The rock of Ceyssac is curious. Formerly a barrier of volcanic tufa stretched across the valley of the Borne; this barrier had been ejected from the volcano of La Denise. The river, arrested in its onward course, was ponded back and formed a lake that overflowed the dam in two places, leaving between them a fang of harder rock. When the water had spilled for a considerable time over the left-hand lip, and had worn this down to a depth of about 70 feet, it all at once abandoned this mode of outlet and concentrated its efforts on the right-hand portion of the dam where it found the tufa less compact. It eventually sawed its way completely through till it reached its present level, leaving the prong of rock in the middle rising precipitously out of the valley with the river gliding peacefully below it, but attached to the mountain side by the neck it had abandoned. The fang was laid hold of, burrowed into, and converted into a village of Troglodytes. In it are cave-dwellings in five superposed storeys, stables with their mangers, with rings for tying up cattle, a vast hall, that is circular, and chambers with lockers and seats graven out of the sides of the walls. There is also a subterranean chapel, with the entrance blocked by a wall that contains an early Romanesque doorway. The Polignacs seized on the spike of rock and built on the summit a castle that could be reached only by a flight of steps cut in the face of the rock. By degrees the inhabitants have migrated from their caves to the neck of land connecting the prong with the hill, and have built themselves houses thereon. They have even abandoned their monolithic church and erected in its place an unsightly modern building. There are other cave-dwellings in the volcanic rocks of the Cevennes and Auvergne, but the above account must suffice. I will now say something about the Troglodyte dwellings in the sandstone in Corrèze, in the neighbourhood of Brive, caves that have been inhabited from the time of the man who was contemporary with the mammoth, to this day. Some have, however, been abandoned comparatively recently. They do not run deep into the rock; usually they face the south or south-west, and are sometimes in a series at the same level; sometimes they form several storeys, which communicated with each other by ladders that passed through holes cut in the floor of the upper storey, or else by a narrow cornice, wide enough for one to walk on. Sometimes this cornice has been abraded by the weather, and fallen away; in which case these cave-dwellings can be reached only by a ladder. There are caves in which notches cut in the rock show where beams had been inserted, and struts to maintain them, so as to form a wooden balcony for communication between the chambers, or between the dwellings of neighbours.