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THE POPULAR SCIENCE MONTHLY. 



Fig. 3. Lilientiial's Fltixg Appaeatds. The landing. 



can not be made to ascend slowly. Once progressing on their 

 road with the tremendous speed adequate to their weight and 

 wing surface, the kite machines can not be stopped or propelled 

 at a lesser rate without at once descending from the level attained. 



The contrivances ap- 

 plied to counteract 

 these disadvantages 

 have not proved effi- 

 cient to overcome 

 them. Nevertheless, 

 the experiments and 

 constructions made 

 by Stringfellow, Moy, 

 Tatin, by Kress in Vienna, Lilienthal in Berlin, Koch in Munich, 

 Philipps, Langley, Edison in America, Maxim in England, and by 

 Hargrave in Australia, all represent so many stages of constant 

 I)rogress. Mr. O. Lilienthal has just succeeded in floating down 

 at a moderate rate from a height of two hundred metres ; his per- 

 sonal skill in the handling of the apparatus adds considerably to 

 the advantages derived from its judicious construction (Figs. 2, 3, 

 and 4). Some of the most remarkable experiments in the field of 

 aerodynamics are those devised and carried out by Prof. Langley. 

 The essence of Prof. Wellner's innovation is his invention of the 

 sail-wheel (Fig. 5). It consists of a horizontally placed axis with 

 spokes and arched aeroplanes attached to them in a cylindrical 

 form. While revolving round the axis the latter take a slightly 

 slanting position, which causes the forward edges of these sur- 

 faces to be inclined, and consequently to compress the air in the 

 way of a sail or a kite, calling into ])lay the vertical force. Three 

 ribs running across each lifting surface and made in the form of 

 a screw at the same time serve to 

 strengthen the aeroplanes and to add 

 to the horizontal force. 



These sail-wheels set in pairs can 

 be placed, according to the size of air- 

 ship aimed at, in one or more groups 

 of two wheels, revolving in opposite 

 directions, behind or beside each other. 

 The cigar-shaped car, furnished with a 

 motor and carrying the aeronauts, is 

 attached horizontally under the center 



of the wheels, so that the whole construction will resemble a 

 colossal bird, propelled, instead of by wings, by revolving wheels, 

 the lifting surfaces of which are consecutively and constantly de- 

 veloping vertical and horizontal power. The bird's movements 

 in flying and the speedy headway motion necessary to the kite- 



Fui. 4. Ltlienthal's Flying 

 Ai'PABATrs. In fliLrht. 



