176 DR BENNETT ON THE STRUCTURE OF THE 
yellow matter, resembling bees-wax, with only a few irregular spots of the black 
matter. In some sections, especially of the light-brown specimens, the rounded 
masses, as they are ground thinner, may be seen, as it were, to melt into one _ 
another (Plate I., fig. 11). In such sections, no difference whatever can be made 
out, whether they be made in a longitudinal or in a horizontal direction. But in 
certain sections, the yellow masses assume an elongated shape, so as to resemble 
the appearance represented, Plate I., fig. 9. 
In some thin sections these rounded transparent bodies can be separated from 
one another ,and be distinctly seen to possess a radiated crystalline appearance, 
strongly reminding one of the crystals of carbonate of lime which occur in urine. 
(Plate IL., fig. 1.) At certain angles, also, a few of them refract light, and be- 
come strongly tinted with the orange ray when polarized,—a circumstance per- 
haps dependent on the admixture of mineral matter. When a section of the 
mineral, presenting both the substances described is held over the flame of a lamp, 
the yellow matter evaporates in the form of thick smoke, leaving the black mat- 
ter unaffected, with large holes or loculi in it. It must be clear from this expe- 
riment that the yellow matter is some bituminous or resinous substance, easily 
decomposed by the heat of a lamp, and that the black matter is an earthy mate- 
rial, which resists the same amount of heat. We can have no doubt, therefore, 
that an easily volatilized and highly inflammable matter has concreted in the 
form of rounded masses, and constitutes the light-coloured portion of the mineral 
formerly described. Whether this be chemically the same as, or only allied to 
bitumen, resin, or amber, I leave to be determined by chemists. But we may at 
least correctly denominate it a Bituminoid substance, that is, one which closely 
resembles, even should it turn out not to be identical with, bitumen. The matter 
in which this is imbedded seems for the most part to be composed of clay, or 
_earthy matter which leaves a white ash, altogether destitute of structural traces, 
and is equally amorphous in whatever direction the section of the mineral is ex- 
amined. 
Some portion of the Torbanehill mineral, however, has a tendency to split up 
into thin laminee, and presents smooth or irregular depressions, dependent on the 
presence of Stigmaria or other fossil plants, which, in these places, come in con- 
tact with, or are imbedded in, the substance of the mineral. Thin sections of 
such portions exhibit masses of a rich brown colour, composed of scalariform ducts 
in great numbers, and occasionally the woody fibres and rings of coal. These 
latter are most common where the mineral forms a junction with coal, and where 
the one is more or less mingled, or alternates with the other. In these places the 
oreat difference in structure between them is easily recognized both by the naked 
eye, and by microscopic demonstration. By the naked eye, the black shining 
layers of coal are easily distinguished from the brown dull appearance of the 
mineral, and wherever such coal exists, the streak is dark and lustrous ; wherever 
