387 
The well is sunk about three archines and a half below the surface, 
in a hole in the ground, consisting of parts of roots both of trees 
and herbs (which are partly mineralized), and intermingled with 
flakes of stones, then an archine and a half in a clayey kind of 
stone, mixed with a great quantity of sulphur pyrites. In the deep 
points of the valley, under the forementioned, there is a layer of 
vitriolic earth, which is a mixture of iron earth and swampy iron ore 
(bog ore). It is easily got, and is then taken to the vitriol works, 
and there boiled*. 
According to the degree of change which the vegetable matter 
has undergone, and the quantity of metal introduced, must of course 
its gravity vary ; hence the range of variation of gravity in different 
specimens of fossil iron wood is very great. The specimens in 
which the change has been considerable, will in general be found 
to be of pretty high specific gravity. These are chiefly formed of 
a brown rust-like metallic substance, sometimes marked by spots of 
a red colour, approaching to a crimson ; the form and texture of the 
mass readily leading to a recognition of its original mode of existence. 
By far the greater part of some specimens is evidently composed of 
pyrites, the rust-like substance appearing only on the surface ; but in 
these, there is great reason to suppose, that this covering has pro- 
ceeded from a partial decomposition during exposure to the air. 
It is necessary to observe, that, independent of those specimens, 
which, from the very large proportion of iron which they contain, 
deserve to be distinguished as metallic, there is scarcely any spe- 
cimen of fossil wood on which the indurating effects of iron does not 
appear to have been exerted. It is evident, that to the different 
precipitates of this metal, may be attributed many of the various 
beautiful colours which the several specimens of silicious fossil wood 
are found to display. 
* View of the Russian Empire, by William Tooke, Esq. vol. i. p. 86. 
