2

accumulation of coal-that it accumulated where the vegetation grew, and that the place was not far from high-water mark. Besides the evidence of the spores, moreover, we have that of sundry other fossils found with the coal. We find terrestrial creatures, such as scorpions, which are not readily distinguishable from those living at the present day. We find beetles; and in one remarkable case, in Canada, a trunk of a tree was found which was filled with sandstone. As this trunk was standing upright, it is extremely probable that in the old days it was the hollow stump of a tree, and that, in the old carboniferous days, as at present, the hollow trunks of trees formed a trap for small creatures to fall into and die. So Dr. Dawson3 investigated, bit by bit, the contents of this fossil hollow trunk, and he found a small worm which is scarcely to be distinguished from a living centipede, and a small land shell which is not very far removed from a modern one. Those two forms of life in that trunk testify to the fact that the coal was accumulated on the land, and not in the sea. There are many other forms of life in the coal. We have large creatures of the reptilian kind, allied, more or less, to our frogs and newts.

4

6. Apart from its surroundings, I have hitherto spoken of coal itself. It is always associated with sandstone and shales, which are indisputably derived from the wear and tear of the land by water. The first difficulty that strikes us in regard to the formation of a bed of coal is -how is it that while it is associated with sandstone and shale and clay, it is so purely vegetable. But if wo refer to the great cypress swamps on the banks of the Mississippi," we shall easily gather a reason for that. There we find large quantities of peaty matter accumulating, which is more or less enveloped in the floods

every spring; but those floods of the Mississippi lose all their sand and mud long before they arrive at the peaty matter. Round those swamps there is a fringe of rushes and mosses, which completely strains off all earthy and sandy material, and the result is that in the interior you get a perfectly pure vegetable matter, very much like that of which our coal is composed.

7. I have no doubt whatever that the purity of our coal is in part owing to the earthy matter being strained off by these grasses, sedges, and rushes, which subsequently disappeared. It is, however, easily explained by the simple fact that the vegetation accumulated where it grew. Indeed these old coal layers call to mind our peat bogs. We find a layer of peat nearly everywhere on our coast line between high and low water mark,—at Fleetwood, in Lancashire, for instance,—which is perfectly pure and free from extraneous matter, although it is based upon a layer of clay, and covered by marine. sand. Each layer of coal represents a mass of vegetable matter accumulated on the ancient land surface, just like that of the Lancashire coast, while the sandstones and shales were deposited by water on the submerged lands; and each of the many layers of coal represents a new submergence; and to show you that it is not unreasonable to suppose that in the coal epoch, changes of level did take place, I may adduce one or two instances which have taken place during this century. In the valley of the Mississippi, in 1812, an earthquake took place, and a large area of country in which the cypress trees grew was sunk beneath the level of the water; and the stumps of cypress trees and the peat were completely covered up with alluvium, very much as any seam of coal might be now-a-days. In India, in 1819, a large alluvial plain was suddenly submerged by an earthquake, in the Gulf

8

of Cutch, and a solitary fort, which marked the extent of the depression, was left half out of the waters. Like causes produced like effects in the coal measures.

8. The next question for us to discuss is-how these changes of level are brought about; and that is not at all hard to answer. They are caused altogether by the internal heat of the earth. I dare say that many of you know that, in the mines, the deeper you go the hotter the atmosphere becomes. Speaking roughly, the increase of temperature in going down into any part of the earth's crust is one degree for 65 feet of descent. Sir C. Lyell has estimated that at a depth of two miles we should arrive at the temperature of boiling water, and at a depth of 34 miles we should arrive at the temperature of molten iron. This heat manifests itself in the hot springs which we find at Bath and other places, and in volcanoes; and it is this internal heat which has caused the depressions of the land on which the coal was accumulated.

9. You know that if you heat a poker, it expands, the heat making it longer. The earth is in the same state as a hot poker, and parts of it expand or contract as the heat within it ebbs and flows. If the heat ebb away from one portion, the land above will be depressed, if it flow towards it, it will rise. In this way all the changes of level can be explained.

10. You will naturally ask,-How long ago is it since the coal was formed? I am extremely sorry that I cannot tell you. It is so long ago that we cannot grasp the idea of the lapse of time. In the Manchester coal field, we have no less than 6,800 feet of deposit, and in it we have no less than 60 feet of workable coal. But the Lancashire coal field is not the thickest. There are coal fields in the Forest of Dean and in America, which are much larger and much thicker. The coal fields must

have demanded a vast amount of time for their accumulation; and the carboniferous epoch is separated from us by an interval too great to be bridged over by any unit of time which can be devised.

SPELL AND GIVE THE MEANING-

NOTES.

GREECE.

1. GREECE was the first country in Europe which rose to a high place, not only for arts and laws but for the dis

play of splendid ability in all the various powers of the mind.

2. We know very little of it till about five hundred years before Christ, but it then re

veals itself as,

long before, pos

sessing the great

poems of Homer1

which are sup

CORINTH,

posed to be as old as the age of David, the King of Israel, 1,000 years before Christ.

3. Greece is a

very mountainous country, and people were then SO fierce and given to war that the dwellers in the valley on one side of a