DEFIANCE COUNTY. 425 



GEOLOGICAL STRUCTURE. 



The rocks of the county embrace the limestones of the Devonian and 

 the overlying shales. The highest observed rock is the black slate, but 

 it is very probable that higher formations of shale, corresponding to 

 those above the black slate on the eastern side of the anticlinal, also 

 succeed in ascending order in Defiance county, occupying a surface area 

 comprising most of the northern tier of towns. The general dip is to- 

 ward the north. The lower portion of the great Corniferous group of Dr. 

 Newberry 'forms the surface rock of the south-eastern half of Highland 

 township. The upper portion of the same, represented by the blue stripe 

 on the map, succeeds it on the north, its northern boundary crossing the 

 Auglaize River in section 3, Defiance township. The greater portion of 

 the Hamilton fossils found in this county pertains to the lower part of 

 this limestone, but they are found also throughout its whole thickness. 

 It is hence styled Hamilton on the accompanying map, that shale which 

 Dr. N. regards as Hamilton in the central portion of the State not hav- 

 ing been discovered in Defiance county. Its place is occupied by the 

 base of the black slate or Huron shale. (See the Reports on the Geology 

 of Paulding County and of Defiance County.) This belt of Hamilton, or 

 Upper Corniferous, as it has been styled in the reports on Sandusky and 

 Seneca counties, crosses Highland and Defiance townships, underlying 

 also the south-eastern portion of Richland. The black slate underlies 

 Defiance city. The Maumee River runs over the black slate from near 

 the point of its entrance within the county to within a mile and a half 

 of the Henry county line. The remainder of the county is colored to 

 represent the black slate, although it is not known, as already remarked, 

 but higher formations succeed it in the northern towns of the county. 

 The Drift is so uniformly spread as to hide the rock, from view. 



The Huron Shale. — The only known exposures of the black slate are in 

 the valleys of the Auglaize and the Maumee. Beginning on the south, 

 the outcrop at the mouth of Powell's Creek is the first and most import- 

 ant, owing to the enterprise there started by Mr. Gleason of manufac- 

 turing hydraulic cement from its lower beds. (See Geology of Marion 

 County.) This is on the S. E. J section 34, Defiance township, on the right 

 bank of the Auglaize. The thickness of the black slate here developed 

 is seventeen feet. This includes that passed through in digging a well 

 at the same place. This well was drilled for the express purpose of test- 

 ing the thickness of the slate. The drill then struck a very hard rock, 

 which, after two or three hours' drilling, was so little affected as to cause 

 the abandonment of the well. The rock here struck can have been no 



