NATURE AND ORIGIN OF THE SOIL. 



35 



these cracks and fill them up. Then winter comes on and the 

 water in the cracks freezes. What will happen then ? Just 

 what happens when the barrel of rain water freezes, or the 

 down pipes on the house freeze solid, or the bottles of canned 

 fruit in the cellar freeze. There will be a bursting. And even 

 though the quantity of water is small, it must expand, the 

 rocks must give to make room for it. The cracks are made 

 larger, a little of the surface is broken away, or a huge shoulder 

 of the rock is burst off. Gradually, 

 year by year, the rocks are thus 

 broken up by the frost, the atmos- 

 phere wears them away, and the rains 

 wash them down. The rocky cliffs 

 are slowly broken down, and the 

 ice, as it slowly moves down the 

 sides of the mountain, scrapes and 

 scratches off more and more. This 



Sad bearing -pvrti&i, 



Fie. IQ Soil formed from hill rock at a distance, a is solid rock of a hill or mountain. 

 Kock at c has l>een broken off by rain and frost and thrown down to foot of bill ; 

 coarsest rock lies in heaps forming soilless pirtio i ; finer rock has been carried further 

 down where some plants, as trees and grass, grow. Finest soil IS being washed into 

 the stream to be carr ed away aiid spread out, farming layers of soil more or less level, 

 on which crops are grown. 



material is washed away the larger pieces but a short dis- 

 tance, the smaller pieces further, and the finest sand and clay 

 carried far away, to be dropped or spread out somewhere to 

 make soil. Seeds are dropped by the birds or blown by the 

 winds ; some plants sprout, grow, die and decay, and form a 



