[ 12 5 ] 
The waters were thus conftantly railing ob- 
ftacles to their own progrefs, and were frequently 
therefore forced into new channels ; lo as, by de- 
grees, to be extended over a furface of at leaft 500 
yards in length. And, by being repeatedly re- 
turned into the fame channels, a Stratum, of con- 
ftderable thicknefs, has been formed. 
On examining this Stratum , fome parts are dis- 
covered to be extremely hard, and others fo foft, 
as ealily to be cut. The foft parts, however, on 
expofure to the air, become as hard as hint ; and 
on being ftruck, found like metal. The reafon, 
of this difference in the hardnefs of different parts, 
appears to be this : as the waters frequently 
changed their channels, and repeatedly like wife 
returned again to the fame channels, if, in the in- 
tervals, there were any parts confiderably raifed, 
and confequently longer before they were covered 
with frelh incruftations, thefe, from a longer ex- 
pofure to the air, would acquire a greater degree 
of hardnefs. 
Whole houfes, in the neighbourhood, are built 
of this ftone, which they find more durable, than 
any other they meet with ; and as it has the ex- 
cellent property of growing harder, from being 
expofed, and has likewife many little cavities and 
interfaces, good mortar fo infmuates itfelf into 
thefe, as to form a wall as firm as one continued 
ftone. 
This Stratum affords very curious and beauti- 
•/ 
fully varied petrifactions. Mol's exhibits great 
varieties ; for it is evident, that the mofs has con- 
tinued to vegetate, after the roots and lower parts 
had 
