204

CHAPTER XI.

THE COMPOSITION AND PROPERTIES OF MINERAL
MANURES.

Mineral Manures ... Sulphate and Muriate of Ammonia ... Sulphomuriate
of Ammonia ... Ammoniacal Liquor ... Nitrates of Potash and Soda ...
Muriate and Sulphate of Potash ... Chloride of Sodium, or Common Salt
... Carbonates of Potash and Soda ... Silicates of Potash and Soda ...
Sulphate of Magnesia ... Phosphate of Lime ... Bone-ash ... Coprolites
... Apatite ... Sombrero Guano ... Superphosphates and Dissolved Bones
... Biphosphate of Lime or Soluble Phosphates ... Phospho-Peruvian Guano
... Lime ... Chalk ... Marl ... Application and Action of Lime on Soils
... Sulphate of Lime or Gypsum 226

CHAPTER XII.

THE VALUATION OF MANURES.

The Principle on which Manures are valued ... Its application to
different simple and complex Manures ... Method of Calculation ...
General Remarks 255

CHAPTER XIII.

THE ROTATION OF CROPS.

Its necessity explained ... Quantity of Mineral Matters in the produce
of an Acre of Different Crops ... The Theory of Rotation 266

CHAPTER XIV.

THE FEEDING OF FARM STOCK.

The Principles of Feeding ... The Composition of different Animals in
different stages of Fattening ... The Composition of the Food of Animals
... Milk ... The Principal Varieties of Cattle Food ... General
Observations on Feeding 276

AGRICULTURAL CHEMISTRY.

INTRODUCTION.

That the phenomena of vegetation are dependent on certain chemical
changes occurring in the plant, by which the various elements of its
food are elaborated and converted into vegetable matter, was very early
recognised by chemists; and long before the correct principles of that
science were established, Van Helmont maintained that plants derived
their nourishment from water, while Sir Kenelm Digby, Hook, Bradley, and
others, attributed an equally exclusive influence to air, and enlarged
on the practical importance of the conclusions to be deduced from their
views. These opinions, which were little better than hypotheses, and
founded on very imperfect chemical data, are mentioned by Jethro Tull,
the father of modern agriculture, only to deny their accuracy; and he
contended that the plants absorb and digest the finer particles of the
earth, and attribut