The Phosphates of America. 11 



potassium, sodium, magnesium, iron ; phosphates, sulphates and 

 chlorides. 



The soil at first resulting from this gradual decomposition 

 formed very thin layers, in which only the lower orders of plants 

 found sufficient food to fructify, deriving from the air and the rain 

 their carbon, hydrogen, oxygen and nitrogen. In the natural 

 process of death and decay, these fresh elements of fertility, in vari- 

 ous states of combination, were transferred by the plants to the soil, 

 which was thus enabled to afford nourishment to a higher vegetation. 



It is the general custom to class arable lands according to the 

 nature of their predominating constituents, and thus we allude to 

 soils as sandy, clayey and limey. 



Sandy soils are distinguished by their extreme porosity, and are 

 frequently in such a fine state of division that in the dry season 

 the least wind will displace and scatter them in all directions. In 

 such cases they are naturally sterile ; but when they are sufficiently 

 moist, they facilitate and encourage the growth of an immense 

 variety of plants of the lower order, which, by their eventual 

 decomposition or putrefaction, form considerable deposits of that 

 valuable substance called humus. 



Such soils are more propitious than any others for the develop- 

 ment of plants with very delicate or fine roots, such as barley, rye, 

 oats, lucern, lupins, lentils and potatoes ; but they require constant 

 attention, and a large and regular quantity of manure, because 

 their porosity permits them to absorb such an abundance of oxygen 

 that all their organic matter is rapidly burnt up. 



Clayey soils are heavy and compact, and when they contain 

 more than fifty per cent, of pure clay are onerous to work, and 

 unprofitable to cultivate. It has, however, fortunately been dis- 

 covered that the addition to them of so small a quantity as two per 

 cent, of burnt lime suffices to so entirely change their nature and 

 consistency, by transforming the silicate of alumina into a porous 

 silicate and aluminate of lime, that it is now an easy matter in 

 districts where lime is cheap and plentiful to overcome this diffi- 

 culty. In hot countries or in windy regions or in districts where 

 the subsoil is of a very permeable character, good clay lands offer 

 great advantages, and although they periodically require the appli- 

 cation of large quantities of reconstituents, they possess the faculty 

 of retaining all the precious elements supplied to them, and of 

 storing them up for the use of successive crops. When they contain 

 a proportion of about ten per cent, of carbonate of lime, or chalk, 



