every bone in its natural position. From the bone earth there were taken fifteen knives, recognized, by the experienced antiquaries, as having been artificially formed. In the lowest gravel, underlying all, there were found imperfect specimens of flint knives. The fine layer of mud was deposited by the slow but regular action of water. Since these layers were formed the stream has cut its channel seventy-eight feet below its former level.[18] On both banks of the Meuse, at Maestricht (Hollerd) are terraces of gravel covered with loess. Below the city, on the left bank, one of these terraces projects into the alluvial plain of the Meuse. During the construction of the canal the terrace was opened to a depth of sixty feet. The upper twenty feet consisted of loess and the lower forty feet of stratified gravel. Great numbers of molars, tusks, and bones of elephants, together with those of other mammalia, and a human lower jaw with teeth, were found in or near this gravel. The human jaw was at a depth of nineteen feet from the surface, in a stratum of sandy loam, beneath a stratum of pebbly and sandy beds, and immediately above the gravel. The stratum from which the jaw was taken was intact and had never been disturbed. But the jaw was somewhat isolated, and the nearest fossil object was the tusk of an elephant six yards distant, though on a horizontal plane. This fossil is probably older than that discovered at Lahr. It was probably covered just before the gush of the water when it first began to flow from the gorges and had washed the ground at some distance from the ice.[19] The human skeleton from the undisturbed loess of the Rhine, near Lahr, was found in nearly a horizontal position, but in such a manner as to forbid the idea of sepulchre. These bones were exhumed from a perpendicular cliff of solid loess, about five feet high. The town of Lahr is situated four miles from, and about one hundred feet above, the Rhine, and not far from the tributary valley drained by the Schutter, flowing from the Black Forest.