136 



THE planter's GUIDE. 



exposure to the atmospliere as of no benefit whatever to 

 soils ; he therefore condemns fallowing as useless and 

 unprofitable. But the reasons given for such an opinion 

 are merely speculative, and founded on nothing experr 

 mental or conclusive ; accordingly, they will convince no 

 skilful agriculturist, nor no practical planter. 



To these facts and observations we may add a sugges- 

 tion of Darwin's respecting temperature, which, though 

 fanciful, is ingenious — namely, that a certain portion of 

 atmospheric air being always taken down into the soil, at 

 the time of pulverisation, its internal heat is thereby pro- 

 moted, and its fertility increased. The confinement of the 

 air occasions decomposition, by means of the moisture in 

 the earthy portions. Ammonia is formed by the union 

 of the hydrogen of the water with the nitrogen of the 

 atmosphere, and nitre by the union of oxygen and nit- 

 rogen. The oxygen likewise probably unites with the 

 carbon contained in the soil, and forms carbonic acid gas 

 and carburetted hydrogen. Hence the heat given out 

 during these processes.'" 



Such is a short and very imperfect view of the manifold 

 beneficial changes which deepening and pulverising effect 

 in soils, according to the ingenious researches of Davy, 

 Thomson, Griesenthwaite, and others, who have usefully 

 laboured to render chemical researches subservient to rural 

 purposes. Had Tull, who flourished about a century ago, 

 been acquainted with chemistry as at present improved, 

 he would not have missed that permanent fame to which 

 his ingenuity so well entitled him. Tull was unquestion- 

 ably the first practical advocate for the power of pulverisa- 

 tion ; but he was deceived by its astonishing and various 

 effects, without being able to perceive its limits. Hence 



Phytologia, Sect. XII. 1. 



