6;
water in, 225, 226.

Horse-manure, 242;
amount produced per day, 243;
amount produced per year, 243;
analyses of, 283;
dry matter in, 243;
dry nature of, 245;
fermentation rapid in, 245;
mineral matter in, 243;
nitrogen in, 243, 244.

Horse-urine, alkalies in, 230;
composition of, in dry state, 231;
fertilising ingredients in, 232;
nitrogen in, 230;
phosphoric acid in, 230;
water in, 230.

Hosaeus on assimilation of ammonia, 50.

Howland Island guano. 309, 328;
phosphoric acid in, 330.

Huanillos, guano from, 302, 327;
nitrogen in, 330;
phosphoric acid in, 330.

Huano, 297.

Hueppe on organisms in soil, 95.

Hughes, John, on bracken-fern as litter, 241;
on composition of bracken, 283.

Humates in farmyard manure, 259.

Humboldt, A., discovery of Peruvian guano by, 300.

Humic acid in farmyard manure, 258;
in humus, 47.

Humin in humus, 47.

Humus, absorptive power of, 68, 98;
evaporation from, 99;
nature of, in soil, 47;
soils improved by addition of, 273.

Huon Island guano, 309, 328;
phosphoric acid in, 330.

Huxtable and Thompson on retention of plant-food by soil, 57.

Hydrated silicates, 107, 459.

Hydrochloric acid as a fixer, 245.

Hydrogen, amount of, in plants, 40;
source of, in plants, 40.

Hygroscopic power of soils, 75.

Ichaboe guano, 307;
nitrogen in, 329;
phosphoric acid in, 329.

Independence Bay guano, 302, 327;
nitrogen in, 329;
phosphoric acid in, 329.

India, nitre soils of, 162.

Indirect manures, 113, 114, 449-473.

Ingenhousz, John, experiments by, on nitrogen in plants, 41;
on oxygen evolved by plants, 12.

Insoluble phosphate, 386;
value of, 396.

Iodine, in ash of plants, 55;
in nitrate of soda, 340, 342.

Iquique, nitrate of soda from, 333.

Iron in ash of plants, 54;
necessary for plant-growth, 55;
reversion in superphosphates caused by, 390, 399.

Iron-works, ammonia from, 353, 355, 358.

Irrigation, 431-433;
intermittent, 434;
subsoil, 432.

Jamieson, Professor, experiments with coprolites, 380.

Jarvis Island guano, 309, 328;
phosphoric acid in, 330.

Jersey, manuring of potatoes in, 521.

Johnson, Professor S. W., on application of superphosphate, 395;
on Earl Dundonald, 13;
on nitrogen in buffalo-horn shavings, 426;
on nitrogen in soils, 123;
on solubility of