32 AGRICULTURE. 



former readily falls apart after being taken out of the boxes 

 and can be used again, and the latter when moulded and 

 worked keeps its shape as it dries. 



Make two sets of objects (such as balls, cubes, cups, vases or simple 

 figures of small animals), one set from wet sand and one set from clay. 

 Place them in the sun or near the stove and observe the effect of drying. 



We see that sand as it dries does not stick together, and clay 

 as it dries does stick together and also sticks to other objects. 

 We now understand how it is that wet clay is sticky ; it clings 

 to the plow and the harrow and to the feet of the horses and 

 is hard or heavy to work. Sandy soil is said to be light and 

 clay soil to be heavy, not because of their weight, but be- 

 cause the former is easily worked and the latter is harder to 

 work. If we watch closely the drying out of the two sets of 

 objects that we have moulded we shall observe further that the 

 sand dries out more quickly than the clay; the latter holds on 

 to the water longer. Clay soils are usually wet soils ; they are 

 more apt to have water in them than sandy soils. 



The third class of soils is usually dark in color, from light 

 brown to dense black, such as are found in the woods where 

 leaves and branches have decayed, and in low pastures and 

 swampy places. This soil is made up of the refuse of leaves, 

 branches and roots of plants. Sometimes we can see pieces of 

 half-decayed or rotten plants ; sometimes there are very slight 

 traces of the original form of the plants. This soil has, how- 

 ever, all come from former plants. We call such a soil a 

 vegetable soil, and this dark colored loose material formed from 

 the decay of vegetable matter is called humus. Notice how 

 it differs from both sand and clay. It is light in weight and 

 easily worked and it holds water readily. 



Place a handful of swamp muck or leaf mould (humus) on an iron fire- 

 shovel and carefully set it upon the burning coals. It dries out, then burns 

 away until only a small quantity of ash is left. Place some wet sand on 

 the shovel and heat, and then a little wet clay. What is the result ? 



