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LEFT FBICTION 221 FRENCH, SOCIETY OF lines, and the British attack was launched on both sides of the village. Gradually the Germans were nipped out of this strategic point and the village was taken on the following day by the British. HENRY C. FRICK FRICTION, the act of rubbing two bodies together, or rubbing one body on another; in physics, the resistance which any body meets with in moving over an- other body. No body is quite smooth; all have elevations and depressions, and when one moves over another some of the projecting points of the one are sure to enter the cavities of the other, and render movement more difficult. Fric- tion is grreater when a body, previously at rest, first begins to move. The larger and heavier the body, the greater the friction. Friction is a retarding force in nature. It gives stability to bodies which else would be easily moved. It generates heat, and is one of the chief means of developing electricity. Co-efficient of Friction for Two Sur- faces. — The ratio between the force re- quired to move one of these surfaces over the other, and the pressure between the two surfaces. FRICTION CLUTCH, in machinery, a device for connecting two shafts by bringing a piece on one shaft into con- tact with a piece of another shaft, which revolves with such force that the former partakes of the motion of the latter. It consists of a shell or box fixed on the cmd of a driving shaft, fitted by a conical Vol. IV — crc — piece which slides on a feather or raised part of the end of another shaft, so that it can be engaged at pleasure by the cone being forced into the shell by a lever or screw. This apparatus is very useful for driving machines, the parts of which are subject to violent strains, as the pressure upon the clutch can be regu- lated so as to allow it to slip when the strain is abnormal. FRICTION WHEEL, in machinery, a wheel, the motion of which is caused by the friction of a moving body, or, con- versely, whjch communicates motion to a body by frictional contact. In one variety, one wheel being driven becomes a motor to the other, their perimeters being in contact. The surface is usually clothed with leather, rubber, or some sufficiently elastic material which does not polish too readily, and thus induce slipping. By grooving the perimeters of the wheels, the contact may be made more intimate, as the surface engaged is increased, and the elastic material of the respective faces caused to bind. In an- other form a collar fastened to the cen- tral shaft has four pivoted arms. When the rim turns in one direction, the arms turn on their pivots, leaving the rim and failing to transfer the motion to the shaft. When the rim turns in the con- trary direction, the arms catch against it and are rotated by the contact, turn- ing the shaft also. Another form has an upper india-rubber wheel with V- edge, clamped between two metallic plates. By screwing up the nut which holds the parts together, the disk is made to expand radially, and thus in- crease the tractive power on the lower driving wheel. The term friction wheel is often, but erroneously, applied to wheels which diminish friction ; these are properly called anti-friction wheels. FRIENDLY ISLANDS. See TONGA. FRIENDLY SOCIETIES, societies formed with the view of assisting any one of their members who may be sick, infirm, or old, or who may have to meet the expense of a funeral in his family; or for providing a certain amount of support for his widow and family on his death. To obtain money for those objects, there is a fixed scale of contributions binding on all the members. Friendly societies existed among the Anglo- Saxons. An act for the encouragement of such institutions was passed by the English Parliament in 1793. See Frater- nal Societies. FRIENDS. SOCIETY OF. the organi- zation commonly called Quakers, founded in the middle of the 17th centurj^ by George Fox. They are distinguished from