u6 



Cincinnati Society of Natural History. 



It is stated to underlie the limestone that forms the brink of 

 the Falls. " It is of various depths, from ten to seventy-five 

 feet."* 



In 1820, H. R. Schoolcraft was sent by the general govern- 

 ment on an expedition to the sources of the Mississippi 

 River, and he submitted a report of his observations in 1821. 

 This was republished in 1855, !" and in this volume he refers 

 to the geological features of St. Anthony's Falls, where the 

 river is precipitated, at one leap, over " strata of white sand- 

 stone, overlaid by the metalliferous limestone. * * This sand- 

 stone is composed of grains of pure and nearly limpid quartz, 

 held together by the cohesion of aggregation. If my obser- 

 vations were well taken it embraces, sparingly, orbicular 

 masses of hornblende. It is horizontal, and constitutes, in 

 some places, walls of stratification, which are remarkable for 

 their whiteness and purity. "J This is, undoubtedly, the St. 

 Peter's sandstone. 



In 1824, Professor Keating || gave a section of the strata as 

 observed by him at Fort Snelling. In this a sandstone is 

 mentioned as occurring beneath from twenty-five to thirty 

 feet of limestone, and which constituted the principal mass of 

 the bluff. He says : " This is friable, but every fragment, 

 examined with care, seems to be a regular crystal." Keating 

 inclined to the opinion that it must have been a chemical pre- 

 cipitate, and not a mere mechanical deposit. He says : 

 " The process of its formation may have been a rapid one, 

 such as is obtained in the manufacture of fine salt : and to 

 this may be attributed the circumstance of its fine texture. 

 The color is white, sometimes a little grayish, when it resem- 

 bles the finer varieties of Muscovado sugar." § 



In the report of Dr. John Locke, made in 1839,* in describ- 



* Voyage in a six-oared skiff to the Falls of St. Anthony, in 1817. Minn. Hist. 

 Soc. Coll., Vol. II, p. 36 ,pub. i860). 



t Summary narrative of an exploring expedition to the sources of the Missis- 

 sippi. Appendix VII, pp. 303-362. Philadelphia. 1S55. 



% Ibid, p. 330. 



Narrative of an expedition to the source of the St. Peter's River, etc.. per- 

 formed in the year 1S23. under command of Major Stephen H. Long. 2 vols, 1^24. 



\ Quoted in Vol. I of Final Report of Geology of Minnesota. 1SS4, p. 35. 



•"[Comparison of the geological formations of the lead regious of Iowa and 

 Wisconsin, and the cliff formation of Ohio. Indiana, and Kentucky, with various 

 sections.) Kept, of Geol. Expl. of part of Iowa, Wisconsin, and Illinois, by D. D. 

 Owen, pp. 116-126. 26th Cong., 1st Sess.. H. R. Ex. Doc, No 239, 1840. 



