<div class="htmlview paragraph"><b>THE authors state that the balance of a machine part or group of machine parts is a function of the motion of their center of gravity, and that perfect balance of the moving parts exists when their center of gravity remains stationary</b>.</div> <div class="htmlview paragraph"><b>When the center of gravity oscillates, unbalance is present, the amount being proportional to the magnitude of the oscillation of the center of gravity</b>.</div> <div class="htmlview paragraph"><b>The subject of balancing is discussed practically, balancing machines being also described and commented upon. The seven main requirements of a good balancing machine are stated.</b></div> <div class="htmlview paragraph"><b>Regarding balance limits, in computing those for an assembled engine, the first item is to obtain the balance on each of the rotating parts and the second, to ascertain the limit to be placed on the fits of “pilots.” In conclusion, fourteen items constituting the total unbalance of the engine chosen for illustration are enumerated.</b></div>