652 Proceedings of the Royal Society 
have gained, and give it an appearance quite foreign to that of 
coal. Eut to what extent this porosity would be modified by the 
application of an immense pressure during the heating process we 
do not know ; this, however, is almost certain, that if it did succeed 
in preserving or giving to the coal a more mineral appearance, it 
could but partially reduce its vesicularity, and never so much but 
that it would readily be discerned — the increase of hardness sup- 
posed to follow by this process would only help to impede the 
effect of pressure, and preserve to the vesicules their exact shape 
and size. 
But in order to escape this, it may he argued that the gas in 
these pores has since been substituted by other matters in a state 
of fusion, or by condensed oils, &c. If, however, such had been 
really the case, we should surely have been able to observe indica- 
tions of it in the amygdaloidal state of the coal so found, since we 
could scarcely have given us the same characters to substances 
whose chemical composition and manner of formation are so dif- 
ferent ; this appearance would be especially manifested at the 
junction of those bands in the coal before alluded to ; in tho place 
of the divisional places being as now perfect, there would be in- 
numerable interruptions from some of the geodes occupying a 
position in both seams. That bands of a more recent date have 
obliterated the amygdaloidal appearance of the coal is too improbable 
to need any comment. 
It would therefore appear, that though the hardness of coal may 
be increased, even into that of coke, by heat, the coal thus obtained 
would be rendered proportionately lighter and more porous ; and 
that heat could induce the laminated appearance of coal, or favour 
its development, when begun, is very improbable, its effect would 
rather be to obliterate any previous lamination, and give to the coal 
a homogeneous appearance. 
Eut besides these objections against the supposition that high 
temperature has been concerned in the production of coal from 
organic matters, there are others — the non -necessity of such for the 
production of these chemical differences we observe between them ; 
for that there is no absolute necessity for this may be gathered 
from the heterogeneous nature of most samples of coals. In the 
case of the Newcastle coal, the difference in the parts, great as it is, 
