A-Powered CruiserFlare BackBui ns Threestroyers damaged four barges 13 miles north northwest of Dong Hoi with volleys from their 5-inch guns. There was no report of damage to the destroyers.U.S. Navy fightcr-bombers. that have been hammering coastal shipping daily, attacked 10 barges Tuesday northwest of Dong Hoi. A precise damage assessment was not available.AIR FORCE pilots, focusing most of their attention further inland and to the north around Dienbienphu and Hanoi, pounded highways, railroads and supply depots.Air Force, Navv and Ma-the first time in nearly a week. A destroyer also exchanged fire briefly with a shore battery Monday, but no enemy vessel was involved.second and third-degree burns, lace of Merritt Island, Fla.,and carries on her the flag of Rear Adm. A. S. Goodfel-low, commander of the U.S. 7th Fleet's cruiser destroyer group.The spokesman said the vessel was making her first cruise in the waters off Vietnam.TWO DESTROYERS, t h e Ingersoll and Keppler, at-r.I «cc„„,pa„S,n6 ,„c sen,,™: M* **£ “«g Glen Smith, a retired colonel y and a member of the staff ofthe Senate armed services preparedness subcommittee.irie*ec-The Pentagon said it has nonthpr rlptails availahlp nn thpWASHINGTON (AP)-A 5-inch shell exploded aboard the destroyer Manley off Vietnam yes-lerday while Sen. Henry M. Jackson, D-Wash., was aboard to observe naval bombardment, 'the Pentagon said.The senator was not injured, but three crewmen were burned in a fire which followed the blast.The incident occurred as the 4,200-ton destroyer shelled Communist. positions south of the big naval base at Da Nang in South Vietnam.THE PENTAGON said the explosion occurred in one of the destroyer’s 5-inch gun mounts when a shell ignited before being rammed into the firing chamber.The three crewmen sufferedbut were listed in good condition. They were not immediately identified.The destroyer was operating B under direction of Cmdr. Warren C. Graham of Valdosta, Ga. It carried a crew of about 300.JACKSON, a member of the l* Senate Armed Services Committee, has been in Vietnam for a•I'weck on an inspection.On Destroyerhas sent its only nuclear-powered cruiser into the Gulf of Tonkin for patrol duty off the coast of North Vietnam, an American military spokesman said last night.The spokesman said the cruiser Long Beach steamed into the South China Sea Nov.30 to relieve the destroyer King.IT WAS NOT clear what the duties of the Long Beach would be, but in addition to the five guns and torpedoes carried by the King, the nuclear vessel is equipped with both intermediate and long-range surface-to-air missiles.The Long Beach is commanded by Capt. K. C. Wal-USS Long Beach Patrols Off NortlNew York Times Service SAIGON — The U.S. Navy