6 INTRODUCTION. 



way as such rocks are now accumulated — the pebble-beds 

 and sands near the shore, the clayey and marly beds further 

 away from land, and the limestones in the deeper water. 

 Gravel, sand and clay are likewise formed and distributed 

 by rivers and glaciers, and all kinds of sediment may be 

 deposited in lakes. 



It may be noticed on any sea-coast where there are cliffs, 

 how the ceaseless action of the land-springs and the breakers 

 is ever wearing away the land. Portions of the cliffs are 

 undermined, landslips occur, and the harder rocks that fall 

 down are pounded up by the waves into shingle and sand. 

 The finer matter is often carried to some distance from the 

 shore and laid down at the bottom of the ocean ; while at a 

 very great distance from land, the accumulations may be 

 chiefly organic. Thus in time great deposits are formed. 



Again, all rivers bear along with them much material held 

 in suspension or solution, which has been worn away from 

 their banks or carried into them by springs and rivulets, and 

 this they convey to the sea or lake, as the case may be ; the 

 heavier suspended materials naturally sinking first, and the 

 finer or lighter particles being carried to the greater distance. 



The general arrangement and characters of the Aqueous, or 

 Sedimentary Rocks will be seen from the accompanying Table : — 



Defi'stis. 



li'heit indurated 

 or cotnpacted. 



Altered or 

 Metatiiorphoscd. 



Gravel J 



Shingle and 

 Pebble-beds 



Sand 



Loam or 

 Brickearth.. 



Clay 



Marl 



Calcareous \ 

 Mud or Ooze/ 



Breccia or | 



Conglomerate, "j 



Conglomerate 

 & Puddingstone 



Grit J 



Sandstone . 



Mudstone . 

 Shale 



Marlstone . 



Limestone- 



Angular, sub-angular, 

 and rolled fragments 

 of quartz, quartzite, 

 sandstone, flint, lime- 

 stone, etc. 



Pebbles and sub-angu- 

 lar fragments of 

 similar hard rocks. 



Coarse grains of quartz, 

 etc., cemented by 

 siliceous, calcareous 

 or ferruginous matter. 



Fine grains of quartz, 

 etc., cemented by 

 similar material. 



Clay and much Sand. 



Clay (Hydrated silicate 

 of alumina) and sand. 



Clay witli carbonate of 

 lime : or Argillaceous 

 limestone. 



Carbonate of lime 

 (chiefly). 



Greywacke 



and 



Quartzite. 



Hornstone 



and Slate. 



Marble. 



