The property of cords contracting their length by moisture became generally known, it is said, on the raising of the Egyptian obelisk in the square facing St. Peter's, at Rome, by order of Pope Sixtus V. The great work was undertaken in the year 1586, and the day for raising the obelisk was marked with great solemnity. High mass was celebrated at St. Peter's, and the architect and workmen received the benediction of the Pope. The blast of a trumpet was the given signal, when engines were set in motion by an incredible number of horses; but not until after fifty-two unsuccessful attempts had been made, was the huge block lifted from the earth. As the ropes which held it had somewhat stretched, the base of the obelisk could not reach the summit of the pedestal, when a man in the crowd cried out, "Wet the ropes!" This advice was followed, and the column, as of itself, gradually rose to the required height, and was placed upright on the pedestal prepared for it.