<ARTICLE> 5
<CIK> 0000006769
<NAME> ART.5 FDS FOR 1997 SECOND QUARTER 10-Q
<MULTIPLIER> 1,000
<CURRENCY> U.S. DOLLAR
       
                             
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1997
<PERIOD-START>                             JAN-01-1997
<PERIOD-END>                               JUN-30-1997
<EXCHANGE-RATE>                                  1,000
<CASH>                                          14,182
<SECURITIES>                                         0
<RECEIVABLES>                                  201,431
<ALLOWANCES>                                         0
<INVENTORY>                                     17,664
<CURRENT-ASSETS>                               249,250
<PP&E>                                       5,750,873
<DEPRECIATION>                               2,458,790
<TOTAL-ASSETS>                               3,599,782
<CURRENT-LIABILITIES>                          268,680
<BONDS>                                      1,349,099
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                       114,369
<OTHER-SE>                                   1,474,279
<TOTAL-LIABILITY-AND-EQUITY>                 3,599,782
<SALES>                                        481,128
<TOTAL-REVENUES>                               580,669
<CGS>                                          398,774
<TOTAL-COSTS>                                  398,774
<OTHER-EXPENSES>                                18,083
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                              32,101
<INCOME-PRETAX>                                131,711
<INCOME-TAX>                                    53,088
<INCOME-CONTINUING>                             78,623
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    78,623
<EPS-PRIMARY>                                      .85
<EPS-DILUTED>                                      .84