THROWING THE BEADS A mother at Shannon, waving to her son Setting out from North Kerry, flung A rosary beads out to the tarmac Suddenly as a lifebelt hurled from a pier. Don't forget to say your prayers in Boston. She saw the bright crucifix among skyscrapers, Shielding him from harm in streets out of serials, Comforting as a fat Irish cop in a gangster film Rattling his baton along a railing after dark. -- Sean Dunne (1956-95), from "Sheltered Nest."