STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 171 



lier-^*' at numerous localities farther down the Yukon, show the same 

 general features as those already referred to. 



IMartin and Katz-^' found in the Matanuska region beds of dark 

 fissile shale with bands of ironstone. The coal beds, in some cases, 

 are thick and commercially good, but in others they consist merely 

 of thin alternating layers of coal and shale, so that, though the coal 

 predominates, the thick mass is worthless. The upper half of the 

 section, about i,ooo feet, is composed chiefly of dark shales with 

 thin beds of sandstone and many thicker beds of carbonaceous shale, 

 which are leaf-bearing and include petty lenses of coal. The authors 

 saw several fossil logs and tree stumps in an exposure, where one 

 of them is 20 feet long and vertical to the bedding. Petrified frag- 

 ments of wood appear to be not rare. 



Henshaw-^^ has given a brief note respecting the great bed on 

 Chicago Creek, in Seward Peninsula and almost directly under the 

 Arctic circle. The dip is 18 to 36 degrees and the thickness is 88 

 feet. The coal is frozen as in Spitzbergen and the modest mining 

 operations are prosecuted during the short summer. The tunnel had 

 been cleaned out only a short time before Henshaw's visit and he 

 w^as able to make examination of the whole bed. It is an almost 

 continuous mass of coal, broken only by a few layers of bony coal 

 and sandy shale. Atwood-^^ notes that in the Cook Inlet area, the 

 coal beds are many, varying from mere films to 20 feet. At a mine 

 near Tyonek, the coal is a tough, woody lignite and contains large 

 trunks of trees, which are only partly converted. The mode of their 

 occurrence suggests to him that they may be logs drifted into a pond 

 or swamp, or that they are a group of fallen forest trees. 



Tertiary coals have been observed at many localities in Siberia, 

 but available notes respecting them are few and the age of the coals 

 seems to be somewhat uncertain. The summary description of 



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

 Survey, Bull. 218, 1903, pp. 17, 19, 22-26, 30-39. 



237 G. C. Martin and F. J. Katz, " Lower Matanuska Valley," U. S. Geol. 

 Survey, Bull. 500, 1912, pp. 44-48. 



238 p_ p_ Henshaw, " Mining in the Fairhaven Precinct," U. S. Geol. 

 Survey, Bull. 379, 1909, pp. 362. 



239 -vv^ \\/-_ Atwood, " Mineral Resources of Southwestern Alaska," the 

 same, p. 117. 



