OF NATURE* 51 



That clay is the feditnent of the Tea is fuffi- 

 ciently proved by obfervation, for which rca- 

 fon it is generally found in great plenty along 

 the coafts. 



The journals of feamen clearly evince, that 

 a very minute fartd covers the bottom of the 

 fea, nor can it be doubted, but that it is daily 

 cryftallifed out of the water. 



It is now acknowledged by all, that tefta- 

 ceous bodies and petrifactions refembhng 

 plants were once real animals or vegetables ; * 

 and it feems likely that fhells being of a cal- 

 careous nature have changed the adjacent clay, 

 fand, or mould into the fame kind of fubflance. 

 Hence we may be certain that marble may be 

 generated from petrifadions, and therefore it 

 is frequently feen full of them. 



Rag-ftone the moft common matter of our 

 rocks appears to be formed from a fandy kind 

 of clay,, but this happens more frequently, 

 where the earth is impregnated with iron. 



Freeftom is the produ6t of fand, and the 

 deeper the bed, where it is found, the more 

 compad it becomes \ and the more denfe the 



* I have taken the liberty not to follow the ori:n'-^a! 

 text in this place. The learned uill fet the reafon at firlt 



E 2 1-nd, 



