"kton.j OHIO RIVER TO CHICAGO. 297 



At Auburn the drill has revealed the presence of a Blight fold in the 

 deep-lying Trenton limestome, snfflcienl for the accumulation of gas 



and oil to a small extent. Despite the monotonous aspect of the pres- 

 ent drift -covered surface, the underlying rocks have recently been found 

 to be more broken by small folds and fractures than any other parts of 

 the two states included in this review. Four or more wells, more than 

 2,000 feet (610 m.) in depth, have been drilled within the limits of 

 Auburn. The gas found in the productive rock has a very high initial 

 pressure. The first flow of the besl wells showed more than 1,000,000 

 cubic feet per diem as the daily yield. The gas has been utilized in 

 the town to the full extent. 



The drift beds exceed 200 feet [60 m.) in thickness here. The fust 

 rock stratum reached beneath the drift IS the basal portion of the black 

 Ohio shale (Devonian). In the Lower Helderberg limestone (TJpper 

 Silurian), which has a thickness of about 600 feet (183 in.), considerable 

 deposits of gypsum and anhydrite are found about midway in tin 1 

 Series. At or about this same point in this series very important beds 

 of rock salt are found in Ohio, Michigan, and Canada. These deposits 

 are now being worked on a large scale in all three places. A valuable 

 deposit of gypsum occurs in the same horizon in Ohio. 



From Auburn to Garrett the basal rock is the black shale previously 

 reported. The drift is nonmorainic. 



At Garrett and just west of Garret! one line of the terminal moraine 

 is crossed. 



At Albion another belt of the terminal moraine is crossed. The 

 region about Albion illustrates well the lack of drainage which is com- 

 mon along the terminal moraine. Numerous shallow lakes, ponds, and 

 swamps are found here. A single lake will sometimes occupy several 

 square miles of the surface. 



Between Teegarden and Walkerton the line traverses the terminal 

 moraine, the black slate of the Devonian still underlying the drift. 



From Walkerton to Coburg is modified drift underlain by the Devo- 

 nian to Union Mills, and by the Niagara limestone (Upper Silurian, 

 Wenlock ! from Union Mills to Coburg. 



At Suman an inner morainic line of the Fake Michigan glacier is 

 crossed. The morainic belt extends westward as far as Woodville. 



Prom Woodville to Chicago the underlying rock is Niagara limestone, 

 buried beneath modified drift, deposited in Lake Michigan during its 



expanded condition, in late glacial and postglacial times. Through a 

 part of this region the sands of old beaches have been extensively modi- 

 fied by the act ion of t he w inds, forming in places Conspicuous dunes. 

 The road follows the southern and southwestern margin of Lake Michi- 

 gan during the last 26 miles (40 km.). 



The Niagara limestone which has been repeatedly named in the pre- 



