Calamite, 47 Calcium, 13 Cambrian system, 32 Carbon, 11 Carbonate of lime, 15 Carbonate of magnesia, 19 Carbonic acid a cause of disintegration of rocks, 95 Carboniferous formation, 39 essential to national wealth, 43 extent of, 47 a prospective arrangement, 43 faults in, 41 not always disturbed by faults, 42 Carboniferous limestone, 39 sometimes becomes a coal-bearing rock, 42 fossils of the, 40 Carnelian, 14 Cause of internal heat, 128 Cause of stratification, 114 Caverns, 69 Cephalaspis, 39 Cephalopoda, 36 in oölite, 50 Chalcedony, 14 Chalk, 52 Changes of climate, 88 how produced, 146 Changes in the crust of the earth, 67 of temperature a disintegrating agent, 96 at the surface, 85 Chemical action, 97 in solids, 99 in crystallization, 97 Chlorine, 12 Chlorite, 15 Chlorite slate, 32 Classification of rocks, 21 Clay, 19 Clay slate, 20 Cleavage structure, 68, 98 Coal, 16 varieties of, 42 mode of quarrying, 42 origin of, 116 conversion of vegetable matter into, 117 now forming, 118