Cloud, force of the chemical combination requisite to form a, i. 98 Cloves, oil of, amount of radiant heat absorbed by the perfume of, i. 44 Club mosses. _See_ Lycopodiaceæ Coal, i. 13 effect of the consumption of a pound of, in a steam-engine, i. 29, 30 energy in abeyance in the coal existing in the whole globe, i. 30 Coal gas, i. 117, 118 poisonous quality of, i. 118 explosive quality of, i. 118 impurities from which it is freed, i. 118 uses of the black fœtid gas water resulting from the distillation of coals, i. 119 Coal tar, i. 120 substances produced from, by distillation, i. 120 colours, i. 121, 122 Cobalt, i. 4, 5 crystals of, formed artificially by electricity, i. 74 effect of heat in the magnetism of, i. 77 Coccocarpei, characters of, i. 307 Coccocarpia smaragdina, section of, i. 300 Coccospheres, found at a vast depth in the ocean, ii. 51 Cockle, structure and mode of life of the, ii. 230, 231 Codium, structure and habitat of, i. 219-224 Codium Bursa, structure of, i. 224 Codium tomentosum, structure of, i. 214 Coffee, active principle of, i. 428 Cohesion, properties of, i. 25 in solids, i. 25 in liquids, i. 25 Cohesion: reciprocal attractions between solids and liquids, i. 25 instance of the power of the cohesive force, i. 91 Colchicum, or meadow saffron, mode of reproduction of, i. 388 poisonous alkaloid obtained from, i. 427 Collemacei, structure and habitat of, i. 307 Colloid bodies, i. 109, 110 less diffusible than crystalloids, i. 109 permeable to solutions of crystalloids, but impermeable to solutions of colloids, i. 110 characteristics of colloids, i. 111 Collomia grandiflora, fructification of, i. 380 Colocasia, water secreted by, i. 430 Colour, causes of, in flowers, green leaves, dyed cloth, gold, and copper, i. 35, 36 Colouring matter of flowers and plants, i. 428, 429 Comatula, structure of, ii. 175, 176 Combination, chemical, i. 94 the law of definite proportions, i. 94, 95 force of, i. 97, 98 Combustion, effect of, in the consumption of coal in the steam-engine, i. 29, 30 combustion a case of impetus, i. 30 Comets, spectra of, i. 159 _note_, 163 Conferva glomerata, development of, i. 207 Confervaceæ, habitat of, i. 206, 207 structure and development of, i. 207 reproduction of, i. 208 modes of action of the vital forces of, i. 210 Confervæ, cells and development of, i. 171 Confervæ, marine, structure, habitat, and reproduction of, i. 221, 222. Conidium, or spore-dust cell, of fungi, i. 279 Coniomycetes, characters of the family of, i. 275 Conjugatæ, structure of the genus, i. 216 Conjugation, propagation of diatoms by, i. 200, 204 Constantinea rosa marina, i. 235 Constantinea sitchensis, i. 235 Copepoda, characters of the, ii. 204