Sect. III. Agriculture and Vegetation. 5 1 



have been marled, become much drier. 

 It is owing, I imagine, to the water get- 

 ting off fo quickly, that marled grounds, 

 as is obferved, are lefs affected by froft, 

 than the fame foils which have not got 

 any marl. 



Exp. 21. It effervefces with all the dif- 

 ferent acids, and turns with them into a 

 neutral fait. During the effervefcence with 

 the oil of vitriol, a fulphureous fleam arofe, 

 which is a flrong prefumption of its con- 

 taining fome oily fubftance. The clay marl 

 feemed to diffolve fafter than the ftone marl, 

 and deflroyed about a third more of the 

 acids. This quality which marl has of at- 

 tracting and destroying acids, is one of its 

 diftinguiming properties, without which no 

 fubftance can be called marl. In this quality 

 it is likewife diitinguifhable from clay. 



As farmers are extremely inaccurate in 



their terms, they often give the name of 



E 2 marl 



