640 



SCIENTIFIC RECREATIONS. 



is produced in calm air," he says, " the icy particles build themselves into 

 stellar shapes, each star possessing six rays." We annex some drawings of 

 snow crystals, which are, indeed, wonderfully made. Hear Professor Tyndall 

 once again : 



" Let us imagine the eye gifted with a microscopic power sufficient to 

 enable us to see the molecules which compose those starry crystals : to 



Fig. 722. Ice crystal. 



observe the solid nucleus formed and floating in the air ; to see it drawing 

 towards it its allied atoms, and these arranging themselves as if they moved 

 to music, and ended by rendering that music concrete." This " six-rayed 

 star " is typical of lake ice also. 



Snow sometimes reaches us in a partly melted condition ; under these 

 circumstances it is called sleet, and snow being much lighter than rain (ice 

 is lighter than water), it descends less directly, and represents about one- 



Fig. 723. Ice crystal. 



tenth the depth of the rain-fall. The use of snow in warming the earth is 

 universally acknowledged, and as it is such a bad conductor, a man in a snow 

 hut will soon become unpleasantly warm. 



Ice is only water in another form, and snow is ice ; and it is the air 

 in the snow that gives it warming properties. These are all simple facts, 

 which any one by observation and careful reading and study may soon 



