guanite, 236.

Quartz, 86.

Rainwater, 17, 18.

Rape Cake, 196, 286.
Dust, 195.

Rocks, crystalline, 85.
Composition of, 91.
Disintegration of, 85.
Sedimentary, 86.

Roots of plants, amount of ash in, 65.

Rotation of crops, 81, 266.

Ruebsen cake, 286.

Rye, 286.

Saccharine Constituents of plants, 40.

Saldanha Bay guano, 207.

Salt, common, 232.

Sandstones, 95.

Schuebler's experiments, 127.

Sea Bear Bay guano, 208.

Sea weed, 200, 201.

Seeds, amount of ash in, 64.

Sesamum cake, 286.

Sewage manure, 191.

Shell sand, 246.

Silica plants, 82.

Silicate of potash, 233.
Soda, 233.

Skin, 218.

Soda, carbonate of, 232.
Nitrate of, 229, 260.
Salts, 231.
Silicate of, 233.

Sodium, chloride of, 232.

Soil, the, 20, 83.
Influence on the composition of the ash of plants, 71.
Chemical composition of, 98.
Chemical and physical characters of, 83.
Improvement of, by mechanical means, 137.

Soil, relation of, to heat and moisture, 127.

Soils, absorbent action of, 122.
Air in the pores of, 114.
Analysis, 101, 118.
Barrenness of, 109.
Classification of, 135.
Exhaustion of, 81.
Inorganic constituents of, 85.
Mixing of, 150.
Origin of, 84.
Organic matters in, 103.
Physical characters of, 118, 127.

Sombrero Island guano, 236.

Starch, 41.
Lichen, 42.

Stearic acid, 47.

Stearine, 46.

Stems of plants, ash in, 64.

Straw, amount of ash in, 64.
As a manure, 197.

Sulphate of iron, 182.
Lime, 96, 253, 260.
Magnesia, 182.
Ammonia, 29, 227.
Potash, 231.

Sulphomuriate of ammonia, 227.

Sulphur in plants, 78.

Sulphuret of iron, 135.
Calcium, 252.

Sulphuretted hydrogen, 19.

Sugar, 43.
Of milk, 283.

Subsoil, the, 134.
Ploughing, 143.

Sunflower cake, 286.

Syenite, 91.

Tares, 286.

Teelcake, 286.

Temperature, influence of, on germination, 54.

Thomsonite, 90.

Trap rock, 92.

Tubers, amount of ash in, 65.

Ulmic acid, 21.

Ulmin, 22.

Upper Peruvian guano, 207, 213.

Urate, 216.
Of ammonia, 205.

Urea, 168.

Uric acid, 168, 205.

Urine, composition of, 167.
Human, 168.
Sulphated, 216.

Valuation of manures, 255.

Vegetable manures, 195.

Vegetation, influence of light on, 57.

Voelcker's analyses of dung, 174.

Warping, 148.

Water, absorption of, by plants, 35.
Decomposition of, by plants, 60.
Exhalation of, by plants, 35.