overmastered all difficulties may be seen in the Valley of Ceyssac. The rill flows into the Borne at an acute angle against the current. The valley was choked with a mass of tufa ejected from La Denise, and the current was arrested in its downward course. The stream then formed a lake that rose till it overflowed the dam in two places, leaving between them a prong of somewhat harder rock. When the water had poured for a considerable time over the left-hand lip, and it had worn this down to the depth of about seventy feet, it all at once abandoned this mode of outlet and concentrated its efforts on the right-hand portion of the barrier, where it found that the tufa was less compact, and it sawed this down till it reached its present level, leaving the prong of rock in the middle rising precipitously out of the valley with the water flowing below it, but attached to the mountain-side by the neck it had abandoned. The Polignacs seized on the fang of tufa and built a castle on the top, only to be reached by steps cut in the face of the rock; and the villagers covered the neck with their houses. They then proceeded to scoop out a great vault in the body of the living rock, blocked the entrance with a wall in which is inserted a pretty Romanesque doorway, and so provided themselves with a parish church at very little expense. On a saddle overhead they constructed a belfry for three bells.
In no part of Europe can be studied with greater facility the process of valley formation, for here that process is comparatively recent. That which has been accomplished elsewhere in hundreds of thousands of years, has here been achieved in thousands only. The great elevation of the valley, and the fact that it lies open to the north cause it to be a cold country. The
