i. 267, 268

Hyponitrous acid, combination forming, i. 95

Hypopterygium Smithianum, leaves of, i. 330

I

Ice, absorption of invisible rays by, i. 65 believed to be a colloid body, i. 111

Iceland moss, characters of, i. 304

Iceland spar, polarization of light and heat in, by refraction, i. 69 change of position of the optical axes of the crystals of, by heat, i. 73

Ileodictyon, eaten as food, i. 268

Impetus, i. 26, 27 heat generated by, i. 27 combustion a case of, i. 30

Indian rubber, dissolved by naphtha for waterproofing, i. 120

Indium, discovery of the metal so called, i. 137 properties of, i. 137

Infusoria, structure, form, and habitat of, ii. 63 abundance of infusoria in the atmosphere, ii. 63, 64 different states of development in one and the same animal, ii. 65 groups of, of opposite characters in the same liquid, ii. 66 the agents in the decomposition of animal matter, ii. 67 minuteness of the ferments, ii. 68 cilia of Infusoria, ii. 68 as organs of locomotion, ii. 69 cell constituting the body of Infusoria, ii. 70 food and organs of digestion of, ii. 70 transparent contractile vesicles, ii. 71 modes of propagation, ii. 74 _et seq._ in a state analogous to hybernation, ii. 78, 79 functions assigned to Infusoria in the economy of nature, ii. 79

Insects, phosphorescence of, i. 167

Intelligence, or the mental principle, of animals, ii. 11, 12

Iodine, i. 18, 21 whence obtained, i. 19 properties of, i. 21, 22 spectrum of, i. 21 atomic weight of, compared with that of hydrogen, i. 100 preparation of, from sea-weeds, i. 128 spectrum analysis of, i. 140, 141 iodine richer at Guernsey than elsewhere, i. 258

Iris germanica, vertical section showing the cellular tissue of, i. 173

Iron heated by percussion or impetus, i. 27 effect of electricity on, i. 32 effect of magnetism of, i. 75, 76, 77 and of heat on the magnetism of, i. 77 feeble affinity of iron for mercury, i. 98 atomic weight of, compared with that of hydrogen, i. 100 spectrum analysis of the rarefied vapour of, i. 142

Isaria, its structure and habitat, i. 282 its destruction of caterpillars, i. 282, 293

Isaria crassa, characters of, i. 283

Isaria farinosa, characters of, i. 283

Isariacei, structure and habitat of, i. 282

Isidæ, structure, habitat, and mode of reproduction of, ii. 125

Isis, structure of the genus, ii. 125

Isomeric substances, i. 104 law of the sequence of three isomeric bodies, and their respective atomic numbers, i. 105

Isomorphism, property of, in determining atomic weights, i. 99

Isomorphous substances, conduct of, under magnetic influence, i. 76

Isopoda, characters of the order, ii. 202

J

Jam, greenish, and grey moulds on, i. 285

Jungermanniaceæ, or scale mosses, structure, fertilization, and development of, i. 320-322

Jupiter, the planet, spectrum of, i. 157, 161 constitution of, i. 158

K

Katsup made from the morel, i. 292

Kelp, i. 258 former and present uses of, i. 128

Kerona silurus, structure and food of, ii. 69

L

Labellum of orchids, i. 401

Lactarii, laticiferous vessels of, i. 263

Lady Fern, herbaceous caudex of, i. 340 structure and fructification of, i. 352, 353

Lagenidæ, characters and habitat of the family, ii. 39

Lagoons formed by corals, ii. 140-143

Laminaria bulbosa, structure and fruit of, i. 248

Laminaria debilis, structure of, i. 248

Laminaria digitata, or oar-weed, structure of, i. 249 richness of the iodine obtained from, at Guernsey, i. 258

Laminaria radiata, structure, habitat, and fructification of, i. 250

Laminaria saccharina, or devil’s apron, structure and mode of reproduction of, i. 249

Laminariæ, submarine forests of, i. 248

Lanosa nivalis, the probable cause of the mildew in rye, i. 297

Lastrea, structure of the genus, i. 346

Lastrea æmula, structure of, i. 346

Lastrea filix-mas, structure of, i. 340

Lastrea rigida, scent of, i. 347

Lastrea Thelypteris or marsh fern, structure of, i. 346

Latex, structure of the, in plants, i. 417

Laughing-gas, or protoxide of nitrogen, combination forming, i. 95

Laurel, oil of, amount of radiant heat absorbed by the perfume of, i. 44

Laurencia dasyphylla, antheridia of, i. 241

Laurencia pinnatifida, or pepper dulse, structure, habitat, and mode of propagation of, i. 241

Laurencia tenuissima, antheridia of, i. 241

Laurenciaceæ, characters of, i. 240, 241

Laurentian system, ancient formation of the crystallized limestone near the base of the, ii. 54

Lavender, absorption of radiant heat by the perfume of, i. 44

Lead, its resistance to electricity, i. 90 chloride of, spectrum of, i. 146

Leathesia, structure of, i. 245

Leaves of plants, structure and functions of, i. 410

Lecanora affinis, section of, i. 300 structure and habitat of, i. 305

Lecanora esculenta, habitat of, i. 305

Lecidea, characters of the genus, i. 306

Lecidea geographica, great age of, i. 306

Lecidinei, characters of the order, i. 306

Leeches, structure of, ii. 149-151

Lemon, amount of radiant heat absorbed by the perfume of, i. 44

Lepadidæ, structure of, ii. 213, 215

Lepas anatifera, structure and mode of reproduction of, ii. 215

Lepidodendron, structure of the fossil, i. 375

Lepidostrobus ornatus, structure of, i. 375

Lepraliæ, structure of, ii. 219

Leptopteris, characters of, i. 364

Lessonia, arborescent, forests of, i. 251

Lessonia nigrescens, structure of, i. 251 rings of growth of, i. 252

Leucobryum, structure of, i. 329

Leucobryum glaucum, leaves of, i. 330

Leveillea, structure of, i. 242

Libanea crab, a parasite of the medusæ, ii. 100

Lichens, characters and habitat of, i. 298 two groups of—Gymnocarpei and Angiocarpei, i. 299 horizontal lichens, i. 299 gonidia, i. 300 asci, i. 301 thallus or frond, i. 301 dyes obtained from, i. 124, 303 brilliancy of the colours of, i. 304

Lichina, characters of the genus, i. 310

Lichinei, characters of the group, i. 310

Life, the mystery of, i. 97 instances of individual combined with a common life in the lower orders of animals, ii. 38

Light, probable cause of the, of the sun, i. 28 Drummond’s light, how produced, i. 30 intensity of the, of the electric spark, i. 32 chemical action of, i. 34 amount of force exerted by the sun’s light within the limits of the terrestrial atmosphere, i. 34 constancy of the amount and refrangibility of light and heat absorbed and radiated, i. 34 causes of colour of flowers, leaves, dyed cloth, and gold and copper,