STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 167 



occurrence within considerable spaces, but they change so abruptly 

 in thickness, structure and composition that correlation in the dif- 

 ferent areas is impossible; the associated rocks are equally variable. 

 The floor is usually clay or shale, often carbonaceous, but occasion- 

 ally it is sandstone. Some parts of the county lost much coal during 

 formation of pre-glacial valleys, now filled with glacial drift; while 

 several coal beds suffered much from contemporaneous erosion and 

 were replaced in considerable areas with sandstone. Evans notes 

 tree trunks extending from the coal into the roof. D. White,^^^ 

 when at Rentoul in 1908, saw " kettle bottoms," or erect stumps of 

 trees, 6 to 18 inches in diameter, standing directly on the coal, with 

 black shale and coal filling the casts of the decayed boles. The coal 

 is distinctly xyloid and jetified wood is strongly in evidence. Evans 

 found a silicified erect stump showing the annual rings. Thiessen-^^ 

 ascertained that the coal collected by D. White contains a great pro- 

 portion of debris, the quantity being almost equal to that of the 

 woody matter. The woody component is coniferous and resinous ; 

 the debris is very resinous, apparently almost one half of its mass 

 consisting of such material. Exines of spores and pollen are rather 

 abundant but cuticles are rare. 



The province of British Columbia, Canada, adjoining the state of 

 Washington at the north, has a number of isolated coal basins, 

 mostly of small extent. The available knowledge respecting the 

 region has been digested by Bowling,-^' from whose work this syn- 

 opsis is taken. It seems probable that the deposits are of Oligocene 

 age in many of the places where the coal is economically important. 

 In the Tulameen district, according to C. Camsell, the coal-bearing 

 rocks occupy a basin in the older rocks, with an area of about 5 

 square miles. The section measured is about 2,500 feet and the 

 middle portion, 460 feet, carrying the coal beds, begins at 600 feet 

 from the bottom. Four beds with, in all, 20 feet of coal have been 

 discovered and prospected. The coal throughout is in alternate 

 bright and dull bands, the latter predominating; but the dull bands 



231 D. White, " Origin of Coal," p. 24. 



232 R_ Thiessen, " Microscopic Study of Coal," p. 243. 



233 D. B. Dowling, " Coal Fields of British Columbia," Geol. Surv. of 

 Canada, Mem. 69, 1915, pp. 263 ff., 289 ff., 298 ff., 309, 321. 



