Alccount of a Remarkable Fossil Tree. 287 
where portions of it have been disengaged, and carried 
away ; but no portion of what remains is elevated more than 
a few inches above the surface of the rock. It is owing, 
however, to those partial disturbances, that we are enabled 
to perceive the columnar form of the trunk—its cortical lay- 
ers—the bark by which it is enveloped, and the peculiar 
cross fracture, which unite to render tlhe evidence of its lig- 
neous origin, so striking and complete. From these charac- 
ter being replaced by a mixed substance analagous in its ex- 
ternal character, to some of the silicated and impure calca- 
reous carbonats of the region. Like those carbonats, it is 
of a brownish grey colour, and compact texture, effervesces 
slightly in the nitric and muriatic acids, yields a white streak 
under the knife, and presents solitary points, or facets of 
crystals resembling cale spar. All parts of the tree are pen- 
etrated by pyrites of a brass yellow colour, disseminated 
through the most solid and stony parts of the interior,—fill- 
ing interstices in the outer rind, or investing its capillary 
pores. There are also the appearances of rents or seams 
between the fibres of the wood, caused by its own shrink- 
age, which are now filled with a carbonat of lime, of a white 
partially submitted to decay, and became w, before the 
process of petrifaction commenced, and that the interior 
