Machine

(mah-sheen'.) Any contrivance for transmitting force from one point to another, or for increasing or regulating the effect of a given force. The simple machines are the lever, the wheel and axle, the pulley, the inclined plane, the screw, the wedge. Compound machines consist of combinations of these simple machines. They admit of infinite variations and adaptations, but there are certain laws found to apply to all machines. The work of a M. is measured by the amount of resistance overcome in a given time. An important empirical law, due to Euler, gives the relation which must subsist between the speed and the resistance in order that the effect maybe a maximum. The load or resistance should be about four - ninths of that which would exactly counteract the power or keep the M. at rest, and the velocity of the point or points of application of the power should be one-third of their greatest velocity. When these two conditions are fulfilled, the •M.will work to the greatest po ible advantage. Thus am ill will do the greatest amount of work in a given time when the wheel has one-third of its greatest po ible velocity, and overcomes a resistance equal to four ninths of the greatest resistance against which it can move; an animal will accomplish the greatest amount of work in a given time when it moves with one-third of its greatest speed, and is loaded with four-ninths of the greatest load it is capable of moving. Macintosh, (-in'tōsh,) in Georgia, a S.E. co., washed by the Atlantic Ocean; C. Darien. Pop. 4,491. MacKean, (-ken,) in Pennsylvania, a N.N.W.co.; area, 1,100 sq. m.; C. Smith port. Pop. 8,825. Mackenzie River, (-kěn'ze,) a large stream ofBrit. N. America. Its upper waters form the Athabasca, rising on the N.E. side of the Rocky Mts., in N. Lat. 520, W. Lon. 116° 30', and emptying into Athabasca Lake after af low of 800 m. The M., under the name of Slave River, flows thence as far as Great Slave Lake; then, under its own proper title, it makes a course generally N. and W. to its embouchure in Mackenzie Gulf, Arctic Ocean. Total length, abt. 2,500 m. It was discovered and navigated by, and named after one Alex. Mackenzie, a Scottish explorer, 1789. [s. 565]