It was a queer craft, the like of which no man had ever seen, in which Ezra Lee embarked one dark night in August, 1776, with the firm intention of destroying the pick of the British fleet. Its shape suggested a turtle or rather two upper turtle shells, securely fastened together. A brass crown, resembling a hat, represented the head of the turtle; it was provided with glass windows, which supplied light while the boat was on the surface, and with several round doors, which were opened before submersion for the admission of air. The turtle rested in the water with its tail downwards, being held in position by a permanent lead ballast in the hold of 500 pounds. This was supplemented by 200 pounds of the same metal, which could be released at the will of the navigator, enabling him to rise suddenly to the surface. The turtle was made of oak, put together in the strongest manner; it was seven and one-half feet long and six feet high. It admitted only one person, who had room enough either to stand up or sit down. There were two air-tubes, one for letting the fresh air in and another for letting the foul air out. These were ingeniously arranged so that they operated whenever the boat was brought to the surface and closed immediately after it was submerged. There were no means of generating or supplying air while the contrivance was under water. Sufficient atmosphere to last the operator thirty minutes was supplied before the trial began, after the exhaustion of which he was obliged to rise to the surface.