308 THE ELEMENTS OF ECONOMIC GEOLOGY

168; industrial value of, 168.
China clay, 169-73 ; pneumato.
Iytic origin’ of, 169 ; price, 173 ;
some due to descending solutions,
172-3. Pottery clays, 169. Fire
clay, 169,
Coal and its classification, 259-72
annual output of, 272; anthra
cite, 261, 264-5, 268, 271-2; arti
ficial coal and its evidence, 271
black or bituminous coal 261,
263-4, 271; calorific value from
analysis, 259; cannel, 265-6;
chemical classification, 267-8 ;
coking, cause of, 264 ; coking
index, 264 ; constitution of, 260 -
definition of, 260 ; graphite, 265
humic, 260-5 ; lignite or brown.
261, 262-3; origin of, 267, 268
70; peat, 261 ; resources, 272-4 ;
sapropelic coals, 260, 261, 263-6,
294; seams, carbon enrichment
in, 270-1; ‘wood, composition,
201.
Coast defence, 245-8 ; beach mate
rial, transport of, 241; broads
formation of, 245; coastal ac.
cretion, 242-4; continental shelf,
241; estuary works and models,
248; estuaries, silting of, 244 i
groynes, 246; marine abrasion,
rate of, 241, 242 ; planting, 245 ;
recession of the land, 240; seawalls,
 247 ; silt jetties, 245 ; spit
formation, 243 ; ‘subaerial erosion
242 ; warping, 244. Waves, 238-40;
 depth of, 239 ; force of, 240;
height and fetch, 239-40.
Cobalt, 5, 110-12,
Colours of gold, 5.
Contact ores, 85, 102, 132.
Contra-lodes, g.
Copper, price, 80, 81; qualities of,
80; British yield of, 80 ; ores of,
80-95; bedded or sedimentary,
93-5; Classification of, 81-2:
contact, 85; Cornish lodes, 84
dissemination ores, 85 ; distribu:
tion of, 81; lodes, 21, 29; pipe
lodes, 85; pneumatolytic lodes,
82-4 ; primary lodes, 81, 82-90:
pyritic masses, 86-go, 134; re

placements, 85-90, 94; secon:
dary ores, go-3; secondary enrichments,
 84, 90-2; in volcanic
rocks, 83-4, 94.
Coprolites, 203.
Corundum group, 165-7.
Costeaning, 6.
Country, term defined, 7.
Cross-course lodes, 9, 100.
Crustified lodes, 11, gg.

DEEP leads, 53-7.
Depth of ore formation, 28, 36, 38
42, 43, 45, 63, 70, 73, 83, 84, 95
97, 100, 102, 105, 112, 124, 126.
127, 137.
Diamond, the, 161-5 ; distribution,
161-3; formation of, 163-4;
kimberlite, 162 ; mineral association,
 162; penumatolytic, 162,
164 ; production, 162; theories
of formation based on alleged
artificial diamonds, 164.
Dredging, 53-4.
Dumb-wells, 22g.

EARTH, structure of, 16.
Earthquakes and anti-earthquake
construction, 248-58; action,
nature of, 249; anti-earthquake
construction, 253-8; anti-earthquake
 building design, 254-7 ;
submarine cables broken by earth
slips, 251; causes of earthquakes,
251; depth of, 250; determination
 of origin, 249-50; economic
seismology, 252-8 ; epicentrum,
249; foundations, loose #. firm,
254-5; homoseists, 249; isoseists,
 249; landslips, 251; lateral
 movement, effects of, 255;
level of greatest damage, 257 ;
prediction of and its value, 252 ;
probability, 252; source and
cause, 251; suitability of materials,
 257-8; Tokyo, of 1923, 253.
Efflorescent minerals, 30; iron
ores, 147.
Emborroscado, 28.
Emerald, 166 ; ural emerald, 167.
Engineering geology, 219-58.