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NATURE FOB ITS OWN SAKE 



from sudden gusts of wind and cold. They 

 rush up the mountain-side quite rapidly, as 

 everyone knows who has stood there at noon- 

 time and felt the draft upward from the valley. 

 As soon as they reach the top of the mountain 

 they are forced from shelter by the currents 

 coming after, and meet with the cold winds 

 above the peak. The result is quick condensa- 

 tion and the formation of that cloud which is 

 called the " cloud cap " or "night cap" of the 

 mountain. It is broken and blown away by 

 the winds continually, but it is also being con- 

 tinually renewed by the ascending currents, so 

 that apparently it remains stationary and in- 

 tact. It does not sink down, because of its re- 

 newal and because the currents in measure lift 

 it up. 



Something of the same process is apparent in 

 the formation of what is called the "banner 

 cloud," which appears to fly out like a streamer 

 from some of the Alpine peaks. This cloud is 

 usually on the warm valley-side of the peak. 

 The moist air from below rises along this shel- 

 tered side to the tip of the peak before it is 

 struck by the cold currents and condensed into 

 visible vapors. Above it and at the sides the 

 cloud is being cut off and drifted away by 



