306 THE GEOLOGY OF MINNESOTA. 



[Devonian limestone!. 



to the Devonian, as it has some of the features of the Galena. It is firm, 



t e 



but porous; of a buff color, and a coarse magnesian grain, with superficial 

 cavities due to the weathering out of fossils. It is on the land of Mrs. 

 Annie Postle. A similarly doubtful exposure, slightly quarried, is owned 

 by Dora Wright near the center of sec. 14, Bloomfield, by the roadside. 

 Wm. B. McNee has also taken out the same stone near his barn, N. W. ^ sec. 

 14, and used it in his barn foundation. It here holds considerable calcite. 



At Etna Mr. S. S. Belding has a quarry- in the Devonian. This is a soft, 

 porous stone, in heavy beds, which once held fossils, but which have been 

 lost by absorption, leaving the rock porous, and finely vesicular. Mr. Bel- 

 ding states that this limestone has a hydraulic quality, but as near as can 

 be ascertained it makes simply a quicklime which endures well under 

 repeated wetting. The rock here seen amounts to eighteen or twenty feet. 

 Other quarries, similar to Mr. Belding's, are owned by 0. M. Postle, N. W. J 

 sec. 36, Bloomfield, by George Hoy and Mr. De For, 1ST. E. ^ sec. 25, and by 

 H. T. Odell, S. E. i sec. 36. 



At De For's mill, N. E. J sec. 25, Bloomfield, the rock* exposed is fine 

 and even-grained, belonging probably to the lower portion of the Devonian. 

 It embraces one thin layer of a shaly limestone which has turned white. 

 It makes a good quicklime. It is in heavy beds of about eighteen inches, 

 and holds a coarse coralline form (Syringopora ?) seen also at the quarry 

 of Mrs. Postle, already mentioned. Below these heavy layers is a bed of 

 shale which was exposed in the digging of the mill-race, having a thickness 

 of five and a half feet. Below that thickness the shale becomes arenace- 

 ous, and in the weather crumbles to pieces. Among the crumbled frag- 

 ments are indistinct remains of the buckler of a small trilobite. This shale 

 may belong to the Maquoketa shales of Iowa. At Spring Valley quarries 

 are worked to a greater or less extent by Mr. Willard Allen, Thomas Thayer, 

 Eurylas Parsons and Nelson Smith. These openings are on the south side 

 of the valley and are all in about the same kind of stone. Some of them 

 furnish as yet only rough large pieces, water-worn and rusty, dislodged 

 from their original places. The rock has undergone long weathering and 

 erosion at Spring Valley, and is disintegrated and changed to a considerable 

 depth. Along the road near the public school, a small cut in the shat- 

 tered crumbling layers has exposed a great number of detached casts of a 



