st in, 149;
purified by soils, 435;
treatment of, by precipitation, 436;
value of, as a manure, 430.

Sewage-sick land, 433.

Sewage-sludge, 438-441;
as a manure, experiments with, 438;
nitrogen in, 439;
phosphoric acid in, 439;
profitable treatment of, 441;
value of, 439;
water in, 438.

Shale-works, sulphate of ammonia, from, 358.

Shark's Bay guano, 309, 328.

Sheep, excrements of, 280, 281;
solid excreta voided by, 280;
urine voided by, 280.

Sheep-dung, alkalies in, 226;
composition of, in dry state, 227;
most valuable excrement, 227;
nitrogen in, 226;
phosphoric acid in, 226;
water in, 226.

Sheep-manure, 251;
amount produced per day, 251
--per year, 252;
dry matter in, 252;
mineral matter in, 252;
nitrogen in, 252.

Sheep-urine, alkalies in, 230;
composition of, in dry state, 231;
most valuable urine, 231;
nitrogen in, 230;
phosphoric acid in, 230;
water in, 230.

Shoddy, 427;
production of, 152, 425;
nitrogen in, 152, 427.

Sicily, bones from, 360.

Sidney Island guano, phosphoric acid in, 330.

Siemens, Dr, experiments by, with light on plants, 38.

Silica, in ash of plants, 55;
in Chincha guano, 305;
jelly, 169;
necessary for plant-growth, 55.

Silicates, 102;
absorbed by cereals, 494.

Silicic acid fixed by soils, 58.

Simon on humus in soil, 47.

Slaked lime, 454.

Slugs killed by lime, 461.

Smut prevented by lime, 461.

Soda, in ash of plants, 54;
fixed by soils, 58;
necessary for plant-growth, 55;
nitrate of, 332-351;
in _salinas_, 335;
replaces potash, 466.

Sodium chloride in Chincha Island guano, 305.

Sodium phosphate in concretionary nodules, 328.

Sodium sulphate in concretionary nodules, 328.

Soil, 65-108;
absorptive power of, for water, 67, 98;
acids fixed by, 58-60;
action of lime on, 453;
ammonia absorbed by, 81;
amount of soluble plant-food in, 100;
artificial, 54;
barley, nitrates in, 158;
bases fixed by, 58-60;
best suited for nitrification, 192;
biological properties of, 92-96;
capacity for heat, 76-78;
carbonic acid absorbed by, 81;
chemical composition of, 87-92, 101-107;
colour of, 80;
cropped, nitrates in, 157;
denitrification in, 177;
evaporation from, 71, 72;
farmyard manure, action of, on, 272;
fertilising ingredients in, 87;