picture of the Colorado river? At certain places it runs for long 

 distances at the bottom of an enormously deep channel in the solid 

 rock, the sides being at some points more than a mile high. How was 

 this gigantic furrow ploughed? Simply by the water itself, with the 

 assistance of the stones and sand it carried along. 



Yet this is still only a very small account of the industry of water. 

 It carries mud and small stones down stream with it for hundreds of 

 miles, but what is more surprising still, it was water that actually 

 made the mud and pebbles. To explain this we must refer for a 

 moment to the way in which water turns to ice and ice to water. If 

 you have not yet tried the experiment of freezing water in a bottle 

 on a cold night you should do so and you will learn that when water 

 freezes it expands in volume and occupies a larger space. This 

 explains why ice floats on water, for in becoming ice it increases in 

 volume and becomes therefore less dense, and so can float on the 

 heavier water. You will no doubt know cases in which the expansion 

 of freezing water does much damage. Water pipes and Jugs that are 

 full of water must burst when the water in them freezes. We say it 

 is due to frost, but this merely means that it is due to the freezing 

 water. 



ISTow all of the rain that falls does not run off in streams. Much of 

 it sinks into the soil and even into such rocks as sandstone and lime- 

 stone. Sandstone is a very coarse kind of stone and contains quite 

 large spaces or pores between the separate grains of sand which make 

 up the stone, and limestone is full of cracks, into which the water 

 trickles. Suppose, now, cold weather comes and part of the water 

 freezes. In freezing it must expand, and in expanding it shoves the 

 parts of the rock apart and so produces cracks which grow larger every 

 time the water freezes in them. If you notice the rocks exposed in a 

 quarry you will find that they are split up by great fissures, and these 

 large cracks enable the quarryman to divide the rocks up into large 

 blocks. At an exposed surface of the rocks layers are actually peeled 

 off by this action of freezing water, and fall from the rest. But 

 the water is not content to leave even the pieces that thus fall off. 

 In the same way it splits up these pieces into still smaller pieces until 

 it at last reduces them to fine grains of sand or mud, just as if they 

 had been crushed in a mortar. Thus rocks are turned into soil by 

 the action of water. Frost, then, is one of the farmer's greatest 

 friends. It helps to make the soil for him and also loosens the 

 ground so that the roots and fibres of plants can readily enter. Observe 

 the surface of a cultivated field after a frost. You will find that it is 

 now a layer of fine mud and in some cases you will see that the small 

 stones have been partly pushed out of their beds. 



