29 
GENERAL GEOLOGY OF STEUBENVILLE QUADRANGLE. 
I 1 iom the south end of this anticline a structural nose puts off toward 
Paiis, 1 a., whence it extends southward along the Pennsylvania- 
T\ est T irginia line, ending south of Colliers Station in a terrace 
which has been called the Collier terrace. 
hiom the southwest end of the New Cumberland anticline another 
nose passes through a very low saddle and connects with the main 
anticline of the ( adiz quadrangle, two miles Avest of the A 7 illage of 
TV intersville the beds are nearly level and form what is called the 
Wintersville terrace. 
The main syncline of the area, known as the Mingo syncline, enters 
the quadrangle near the southeast corner and extends northwestward 
to the town of Mingo Junction, A\ T here it swings to the north toward 
Hollidays C ove. I he trough rises rapidly after passing the mouth 
of McMahan Run and soon attains the general level of the adjacent 
structure. 
In the northwest corner of the quadrangle is the end of a synclinal 
basin which extends into the quadrangle from the north. This is 
called the Somerset syncline, after the Aullage of NeAv Somerset, in 
the TV ellsville quadrangle. Besides these main features there are a 
number of local basins and some anticline noses or terraces which are 
not of enough importance to deserve distinctive names. 
GEOLOGIC FEATURES BELOW THE SURFACE. 
SOURCE OF INFORMATION. 
A knowledge of conditions below the surface is obtained from the 
logs of shafts and \A 7 ells. Some logs are recorded in great detail, but 
in most of them only the strata that are of importance to those who 
are drilling are noted. The sandstones are the formations that in¬ 
terest the oil and gas drillers, but if the} 7 have not previously pro¬ 
duced either oil or gas their positions are noted only by “ string 
measurement.” In this method a string is tied around the main 
cable which holds the drilling tools at the top of the bull Avheel. 
The distance OA 7 er the crown pulley to the mouth of the Avell on the 
derrick floor is measured, or assumed to be 160 feet. When the string 
has gone over the crown pulley and entered the hole, a second string 
is attached at the bull wheel. When the driller desires to know the 
dejDtli of a particular bed of rock in which the drill is working, he 
multiplies 160 feet (or the measured distance) by the number of 
times strings have entered the hole and to this product adds the dis¬ 
tance which the last string has moved up the derrick. 
When a sandstone is reached in which oil or gas is expected to 
occur, its position below the mouth of the well is carefully measured 
by a steel tape. If the string and tape measurement were both 
