Electric motors driven from a dynamo, battery, or accumulator.
Magnetic power cannot be employed continuously as a motor, as it gives out only as much as it receives.
Tidal motion can be utilised to drive any kind of wheel, see Water Wheels, [Section 90]. It can also be stored in a reservoir, driving a water engine as it flows in and out on the flood and ebb; or a floating vessel may, by its rise and fall, communicate motion to machines.
Falling water; for machines employed to utilise, see Water Wheels, [Section 90]; Turbines, Water-pressure Engines, &c., [Section 93].
Descending weights must first of course be raised, absorbing as much power in raising as they give out in falling, neglecting friction. Clockwork; water; or compression of a spring (see [Section 80]); multiplying pulleys (see [Section 42]), are the apparatus employed to utilise this form of energy.
Wave motion is too uncertain and erratic to be a practicable source of power. Rocking air-compressing chambers, rocking pumps, &c., have obtained some small measure of success.
Wind, windmills. See [Section 95].
Expansion of air and gases. Ascending currents of hot air from a fire are used to drive a light screw motor, fan, &c. Hot-air engines, see Ryder’s patent and numerous others, which depend upon alternate expansion and contraction of air by heating and cooling. Air compressed in an accumulator or reservoir is employed to give motion to multiplying pulleys or an air engine.
Expansion of liquids, other than water (by heat), into the gaseous form. Engines in which the fuel is burnt under pressure and the total products of combustion employed (with or without steam) to drive a motor.
Steam is in reality one of the last-mentioned sources of power; it is employed by direct pressure on a piston or ram (see [Section 32]); or to produce direct rotary motion (see [Section 75]); also in the jet pump, [No. 801]; or injector (see [Section 45]); or by direct pressure on a body of water contained in a closed vessel, as in the pulsometer, steam accumulator, &c.