Xll. 



3. 



rt!ie 



ated 



'^Hed i 



m 





ceoi: 



1 



1 



s 



J 



^^ iron 



'■^quent 



as 



cdfo 



utepart 



' g more 

 er, and 

 ice of it 

 ■ ier im- 



odours 



kiiow' 



.m over 



DS 



feme 

 ;d with 

 careous 

 I aether, 



neliora- 

 > roots. 



a ni 



crreater 

 ■row on 



ir 



earl/ 



.jfjcr eX 



D 



ag' 



iaous 



SCET. XII. 4 



PULVERIZATION 



It fliould b 



dded, that fom 



are 



faid not to impoverifii 



D 



before th 



d on which they have grown during their herbaceous date 

 . k..i A.m. have arifen; as turnips, when drawn up am 



drawn up and 

 This has b 



Some 



earned away to feed cattle or (heep on other grounds ^ . . . . 



afcrlbed by L.e authors to the foil having been (haded by the. ta.k 

 foliage, and thus not having fufFered fo tnuch by e vapor- ■"_ 

 have afcribed this fuppofed melioration of the fo.l to its having bee 

 fcreeued or overftadowed by the th.cker foliage of fuch crops; an 

 that as the putrefaaive procefs of vegetable recrements proceeds beft 



p and confined air, as wood decays fooneft in cellars, they fup- 



d 



'pofb'thc foil n.ay thus become improved. But Mr.TuU feems 

 to doubt the faa, or to attribute it to the ground, where fuch^tots 

 are cultivated, being ufually once or twice hoed ; and thus in efFeft to- 

 have been followed by the repeated aeration and pulverization of th& 

 foil and the deftruaion of innumerable weeds. 



If neverthelefs the faft be true, not only all the circumftances above- 

 Hientioned may contribute to produce it, but alfo, as it appears by the 



experiments of Prieftley and Ingenhoufe, that though the perfpirable 



matter of vegetable leaves gives out oxygen in the funflime, yet that 



o-ives out carbonic acid in the fhade ; 



w 



hich even in its aerial 



aaffeous form is much heavier than common air. and will therefore 



fubfide on the earth in the (hade of this perfpiring fohag( 

 tribute to enrich the foil by the hourly addition of carbon 



d 



4. Neverthelefs wh 



th 



foil is 



dy replete with manures 



and thefe proceffes produftive of carbonic, nitrous, 



d phofph 



acids, and of volatile alkali 

 foils muft be injured by bei 

 fallowing ; 



proper abund 



fuch 



K 



fr 



quently turned over in fummer 



and' thus by expofing too great a furface, and that too fre- 



2 rain ; by which much of 



quently, to the air, the funlhine, and the rain ; 



the fluid carbonic acid will be converted into aerial carbonic acid, and 



efcape,as well as the phofphorus and the ingredients in their ftate p 



the produdion of nitrous acid, and of the volatile alkali 



6 



O 



th 



