When, in the course of time, the red sandstone formed the dry land of Cheshire, it became covered by a great ice-sheet which extended over Britain even as far south as the Thames valley. Beneath this covering of ice the rocks were crushed and ground to atoms by the movement of the ice-sheet over them. This formed beds of a substance called boulder-clay, containing lumps of rock which must have been brought by the ice great distances, for they are of a kind found only in the north of England or in Scotland. Some of these 'boulders' are of great size. Several have been placed in Vernon Park, Stockport, and in the West Park, Macclesfield, you may see one that was dug up in the neighbourhood of the town. It weighs about thirty tons. On Eddisbury Hill is a mass of rock, ten feet long, of a kind found only on Skiddaw in the Lake District, and in the narrow lane behind the 'Wizard' Inn on Alderley Edge is a lump of granite from Eskdale, so that these rocks have been brought by the ice a distance of a hundred miles. Such blocks and boulders are called 'erratics', because they have wandered so far from their original home. Another proof of the existence of the ice-sheet may be seen in the scratchings and marks (called 'striae') on pebbles and rocks found in these beds. In the lane outside the church at High Legh are a number of large boulders which still show the lines of furrows and scratchings made on their surface by the movement of the ice over them. The boulder-clay has been worn away by the action of water and weather from a great part of Cheshire, but in the west of the county large patches may be seen in the low-lying districts. You may observe the beds most clearly in the cliffs of boulder-clay on the estuary of the Dee between Heswall and West Kirby. In the neighbourhood of Chester, many of the villages--Tarvin, Christleton, Aldford, Saighton, and Barrow, for instance--are built on sandstone knolls and ridges which stick up through the boulder-clay, for the sandstone is drier and healthier than the clay to live upon, and the wells, especially those in the Bunter beds, provide the purest water. 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