The borders of Oakmere abound with curious plants. One of the rarest of British grasses, the Calamagrostis stricta, grows here. The locality is also a noted one for the Utricularia minor, though we do not find that interesting fern of the Vale Royal wood, the Lastrea Thelypteris.
Contemplating this lovely mere, whether from Eddisbury, or its own borders, and remembering the many similar waters close by,[10] a group, after that one to which Windermere leads the way, without parallel in our island, it is impossible not to feel curious as to their history. The simple fact appears to be that all, or nearly all the Vale Royal meres are referable to the existence, underneath, of great salt crystal beds which give occupation to the people of Northwich. The surface–soil of the Cheshire salt district consists of a few feet of drift–sand or clay. Below this there is a considerable depth of “New red marl,” and below this there is good reason to believe there is a nearly continuous bed or deposit of the crystal. The “new red sandstone” rock in which these deposits are embedded, is very porous and much jointed. Water is constantly filtering into them from above; the salt crystal, exposed to its action, slowly dissolves into brine, which, as the height is at least a hundred feet above the sea–level, slowly drains away. Then the overlying strata gradually sink; depressions are caused, of less or greater magnitude, and in course of time these become basins of water. Mr. Edw. Hull, the distinguished geologist, considers that should the process go on, the whole of the valley of the Weaver will some day be submerged. Most of the salt sent from Cheshire is prepared from this natural brine. To extract the crystal is not so cheap as to let the water do the mining, then to pump up the solution, and evaporate it.
CHAPTER IV.
CARRINGTON MOSS.
“Will you walk into my parlour?” said the spider to the fly:
“’Tis the prettiest little parlour that ever you did spy.”