252 IMPROVEMENT OF THE SOIL 



here, that most of our soils are nearly destitute of lime, al- 

 though reposing on limestone rocks. We have no soils which 

 are strictly calcareous, and hence this earth may be added 

 without the least fear of injury, but with the certainty of ulti- 

 mate and permanent benefit. The quantity need not be 

 large ; four or five per cent, and even less will essentially im- 

 prove the texture of the soil, and supply the necessary earthy 

 ingredients, and it is in these two respects that we are now 

 speaking of it. Hence it should be applied, for these objects, 

 in the form of marl, shell or ground limestone. Quick or 

 slacked lime applied to the soil soon becomes converted, in 

 part, into carbonate, and air-slacked lime is already partially 

 carbonated ; but the application of lime in this form is better 

 suited to it as a saline manure. The effect of lime, as an 

 earthy ingredient, is to render cold, stiff clay soils more fria- 

 ble and light ; of course dryer and more easily heated by the 

 rays of the sun. Upon sandy soils, the effect is just the re- 

 verse ; and, in addition, it enables such soils to retain the 

 manures placed upon them, and counteracts the electro-nega- 

 tive character which the silicic acid or silex imparts to them. 

 2. Sand ox gravel. When a soil is too clayey or peaty, its 

 texture may be improved by the addition of sand or gravel. 

 Their effect upon such soils is similar to that of lime. The 

 sand gives to the clay a better consistency, and renders the 

 peat more compact. It is easy to understand how this is ; 

 but it has been a question of some difficulty to determine 

 whether sand or coarse gravel is the better form in which to 

 apply siliceous matter. This question is one of easy solu- 

 tion, provided all the circumstances are understood. If the 

 soil is peaty, the fine gravel will produce a more immediate 

 effect, and loam is better than gravel ; but coarse gravel will 

 be more durable, because it not only supplies the earthy in- 

 believed, by others, to add greatly to the fertility. When applied as 

 a carbonate, no ill effects can be experienced. In its caustic state, it 

 may prove injurious by forming with the vegetable matter an insoluble 

 substance, which thus removes a part of the vegetable food. 



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