OF NATURE. 5* 
That clay is the fediment of the fea is fuffi- 
ciently proved by obfervation, for which rea- 
fon it is generally found in great plenty along 
the coafts. 
The journals of feamen clearly evirice, that 
a very minute fand 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 refembling 
plants were once real animals or vegetables *, 1 
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 fubltance. 
Hence we may be certain that marble may be 
generated from petrifactions, 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. 
Freeftone is the produCt of fand, and the 
deeper the bed, where it is found, the more 
compadt it becomes ; and the more denfe the 
1 I have taken the liberty not to follow the original 
text in this place. The learned will fee the reafon at iirft 
light* 
E 2 fand. 
