It is certain that none of these port works will ever fail by reason of insecure foundations. Wherever unusual loads were to be carried great piers of reinforced concrete were sent down to solid rock, often a distance of 60 feet below the surface. They consisted of a hollow shell of reinforced concrete which was allowed to sink to hardpan of its own accord or under heavy weight. These shells were built in sections 6 feet high. The bottom section was 10 feet in diameter, and the lower end was equipped with a sharp steel shoe. As the section cut down into the earth of its own weight and that above it, laborers on the inside removed the material under the shoe and as they did so it sank further down. The sections above were only 8 feet in diameter, and did not quite fill up the hole made by the bottom of the section, thus overcoming all skin friction, and permitting the full weight of the series of sections to fall on the lower one. A jet of water was forced around the sinking pier all the time it was going down, and this made its progress the more easy. At times the weight of the superimposed sections was sufficient to force the pier down through the soft mud, while at other times the material became so heavy that even a 25-ton weight on top of the pier scarcely moved it. At one place a stratum of material was struck about 25 feet below the surface which yielded sulphuretted hydrogen gas. This affected the laborers' eyes, and some of them had to go to the hospital for treatment. The work of digging out the material was continued until the lower section reached bed rock, where it was anchored. The sections themselves were tied together with heavy iron rods. After they were firmly in place the interior was filled up with concrete, itself reinforced, so that the foundations became, in reality, a series of huge concrete piles, 8 feet in diameter, anchored to bed rock.