TOPOGRAPHY. 



659 



of the Blue Mound springs is the same as that of all other springs in 

 the Lead region, which is about the mean temperature of the earth 

 through which they flow. Were they thermal springs, or of igneous 

 origin, we should expect to find at least some lingering traces of heat, 

 to show us from whence they came. In view of these facts, it seems 

 more logical to look for their origin in the natural and self evident 

 causes presented, than to attribute them to more complex conditions, 

 imperfectly understood. v 



FIG. 2. 



SKETCH OF THE UPPEU PART OF THE BLUE MOUNDS. 



1, Flinty cap of the West Mound; 2, Horizon of the springs; 3, Niagara limestone; 4, Cincinnati 



group; 5, Galena limestone. 



In such portions of the country as are not liberally supplied by 

 nature with springs, water is easily and abundantly obtained by 

 means of wells. Their average depth is about twenty-five feet; this, 

 however, depends chiefly on the locality in which they are sunk, those 

 on the ridges and prairies being deeper than the rest. Round wells, 

 of four or five feet diameter, are usually sunk for shallow depths, 

 sometimes being as deep as sixty feet. Wells are sometimes obtained 

 by drilling; such borings being chiefly confined to the prairie, and 

 seldom exceeding sixty feet in depth. They are then furnished with 

 a windmill pump, and supply an abundance of clear water for stock 

 and farm purposes. 



Nearly all the water in the Lead region, whether in springs or 

 wells, holds in solution a small portion of lime and magnesia, and 

 a still smaller quantity of sodium, iron, alumina, and silica. The 

 presence of these salts usually gives the water what is called a hard 

 taste which is more noticeable in the limestone than in the sandstone 

 springs, and not infrequently induces persons to believe them pos- 

 sessed of medical properties. 



The following analysis, which is believed to be a fair sample of the 

 quality of the water in the springs and wells of the Lead region, is in- 

 serted to show the small amount of foreign substances which they con- 

 tain. The well is situated on the K E. qr. of Sec. 9, T. 2, R. 9 E., a short 

 distance northwest of the city of Brodhead, on the farm of Mr. Freder- 

 ick Gomber. It was sunk to a depth of about thirty feet, of which 



