PP AKAl^StS OP SOILS. 



this cafe, as has been (hewn by Mr. Tennant, it is exceeding* 

 \y injurious to land *. The magnetian limeftorte may be 

 diftinguifhed from the common limeftone by its greater hard- 

 nels, and by the length of time that it requires for its folu- 

 tion in acids, and it may be analyfed by the procefs for carbo- 

 nate of lime and magnefia IX. 



When the analytical comparifon indicates an excefs of vege* 

 table matter, as the caufe of fterility, it may be deftroyed 

 by much pulverization and expofure to air, by paring and 

 burning, or the agency of lately made quicklime. And the 

 defect of animal and vegetable matter mult be fupplied by 

 animal or vegetable manure. 



XVII. Sterile Soils in different Climates and Situations muft 

 difftr in Compojition. 

 Different ell- The general indications of fertility and barrennefs, as found 

 "^mftaiiMs 21 b ? chemical experiments, muft neceflarily differ in different 

 require differentclimates, and under different circumftances. The power of 



feS folk f ° r f ° i,S t0 abforb moifture > a principle effential to their produdive- 

 nefs, ought to be much greater in warm and dry countries, 

 than in cold and moift ones; and the quantity of fine aluminous 

 earth they contain larger. Soils likewiie that are fituated 

 on declivities, ought to be more abforbent than thofe in the 

 fame climate on plains or in valleys f . The produdtivenefs of 

 foils muft likewife be influenced "by the nature of the fubfoil, 

 or the earthy or ftony ftrata on which they reft ; and this cir* 

 cumftance ought to be particularly attended to, in confidering 

 their chemical nature, and the fyitem of improvement. Thus 

 a fandy foil may fometimes owe its fertility to the power of 

 the fubfoil to retain water; and an abforbent clayey foil may 

 occafionally be prevented from being barren, in a moift climate^ 

 by the influence of a fubftratum of fand or gravel. ^ 



XVIII. Of the chemical Compofition of fertile Corn Soils in the 



Climate. 



Aftua] compofi- Thofe foils that are moft productive of corn, contain always 



tion ot fame certain proportions of aluminous and calcareous earth in a 

 fertile foils. ...... „ . . r L i 



finely divided ftate, and a certain quantity of vegetable or 



animal matter. 



• Phil. Tranfaftions for 1759, p. 305. This limeftone is found 

 • abundantly in Yorkfliire, D-Jibyihire, and Som rfetthire, 

 -| Kii wan. Tranf, Irim Academy, Vol. V. p. 175. 

 \ The 



