560 
ARTESIAN WELLS. 
purposes and sometimes even for moving machi- 
nery. The quantity of water thus obtained in 
Artois is often sufficient to turn the wheels of 
Corn mills. 
In the Tertiary basin of Perpignan and the 
chalk of Tours, there are almost subterranean 
rivers having enormous upward pressure. The 
Water of an Artesian well in Roussillon rises 
from .30 to 50 feet above the surface. At Per- 
pignan and Tours, M. Arago states that the 
water rushes up with so much force, that a 
represents the water level within the stratum G ; below this line, 
water would be permanently present in G ; it could never rise 
above it, being relieved by springs that would overflow at a. 
The line, c. d. represents the level above which the water could 
never rise in the stratum F ; and the line e, f, represents the 
highest water level within the stratum E. The discharge of all 
rain waters that percolated the strata E, F, G, thus being effected 
by overflowing at e. c. a. 
If common wells were perforated from the surface, i. k. 1. into 
the strata G. F. E, the water would rise within them only to the 
horizontal lines a b, c d, ef. 
Tlie upper porous stratum C, also, would be permanently 
loaded with water below the horizontal line, g, h, and perma- 
nently dry above it. 
The theoretical section, PI. 69. fig. 2. represents a portion of a 
basin intersected by the fault H, L, filled with matter impermeable 
to water. Supposing the lower extremities of the inclined and 
permeable strata N, O, P, Q, R, to be intersected by the 
fault or dyke H, L, the rain water which enters the uncovered 
portions of these strata, between the impermeable clay beds, 
A, B, C, D, E, would accumulate in the permeable strata up to 
the horizontal lines, A A", B B", C C", D D", E E". If an Arte- 
sian well was perforated into each of these strata to A', B', C', 
