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sulphuretted hydrogen ; and the long continuance of this substance, 
in contact with the other principles, must give so superior a degree 
of energy to the natural processes, by which these substances are 
formed, as, perhaps, would leave to art, the power of only approxi- 
mating to their result. 
I have already furnished you with some particulars, respecting 
the form and appearance of pyritous wood, as well as concerning 
the situations in which it is commonly found. But as the following 
account, written upwards of a hundred years since, by Pillingen, 
whilst treating of the bituminous wood of Meizlibizen, is exceed- 
ingly particular and comprehensive, and was written without the 
intention of supporting an^ opinion resembling that which I have 
here advanced, I have laid it before you, that it may serve as 
a test, to show how far the conjectures which I have formed, re- 
specting its formation, are supported, or opposed, by the circum- 
stances under which this substance is found. A pit, he says, was 
lately dug in the declivity of the mountain, directly to the vein of 
bitumen, for the more easy extraction of the substances which were 
dug. Here they first found, for about three feet from the surface, 
common earth, with which a small portion of sand was mixed: 
they then dug, to the depth of two orgyia, through a vein of very 
fine clay, which was sustained by a firm sand, impregnated through- 
out, and blackened by bituminous vapours. At last, when they 
came to the surface of the bituminous earth itself, behold ! pyrites 
of a most uncommon form presented themselves to view ; so fabri- 
cated, had they been in the bowels of the earth, that their external 
appearance, in every respect, agreed with that of decayed wood. 
Other portions had other appearances ; for some resembled stakes ; 
others were so incircled by the knots of branches, &c. as to appear 
like smooth, cylindrical, and oblong sticks : some again, hollowed 
out, were woody on the concave inner surface, whilst the external 
and convex surface was brassy; others were turned, twisted, sur- 
