THE OLD RED SANI'S TONE. 9235 
same variety of ichthyolite; and the circumstance seems 
fraught with evidence regarding both the original habits of 
the creatures, and the instantaneous suddenness of the de- 
struction by which they were overtaken. They seem, like 
many of our existing fish, to have been gregarious, and to 
have perished together ere their crowds had time to break up 
and disperse. 
Fish have been found floating dead in shoals beside sub- 
marine volcanoes — killed either by the heated water, or by 
mephitic gases. ‘There are, however, no marks of volcanic 
activity in connection with the ichthyolite beds—no marks, 
at least, which belong to nearly the same age with the fossils. 
The disturbing granite of the neighboring eminences was not 
upheaved until after the times of the Oolite. But the volcano, 
if such was the destroying agent, might have been distant; 
nay, from some of the points in an area of such immense 
extent, it must have been distant. ‘The beds abound, as has 
been said, in lime; and the thought has often struck me that 
calcined lime, cast out as ashes from some distant crater, and 
carried by the winds, might have been the cause of the wide- 
ly-spread destruction to which their organisms testify. I have 
seen the fish of a small trouting stream, over which a bridge 
was in the course of building, destroyed in a single hour, for 
a full mile below the erection, by the few troughfuls of lime 
that fell into the water when the centring was removed. 
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