19". J STEVEXSOX— FORMATION OF COAL BEDS. 623 



boughs and stems were found, mostly conifers, birches, willows and 

 alders, which in some cases resemble brown coal, in others, pitch 

 coal. The peat-like character of the whole mass, as described by 

 V. Giimbel, recalls the buried bogs of Ohio and Indiana. Treated 

 with caustic potash, the looser portions become a soft, dense felted 

 mass, in which the microscope detects as prevailing constituents, 

 leaves of grasses with mosses. Sphagnum is the prevailing form. 

 Fragments of wood are comparatively rare, though needles and 

 twigs of conifers are not wanting. The denser portions need appli- 

 cation of Schultze's test, a mixture of potassium chlorate and strong 

 nitric acid, which must be allowed to act for a considerable time in 

 order to separate the plant remains. These are the same as in the 

 looser portions. But in addition are splinters of a deep brown 

 structureless material, behaving as dopplerite. It fills cell-spaces in 

 many plant-fragments; this textureless material is the Carbohumin. 

 The numerous cones embedded in the mass are not deformed. 



In passing from the Quaternary to the Tertiary, one finds in- 

 creased difficulty in recognizing peat bogs ; the conditions, observed 

 in the older portions of recent bogs and in those of the Quaternary, 

 are intensified by compression and by removal of the water, which 

 kept in soluble condition the ulmic and humic constituents, while 

 advancing chemical change has converted the whole mass into the 

 mature condition. In fine, the amorphous plastic peat has become 

 amorphous brown coal and only trunks of resistant wood remain to 

 tell the story. Yet in some cases the resemblance is so great that 

 little room remains for doubt. A typical instance is the great 

 Senftenberg Miocene deposit, described by Potonie, to which refer- 

 ence will be made again on a succeeding page. To one familiar with 

 the cypress swamps of the United States, there can be no question 

 respecting the origin of that deposit. Aside from loss in plasticity 

 of the peat, and its conversion into brown coal, the description given 

 by Potonie would apply equally well to the white cedar swamps of 

 New Jersey or to some of the Taxodiuin swamps of the Mississippi, 

 where the peat is equally pure, the mud and silt having been strained 

 out as the water passed through cane brakes. 



Heer, in his " Primeval World of Switzerland," says that at 



221 



