96 TOWN GEOLOGY. [iv, 



hypothesis of a state of things quite unlike what we 

 see now. We were brought up to believe that in the 

 Carboniferous, or coal-bearing era, the atmosphere was 

 intensely moist and hot, and overcharged with carbonic 

 acid, which had been poured out from the interior of 

 the planet by volcanic eruptions, or by some other 

 convulsion. I forget most of it now : and really there 

 is no need to remember ; for it is all, I verily believe, 

 a dream an attempt to explain the unknown not 

 by the known, but by the still more unknown. You 

 may find such theories lingering still in sensational 

 school-books, if you like to be unscientific. If 

 you like^ on the other hand, to be scientific you 

 will listen to those who tell you that instead of 

 there having been one unique carboniferous epoch, 

 with a peculiar coal-making climate, all epochs are 

 carboniferous if they get the chance; that coal is 

 of every age, from that of the Scotch and English beds, 

 up to the present day. The great coal-beds along the 

 Rocky Mountains, for instance, are tertiary that is, 

 later than the chalk. Coal is forming now, I doubt not, 

 in many places on the earth, and would form in many 

 more, if man did not interfere with the processes of 

 wild nature, by draining the fens, and embanking the- 

 rivers. 



Let me by a few words prove this statement. They 

 will give you, beside, a fresh proof of Sir Charles LyelPs 

 great geological rule that the best way to explain what 

 we see in ancient rocks is to take for granted, as long 

 as we can do so fairly, that things were going on then 

 very much as they are going on now. 



When it was first seen that coal had been once 

 vegetable, the question arose How did all these huge 



