Imllana Natural Gas Field. — Leverett. 17 
out-crop we have 205 feet A. T., as the altitude of the Trenton 
at the Manteno ridge. 
The eastern-most out-crop of the Trenton in northern Illinois 
is the one four miles northeast of Morris, in Grundy county. 
The crest of the anticlinal is probably denoted by this outcrop 
at an altitude about 550 feet A. T. A few miles west from this 
point is the southern end of a more prominent axis of upheav- 
al. This and similar axes in Illinois are discussed by Prof. 
Worthen. ' Concerning the one referred to this statement is 
made : "It enters the state in Stephenson county, intersects 
Rock river at Grand de Tour and the Illinois at Split Rock be- 
tween LaSalle and Utica, bringing the St. Peter's sandstone to 
the surface on Rock river and the Lower Magnesian limestone 
on the Illinois." Its general trend is N. N. W. to S. S. E. How 
far south of the Illinois it extends he did not determine. The 
continuation of this axis to the north west across the lead 
region of Wisconsin is discussed by Prof. Chamberlin in con- 
nection with the prominent flexure axes of that state. - 
The east-to-west axis whose probable distribution has been 
given, apparently connects the Cincinnati anticlinal with the 
upheaval in northern Illinois and southwestern Wisconsin, and 
thus introduces a new feature into the dynamics of the Missis- 
sippi basin. The prominence of this axis above the region north 
of it has been shown by borings in Porter and LaPorte coun- 
ties, Indiana, which strike the Trenton at 400 — 600 feet be- 
low tide, and above the region south of it by a boring at Terre 
Haute, 2400 feet in depth, which does not reach the bottom of 
the Niagara limestone, and by many borings in the coal-fields 
of eastern and central Illinois, records of which occur in the 
geological reports of that state, which are still in coal measure 
strata some distance below sea-level. 
Distribution of natural gas. — The majority of the strong 
gas wells of Indiana lie within the boundaries of the elevated 
portion of the Cincinnati anticlinal. The limits of the gas field 
may be roughly outlined by lines connecting the following 
towns : Greenfield, Hancock county, Broad RijDple, Marion 
county, Joliet and Sheridan, Hamilton county, Kempton, Tip- 
ton count}', Kokomo, Howard county, Amboy, Miami county, 
Somerset and LaFountaine, Wabash county, VanBuren, Grant 
' Geology of Illinois ; vol. i. pp. 4-7. 
'^Geology of Wisconsin; vol. iv. pp. 422-438. 
