VOL. XIV.(1) |THE PRESIDENT’S ADDRESS 9 
the close of what I may term this limestone-forming stage, 
the sea-floor was apparently gradually rising; and, instead 
of deposits of remains of marine organisms, there came an 
arenaceous deposit, that is to say, detrital material brought 
down from the denudation of land, containing a quan- 
tity of quartz, or sand. This we know from the fact that 
the limestones are followed by a thick deposit of sand- 
stone (quartzite), known as the Millstone Grit. 
In some parts of England and Scotland actual seams of 
coal occur in the limestone and Millstone Grit. In the 
West of England there are none in the limestone, but 
there are a few carbonaceous deposits at the top of the 
Millstone Grit. Strictly speaking, however, in the West 
of England, we may say that the Millstone Grit in its turn, 
so to speak, gave place to actual land surfaces, and on these 
grew the coal-forming vegetation. 
If we examine a piece of ordinary bituminous coal we 
notice that it is made up of irregular layers. Some have 
a bright lustre, others a dull, somewhat brown colour. 
Microscopic sections of the latter show these layers to be 
accumulations of countless spores of plants," some of them 
remarkably well preserved. On the other hand the bright 
lustrous layers, when sectioned and examined under a 
microscope, are seen to be made up, for the most part, of 
structureless material, which, for want of a better name, I 
have called hydrocarbon. Vegetable tissue is also at times 
to be seen. 
The smokeless steam coals of South Wales, as far as I 
have examined them, are somewhat different. There are 
no defined bands of spores; and when structure is preserved 
it consists, for the most part, of highly carbonized vege- 
table tissue, the exact nature of which it is difficult to 
determine. 
1 See my paper in these Proceedings, Vol. viii., p. 168; 1885. 
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