WIND AND FLIGHT 147 



Kestrel hovering with motionless wings. The up- 

 currents over sun-heated plains seem to have force 

 up to an enormous height. In Egypt I once watched 

 through my telescope a flock of Storks, ascending 

 with wings held rigid till they looked mere specks. 

 I wondered how they steered clear of one another, 

 there were so many describing mazy, intersecting 

 circles. It was just noon, and the day was decidedly 

 hot. 



Of course there may be among mountains upward 

 currents that are in origin similar to those found 

 over level plains. The extraordinary heat of the 

 summer of 1911 has been well calculated to produce 

 such currents in unusual places. I have a letter 

 from Mr. R. C. Gilson that gives most striking 

 evidence of this. " Lying on my back the other 

 day," he writes (the letter is dated Sept. 16th, 1911, 

 " on the summit of the Murren Schildhorn, a flat- 

 topped eminence (about 10,000 feet) with pretty 

 steep sides — at all events two opposite sides are 

 steep, the mountain is ridge-shaped — I saw a piece 

 of paper carried up by the wind, and having no 

 tendency to descend, but the reverse. I then noticed 

 another much higher up, then others, an apparently 

 indefinite series (the mountain is frequented by 

 untidy tourists), of which the farthest that I could 

 see were mere silvery specks in the sunshine. How 

 high they were it is impossible to say, but I guess 

 not far off 1,000 feet above the hill. The weather 

 was anticy clonic, almost windless. Presumably the 

 elevating forces were convection currents from the 

 sun- warmed mountain-side. Where I lay I could 

 hardly detect a breeze, but there was always a very 



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