SOME AERONAUTICAL EXPERIMENTS. 147 



a inechanicul succes.s if its ratio of horsopower to tonnage is insiu'niti- 

 cant. A tiyino- nuu-hine that would tiy at a speed of 60 miles an hour 

 with eno-ines of 1,000 horsepower would not he upheld by its wino-s at 

 all at a speed of. less than 26 miles an hour, and uothino- less than 500 

 horsepower eould driv(> it at this spetxl. But a l)oat which could make 

 •iO miles per hour with engines of 1,000 horsepower would still move 

 •4 miles an hour even if the engines were reduced to 1 horsepower. 

 The pro])lenis of land and water travel were so1v(m1 in th(>, nineteenth 

 century, hecause it was possible to begin with small achievements and 

 gradually work up to our present success. T\\o Hying problem was 

 teft over to the twentieth century, l)ecaus(> in this case the art nuist Ije 

 highly developed before any Hight of consideral)le duration can ])e 

 ol)taiiuKl. 



Howevei'. there is anotluu' way of flying which re(|uires no artificial 

 motor, and many workers Ixdieve that sucec^ss will first come by this 

 road. 1 refer to the soai'ing Hight, ])y which the machine is perma- 

 nently sustained in the air by th(^ same means that are em])loyed 1)y 

 soaring l)irds. They s})read their wings to the wind, and sail T)V the 

 hour, with no perceptible exertion ])eyond that reciuired to balance 

 and steer themselves. What sustains them is not dc^finitely known, 

 though it is almost certain that it is a rising current of air. But 

 whether it be a rising current or something else, it is as well al)le to 

 support a fl^nng machine as :i bird, if man once learns the art of util- 

 izing it. In gliding experiments it has long ])een known that the rate 

 of vertical descent is very nuich retarded and the duration of the 

 flight greatly prolonged if a strong wind blows u\) the face of the hill 

 parallel to its surface. Our machine, when gliding in still air, has a 

 rate of vertical descent of nearly 6 feet per second, while in a wind 

 blowing 26 miles per hour up a steep hill we made glides in whicli the 

 rate of descent was less than 2 feet per second. And during the 

 larger part of this time, while the machine remained exactly in the 

 rising current, there was no descent at all, l)ut even a slight rise. ]f 

 the operator had had sufficient skill to keep himself from passing 

 beyond the rising current, he would have been sustained indetinitely 

 at a higher point than that from which he started. The illustration 

 shows one of these very slow glides at a time when the machine was 

 practically at a standstill. The failure to advance more rapidly causinl 

 the photogi'apher some troutjle in aiming, as you will perceive. In 

 looking at this picture 3'ou will readily understand that the excite- 

 ment of gliding experiments does not entireh^ cease with the breaking 

 up of camp. In the photographic dark room at home we pass moments 

 of as thrilling interest as any in the field, when the image begins to 

 appear on the plate and it is yet an opon ([uestion whether we liave a 

 picture of a Hying machines or merely a ])atcli of open sky. These 

 slow glides in ri.>>ing currents probably hold out greater hope of exten- 

 sive practice than any other method within man's reach, but they have 



