As the ice-sheet melted and the glaciers or ice-rivers retreated northwards when the climate became warmer, beds of sand, gravel, and stones were spread over the Cheshire plain. These are called drift beds. The stones and pebbles are rounded by the streams of melted ice and snow which flowed from the mouths of the ice-rivers. Upon the beds of drift lies the surface soil in which grow the crops and grass, the herbage and the woods of to-day; and it is in the drift, as you will see in a later chapter, that traces of the earliest inhabitants of Cheshire are to be found.
CHAPTER III
THE MAKING OF CHESHIRE (cont.). II
The Older Rocks
Let us now visit some quarries in East Cheshire. We shall find considerable difficulty in reaching some of them. It will be necessary to get permission from the owners of the quarries, put on a special suit of clothes, enter an iron cage, and descend many hundred feet perhaps into the depths of the earth's surface until we find ourselves—in a coal-mine!
Section of Rocks from Knutsford to Buxton
Unlike the New Red Sandstones, which are found for the most part in flat horizontal beds, the coal beds slope downwards from east to west. This is due to the uplifting of the East Cheshire hills, which we shall presently explain. When this uplift took place, the coal beds, which were originally flat, became raised in the east and equally lowered in the west. When the sea flowed over them they became covered by sandy deposits of such a thickness that in the greater part of Cheshire the coal cannot be reached. The earliest sands laid down formed what are called the Permian rocks, and the later layers the New Red Sandstone series mentioned in the last chapter. The Permian rocks may be well seen at Stockport, in the river beds of the Tame and the Goyt which have cut their way through them. In the strip of country between Stockport and Macclesfield, and again on the south-eastern borders of Cheshire, the upturned edges of the coal beds have been left exposed so that the coal is near the surface and can be easily extracted.
Coal consists of the vegetable remains of forest trees and their undergrowth. If you look at a lump of coal you will see that it has been pressed down into thin layers like the leaves of a book. When these layers are split apart there are often found the fossil remains of leaves and roots of trees, fronds of ferns, seed-cones and stems of plants which grew in the forests. Some of these, particularly the ferns, are often of great beauty. You may see a number of these 'coal pictures' in the Vernon Park Museum at Stockport. Here too you will find portions of the actual trunks of trees that have been dug up just where they stood when the seas flowed over them.
You may learn even to distinguish different varieties of these forest trees, just as you are able to distinguish the oak and the beech and the elm of to-day. Latin names such as Sigillaria, Lepidodendron, and Salisburia have been given to them. The most beautiful of all is a Maidenhair Tree-fern. The Calamites was a huge 'Horse-tail' plant of which you may find small varieties to-day on banks and in hedgerows.
On the coast of Wirral, between Meols and New Brighton, are the remains of a forest which has only in very recent years been covered by the sea. Boys who live in this neighbourhood may have heard their parents tell of the stumps of tree-trunks sticking out through the sands when the tide was low. This shows that the land is continually undergoing changes, at one time being raised above the seas, at another time sinking beneath the waves.
The beds or 'seams' of coal vary in thickness from a thin film to several yards, and are separated from one another by layers of hard clays and flagstones. From the flagstone beds are obtained the square slabs with which the pavements of our towns and cities are laid. In many of the quarries near the Cheshire coal-field you may watch the workmen cutting and shaping these stones.