EXHIBIT 4.18

             FOURTH SUPPLEMENTAL SENIOR SUBORDINATED NOTE INDENTURE

         FOURTH SUPPLEMENTAL SENIOR SUBORDINATED NOTE INDENTURE (this
"Supplemental Senior Subordinated Note Indenture"), dated as of February 16,
2000 among Peabody Natural Gas, LLC, a Delaware limited liability company (the
"Guaranteeing Subsidiary"), 'a subsidiary of Peabody Holding Company, Inc. (or
its permitted successor), a New York corporation (the "Company"), the Company,
the other Senior Subordinated Note Guarantors (as defined in the Senior
Subordinated Note Indenture referred to herein) and State Street Bank and Trust
Company, as Senior Subordinated Note Trustee under the Senior Subordinated Note
Indenture referred to below (the "Senior Subordinated Note Trustee").

                                   WITNESSETH

         WHEREAS, the Company has heretofore executed and delivered to the
Senior Subordinated Note Trustee a Senior Subordinated Note Indenture (the
"Senior Subordinated Note Indenture"), dated as of May 18, 1998 providing for
the issuance of an aggregate principal amount of up to $650.0 million of 9-5/8%
Senior Subordinated Notes due 2008 (the "Senior Subordinated Notes");

         WHEREAS, the Senior Subordinated Note Indenture provides that under
certain circumstances the Guaranteeing Subsidiary shall execute and deliver to
the Senior Subordinated Note Trustee a Supplemental Senior Subordinated Note
Indenture pursuant to which the Guaranteeing Subsidiary shall unconditionally
guarantee all of the Company's Obligations under the Senior Subordinated Notes
and the Senior Subordinated Note Indenture on the terms and conditions set forth
herein (the "Subordinated Subsidiary Guarantee"); and

         WHEREAS, pursuant to Section 9.01 of the Senior Subordinated Note
Indenture, the Senior Subordinated Note Trustee is authorized to execute and
deliver this Supplemental Senior Subordinated Note Indenture.

        NOW THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the
Guaranteeing Subsidiary and the Senior Subordinated Note Trustee mutually
covenant and agree for the equal and ratable benefit of the Holders of the
Senior Subordinated Notes as follows:

         1. CAPITALIZED TERMS. Capitalized terms used herein without definition
shall have the meanings assigned to them in the Senior Subordinated Note
Indenture.

         2. AGREEMENT TO GUARANTEE. The Guaranteeing Subsidiary hereby agrees as
follows
                  (a) Along with all Senior Subordinated Note Guarantors named
         in the Senior Subordinated Note Indenture, to jointly and severally
         Guarantee to each Holder of a Senior Subordinated Note authenticated
         and delivered by the Senior Subordinated Note Trustee and to the Senior
         Subordinated Note Trustee and its successors and assigns, irrespective
         of the validity and enforceability of the Senior Subordinated Note
         Indenture, the Senior Subordinated Notes or the obligations of the
         Company hereunder or thereunder, that:



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         (i)      the principal of and interest on the Senior Subordinated Notes
                  will be promptly paid in full when due, whether at maturity,
                  by acceleration, redemption or otherwise, and interest on the
                  overdue principal of and interest on the Senior Subordinated
                  Notes, if any, if lawful, and all other obligations of the
                  Company to the Holders or the Senior Subordinated Note Trustee
                  hereunder or thereunder will be promptly paid in full or
                  performed, all in accordance with the terms hereof and
                  thereof, and

         (ii)     in case of any extension of time of payment or renewal of any
                  Senior Subordinated Notes or any of such other obligations,
                  that same will be promptly paid in full when due or performed
                  in accordance with the terms of the extension or renewal,
                  whether at stated maturity, by acceleration or otherwise.
                  Failing payment when due of any amount so guaranteed or any
                  performance so guaranteed for whatever reason, the Senior
                  Subordinated Note Guarantors shall be jointly and severally
                  obligated to pay the same immediately.

                  (b) The obligations hereunder shall be unconditional,
         irrespective of the validity, regularity or enforceability of the
         Senior Subordinated Notes or the Senior Subordinated Note Indenture,
         the absence of any action to enforce the same, any waiver or consent by
         any Holder of the Senior Subordinated Notes with respect to any
         provisions hereof or thereof, the recovery of any judgment against the
         Company, any action to enforce the same or any other circumstance which
         might otherwise constitute a legal or equitable discharge or defense of
         a Senior Subordinated Note Guarantor.

                  (c) The following is hereby waived: diligence presentment,
         demand of payment, filing of claims with a court in the event of
         insolvency or bankruptcy of the Company, any right to require a
         proceeding first against the Company, protest, notice and all demands
         whatsoever.

                  (d) This Subordinated Subsidiary Guarantee shall not be
         discharged except by complete performance of the obligations contained
         in the Senior Subordinated Notes and the Senior Subordinated Note
         Indenture.

