THE CLOUDS 89 



as if it had some potent attraction for them which 

 they were unable to resist, although they may be seen 

 streaming away to leeward like snowy meteors. And 

 this phenomenon may be witnessed wherever there are 

 mountains, in a greater or less degree, according to 

 their attitude and geographical position. 



Next in point of interest as well as beauty comes 

 the curious cloud-form known to meteorologists as the 

 cirrus. These are of a totally different character to 

 the cumulus or heaped-up clouds, whose greatest 

 height above the earth is estimated at three miles, 

 and whose form, as we have seen, is continually 

 changing. The cirrus or " curl " clouds float far above 

 the cumulus in the region of intense cold and rarefied 

 air, and are composed of minute ice crystals or spiculae. 

 It is a curious and beautiful sight to see how steadily 

 they will maintain their position and shape in the 

 upper ether when the cumulus clouds are flying along 

 underneath them, borne upon the wings of the earth 

 wind, as we may, somewhat fancifully, perhaps, desig- 

 nate the lower currents of air ; not that the cirrus is 

 stationary by any means, but its vast height above 

 the earth makes its motions appear very slow, indeed 

 almost imperceptible, unless compared with some 

 stationary object, such as a mountain-peak or a tower. 

 Streaming over the blue sky in graceful feathery 

 wreaths, they betoken unwonted movement among 

 the upper air currents soon to have a disturbing effect 

 upon the earth wind, and hence are considered by 

 sailors as sure precursors of storms. In fact, there is a 

 sea-rhyme of undoubted antiquity which runs 



" Mackerel backs and mares' tails 

 Make lofty ships carry low sails." 



