SURTURBRAND. 
141 
it has undergone are induration and com¬ 
pression ; having been impregnated with 
bituminous sap, and flattened by the enor¬ 
mous weight of the superincumbent rocks. 
Some few branches stretch at times across 
the bed, but in general they all lie parallel 
with one another, and are frequently press¬ 
ed together, so as to form a solid mass. 
The third stratum is not so pure, being 
mixed with a considerable portion of fer¬ 
ruginous matter; grey externally, but black 
in the fracture, has no lustre, and is much 
heavier than the former, yet possesses evi¬ 
dent traits of its vegetable character. The 
fourth or uppermost stratum consists of 
what the Icelanders call steinbrand^ or 
coal, from which it differs only in the ab¬ 
sence of the gloss, and its containing a 
quantity of earthy matter. It still retains 
some faint marks of wood. 
Remarkable as the appearance of this 
rock-wood undoubtedly is, a still more sur¬ 
prising phenomenon makes its appearance 
between the second and third strata, viz. a 
bed of dark grey schistus, about four inches 
in thickness, that admits of being divided 
