EE STATED THAT THE SUCTION FOR THE DUST COLLECTION SYSTEM ON THE NO. 463 ROOF BOLTING MACHINE THAT HE WAS OPERATING BECAME STOPPED-UP. HE GOT OFF OF THE MACHINE AND WAS STANDING ON THE RIGHT H AND SIDE ATTEMPTING TO CORRECT THE PROBLEM. WHEN A PIECE OF ROCK 69"" LONG, 30"" WIDE AND 6""-8"" THICK FELL FROM THE MINE ROOF AND STRUCK THE MAST OF THE ROOF BOLTING MACHINE AND THEN STRUCK HIM