WATER SUPPLY OE EASTERN AND SOUTHERN FLORIDA. 143 
and form a finer grained sandstone grading ultimately into a clay. 
Similarly, a sandstone, or other pervious formation, may pinch 
out as a result of the thickening of a shale or clay bed. The term 
“artesian slope” has been applied to such an area to distinguish 
it from an artesian basin. 
The friction of water threading its way long distances 
through the pores of an inclined pervious formation may result 
in an appreciable artesian pressure. That this is true, may be 
demonstrated by the following very simple experiment: Fill a 
tube of any length with sand, and incline at a convenient angle. 
The sand of the tube represents the pervious water-bearing 
stratum; the tube itself, the impervious confining strata. Let 
smaller tubes placed vertically be welded into the larger tube. 
These vertical tubes represent bored wells. The water will be 
found to rise in the vertical tubes, exhibiting an appreciable 
artesian pressure due to the friction of flow through the sand. 
ARTESIAN WATER FROM UNCONFINED HORIZONTAL BEDS. 
It is, doubtless, possible to obtain artesian water in some in¬ 
stances from unconfined horizontal beds. This condition is illus- 
Fig. 3.—Illustrating artesian water from unconfined horizontal beds. 
The pressure in this case is due to the friction of water moving through 
the pores of the rock. 
trated by the following sketch taken from the report of M. L. 
Fuller.* It is possible that some of the small local flows obtained 
in the lake region of interior Florida are due to similar conditions. 
ARTESIAN WATER FROM SOLUTION PASSAGES. 
Solution passages through limestones undoubtedly facilitate 
the free movement of water. If limestones should be otherwise 
