31z THE ELEMENTS OF ECONOMIC GEOLOGY 
water supply, 236 ; meteoric, 219- 
20; percolation, 223-4 ; percola- 
tion 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. 
PRINTED IN GREAT BRITAIN AT THE UNIVERSITY PRESS, ABERDEEN