SNOW-FLAKES 23 



The star-like crystals are believed to form only in 

 great cold, as in the upper regions of the air. Tabular 

 crystals, or flat hexagonal plates, form at higher 

 temperatures. They are common in the lower layers 

 of fallen snow, and appear to the eye as minute 

 lustrous scales. The crystalline form must have 

 undergone change, for tabular crystals rarely fall 

 from the sky. 



A sufficiently low temperature will produce snow 

 direct from water-vapour. The story of the Peters- 



FIG. 9 Hexagonal snow -crystal, with star-shaped cavity. The alternate triangular 

 fields (a, />) differ in pattern. Photographed from nature by Nordenskiold. 

 Nature, Oct. 19. 1893. 



burg ball-room is well known. The hall was crowded 

 with people and ladies were fainting from heat, when 

 some one opened a window, and the cold air rushing 

 in caused snow to fall. Maupertuis observed in 

 Lapland that the mere opening of a door caused big 

 snow-flakes to fall in the hut. Cold readily forms 



