420 Transactions of the Society. 



originated not Irom a variety of vegetation, Piicli as \ve should 

 expect to find Irom a submerged forest, but from one class of 

 vegetation. If we are to accept the submerged forest theory, there 

 are one or two difhcultios to be removed before it can be conclusive. 

 Professor James Dana * has been at some trouble to ascertain the 

 amount of vegetable matter necessary to form a foot thick of coal ; 

 he says, " It would take eight feet in depth of compact vegetable 

 debris to make one foot of bituminous coal, or twelve feet to make one 

 of anthracite." Assuming these calculations to be approximately 

 correct, we have to imagine a four-feet seam of coal formed by an 

 accumulation of forest vegetation to the thickness of 32 feet, and 

 48 feet for an anthracite seam of the same thickness. How is this 

 mass of vegetable debris to be obtained from a submerged forest ? 

 Mr. Carruthers tells us that the " trees grew in the coal itself." t 

 We have to imagine, then, a forest growing on the debris of its own 

 decay, for generations as some people tell us. Now, I would ask 

 any chemist whether such a thing be possible with forest growth 

 exposed to the air : the debris would, of course, be speedily turned 

 into humus by the oxygen of the air. It is not necessary for me 

 to prove that the Carboniferous atmosphere contained oxygen. I 

 do not contend that the coal- forming vegetation was allied to the 

 bog-mosses (Sphagnaceae), but I do say that it was of aquatic 

 habit, growing in a manner similar to modern bogs, though of 

 much larger extent. 



In conclusion, I beg to return my thanks to Professor Harker, 

 of the Koyal Agricultural College, Cirencester, for his kind 

 assistance in looking at my slides, and giving me the benefit of his 

 opinion upon them. 



• 'Manual of Geology,' Ist edition, 18G6, p. 360. 

 t Quart. Journ. Geol. Soc, xl. p. 60. 



