124 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



sociated with other types and not rarely one finds laminae of Glanz- 

 alternating with those of dull coal, giving a banded appearance to 

 the section. This is the hardest variety of brown coal and is de- 

 rived prevailingly from resinous woods. (9) Gayet or jet, dense, 

 hard but not brittle, richly bituminous. 



Von GumbeP°* was satisfied with a much simpler classification. 

 His subdivisions are Lignit, Pechkohle, typical Braunkohle, which 

 includes all the other varieties of authors. He adds Faserkohle, 

 the same with mineral charcoal or fusain. 



Toula's^"^ system is as simple as that of v. Giimbel, but quite 

 different in the method of grouping. Glanz- and Pechkohle are 

 varieties of the black coals ; Moorkohle in many ways resembles 

 peat ; Blatterkohle or Dysodil and Lignit are defined by him as by 

 other writers. All are allied closely to types of materials observed 

 in peat deposits. 



The array of terms is formidable, but the condition is less com- 

 plex than it appears. A bed never consists wholly of any one type; 

 ordinarily several kinds of coal are found in a single bed, where 

 those most in contrast are often found in intimate association. 

 The great variety shows sufficiently well that the term brown coal 

 or lignite is applied to a group of substances differing in mode of 

 occurrence as well as in chemical and physical character, among 

 them some closely allied to peat and others which bear great re- 

 semblance to the Palaeozoic coals. Owing to the great diversity 

 in conditions, it is necessary to present descriptions of deposits in 

 the order of their age and in some detail, reserving until the close 

 an effort to determine the features which are in common. 



The Pliocene Coals. — Descriptive notes respecting the Pliocene 

 coals are comparatively few. Some of the deposits are on the bor- 

 der line between Tertiary and Quaternary, so that the age is in- 

 determinate. Collier^^*' discovered an area of this kind near the 

 palisades of the Yukon River in Alaska. Bluffs of silt and gravel, 

 150 feet high, line the river and contain so many bones of large 



164 C. W. V. Giimbel, " Beitrage," etc., pp. 139 ff. 



165 F. Toula, " Die Steinkohlen," Wien, 1888, p. 18. 



166 A. J. Collier, " The Coal Resources of the Yukon, Alaska," U. S. Geol. 

 Survey, Bull. 218, 1903, pp. 43, 44. 



