Every day, as soon as the tide had ebbed, the artificers repaired to work, and the hours for meals were so arranged that no interruption took place while the tide lasted. When the rising waters forced them to abandon the rock, a bell gave the signal. They then hastened to cover with a cement which hardened instantaneously the portions of masonry which had just been finished, and took refuge in their abodes. Sometimes, however, it would happen that the sea rose with unusual rapidity; woe, then, to the tardy! They had no other resource but to throw themselves into the water before its depth became dangerous; an amusement for the on-lookers, and almost their only one. Thanks to these measures of order and supervision, the engineer had not to regret the loss of any of the members of his laborious little colony; although, during the course of their works, many ships, and, still more unfortunately, several visitors, perished. * * * * * Let us now say a few words respecting the work itself. The principal difficulty of the operation consisted in erecting the submarine portion of the building. Once the level of high-water mark was reached, the men could not only carry on their labours more conveniently, but were relieved from the most critical chances. Thenceforth they had nothing further to do with the sea than as regarded the process of landing, and to a certain extent they built upon an island. But on this artificial island everything depended, and in its formation every precaution had to be studied. The rock on which the lighthouse rests consists of an extremely hard and resistant black porphyry. Nevertheless, as in some places it showed numerous fissures, the work began with the removal of all the superficial part, so as to secure a properly sound basis; and as, at the same time, it was of great importance that the foundation should never be exposed, M. Reynaud adopted the necessary measures to sink it completely in the rock. With this view, an annular surface of 38 feet in diameter, destined to support the hewn stone work, was excavated in the porphyry to a depth of about twenty inches, and dressed with the utmost exactitude; a labour of excessive difficulty on account of the tenacity of the rock, but a certain safeguard against future danger. In the groove thus protected by the whole mass of porphyry were deposited the first courses. As for the part of the rock corresponding to the interior of the tower, no special necessity for extra precautions existing in respect to it, it was left in its rough state, with simply a layer of concrete. * * * * *