Abstract: A steel ball machining apparatus comprises a cylindrical ball storing vessel having an opening, a steel ball machining mechanism, a steel ball supply path for supplying steel balls to said machining mechanism from the opening in said vessel, a steel ball discharge path for discharging the balls from said machining mechanism, and an elevating conveyor is provided between the discharge path and the cylindrical vessel, the elevating conveyor having a ball receiving vessel which is adapted to move between a lower position in which the ball receiving vessel aligns with the discharge path and an upper position over the cylindrical vessel, a lifter of said ball receiving vessel, a ball return path provided at the upper position for feeding the balls from the ball receiving vessel over to the cylindrical vessel, the return path having a ball exit adapted to discharge the balls to said cylindrical vessel at radially different positions therein.

Abstract: A steel ball machining apparatus comprises a ball machining mechanism having a pair of machining plates which are adapted to oppose and rotate relative to each other, a steel ball storing vessel for supplying to and receiving from said polishing mechanism steel balls, a steel ball supply path provided between said machining mechanism and said steel ball storing vessel, a steel ball discharge path provided between said machining mechanism and said steel ball storing vessel adapted to discharge said steel balls to said vessel, and a set of parallel bars provided in at least one of said steel supply path and steel ball discharge path so as to eliminate foreign matter.

Abstract: A novel sulfur-containing aromatic vinyl compound represented by the following general formula (I) ##STR1## wherein R.sub.1 represents an alkylene group having 1 to 3 carbon atoms and R.sub.2 represents an alkylene group having 2 to 8 carbon atoms, and the two bonds in the benzene ring are meta or para to each other. A curable composition comprising at least one of the said vinyl compounds, an isocyanate compound and a radical polymerization initiator. On heating, the composition gives a crosslinked polymer article useful as lenses.