31z THE ELEMENTS OF ECONOMIC GEOLOGY

water supply, 236 ; meteoric, 219-20;
 percolation, 223-4 ; percolation
 wells, 229; permeability of
rock, 228; piezometers, 226;
plutonic, 220-2; in primary
rocks, 220; rainfall, disposal of
222-3 ; IeESEIVOIr sites, 237 ; rock:
pressure, 232 ; run-off, 222-3; soil
purifying action of soaks, 230;
springs, 230; subterranear
waters, circulation of, 224-36,
subterranean water, quantity;
225 ; three sources of water, 219;
town supplies and settlement, 236

water storage, 227-8; water
table, 224 ; wells, flowing, 230-6
wells and springs, 230-6; wells.
yield of, 227.
Waves, 238.
Wolframite, 79.
Wood, fuel value, 261.

Zinc, 109-110; distribution, 109 ;
Franklin ores, 109-10; origin of
name, 109; qualities and price,
109.
Zircon, 166.

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