Page:A Treatise on Geology, volume 2.djvu/77

 CHAP. VI. a considerable portion of the vegetable mass. There are, however, peat bogs in which no timber lies buried; and many of these are daily and hourly augmenting their area, and increasing their depth, by the growth of living, and the accumulation of dead, plants. Though the gigantic "peat plant," as described by some writers, is an imaginary creation, sphagnum palustre and other humble mosses appear to deserve the epithet, and heather is a very common accompaniment. To an antiseptic property, imparted by this latter plant, De Luc was disposed to ascribe the conservation and accumulation of the various vegetable substances which occur in peat.

There are few shallow lakes in the interior of England, and especially in the sandy tracts, like Cheshire and Nottinghamshire, which are not, in some part or other, encroached on by the growth of peat. Preceded by reeds, this substance slowly advances over the sandy or pebbly bed, and changes to damp and shaking meadows the surface of the upper end of the lake. The upper end of Derwentwater, Ulswater, and many of the mountain lakes in Wales, display this growth of peat completely; and in many of the wide bogs of Ireland, the Isle of Man, and Arran, we see the process finished, and the lakes wholly obliterated in a spongy carbonaceous mass. In a similar way, many of the valleys without lakes, and many of the elevated slopes and summits of hills, especially on gritstone or granite surfaces, both in the south of England (Dartmoor), among the Yorkshire hills (Watercrag, Great Whernside), and the Cumbrian mountains (between Skiddaw and Saddleback), are covered with great depths of peat, in which trees are never seen. Similar facts appear among the Grampians, on the mountains near Enniskillen, and in other parts of Ireland; and these extensive tracts of "moor," as De Luc calls the peat deposits in the north of Germany, are supposed to be no where so abundant as in northern latitudes.

The bogs of Ireland lie principally in the central parts, on the wide plains of mountain limestone, and