1 SOILS 



to their temperature. The former are therefore sometimes spoken 

 of as cold, and sandy soils as warm. As a certain amount of 

 warmth in the soil is necessary for plant life, this indicates the 

 importance of draining low-lying, cold, clayey land. 



Volcanic soils. These are formed by the lava which has 

 flowed over the surface of volcanoes, and subsequently become 

 subject to the action of the atmosphere. Soils of volcanic origin, 

 as those of certain islands, are usually very fertile. Such soils 

 may practically be said not to exist in Ceylon. 



Submarine or coral soils are found in certain islands which, 

 by volcanic or other agencies, have been lifted up above 

 the sea. 



Chemical composition of soils. All soils are composed of (1) 

 vrganic and (2) inorganic elements. The former comprise 

 oxygen, hydrogen, nitrogen and carbon, which disappear as 

 vapour or smoke w r hen an organised body, vegetable or animal, is 

 burnt in the air. The first three are gases, and the last is a sub- 

 stance, one form of which, charcoal, is familiar to every one. 

 Besides these, there are two other substances, namely, sulphur 

 and phosphorus which are sometimes called secondary organic 

 elements, because they are frequently, but not always, found in 

 organised bodies. The inorganic elements which are always to 

 be found in combination with other elements in lands suitable for 

 cultivation are potassium, sodium, magnesium, calcium, and iron. 

 With the exception of magnesium, calcium and iron, all these are 

 essential constituents of plant-food. 



Examination of soils. The following simple mechanical 

 tests are given as a ready means of ascertaining approximately the 

 condition of a given soil:- Weigh out J Ib. of earth after it has 

 been well dried, boil it for a short time in a pint of water, and 

 then pour all into a glass vessel. Into this insert a piece of blue 

 litmus paper ; if the paper turn to a red colour, it shows that acid 

 humus is present in the soil, and that lime is necessary to counter- 

 act the acidity. Then add more water, stir well, and pour off 

 -carefully the muddy water into a large vessel, care being taken 

 that none of the sand which settles to the bottom is lost ; stir up 

 the sand with fresh water, which is again poured off into the 

 larger vessel. This is to be done several times until the sand be- 

 comes clean and free from mud. The contents of the larger 

 vessel are to be allowed to remain for several hours until the fine 

 mud settles to the bottom, when the clear water is to be carefully 



