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ances they yield, the parts in which they are found, and the nature 

 of the change they have suffered, I shall therefore now attempt. 



The vague manner in which the metallization of wood has been 

 hitherto endeavoured to be accounted for, will excuse me for ex- 

 tending this inquiry to a more than usual length. M. Walch* 

 who paid particular attention to this subject, says, the wood is, in 

 general, metallized, in those places, where the subterranean heat 

 raises a considerable quantity of metallic vapours ; and, upon these 

 vapours meeting with solid bodies, they deposit their metallic par- 

 ticles. Water, impregnated with metallic particles, he also sup- 

 poses, may convey the particles of metal into the interstices, and 

 cavities of the wood. 



It must be confessed, that considerable difficulties are to be 

 opposed, whilst endeavouring to determine the real nature of the 

 operation, by which a substance, which originally existed in an 

 organized state, has been so changed, as to be rendered metallic in 

 almost every part. Chemical analysis, as well as the natural de- 

 composition of these substances, shows that they are composed of 

 a portion of the ligneous substance, in most instances rendered 

 charcoal, intermixed with pyrites, or some saline metallic body. 

 The pyrites are frequently in so considerable a quantity, as to suf- 

 fer hardly any diminution of its metallic splendour from the inter- 

 mixed charcoal, which still serves to show the striae and circles, 

 which characterized its original structure. An inquiry into the 

 nature of the operation, by which this change has been effected^ 

 must necessarily involve in it the question by what natural ope- 

 ration are pyrites formed ? This question should, therefore, first 

 engage our attention. 



The formation of native metallic sulphurets, pyrites or marca- 

 sites, has been adduced, by Dr. Hutton, as clearly evincing the 

 agency of fire, and as entirely incompatible with aqueous solution. 

 The doctor says, speaking of the union of metallic substances with 



