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Seams of coal are spoken of as if they consist of a solid and 
uninterrupted mass of mineral, and this is often true in cases 
of thin seams; but for the most part seams are found to be 
_ made up of more than one layer, separated by earthy partings ; 
from which it is clear that in the case of thick seams there is a 
break or breaks in the accumulation of the mass. Next, as to 
_ microscopic structure. If we examine a piece of coal we find it 
to be built up of layers, which may be divided into bright and 
j dull layers. In the latter, as a rule, the spores of plants are 
met with ; some indeed may be said to be made up of them. In 
the bright layers, and in bright coals generally, these bodies 
are less numerous, and wood tissue becomes more abundant. 
Of the spores themselves there are two kinds, macrospores and 
microspores. Assuming that they belong to plants allied to the 
Lycopodiacee, it is clear that they cannot belong to the Lycopo- 
diec, as the latter have but one kind of spore. The Selaginellee is 
the only other family of the Lycopodiacee which are terrestrial 
plants. They have macrospores and microspores, and are 
considered by Mr Carruruers to be represented in carbonife- 
‘rous times by Triplosporites (Brown), but it is a question yet to 
be decided whether the coal plants were allied to that genus. 
There is another class of plants belonging to the Lycopodiacee ; 
these are the Isdetee which are of aquatic growth, and they 
have macrospores and microspores, which are very similar in 
appearance to those detected in coal. 
Coming to the cretaceous coal, the specimens of which were 
collected by the lecturer from a cretaceous coal or lignite, 
_which extends under a portion of the third Prairie Steppe of 
the north-west of Canada. It is difficult on inspection to 
believe that one is not looking at carboniferous coal; there are 
the bright and dull layers well defined, which at once suggests 
a like mode of deposition. The bright layers show, on 
microscopical examination, the same structureless material as 
