THE COMPOSITION OF FERTILE AND BARREN SOILS. 53 



In marly soils we have a class of soils which resemble on the 

 one hand clay soils, and on the other hand calcareous soils. Ac- 

 cording to the proportion of lime and clay which they contain, 

 they are more or less stiff, and, on the whole, belong to the 

 better kinds of soils. Many marly soils produce naturally heavy 

 crops of pulse, peas, and clover, and, when properly pulverised, 

 also good root-crops. 



All marly soils contain more than 5 per cent., and not more 

 than 20 per cent., of lime. When there is much sand mixed with 

 the clay and lime in the soil, it is called a sandy marl ; on the 

 other hand, if a marly soil contains much clay, it is termed a 

 clay marl. Clay marls are often used with much benefit for im- 

 proving light sandy soils. 



ANALYSIS of a CALCAREOUS SOIL from the Farm of the Royal Agricultural 

 College, Cirencester. By Dr. VOELCKEB. 



Organic matter and water of combination 6*339 



Oxides of iron and alumina, with a trace of phosphoric acid 9*311 



Carbonate of lime 54*566 



Magnesia trace 



Sulphuric acid ditto 



Chlorine ditto 



Potash and soda 1*032 



Insoluble silicious matter 28*947 



100*195 



The preponderating constituent in calcareous soils is lime. 

 In chalky soils, as some of the calcareous soils resting on the 

 great oolite, the proportion of carbonate of lime rises often as 

 high as 70 to 80 per cent. Calcareous soils, in which lime pre- 

 ponderates so largely, are, generally speaking, not very produc- 

 tive ; but they are well adapted for the growth of leguminous 

 plants, especially sainfoin, which tribe of plants appears to delight 

 in calcareous soils. The physical characters, as well as the 

 chemical composition of soils belonging to this class, vary ex- 

 ceedingly, and also the agricultural capabilities and value of 

 different calcareous soils. 



Those calcareous soils which contain a considerable propor- 

 tion of clay are cold and difficult to work, whilst others contain- 

 ing more sand are lighter and more easily cultivated. 



Before proceeding further, I may be allowed to observe, that 

 of all systems of classifying soils, the one in which soils are 

 arranged in groups according to the preponderance of one of its 

 four chief component parts namely, lime, clay, sand, and organic 

 matters appears to me the most simple and practically useful. 

 Accordingly soils may be conveniently classified as follows : 



