FULLER : CARBONIFEROUS FOSSILS. 
199 
resulting: from the action of the weather on the arenaceous matter 
with which they were assumed to have once been filled. 
I would suggest, however, in view of the facts observed in Brock¬ 
ton, that these cavities were probably filled, not with the arena¬ 
ceous casts of Carboniferous trees, but with the calciferous mineral 
charcoal described. On exposure to the action of meteoric waters 
rich in carbonic acid the finely disseminated calcite would be dis¬ 
solved and removed in solution, leaving a porous mass of carbon¬ 
aceous matter, which itself would be slowly oxidized by the atmos¬ 
pheric agencies, giving finally the empty cavities observed. 
Printed, October, 1S96. 
