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parts of the specimen was quite sharp and distinct, and different 

 from what must have taken place, had the flinty matter been intro- 

 duced into the body of the wood, by any fluid, in which it was dis- 

 solved. On the contrary, in numerous specimens now before me, 

 in which the fibres of the fossil wood are in some parts distinct, and 

 in others lost, I seek in vain for any line of distinction, as to the 

 penetration of the wood with silicious matter ; but see, in all, no 

 difference whatever, in this respect, in that part where the struc- 

 ture is confused, or where it is distinct ; nor do I find the least rea- 

 son to suppose, that the silex has not pervaded the whole, in the 

 most uniform manner. 



" In those specimens of fossil wood that are partly penetrated 

 by agate, and partly not penetrated at all," the Professor says, 

 " the same sharpness of termination may be remarked, and is an 

 appearance highly characteristic of the fluidity produced by fusion." 

 Here I have again to lament the never having had the opportunity 

 of seeing a specimen similar to those which are here alluded to. I 

 possess several specimens of agatine, opaluie, and jasperine woods, 

 the appearance of the external parts of which very nearly resemble 

 that of unchanged wood ; but examination soon shows that these 

 parts have also been fully penetrated by the silex. That such spe- 

 cimens do not exist, it is not my intention to assert ; it is quite 

 sufficient to remark, that such specimens would only prove that 

 the petrifying matter had only been applied to one particular part 

 of the wood ; a circumstance of which there certainly exists no 

 reason to prohibit the occurrence, in the case of the application of 

 an aqueous solution of petrifying matter. 



Mr Kirwan, indeed, quotes an account, that the Emperor of 

 Germany, being desirous to know the length of time necessary to 

 complete a petrifaction, obtained leave from the Sultan to take up, 

 and examine, one of the timbers that had supported Trajan's bridge 

 over the Danube, some miles below Belg *ade Jt was found, it is 



