KINDS OF SOILS. 51 



is to take the two materials from the rocks of every 

 kind, the sand, and the fine dust or silt which we 

 will now call clay. The sandstones represent sand 

 turned to stone, the shales represent clay turned to 

 stone. These two in turn also become sand and 

 clay, and these two form the larger part of all our 

 soils. 



XI. EXPERIMENTS WITH SAND AND CLAY. 

 Procure from a sand-bank, or, if you are in town, 

 from the nearest stonemason's yard or from the dealer 

 in building-materials a quart of clear sand. Spread 

 it out in the sun to dry ; and when perfectly dry, place 

 a small quantity on an iron spoon, and hold it over a 

 hot fire. The heat has no effect upon it ; and even if 

 thrown in the fire, it remains unaltered except perhaps 

 in color. Remove the spoonful of sand from the fire, 

 and it will be found that the sand keeps its heat for 

 a long time. Place a small quantity of the sand in a 

 fine sieve, and pour water over it. The water at first 

 flows away more or less discolored, and presently runs 

 quickly through the sand pure and clean. While wet, 

 the sand sticks together slightly. Place it in the air, 

 and it soon dries, and the grains are as loose as before. 

 Place a little of this washed sand from the sieve in a 

 bottle filled with water. Cork the bottle, and shake 

 it up. The sand will be moved about as long as the 

 water is in motion ; but the instant the bottle is at 

 rest, it falls to the bottom, and forms a layer under the 

 clear water. Place some of the sand in the sun or in 

 an oven till perfectly dry. Place three tablespoonfuls 



