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                                                                     EXHIBIT 4.2

                          FOURTH SUPPLEMENTAL INDENTURE

      Fourth Supplemental Indenture (this "SUPPLEMENTAL INDENTURE"), dated as of
January 20, 2005, among the entities listed on Schedule 1 attached hereto
("GUARANTEEING SUBSIDIARIES"), each being a subsidiary of Peabody Energy
Corporation (or its permitted successor), a Delaware corporation (the
"COMPANY"), the Company, the other Subsidiary Guarantors (as defined in the
Indenture referred to herein) and U.S. Bank National Association, as Trustee
under the Indenture referred to below (the "TRUSTEE").

                                   WITNESSETH

      WHEREAS, the Company has heretofore executed and delivered to the Trustee
the First Supplemental Indenture dated as of March 23, 2004 to the Indenture
dated as of March 19, 2004, (the "BASE INDENTURE," and, together with the First
Supplemental Indenture, the "INDENTURE") providing for the issuance of an
unlimited amount of 5-7/8% Senior Notes due 2016 (the "NOTES"); as supplemented
by the Second Supplemental Indenture, dated as of April 22, 2004; and Third
Supplemental Indenture, dated October 18, 2004;

      WHEREAS, the Indenture provides that under certain circumstances the
Guaranteeing Subsidiaries shall execute and deliver to the Trustee a
supplemental Indenture pursuant to which the Guaranteeing Subsidiaries shall
unconditionally guarantee all of the Company's Obligations under the Notes and
the Indenture on the terms and conditions set forth herein (the "SUBSIDIARY
GUARANTEE"); and

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

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

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

      2.    AGREEMENT TO GUARANTEE. The Guaranteeing Subsidiaries hereby agrees
as follows:

      (a)   Along with all Subsidiary Guarantors named in the Indenture, to
            jointly and severally Guarantee to each Holder of a Note
            authenticated and delivered by the Trustee and to the Trustee and
            its successors and assigns, irrespective of the validity and
            enforceability of the Indenture, the Notes or the obligations of the
            Company hereunder or thereunder, that:

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            (i)   the principal of and interest on the 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 Notes, if any, if lawful, and all other
                  obligations of the Company to the Holders or the 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
                  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 Subsidiary 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 Notes or the
            Indenture, the absence of any action to enforce the same, any waiver
            or consent by any Holder of the 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
            Subsidiary 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 Subsidiary Guarantee shall not be discharged except by complete
            performance of the obligations contained in the Notes and the
            Indenture.

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

      (f)   The Guaranteeing Subsidiaries 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 Subsidiary Guarantors, on the one hand, and the
            Holders and the Trustee, on the other hand, (x) the maturity of the
            obligations guaranteed hereby may be accelerated as provided in
            Article 6 of the First Supplemental Indenture for the purposes of
            this 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 First Supplemental Indenture, such obligations
            (whether or not due and payable) shall forthwith become due and
            payable by the Subsidiary Guarantors for the purpose of this
            Subsidiary Guarantee.

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

      (i)   Pursuant to Section 9.04 of the First Supplemental 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 Subsidiary Guarantor in respect of
            the obligations of such other Subsidiary Guarantor under Article 9
            of the First Supplemental Indenture shall result in the obligations
            of such Subsidiary Guarantor under its Subsidiary Guarantee not
            constituting a fraudulent transfer or conveyance.

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

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

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

            (i)   subject to Section 9.04 of the First Supplemental Indenture,
                  the Person formed by or surviving any such consolidation or
                  merger (if other than a Subsidiary Guarantor or the Company)
                  unconditionally assumes all the obligations of such Subsidiary
                  Guarantor, pursuant to a supplemental Indenture in form and
                  substance reasonably satisfactory to the Trustee, under the
                  Notes, the Indenture and the 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
            Indenture, executed and delivered to the Trustee and satisfactory in
            form to the Trustee, of the Subsidiary Guarantee endorsed upon the
            Notes and the due and punctual performance of all of the covenants
            and conditions of the Indenture to be performed by the Subsidiary
            Guarantor, such successor corporation shall succeed to and be
            substituted for the Subsidiary Guarantor with the same effect as if
            it had been named herein as a Subsidiary Guarantor. Such successor
            corporation thereupon may cause to be signed any or all of the
            Subsidiary Guarantees to be endorsed upon all of the Notes issuable
            hereunder which theretofore shall not have been signed by the
            Company and delivered to the Trustee. All the Subsidiary Guarantees
            so issued shall in all respects have the same legal rank and benefit
            under the Indenture as the Subsidiary Guarantees theretofore and
            thereafter issued in accordance with the terms of the Indenture as
            though all of such Subsidiary Guarantees had been issued at the date
            of the execution hereof.

