STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 153 



ings have streaks or fragments of lignite; the thick bottom bench is 

 No. 25 of Pengelly's section, 20 feet 11 inches; clays and sands, 

 stems and leaves are abundant in the upper half and thin streaks of 

 lignite were seen in the lower part, 44 feet i inch ; lignite with part- 

 ings, 17 feet of lignite in 9 benches and 3 feet 2 inches of clay in 

 the partings ; the lignite benches are 3 inches to 4 feet thick, 20 feet 

 9 inches. 



Roots descend from the lowest bench of the upper lignite into 

 the underclay and the coal of that bench consists very largely of 

 fronds of great ferns associated with leaves of other plants. The 

 lower bed shows noteworthy variation in its benches. The third, 

 descending, is woody and somewhat charred; the fifth and sixth are 

 very hard and compact, not so tough as some of the others. The 

 bottom bench is divided by a thin parting of " charred lignite " into 

 an upper portion, 9 inches thick, which breaks into " irregular glassy 

 pieces," and a lower portion, 3 feet 3 inches, which is hard light 

 brown, less heavy than the ordinary lignite, is brittle woody and looks 

 like ordinary coal. ]\Iineral charcoal is present in all the benches. 

 Of the about 50 species of plants recognized by Heer, Sequoias are 

 most abundant and they form the greater part of one bed. Cony- 

 beare-^^ has remarked that, in the Bovey Tracey area, one can see 

 " the most decided wood pass into a substance nO' wise differing from 

 common coal in chemical characters." 



The Lower Tertiary coals of the United States of America are 

 of great economic importance. They are of all grades from woody 

 lignite to bituminous, even coking coal, and anthracite ; and all are 

 utilized. The basins and the fragments of basins which have escaped 

 erosion are mostly in areas bordering on the Rocky Mountain region ; 

 but besides these there is a very extensive area in Texas and petty 

 deposits are found in a few other localities west from the Mississippi 

 A'alley. 



The deposits carrying brown coal in Texas have been grouped by 

 Dumble'-^*^ into the Timber Belt, the Yegua and the Fayette, the last 



-15 W. D. Conybeare, "Outlines of Geology of England and Wales," 

 London, 1822, p. 345. 



216 E. T. Dumble, " Report on the Brown Coal and Lignite Deposits of 

 Texas," Austin, 1892, pp. 125, 135, 151, 165. 



