Another calculation, the conclusions of which agree tolerably well with these, was made by M. Gilliéron, professor at the college of Neuveville. We have already said that the remains of a pile-work belonging to the Stone Age was discovered near the bridge of Thièle, between the lakes of Bienne and Neuchâtel. It is evident that the valley, the narrowest part of which was occupied by the lacustrine settlement, was formerly almost entirely under water, for below this point it suddenly widens out and retains these proportions as far as the lake of Bienne. The lake must, therefore, have retired slowly and regularly, as may be ascertained from an examination of the mud deposited by it. If, therefore, we know its annual coefficient of retreat, that is to say, how much it retired every year, we should be able to estimate with a sufficient degree of approximation the age of the settlement of the bridge of Thièle. Now there is, not far from the lake, at about 1230 feet from the present shore, an old abbey, that of Saint-Jean, which is known to have been built about the year 1100. A document of that time mentions that the cloister had the right of fishing in a certain part of the lake; and there is some likelihood that it was built on the edge of the lake; a supposition which naturally presents itself to the mind. The lake, then, must have retired 1230 feet in 750 years. This granted, M. Gilliéron easily calculated the time which would be taken for a retreat of 11,072 feet, this number representing the distance from the present shore to the entrance of the defile which contains the settlement of the bridge of Thièle. He found by this means that the settlement is at least 6750 years old, a figure which confirms those of Morlot. The preceding calculations assign to the Stone Age in Switzerland an antiquity of 6000 to 7000 years before the Christian era, and to the bronze epoch an antiquity of 4000 years before the same era. There is still much uncertainty in the figures thus given to satisfy public curiosity; but there is at least one fact which is altogether unquestionable--that these calculations have dealt a fatal blow to recognised chronology. FOOTNOTE: [38] 'Le Danemark à l'Exposition Universelle de 1867, by Valdemar Schmidt,' vol. i. pp. 60-64. Paris, 1868. II. THE IRON EPOCH. CHAPTER I. Essential Characteristics of the Iron Epoch--Preparation of Iron in Pre-historic Times--Discovery of Silver and Lead--Earthenware made on the Potter's Wheel--Invention of Coined Money.