NATURAL KISTOilY. 212 



To confirm this reasoning, it is worthy of remark, 

 chat the different strata of stones in quarries are al- 

 most all horizontal or regularly inclined. Indeed the 

 strata of granite vitrifiable sand, clays, marbles, cal- 

 careous stones, chalk, and marlcs, are always parallel 

 or equally inclined ; and the disposition of strata, as 

 deep as mankind have penetrated is the same. 



Those heds of sand and gravel which are washed down 

 from the mountains, must, in some degree, be excepted 

 from the general rule. And as they are formed by 

 rivers and brooks which often change their channels, 

 it is not surprising that they are so frequent. The 

 strata formed by rivers are not very ancient ; they are 

 easily distinguished by their frequent interruptions, and 

 the inequality in thickness, which is constantly vary- 

 ing, but the ancient strata uniformly preserve the same 

 dimensions throughout. These modern strata may 

 likewise be distinguished by the form of the stones and 

 gravel they contain, which bear evident marks of having 

 been rounded by the motion of water. The same ob- 

 servation holds good with respect to those beds of turf, 

 and corrupted vegetables, which are found in marshy 

 grounds, immediately below the soil ; and which have 

 derived their origin from successive accumulations of 

 decayed trees, and other plants. The strata of slime 

 and mud being formed by stagnating waters, or the 

 inundations of rivers, are neither so perfectly horizon- 

 tal, nor so uniformly inclined as those produced bv the 

 regular motions of the sea. In strata formed by rivers, 

 we meet, with river and seldom with sea shells ; but in 

 the ancient strata there are no river shells ; the sea 

 shells are numerous, well preserved, and all placed in 

 the same manner. From whence could this beautiful 

 regularity proceed? Instead of regular strain, why do 



