Athenian cultural dominance continued throughout the Roman period, and the buildings added to the Agora reflect the educational role of the city, a role that ended only with the closing of the pagan philosophical schools by the Christian emperor Justinian in A.D. 529.
Bearing, in machine construction, a connector (usually a support) that permits the connected members to rotate or to move in a straight line relative to one another. Often one of the members is fixed, and the bearing acts as a support for the moving member. Most bearings support rotating shafts against either transverse (radial) or thrust (axial) loads.
Bearings are what allow roller skates to turn, spin, and rotate on the axle of the wheel. Roller skate bearings are essential and protect against metal grinding on metal within the wheel. Even though bearings are small, donât be fooled! They play a huge part in how fast and how smooth you skate.