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149 
the Forest of Dean. The Spores exhibited by Dr Dawson had 
been discovered by Professor Epwarp Orton, Columbus, Ohio, 
and had been referred to in a paper read before the American 
Association for the Advancement of Science in 1882. The Pro- 
fessor on being written to kindly sent specimens of the shales. 
The Ohio Black Shales rest upon the uppermost Devonian 
Rocks, and represent a thickness of from 250 to 350 feet. The 
deposit is considered by the American Geological Society as a 
. dividing line between the Devonian and Carboniferous for- 
mations, they are of special importance as yielding mineral 
oils. It is important to note that the horizon of the beds, in 
Ohio, which yield the Black Shales, are precisely similar to those 
of the Forest of Dean Shales, which yield the vegetable remains. 
Identically similar spores have been found by Dr Dawson in 
the Erian formation of Kettle Point on the Huron, which 
strata are assigned to the Upper Devonian. The facts are 
remarkable, inasmuch as they point to a similarity of conditions 
which ushered in the great carboniferous period, and closed 
the Devonian over widely separated areas; conditions which 
allowed of the accumulated growth of vegetation in dense 
masses, and of close relationship in type. As respects the 
spores themselves, there is a close resemblance between those 
from the Forest of Dean and those from America; some are 
certainly of the same genera if not of the same species. From 
the Forest two varieties can be made out; those from Ohio are 
usually of larger size. Some of those from Drybrook show 
triradiate markings, which is a fact of importance in determining 
their connection with existing forms of vegetation. In con- 
sidering this latter point, it would be rash to class them 
definitely with existing plants, having consideration of our 
limited knowledge of the vegetation which yielded the spores. 
We have then, in the Forest of Dean, the same class of 
vegetation which by decomposition has yielded the well-known 
stores of mineral oil in America, and the question naturally 
- arises “Is oil to be got from the Forest of Dean Shales?” The 
Ohio Shales give from 8 to 22 per cent. of organic matter. A 
fair example from Drybrook gave 17 per cent., 6 per cent. of 
