L 5 8 7 ] 
tlie inclination of the drata from thence to the coun- 
tries on each fide, is perfectly uniform ; for they have 
frequently very conliderable inequalities, and thefe 
inequalities are fometimes fo great, that the drata are 
bent for fome fmall diflance, even the contrary way 
from the general inclination of them. This often 
makes it difficult to trace the appearance I have been 
relating, which, without a general knowlege of the 
fofhl bodies of a large trad of country, it is hardly 
poffible to do. 
48. At conliderable diftances from large ridges of 
mountains, the fcrata, for the mod part, alfuine a 
fltuation nearly level ; and as the mountainous coun- 
tries are generally formed out of the lower drata, fo 
the more level countries are generally formed out of 
the upper drata of the earth. 
49. Hence it comes to pafs, that, in countries of 
this kind, the lame drata are found to extend them- 
felves a great way, as well in breadth as in length : 
we have an indance of this in the chalky and flinty 
countries of England and France, which (excepting 
the interruption of the Channel, and the clays, hands’, 
&c. of a few counties) compofe a trad: of about three 
hundred miles each way. 
yo. Beddes the railing of the drata in a ridge, 
there is another very remarkable appearance in the 
drudure of the earth, though a very common one; 
and this is what is ufually called bv miners, the 
trapping down of the drata; that is/ the whole fet 
of drata on one fide a cleft are funk down below the 
level of the correfponding drata on the other fide. 
If, in fome cafes, this difference in the level of the 
drata, on the different ddes of the cleft, Ihould be 
Vol. LI, 4G very 
