1883.J S03IE OF THE CIIAnACTEPJSTICS OF SOILS. 107 



and the presence of lime or some other base with which to neutralise 

 the acid as it formed, and the process goes on untiriugly. In early- 

 summer it commences with us, and it continues far into autumn. The 

 nitrates are so soluble that unless they are speedily taken up by 

 growing plants they soon find their way to the drains, for ever to be lost 

 to the fields from whence they originated. Phosphorus is rather scanty 

 in soils, and though there is enough in the majority of them for the 

 uses of natural lierbage, the growth of cultivated plants necessitates 

 the bestowal of large quantities of phosphates on land under tillage. 

 Potash is not usually so scarce, for it enters largely into the composition 

 of most of the rocks that form the basis of soils, and as disintegration 

 and decomposition proceeds, fresh stores of it is being placed at the 

 disposal of plants. Experiments on the absorbent powers of soils have 

 revealed the strange fact, that when solutions of potash such as the 

 nitrate, sulphate or carbonate, are poured on soil and allowed to filter 

 through it, they have the property of arresting, as it were.tlie potash 

 of any of these salts and substituting lime or soda in its place. Where, 

 however, neither of these alkaline bases or any otliers are available to 

 act the part of the potash in neutralising the acid, the solutions pass 

 through unaltered, and the potash is found in the filtrate. Soils act 

 similarly with solutions of ammonia, having the power of arresting 

 this most soluble body and preventing its escape to the drains before 

 it has taken part in the neutrifying process before referred to. Hence 

 it follows that lime, besides acting directly as a supplier of food to 

 plants, performs many useful ofhces in the soil. It acts as abase with 

 which to neutralise the nitric acid produced by the minute fungus 

 already mentioned, thus saving the less plentiful potash and ammonia 

 for the uses of the plant ; and in like manner it neutralises the acids 

 of the soluble phosphates which are nowadays so much used by farmers, 

 and enables the latter to obtain the full good of them. Before the 

 plant has time to seize on the soluble phospliates freshly bestowed on 

 the soil, the free acids they contain have attached more lime and 

 once more become insoluble, but afterwards they are precipitated in 

 such a finely divided state, that the rootlets of the plant can easily 

 absorb them. "Were lime not available, the accumulation of free acids 

 in some soils would soon come to act prejudicially on the welfare 

 of the plants which the farmer thought to encourage. "Without its 

 presence and use, the quickened decomposition of soils full of such 

 inert organic matter as peat, is almost impossible. Other bases — 

 potash, ammonia, or soda — may perhaps be available, but the first 

 two are too valua'ble to be allowed to serve such purposes as the 

 cheaper and more plentiful lime can even more efficiently perform. 

 Comparing the composition or the analyses of the ordinary crops 

 of cultivation with that of wood, we can at once see why it 



