PRIME-MOVER. A machine transforming c.pparent natural energy into visible work, and varied in form relatively to both. Ran himself is the highest prime-mover and standard of natural construction. Next are the animals, greater muscular example$, foreshadowing the division of the translators of energy into classes, relating more to the work to be performed than to the energy to be transformed. While prime-movers are parallel in many points to the machines which they drive, they are almost alone in requiring a construction adapted to the driving-power; demanding a distinct region of scientific principles, and thus a "science of power" or "first motion." Exhausting a visible energy, they demand an economy, in per cent of work, from each " destruction ;" thus, greater than machines, they become motors.
The sources of apparent energy in nature, made actual through prime-movers, are muscular energy, gravitation, and heat; the two latter respectively including falling water and atmospheric movements; electricity and magnetism. Although the heat mover, or steam-engine, holds the first place, yet it was preceded in history by the united force of animals directed by men upon various objects; and by the windmill—to the prairie what the water-wheel is to the river—the oldest mechanical survivor of antiquity, claiming to acid to the short list a fourth source of energy—horizontal velocity. After the windmill were the water-wheels, in many forms; then appeated the last of the "directly visible", powers; that prebeded the heat-engine—Barker's mill, a rude form, giving power and prophesying the turbine. This gave control of the force of gravity,
expressed in the vertical fall from level to level, of bodies of water; a force equivalent in foot-pounds to the product of the weight of the water multiplied by the feet of fall, equaling the energy increased continually to the point of shock on the water-wheel; where, intercepted in its force, it loses an energy equal to the work " attached " to the Wheel; thus with light work losing most of the, energy of the body of water. -Even m older than the wheel is the water-engine, a slow mover, in its construction forerunner of the steam-engine. The heat-engine, in the form of steam-engine used for propulsion, exerted an influence upon the stationary engine, that produced the turbine as a com petitor against the wheel, gown obsolete, and against the new power, threnening to take the place of the waterfall. In turn, as special purposes sought special prime-movers, appeared hot-air, gas, and electro-dynamic engines; restricted in their applications, but in those superior;,and again, in turn, we shall probably see electricity in various devel opments; then the applied force of the tides, great natural prime-movers, replacing the turbine in its first importance; then the sun's heat gathered and applied in tropical lands for the uses of a new civilization.