404 EFFECTS OF CLIMATE AND SOIL ON CONFORMATION. 



Retention of Water by Soil. — Of all soils, clay 

 has the greatest power of retaming water, and, conse- 

 quently, it is admirably suited for growing luxuriant grass. 

 Therefore, clay land in temperate climates is the natural 

 home of the heavy cart-horse. " Ordinary clay consists 

 of extremely fine particles held together by a small 

 proportion of a colloid [glue-like] body. Its constitution 

 thus resembles that of putty, in which the particles of 

 whiting are united by means of linseed oil " (Warington). 

 This colloid body " is coagulated by salts of lime, and the 

 action of lime on a clayfield is to cause fiocculation or 

 granulation of the particles by its action on the cementing 

 material" (McConnell). The addition of organic matter, 

 such as farm - yard manure and peat, greatly reduces 

 the water-retaining power of clay soil, and increases that 

 of sandy soil, which is extremely permeable. Herbage 

 which is favourable to the development of saddle and 

 light harness horses, is grown on comparatively porous 

 soil. 



Lime. — Lime is the oxide of calcium ; and is best 

 known in the burnt form, as " quick lime." The term, 

 " lime," when referring to the constituents of soil, is 

 popularly used to signify some form of limestone. 



A good supply of lime in the soil is essential for the 

 production of the herbage which is suitable to vigorous 

 and high-mettled saddle and light harness horses. Its 

 beneficial action is of two kinds — namely, that of helping 

 to build up the tissues in the best possible manner, and of 

 rendering the soil porous. Lime is derived from calcareous 

 rocks (limestone), which chiefly consists of carbonate of 

 lime, with which carbonate of magnesia is combined in 

 some cases. The principal forms of limestone are : 

 Mountain Limestone ; Chalk ; Magnesian Limestone, 

 which is composed of carbonate of lime and carbonate of 

 magnesia in varying proportions ; Oolite ; and Calcareous 

 Marl, which is a mixture of clay and carbonate of lime. 



