TRUE COAL MEASURES. 
145 
There are some accumulations of wood 
even now in course of formation which re¬ 
mind us of the phenomena of the coal 
measures. 
Such are the lignites of North Germany 
already mentioned, the wood-hills of new 
Siberia, and the vast heaps of drifted tim¬ 
ber, visible along the coasts of the northern 
seas; in some places interstratified with 
layers of sandstone, and bituminized in the 
process of decay. Such also must be the 
beds of lignite laid on the floor of the ocean 
at the mouth of the Mississippi, whose 
turbulent waters constantly bear forward 
the spoils of the mighty forests through which 
it flows. But none of these results are 
comparable, in point of extent, or amount, 
with the rich strata of our collieries. 
It has been computed that the woody 
matter contained in the growth of a 
thousand years, in a dense tropical forest, 
would not constitute a layer of mineralized 
fuel half an inch in thickness. How is it 
then possible to assign to the present 
rate of agency of causes now in opera¬ 
tion, the production of the numerous 
N 
