ARTESIAN WELLS IN THE DESERT. A481 
These wells, however, are too few and too scanty im supply 
to serve any other purposes than the domestic wells of other 
countries, and it is but recently that the transformation of 
desert into cultivable land by this means has been seriously 
attempted. The French Government has bored a large num- 
ber of artesian wells in the Algerian desert within a few years, 
were of carboniferous and magnesian limestone alternating with sandstone. 
The remainder of the well passes through igneous rock. At St. Louis the 
Missouri and Mississippi rivers are not more than twenty miles distant from 
each other, and it is worthy of note that the waters of neither of these two 
rivers appear to have opened for themselves a considerable subterranean pass- 
age through the rocky strata of the peninsula which separates them. 
When in boring an artesian well water is not reached at a moderate depth, 
it is not always certain that it will be found by driving the drill still lower. 
In certain formations, water diminishes as we descend, and it seems probable 
that, except in case of caverns and deep fissures, the weight of the superincum- 
bent mineral strata so compresses the underlying ones, at no very great dis- 
tance below the surface, as to render them impermeable to water and con- 
sequently altogether dry. See London Quarterly Journal of Science, No. xvii., 
Jan., 1868, p. 18, 19. 
In the silver mines of Nevada water is scarcely found at depths below 1,000 
feet, and at 1,200 feet from the surface the earth is quite dry.—American 
Annual of Scientific Discovery for 1870, p. 75. 
Similar facts are observed in Australia. The Pleasant Creek News writes: 
‘‘ A singular and unaccountable feature in connection with our deep quartz 
mines is being developed daily, which must surprise those well experienced in 
mining matters. It is the decrease of water as the greater depths are reached. 
In the Magdala shaft at 950 ft. the water has decreased to a minimum ; in the 
Crown Cross Reef Company’s shaft, at 800 ft., notwithstanding the two reefs 
recently struck, no extra water has been met with; and in the long drive of 
the Extended Cross Reef Company, at a depth of over 800 ft., the water is 
lighter than it was nearer the surface.” 
Boring has been carried to a great depth at Sperenberg near Berlin, where, 
in 1871, the drill had descended 5,500 feet below the surface, passing through 
a stratum of salt for the last 3,200 feet ; but the drilling was still in progress, 
the whole thickness of the salt-bed not having been penetrated.—Aws der 
Natur, vol. 55, p. 208. 
The facts that there are mines extending two miles under the bed of the 
sea, which are not particularly subject to inconvenience from water, that lit- 
tle water was encountered in the Mt. Cenis tunnel, 3500 feet below the surface, 
and that at Scarpa, not far from Tivoli, there is an ancient well 1700 feet 
deep with but eighteen feet of water, may also be cited as proofs that water 
is not universally diffused at great distances beneath the surface. 
