166 
SEAL : FOSSIL PLANTS. 
was originally an incandescent or highly heated mass, and 
was gradually cooled down sufficiently to render the early 
gneiss and mica schist crystalline ; cool enough during 
Grauwacke and Silurian eras to permit of marine corals, 
shell fish, or Crustacea ; cooler still during the life of the 
plated fishes of the old red sandstone ; and sufficiently genial 
throughout the carboniferous period to foster a growth of 
terrestrial vegetation over the surface. It is thought by 
Brogniart and others that this high and uniform temperature, 
combined with a greater proportion of carbonic acid gas in 
the atmosphere, would sustain the gigantic and prolific vege- 
tation necessary for the formation of beds of coal. Thus all 
the conditions would have arisen for extensive deposits of 
vegetation, which would, in course of time, with the accumu- 
lated weight of superincumbent deposits, undergo a state of 
petrifaction by the waters passing through the different 
deposits of sand and mud ; and thus, through the lapse of 
untold ages, become completely stripped of all vegetable 
matter and be turned into stone, some of them being largely 
impregnated with iron. 
In conclusion, I venture to give an opinion upon a point 
on which geologists differ, namely, as to whether the con- 
tortions and breaks in our rocks are the result of an 
upheaving agency. I grant that some of the rocks are so 
broken and contorted that they have the appearance of 
having been subject to internal pressure, but my opinion is 
that the breaks or joints that we find have gradual^ taken 
place during the period of their deposition, and are not the 
result of upheaving convulsions. However, my object has 
not been to advance any crotchets of my own, but simply to 
place on record some account of the fossils found in the 
Darfield rocks. 
