The many experiments made during this last quarter of the nineteenth century have given considerable impetus¹ to the question of guidable balloons. The cars furnished with propellers² attached in 1852 to the aerostats of the elongated³ form introduced by Henry Giffard, the machines of Dupuy de Lome in 1872, of the Tissandier brothers in 1883, and of Captain Krebs and Renard in 1884, yielded many important results. But if these machines, moving in a medium heavier than themselves, maneuvering⁴ under the propulsion of a screw, working at an angle to the direction of the wind, and even against the wind, to return to their point of departure, had been really "guidable," they had only succeeded under very favorable conditions. In large, covered halls their success was perfect. In a calm atmosphere they did very well. In a light wind of five or six yards a second they still moved. But nothing practical had been obtained. Against a miller's wind—nine yards a second—the machines had remained almost stationary⁵. Against a fresh breeze—eleven yards a second—they would have advanced backwards⁶. In a storm—twenty-seven to thirty-three yards a second—they would have been blown about like a feather. In a hurricane—sixty yards a second—they would have run the risk of being dashed to pieces. And in one of those cyclones⁸ which exceed a hundred yards a second not a fragment of them would have been left. It remained, then, even after the striking experiments of Captains Krebs and Renard, that though guidable aerostats had gained a little speed, they could not be kept going in a moderate breeze. Hence the impossibility of making practical use of this mode of aerial locomotion⁹.