                  (e) If any Holder or the Senior Subordinated Note Trustee is
         required by any court or otherwise to return to the Company, the Senior
         Subordinated Note Guarantors, or any custodian, Senior Subordinated
         Note Trustee, liquidator or other similar official acting in relation
         to either the Company or the Senior Subordinated Note Guarantors, any
         amount paid by either to the Senior Subordinated Note Trustee or such
         Holder, this Subordinated Subsidiary Guarantee, to the extent
         theretofore discharged, shall be reinstated in full force and effect.

                  (f) The Guaranteeing Subsidiary shall not be entitled to any
         right of subrogation in relation to the Holders in respect of any
         obligations guaranteed hereby until payment in full of all obligations
         guaranteed hereby.



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                  (g) As between the Senior Subordinated Note Guarantors, on the
         one hand, and the Holders and the Senior Subordinated Note Trustee, on
         the other hand, (x) the maturity of the obligations guaranteed hereby
         may be accelerated as provided in Article 6 of the Senior Subordinated
         Note Indenture for the purposes of this Subordinated Subsidiary
         Guarantee, notwithstanding any stay, injunction or other prohibition
         preventing such acceleration in respect of the obligations guaranteed
         hereby, and (y) in the event of any declaration of acceleration of such
         obligations as provided in Article 6 of the Senior Subordinated Note
         Indenture, such obligations (whether or not due and payable) shall
         forthwith become due and payable by the Senior Subordinated Note
         Guarantors for the purpose of this Subordinated Subsidiary Guarantee.

                  (h) The Senior Subordinated Note Guarantors shall have the
         right to seek contribution from any non-paying Senior Subordinated Note
         Guarantor so long as the exercise of such right does not impair the
         rights of the Holders under the Subordinated Subsidiary Guarantee.

                  (i) Pursuant to Section 11.02 of the Senior Subordinated Note
         Indenture, after giving effect to any maximum amount and any other
         contingent and fixed liabilities that are relevant under any applicable
         Bankruptcy or fraudulent conveyance laws, and after giving effect to
         any collections from, rights to receive contribution from or payments
         made by or on behalf of any other Senior Subordinated Note Guarantor in
         respect of the obligations of such other Senior Subordinated Note
         Guarantor under Article 11 of the Senior Subordinated Note Indenture
         shall result in the obligations of such Senior Subordinated Note
         Guarantor under its Subordinated Subsidiary Guarantee not constituting
         a fraudulent transfer or conveyance.

         3. EXECUTION AND DELIVERY. Each Guaranteeing Subsidiary agrees that the
Subordinated Subsidiary Guarantees shall remain in full force and effect
notwithstanding any failure to endorse on each Senior Subordinated Note a
notation of such Subordinated Subsidiary Guarantee.

         4. GUARANTEEING SUBSIDIARY MAY CONSOLIDATE, ETC. ON CERTAIN TERMS

                  (a) The Guaranteeing Subsidiary may not consolidate with or
         merge with or into (whether or not such Senior Subordinated Note
         Guarantor is the surviving Person) another corporation, Person or
         entity whether or not affiliated with such Senior Subordinated Note
         Guarantor unless:

                  (i) subject to Section 11.05 of the Senior Subordinated Note
                  Indenture, the Person formed by or surviving any such
                  consolidation or merger (if other than a Senior Subordinated
                  Note Guarantor or the Company) unconditionally assumes all the
                  obligations of such Senior Subordinated Note Guarantor,
                  pursuant to a supplemental Senior Subordinated Note Indenture
                  in form and substance reasonably satisfactory to the Senior
                  Subordinated Note Trustee, under the Senior Subordinated
                  Notes, the Senior Subordinated Note Indenture and the
                  Subordinated Subsidiary Guarantee on the terms set forth
                  herein or therein; and



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                  (ii) immediately after giving effect to such transaction, no
                  Default or Event of Default exists.

                  (b) In case of any such consolidation, merger, sale or
         conveyance and upon the assumption by the successor corporation, by
         supplemental Senior Subordinated Note Indenture, executed and delivered
         to the Senior Subordinated Note Trustee and satisfactory in form to the
         Senior Subordinated Note Trustee, of the Subordinated Subsidiary
         Guarantee endorsed upon the Senior Subordinated Notes and the due and
         punctual performance of all of the covenants and conditions of the
         Senior Subordinated Note Indenture to be performed by the Senior
         Subordinated Note Guarantor, such successor corporation shall succeed
         to and be substituted for the Senior Subordinated Note Guarantor with
         the same effect as if it had been named herein as a Senior Subordinated
         Note Guarantor. Such successor corporation thereupon may cause to be
         signed any or all of the Subordinated Subsidiary Guarantees to be
         endorsed upon all of the Senior Subordinated Notes issuable hereunder
         which theretofore shall not have been signed by the Company and
         delivered to the Senior Subordinated Note Trustee. All the Subordinated
         Subsidiary Guarantees so issued shall in all respects have the same
         legal rank and benefit under the Senior Subordinated Note Indenture as
         the Subordinated Subsidiary Guarantees theretofore and thereafter
         issued in accordance with the terms of the Senior Subordinated Note
         Indenture as though all of, such Subordinated Subsidiary Guarantees had
         been issued at the date of the execution hereof.