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

      5.    RELEASES.

      (a)   In the event of a sale or other disposition of all of the assets of
            any Subsidiary Guarantor, by way of merger, consolidation or
            otherwise, or a sale or other disposition of all to the capital
            stock of any Subsidiary Guarantor, then such Subsidiary 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
            Subsidiary 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 Subsidiary Guarantor) will be released and
            relieved of any obligations under its Subsidiary Guarantee; provided
            that the Net Proceeds of such sale or other disposition are applied
            in accordance with the applicable provisions of the Indenture,
            including without limitation Section 4.10 of the Indenture. Upon
            delivery by the Company to the Trustee of an Officer's Certificate
            and an Opinion of Counsel to the effect that such sale or other
            disposition

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            was made by the Company in accordance with the provisions of the
            Indenture, including without limitation Section 4.10 of the First
            Supplemental Indenture, the Trustee shall execute any documents
            reasonably required in order to evidence the release of any
            Subsidiary Guarantor from its obligations under its Subsidiary
            Guarantee.

      (b)   Any Subsidiary Guarantor not released from its obligations under its
            Subsidiary Guarantee shall remain liable for the full amount of
            principal of and interest on the Notes and for the other obligations
            of any Subsidiary Guarantor under the Indenture as provided in
            Article 9 of the First Supplemental Indenture.

      6.    NO RECOURSE AGAINST OTHERS. No past, present or future director,
officer, employee, incorporator, stockholder or agent of the Guaranteeing
Subsidiaries, as such, shall have any liability for any obligations of the
Company or any Guaranteeing Subsidiaries under the Notes, any Subsidiary
Guarantees, the Indenture or this Supplemental Indenture or for any claim based
on, in respect of, or by reason of, such obligations or their creation. Each
Holder of the Notes by accepting a Note waives and releases all such liability.
The waiver and release are part of the consideration for issuance of the 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 LAW OF THE STATE OF NEW YORK SHALL
GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE.

      8.    COUNTERPARTS. The parties may sign any number of copies of this
Supplemental 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 TRUSTEE. The Trustee shall not be responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made solely by the Guaranteeing Subsidiaries and the Company.

                                       5
<PAGE>

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

PEABODY ENERGY CORPORATION                US BANK NATIONAL ASSOCIATION
("COMPANY")                               ("TRUSTEE")

By: /s/ Walter L. Hawkins, Jr.            By: /s/ Philip G. Kane, Jr.
    --------------------------                ------------------------
Name: Walter L.Hawkins, Jr.               Name: Philip G. Kane, Jr.
Title: Vice President and Treasurer       Title: Vice President

EXISTING SUBSIDIARY GUARANTORS:

                       AFFINITY MINING COMPANY
                       APPALACHIA MINE SERVICES, LLC
                       ARCLAR COMPANY, LLC
                       ARID OPERATIONS INC.
                       BEAVER DAM COAL COMPANY
                       BIG RIDGE, INC.
                       BIG SKY COAL COMPANY
                       BLACK BEAUTY COAL COMPANY
                       BLACK BEAUTY EQUIPMENT COMPANY
                       BLACK BEAUTY HOLDING COMPANY, LLC
                       BLACK BEAUTY MINING, INC.
                       BLACK BEAUTY RESOURCES, INC.
                       BLACK BEAUTY UNDERGROUND, INC.
                       BLACK HILLS MINING COMPANY, LLC
                       BLACK STALLION COAL COMPANY, LLC
                       BLACK WALNUT COAL COMPANY
                       BLUEGRASS COAL COMPANY
                       BTU EMPIRE CORPORATION
                       BTU VENEZUELA, LLC
                       CABALLO COAL COMPANY
                       CHARLES COAL COMPANY
                       CLEATON COAL COMPANY
                       COAL PROPERTIES CORP.
                       COALSALES, LLC
                       COALSALES II, LLC f/k/a PEABODY COALSALES COMPANY
                       COALTRADE INTERNATIONAL, LLC
                             f/k/a PEABODY COALTRADE INTERNATIONAL, LLC
                       COALTRADE, LLC f/k/a PEABODY COALTRADE, INC.
                       COAL RESERVES HOLDING LIMITED LIABILITY
                       COMPANY NO. 1
                       COAL RESERVES HOLDING LIMITED LIABILITY
                       COMPANY NO. 2
                       COLONY BAY COAL COMPANY
                       COLORADO YAMPA COAL COMPANY
                       COOK MOUNTAIN COAL COMPANY

