184 DR BENNETT ON THE STRUCTURE OF THE 
getable structure, is rich in the bituminoid substance ;—a circumstance, I think, 
explained by the fact that it is found in the neighbourhood of coal, so that the 
bituminoid or resinoid matter formed in the partially woody structure of the 
latter has flowed out, mixed itself with, and solidified in the essentially earthy 
substance of the former. It is easy to conceive how enormous pressure, con- 
joined with chemical change and heat, may have effected this, and how some- 
times such fiuid bituminoid matter may have run into neighbouring beds of peat, 
of clay, or even of sandstone. Facts, indeed, are not wanting to show that occa- 
sionally large collections of such substance, almost pure, may be formed, unmixed 
with either peat or clay, of which the remarkable specimen I now exhibit to the 
Society, taken from the Binnie Quarry, and for which I am indebted to Dr Curis- 
TISON, is an example. Fragments of this substance, under the microscope, closely 
resemble the yellow masses which exist in the Torbanehill mineral. 
In conclusion, I would remark that the controversy on this subject is only an 
example of a far more extensive one which is now everywhere taking place 
throughout the natural sciences, in reference to the influence which more im- 
proved methods of research in chemistry and histology should exercise on our 
thoughts and nomenclature. Those who, with myself, recognise that differences in 
structure indicate differences in function, and that these should be studied as the 
foundation for a correct classification, will recognise in the question, what is coal ? 
an analogue to the questions, what is wood or coral?—what is bone or tooth?— 
what isa fibrous or a cancerous tumour? The progress of science, and especially 
of micro-chemistry, has already answered some of these questions, and will ulti- 
mately determine others; and in doing so, will overthrow the more vague and 
incorrect views and terms which previously prevailed. At the trial, indeed, it 
was very plausibly argued, that, in a bargain between man and man, scientific 
terms were of no value, and that a whale among whalers was still a fish.* But 
in this Society, as no naturalist, conversant with the structure and functions of 
a whale, would for a moment suppose it to be a fish, because it inhabits the water 
and resembles one ; so I contend no histologist, acquainted with the structure 
and properties of the Torbanehill mineral, ought to maintain that it is coal, be- 
cause it is dug out of the earth and burns in the fire. 
* Mr Lyext’s Report, p, 231, 
