TOPOGRAPHY. 657 



In this connection may be noticed the diminution of water in the 

 Lead region since the early mining times. In comparing the streams 

 at present with those recorded in the government surveys, it will be 

 fornd that many of the smaller ones are entirely dry, and others 

 nearly so. Numerous springs, which formerly furnished an abund- 

 ant supply of water, are now dry, and have been replaced by wells, 

 sunk to obtain water from a deeper stratum. 



FIG. 1. 



GENERAL SECTION OF PLATTE RIVER VALLEY. 

 1. Trenton Limestone. 2. St. Peters Sandstone. 3. Lower Magnesian -Limestone. 



In T. 5, R. 6 W., are several streams flowing into the Mississippi 

 river, which present some curious features in common. They vary in 

 length from three to five miles, and take their rise in the Trenton 

 limestone. They occupy quite long and narrow valleys of erosion, 

 and their dry beds may be distinctly traced in them. They are quite 

 large streams, and continue increasing in size for a mile or two from 

 their sources, until they reach certain beds of the Lower Magnesian 

 formation, when they gradually disappear. 



The large streams of the Lead region contain a much smaller 

 amount of water than heretofore. Several places were seen where 

 old mills, formerly operated by water-power, had been abandoned, on 

 account of a diminishing and final failure of the supply. 



The diminution is not confined to surface water, springs, streams 

 and the like, but is true, to a greater or less extent, of all the mining 

 ground of the region. In many instances this circumstance alone has 

 led to the reopening and profitable working of mines which years 

 ago were abandoned on account of water, with ore "going down" in 

 the crevices. 



It is probable that cultivation of the land is the chief cause of this 

 decrease, as a much greater amount of surface is thus exposed, and 

 evaporation takes place more rapidly and in larger quantities. Re- 

 moval of the timber is, without doubt, another cause of this decrease. 

 The soil of the timbered land contains more moisture than that of the 

 prairie; and in all countries, the removal of the timber has always 

 been followed by a marked decrease of the water supply. This was 

 Wis. SUR. 42 



