84 THE WONDERS OF GEOLOGY. Leot. I. 



the Thames, large masses of a firm conglomerate are occa- 

 sionally dredged up, in which Roman coins, and fragments 

 of pottery, are imbedded ; the stone being formed of sand 

 and clay solidified by ferruginous infiltration. 



These specimens of oxide of iron were dug up in a 

 marshy soil, near Bolney, in Sussex, and are of the same 

 nature as the substance called bog-iron ore, which so fre- 

 quently occurs in peat. Specimens of bog-iron are not 

 uncommon in the superficial loam and gravel of the south- 

 east of England. The ebony colour of the woods from 

 Ireland, which we have already examined, has been de- 

 rived from an impregnation of iron. 



The consolidation of sand, gravel, and other detritus, by 

 this agency, is taking place everywhere ; on the shores 

 of the Mediterranean ; on the coasts of the West India 

 Islands, and of the Isle of Ascension ; and on the borders of 

 the United States ; thus the remains of man, at Guadaloupe 

 — of turtles, in the Isle of Ascension — of recent shells, and 

 bones of ruminants, at Nice — of ancient pottery in Greece 

 — and of animal and vegetable substances, in our own 

 country, have become imbedded and preserved. 



I now proceed to notice a few instances of these simple 

 but important operations, by which much of the solid 

 crust of the globe is continually being renewed. 



42. Recent limestone of the Bermudas. — The 

 shores of the Bermuda Islands afford interesting examples 

 of this class of deposits in different states of consolidation. 

 The sea surrounding the Bermudas abounds in corals and 

 shells ; and from the action of the waves on the reefs, and 

 on the dead shells, the water becomes loaded w r ith calcareous 

 matter. Much of the detritus is transported to a distance, 

 and subsides in the profound depths of the ocean, imbed- 

 ding the remains of animals and vegetables ; but a great 

 portion is borne by the waves towards the shores, and cast 

 up on the strand in the state of fine earth and sand. This 



