3. _Rent-bearers may be increased by inventions and improvements that make machines stronger, quicker, and better._ This proposition is not logically different from the preceding. A machine is an arrangement of material things through which force may be indirectly applied to move matter. No fast line divides machinery as regards form, purpose, or cause of value, from the artificially improved natural agents that we have been discussing. Just as a field is drained, plowed, and cultivated to fit it better to yield a crop, so is the iron ore shaped into a form called a machine, better fitted to cut, carve, and weave as man wills. Machines are merely adaptations of natural resources. [Sidenote: Bettering quality of agents] Increase in machinery may be either in quality or quantity. The two causes have in most cases the same result. If the quality or efficiency of looms is doubled, it is as if their number had grown in like proportion. In its economic function the beast of burden may not illogically be classed with inanimate machines. The horses in America have been remarkably improved of recent years by the importation of thoroughbred stock from Europe. Ten or fifteen years ago the number of horses in the United States was found to have decreased, and there was much comment on this evidence of a declining industry. It was not at once recognized that there was embodied in horse-flesh more horse-power than ever before, as a single Norman horse has the strength of several Mexican mustangs. Numbers alone are not the measure of efficiency. [Sidenote: Increasing number and better grouping of agents] 4. _The increase of wealth and the betterment of environment go on as well through the increase in the number of appliances and through their improved arrangement, as through changes in their kind._ A machine is an adjustment of various natural agents to each other so as to make a more efficient agent, and machines in turn may be adjusted as parts of a larger system of production. The ideal of the modern factory system is so to arrange the machinery that no bit of material will make an unnecessary motion. The log, once started through the mill, is carried automatically from one machine to another until it emerges as a roll of paper or as a box of tooth-picks, ready for use. In an American watch-factory one man tends twelve or fifteen automatic machines. A small brass rod is fed automatically to the machine; a piece is cut off, is picked up by a human-like metal hand; is put into a lathe, and shifted or held firmly while it goes through fifteen or twenty processes; and then is dropped into a box where it is ready for the "assembling" of the watch. As the machinery improves, factories making allied products are grouped to make a system still more efficient.