24 GEOLOGICAL SURVEY OF ALABAMA. 
prominent ridge known in the south end of the basin as 
Pine Ridge, or Flat Ridge, and in the north end of the basin, 
as Black-jack Ridge ; this ridge is formed mostly of heavy 
beds of the white Millstone Grit Sandstone, overlying the 
gritty slates and forming a shield, protecting the slates from 
the action of denuding forces. This sandstone is composed 
of the same material as the white sandstone in Shades 
Mountain or Rocky Ridge. After passing over this and ar- 
riving at the foot of Flat Ridge or Black-jack Ridge on its 
southeast side, you wil! cross the outcrop of a thic seam, 
generally of about six inches in thickness. You are now at 
the base of the immense gritty slate formation surrounding 
the Gould seam. Before arriving at the Gould seam you 
will notice a pink sandstone which is the bottom rock of 
the under-seam, ten feet below the Gould. Passing over the 
Gould seam you will find a yellow and pink sandstone, the 
roof of said seam, and overlying this an immense layer of 
gritty slate. Ascending the next prominent ridge, which in 
this basin is mostly designated as Grassy Ridge, (in other 
parts of the Coal Field it is known as Chestnut Ridge, Red 
Ridge, &c.,) you now find the thick beds of gritty slate 
changing their color and texture to layers of sandstone, 
then gritty slate, and further up the ridge you find a twenty 
or thirty foot layer of bluish black slate. On attaining the 
summit of Grassy Ridge, you find the upper layers of the 
white Millstone Grit Sandstone; this forms the shield to 
Grassy Ridge against denuding action on the underlying 
slates. This upper layer is one of our most prominent 
landmarks in geological examinations in this part of the 
coal measures of Alabama. Descending fhe gentle slope of 
Grassy Ridge to its foot on the southeastern side, you next 
pass over a number of beds of sandstone and gritty slates 
and arrive at the Nunnally seam, with a sandstone roof; 
this seam contains about two and a half feet of coal. 
Thence, in the direction of the dip, passing over various 
layers of sandstone, slaty sandstone and gritty slates, you 
arrive at the Harkness Double, or Poole seam. 
(For section of Poole seam, see below.) 
Continuing on in the same direction, you arrive at a 
large, hundred feet thick layer of blue sandstone, that is 
