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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 gene- 
ral, 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 particles. 
Water, impregnated with metallic particles, he also supposes, 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, shews 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 suffer 
hardly any diminution of its metallic splendour from the intermixed 
charcoal, which still serves to shew 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 operation are 
pyrites formed ? This question should, therefore, first engage our 
attention. 
The formation of native metallic sulphurets, pyrites or marcasites, 
has been adduced, by Dr. Hutton, as clearly evincing the agency of 
fire, and as entirely incompatible with aqueous solution. The doc- 
tor says, speaking of the union of metallic substances with sulphur. 
