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 classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts. The term bearing is derived from the verb  to bear ; a bearing being a machine element that allows one part to bear (i.e., to support) another.ome applications apply bearing loads from varying directions and accept only limited play or slop as the applied load changes. One source of motion is gaps or play in the bearing. For example, a 10 mm shaft in a 12 mm hole has 2 mm play.