200 IVriNERALOGY OF THE PENTLAND HiLLS. 



Section III. 



ALLUVIAL ROCKS. 



The alluvial substances are few in number, of 

 little extent, and do not present great variety in 

 appearance : they are, Rolled Masses, Gravel, Clay, 

 and Peat. 



I. Rolled Masses. 



These are generally portions of the neighbour- 

 ing rocks, which have been broken off by the in- 

 fluence of the weather, and rolled in the water 

 of the rivers and rivulets of the district. Amongst 

 these, however, I observed several large masses 

 of what may be named primitive grey-wacke^ and 

 which is foreignto this part of the country; its near- 

 est native place being near Dunkeld in Perthshire, 

 Similar masses occur in different parts of Mid- 

 Lothian ; also in Fifeshire. How have they been 

 transported to their present situation ? 



II. Gravel, Sand, and Clay, 



The gravel, sand, and clay, are portions of the 

 ^of the district, more or less completely bro- 



