220 Sir C. Lyell on Fossil Reptilian Remains 



irate and bad been turned into coal, were covered with layers 

 of mud (now turned to shale), and yet tbe coal itself has re- 

 mained unsoiled throughout these various changes. The 

 lecturer thinks this enigma may be solved, by attending to 

 what is now taking place in deltas. The dense growth of 

 reeds and herbage which encompasses the margins of forest- 

 covered swamps in the valley and delta of the Mississippi, is 

 such that the fluviatile waters in passing through them are 

 filtered and made to clear themselves entirely before they 

 reach the areas in which vegetable matter may accumulate 

 for centuries, forming coal if the climate be favourable. 

 There is no possibility of the least intermixture of earthy mat- 

 ter in such cases. Thus in the large submerged tract called 

 the " Sunk Country,'' near New Madrid, forming part of the 

 western side of the valley of the Mississippi, erect trees have 

 been standing ever since the year 1811-12, killed by the great 

 earthquake of that date ; lacustrine and swamp plants have 

 been growing there in the shallows, and several rivers have 

 annually inundated the whole space, and yet have been un- 

 able to carry in any sediment within the outer boundaries of 

 the morass. 



In the ancient coal of the South Joggins in Nova Scotia, 

 many of the underclays shew a network of Stigmaria roots, 

 of which some penetrate into or quite through older roots 

 which belonged to the trees of a preceding generation. 

 Where trunks are seen in an erect position buried in sand- 

 stone and shale, rooted Sigillarise or Calamites are often 

 observed at different heights in the enveloping strata, attest- 

 ing the growth of plants at several successive levels, while 

 the process of envelopment was going on. In other cases 

 there are proofs of the submergence of a forest under marine 

 or brackish water, the base of the trunks of the submerged 

 trees being covered with serpulse or a species of spirorbis. 

 Not unfrequently seams of coal are succeeded by beds of im- 

 pure bituminous limestone, composed chiefly of compressed 

 modiola; with scales and teeth of fish, these being evidently 

 deposits of brackish or salt water origin. 



The lecturer exhibited a joint of the stem of a fresh-water 

 reed (Arundinaria macrospenna) covered with barnacles, 



