322 How LONG DOES LiME LAST IN THE SOIL? [SEPT., 



rock, which was then excavated, hauled to the surface, and 

 spread over the adjoining land by sledges. Sixty to a hundred 

 loads per acre were applied, and the process was repeated at 

 intervals of six or ten years, as the farmer could spare the 

 labour. The pits were generally filled with brushwood and 

 rubbish, and left to fall in ; most of the fields to-day show a 

 depression due to this cause, known locally as a "dell," and the 

 former excavation can generally also be detected by the 

 presence of some subsoil clay, still raw and unkindly to work, 

 round the edges of the hollow. 



But in Hertfordshire, as elsewhere, comparatively little liming 

 or chalking is nowadays to be seen. How is it that the practice 

 has so much fallen into disuse.'' In the main, we must put it 

 down to the increased cost of labour : the farmer is working with 

 fewer hands on the farm, and no longer does he find occupation 

 for them in the winter and other slack times by digging chalk 

 or carting limestone from a distance. Liming and chalking have 

 begun to pass into the category of practices like marling, claying, 

 and" sanding, — excellent operations, by which in the past certain 

 soils have been created for farming purposes, but which are 

 unjustifiable in these days of low returns for farm produce and 

 high cost of labour. Something also must be set down to the 

 introduction of artificial manures ; by putting on bones or 

 superphosphate of lime the farmer thought he was restoring 

 lime to the land and was therefore absolved from any obliga- 

 tion to supply it more directly. But at the outset a clear dis- 

 tinction must be drawn between free lime, as it exists in quick 

 lime or slaked lime, and the same lime combined with an acid, 

 as in bones, where it is combined with phosphoric acid, or in 

 gypsum, where it is combined with sulphuric acid. What is 

 necessary for the soil is not so much the chemical substance 

 lime, but a base — something capable of combining with the 

 acids produced naturally or artificially in the soil. In quick- 

 lime or in slaked lime we have this base, and nothing else. 

 Chalk and all natural limestones contain lime and carbonic acid, 

 which, however, is so weak an acid that it is easily turned out and 

 does not interfere with the basic properties of the lime, whereas 

 in bones or gypsum the lime is already completely saturated 

 with strong acids, and in superphosphate there is even an 



