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 fluid 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 Chris- 

 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 is a 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 Lyell's Report, p. 231. 



