1 2 A GRICUL TURE. [CH. 



17. These two portions of the soil are strikingly 

 distinct, and they are therefore used as the foundation 

 of a system upon which we can base a general classi- 

 fication of soils. The manner in which the quantity 

 of clay and sand in a soil is determined is exceedingly 

 simple. When a sample of soil is to be so examined, 

 measures are taken to separate the stones and portions 

 of rock which are present. These are not a part of the 

 true soil; they are simply rock or stone mixed with the 

 soil. The soil upon which the farmer has to rely for 

 his crops is the fine earthy matter, and not the stones 

 which are mixed with it. It would, however, be a 

 serious error to consider these stones and pieces of rock 

 as useless to the farmer. These have their duties to 

 perform, as we shall hereafter see; but, for the present 

 purpose, they must be distinguished from the soil which 

 has to be examined. 



1 8. To obtain the fine earthy matter from a soil, a 

 small sieve or piece of wire work should be used, and 

 the coarser portions separated, and the finer carefully 

 dried. Two hundred grains- of the sifted soil may 

 then be thoroughly mixed with about half a pint of 

 water, and well shaken for some few minutes. As 

 soon as this has been accomplished, the vessel may be 

 allowed to remain quiet for a short time, during which 

 the sand falls to the bottom. Whilst the fine particles 

 of clay are still floating in the water, it should be 

 quickly poured into another vessel, leaving the sand 

 behind in the first. If the clay be not entirely re- 

 moved in the first attempt, the sand may be again 

 washed, and any clay poured into the vessel containing 

 that first removed. You have thus made a separation 

 of the soil, which will enable you to determine its 

 character, and to classify it accordingly. More ad- 

 vanced and accurate processes are sometimes adopted 

 (see Professor Church's " Laboratory Guide "), but 

 this simple process gives results which are sufficiently 

 satisfactory for all ordinary purposes. 



