This river no doubt owes its origin to the superfluous waters of the Lake of Brenets, which have no visible outlet, and sink into fissures and _entonnoirs_ in the rock at the edge of the lake.

Notwithstanding that the lake is three-quarters of a league distant, horizontally, and nearly 700 feet higher, the belief had always been that it was the source of the stream, and in 1776 this was proved to be the fact.

For some years before that date, the waters of the Lake of Joux had been inconveniently high, and the people determined to clean out the _entonnoirs_ and fissures of the Lake of Brenets, which is only separated from the Lake of Joux by a narrow tongue of land, in the expectation that the water would then pass away more freely.

In order to reach the fissures, they dammed up the outlet of the upper into the lower lake; but the pressure on the embankment became too great, and the waters burst through with much violence, creating an immense disturbance in the lake; and the Orbe, which had always been perfectly clear, was troubled and muddy for some little time.

The source of the Loue, near Pontarlier, is more striking than even that of the Orbe.[25] FOOTNOTES: [Footnote 21: A point common to the two sections, which are made by planes nearly at right angles to each other.] [Footnote 22: The dimensions of the two caves, and of the various masses of ice.] [Footnote 23: The Cartulary of Lausanne states that the wealthy village of Biere received its name from the following historical fact:--In 522, the Bishop of Lausanne, S.Prothais, was superintending the cutting of wood in the Jura for his cathedral, when he died suddenly, and was carried down on a litter to a place where a proper _bier_ could he procured, whence the place was named Biere.] [Footnote 24: The most curious pit of this kind is the _frais-puits_ of Vesoul, in the Vosgian Jura, which pours forth immense quantities of water after rain has fallen in the neighbourhood.