329 



the term, which long usage sanctions, of PETRIFIED WOOD, LITHOXY- 

 LOX of oryctologists. This may be divided into different classes, 

 according to the predominance of the different earths with which it 

 is impregnated : thus petrified wood may be subdivided into sili- 

 cious wood, calcareous wood, aluminous wood, &c. 



The nature of these several fossil woods we shall now proceed 

 to examine, pointing out the different kinds into which each may 

 be again subdivided, and the several species and varieties which 

 demand particular observation. Fossil wood, which has been mine- 

 ralized by an impregnation with silex, HOLZSTEIN of the Germans, 

 and which we may term SILICIOUS FOSSIL WOOD, may be divided 

 into two kinds. The first is that, in which the wood had suffered 

 no real change in its nature, during its existence in a subterranean 

 situation, previous to that produced by the silicious impregnation. 

 The second is that, in which bituminization had wrought its peculiar 

 change on the wood, previous to its impregnation with silicious 

 matter. Of the former kind 1 know but one instance,, and that of 

 rather rare occurrence : which is, where the wood, previous to 

 having been buried, had undergone that change, which we fre- 

 quently see take place ; every part of the wood having been re- 

 moved but the mere ligneous fibre ; the light mass which is left 

 being in that state which is designated by the term rotten-wood. 

 The wood having been impregnated, whilst in this state, with silex, 

 yields an appearance exactly resembling that of rotten-wood ; 

 but occasions no small surprise to any one who, taking such a spe- 

 cimen in his hand, expecting from its appearance to find it ex- 

 ceedingly liglit, discovers it to be possessed of considerable weight, 

 from the great quantity of silex it contains. The specimen figured 

 at Plate II. Fig. 1. is of this kind, it having the peculiar light ap- 

 peara'ue of rottenwooJ, whilst its impregnation with silexhas 

 been to such a degree, as to have allowed it at one end to have 

 assumed a very high polish, from the lapidary's wheel. Since this 



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