STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 505 



of trees, still standing erect in the position in which they grew, and 

 attached to their roots, rise out of an underclay." At times, the 

 underclay underlies carbonaceous shale. Canister is a very hard 

 silicious earth, which is seat to numerous coals, especially in the 

 Lower Coal Measures."^ 



Creen mentions (p. 123) that an erect stem was seen rooted in 

 a thin seam of coal and passing up into sandstone. Sorby^^- gave a 

 brief note respecting erect stems, which he saw at Wadsley. In 

 preparing the surface for a public building, the workmen exposed 

 a considerable number of such stems. Sorby induced the authori- 

 ties to construct sheds in order to preserve the finer specimens. 

 The trees appeared to have grown in what is now a clay-like shale, 

 then died and become decomposed to the top of the surrounding 

 mud. They were hollow stumps and were filled with sand like that 

 of the overlying sandstone. The stems are Sigillaria and the roots 

 are Stigmaria. The largest and best specimen has diameter of 5 

 feet 2 inches and the top is not ragged. The roots, which bifurcate, 

 are shown well to a distance of 6 feet from the stump. A prostrate 

 stem lay alongside. Five stumps were exposed in a space of 40 or 

 50 yards. 



In the Northern field, within Durham and Northumberland, coal 

 seams make their appearance in the Lower Carboniferous and attain 

 some economic importance. These become valuable in portions of 

 Scotland, where they are the source of fuel supply for leading in- 

 dustries. It is unnecessary to dwell on the several fields, as, for 

 the most part, the general conditions differ in the Coal Measures 

 very little from those observed in England. It will suffice to make 

 reference to but one field in Scotland, 



The coalfield of the Lothians is in Edinburghshire and Linlith- 

 gowshire. It was studied long ago by Howell, Geikie and Young 

 but more recently was examined in detail by Cadell.^^^ The suc- 



"1 Green and Russell, pp. 14, 17, 37, 58, 60, 97, 114, 140, 300, 323, 402, 

 437, 470, 496, 649, 666. 



112 H. C. Sorby, " On the Remains of a Fossil Forest in the Coal Meas- 

 ures at Wadsley, near Sheffield," Quart. Jour. Gcol. Soc, Vol. 31, 1875, p. 458. 



113 H. M. Cadell, " The Geology of the Oil Shalefield of the Lothians," 

 Trans. Edin. Geol. Soc, Vol. VIII., 1901, pp. 116 et seq. ; Mem. Geol. Survey, 

 1906, 1910; "The Story of the Forth," Glasgow, 1913. 



