ARTICLE XL 



NOTES UPON THE OEOLOGY OF SOME PORTIONS OP MINNESOTA, FROM ST. PAUL TO THE 



WESTERN PART OF THE STATE. 



UY JAMES HALL. 



Bead June 15, 1860. 



During the months of June and July, 1865, I had an opportunity of examining some 

 parts of the State of Minnesota, the geology of which has not heretofore, so far as I am 

 aware, been fully described or understood. 



After returning to St. Paul from an exploration of the St. Croix River, an occasion was 

 offered of going out to the central and western parts of the State, to examine some reputed 

 coal mines. This part of the country was beyond the limits of the settlements, and sup- 

 posed to be subject to the incursions of hostile Indians. There were at that time, beyond 

 the settlements, two ranges of stockades, about fifteen miles distant from each other, at 

 each one of which were stationed a number of mounted men. Beyond these were scouts' 

 camps ; the most westerly of which was at Lake Shetek, near the borders of Pipestone 

 County. It was not deemed prudent to undertake the journey without an escort, and 

 General Sibley, the commander of that military district, very kindly gave an order to Col. 

 Pfaender, commanding officer at Fort Ridgcly, upon the Minnesota River, to furnish a 

 mounted escort sufficient to protect the party in the journey west from the Minnesota 

 River. Fortunately Mr. Henry Back, the chief of scouts, was at Fort Ridgely on our 

 arrival there; and through the kindness of Col. Pfaender, he was placed in command of 

 the escort. 



The geology from St. Paul westward to St. Peter is monotonous and barren of especial 

 interest. Leaving the Lower Silurian limestones of the Trenton, Black River, and Birds- 

 eye formations, we descend at Fort Snelling to the friable and often incoherent sandstone, 

 denominated by Dr. I). I). Owen, St. Peter's sandstone, and which, in the western series, 

 holds the place; of the Cliazy limestone in eastern localities. From this place to St. Peter 

 we find exposed at intervals the Calciferous sandstone or Lower Magnesian limestone, with 

 the Potsdam sandstone beneath, — while the surface is marked by accumulations of sand 

 from the destruction of the St. Peter's sandstone above ; and there are at some points indi- 

 cations of remaining outliers of the same rock. At St. Peter the second river-bottom, or 

 terrace, is underlaid by the Lower Magnesian limestone, which is quarried for a buildin<>- 

 vol. xni. — 12 



