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. CHAPTER I. Distinction between Organic and Inorganic Substances.—The Ash of Plants.—Constitution of the Organic Parts of Plants.—Preparation and Properties of Carbon, Hydrogen, and Nitrogen.—Meaning of Chemical Combination. The object of the practical farmer is to raise from a given extent of land the largest quantity of the most valuable produce at the least cost, and with the least permanent injury to the soil. The sciences either of chemistry or geology throw light on every step he takes or ought to take, in order to effect this main object. SECTION I.—OF THE VEGETABLE AND EARTHY OR THE ORGANIC AND INORGANIC PARTS OF PLANTS.