**EXHIBIT 4.C****FOURTH SUPPLEMENTAL INDENTURE**     FOURTH SUPPLEMENTAL INDENTURE DATED MAY 4, 2007 (THIS “FOURTH SUPPLEMENTAL INDENTURE”)AMONG (i) SOUTHERN NATURAL GAS COMPANY, A DELAWARE CORPORATION (THE “COMPANY”), (ii) SOLELYWITH RESPECT TO THE RECITALS HEREIN AND THE SECTIONS HEREOF IDENTIFIED BESIDE ITS SIGNATURE ON THESIGNATURE PAGE HEREOF, WILMINGTON TRUST COMPANY, A DELAWARE BANKING CORPORATION (THE “ORIGINALTRUSTEE”), AND (iii) THE BANK OF NEW YORK TRUST COMPANY, N.A., A NATIONAL BANKING ASSOCIATION(THE “SERIES TRUSTEE”).RECITALS     WHEREAS, the Company has heretofore executed and delivered to the Original Trustee (assuccessor in interest to JPMorgan Chase Bank, National Association, successor to ManufacturersHanover Trust Company, pursuant to the Instrument of Resignation, Appointment and Acceptance, datedas of February 27, 2003, among the Company, JPMorgan Chase Bank and the Original Trustee (the“2003 Resignation and Appointment”)) the Indenture, dated as of June 1, 1987 (suchIndenture as amended and supplemented by the First Supplemental Indenture thereto dated as ofSeptember 30, 1997, the Second Supplemental Indenture thereto dated as of February 13, 2001 and the2003 Resignation and Appointment being herein called the “Original Indenture”), providingfor the issuance from time to time of one or more series of the Company’s unsecured debentures,notes or other evidences of indebtedness (the “Securities”), the terms of which are to bedetermined as set forth in Section 3.01 of the Original Indenture; and     WHEREAS, Section 12.01(g) of the Original Indenture provides that the Company and the Trusteemay enter into indentures supplemental to the Original Indenture for the purpose of establishingthe form or terms of Securities of any series as permitted by Sections 2.01 and 3.01 of theOriginal Indenture; and     WHEREAS, Section 12.01(i) of the Original Indenture provides that the Company and the Trusteemay enter into indentures supplemental to the Original Indenture for the purpose of making suchother provisions in regard to matters or questions arising under the Original Indenture which shallnot be inconsistent with the provisions of the Original Indenture and which shall not adverselyaffect in any material respect the interests of any holders of Securities; and     WHEREAS, on March 26, 2007 (the “Original Issue Date”), the Company and the SeriesTrustee entered into an instrument entitled Third Supplemental Indenture, dated as of March 26,2007, as a supplement to the Original Indenture (including the exhibits thereto, the “ThirdSupplemental Indenture”), a copy of which is attached hereto as Exhibit A, for the purpose ofcreating a series of Securities under the Original Indenture designated as the 5.90% Notes Due 2017(the “Notes”); and on the Original Issue Date, the Company executed and the Series Trusteeauthenticated Notes in the aggregate principal amount of $500,000,000, such Notes
 

 
having been made payable to Cede & Co., nominee of The Depository Trust Company, and held bythe Series Trustee as custodian for Cede & Co. (the “Issued Notes”); and     WHEREAS, in addition to the Issued Notes, there are outstanding as of the date hereof thefollowing Securities issued under the Original Indenture:     (i) $48,055,000 in aggregate principal amount of the Company’s 6.70% Notes DueOctober 1, 2007;     (ii) $100,000,000 in aggregate principal amount of the Company’s 6.125% NotesDue September 15, 2008;     (iii) $300,000,000 in aggregate principal amount of the Company’s 7.35% NotesDue February 15, 2031; and     (iv) $300,000,000 in aggregate principal amount of the Company’s 8% Notes DueMarch 1, 2032 (the Securities described in clauses (i) through (iv) above beingherein called the “Outstanding Securities”); and     WHEREAS, the parties hereto desire to confirm that the Series Trustee shall act as the Trusteeunder the Indenture with respect to the Notes (including the Issued Notes), to clarify therespective rights, obligations and duties of the parties hereto in respect of the Notes (includingthe Issued Notes) and to set forth certain other related agreements and acknowledgments of theparties hereto; and     WHEREAS, the Company desires to confirm that the Issued Notes are entitled to the benefits ofthe Original Indenture and the Third Supplemental Indenture; and     WHEREAS, all acts and things necessary to constitute these presents a valid and bindingsupplemental indenture and agreement according to its terms, have been done and performed;     NOW, THEREFORE, THIS FOURTH SUPPLEMENTAL INDENTURE WITNESSETH:ARTICLE 1DEFINITIONS     Initially capitalized terms used and not otherwise defined in this Fourth SupplementalIndenture have the meanings ascribed to such terms in the Original Indenture.ARTICLE 2ADOPTION OF THIRD SUPPLEMENTAL INDENTURE     The Company and the Series Trustee agree that the Third Supplemental Indenture, as modified bythis Fourth Supplemental Indenture, (i) is hereby approved and adopted by the Company and theSeries Trustee to the same extent as if it were duly executed and delivered by
