SEAL : FOSSIL PLANTS. 
165 
Modern students in geology have accepted the view that 
most of our coal- forming plants have grown on the spot 
where the beds of coal now exist. Professor Green, in his 
admirable work on " Geology for Students," while admitting 
that we occasionally meet with coal which has been formed 
under water from masses of drift timber and plants carried 
down by rivers and buried among mechanically aggregated 
deposits — such coal occurring rather in lenticular patches 
than regular beds, and apt to be impure from mixture of 
earthy sediments ; — arrives at the same conclusion as Logan, 
Binney, and others, that the under clays are old terrestrial 
soils, and that the trees and plants which grew upon them 
dried and fell to the ground, forming a layer of nearly pure 
vegetable matter. After a time, the surface was lowered 
beneath the water, but so gently that the soft pulpy mass was 
not disturbed ; sand and clay were deposited above them, and 
the band of dead plants was thus sealed up, and afterwards 
converted, by pressure and chemical changes, into a seam of 
coal. From distinct isolated specimens of the species I have 
named, which are found in the stone amidst the coal beds, we 
discover the nature of the plants of this era ; but the later 
deposits in the sandstone rocks are more perfect — in fact, so 
clear and distinct are some of them, that in many instances 
even the bark of the Stigmaria and Lepidodendron may be 
seen, but it is mostly decayed to a black powder. 
Calamites resembled the horse tail more nearly than any 
other living plant. The fossil specimens, however, were of 
enormous magnitude compared with the dwarfish examples 
of our own day, and appear to indicate a temperature 
which may be compared with the tropical climate of the 
present time. Many geologists hold the opinion that the 
large specimens found in our carboniferous rocks and 
coal measures are the result of high temperature obtained 
otherwise than that of tropical regions, and that the earth 
