334 THE GEOLOGY OF MINNESOTA. 



[Explorations for coal. 



equal abundance, is an evidence of the former extent of the Devonian rocks in that direction. 

 The Devonian does not certainly cross the Minnesota river. Yet in McLeod county, which lies 

 in the line of strike of the Devonian of Iowa and Freeborn county, toward the northwest, on the 

 opposite side of the Minnesota river, the same limestone boulders are very abundant, some being 

 so large as to have been reputed rock in tilu, and quarried as such till exhausted. There is, in the 

 neighborhood of Fieeborn, an area of the Cretaceous, which must overlie the Silurian limestones. 

 This Cretaceous area is believed to extend north and south across the west end of the county and 

 to be roughly coincident with the flat and prairie portion in the western part of the county, in 

 which case it also overlaps the Devonian. 



Explorations for coal. 



In common with many other places in southern Minnesota, Freeborn township, in the north- 

 western corner of this county, has furnished from the drift, pieces of Cretaceous lignite that 

 resemble coal. These have, in a number of instances, incited ardent expectations of coal, and 

 led to the outlay of money in explorations* Such pieces are taken out in digging wells. The 

 opinion seems to grow, in a community where such fragments are found, that coal of the Carbon- 

 iferous age exists in the rocks below. In sinking a drill for an artesian well at Freeborn village, 

 very general attention was directed to the reported occurrence of this coal in a regular bed in con- 

 nection with a "slate rock''. This locality was carefully examined, and all the information was 

 gathered bearing on the subject that could be found. The record of the first well drilled is given 

 below, as reported by the gentleman who did the work. 



1. Soil and subsoil, clay 15 feet. 



2. Blue clay 35 feet. 



3. " Conglomerated rock " (Had to drill) 2 in. 



4. Sand with water 5 feet. 



5. Fine clay, tough, and hard to drill, with gravel, and limestone pebbles 60 feet. 



6. Sand with water 4 in. 



7. " Slate rock " i \ 7 feet. 



8. "Coal" | Probably Cretaceous ) _6feet_4_in. 



Total depth 127 ft. 10 in. 



This indication of coal induced the drilling of another well situated one hundred feet distant. 

 toward tha northeast. In this the record was as follows, given by the same authority. 



1. Soil and subsoil, clay 15 feet. 



2. Blue clay 33 feet. 



3. " Conglomerated rock " 2 in. 



4. Sand with water and pieces of coal 12 feet. 



Total depth 60 feet 2 in. 



When the drill here reached the "conglomerated rock", it was supposed to have reached the 

 "slate rock'', No. 7, of the previous section. The amount of coal in the sand of No. 4 was also 

 enough to cause it to be taken for No. 8 of the previous section. Hence the boring was stopped ; 

 and having thus demonstrated the existence of a coal-bed, to the satisfaction of the proprietors, 

 the enterprise was pushed further in the sinking of a shaft. In sinking this shaft water troubled 

 the workmen so that at thirty-five feet it had to be abandoned. 



Three-quarters of a mile north of these drills a shaft was sunk fifty-seven feet, but not find- 

 ing the coal as expected, according to the developments of the last section above given, this 

 exploration ceased. In this shaft the oveiseer reports the same strata passed through in the 

 drift as met with in the first well drilled, but the so-called "conglomerated rock" was met at a 

 depth of forty-five feet. The sand below the ''conglomerated rock" here held no water, but was 

 full of fine pieces of coal. Before sinking the shaft at this place a drill was made to test the strata. 

 These being found "all right" the shaft was begun. In that drill gas was first met. It rose up in 

 in the drill-hole, and being ignited it flamed up eight or ten feet with a roaring sound. The shaft 

 was so near the drill-hole that it drew off the gas gradually, allowing the intermixture of more air, 

 thus preventing rapid burning. From this place the exploration was re-directed to the first situa- 

 tion, where another shaft was begun. This was in search for the "lower rock", so called, or the 

 "slate rock" supposed to overlie the "coal". Here they went through the same materials, shutting 



