sxow. 



639 



the district. Twenty inches is a very low estimate. Some places have an 

 annual rainfall of forty or fifty inches. In Cumberland we find 165 inches 

 has been recorded ! If we then multiply these last figures we get the enormous 

 quantity of 16,500 tons of water upon every acre of land in the district in 

 one year. It is reported from India that in the Khasia Hills the average is 

 610 inches, which must be the maximum rainfall in the world. At other 

 places, in the north-west provinces, the fall is only seven inches. Sometimes 

 in tropical rains we find fifteen inches of rain in a day, and that has been 

 exceeded. 



\Ye can now judge of the enormous amount of moisture carried up by 

 the sun and dispersed over the earth in rain, which swells our brooks and 

 rivers, cleanses the air of its impurities, supplies our springs, carries with it 

 into the sea lime from the rocks for the shells of marine animals, and then 

 leaving its salts, is again evaporated to form clouds, which discharge the fresh 

 water continually upon the earth in a never-ceasing rotation. 



Fig. 721. Crystals of snow. 

 SNOW. 



11 We all know what SNOW is," you will say, perhaps. Well, then, 

 will any ordinary young reader tell me what he knows about snow? 

 " It falls from the sky in white flakes," says one. " It's frozen rain," remarks 

 another. " Why, snow is snow," says a third. " There's nothing like it ; it's 

 white rain water frozen." 



The last answer we received is the nearest of all. Snow is not snow, 

 paradoxical as that sounds. Snow is Ice ! Flakes of snow are ice-crystals 

 white, because reflecting light. In the section of MINERALOGY we mentioned 

 crystals, which are certain definite shapes assumed by all substances, and we 

 gave many examples of them. Just as alum crystallizes and rock crystal 

 assumes varied and beautiful forms, so ice crystallizes into six-rayed stars 



It is to Professor Tyndall that the world is chiefly indebted for the 

 descriptions of snow crystals and ice flowers. In his work upon " Heat as a 

 Mode of Motion," this charming writer shows us the structure of ice flowers. 

 He describes a snow shower as a " shower of frozen flowers." " When snow 



