I9II.] STEVENSON— FORMATION OF COAL BEDS. 581 



in Thurgau shows algae as the chief constituents, with pollen and 

 chitin remains, all felted and embedded in a gelatin-like mass. These 

 Lebertorfs originated in quiet waters or on damp soil, through con- 

 tinuous deposition of gelatinous algae. 



Lebertorf is the same with Faulschlamm or Sapropel of Potonie,** 

 an accumulation of stagnant water organisms, animals as well as 

 plants, a formation characteristic of pools in swamps. The fresh- 

 water algse multiply with such rapidity that eventually a great mass 

 may be deposited. Potonie says that there are lakes in south Ger- 

 many so filled with Sapropel that they cannot be navigated. Cas- 

 pary, cited by Friih, conceives that there is no peat-filled lake, on 

 whose bottom this material does not exist. He found it about 9 

 meters thick at one locality. Friih has given a synopsis in his later 

 work of studies by the students of northern Europe which show the 

 wide distribution of this material. But Lebertorf or Sapropel, so 

 closely resembling cannel in appearance, is not the mass of peat; it 

 is wholly local, originating in open ponds or lakes. The gelatinous 

 algse are of comparatively rare occurrence in true peat, which owes 

 its origin to plants of wholly different type. 



The substance, known as Dopplerite, was described by Haidinger 

 in 185 1 and was studied in great detail by v. Giimbel in 1858. Its 

 similarity, in some respects, to coal led the latter author to give it 

 the name of Torfpechkohle. It occurs at many localities, so many 

 that it may be regarded as a normal constituent of peat. The first 

 reference to material of this type in America is in a paper by Fair- 

 child,®^ who obtained some from a bog at Scranton, Pennsylvania. 

 It is described as bright, resembling a firm but brittle jelly and as 

 occurring in branching masses through the ripe or older peat. In 

 drying, it shrinks more than the peat and the color changes from 

 yellowish brown to almost black, finally becoming brown. In struc- 

 ture it resembles coal. 



Julien,**' discussing Fairchild's communication, asserted that the 

 physical features of the substance, as described, are those of apo- 



^ H. Potonie, " Die Entstehung," etc., p. 20. 



'"H. L. Fairchild, Trans. N. Y. Acad. ScL. Vol. I., 1881. p. 73. 



"A. A. Julien, Trans. N. Y. Acad. Sci., Vol. I., 1881, pp. 75, 76. 



179 



