s, as pumping-engines, 76;
water transpired by, 71.

Tricalcic phosphate, 386, 398.

Tubercles on roots of plants, 44.

Tull, Jethro, theory of, on plant-growth, 9-11, 69, 109.

Turkey, dung produced by, 331.

Turnips, fertilising ingredients removed from soil by, 485;
manurial constituents in, 282;
manuring of, 510, 511, 513-517;
Rothamsted experiments on growth of, 568.

Twigs, potash in, 217.

Tyrosin, assimilated by plants, 47.

Ulmates in farmyard manure, 259.

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

Ulmin in humus, 47.

Uncovered farmyard manure, 263, 289.

Unexhausted manures, valuation of, 549-552, 558.

Unit value of manurial ingredients, 544.

Units for determining commercial value of manures, 554.

Urate of ammonium in Chincha Island guano, 305.

Urea, assimilated by plants, 46;
in farmyard manure, 257;
nitrification in, 182.

Uric acid, experiments with, 46;
in Chincha Island guano, 305.

Urine, 228;
amount voided, 291;
composition of, varies, 228;
contains digested manurial ingredients, 228, 232;
devoid of phosphoric acid, 205;
and dung, composition of, 234;
influence of food on, 229;
nitrification in, 197;
nitrogen in, 292;
potash in, 292;
voided by cows, 280;
voided by oxen, 280;
voided by pigs, 281;
voided by sheep, 280.

Uruguay, meat-meal guano from, 324.

Valuation of manures, 539-559.

Vegetation, desirable to have soil covered with, 194.

Venezuela, guano deposits at, 327.

Ville, Georges, on assimilation of ammonia, 50;
theory of, on source of plant-nitrogen, 41.

Vine, potash removed by, 216.

Virgin soils, 133.

Voelcker, Dr, analysis of apatite, 210
--of farmyard manure, 259;
on action of superphosphate, 395;
on fresh and rotted dung, 261, 286;
on guano, 316;
on salt as a manure, 473.

Voss, Hermann, on manures used, 152.

Wagner, Professor, on, application of basic slag, 416;
assimilation of organic nitrogen, 46;
experiments with basic slag, 408-413;
fineness of basic slag, 409;
manures, 412;
relative manurial value of nitrogen compounds, 556;
solubility of basic slag, 408.

Wallace, Dr, on sewage purification, 436.

Walruses, guano from, 297.

Warington, R,., on ammonia in rain, 49;
on appearance of nitrous organisms, 168;
on conditions favourable for nitrification, 181;
experi