88 LOWER PENINSULA. 



Similar shales, alternating occasionally with a seam of sand- 

 stone or limestone, continue to a total depth of 447 feet below 

 the surface. 



Only half a mile east from this drill-hole, on a higher level, in a 

 brick-yard, shale beds of a seemingly higher position than those 

 penetrated in the drill-hole are well denuded. The exposure com- 

 prises about 25 feet of strata, principally a soft blue shale with 

 interstratificd seams of arenaceous, thin-bedded flagstones, and 

 full of lenticular iron-ore geodes of concentric structure, contain- 

 ing sometimes a loose, shaking nucleus. The superficial crust of 

 the geodes is generally transformed into hydrated sesquioxide 

 of iron ; the internal portions are gray, compact, amorphous 

 protocarbonate of iron. The shale beds, otherwise horizontal, 

 are considerably flexured in serpentine lines, which disturbance 

 in all probability was caused during the drift period by pressure 

 of the advancing glacier masses on those beds which they encoun- 

 tered. The base of the hill capped with this shale is all en- 

 veloped by a mantle of drift deposits. No fossils were found in 

 this locality. 



Similar shales are uncovered in another brick-yard on the north 

 side of the city of Cold water ; they are likewise crowded with 

 iron geodes, some of which are fossiliferous, inclosing Chonetes 

 Illinoisensis, etc. Below the shales, argillaceo-micaceous sand- 

 stones come to the surface, which contain iron geodes similar to 

 those of the shales. All the hillsides north of Coldwater River 

 valley, for several miles eastward from Coldwater, are composed of 

 this shale formation covered by a more or less thick coating of 

 drift material, but in other parts of the State, brick-yards generally 

 use the drift clay. In the vicinity of Coldwater, all the clay used for 

 brick-making is derived from the shale beds of the Waverly group, 

 which are ploughed up and left to the influence of the weather for 

 about a year, by which time the shale has decomposed into a soft, 

 plastic clay. In the brick-yard of Mr. Merritt, 2 miles south of Union 

 City, Town. 5, R. 7, west, Sect. 16, the surface beds are sandy shales 

 with seams of calcareo-ferruginous rock, containing many small cylin- 

 draceous nodules composed of compact carbonate of iron, besides 

 a number of partially very finely preserved fossils. Below these 

 beds are yellowish gray soft shales, used for brick-making, which 

 also contain numerous kidney-ore concretions of lenticular form. 



