516 THE GEOLOGY OF MINNESOTA. 



[Peat, Mounds. 



Weimer. "Sec. 31. A thin deposit of about six inches of peat covers about half an acre. 



mostly under water. This is the only pea 1 that can be found in the vicinity of Heron Lake." 

 Wisconsin. "On the S. E. J of sec. 27, Mr. W. V. King correctly deScribes a peat marsh." 

 Round Lake. "Sec. 20; land of Everett \V. Scovill. Peat here covers four or five acres. 



and is associated with a deposit of bog iron ore." 



Analyses of peat ashes. 



The ashes of the specimens of peat mentioned as analyzed by Prof. Peckham, were also sub- 

 jected to analysis by him, and their composition was found to be as follows: 



1. 3. 3. 4. 5. . 



Silica 64.27 88.28 81.99 72.64 64.37 68.06 



Carbon 2.80 1.32 1.14 0.75 0.10 1.34 



Iron oxide and iron phosphate .. 9.75 6.34 9.39 15.46 21.41 8.82 



Lime 15.75 0.84 4.84 5.87 6.26 5.03 



Magnesia 1.77 0.51 0.60 trace 1.54 4.81 



Sulphuric acid 3.69 trace 1.12 5.73 7.58 6.53 



Undetermined... . 1.97 2.71 0.92 5.41 



100.00 100.00 100.00 100.45 101.32 100.00 



Traces of phosphoric acid were found in all; and of alkalies in Nos. 2 and 3. Carbonic acid 

 was present in considerable amount in Nos. 1 and 6, and in very small amount in No. 2. 



ABORIGINAL EARTHWORKS. 



Though artificial mounds probably exist in these counties, none were observed during their 

 examination. 



In the north part of section 17, Spirit Lake, about a mile south of the state line, an inter- 

 esting group of six or eight mounds, of the usual round form and two to four feet high, was seen 

 beside the road, at the northwest side of Spirit lake and a short distance south of Little Spirit 

 lake, on land fifteen to twenty-five feet above them. 



