82 .ANAtflTSIS OF SOILS. 



infolublein water, and not acted upon by common acids; It is the 

 fubftance which conftitutes the principal part of rock chryftal ; 

 it compofes a confiderable.part of hard gravelly foils, of hard 

 -Tandy foils, and of hard ftony lands. 

 Alum'mc* Alumint, or pure clay, in its perfe6t ftate is white like filex ; 



it adheres ftrongly to the tongue, is incombuftible, infoluble in 

 water, but foluble in acids, and in fixed alkaline menftrua.- 

 It abounds moft in clayey foils and clayey loams ; but even in 

 the fmalleft particles of thefe foils it is ufually united to filex 

 and oxide of iron. 

 Lime. Lime is the fubftance well known in its pure ftate under the 



name of quicklime. It always exifts in foils in combination, 

 and that principally with fixed air or carbonic acid, when it is 

 called carbonate of lime ; a., fubftance which in the moil com- 

 pact form conftitutes marble, and in its loofer form chalk. 

 Lime, when combined with fulphuric acid (oil of vitriol), pro- 

 duces fulphate of lime (gypfum), and with phofphoric acid, 

 phofphate of lime. The carbonate of lime, mixed with other 

 Tub fiances, compofes chalky Toils and marles, and it is found 

 in Toft fandy foils. 

 Magnefia, Magnefia, when pure, appears as white, and in a lighter 



powder, than any of the other earths ; it is foluble in acid, 

 but not in alkaline menflrua;, jt. is rarely found in foils; when 

 it does exift, it is either in combination with carbonic acid, 

 or with filex and alumine. 

 Animal decom- Animal decompojlng matter exifts in very different ftates, ac- 

 pofing matter. CO rding as the fubftances from which it is produced are differ- 

 ent; it contains much carbonaceous fubftance, and may be 

 principally reiblved by heat into this fubftance> volatile alkali, 

 inflammable aeriform products, and carbonic acid ; it is prin- 

 cipally found in lands that have been lately manured. 

 Vegetable de- Vegetable decompofing matter is likewife very various in kind, 



compdfihg mat- it contains ufually more carbonaceous, fubftance than animal 

 matter, and differs from it in the refults of its decompofition 

 principally in not producing volatile alkali ; it forms a great 

 proportion of all peats; it abounds in rich mould, and is found 

 in larger or fmaller quantities in all lands. 

 Saline com- The faline compounds found in foils are very few, and in 



poinds. quantities fo fmall, that they are rarely to be difcovered. 



They are principally muriate of foda (common fait), fulphate 

 of magnefia (EpTom fait), and muriate and fulphate of potafti, 

 nitrate of lime, and the mild alkalies. 



The 



