268 
parture of the water from it, would at certain times be liable to 
be covered by inundations ; and at others, when left dry, would be 
exposed to the heat of the sun. The plants peculiar to these two 
different states might also be expected to be produced. Hence 
equiseta, reeds, and other aquatic plants, would, at one time, fill this 
spot, which at another would be covered with a variety of filices, 
palms, opunti(E, and of other plants peculiar to the open and sun- 
burnt heath. 
Should the neighbouring mountains have contained iron, this, 
dissolved by the various salts with which the water would be im- 
pregnated, would be conveyed to spots where the water rested, and 
where the decomposing organic matters were deposited ; and would 
there be precipitated in the form of a brown oxide : this, uniting 
with the superior and finer part of the earthy deposit, would cover 
the decomposing vegetable matter with a stratum which, perhaps, 
after no great length of time, would become that substance which 
is known to mineralogists as bog-iron ore. But if, instead of the 
water passing off, it should have long remained, and formed a large 
and deep lake, then would other strata be successively added to 
that which has just been mentioned. Sometimes these strata would 
be furnished by the crumbled particles of the softer rocks, which 
formed the sides of these immense and newly formed reservoirs 
At other times, large masses of harder rocks would fall, undermined : 
and, broken into pieces by the fall, would be sized and rounded into 
boulders of various forms and magnitude ; or would be so far com- 
minuted, as to be rendered the materials of future breccia, the 
coarser sand-stones, &c. By the pressure of many of these suc- 
ceeding strata, the lower ones would suffer a closer approximation 
of their parts. The effects of this pressure are most observable in 
those strata which have since become schisti, and which contain the 
flattened remains of both vegetables and animals. The marks of 
pressure are not, however, observable in all the strata, these effects 
