THE PROPERTIES OF SOILS 195 



grassland gradually come to be buried ; year by year they get 

 deeper as the fine earth is carried up from beneath them and 

 deposited above, until at last they reach the depth below which 

 the worms do not work. The reality of this burying action, and 

 even the rate at which it takes place, can often be detected on an 

 old pasture or a lawn by opening a trench; at a slight depth 

 may be seen a thin layer of chalk or cinders which represents an 

 application of lime or ashes to the surface of the grassland some 

 years previously. If the date of this application has been re- 

 corded it is easy to calculate the rate at which it has been sinking, 

 or rather, at which it has been buried by the action of the earth- 

 worms ; in this way Darwin was able to show that in one case 

 materials had sunk three inches in fifteen years, and in another, 

 seven inches in twenty-nine years. 



THE PROPERTIES OF SOILS. 



In order to arrive at a proper understanding of the nature 

 and behaviour of different kinds of soil in the field it is now 

 necessary to do a few simple experiments, experiments which 

 do not call for any elaborate apparatus, but which become 

 particularly instructive if they are made quantitative by the 

 use of a balance and some of the more common accessories 

 of a laboratory. In the first place, it will be necessary to 

 collect a few specimens of soil by making a hole so as to 

 lay bare a face of the soil, and then taking out with a trowel 

 vertical slices, nine inches deep for the soil, and from ten to 

 eighteen inches for the subsoil, until two or three pounds have been 

 collected. Samples are wanted from an alluvial meadow (soil 

 and subsoil), from heavy clay and light sandy arable land (soil 

 and subsoil), from peaty land (soil only). The soils should be 

 spread out on sheets of brown paper and left to dry naturally in a 

 room ; they should be turned from time to time and crumbled 

 between the fingers when they are just beginning to dry, there 

 is a certain stage in the drying of a clay soil when it can be easily 

 reduced to a powder, a process which is a matter of some difficulty 

 if the soil is once allowed to get thoroughly dry. The soils can 

 then be stored away in bottles or tins. There will now be wanted 



