38 ASYSTEMOF 



a 



"& 



gents, the acid and the alcali, and that the cal- 

 careous earth might, under certain circumftances, 

 be changed into a mineral alcali, as fome have 

 conjectured; the necefiity of the exiftence of the 

 calcareous earth is fufficientiy obvious. But all 

 thefe hypothefes I pafs over, fince they for a long 

 while have been, and will, perhaps, remain for 

 ever undecided ; it being of more coniequence to 

 take notice of the advantages which are to be de- 

 rived from it in human ceconomy, fince it is more 

 or lefs employed in moil trades. However, I do 

 not intend to enter into ail thofe particulars, but 

 only to mention how the calcareous earth, when 

 in its crude ftate, is commonly made ufe of. 



When in the form of a loofe earth, (Seel. 

 v. i.) it is ufed for white-warning; and is 

 mixed with clay in agriculture : for, according to 

 Dr, jJuHbell's rules of vegetation, its alcaline 

 quality ferves to unite fat fubftances with water * 

 befides that it is of a drying nature, and renders 

 the clay lefs coherent, or, as the farmers fay, 

 cc makes the plowing eafier." Hence this 

 loofe earth, in fome foreign countries, is called 

 marie ; for, when added to clay, it promotes the 

 production of marie. The humus conchacea^ or 

 fhell or fea-fand, is looked upon as pretty nearly 

 of the fame quality; but it is unfortunate that 

 clay for the rnoft part is fcarce in thofe places, 

 where the calcareous earth is found in plenty, 

 and that fometimes more is expected from this 

 iaft than it poflibly can perform. Loofe earth 

 may eafily be made into lime, if it is previoufly 

 flacked with water, and made up in moulds. 



The indurated calcareous earth or (tones, in 

 rnafles or lumps, are very ufeful in arable land, 

 |}ecaufe it moulders by degrees on the furface, 

 and attracting the water, retains it longer than 



mol^ 



