414 
very folliliferous, showing that life was abundant when it was laid down. 
The area of outcrop is narrow and intermingles with the western edge of 
the Knobstone, often capping outliers of the latter. It has no distinct 
topography outside of the fact that sinks occur in it, which never occur in 
the Knobstone, and rarely in the formation above it. 
Salem Limestone. Superior to the Harrodsburg formation is the 
famous Salem limestone known as the Odlitic, or Bedford limestone. It is 
an excellent building stone, and is known as such all over the United 
States. Typical outcrops of it occur along the valley of Jacks Defeat. 
The stone is usually massive, with few indications of bedding, varying 
from a few feet up to eighty and ninety feet in extreme cases. The stone 
typically is a porous stone composed of nearly pure calcium carbonate. It 
is made up principally of broken animal remains and several species of 
Protozoa, among which the main one is Endothyra baileyi. These have all 
heen cemented together in a loose manner. The area of its outcrop is 
characterized by long, gentle slopes, rounded hills and general undulating 
topography. 
Mitchell Limestone. The Mitchell limestone is the one that we are 
mostly concerned with, since practically the entire basin of the Flatwoods 
region is in this stone. It ranges in thickness from a few feet in its north- 
ern outcrop to 250 feet in the southern part of the State. The stratigraphy 
of this formation is rather varied, as there are rarely two successive 
layers alike. In general it consists of impure limestones and calcareous 
shales, usually thin. Many layers are very hard, aud weather white, 
sometimes small slabs haying the appearance of bleached bone, and on 
being struck have a metallic ring. Such layers usually have numerous 
right-angled joint cracks, and are semi-lithographic, breaking wth a sub- 
coneoidal fractiure. The upper members of this formation are usually a 
beautiful oblitic structure. Ag a rule the limestone is fessiliferous. The 
area of the outcrop of the Mitchell limestone extends over a broad plain 
which narrows to the north and pinches out in Montgomery County. It is 
essentially a cave-bearing formation, containing some of the most famous 
caves in the world. Wyandotte and Marengo caves of Crawford County 
and Mammoth cave of Kentucky are in this stone. The region of its out- 
crop is pitted with sinks, and underground drainage is a distinct and 
noticeable feature. Lost River of Orange County is a typical example of 
an underground stream in the Mitchell area. Hundreds of sinks occur on 
the borders of the Flatwoods region, where the filled material is relatively 
