| WELLNER'S SAIL-WHEEL FLYING MACHINE. |
By Miss HELENE BONFORT.
ONE of the latest and most ingenious schemes for solving the problem of aërial navigation is that devised by Prof. G. Wellner, of Brunn, Moravia, who has sought to bring in the application of a new principle. He calls his apparatus the "sail-wheel flying machine" (Segelrad-Flugmaschine), and regards the mechanism of it as a kind of cross between those of the screw-propeller and of the kite, combining the advantages and avoiding the inconveniences of both. His system has won approval and confidence from eminent engineers and experts in aërial navigation to such an extent that the Vienna Association of Engineers and Architects is having experiments and observations made which will show very soon the degree of practicability and value possessed by his invention.
In his paper on the subject, Prof. Wellner describes his line of thought and the result of his researches, prefacing them with a summary of the experiments and investigations of his co-workers. 
Fig. 1.—Air-ship La France. The oblong form of balloons chosen by Giffard in Paris in 1852, by Dupuy de Lôme in Vincennes in 1872, by Tissandier in 1883, and by Renard and Krebs at Chalais in 1885 for their balloon "La France," conquered to a considerable degree the resistance of the air and thus increased the velocity (Fig. 1). They contained electro-dynamic motors with a galvanic column so admirably suited to the apparatus as to secure the greatest possible power with the least weight. Various improvements made obviated the danger of pitching. The "La France" almost completely fulfilled the condition that the balloon must return to its point of departure; in seven ascents a return was five times made to the starting point, showing that five times a complete control of direction had been gained. A speed of 6·5 metres per second (about fourteen miles per hour) was reached. Efforts have been made by the French military department to double this velocity, making it thirteen metres per second. This would be important, as in aërial navigation direction can be controlled only by velocity. But the weight of the motor required for such great power must constitute a serious embarrassment. Moreover, the pressure of air currents and the resistance of the wind endanger the balloon constructed of light material.
