96 STEVENSON— FORMATION OF COAL BEDS. [April 21. 



merely illustrations of the ordinary conditions. " The allochthonous 

 formation of fossil humus beds is not the normal, as Ochsenius 

 maintains, but autochthony is the normal, exactly as in the corre- 

 sponding beds of the present day." But this does not exclude con- 

 tributions from other localities. He cites the abandoned ox-bows 

 of the Mississippi, into which drift wood is thrown at high water, 

 but which are filled eventually with autochonous peat in which the 

 driftwood is enclosed. The existence of Stigniaria in intervening 

 beds is a normal thing and to be expected, as appears from condi- 

 tions in cypress swamps of North America. Its existence in the 

 coal itself is explained by autochthony, for, on that hypothesis, the 

 old decaying vegetation becomes soil for the new. Indeed, the 

 only difference between deposits of the several geological periods 

 is in character of the vegetation, there is none in the mode of 

 accumulation. 



He finds a fossil swamp of the American type in the Miocene 

 deposits of brown coal at Gr. Raschen near Senftenberg, which con- 

 tains, among other plants, Taxodium distich iiiii. The brown coal 

 is 10 meters thick and shows several generations of forests, one 

 above the other, the stumps remaining rooted in the brown coal. 

 Everv feature of recent swamps is reproduced there except that 

 the humus has become brown coal. Many of the stems are hollow, 

 containing more or less of Schweelkohle. It is worthy of note that 

 an old peat bog exists on the clay overlying the brown coal, and that, 

 in the humose sand covering the peat, there are trunks of Piniis 

 silvcstris: the conditions favoring accumulation of humus continued 

 there until diluvial time. The Schweelkohle is due to resinous 

 exudations from broken parts of the tree — the familiar process of 

 closing wounds. 



Absence of stumps in no wise proves allochthonous formation. 

 If the fossil moor had borne only non-resinous dicotyledons, the 

 Gr. Raschen condition could not have come about. The fact that 

 Stigmaricc are often filled with sand is no evidence of allochthony, 

 for hollow alder stumps in West Prussia swamps, exposed to high 

 water, are filled with sand even to the roots, so that they must be 

 cleaned out before the axe is applied. 



96 



