376 



which has been just described, from its possessing hardly any 

 vacuities. The texture of the wood is very evident, and even 

 the knots of the wood are frequently perceptible : but, as in the 

 Bovey-coal, so in this fossil, the woody fibres are distorted in 

 various directions, in such a manner as could not have taken 

 place, if they had not been in some degree softened. The calca- 

 reous spar, which permeates the wood through every part, marks 

 it in many places with streaks of a beautiful pearly white, 

 formed by the deposition of the spar from its infiltrated solution ; 

 and when this happens to have been the case in a cavity rather 

 larger than the others, such an arrangement of the particles of the 

 carbonate of lime will sometimes take place, as is -observed in cavi- 

 ties large enough to allow of the formation of stalactites, and the 

 cavity will be found to be filled with striated or fibrous carbonates, 

 or alabaster. Thus, under one or the other of these forms, will the 

 carbonate of lime be found to fill every cavity and rift in the wood 

 which had been produced by the mechanical action of the water 

 in which it had lain, or by subsequent shrinking of the wood. 



The calcareous fossil wood which is found in the neighbourhood 

 of Bath, and of which a specimen is depicted in Plate V ill. Fig. 4. 

 resembles very much in colour that of Charmouth ; but is harder, 

 and retains, still more perfectly, the form of the wood. In the par- 

 ticular specimen, described in the Plate, the spar so penetrates the 

 mass, as to accompany the fibres, in all their directions, in threads, 

 so minute as to be discovered, in many parts, only by tl^e aid of a 

 lens, of no small power. It is also pervaded through its whole 

 substance by a mass of spathose matter, about half an inch in width ; 

 and yet the fibres of the wood are nearly as evident, on the polished 

 surface, as if they had undergone no change. 



Whilst inquiring -into the nature and origin of silicious fossil 

 wood, I ventured to attribute its formation, to the impregnation of 

 wood, chiefly, in different stages of bituminization, with silK, ; <>i- 



