THE SOIL 



111 



certain quantity of the carbonate of lime. There is thus 

 a steady, though small, drain on the carbonate of lime 

 present. This requires but little thought when an 

 appreciable amount is present in the soil, but some soils 

 contain so little that the addition of dressings of carbon- 

 ate of lime, in the form of chalk or limestone, at long 

 intervals, may be expected to add to their fertility. 



PRACTICAL WORK 



Dig a hole or trench in the garden, and note the 

 character of the soil from the surface downwards (see 

 Fig. 15). This trench 



de- 



may perhaps be 

 signed to fulfil some 

 useful purpose, or the 

 observations may be 

 made when occasion 

 arises for digging thus 

 deeply. Sketch what 

 you see. 



Ascertain, if possible, 

 the character of the rock 

 lying beneath the garden 

 either by digging down to it or by observing it at 

 some place in the immediate neighbourhood where it 

 comes to the surface, or is exposed, as in a road- 

 cutting. 



Collect the different kinds of stones to be found in 

 the garden soil, and note whether they are of a similar 

 character to the underlying rock. If other kinds of 

 stones are found, endeavour to explain whence they are 



IG. 15. Diagrammatic section illustrat- 

 ing gradual passage from the soil to 

 the subsoil, and, finally, the underlying 

 rock. 



