BOATS OF ARTIFICIAL STONE
Originally wood was used for the hulls of ships; then between 1845 and 1855 iron supplanted wood, Between 1875 and 1885 steel supplanted iron and to-day efforts are being made to supplant steel with concrete. The advantages offered by concrete are cheapness and speed of construction. The first large vessel built of this material was the Faith, an 8,000-ton ship. This boat stood up very well in heavy weather despite the rigidity of her structure. It is doubtful, however, that a large boat comparable in size to the Leviathan could weather a severe ocean storm.
The proposal to build ships of cement created almost as much of a popular sensation as did the first iron boat. Although the public had accepted iron and then steel as a perfectly proper material for shipbuilding, concrete seemed too much like stone and it did not seem possible that artificial stone could be made to float. They did not realize that a cubic foot of steel weighs four times as much as the same volume of concrete. Of course concrete does not begin to have the tensile strength of steel and consequently the walls of a concrete ship must be made relatively thick. For this reason a concrete vessel is heavier than a steel vessel. She draws more water and requires a larger power plant, and because of her greater mass she is not so readily maneuvered.