Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/52

 40 extremity. Another ridge of land, possessing a small and irregular elevation above the adjoining plain, may be traced from the hills on the eastern border of Cheshire, in a westerly or north-westerly direction to Halton and Runcorn. At this point, where it attains its greatest height, it is separated from the northern extremity of the former ridge, only by the intervention of the valley of the Weaver, which valley is here about two miles in width. Towards the eastern extremity of this range, we meet with a singular sandstone hill, called Alderley Edge, in which have been found ores of lead, copper and cobalt, and masses of sulphate of barytes.

This distribution of the high grounds in the Cheshire plain is traced out in the annexed map, and it will be seen, by a reference to this, that they form three distinct divisions of its area: one to the west of the higher sandstone range; another to the east of this, and south of the lower range ; and a third lying north of the latter, and including the southern parts of Lancashire. With the exception of in very few instances only, the existence of the rock-salt appears to be exclusively confined to the southern or central plain.

The marl beds form the most peculiar feature in the alluvial strata of the Cheshire plain. These occur in great abundance in every part of the district; being found not only under the common soil, but occasionally, as on the borders of Delamere Forest, interposed between layers of sandstone rock. The Cheshire marls are also very frequently met with in large detached masses, twenty or thirty feet in thickness, in the working out of which, it is not unusual to find large assemblages of fragments of the older rocks. Portions of granite, often of large size, and shewing on their surface evident marks of attrition, are among the most common appearances in these collections: no granitic rocks are found within fifty or sixty miles of this district.