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the Company and the Series Trustee on the date hereof and (ii) shall be construed as anindenture supplemental to the Original Indenture, and as provided in the Original Indenture shallform a part thereof, for all purposes, including without limitation for the purpose of establishingthe Notes as a series of Securities pursuant to Section 3.01 of the Original Indenture. Allreferences in the Third Supplemental Indenture to the “Original Indenture” shall be deemed to referto the Original Indenture as defined in this Fourth Supplemental Indenture, and all referencesherein and in the Notes to the “Indenture” shall be deemed to refer to the Original Indenture asdefined in this Fourth Supplemental Indenture, as amended and supplemented by the ThirdSupplemental Indenture and this Fourth Supplemental Indenture.ARTICLE 3APPOINTMENT OF SERIES TRUSTEE     Section 3.01. *Appointment of Series Trustee*.     (a) The Company hereby appoints the Series Trustee as Trustee under the Indenture with respectto the Notes (including the Issued Notes) and vests and confirms to the Series Trustee all rights,powers, trusts, privileges, duties, security interests and obligations of Trustee under theIndenture with respect to the Notes (including the Issued Notes). The Series Trustee will notserve as Trustee under the Indenture with respect to the Outstanding Securities.     (b) The parties hereto expressly and irrevocably acknowledge and agree that the Series Trusteeshall have no rights, powers, trusts, privileges, duties, security interests or obligations of anykind (under the Indenture or otherwise) with respect to the Outstanding Securities.     Section 3.02. *Acceptance of Appointment by Series Trustee*. The Series Trustee hereby acceptsits appointment as Trustee under the Indenture with respect to the Notes (including the IssuedNotes) and agrees that it is hereby vested with all rights, powers, trusts, privileges, duties,security interests and obligations of Trustee under the Indenture with respect to the Notes(including the Issued Notes) and with respect to all property and monies held or to be held underthe Indenture with respect to the Notes. The Series Trustee represents and warrants to the Companythat the Series Trustee is qualified under the provisions of Section 9.08 of the Original Indentureand eligible under the provisions of Section 9.09 of the Original Indenture to act as a Trusteeunder the Indenture.     Section 3.03. *Duties and Obligations of Original Trustee in Respect of the OutstandingSecurities*. The Original Trustee shall continue to serve as Trustee under the Indenture withrespect to the Outstanding Securities, having all rights, powers, trusts, privileges, duties,security interests and obligations of Trustee under the Indenture with respect to the OutstandingSecurities.     Section 3.04 *The Notes and the Original Trustee.*The parties hereto acknowledge that theOriginal Trustee has not acted as Trustee or Paying Agent or in any other role with respect to theIssued Notes, and the Company and the Series Trustee irrevocably agree as between themselves andconfirm to the Original Trustee that the Original Trustee (a) shall have no rights, powers, trusts,privileges, duties, security interests or obligations of any nature whatsoever,
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whether as Trustee, Paying Agent or otherwise, with respect to the Notes or the authenticationthereof and (b) shall have no duties or obligations of any nature whatsoever under the Indenturewith respect to the Notes. Without limiting the generality of the foregoing, the Company and theSeries Trustee irrevocably agree as between themselves and confirm to the Original Trustee that noduties or obligations of any nature whatsoever on the part of the Original Trustee shall be readinto the Indenture with respect to the Notes.     Section 3.05 *The Outstanding Securities and the Series Trustee*     (a) The parties hereto irrevocably agree that the Series Trustee shall not have any liabilityarising out of any breach by the Original Trustee in the performance or non-performance of any ofits duties as Trustee under the Indenture with respect to the Outstanding Securities or otherwisein respect of any of the Outstanding Securities for so long as the Original Trustee is duly actingas Trustee with respect to such Outstanding Securities under the Indenture or in respect of anySecurities that may be issued pursuant to the Indenture after the date of this Fourth SupplementalIndenture and with respect to which the Original Trustee shall be duly appointed by the Company asTrustee that is directly and solely caused by any action or omission of the Original Trustee.     (b) The Company irrevocably agrees to indemnify the Series Trustee for, and to hold itharmless against, any loss, liability or expense (including the reasonable compensation and theexpenses and disbursements of its counsel) arising out of or in connection with the performance ornon-performance by the Original Trustee of its duties under the Indenture, including the reasonablecosts and expenses of defending itself against any claim or liability in connection therewith. Theindemnification provided for in this paragraph shall survive the termination of this FourthSupplemental Indenture and the Indenture.     Section 3.06. *Series Trustee to Serve as Paying Agent*. The Company and the Series Trusteeagree that the Paying Agent for the Notes shall initially be the Series Trustee.ARTICLE 4REPRESENTATIONS AND WARRANTIES OF THE COMPANY     The Company hereby represents and warrants to the Original Trustee and the Series Trustee that(i) the Original Indenture was duly authorized, executed and delivered by the Company, is in fullforce and effect and has not been amended or modified except as provided by or referred to in thisFourth Supplemental Indenture and (ii) no event has occurred and is continuing that, after theexecution and delivery of this Fourth Supplemental Indenture, constitutes, or after notice orlapse of time would constitute, an Event of Default.ARTICLE 5THE ISSUED NOTES     Section 5.01. *Ratification by Company*. The Company hereby ratifies and confirms its executionand delivery of the Issued Notes and confirms and agrees that the Issued Notes constitute valid andlegally binding obligations of the Company.
