STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 61 



7 inches thick and retains some peat-like features, but is a passage 

 from the hgnite of the border to the peat of the open valley, which 

 has been growing continuously, so that it is now 8 feet thick. In 

 another connection, he remarks that some deposits of lignite are 

 surrounded by peat. Goeppert's^^ observation is very similar. A 

 deposit of peat was found in the low part of a valley near Helvetihof 

 in Upper Silesia. On both sides of the valley, a portion of the 

 deposit is covered with 2 to lo feet of soil and sand beds, under 

 which the peat has been changed into a distinctly laminated, hard 

 black mass, almost like stone coal ; whereas the peat in the open 

 valley, uncompressed, has the usual brown color and comparatively 

 loose structure. 



Preservation of Peat Deposits. — The surface of a dead bog is 

 often irregular as though it were wasting away ; the peat-cover of a 

 drained area, under cultivation, disappears within a few years as 

 ploughing exposes more and more of it to oxidation, drying and 

 the winds. A casual observer of the "hag" region of Scotland 

 feels justified in believing that peat is formed only to decay and that 

 little of it will survive to reach a more advanced stage of trans- 

 formation. This is the conclusion reached by an eminent student of 

 coal problems and his opinion appears to have been accepted as fact 

 by several authors. But the conclusion cannot be accepted as final ; 

 it seems to be based on incomplete observation or on lack of 

 familiarity with conditions in great areas. The process of removal, 

 where man does not interfere, is slow, because peat, with its felted 

 structure and its obstinate retention of water, offers great resistance 

 to erosion. A very thin cover of fresh peat protects itself and the 

 underlying rock from removal. The effect of oxidation is not 

 rapid, as it is necessarily superficial, circulation of air in the drying 

 peat being confined to the newer portion. 



Lowering of the water-level does not mean that the surface is 



to become dry and pulverulent, to be swept away by the wind. In 



most cases, that lowering of the level leads to invasion by plants 



which cannot endure wet conditions, to the growth of a rather dense 



cover of vegetation which, by its accumulating offal, protects the 



'^ H. B. Goeppert, " Abhandlung eingesandt als Antwort auf die preis- 

 frage," etc., Amsterdam, 1848, pp. 104, 105. 



