:2o4 CLAY, SAM), MARL. 



in which marly deposits arc formed independently of 

 the presence of water. 



The first of these is from the Mowing of calcareous 

 sand, which being deposited on the land, often at 

 considerable distances from its native place, becomes 

 consolidated by pressure and moisture, and at length 

 covered by vegetable soil or peat, or even by terrene 

 alluvia. In this way, inland marl is found in some of 

 the Western Islands, even on declivities. But a more 

 remarkable deposit of this nature occurs in several 

 parts of Perthshire ; and. in the Geological Transac- 

 tions, I have described a conspicuous instance in Glen 

 Tilt. These are formed by terrestrial shells ; and the 

 depths of the deposits are often very great. For the 

 details, which my plan excludes, I must refer to the 

 original paper, where the animals which conduce to 

 produce them are described. 



