152 Q. W. Buhnan — Drift Coal in Sandstone. 



down by the next. But, admitting the drift origin of these inter- 

 calations, it follows that the " Thick coal " itself, of which seam they 

 are portions, must be attributed to a similar origin. 



Coal-seams may also be broken up by intercalated bands of sand- 

 stone, as in the following section of the " Kailblades " Coal of the 

 Midlothian Coal-field : 



Feet. Inches. 



Sandstone and Shale ... 10 8 



Coal 1 6 



Sandstone 2 11 



Coal 1 1 



Sandstone and Shale 3 2 



Coal 1 10 



Sandstone and Shale 78 1 



(Memoirs Geological Survey, Geology of the Neighbourhood of 

 Edinburgh, p. 97.) 



Similarly thin seams of coal may occur in beds of sandstone, as in 

 the following section on page 100 of the same Memoir : 



Feet. Inches. 



Grey Sandstone ,., ... 62 



Coal 3 



Sandstone ... ... ... 3 



There are, moreover, certain areas of coal — usually of limited 

 extent — which are attributed to drift vegetation by advocates of its 

 terrestrial origin in general. Thus Prof. Green attributes the origin 

 of cannel coal to the accumulation of drift vegetation in ponds or 

 lakes : — 



" The presence of fossil fish in cannels shows that they must 

 have been formed under water, and they probably consist of vege- 

 table matter which has drifted down into ponds or lakes and lay 

 soaking till it became reduced to pulp " (Coal, by Professors Green 

 and Miall, etc., p. 31). 



And if it be admitted that the sand, mud, and vegetable matter 

 drifted down by streams into the pond or lake were sorted so as to 

 produce beds of more or less pure coal, is it not necessary also 

 to admit that a similar sorting, on a much larger scale, would take 

 place with the vegetation and other debris carried down to the sea ? 



Thus we are led to admit the possibility of more extensive beds 

 of coal being formed of drift vegetation. Nor is it necessary to 

 assume that such drift coal will necessarily be cannel. For the 

 obviously drift coal we have been considering is not cannel, but 

 ordinary bituminous coal, with the usual cleavage. 



If, then, cannel coal — as seems probable — was formed by drift 

 vegetation, and ordinary bituminous coal in sandstone has a similar 

 origin, there seems no reason why areas of the latter as extensive 

 as those of the former, or even more so, should not occur. Such a 

 conclusion, however, leaves unexplained the differences between 

 cannel coal and the ordinary bituminous coal found in sandstone. 



Other considerations point to the conclusion that in cei'tain cases 

 ordinary bituminous and cannel coal have been formed under the 

 same conditions as to place. 



In the Northumberland Coal-field, for example, no distinct and 



