FOSSIL VEGETABLES. 53 
and fruits, associated with other remains in the strata, but 
also in beds of great thickness and extent, consisting wholly 
of plants transmuted, by that peculiar process which vege- 
table matter undergoes when excluded from atmospheric 
influence, and under great pressure, into Lignite, and Coal. 
And there are intermediate stages of this process, in which 
the form and structure of the trees and plants are apparent ; 
and a gradual transition may be traced, from the peat-wood 
and submerged forests of modern epochs, in which leaves, 
fruits, and trunks of indigenous species are preserved, to 
those ancient accumulations of carbonaceous matter, whose 
vegetable origin the eye of science can alone detect. 
For the collection and preservation of fossil vegetables, 
with the exception of those which are permeated with 
pyrites (as those of the Isle of Sheppey, &c.), but few 
instructions are required. The silicified and calcareous 
stems are generally easy of extraction, even when imbedded 
in hard stone, and if broken can be repaired with glue. 
When the stems bear the imprints of leaf-stalks (as in 
Lign. 31 and 54), the surrounding stone should be carefully 
examined, with the view of detecting impressions, or other 
indications of the foliage. Delicate leaves in clay, or shale, 
must not be washed ; a thin coat of mastic varnish, or of 
gum water, applied with a camel-hair pencil, will preserve 
them, and render them more distinct. When a leaf, fruit, 
seed-vessel, or other fragile object is attached to clay or 
friable sandstone, it is advisable to glue the specimen to a 
piece of thin wood or pasteboard, of suitable proportions. 
The Sheppey fruits and other fossils permeated with iron 
pyrites, generally decompose after a few months’ exposure to 
the air. The fruits, especially, are liable to decomposition ; 
Mr. Bowerbank keeps his specimens in bottles of water; a 
solution of isinglass in spirits of wine is the best varnish 
to preserve such fossils, without obscuring their character 
and injuring their appearance: but even this method is 
