It will be noted that the gross receipts, the expenses, the farm income and the labor income on these actual farms are all more closely related to the capital invested than the size of the farm. Thus, on the 30 farms with a capitalization of about $13,500, the average yearly receipts were about $25 an acre, while on the 28 farms with a capitalization of about $8,300, the average yearly receipts were about $16 an acre. Likewise on the high-priced farms the labor income was approximately $10 an acre, while on the lower priced ones it was about $7. ----- [B] Obtained by dividing by two the sum of capital at beginning and end of three-year period. [C] For further details see Hunt, "How to Choose a Farm," Chaps. X and XI. CHAPTER XII GRAIN AND HAY FARMING An important and primary factor in the production of all wealth is labor. Aside from the professional and domestic classes, the people of the world devote themselves to three forms of work: (1) Changes in substance, or natural products; (2) changes in form, or mechanical products; (3) changes in place, or exchange of products. The second of these forms of work gives rise to manufacturing; the third, to trade and commerce. Under the first sub-division two classes of natural products may be recognized; first, what, for want of a better name, may be called chemical products, such as ores, coal and salt, from which are derived mining and the metallurgical arts; and second, vital products, or, in other words, vegetation and animals. It is work applied to the production of vegetation and animals that gives rise to agriculture. Agriculture is labor applied to the production of living things. KINDS OF AGRICULTURE The industries which deal with the production of living things may be divided, theoretically, largely on the basis of the character of the results, but to some extent upon the nature of the activities involved. { Grain Farming--Cereals and } { grasses. } { } Agriculture { Plantations--Cotton, sugar, } { tobacco, coffee. } Plant Production { (Soil Culture) { Truck Farming, Market } { Gardening--Vegetables. } { } Horticulture { Fruit Growing--Fruits. } { } { Forestry--Trees, shrubs. }