435.

Rye-straw, summer, composition of, 238;
winter, composition-of, 238.

St Helena, experiments at, with Peruvian guano, 301.

Saldanha Bay guano, 328;
nitrogen in, 329;
phosphoric acid in, 329.

_Salinas_, 335.

Salm-Horstmar, Prince, on water-culture, 54.

Salt, 465-473;
action of, on crops, 472;
adulterant of guano, 319;
amount applied, 473;
antiquity of use of, 465;
an antiseptic, 468;
application of, 472;
clarifies water, 470;
coagulates clay, 470;
decomposes minerals, 470;
a germicide, 468;
indirect action of, 468;
mechanical action of, 470;
nature of action of, 465;
not a necessary plant-food, 466;
occurrence of, 467;
prevents rapid fermentation, 471;
quantity to apply, 473;
solvent action of, 470;
sources of, 468.

Saltpetre, formation of, 164;
occurrence of, 215;
plantations, 163.

Sand, absorptive power of, 68;
an adulterant of guano, 319;
calcareous, absorptive power of, 98;
siliceous, absorptive power of, 98.

Sandy soils deficient in lime, 451.

Sandwich Islands, guano deposits at, 328.

Saragossa Sea, sea-weed in, 339.

Saussure, De, on absorption of gases by soil, 81;
on nitrogen in plants, 41;
researches on plant-food by, 15.

Sawdust an adulterant of guano, 319.

Scheibler, Professor, on basic slag, 404.

Schloesing and Muentz, on nitrification, 51, 166;
experiments on rate of nitrification by, 185;
on denitrification, 179;
on ferments effecting nitrification, 167;
on fixation of free nitrogen, 42;
on ammonia in air, 119, 132;
on nitrogen absorbed by soil from air, 132;
on temperature favourable for nitrification, 175.

Schoenite, potash in, 220.

Schuebler, on absorptive power of soils, 98;
on retentive power of soils, 98.

Schulze on fixers, 246.

Scutch, 427;
manufacture of, 427;
nitrogen in, 427.

Sea-weed, nitric acid in, 339.

Seals, guano from, 297.

Seed, fertilising ingredients lodge in, 491.

Seine, nitrates in waters of, 158.

Senebier, Jean, on carbon in plants, 12;
on nitrogen in plants, 41.

Sewage, 430-441;
charcoal a filter for, 437;
crops suited for, 434;
denitrification in, 179;
dry matter in, 431;
effects of continued applications of, 433;
filters for, 437;
irrigation with, 431-433;
nitrification in, 166;
nitrogen lost in, 149;
phosphoric acid lo