26 



Popular Science Monthly 



Yr^AtZ IrK "^^"'^^l^i^E;, These beautiful deposits assume two principal forms, the feathery 



Sd iesi.n ?hf "'• ^^" ^""TV '' ^^' ™°^^ ^°"^"^°" ^"d the more striking in appearance 

 ana design. The same pane of glass will exhibit entirely different designs on different nights 



exists at all times in the air, and not from 

 raindrops; though, on the other hand, rain 

 IS often the final product of snow that 

 melts before it reaches the ground. 



The true structure of a mass of ice may, 

 however, be made evident by an experiment 

 that Tyndall was fond of performing in his 

 public lectures. Through a slab of clear ice, 

 revealing no trace of structure, he passed 

 the beam of an electric lamp, the light 

 falling upon a screen. The image of the 

 slab was magnified by a lens. While the 



light of the lamp was transmitted freely, 

 its heat was partly absorbed by the ice, 

 and produced an interesting transforma- 

 tion. _ Numerous six-rayed stars and com- 

 binations of such stars appeared here and 

 there on the screen. These "ice-flowers," 

 as they are called, resulted from the melt- 

 ing of crystals locked up in the block of ice; 

 they were, in fact, hollow spaces, retaining 

 the form of the original crystals but filled 

 with water. 



The invisible moisture of the air produces 



