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XXX. HYDRAULIC ASPECT OF THE ARTESIAN PROBLEM. 
That the hydrostatic pressure does not so rapidly dis- 
appear as is assumed by Professor Gregory, is easily seen 
when it is remembered that in a uniform stratum the 
velocity of the water diminishes as the distance from. the 
bore is increased in the ratio r/R, in which r is the radius 
of the bore, and R the distance of the point considered: 
that is to say, putting v for the velocity at the bore of 
radius r, and V for that at the distance R from its centre, 
V = ori cokes (1.) 
so that even for the smallest bore, say of 3 inches radius, 
at the distance of one mile the velocity would be only 
1/21,120 of its velocity as it entered the bore; or again, a 
10-inch bore discharging 1 million gallons per diem, from a 
10-foot stratum, would acquire a velocity of about 54 feet 
per second across the surface into the bore. At the dis- 
tance of 1 mile this would involve a velocity of only about 
zoo inch per second. | 
(d) The rate of loss of hydrostatic head depends upon 
the rate of fiow and is very small when the velocity is 
small, as previously explained. 
(e) That the earth’s internal heat affects the question is. 
indubitable, but that it is not the causa proxima is equally 
indubitable, as will appear when it is remembered that the 
water is not absolutely imprisoned, and that :-— 
(f) The pressure is never relieved so far as to allow of 
ebullition. 
(g) Hence the statement in (g) above is inaccurate. 
4. Complication by existing facts.—The problem of 
exactly determining the possible flow by tapping the artes- 
ian stratum at various points, and of reaching something 
like definite knowledge of the extent of safe exploitation, 
is greatly complicated by the fact that the hydraulic 
records of the bores (where such records exist at all) are 