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     Section 5.02. *Certain Additional Agreements*.     (a) The Company hereby confirms its intention to appoint the Series Trustee as Trustee withrespect to the Notes, and the Series Trustee hereby confirms its intention to accept suchappointment, as of the Original Issue Date.     (b) The Company hereby irrevocably agrees, for the benefit of the other parties hereto and theholders of the Issued Notes at all times from the Original Issue Date to the date hereof, that suchholders were entitled to the benefits of the Original Indenture as supplemented by the ThirdSupplemental Indenture.     (c) The Company has requested that the Series Trustee, and the Series Trustee agrees that itwill, retrieve the Issued Notes and execute and attach to the Issued Notes a certificate ofauthentication of the Issued Notes in the form set forth in the Indenture and dated on or as soonas practicable after the date hereof.ARTICLE 6CERTAIN MATTERS WITH RESPECT TO THE ORIGINAL TRUSTEE     Section 6.01. *Knowledge of Original Trustee*. The parties hereto acknowledge that the OriginalTrustee had no knowledge on or prior to the Original Issue Date of the proposed execution anddelivery of the Third Supplemental Indenture or the issuance of the Issued Notes, and was notnotified of the issuance of the Issued Notes.     Section 6.02. *Indemnification of Original Trustee*. The Company irrevocably agrees toindemnify the Original Trustee for, and to hold it harmless against, any loss, claim, liability orexpense (including the reasonable compensation and the expenses and disbursements of its counsel)arising out of or in connection with the issuance of the Issued Notes, the execution and deliveryby the Company and the Series Trustee of the Third Supplemental Indenture, and the execution anddelivery by the parties hereto of this Fourth Supplemental Indenture, including, without limitingthe generality of the foregoing, the performance or any actual or alleged non-performance by theSeries Trustee of any of its powers, trusts, privileges or duties under the Indenture in respect ofthe Notes, or the exercise by the Series Trustee of any of its rights or privileges under theIndenture in respect of the Notes (including, without limitation, any realization by the SeriesTrustee in respect of any security interest created under the Indenture). The indemnity providedby this Section 6.02 shall include the reasonable costs and expenses of the Original Trusteeincurred in defending itself against any loss, claim or liability referred to above. Theindemnification provided for in this Section 6.02 shall survive the termination of this FourthSupplemental Indenture and the Indenture.ARTICLE 7MISCELLANEOUS     Section 7.01. *Execution as Supplemental Indenture*. This Fourth Supplemental Indenture isexecuted and shall be construed as an indenture supplemental to the Original
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Indenture and, as provided in the Original Indenture, this Fourth Supplemental Indenture formsa part thereof.     Section 7.02. *Responsibility for Recitals, Etc*. The recitals herein, in the ThirdSupplemental Indenture and in the Notes (except in the Series Trustee’s certificate ofauthentication in respect of the Notes, including the Issued Notes, which constitute statements ofthe Series Trustee, and except for the recitals herein that are specifically attributed to some orall of the parties hereto) shall be taken as the statements of the Company, and neither theOriginal Trustee nor the Series Trustee assumes any responsibility for the correctness thereof.Neither the Original Trustee nor the Series Trustee makes any representation as to the validity orsufficiency of the Third Supplemental Indenture or this Fourth Supplemental Indenture.     Section 7.03. *Provisions Binding on Successors*. All the respective covenants, stipulations,promises and agreements of each party hereto contained in this Fourth Supplemental Indenture shallbind such party’s successors and assigns whether so expressed or not.     Section 7.04. *New York Contract*. THIS FOURTH SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY ANDCONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.     Section 7.05. *Execution in Counterparts*. This Fourth Supplemental Indenture may be executedwith counterpart signature pages or in any number of counterparts, each of which shall be anoriginal but such counterparts shall together constitute but one and the same instrument.*[Signatures on following page.]*
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     IN WITNESS WHEREOF, the parties hereto have caused this Fourth Supplemental Indentureto be executed on May 4, 2007.      SOUTHERN NATURAL GAS COMPANY