Sometimes several weeks passed, load after load being dropped in, before the mass was of sufficient size to rise above the water.  After having been left some time to consolidate, the summit was capped by blocks of hewn stone, rising from low-tide mark to many feet above that of high-water, so that the sea during the fiercest gale could not force its way over it.  The piles to support the stage were what are called screw piles; they were ninety feet in length, and soaked in creosote to preserve them, the weight of each being about seven tons.  One of the most curious operations was that of forcing the creosote into the piles. It was done by placing them in an iron cylinder one hundred feet in length, and six feet in diameter.  Out of this the air was first pumped, and then the creosote was pumped in.