Earth Study 



Ssr 



cold, straightway the cap falls off and it becomes visible. If it be a stratum 

 of cold air that meets the invisible wanderer, it becomes visible as a cloud, 

 or as mist, or as rain. If the cold object be an ice pitcher, then it appears as 

 drops on its surface, captured from the air and chained as "flo-ving tears'' 

 lipon its cold surface. And again, if it be the cooling surface of th>= earth at 

 night that captures the wanderer, it appears as dew. 



But the story of the water magic is only half told. The cold brings back 

 the invisible water vapor, forming it into visible drops; but if it is cold 

 enough to freeze, then we behold another miracle, for the drops are changed 

 to crystals. The cool window-pane at evening may be dimmed with mist 

 caught from the air of the room ; if we examine the mist with a lens we find 

 it composed of tiny drops of water. But if the night be very cold, we find 

 next morning upon the window-pane exquisite ferns, or stars, or trees, all 

 formed of the crystals grown from the mist which was there the night before. 

 Moreover, the drops of mist have been drawn together by crystal magic, 

 leaving portions of the glass dry and clear. 



If we examine the grass during a cool evening of October we find it 

 pearled with dew, wrung from the atmosphere by the permeating coolness 

 of the surface of the ground. If the following night be freezing cold, the 

 next morning we find the grass blades covered with the beautiful crystals of 

 hoar frost. 



If a raincloud encounters a stratum of air cold enough to freeze, then 

 what would have been rain or mist comes down to us as sleet, hail or snow- 

 flakes, and of all the forms of water crystals, that of snow in its perfection is 

 th^ most beautiful ; it is, indeed, the most beautiful of all crystals that we 

 know. Why should water freezing freely in the air so demonstrate geome- 

 try by forming, as it does, a star with six rays, each set to another, at an 

 angle of 60 degrees? And as if to prove geometry divine beyond cavil, 

 sometimes the rays are only three in number — a factor of six — and include 

 angles of twice 60 degrees. Moreover, the rays are decorated, making 

 thousands of intricate and beautiful forms; but if one ray of the six is 

 ornamented with additional crystals the 

 other five are decorated likewise. Those 

 snow crystals formed in the higher 

 clouds and, therefore, in cooler regions 

 may be more solid in form, the spaces in 

 the angles being built out to the tips of 

 the rays including air spaces set in sym- 

 metrical patterns: and some of the 

 crystals may be columnar in form, the 

 column being six-sided. While those 

 snow crystals formed in the lower cur- 

 rents of air, and therefore in warmer 

 regions, show their six rays marvellously 

 ornamented. The reason why the snow 

 crystals are so much more beautiful and 

 perfect than the crystals of hoar frost or 

 ice, is because they are formed from water 

 vapor, and grow freely in the regions of 

 the upper air. Mr. W. A. Bentley, who has spent many years photo- 

 graphing the snow crystals, has found more than 1300 distinct types. 



Composite snow crystal formed in 



high and medium clouds. 

 Photomicrograph by W. A. Bentley. 



