4210 Royal Society of Edinburgh. 



distinguish his mineral ; mineralogists did not depend upon mere external characters 

 now-a-days (Professor Traill—" They never did ''), and the characters pointed out hy 

 the author of the paper did not involve differences of kind, but merely of degree. 

 [In an after speech this was denied by Professor Traill, and he seemed to lay great 

 stress on the external characters, which were of great practical value in distinguishing 

 minerals, iron and copper pyrites, for example ; and the only difference between the 

 charcoal and the diamond was a difference in hardness, for their chemical composition 

 was the same]. But Dr. Fleming, instead of acknowledging Dr. Traill's new 

 mineral, Bitumenite, did not consider it a mineral at all. It was not formed of cer- 

 tain elements in certain proportions, but varied much in different specimens ; and 

 from these and other considerations, it was not a mineral, but a rock, and it did 

 not differ more from coal than the Craigleith sandstone did from the Hailes sand- 

 stone, or the Redhall did from the Granton, or the sandstone of Salisbury Crags 

 did from all four. In the same way, the mountain limestone of different districts pre- 

 sented differences equally marked with those which distinguished the Boghead gas 

 coal from other kinds of coal. With respect to structure, he had seen specimens of 

 fossil wood wherein the slightest trace of organic structure could not be detected under 

 the microscope. 



Professor Bennet had devoted much attention to the microscopical characters of 

 the different coals, and wished to give his opinion merely on this point. He ex- 

 hibited drawings, from the microscope, of true coal, and the substance in question. 

 The latter exhibited markings, which he believed were regarded by the botanists en- 

 gaged in the inquiry as cells. Now, th«y wanted the character of cells. Hugo von 

 Mohl had shown the vegetable cell to be of the following anatomical structure : — It 

 consisted of, 1, a central nucleus ; 2, a primordial utricle; 3, a proper cell-wall ; with 

 also included granules. Now, these appearances he could not find in any specimens 

 of the substance submitted by him to the microscope. It was of great importance, he 

 considered, to determine whether the markings shown in his drawing were cells or 

 not, because the whole question hinged upon it, and if they were cells, then this 

 substance showed a structure so profuse in cells as to be unparalleled in any other 

 instance of coal. 



Dr. Greville had been called upon to examine the substance carefully, and 

 stated that although the markings in the drawing looked very like cells, still he was 

 not prepared to say that they were cells in their normal condition. They might have 

 been once cells, and become altered, but, at any rate, the substance seemed to have a 

 vegetable basis. 



Professor Balfour entered at length upon the question in its botanical bearings. 

 There could be no doubt but that organic structure, both vascular and cellular, 

 occurred in the disputed substance. He alluded to the opinions of Quekett and 

 others who had examined it with this view, and thought that it was wrong to draw any 

 argument against the substance being coal, from the fact that the structure seen was 

 not of a certain kind ; coal might be formed of coniferous wood, in other cases it might 

 not. We know well that various plants differing from the Coniferae — the Stigmarias 

 and others — occurred in the coal formations, and it was but reasonable to suppose that 

 these contributed to the coal deposits, as well as the Conifer®. It was impossible, 

 therefore, to set limits to the kind of structure to be found. As for finding the nuclei 

 and primordial utricles of cells, we could not expect that. With regard to the 

 general appearance of the substance, he also made some observations, and stated that, 



