120 
MODE OF DEPOSIT, 
preceding. No acciimulations now in process 
of formation on this fair earth, afford ade¬ 
quate analogy to the steps of this mighty 
process. 
The origin of coal is a much easier 
question to solve than the method in which 
it became placed where we now find it. 
The prevalent suppositions are that it 
either resulted from a mass of vegetation 
matted together, and drifted down by a 
large stream, similar to the floating trees 
of the Mississippi; or that it is the product 
of low luxuriant islands, which sank be¬ 
neath the waters, and were covered with 
accumulations of mud and gravel. The 
latter hypothesis most nearly accords witli 
the observed facts, as the plants are too per¬ 
fect to admit of the former supposition, 
save in a few instances. But owing to the nu¬ 
merous beds of coal lying with intercalated 
sandstones and clays vertically above each 
other, the problem requires an amount 
of alternations of repose and submergence, 
baffling even the computation of the philoso¬ 
pher. An instance from one coal field, and 
that by no means the thickest, will illustrate 
