170 
been suggested by Dr Sterry Hunr,* but at the same time Dr 
Honr is disposed to assign the origin in some instances to the 
decomposition of animal remains. He says—‘‘ When, however, 
it is considered that the lower forms of animals contain con- 
siderable proportions of a non-azotized tissue analogous in its 
composition to that of plants, and that even muscular tissue, 
plus the elements of water, contain the elements of cellulose 
and ammonia, it is easy to understand that vegetable and 
animal remains may, by their slow decomposition, give rise to 
similar hydrocarbonaceous bodies.” Dr Newserry, referring to 
the same subject, writest— Waiting the demonstrative solution 
of the problem, which patient and exhaustive study will doubt- 
less sometimes furnish, I offer as a possible explanation of the 
peculiar feature of the Huron Shale the suggestion that its 
carbon was derived from vegetation which lined the shores and 
covered the surface of a quiet and almost land-surrounded sea.” 
A similar view has been expressed by Professor AnprEws;{ but 
it was not until the spring of 1881 that any confirmation of the 
theory was obtained, when Professor Orton discovered in the 
Huron Shales, 1000 feet below the surface, ‘‘ minute trans- 
lucent discs, resinous in appearance, and unmistakably organic,” 
occurring in great numbers, (Figs. No. 6 and No. 7.) Later on 
further proof was produced, by the discovery of these bodies in 
the ‘Black Shales” of Columbus, Ohio, and finally they were 
found to occur throughout the ‘ Black Shales.” 
The Shales in the Forest vf Dean are very insignificant com- 
pared with thosein Ohio. They are at the top interstratified with 
limestone, and towards the bottom with arenaceous beds; the 
total thickness would not exceed twenty feet. Spores of plants 
occur, however, in the Shales (Fivs. 1, 3, 4, 5), and though 
they are not so large as some from America (Figs. 6, 7), there 
is great similarity between them, and a microscopic section 
of the beds shows them to be full of decomposed vegetable 
remains. The Shales are bituminous; a fair average sample 
* “ Chemical and Geological Essays,” p. 179. 
+ No. I. Vol. “Geol. of Ohio,” p. 156. 
{ ‘“ Report of Progress of the Ohio Geol. Survey for 1869,” p. 65. 
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