320 ANNUAL REPORT 
This is readily seen by examining a geological map. The arch con- 
tains minor irregularities, such as the well known Findlay break described 
by Orton and mentioned in the discussion of Hancock and Wood counties 
in the earlier parts of this volume. It was on or near this break that many 
of the largest gas wells were found, and in general it may be stated that 
the richest oil territory has been found where the Trenton rock lies highest. 
In the southwestern part of the Trenton field, in Mercer, Auglaize 
and Shelby counties the rock in question rises to the south and is exposed 
in the bed of the Ohio river at Cincinnati. This seems to exclude the idea 
of an arch in that part of the field. From Mercer county north the dip in 
the Trenton rock is small, the structure being more of a terrace than an 
anticline. 
It cannot be said that all oil or gas fields in Ohio are associated with 
anticlines or terraces. Thus the great gas field at Sugar Grove, the oil 
fields at Chester Hill, Corning, Scio and several smaller reservoirs have 
not as yet been demonstrated to lie on these structures. However, the 
reverse has not been conclusively demonstrated, and the fields in question 
may still fall in with the anticline or terrace theory. The great reservoir 
at Beaumont, Texas, also appears to stand in opposition to this theory. 
