Several attempts have been made to estimate the time which has elapsed since the neolithic period. The estimates of M. Morlot are based on the discoveries made in a hillock formed by the river Tinière at its entrance into the lake of Geneva. This cone contained three distinct layers of vegetable earth placed at different depths between the deposits of alluvium. The first was at a depth of three and one-half feet from the top, and was from four to six inches thick, and in it were found relics of the Roman period; the second was five and one-fourth feet lower, and six inches thick, in which were fragments of bronze; the third was at a depth of eighteen feet from the top, and varied in thickness from six to seven inches, and contained fragments of the stone age. History proves that the layer containing the Roman relics is from thirteen to eighteen centuries old. Since that epoch the cone has increased three and one-half feet, and if the increase was the same in previous ages, then the bed containing the bronze is from twenty-nine hundred to forty-two hundred years old, and the lowest layer, belonging to the stone age, is from four thousand seven hundred to ten thousand years old. The calculation by M. Gillieron was made from the discoveries near the bridge of Thièle. About one thousand two hundred and thirty feet from the present shore is the old abbey of Saint Jean, built in the year 1100. There is a document which seems to show that the abbey was built on the edge of the lake. Then, in seven hundred and fifty years the lake retired one thousand two hundred and thirty feet. The distance of the present shore from the settlement of the bridge of Thièle is eleven thousand and seventy-two feet, and consequently the settlement is not less than six thousand seven hundred and fifty years old. M. Figuier assigns to the lake-dwellings an antiquity of from six to seven thousand years before the Christian era.[74] CHAPTER XI. MAN OF THE NEOLITHIC. From the human bones found in peat-bogs and tumuli, man is represented as having a narrow but round skull, with a projecting ridge above the eyebrows, showing he was round-headed, his eyebrows overhanging, small of stature though stout, and having a great resemblance to the Laplanders. In many respects the race was much superior to that of the preceding epoch. Man advanced rapidly in the arts, and made great progress in civilization. He had passed out of the barbarous, and might be called a semi-barbarian. _Habitations._--Man's habitation varied according to the locality. In the extreme south of France he continued for a considerable length of time to occupy the caves and rock-shelters; in Switzerland, the pile-buildings, and in Denmark he undoubtedly had rude huts placed close together and in proximity to the shell-heaps.