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 intermingFed with 

 flakes of stones, then an archine and an 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 evi- 

 dently 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 proceeded 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 speci- 

 men of fossil wood on which the indurating effects of iron does not 

 appear to have been exerted. Jt 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 WUliam Tooke, Esq. vol. i. p. 86, 



