VALLEY REGION; CHARACTERS OF THE ROCKS. 157 
Measures is well exposed at many places as at Bangor, 
Blount Springs, and Trussville, where it is very extensively 
quarried for use as a fluxing material in the furnaces, as it 
is in part a very pure limestone, but south of the latitude of 
Birmingham it is very rarely seen, and in its stead we find 
the black shales mentioned. These shales are often inter- 
stratified with dark colored limestones and sometimes with 
tolerably pure limestones, but these are unimportant in 
thickness as compared with the shales and sandstones. 
The greater .part of Shades Valley is based upon these 
sandstones and shales, though the limestone appears in 
several places. 
The sandstone which in North Alabama lies between 
the two beds of Mountain Limestone, has a _ very 
close resemblance in texture and other characters to the 
lowermost rocks of the Coal Measures commonly called the 
Millstone grit, and it makes its appearance in that part of 
the State either as a bench along the sides of the Cumber- 
land Mountain spurs, or else as the capping and protecting 
rock of a detached ridge separated from the Sand Mountain 
(Coal Measures), by a narrow valley of erosion. In the anti- 
clinal valleys further south, this sandstone with the litholo- 
gical characters above named, appears commonly as a 
distinct ridge running parallel to the escarpment of the Coal 
Measures, with a narrow valley of shales between, It ap- 
pears to best advantage on one of the detached ridges above 
spoken of, near Tuscumbia, at the site of the old college 
town of Lagrange, and we have often used the name 
Lagrange Sandstone to designate it; but the name Lagrange 
has been used io denote an entirely different formation 
which has caused us to replace it by the name Ozmoor, 
where the rocks are also well exposed, and where the shales 
are more conspicuous than at Lagrange. 
Coal Measures,—Of these rocks it doesnot seem necessary 
to speak in detail, since Mr. Squire has described the Coal 
Measures of the Cahaba Field, and since the measures of all 
the Alabama fields were probably once continuous, the 
description of the rocks of one will answer for all. 
CRETACEOUS.— In the lower part of the area shown in 
the map our study of the distribution of the rocks of older 
