In all probability the stones used were conveyed to the required spot by means of canoes made of hollowed-out trunks of trees. Several of these canoes may still be seen at the bottom of Lake Bienne, and one, indeed, is still laden with pebbles, which leads us to think that it must have foundered with its cargo. But it is very difficult to raise these canoes from the bottom, and it is, besides, probable that when exposed to the open air they would fall to dust. Nevertheless, one of them is exhibited in the Museum at Neuchâtel. In the Museum at Saint-Germain there is a canoe very similar to that of Neuchâtel. It is made out of the trunk of a hollow tree. A second canoe, very like the first, but with the bark still on it, and in a bad state of preservation, lies in the entry of the same Museum of Saint-Germain. It was taken out of the Seine, as we stated when speaking in a previous chapter of the first discovery of the art of navigation during the Stone Age. It may very easily be explained how the constructors went to work in felling the trees and converting them into piles. M. Desor has remarked that the pieces of wood composing the piles are cut cleanly through round their circumference only; the central part shows inequalities just like those which are noticed when a stick is broken in two by the hand after having been cut into all round the outside. The builders of the lacustrine villages, therefore, when they wanted to fell a tree must have acted much as follows: having cut all round it to a depth of 3 or 4 inches, they fixed a cord to the top, and broke the tree down by forcibly pulling at the upper part. They then cut it through in the same way with stone or bronze hatchets, giving it the requisite length, hewing it into a point at one end so that it should more easily penetrate the mud. Sometimes a fire applied to the base of the tree prepared for, and facilitated, the effect of the sharp instruments used. A great number of the piles that have been found still bear the marks of the fire and the cuts made by stone hatchets. In constructing the _ténevières_, the labour of pointing the piles was needless, as the latter were thoroughly wedged in by the accumulation of stones of which we gave a representation in fig. 148. When the piles were prepared, they had to be floated to the spot fixed upon for the village, and to be fixed in the bed of the lake. If we consider that, in many cases, the length of these piles reached to as much as 16 or 20 feet, some idea may be formed of the difficulty of an undertaking of this kind. In the construction of the _ténevières_ much thicker piles were used, and the labour was much less difficult. For instance, in the more ancient _ténevières_ of the Lake of Neuchâtel piles are found made of whole trunks of trees which measure 10 to 12 inches in diameter.