176 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



Schwelkohle was formerly cast aside as worthless, but it has 

 been utilized in the paraffin industry during later years as the supply 

 of pyropissite is practically exhausted. As shown by Raefler the coal 

 is richest in pyropissite on the borders of several petty basins, the 

 proportion decreasing toward the middle. In the larger basin near 

 Zeitz in Sachsen, the proportion of pyropissite becomes negligible as 

 one goes eastward, but it increases again farther east, beyond the 

 central line of the basin. The origin of the material is obscure. 

 Potonie, in describing the Senftenberg coal, says that many of the 

 stumps, Taxodiiim disfichuni, are hollow and those at the bottom con- 

 tain Schwelkohle in the cavity. But the Schwelkohle in hollow 

 stumps is not confined to the bottom of the deposit though it is more 

 abundant there. He thinks that this substance was produced by flow 

 of resin, which must have been great in the wounded trees ; but one 

 has difficulty in conceiving how a stump, which had been dead long 

 enough to become hollow, could still retain enough vitality to pour 

 out a great quantity of resin for healing of its wounds. Whether or 

 not it is a resin may be open to discussion. The microscopic study 

 of the Weissenfels pyropissite by v. Giimbel led to no definite results 

 but in the Sauforst material he found a great quantity of exines of 

 pollen. The mode of its occurrence seems to suggest that it is not 

 unrelated to the Lebertorfs in origin. Potonie regards it as resinous 

 and its occurrence as layers or smuts in what he recognizes aS 

 autochthonous coal is explained by the suggestion, that these may 

 mark dry places, where the exposed coal was removed by decompo- 

 sition and the resin was left unmingled with foreign matter. 



It appears wholly probable that pyropissite was an original con- 

 stituent, not a product of chemical action during conversion of the 

 vegetable material. Kraemer and Spilker thought it formed by green 

 algae while Witt believed that it was derived from spores. Graefe, 

 considering the contrast between pyropissite and the undoubted resin, 

 retinite, cannot regard a resin as the source of pyropissite, and 

 concludes that wax-like secretions of plants were in chief part the 

 original material. Treated with benzol, pyropissite yielded 69.5 per 

 cent, of "bitumen," while good Schwelkohle yielded 27.3 per cent. — 

 the calculation in each case being for the dry substance. Raefler 



