112 THE STORY OP THE EARTH AND MAN. 



For instance, in the Bay of Fnady, whose rapid tideg 

 cut away the red rocks of its shores and deposit their 

 materials quickly, red mud and sand constitute the 

 modern deposit. On the other hand, when the red 

 sand and mud are long washed about, their red matter 

 may disappear ; and when the deposition is slow and 

 accompanied with the presence of organic matter, the 

 red colour is not only removed, but is replaced by the 

 dark tints due to carbon. Thus, in the Gulf of St. 

 Lawrence, where red rocks similar to those of the Bay 

 of Fundy are being more slowly wasted, and deposited 

 in the presence of sea-weeds and other vegetable sub- 

 stances, the resulting sands and clays are white and 

 grey or blackened in colour. An intermediate condi- 

 tion is sometimes observed, in which red beds are 

 stained with grey spots and lines, where sea-weeds 

 or land-plants have rested on them. I have speci- 

 mens of Devonian red shale with the forms of fern 

 leaves, the substance of which has entirely perished, 

 traced most delicately upon them in greenish marks. 



It follows from these facts that extensive and thick 

 deposits of red beds evidence sub-aerial decay of 

 rocks, followed by comparatively rapid deposition in 

 water, and that such red rocks will usually contain 

 few fossils; not only because of their rapid deposition, 

 but because the few organic fragments deposited with 

 them will probably have been destroyed by the 

 chemical action of the superabundant oxide of iron, 

 which, so to speak, "iron-moulds" them, just as 

 stains of iron eat holes out of linen. Now when Sir 



