THE PEAT CLISTASE. 



395 



tion in the recession of the ice was due to a cooling in climate. The ice then 

 began again to recede at the rate of about 20 m. annually for the first 300 

 years. Subsequently, a rapid amehoration of climate appeared, and the 

 annual melting increased 250 m. and northwards to as high as 400 m. Several 

 series of cooler years were noted in different parts of the great area of melting. 

 There was also a period of marked increase of temperature corresponding to 

 the plant remains in the peat-moors, and to the marine fauna which lived in the 

 neighborhood of the receding ice. On the basis of these relations it is con- 

 cluded that it should be possible to investigate accurately the late glacial 

 climatic changes of northwestern Europe and probably also of North America, 

 and to answer the question as to the alternation of climates assumed in Blytt's 

 theory of wet and dry postglacial periods. 



Haglund (1909) has smnmarzied his views concerning the sequence of layers 

 in peat. He dissents from the Blytt-Semander theory of the alternation of 

 climatic periods: 



The development of each moor progresses independently of precipitation, 

 from moist to drier stages until the development ceases. In the high moors, 

 a new formation of peat by Sphagnum and Erwphorum has taken place in 

 consequence of flooding. Between this upper peat and the lower low moor 

 is foimd a stmnp-layer, which is derived from an earlier forest destroyed by 

 fire. In the numerous cases where the author has found pure Sphagnum peat, 

 with or without Eriophorum, a carbon layer is always present. Forest hinders 

 a part of the rainfall from reaching the soil and also uses much of the soil-water 

 in transpiration. As a consequence, the moor becomes dried out. The 

 disappearance of the forest as a result of fire permits a rise in the groimd- 

 water and the change into moor begins. The soil is made poorer in nutrients 

 by the fire, and Sphagnum and Eriophorum enter and cause peat formation 

 anew. According to the author, Sphagnum moors are foimd in regions which 

 have long been influenced by culture, but are lacking on the other hand in 

 uncultivated regions. There is therefore a highly probable correlation between 

 the age of a culture in the district and the transgression phenomena of the 

 moors. These are dependent upon the time of the disappearance of the 

 forests, and can not be assigned to a definite geological period. 



Hartz (1909) has described the Tertiary and Pleistocene flora of Denmark: 



In the brown-coal layers of the Tertiary have been found Pinus laricio, 

 Sequoia langsdorfii, Laurus, and species of Ainws, Betula, Tilia, and Ulmus. 

 The author dissents from the older driftwood theory of the formation of 

 these deposits. Since there is always a distinct layer of fresh-water slime 

 (gytje) under the coal-layers, he assumes that the coal has the same relation 

 to the slime-layer as do the peat-layers to the underljang slime-layers in the 

 postglacial wood-bogs. The author has shown in im earlier investigations 

 that Jutland contains a number of fossiliferous interglacial layers. These 

 often consist of diatoms, and in one locaUty of Brasenia purpurea, Carmnus 

 betulus, Dulichium spathaceum, and Picea exceha. Usually there' is a flat 

 bowl-shaped depression in the soil-surface over such interglacial bog-basins' 

 the peat becoming strongly depressed under the weight of the overlying 

 diluvial layers. These reach a thickness of 5 m. and consist of sand with a 

 few stones These overlying sand-layers are regarded as stratieraphical 

 evidence of the mterglacial age of the fossiliferous beds. The characteristic 

 plants are Picea excelsa and Carpinus betulus, both of them imknown in nost- 

 glacial bogs in Denmark. ^ 



