The Phenomenon of Frost 429 



atmosphere should clear, a scene of wonderful beauty is 

 revealed by the morning's sun. Every object stands " clothed 

 in white samite, mystic, wonderful." The apparition will last 

 but an hour or two. It is one which in its highest perfection 

 is seldom seen, not more perhaps, than once or twice in a 

 lifetime, but on a smaller scale it is not uncommon. 



Frost Fern Patterns on the Window Pane. — From 

 the earliest childhood we have all gazed with delight at the 

 beautiful patterns produced by ice on the window-glass. 

 Palm-leaves, fern-fronds of wonderful delicacy and finish, all 

 most gracefully curved, end in points. Their explanation is 

 not very difficult, and however inexplicable, at first sight, the 

 arrangement may appear, a little close attention will clear 

 away the obscurity. 



The presence of moisture on a window pane always proves 

 that the air is colder on the side that is dry than on that 

 which is wet. Almost always it is the inner side that is wet 

 and the outer side that is dry. The frost-patterns which we 

 refer to are always on the inside and they result from the 

 freezing of the moisture which has been condensed. The 

 thicker parts of these ice encrustations are always on the 

 lowest part of the pane. The fine leaf-like patterns always 

 branch upwards. Their points, which are the thinnest parts, 

 are always at the very top and very usually the uppermost 

 part of the pane is altogether free. Not infrequently there 

 may be seen large well-margined spaces on the frozen part, 

 which are quite free from ice, and dry. 



To understand these conditions it is well to inspect the 

 pane over night. The distribution of the moisture may then 

 be seen to be in its main features exactly what the ice will 

 show in the morning, but of course without its % beauty of 

 arrangement. Over-night the moisture will be seen to be 

 draining downwards and to be most in quantity on the 

 lowest part. The same rounded spaces, shaped like bays or 

 inland seas, will be noticed. The explanation of these, as of 

 the whole pattern assumed by the ice, is to be found in the 



