THE CONQUEST OF TIME AND SPACE 



ary. Thus, contrary to opinions held until recently, 

 and contrary to the rules for land vehicles and ships, 

 the strain of resistance of an aeroplane will diminish 

 instead of increasing with the increase of speed. Pro- 

 fessor Langley proved this remarkable fact with a 

 most simple but ingenious device. It consisted of an 

 immense "whirling table," driven by an engine, so 

 arranged that the end of a revolving arm could be made 

 to travel at any speed up to seventy miles an hour. At 

 the end of this arm, surfaces disposed like wings were 

 placed, and whirled through the two hundred feet 

 circumference, until they were supported like kites by 

 the resistance of the air. 



A certain strain was, of course, necessary to support 

 one of these winglike structures when stationary in 

 the air, but, curiously enough, less strain was required 

 when it was advanced rapidly. Thus a brass plate of 

 proper shape weighing one pound was suspended from 

 a pull-out spring scale, the arm of which was drawn out 

 until it reached the one-pound mark. When the whirl- 

 ing table was rotated with increasing velocity the arm 

 indicated less and less strain, finally indicating only an 

 ounce when the speed of a flying bird was reached. 

 "The brass plate seemed to float on the air,'' says 

 Professor Langley, "and not only this, but taking 

 •into consideration both the strain and the velocity, it 

 was found that absolutely less power was spent to make 

 the plate move fast than slow, a result which seemed 

 very extraordinary, since in all methods of land and 

 water transport a high speed costs much more power 

 than a slow one for the same distance." 



[276] 



