CHAPTER IV.
THE GRAND BARGE D’OLONNE.
A.D. 1861.
We must not take leave of French oceanic lighthouses—that is, of lighthouses built out at sea—without a brief reference to that of the Grand Barge d’Olonne. Situated on a rock of shoal about 1.134 nautical miles from the shore, in a situation surrounded by obstacles of every kind, where the currents are excessively violent, and where the tempests so disturb and madden the sea as to render nugatory all known methods of construction, this lighthouse does the greatest honour to its architects.
Its foundation is almost completely submerged, and during high tides the waves leap to a height, it is said, of 100 feet.
The work was undertaken in 1857, and completed in 1861; but such were the difficulties offered by the nature of the locality, that in these five years only one thousand nine hundred and sixty hours could be devoted to consecutive labour. Yet, so familiar are now the principles on which edifices of this nature must be constructed, or—to speak more justly—so confident in their own resources are the engineers who devise and erect them, that even this comparatively brief period proved amply sufficient.
The entire cost of the work was 450,000 francs, or £18,000. It was executed under the direction of M. Reynaud, inspector-general, and M. Forestier, engineer-in-chief. The tower is built of granite, the stones of the face being mortised and tenoned together; its diameter at the base is 39.37 feet, tapering with a curved outline to 21.23 feet at the upper part. The door-sill is 13.12 feet above high-water mark of the highest tides, and up to this level the tower, with the exception of a cellar for coal and fresh water, is solid. Above the level the tower is hollow, with an internal diameter of 11.48 feet, and is divided into five stories by vaults of brick. The tower has a stout cornice and parapet of granite. From the centre of its platform rises the turret, 6.56 feet high, and 8.2 feet in internal diameter, which supports the lantern. The internal diameter of the catadioptric illuminating apparatus is 3.28 feet, and gives a white light with red flashes every three minutes.
The rocky peak on which the “Phare des Barges” stands, rises about one and a half foot above low water of ordinary spring-tides; but at low water of neap-tides is covered to the depth of about two feet and a half.
It is situated to the westward of the port of Sables-d’Olonne.