40 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



heaths, which develop the peat foundation. The lake closed, forest 

 vegetation, birch and fir, advances ; the firs do not grow high, but 

 they break ofif after attaining a certain height and weight, sinking into 

 the soft material, where they are converted into peat, as is the less 

 imposing vegetation. They are readily overturned by the wind, so 

 that peat is crowded with birch and firs. Peat originates partly from 

 mosses, partly from water-plants, partly from swamp-plants, especi- 

 ally the grasses and rushes, partly from woody plants. The hard 

 parts change slowly while the softer parts become a pulpy mass 

 enveloping the others. By climatic changes a Waldmoor may be con- 

 verted into a Torfmoor and that again into a Waldmoor, giving a 

 section in which a succession of forests is shown. 



Three years later, von Post-® grouped the successive deposits into 

 mud (Gyttja), mud-peat (dytorf) and peat (torf), his conclusions 

 being the outcome of more than 20 years' experience in the peat 

 industry. In 1893, he presented a resume of his studies as a lecture 

 before the Upsala Institute. He had found that most of the Swedish 

 peat mosses began in water-basins and that the bottom material, clay, 

 mud or calcareous tufa, is sediment from more or less muddy water. 

 A most important stratum is the brown earth, Dy in Swedish, which 

 was formed by precipitation from the brown waters, containing 

 huminic substances, quite analogous to the brown waters of rivers. 

 These huminic substances, leached from accumulations on the land 

 surface, are carried into the lakes by heavy rains. Spring water usu- 

 ally contains salts of calcium, iron and aluminum. When this enters 

 the lake, huminic salts of slight solubility are precipitated, giving the 

 brown layers, the Dy or Dy-jord. As this material goes down, it 

 carries with it algK (diatoms, etc.), fragments of mollusks, water 

 insects and other debris, including excrement of animals. The pas- 

 sage to ordinary peat is gradual. Dy may be forming in the open 

 portion of a lake while successive stages of bog-development are 

 shown on the shores — and it may re-appear within the peat. Over- 

 flow, giving a constant rise of the water-level, may cause destrue- 

 ns H. von Post, in K. Vet. Akad. Handl. (4), 1861, not seen by the writer; 

 " The Formation of Peat-mosses with Especial Reference to the Theories of 

 A. Blytt," Bull. Geol. Inst. Univ. Upsala, Vol. I., 1894, pp. 284-288. 



