102 TOWN GEOLOGY. [iv. 



off and lying in every direction, turned into coal, and 

 flattened, as coal-fossils so often are, by the weight of 

 the rock above should we not have a right to say 

 These trees were snapped off where they grew by some 

 violent convulsion ; by a storm, or by a sudden inrush 

 of water owing to a sudden sinking of the land, or 

 by the very earthquake shock itself which sank the 

 land? 



But what evidence have we of such sinkings f 

 The plain fact that you have coal-seam above coal- 

 seam, each with its bed of under-clay ; and that there- 

 fore the land must have sunk ere the next bed of soil 

 could have been deposited, and the next forest have 

 grown on it. 



In one of the Rocky Mountain coal-fields there are 

 more than thirty seams of coal, each with its under- 

 clay below it. What can that mean but thirty or more 

 subsidences of the land, and the peat of thirty or 

 more forests or peat-mosses, one above the other ? 

 And now if any reader shall say, Subsidence ? What 

 is this quite new element which you have brought into 

 your argument ? You told us that you would reason 

 from the known to the unknown. What do we know 

 of subsidence ? You offered to explain the thing 

 which had gone on once by that which is going on 

 now. Where is subsidence going on now upon the 

 surface of our planet? And where, too, upheaval, 

 such as would bring us these buried forests up again 

 from under the sea-level, and make them, like our 

 British coal-field, dry land once more ? 



The answer is Subsidence and elevation of the 

 land are common now, probably just as common as 

 they were in any age of this planet's history. 



