STRATIGRAPHICAL ORDER. 47 
appears in all of our later sections as the Darlington or Middle Kittan- 
ning coal. The Lower Kittanning coal (Leetonia seam) is seldom 
missed from the sections, but its thickness generally falls below 3 feet 
throughout the Little Beaver valley. These two coals, the Lower and 
Middle Kittanning, hold, in the Ohio valley, about the same relations 
to each other that the Upper Clarion and Lower Kittanning hold at 
New Lisbon. The numbers by which these two coals are designated at 
New Lisbon, 3 and 4, have accordingly been shifted to the Lower and 
Middle Kittanning in the Ohio valley. The first of these numbers, 3, 
has been raised from the Lower Mercer horizon to the Lower Kittan- 
ning coal, resting temporarily at Leetonia on the Upper Clarion. The 
second number, 4, has been made to do more varied service. Origin- 
ally fixed upon the upper limestone coal (Gray or Putnam Hill), we 
find it next assigned to the Canfield Cannel (Upper Clarion, which has 
no regular number in the Ohio classification). When this seam emer- 
ges from the Canfield dividing ridge as it is followed southward, its old 
number, 4, is given to the Lower Kittanning that now comes into the 
section, and it is for a time known as No. 3. A similar slipping up- 
ward of the numbers takes place once more in the valley of the Little 
Beaver, as has been already shown where the Lower Kittanning be- 
comes coal No. 3 and the Middle Kittanning becomes No. 4. 
Coming down the Ohio Valley from the mouth of the Little 
Beaver, we hold the section found there unbroken and unchanged to 
the mouth of Yellow Creek and beyond. That the “ Clay Vein coal” 
or “Sulphur Vein” of Smith’s Ferry and above, is the “Clay Vein,” 
“ Potters’ Vein” and “Sulphur Vein” of East Liverpool and Wells- 
ville, and the ‘Creek Vein” and “ Potters’ Vein” of Yellow Creek 
and Linton, is called in question by no one. The openings to the clay- 
bed are so closely connected, and in some parts of the field so nearly 
continuous, and the entire section of the elements involved is so thor- 
oughly characteristic, that though the levels of the beds are sometimes 
changed by the low anticlinal axes or folds that pass through this por- 
tion of the State, the identity of the beds is never shaken nor invali- 
dated. That the Clay Vein coal of Smith’s Ferry is the Lower Kit- 
tanning coal of Western Pennsylvania is as well settled as any fact in 
the geology of the Upper Ohio Valley. The extension of the Pitts- 
burgh coal into Ohio is in no wise more certainly determined than that 
of the Lower Kittanning coal. The identity of the “ Creek Vein” or 
