STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 497 



tendency to separate and eventually that seam appears to be repre- 

 sented by 9 seams in a vertical section of about 400 feet. The same 

 features were observed in other seams, though to less extent. The 

 Heathen Coal, at about 20 feet below the Thick in the Dudley area, 

 is at times 43 feet above the Lower Heathen, though these are 

 united in some districts. The New Mine Coal divides near Bentley 

 into two seams, separated by 33 feet of sandstone and shale ; and the 

 Bottom Coal parting, ordinarily i foot, becomes 50 feet. 



The coal seams show as elsewhere variations in thickness and in 

 quality, but these are most marked where the area is near the 

 original limit of the seam. The coal is bituminous throughout. 

 There is little cannel. 



Much red and mottled clay and clunch is present above and be- 

 low the Thick Coal ; similar rock occurs near Brierley Hill in the 

 lowest portion of the Coal Measures. Crossbedded sandstone is not 

 wanting and there are many beds of ironstone. 



'' Rock faults " and " swells " occur only too frequently. At the 

 Old Baremoor colliery, the measures are regular, but at the New 

 Baremoor, the upper portion of the Thick Coal, 9 feet thick, rests 

 on 42 feet of sandy shale, below which are 44 feet of " rock binds " 

 to the Heathen Coal, which at times is replaced by the rock. The 

 lower part of the Thick Coal fringes out on both sides into the rock 

 mass. This is 282 yards wide and it has been followed northward 

 for 400 yards without reaching the end. The bottom of this rock 

 descends toward the north, cutting the lower bands of the coal and 

 the underlying rocks to the Upper Heathen Coal. Thin wedges of 

 sandstone extend into the coal. " Swells " are risings of the floor, 

 often one or two hundred yards long. Jukes thinks that they may 

 have been merely heaps of sand or mud. An important " swell " in 

 the Baremoor colliery showed that partings in the coal thickened 

 appreciably as they approached the swell, with which they united. 



There is complete conformity throughout the Coal Measures, 

 Ironstone beds in many cases contain numerous marine fossils. 



The North Staffordshire Coalfield, surveyed by Gibson,^^ has the 

 ' sequence complete. The Upper Coal Measures or the Red and Grey 



s^W. Gibson, "The Geology of Coal and Coal-Mining," London, 1908, pp. 

 175-182. 



