THE ACTION OF THE AIR UPON SOILS. 179 



naturally stony. Stones are active agents in promoting 

 heat and retaining it : some lands would be greatly 

 benefited by stones. 



The most productive and profitable land is one pos- 

 sessing a subsoil of sandy clay of a tender texture, 

 with a surface soil of a breify or mellow texture. This 

 sort of land is peculiar in working ; if wet immediately 

 follows after it is ploughed, or it is dug before it 

 can dry, nothing can be done with it by way of sowing 

 seed for some time. Such land must be either cropped 

 at once, or it must lie until it has thoroughly dried, 

 and gets softened by a rain ; then no land can equal it 

 for working or for producing a good crop. Heavy 

 lands are benefited greatly by a dressing of coarse 

 sand, tan, and cinder ashes. This kind of land should 

 be carefully managed, watching for fine weather to 

 plough or dig it ; but light, sandy, and gravelly soils 

 may be dug or ploughed even during wet weather, and 

 are even benefited by it, as it induces a closer texture 

 — for the season at any rate. 



The Action of the Air upon Soils. 



The fertilising power of the air upon land may be 

 attributed to the influence of the nitrogen gases which 

 compose oxygen and carbon, forming carbonic acid 

 gas, the chief fertiliser of the land. This influence is 

 more readily exerted beneficially upon land exposed to 

 the air by turning it up frequently. Thus land that 

 has been heavily cropped and run out, as we say, will 

 recover itself so as to bear good crops merely by rest 

 and frequent ploughing and digging. The fact is, let 

 the land be ever so unkind in its nature, it can be 

 made fertile by judicious management ; and the deeper 

 it is dug or ploughed, the more fertile it will be. 13ut 

 it is necessary to dig or turn it up to the light and air 

 at every sowing ; and, as a rule, the longer it is 

 exposed to atmospheric influences before sowing, the 

 better, especially in the case of heavy lands. These 

 should be turned up several times before cropping ; 



