COAL. 77 
peat-wood, brown-coal, lignite, and jet, to coal, anthracite, 
graphite, and plumbago. Nor must the meritorious labours 
of that accomplished naturalist, and excellent man, the 
late Mr. Parkinson, author of the “Organic Remains of 
a Pormer World,” in this field of research, be forgotten.* 
The first volume of that work, which treats on fossil plants, 
contains much original information on the transmutation of 
vegetables into the various mineral substances in which the 
nature and original structure of the originals are altogether 
changed and obliterated; it may still be consulted by the 
student with advantage. 
Although the vegetable origin of all coal will not admit 
of question, yet evidence of the internal organization of the 
plants of which it is composed, is not always attainable; for 
the most perfect coal has undergone a complete liquefaction, 
and if any portions of the structure remain, they appear 
under the microscope as if imbedded in a pure bituminous 
mass. ‘The slaty coal generally preserves traces of cellular 
or vascular tissue, and the spiral vessels, and the dotted 
cells of coniferous trees, may readily be detected in 
chips or slices, prepared in the manner previously pointed 
out (ante, p. 66). In many examples the cells are filled 
with an amber-coloured resinous substance; in others the 
organization is so well preserved, that on the exposed 
surface of a piece of coal cracked by exposure to heat, the 
vascular tissue, spiral vessels, and cells studded with glands, 
may be detected. Even in the white ashes left after com- 
bustion, traces of the spiral vessels are often discernible 
under a highly magnifying power. Some beds of coal are 
wholly composed of minute leaves and disintegrated foliage ; 
and if a mass recently extracted from the mine be split 
asunder, the surface is seen to be covered with flexible 
pellicles of carbonized leaves and fibres, matted together ; 
and flake after flake may be peeled off through a thickness - 
* See my “Pictorial Atlas of Organic Remains,” 1850. 
