658 GEOLOGY AND TOPOGRAPHY OF THE LEAD REGION. 



notably the case in the Hartz mountains, of Prussia, after the fir and 

 hemlock forests were removed. When the mountain sides were again 

 planted with the indigenous trees, by order of the government, their 

 growth was found to be attended by an increase of water in the 

 streams arid springs. 



Springs and Wells. The Lead region is one of the best watered 

 tracts of country in the state. Springs are very numerous, both about 

 the sources of the streams and frequently in their banks. They aro 

 found in all the geological formations, but with the greatest frequency, 

 and of the largest size, between the bottom of the Galena limestone 

 and the top of the St. Peters sandstone. Such springs are usually 

 found flowing along the surface of some layer of clay, and finding a 

 vent in the outcrop of an opening. The clay "openings " most favor- 

 able to their formation are, the " Upper Pipe Clay opening," situated 

 on the top of the Blue or Trenton limestone, and separating it from 

 the Galena limestone; the "Glass Hock opening," separating the 

 Blue and underlying Buff limestone; and the "Lower Pipe Clay 

 opening," situated in the lower part of the Buff limestone; the latter 

 however, does not seem to be so persistent a bed as the other two. 

 Springs are by no means confined to these three openings, but occur 

 in many of the beds of the Galena limestone, as well as in the lower 

 formations; usually, however, flowing over an impervious bed of clay, 

 or some layer of rock too compact to admit of the passage of water 

 through it. 



In this connection it is desired to call attention to the springs sit- 

 uated about 150 feet below the summit of the west Blue Mound. 

 They have been attributed by many persons to thermal, igneous, and 

 other deep-seated agencies, and by some to hydrostatic pressure. The 

 following facts are offered in regard to these springs: (1) They are 

 found at intervals on all sides of the mound, at a uniform elevation, 

 either as springs or low wet ground, and always on the surface of a 

 stratum of clay impervious to water. (2) They flow most abundantly 

 during and after rainy seasons, and in summer are frequently nearly 

 dry. (3) They are surmounted by the cap of the mound, which is al- 

 most a solid mass of flint, and presents a surface of about 100 acres 

 as a watershed. The annual rainfall in the Lead region is about 30 

 inches, of which about one-quarter is removed by evaporation and the 

 requirements of vegetation, while the remainder finds its way to the 

 springs and streams. On the one hundred acres lying above the 

 springs, there fall annually 10,890,000 cubic feet of water, of which 

 three-quarters, or 8,167,500 cubic feet pass out through these springs, 

 which seems amply sufficient to supply them. (4) The temperature 



