SUBTERRANEAN WATERS. 665 



Another well, in Westphalia in Germany, is 2,385 feet deep. 



An Artesian boring at St. Louis has been carried to a depth of 3,843£ feet, but with- 

 out obtaining a flow of water to the surface ; the last 250 feet were in granite of the 

 Archaean, so that the whole of the Paleozoic of the region, from the Carboniferous 

 downward, was passed through. (Broadhead.) A well at Louisville, Kentucky, 2,086 

 feet deep, supplies an abundance of water, though a little brackish. 



In some cases, subterranean waters are under pressure from an accumulation of gas 

 which is in a state of compression sufficient to send them to the surface without other 

 aid, whenever reached by a boring. 



The subterranean waters sometimes, and perhaps often, form large 

 underground rivers. Those of the caverns of Kentucky and Indiana 

 have their cascades, like ordinary rivers, and may be navigated for 

 long distances. It is stated that there are a hundred thousand miles of 

 underground chambers in the Subcarboniferous limestone of Kentucky 

 (Shaler), and several thousands in that of Indiana; and others, also, 

 though of less extent, in Silurian limestones. Into these caverns rivers 

 enter and become " lost rivers," while from others issue great streams, 

 whose former history is unknown. The Cave of Adelsberg, 22 miles 

 northeast of Trieste, has its river; and the Jura Mountains send 

 forth streams to daylight full grown. On all shores the outward flow 

 of the under-ground waters prevents the in-flow of the salt water. 

 Springs are common on shores ; and, occasionally, their waters rise 

 in large volumes in a harbor, or out to sea, some miles distant from a 

 coast. 



2. Mechanical Effects. 



Subterranean waters act mechanically by erosion, and by softening 

 or loosening permeable beds, and adding to their weight. 



1. Erosion. — Subterranean streams produce erosion, like running 

 water above ground, and may excavate a channel in the same way. 

 Caverns are made partly by erosion and partly by the dissolving ac- 

 tion of water; and the great extent of the caverns of Kentucky and 

 other parts of the Mississippi Valley may be viewed as examples of 

 what has been accomplished by underground streams. A common 

 effect of such excavations is the production of subsidences of the soil 

 and overlying rocks, and the formation of sink-holes. Small shakings 

 of the earth may be a consequence of the fractures of undermined 

 strata. 



2. Softening Beds and adding to their Weight. — The following are 

 among the effects consequent on this softening of beds by water. 



(1.) Land-slides. — Land-slides are of three kinds: — 

 (a.) The mass of earth on a side-hill, having over its surface, it may 

 be, a growth of forest trees, and, below, beds of gravel and stones, 

 may become so weighted with the waters of a heavy rain, and so 

 loosened below, by the same means, as to slide down the slope by 

 gravity. 



