4 
from Coniferous plants. Out of 300 specimens of bituminous 
wood, collected in the Silesian brown coal deposits alone, 
scarcely any other kinds occur besides the wood and fruit of 
a Taxus and Cupressinea. In other districts, the Pinites 
protolarix occurs. The number of species of Coniferiae, 
however, upon the whole, is very small in comparison with the 
enormous mass of brown coal they have contributed to form, 
from which he infers that the Coniferiae of the ancient world 
had a similar gregarious mode of growth with those that now 
flourish on the earth.* Similar facts appear to have been 
noticed by the venerable Humboldt, who observes in his last 
work, " Where several series of coal strata lie over one 
another, the genera and species are not always mixed ; they 
are rather, and for the major part, generically arranged so 
that only Lycopodites and certain ferns occur in one series 
of beds, and Stigmaria and Sigillaria in another."f 
Although the Newcastle coal-field does not appear to have 
afforded any positive evidence upon this point to the authors 
of the Fossil Flora, they nevertheless inferred the fact, as 
will be seen by the conclusions at which they arrived. After 
stating that there are three principal varieties of coal in the 
Northern coal-field — the Fine caking Coal, the Cannel splint 
or Parrot Coal, and the Slate Coal, wdiich in some instances 
occur in the same seam or bed, where they are not indis- 
criminately mixed, but have a well-defined line of separation, 
they observe, u It is certain each bed of coal, and more 
particularly each separate layer in that bed, must have been 
placed in precisely similar circumstances since the deposition 
of the vegetable matter of which it is composed ; and we 
cannot suppose that matter to have obtained any of its 
elements after it was buried in the earth, but rather that 
the difference between the several varieties of coal arise 
* Quarterly Journal of the Geological Society, vol. v., pt. ii., p. 6. 
t Kosmos, vol. 1, p. 299. 
