94 7& Principles of Part IL 



ffond a year 6r two, that it may confoli- 

 date again, and the ferment be retrained ; 

 clfe it is not able to fupport the corn. 

 The reafon of this expaniion of the earth, 

 will appear from the expanfive force of 

 fhell-marl. Thefe different mells are a 

 compofition of calcarious particles, fit to 

 be converted, by the fire, into quick-lime, 

 and of an animal oil. 



WE muft here confider a body, called 

 foell-marl, which is commonly, though im- 

 properly, clafled with the marls. It muft 

 be ranked amongft the mells, as it is a pu- 

 trefied animal mell. It is a white light 

 fubflance, with an odorous fmell, appear- 

 ing to the eye to confift of a number of 

 fmall mells, and generally found at the 

 depth of a foot or two in thofe hollow 

 grounds which have been formerly over- 

 flowed. An animal inhabiting fuch a mell 

 I have met with in ponds, though it is 

 very rare. It muft have been once a very 

 common creature in this country, and ap- 

 pears 



