100 TOWN GEOLOGY. [iv. 



is set on fire, pits are burnt into the ground many feet 

 deep, or as far as the fire can go down without reach- 

 ing water, and scarcely any earthy residuum is left ; 

 just as when the soil of the English fens catches fire, 

 red-hot holes are eaten down through pure peat till the 

 water-bearing clay below is reached. But the purity 

 of the water in peaty lagoons is observable elsewhere 

 than in the delta of the Mississippi. What can be 

 more transparent than many a pool surrounded by 

 quaking bogs, fringed, as they are in Ireland, with a 

 ring of white water-lilies, which you dare not stoop to 

 pick, lest the peat, bending inward, slide you down 

 into that clear dark gulf some twenty feet in depth, 

 bottomed and walled with yielding ooze, from which 

 there is no escape ? Most transparent, likewise, is the 

 water of the West Indian swamps. Though it is of 

 the colour of coffee, or rather of dark beer, and so 

 impregnated with gases that it produces fever or 

 cholera when drunk, yet it is at least when it does 

 not mingle with the salt water so clear, that one 

 might see every marking on a boa-constrictor or 

 alligator, if he glided along the bottom under the 

 canoe. 



But now comes the question Even if all this be 

 true, how were the forests covered up in shale and 

 sandstone, one after another ? 



By gradual sinking of the land, one would suppose. 



If we find, as we may find in a hundred coal-pits, 

 trees rooted as they grew, with their trunks either 

 standing up through the coal, and through the sand- 

 stone above the coal; their bark often remaining as 

 coal while their inside is filled up with sandstone, has 

 not our common-sense a right to say The land on. 



