Note 14 — Progress of Science.

There are two distinct theories respecting the formation of coal, though all agree that it is of vegetable origin. This is proved by the trees and plants found in the substance of coal, by the vegetable remains imbedded in the accompanying strata, and by microscopical examination. The plants most abundant are ferns, some of which were of gigantic size. These are supposed to have composed two-thirds of the mass of most coal. Large trees are sometimes discovered growing upright in the shale that lies beneath and above a seam of coal. The vegetation from which coal has been formed, according to the views of some geologists, grew on the places where it is found, and they consider it to have been composed of decayed beds of peat which grew in succession one over the other, and that by the compression of the whole, when submerged, and by the accompanying action of heat, these vegetable beds were converted into coal. Other geologists imagine that it was produced by the accumulation of drift wood brought down by great rivers, similar to the present accumulation of drift wood on the coast of Mexico brought down by the great American rivers. There are geological facts adduced in support of both theories. Ireland presents the remarkable geological feature of an immense area of carboniferous rocks without coal, that valuable portion of the deposit having, it is supposed, been swept away by some of the denudations to which the surface of the globe has been exposed in the early periods of its history.—Prof. Morris.