CHAP. XLIX HIGH-MOOR FORMATION 203 



may attain a thickness of 3-4 metres, or in East Prussia even of 6-10 

 metres. Peat is produced not only by species of Sphagnum, but also 

 by Polytrichum juniperinum, Scirpus caespitosus, Eriophorum vagina- 

 turn, Erica and Calluna, and others. Remains of animals and other 

 objects may be enclosed and preserved in peat. Humous acids efficiently 

 prevent the putrefaction of organic bodies ; the water of moor contains 

 few or no bacteria. Parts of plants, such as leaves and fruits, and even 

 remains of human beings and animals, may be preserved for thousands 

 of years in the water of moor. 1 



Forest-moors in northern Europe arose thousands of years ago in 

 small lakes or pools within forest, and were formerly surrounded and at 

 least partially or temporarily overgrown by trees. They now contain 

 rich stores of plant-remains, which depict the evolutionary succession 

 of the local vegetation and flora. The substratum of such moors is often 

 constituted of fine clay deposited from the neighbouring heights shortly 

 after the Glacial Epoch, together with remains of Dryas, Betula nana, Salix 

 polaris, S. reticulata, and other tundra-plants, which formed the first 

 vegetation on the moraines when these had been deserted by ice after 

 the Glacial Epoch. 2 The later evolution of these forest-moors has been 

 elucidated by Steenstrup 3 in his excellent work on those of Vidnesdam 

 and Lillemoose in Danish Seeland. According to Steenstrup the first 

 tree-growth after the tundra period was produced by Populus tremula, 

 which was accompanied by mosses, including species of Hypnum and 

 Sphagnum : thus began the formation of moor. Betula also appeared 

 early and accompanied the succeeding strata. Gradually the lakes 

 became fringed with forest vegetation, the trees of which fell into the 

 bog, and, together with leaves and fruits conveyed by wind, were buried 

 therein. The first high-forest was constituted of Pinus sylvestris ; this 

 gave way to Quercus sessiliflora and Q. pedunculata, and these to beech, 

 which is only very scantily encountered in the uppermost layers of the 

 moors. 4 Blytt 5 thought that he had discovered in Norway an alternation 

 of strata of peat and of forest (tree-stems) corresponding to an alternation 

 of moist and dry periods, and he employs this evidence to support the 

 theory of the climatic alternation. Possibly it is merely a case of the 

 conversion of forest into marsh under the influence of increased humidity 

 due to local conditions. When forest has been exterminated by conver- 

 sion into marsh, the soil ultimately becomes drier, and forest once more 

 seizes upon the place. Forest-moor is richer in remains of trees than 

 is low-moor, and contains more numerous aquatic mosses than does 

 the latter. 



According to Cajander, 6 the moors of northern Europe are under- 

 going regressive development ; for example, on the White Sea they are 

 being changed into hilly land which sometimes shows immense hillocks 

 of peat ; Cajander is of the opinion that, with increasing latitude, and 

 possibly with increasing altitude (in the Alps), this regressive develop- 

 ment becomes more accentuated. 



In regard to high-moor in Scotland, seeW. G. Smith, 1902; Lewis, 1905-1907. 



Nathorst was the first to discover remains of this kind in Sweden in 1870. 



Steenstrup, 1841 ; see Chap. XCVI. 



Steenstrup, loc. cit. ; Vaupell, 1851-63. 



Blytt, 1882, 1893. Cajander, 1905. 



