Lakes have been more numerous, &'c. 13 
ftone of no determined fize or figure; and the want 
of coherency is apt to give the obferver an idea, that 
the whole eminence is conftruéted in the fame loofe ~ 
manner. But, if the fuperficial rubbifh be re- 
amoved, the appearance of a folid rock will over- 
turn the hafty conclufion. No kind of matter enters 
in any confiderable proportion, into the firata of 
the north of England, that is proof to the injuries 
of the atmofphere. ‘The argillaceous faxa are moft 
fufceptible of its influence; and even the lofty 
ridges of limeftone, that are found in various parts 
of this county, are, in fome places, fo far demo- 
lifhed by the hand of time, as tobe nearly buried 
in their ownruins. ‘The knowledge of this method 
of decompofing the hardetft fannie: in the world, 
enables us to explain in a very eafy manner the 
formation of the deep channels, along which the 
rivulets of a mountain are conwéyed from its 
_fummit to the neighbouring vallies. For thefe rills, 
which in dry weather are fo infignificant as to glide 
unfeen among the afperities of the hollows where 
they run, are liable to be converted by heavy rains 
into furious torrents that carry all before them. 
It is on thefe occafions, that the loofe fragments of 
their Rony bottoms are. fwept away, and driven to 
the lower ground, leaving a new furface of the 
rock expofed to the atmofphere, which in time is 
broken up by its action, and afterwards removed 
by the impetuofity of fucceeding floods. The 
frequent repetition of thefe deftructive operations 
’ has, 
