STATE GEOLOGIST. 137 
The depth of the wells, of course, varies with the surface altitude; but 
few, if any, exceed 700 feet. One on the Hoon farm, at the end of the 
bridge at Brown’s Mills, struck the oil sand at 393 feet. 
The Oil Sand.—This, as has already been stated, is the First Cow Run. 
Its position below the Ames limestone varies considerably. An examina- 
tion of 11 well records taken at random on the Dale farm showed a max- 
imum and minimum distance of 92 and 71 feet, with an average of 82 
feet ; and the latter figure may be taken as an average for all the territory 
where the sand in question is found. It is rare that the interval exceeds 
100 feet, or is less than 65 feet. | 
The sand varies much in texture. Sometimes it is so coarse as to 
make a conglomerate. Pebbles having a diameter of three-fourths of an 
inch are occasionally found, while those one-fourth of an inch are com- 
mon. From these extremes the rock grows finer until it becomes so 
compact that it cannot contain oil or gas in commercial quantities. Some- 
times the higher portion of the sand is quite fine or compact, and then is 
known as the “cap rock” among the drillers; while at other places the up- 
per part is quite porous and contains important quantities of oil or gas. 
The sand is composed almost wholly of light-colored quartz, but other 
minerals, such as pyrite and mica are not uncommon. It is nearly colorless 
when first brought to the surface, but frequently changes to a yellow-brown 
when exposed to the atmosphere. 
The pay streak, like the sand as a whole, varies much. It is usually 
the coarser part, and has a darker color. The drillers frequently describe 
it as having the shade of brown sugar. In thickness it commonly varies 
from 8 to 15 feet, but smaller and greater measurements are not rare. It 
is usually quite soft, so that the drill passes through it very quickly. Gen- 
erally the pay lies a few feet below the top of the sand, but sometimes it is 
found at the summit. Occasionally also it lies at the bottom. Rarely the 
driller reports the pay rock divided by a few feet of shale, and then he 
announces the presence of two pays. An illustration of this is found on 
the Mozier farm, near Chester Hill, where the upper pay, having a thick- 
ness of ten feet, is separated from the lower one, having the same thick- 
ness, by ten feet of shale. Four wells similar to this have been found on 
the Dale farm. | 
In total thickness the sand varies greatly. Thus on the Dale farm 
14 well records, taken at random, disclosed thicknesses ranging from 4 
to 30 feet, with an average of 15. The rapidity of change is well shown 
on this farm by two wells 125 feet apart. One has 7 feet of the sand and 
the other 30 feet. The greatest thickness yet reported is in well No. 17, 
on the Mozier farm, where 47 feet of sand were found. It is not uncom- 
mon to find thicknesses of a foot or less, but such commonly occur along 
the margin of the field, and are rarely productive. 
