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; sea- 
walls, 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 en- 
richments, 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 associa- 
tion, 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-earth- 
quake building design, 254-7 ; 
submarine cables broken by earth 
slips, 251; causes of earthquakes, 
251; depth of, 250; determina- 
tion of origin, 249-50; economic 
seismology, 252-8 ; epicentrum, 
249; foundations, loose #. firm, 
254-5; homoseists, 249; iso- 
seists, 249; landslips, 251; la- 
teral movement, effects of, 255; 
level of greatest damage, 257 ; 
prediction of and its value, 252 ; 
probability, 252; source and 
cause, 251; suitability of mate- 
rials, 257-8; Tokyo, of 1923, 253. 
Efflorescent minerals, 30; iron 
ores, 147. 
Emborroscado, 28. 
Emerald, 166 ; ural emerald, 167. 
Engineering geology, 219-58.