tilising constituents in, 314;
fish, 320-323;
importance of, in agriculture, 293;
inequality in composition of, 309;
influence of, on farming, 294;
meat-meal, 324;
mode of application of, 315;
nitrification in, rate of, 192;
nitrogenous, 300-308;
origin of, 297;
Peruvian, 300-306;
phosphatic, 308;
quantity to apply, 317;
rectified, 311;
so-called, 320;
source of phosphoric acid, 202;
source of potash, 219;
value of, as a manure, 296;
variation in composition of, 299.

Gulf of Mexico, guano deposits at, 328.

Gulls, guano from, 297.

Gunning on sources of plant-nitrogen, 42.

Gunpowder, exports of, 149;
nitrogen lost in, 149;
production, annual, of, 149;
saltpetre in, 149, 333.

Gypsum, 462-464;
absorptive power of, 98;
action of, mode of, 462--on nitrification, 173;
an adulterant of guano, 319;
as a fixer, 246, 247, 285;
decomposes double silicates, 463;
favourable to clover, 464;
as an oxidising agent, 464.

Hales, Stephen, theory of, on plant-growth, 8.

Hampe, Dr, on nitrogen in plants, 46.

Harting on sources of plant-nitrogen, 42.

Heat, of soils, 76-78;
of fermentation, 78.

Heiden, Dr, on application of farmyard manure, 265;
on fixation of bases and acids by soil, 59;
on loss of ammonia from dung, 249;
on percentage of food voided by animals, 253;
on straw as litter, 244, 249.

Hellriegel, on amount of water in soils, 75;
on barley, 498;
on nitrogen in plants, 44.

Helmont, Van, theory of, on source of plant-food, 4.

Henslow, Professor, on coprolites, 374.

Heraues on organisms in soil, 95.

Herbage, effect of manure on, 505.

Herrings as manure, 321.

Herve-Mangon, experiments on action of light on plants by, 38.

Hilgenstock on tetracalcic phosphate, 405.

Hippuric acid, experiments with, 46;
in farmyard manure, 257.

Hire, De la, on evolution of gases by plants, 11.

Hofmeister on horse excrements, 243.

Hoof-guano, source of nitrogen, 152.

Hoofs and horns, manure from, 425.

Hops, manuring of, 528;
potash removed by, 217;
slow-acting manures benefit, 528.

Horn, capable of nitrification, 182;
as manure, 425;
nitrogen in, 426;
phosphoric acid in, 426.

Hornblende, 105.

Horse-dung, alkalies in, 226;
composition of, in dry state, 227;
hot, 225;
nitrogen in, 225, 226;
phosphoric acid in, 22