1690. Mechanical agents furnish the means by which art is applied in the practice of cultivation. In general it may be observed, that every change effected in the circumstances of materials either consists in, or must be preceded by, a mechanical change in their position. To effect mechanical changes, the fundamental engine is the human frame; but its agency is essentially increased by the use of certain implements, utensils, machines, and buildings. The primary implements of gardening, as an art of culture, would necessarily be confined to a few tools for stirring the ground, and one or two instruments for pruning trees or gathering crops. But in the present state of the art, both the number and kind of agents are greatly extended and diversified. There are tools, instruments, and machines for culture, as the spade, knife, and water-engine; for beautifying scenery, as the broom, scythe, and roller; utensils for portable habitations of plants, or conveying materials, as pots and baskets; structures for culture, as glass frames, hothouses, and awnings; and buildings for use, convenience, or decoration, as tool-houses, arbours, and obelisks. The whole may be included under implements, structures, and edifices, as in the following Table: �
