STATE _GEOLOGIST. 29. 
of the Conglomerate Coal-measures, and its position with reference to the 
Cambridge lime and Dunkard sand strongly indicates that it is the Tion- 
esta sandstone. . 
The Second Cow Run and the Macksburg 500-foot sand have been 
regarded by many as equivalent. As has already been suggested by Pro- 
fessor White, however, this cannot be the case.t. Examination of the 
record of the Rice well shows that the interval between the First Cow 
Run and 500-foot sands is only 307 feet, while, as already stated, the 
interval should be 400 feet. Measuring from the Meigs Creek coal, equally 
conclusive figures are secured. Thus the Second Cow Run sand lies 840 
feet below the Meigs Creek coal, while the interval between this seam 
and the 500-foot sand is only 670 feet. The sand at Macksburg known as 
the 800-foot is probably the equivalent of the Second Cow Run. 
The First Cow Run Sand.—This is the most important and_best- 
known sand of the group. As is shown in the record of the Dunn well, 
its position is 100 feet below:the Ames limestone. In western Morgan 
county, near the outcrop of the sand, the interval ranges from. 70 feet to 
100. The Ames limestone there lies 170 feet below the Pittsburg coal. 
The identification of the sand is made more certain by the fact that the 
Cambridge limestone lies immediately below or is separated from the sand 
by a thin bed of shales. Unfortunately these limestones are not recognized 
in Monroe and the eastern part of Washington counties, hence the sand in 
question often cannot be identified there with certainty. In such localities ° 
any shallow sand, especially if it makes a show of oil or gas, is known 
as the Cow Run. The relation of the sand to the two limestones places it 
about 100 feet above the base of the Conemaugh formation. 
If the Berea grit be taken as the type of a persistent stratum of sand- 
stone, the First Cow Run sand may properly be selected as the representa- 
tive of the opposite type. It is the most patchy of the oil or gas rocks of 
Ohio. The maximum thickness of the formation may be taken at 50 feet, 
but even a short distance from this the stratum may become very thin or 
actually disappear entirely. The texture varies much, and where pro- 
ductive is sometimes conglomeritic. Pebbles three-fourths of an inch in 
diameter have been found, and those one-fourth of an inch are common. 
The pebbles consist of quartz, but small grains of other minerals are found. 
From this type the formation changes to a hard compact sandstone. 
The sand is an important source of oil in Morgan and Washington 
counties. It seems to have been first struck at Macksburg in 1860, where 
it is known as the 140-foot sand; this being the depth at which the sand 
was found in the valley at that place. In 1861 the sand was found at 
Cow Run and has there been a producer ever since. It is seen that the 
latter name has not the claim of priority, but it is so much more widely 
used that it is here retained. 
1West Virginia Geol. Sur. Vol. I, p. 299. 
