Giffard was succeeded in France, first by Dupuy de Lome; then by Gaston Tissandier, well-meaning projectors of steerable balloons, but too cautious to effect an important advance in the art. The first of these gentlemen, an eminent marine engineer, in 1872, completed a gas balloon for the French government, resembling the one designed by General Meusnier in 1784, and like that also driven by muscular power actuating a screw, and kept rigidly inflated by use of an internal balloon, or ballonet. The car was suspended from the bag by a close fitting cover instead of a net, in order to lessen the resistance, and it was kept in alignment by use of crossed suspension cords. A speed of but six miles an hour was attained by the industrious work of eight men operating an ample screw propeller. A decade later Tissandier, with a balloon of like design, but driven by the power of an electric motor and bichromate of potash battery, attained a speed of six to eight miles an hour.