72 



NATURE FOR ITS OWN SAKE 



usual elevation is not so great. Apparently it 

 stands still in thin wisps and curls against the 

 blue, but in reality it is a rapid traveller with 

 the wind, and sometimes reaches so great a ve- 

 locity as ninety miles an hour. It is not a large 

 cloud and in form is curled like hair, is fibrous, 

 or perhaps feathery. At times it is streaked 

 across the sky in a light film somewhat like the 

 Milky Way, but more frequently it is in small, 

 thin patches. It has also many patterns that 

 resemble stripes, tails, plumes, and wings, but 

 they are all diaphanous and film-like. When 

 it appears in streaks and lines these are usually 

 parallel to the wind, and are commonly spoken 

 of as " mares'-tails," ' ' goats'-hair," or " cats'- 

 tails." These clouds often move in irregular, 

 straggling groups. There may be only a few 

 straw-like wisps, and then again the upper space 

 may be spattered with them. Too thin and 

 nebulous as a general thing to show shadows, 

 they are the brightest of all the receivers and 

 reflectors of light. This may be for two rea- 

 sons. First, they are higher than any other 

 clouds and receive a more powerful light from 

 the sun because of the clearness and thinness of 

 the air in which they drift ; secondly, they are 

 ice-clouds, that is, made up of needles of ice, 



