27<S 



MANUAL OF AGEICULTUEE. 



yielding wp of iheir organic matter and phosphates ; the length 

 of such delay being proportioned to the size of the triturated 

 particles. Bone ashes, i.e., hones deprived of their organic sub- 

 stance, contain fewer impurities than the natural phosphates of 

 lime, and yield the most valuable superphosphates. " A variety 

 of substances/' says Anderson, " are sold under the name of 

 nitrophosphate, potato manure, cereal manure, &c., which are all 

 superphosphates, differing only in the proportion of their 

 ingredients, and in the addition of small quantities of alkaline 

 salts, sulphate of magnesia, and other substances, but they pre- 

 sent little difference from ordinary superphosphates in their 

 effects/' The following, according to the same authority, are 

 analyses of various superphosphates : — 



The cheapest source of potash is the mineral called kainit, 

 containing sulphate of potash, which has now begun to be ex- 

 tensively supplied to turnips, potatoes, mangolds, &c. Gypsum, 

 or sulphate of lime, is also applied occasionally to leguminous 

 crops. 



Another method for increasing the soil's fertility employed by 

 advanced farmers, is the feeding of sheep upon rich artificial 

 substances, whereby, whilst the primary object of fattening the 

 animals is speedily attained, the soil is benefited by receiving 

 their valuable excreta, becoming enriched with manurial bodies. 



Other bodies, besides, are supplied to the soil, in order to pro- 

 mote certain physical as well as chemical results. Thus, clay is 

 added to light sandy and peaty soils, that thereby they may 

 receive body or staple ; and, reversely, sand and peat are added 

 to clay soils, the former — in order to render them more friable, 

 the latter to increase their stock of organic matter. In some 

 districts the clay of strong soils is burnt, for the consequent 

 effect of its friableness being increased, and many of its insoluble 

 compounds being broken up. Lime, however, is the principal 

 of all the substances which are added for combined physical and 



