Saussure, in describing the route from Geneva to Chamouni, mentions many remarkable instances of the bending of the strata, and particularly where the small stream of Nant d'Arpenaz forms a cascade, by falling over the face of a perpendicular limestone rock. The strata of this rock are bent into circular arches, extremely regular, and with their concavity turned to the left. What deserves particularly to be remarked, is, that a mountain behind the cascade has its strata bent in a direction opposite to the former, or with their concavity to the right. There is no doubt that the strata of both rocks are the same, so that a vertical section of them would give a curve, in the figure of an S.[99] These circumstances are mentioned by Saussure, and from them we may infer this other property of these strata, that their section by a horizontal plane, must exhibit a system of straight lines, probably all parallel to one another. [Footnote 99: Voyages aux Alpes, vol i. § 472; also, Theory of the Earth, vol. ii. p. 30.] The same mineralogist describes the calcareous strata which compose the mountain Axenberg, on the side of the Lake of Lucerne, as having from top to bottom of the mountain the form of the letter S compressed, (_ecrasée_) with their curvature in some places very great. These inflections are repeated several times, and often in contrary directions; the layers are sometimes broken, where their curvature is greatest.[100] [Footnote 100: Voyages aux Alpes, tom. iv. § 1935.] On the side of the same lake, is another instance of bent strata, in a mountain, of which the beds are horizontal in the lower part, but are bent at one end upwards, in the form of the letter C. The horizontal part is of great extent, and the rock is also calcareous,[101] [Footnote 101: _Ibid._ § 337.] The Montagne de la Tuile, near Montmelian, receives its name from the beds of rock being incurvated in form of a tyle.[102] Among secondary mountains, the same kind of phenomena are observed, though less frequently, and with less variety of inflection. The chain of Jura is secondary, and the beds which compose it are of limestone, or of grit: they are bent in such a manner, that in a transverse section of the mountain, each layer would have the figure of a parabola.[103] [Footnote 102: _Ibid._ vol. iii. § 1182, and plate i.] [Footnote 103: _Ibid._ tom. i. § 334.] 201. The Pyrenees furnish abundance of phenomena of the same kind, as we learn from the _Essai sur la Mineralogie des Pyrenées_. The calcareous strata of the valley of Aspe, represented plate v. of that work, deserve particularly to be remarked.