BLUE EABTH COUNTY. 451 



Bricks.) 



Analysis of portion dissolved by hydrochloric acid: 

 Fe2Oj with small amount of 



A! 2 Oj and SiOj 3.U per cent., being 2.65 per cent, of whole rock. 



CaO CO.. 55.47 " " " 46.86 " " " ' " 



MgO CO 2 39.73 " " "33.56 " " " " 



98.34 83.07 



Analysis of portion left undissolved by hydrochloric acid: 



SiO 2 77.90 per cent., being 12.10 per cent, of whole rock. 



A1 2 O 3 19.24 " " " 2.99 " ' " " 



CaO 34 " " " .05 " ' " " " 



MgO 12 " " " .02 " 



Alkalies traces. 



Organic matter traces. 



97.60 15.16 



It appears, therefore, that the rock is a magnesian limestone, with about 12 per cent, of 

 silica and somewhat over 2 per cent, of oxide of iron. 



Bricks. The principal brick-making in this county is at Mankato. 



The Mankato Brick company, O. K. Mather, superintendent, has three yards, two of which, 

 making cream-colored bricks, are situated in the north part of the city, about fifty rods southwest 

 from the lime-kilns, while the third, making red bricks, is a mile distant to the southwest. They 

 all are on the bottomland, and the material used is the recent alluvium of the Minnesota river, 

 the excavations reaching from the level of low water to fifteen feet above it. No sand is needed 

 for tempering at these or the following yards. The difference in color of these bricks seems to be 

 due to the mode of burning. With a rapid, hot fire, they take a light buff or cream color through 

 the whole kiln; but when more slowly burnt they are red, except near the fire, where they become 

 brownish or whitish gray. This business was begun ten years ago, and the annual product has 

 averaged about 4,000,000. In 1880 it was 6,000,000, about two-thirds being cream-colored and 

 one-third red. The bricks are sold at $5 to $7 per thousand, loaded upon the cars. Many of them 

 go to distant points, as Saint Paul, Minneapolis, and Duluth. and to southwestern Minnesota and 

 northern Iowa. About a sixth of a mile southwest from the third of the foregoing yards, in the 

 west part of Mankato, F. Polchow & Co. have made red bricks eight years, averaging 4,000,000 

 yearly, and selling at about $6 per M. The material used is the same fine alluvial silt of the river. 

 All these bricks are of excellent and durable quality. 



In 1879 Willimes & Grothe began making bricks about one and one-fourth miles north of 

 Mankato, being at the south side of a creek close southwest of Jefferson's quarry. They also use 

 alluvium, producing red bricks excepting near the fire, where they are light gray. About 150,000 

 were made in 1879, and 3,000,000 in 1880, bringing $5 to f 5.50 per M. 



Bed bricks have also been made since 1878, by Gekeler brothers, in the N. W. \ of section 

 8, McPherson, using the alluvium of the Le Sueur river. Their annual product is about 50,000, 

 selling at $5 per M. 



Brick-making was formerly done, but is discontinued, at five places in the west part of the 

 county, as follows: by O. E. Mather, from 1867 to 1871, on the southeast side of Willow creek, 

 in the S. W. i of section 6, Shelby, producing red bricks of fair quality; also by Mr. Mather, dur- 

 ing the next two years, in the southwest edge of the town of Lake Crystal; in 1869, south of the 

 Garden City fair-ground, on the north bank of the Watouwan river, red bricks, cracked by par- 

 ticles of limestone contained in the sand which was employed for tempering, while the clay used 

 is free from gravel and is said to have been tested in the Mankato pottery and found suitable for 

 making stone-ware; in the N. W. } of section 8, Shelby, on the east side of the Blue Earth river, 

 about eight years ago; and, at nearly the same date, in the S. W. \ of section 32, Ceresco, west 

 of I'erch creek. 



Fire-bricks. Mr. David P. Davis states that the Cretaceous clay in the 

 lower part of his quarry at South Bend has been tested, and found to be 



