Chapter III: Introduction

The scientific principles upon which the art of culture depends, have not hitherto been sufficiently understood or appreciated by practical men. Into the causes of this I shall not here inquire. I may remark, however, that if Agriculture is ever to be brought to that comparative state of perfection to which many other arts have already attained, it will only be by availing itself, as they have done, of the many aids which Science offers to it; and that, if the practical man is ever to realize upon his farm all the advantages which Science is capable of placing within his reach, it will only be when he has become so far acquainted with the connection that exists between the art by which he lives and the sciences, especially of Chemistry and Geology, as to be prepared to listen with candour to the suggestions they are ready to make to him, and to attach their proper value to the explanations of his various processes which they are capable of affording.

The following little Treatise is intended to present a familiar outline of the subjects of _Agricultural Chemistry and Geology_, as treated of more at large in my LECTURES, of which the first Part is now before the public. What in this work has necessarily been taken for granted, or briefly noticed, is in the LECTURES examined, discussed, or more fully detailed.

_Durham, 8th April, 1842._

CONTENTS.

CHAPTER I.
PAGE
Distinction between Organic and Inorganic Substances
—The Ash of Plants—Constitution of the Organic
Parts of Plants—Preparation and Properties of
Carbon, Oxygen, Hydrogen, and Nitrogen—Meaning
of Chemical Combination. 13

CHAPTER II.

Form in which these different Substances enter into
Plants—Properties of the Carbonic, Humic, and
Ulmic Acids; of Water, of Ammonia, and of Nitric
Acid—Constitution of the Atmosphere. 25

CHAPTER III.

Structure of Plants—Mode in which their Nourishment
is obtained—Growth and Substance of Plants—
Production of their Substance from the Food they
imbibe—Mutual Transformations of Starch, Sugar,
and Woody Fibre. 38

CHAPTER IV.

Of the Inorganic Constituents of Plants—Their
immediate Source—Their Nature—Quantity of each
in certain common Crops. 49

CHAPTER V.

Of Soils—Their Organic and Inorganic Portions—Saline
Matter in Soils—Examination and Classification of
Soils—Diversities of Soils and Subsoils. 67

CHAPTER VI.

Direct Relations of Geology to Agriculture—Origin
of Soils—Causes of their Diversity—Relation to
the Rocks on which they rest—Constancy in the
Relative Position and Character of the Stratified
Rocks—Relation of this Fact to Practical
Agriculture—General Characters of the Soils upon
these Rocks. 78

CHAPTER VII.

Soils of the Granitic and Trap Rocks—Accumulations
of Transported Sands, Gravels, and Clays—Use
of Geological Maps in reference to
Agriculture—Physical Characters and Chemical
Constitution of Soils—Relation between the Nature
of the Soil and the Kind of Plants that naturally
grow upon it. 103

CHAPTER VIII.

Of the Improvement of the Soil—Mechanical and Chemical
Methods—Draining—Subsoiling—Ploughing, and Mixing
of Soils—Use of Lime, Marl, and Shell-sand—
Manures—Vegetable, Animal, and Mineral Manures. 133

CHAPTER IX.

Animal Manures—Their Relative Value and Mode of
Action—Difference between Animal and Vegetable
Manures—Cause of this Difference—Mineral Manures—
Nitrates of Potash and Soda—Sulphate of Soda,
Gypsum, Chalk, and Quicklime—Chemical Action of
these Manures—Artificial Manures—Burning and
Irrigation of the Soil—Planting and Laying Down
to Grass. 165

CHAPTER X.

The Products of Vegetation—Importance of _Chemical_
quality as well as quantity of Produce—Influence
of different Manures on the quantity and quality
of the Crop—Influence of the Time of Cutting—
Absolute quantity of Food yielded by different Crops
—Principles on which the Feeding of Animals depends
—Theoretical and Experimental Value of different kinds
of Food for Feeding Stock—Concluding Observations. 216

ELEMENTS
OF
AGRICULTURAL CHEMISTRY, &c.