The mechanical air ship had, by this time, as may be inferred, begun seriously to occupy the attention of both theoretical and practical aeronauts. One of the earliest machines deserving of special mention was designed by M. Giffard, and consisted of an elongated balloon, 104 feet in length and 39 feet in greatest diameter, furnished with a triangular rudder, and a steam engine operating a screw. The fire of the engine, which burned coke, was skilfully protected, and the fuel and water required were taken into calculation as so much ballast to be gradually expended.