                  (c) Except as set forth in Articles 4 and 5 of the Senior
         Subordinated Note Indenture, and notwithstanding clauses (a) and (b)
         above, nothing contained in the Senior Subordinated Note Indenture or
         in any of the Senior Subordinated Notes shall prevent any consolidation
         or merger of a Senior Subordinated Note Guarantor with or into the
         Company or another Senior Subordinated Note Guarantor, or shall prevent
         any sale or conveyance of the property of a Senior Subordinated Note
         Guarantor as an entirety or substantially as an entirety to the Company
         or another Senior Subordinated Note Guarantor.

         5. RELEASES.

                  (a) In the event of a sale or other disposition of all of the'
         assets of any Senior Subordinated Note Guarantor, by way of merger,
         consolidation or other-wise, or a sale or other disposition of all to
         the capital stock of any Senior Subordinated Note Guarantor, then such
         Senior Subordinated Note Guarantor (in the event of a sale or other
         disposition, by way of merger, consolidation or otherwise, of all of
         the capital stock of such Senior Subordinated Note Guarantor) or the
         corporation acquiring the property (in the event of a sale or other
         disposition of all or substantially all of the assets of such Senior
         Subordinated Note Guarantor) will be released and relieved of any
         obligations under its Subordinated Subsidiary Guarantee; provided that
         the Net Proceeds of such sale or other disposition are applied in
         accordance with the applicable provisions of the Senior Subordinated
         Note Indenture, including without limitation Section 4.10 of the Senior
         Subordinated Note Indenture. Upon delivery by the Company to the Senior
         Subordinated Note Trustee of an Officers' Certificate and an Opinion of
         Counsel to the effect that such sale or other disposition was made by
         the Company in accordance with the provisions of the Senior
         Subordinated Note Indenture, including without limitation Section 4. 10
         of the Senior Subordinated Note Indenture, the Senior Subordinated Note
         Trustee shall execute any documents reasonably required in order to
         evidence the



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         release of any Senior Subordinated Note Guarantor from its obligations
         under its Subordinated Subsidiary Guarantee.

                  (b) Any Senior Subordinated Note Guarantor not released from
         its obligations under its Subordinated Subsidiary Guarantee shall
         remain liable for the full amount of principal of and interest on the
         Senior Subordinated Notes and for the other obligations of any Senior
         Subordinated Note Guarantor under the Senior Subordinated Note
         Indenture as provided in Article I of the Senior Subordinated Note
         Indenture.

         6. NO RECOURSE AGAINST OTHERS. No past, present or future director,
officer, employee, incorporator, stockholder or agent of the Guaranteeing
Subsidiary, as such, shall have any liability for any obligations of the Company
or any Guaranteeing Subsidiary under the Senior Subordinated Notes, any
Subordinated Subsidiary Guarantees, the Senior Subordinated Note Indenture or
this Supplemental Senior Subordinated Note Indenture or for any claim based on,
in respect of, or by reason of, such obligations or their creation. Each Holder
of the Senior Subordinated Notes by accepting a Senior Subordinated Note waives
and releases all such liability. The waiver and release are part of the
consideration for issuance of the Senior Subordinated Notes. Such waiver may not
be effective to waive liabilities under the federal securities laws and it is
the view of the Commission that such a waiver is against public policy.

         7. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK
SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL SENIOR SUBORDINATED NOTE
INDENTURE BUT WITHOUT GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW
TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE
REQUIRED THEREBY.

         8. COUNTERPARTS. The parties may sign any number of copies of this
Supplemental Senior Subordinated Note Indenture. Each signed copy shall be an
original, but all of them together represent the same agreement.

         9. EFFECT OF HEADINGS. The Section headings herein are for convenience
only and shall not affect the construction hereof

         10 THE SENIOR SUBORDINATED NOTE TRUSTEE. The Senior Subordinated Note
Trustee shall not be responsible in any manner whatsoever for or in respect of
the validity or sufficiency of this Supplemental Senior Subordinated Note
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made solely by the Guaranteeing Subsidiary and the Company.



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         IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Senior Subordinated Note Indenture to be duly executed and attested, all as of
the date first above written.

Dated: February 16, 2000

                                        PEABODY NATURAL GAS, LLC



                                               By:  /S/ S. F. Schaab
                                                  ------------------------------
                                               Name: S. F. Schaab
                                               Title: Vice President & Treasurer



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