VALLEY REGION DETAILS ; SHADES VALLEY. 177 
now lapping up in contact with the roeks of the Coal 
Measures, now trending further out into the valley, leaving 
the upturned edges of the whole series from Knox Dolomite 
up, between. 
West of Bessemer we see a rather eomplicated spot where 
the Red Mountain rocks attain a considerable development, 
which will be understood better by a study of the map than 
by any description in words. 
As may be inferred from the map, the Red Mountain on 
this western side of the valley is rather fragmentary, and of 
little value as compared with the same formation on the 
other side, east of Birmingham. Above Boyle’s Gap it be- 
comes more regular and of greater economic importance. 
It need hardly be repeated that the strata of all the forma- 
tions to the west of this second fault, stand at very high 
angles, often being perpendicular, and at times being pushed 
over past the vertical so as to dip back towards the south- 
east. The millstone grit of the Warrior Field may nearly 
always be seen as a ledge of nearly vertical rocks forming, 
most the whole length of the. valley, a wall, beyond which 
we come in a few hundred yards to almost horizontal 
measures, showing that the disturbance affects to any great 
degree, only the extreme edge of the field. Parallel with 
this rock wall of the Millstone grit, we usually find another 
wall of vertical rocks, with a narrow valley intervening. 
This wall is formed by the Sub-Carboniferous sandstone of 
the Oxmoor series. The line of the fault may easily be 
traced by the ledges of vertical or nearly vertical rocks that 
lie to the northwest of it. Such, then, is the structure of the 
valley in all the upper half of the map, or above the latitude 
of Bessemer. Below that there are some important varia- 
tions which have in part been referred to. 
The variations from the above named structure are to be 
seen in the area through which the McAshan Mountains ex- 
tends. This mountain is a Red Mountain ridge composed 
of the three formations, Clinton, Black Shale, and Sub-Car- 
pboniferous chert, with Trenton limestone on its eastern face. 
Beyond this mountain and across a fault, we find a repeti- 
tion of the same beds, a second Red Mountain, in its normal 
place as ne the Warrior Coal Field. 
