A distinctive feature of the Eagle was a strong guide rope, intended to keep the balloon at a uniform height. It also served as a keel to the air ship, which was provided with three sails. The balloon had a capacity of 170,000 cubic feet and was 67 1/4 feet in diameter. Its basket, or car was only seven feet in diameter and five feet in depth. Above this was the observatory. In the observatory were the sextants, glasses and other instruments. A stove was suspended twenty-five feet below the car, and was for cooking only.