304 THE GEOLOGY OF MINNESOTA. 



I Devonian limestones. 



generally less than eight inches, though when quarried it is often taken out 

 in heavy blocks more than two feet thick. Its color is yellowish, and it is 

 tolerably free from such impurities as chert or calcite lumps. It is suitable 

 for most purposes in common masonry. It has a few brachiopods, Atrypa 

 reticularis being the most common and most conspicuous, and an incrust- 

 ing bryozoan like Fenestella. 



At Lime Springs station, Iowa, is a quarry in the Lower Devonian, expos- 

 ing about ten feet. At Hopkins' quarry, situated two miles west and a 

 little south of Lime Springs, about twelve feet in heavy layers can be seen, 

 without fossils but holding some flint dip S. E. At Chester similar beds 

 are exposed near the mill, three-fourths of a mile south of the state line. 

 It is here in heavy beds, of a soft, uniform, granular texture and yellowish 

 color, useful for cut stone. 



At Foreston, one mile south of the state boundary line, the Devonian 

 appears in the lower river bluffs, and is in very rough and heavy beds. It 

 presents numberless cavities of all shapes, as large as a thimble and larger, 

 and often iron-stained. It here has a noticeable dip to the south. While 

 it is fossiliferous, it is so coarsely and so completely crystalline that the fos- 

 sils are either entirely absorbed or remain as indistinct impressions or im- 

 perfect casts. It contains white calcite in some large masses. The river 

 itself at Foreston is probably on the Galena, the water-power there improved 

 being due to a change from the firm overlying layers to a soft shale indi- 

 cating the upper portion of the Hudson River group. On the state line, due 

 north from Foreston, a limestone appears in the road, of a coarsely crys- 

 talline grain, with calcite and cavities, entirely like the Devonian. It is 







observable in a number of the hilltops, and extends half a mile, at least, 

 north of the state line, north from Foreston; and a fourth of a mile east 

 (N. E. | sec. 35, York) the Galena appears on the northeast side of a ravine, 

 while the Devonian appears on the southwest side, the road running be- 

 tween the two and probably passing over the Maquoketa shales. The rock 

 has a perceptible dip toward the south. The Devonian occupies the high 

 river-bluffs from that point nearly to Granger, on the north side of the river, 

 when it passes to the south and lower beds take its place, both having a 

 dip toward the south. This rock is probably that which is said to appear 

 iu the river banks, sec. 34, Beaver, on Jerry Kingsley's land. 



