XXXVI. HYDRAULIC ASPECT OF THE ARTESIAN PROBLEM. 
velocity, at least if the general condition of its surface is 
known. 
3. Conditions of fiow in sand and rock.—The experi- 
ments of Professor F. H. King’ shewed that soils, sands, 
and sandstones may contain up to over 40% of water, sand- 
stone ranging from 15 to 38%. Much less porous rocks may 
also contain water, for example, even marble will absorb 
0°23%. The condition of movement may be aggregatea 
under three categories :— 
(1) Gravitational: (2) Capillary: (3) Thermal. 
It will be well here to mention that the influence of baro- 
metric pressure is very marked in the case of gravitational 
movement of water; as in the discharge from springs, etc. 
This will be referred to hereinafter. Except as in so far 
as surface-tension interferes therewith, water will of course 
flow gravitationally (i.e. downward) in rock. Capillary 
movement will take place in any direction, but upward 
movement has been experimentally observed to shew 
diminution as indicated in the following table :— 
Height 1 ft. 2°37 tbs. 2°05 Tbs. 
Reo wey Ge 2°07 1°62 | per square foot 
oaks Foslibs 1°23 1°00 per 24 hours. 
ree Shook Gs 0°91 0°90 ) 
4, Hxperimental investigation.—Professor King made a 
great many experiments of the rate of percolation from 
sands of various degrees of fineness under gravitational 
head, of the capillary lift, and of the evaporation; these 
would be of some service in judging how much water, out 
of the total annual fall, may be assumed to contribute to 
the artesian supply. The fact referred to by Professor 
Gregory, that the lines of flow of water do not take the 
shortest direction, is easily understood. (See Fig. 1.) 
1 Principles and conditions of the movements of ground Wied S. 
Geol. Survey Report, 1897-8, pp. 59 — 294. 
