380 THE WONDERS OF GEOLOGY. Lect. IV. 



their course the remains of animals and plants that may 

 happen to lie in the bed of the river, and at length subside 

 and are engulfed in silt and sand ; in like manner the fossil 

 trees in this cliff are associated with river shells ( Uniones), 

 and bones of land reptiles. The fossil forest at Brook 

 Point is, in fact, a raft of pine trees, which floated down 

 the river that deposited the Wealden beds, and was sub- 

 merged in its delta, burying with it bones of terrestrial 

 animals, freshwater mussels, &c. 



The trees when lying in the sandstone are invariably 

 covered with their bark, now in the state of lignite, and 

 which varies from one to three or four inches in thickness, 

 according to the magnitude of the trunk. This carbonized 

 cortical investment is quickly removed on exposure to the 

 action of the waves ; but the ligneous structure, the woody 

 fibre, remains. The trees are calcareous, not siliceous like 

 those of Portland ; they are more or less traversed by 

 pyrites, and the delicate veins and filaments of this mineral 

 which permeate the woody fibre, impart a beautiful appear- 

 ance to polished specimens. The trunks are generally of 

 considerable magnitude, being from one to three feet in 

 diameter ; some are of such a size as to indicate a height 

 of forty or fifty feet when entire. In the conversion of 

 the bark into lignite, and in the smooth condition of the 

 trunks, the trees of this fossil forest present a remarkable 

 dissimilarity from those of the Isle of Portland, which we 

 shall presently examine ; for in the latter the carbonized 

 bark rarely, if ever, occurs, and the surface of the steins is 

 similar to that exhibited by the trunks of old decorticated 

 trees, that have been much weathered by alternate exposure 

 to air and moisture. At Brook Point, on the other hand, 

 the trees appear to have been engulfed when fresh and vi- 

 gorous, with their bark and vessels full of sap. The annular 

 lines of growth are often very distinct, and I have traced 

 from thirty to forty on some of the stems ; but these circles 



