174 University Geological Survey of Kansas. 
to find such an arch with its axis of direction paralleling the 
sand-beds. Quite as often they cut them transversely and at 
various angles. Here, again, we may learn a lesson from the 
Appalachian fields. It is well established by geologists that, at 
the time the productive sand-beds were accumulating, a long, 
slender arm of the ocean occupied the position now held by the 
Appalachian mountains, an ocean arm forming an inland sea 
very similar in character to the Red Sea, or to the Gulf of Cali- 
fornia. Naturally, therefore, the sand-beds or sand-beaches 
were long and slender, paralleling the arm of the ocean. Later, 
when the mountains were elevated, folds and flexures were 
produced which, by strange coincidence, almost exactly paral- 
leled the ancient coast line of this inland ocean. If, therefore, 
a geological section is drawn parallel to the mountain ranges, 
it shows but little variation and the given sandrock is approxi- 
mately at a constant depth beneath the surface. If such a sec- 
tion is drawn transverse to the mountain range, however, then 
the anticlinal arches and the synclinal troughs become ap- 
parent. It is along these great anticlinal regions that the won- 
derful gas-wells of West Virginia and Pennsylvania are found. 
STRUCTURE IN THE MIDCONTINENTAL OIL-FIELDS. 
Out in the Midcontinental field we have a set of conditions 
slightly different from those of other fields, although, after all, 
they are strongly similar. From good geological evidence it 
may be stated that the old ocean beach had a trend approxi- 
mately north and south, bearing a little to the northeast and 
southwest through the eastern part of Kansas and gradually 
veering eastward in Oklahoma south of Tulsa. The dip here 
in Kansas is due to influences which produced the Ozark hills 
in southwest Missouri. In the vicinity of Kansas City, Ottawa, 
Paola, Garnett, etc., the rocks dip gently to the northwest. 
_ Along the southern line of Kansas the maximum dip is approxi- 
mately west, possibly veering a little southwest. Farther 
south, in Oklahoma, the southwestern dip becomes more ap- 
parent. The same formations swing around to the east in the 
vicinity of Fort Smith, where a new set of earth movements 
have produced effects and the dip of the rock is more often in 
a north and south direction. 
In general, we may look for gentle anticlinal arches trend- 
ing northeast and southwest in Kansas. They are so mild that 
they can scarcely be found. In fact, erosion has done its work 
so well that in many cases the eastern sides of such anticlinal 