                                       6
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                       COTTONWOOD LAND COMPANY
                       CYPRUS CREEK LAND COMPANY
                       CYPRUS CREEK LAND RESOURCES, LLC
                       EACC CAMPS, INC.
                       EAGLE COAL COMPANY
                       EASTERN ASSOCIATED COAL CORP.
                       EASTERN ROYALTY CORP.
                       EMPIRE MARINE, LLC
                       FALCON COAL COMPANY
                       GALLO FINANCE COMPANY
                       GIBCO MOTOR EXPRESS, LLC
                       GOLD FIELDS CHILE, S.A.
                       GOLD FIELDS MINING, LLC
                             f/k/a GOLD FIELDS MINING CORPORATION
                       GOLD FIELDS OPERATING CO. - ORTIZ
                       GRAND EAGLE MINING, INC.
                       HAYDEN GULCH TERMINAL, INC.
                       HIGHLAND MINING COMPANY
                       HIGHWALL MINING SERVICES COMPANY
                       HILLSIDE MINING COMPANY
                       INDEPENDENCE MATERIAL HANDLING
                            COMPANY
                       INDIAN HILL COMPANY
                       INTERIOR HOLDINGS CORP.
                       JAMES RIVER COAL TERMINAL COMPANY
                       JARRELL'S BRANCH COAL COMPANY
                       JUNIPER COAL COMPANY
                       KANAWHA RIVER VENTURES I, LLC
                       KAYENTA MOBILE HOME PARK, INC.
                       LOGAN FORK COAL COMPANY
                       MARTINKA COAL COMPANY
                       MIDCO SUPPLY AND EQUIPMENT
                            CORPORATION
                       MIDWEST COAL ACQUISITION CORP.
                       MOUNTAIN VIEW COAL COMPANY
                       MUSTANG ENERGY COMPANY, L.L.C.
                       NORTH PAGE COAL CORP.
                       OHIO COUNTY COAL COMPANY
                       PATRIOT COAL COMPANY, L.P.
                       PDC PARTNERSHIP HOLDINGS, INC.
                       PEABODY AMERICA, INC.
                       PEABODY ARCHVEYOR, L.L.C.
                       PEABODY COAL COMPANY
                       PEABODY DEVELOPMENT COMPANY,LLC
                       PEABODY DEVELOPMENT LAND HOLDINGS, LLC
                       PEABODY ENERGY GENERATION HOLDING COMPANY

                                       7
<PAGE>

                       PEABODY ENERGY INVESTMENTS, INC.
                       PEABODY ENERGY SOLUTIONS, INC.
                       PEABODY HOLDING COMPANY, INC.
                       PEABODY INVESTMENTS CORP.
                             f/k/a BTU WORLDWIDE, INC.
                       PEABODY NATURAL GAS, LLC
                       PEABODY NATURAL RESOURCES COMPANY
                       PEABODY POWERTREE INVESTMENTS, LLC
                       PEABODY RECREATIONAL LANDS, L.L.C.
                       PEABODY SOUTHWESTERN COAL COMPANY
                       PEABODY TERMINALS, INC.
                       PEABODY VENEZUELA COAL CORP.
                       PEABODY-WATERSIDE DEVELOPMENT, L.L.C.
                       PEABODY WESTERN COAL COMPANY
                       PEC EQUIPMENT COMPANY, LLC
                       PINE RIDGE COAL COMPANY
                       POINT PLEASANT DOCK COMPANY, LLC
                       POND CREEK LAND RESOURCES, LLC
                       POND RIVER LAND COMPANY
                       PORCUPINE PRODUCTION, LLC
                       PORCUPINE TRANSPORTATION, LLC
                       POWDER RIVER COAL COMPANY
                       PRAIRIE STATE GENERATING COMPANY, LLC
                       RIO ESCONDIDO COAL CORP.
                       RIVERS EDGE MINING, INC.
                       RIVERVIEW TERMINAL COMPANY
                       SENECA COAL COMPANY
                       SENTRY MINING COMPANY
                       SHOSHONE COAL CORPORATION
                       SNOWBERRY LAND COMPANY
                       STAR LAKE ENERGY COMPANY, L.L.C.
                       STERLING SMOKELESS COAL COMPANY
                       SUGAR CAMP PROPERTIES
                       THOROUGHBRED, L.L.C.
                       THOROUGHBRED GENERATING COMPANY, LLC
                       THOROUGHBRED MINING COMPANY, L.L.C.
                       TWENTYMILE COAL COMPANY
                       WILLIAMSVILLE COAL COMPANY, LLC
                       YANKEETOWN DOCK CORPORATION

                       By: /s/ Walter L. Hawkins, Jr.
                           --------------------------
                       Name: Walter L. Hawkins, Jr.

                       Title:  Vice President

                                       8
<PAGE>

NEW GUARANTEEING SUBSIDIARIES:

                                     DIXON MINING COMPANY, LLC

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

                                     DODGE HILL HOLDING JV, LLC

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

                                     DODGE HILL OF KENTUCKY, LLC

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

                                     DODGE HILL MINING COMPANY, LLC

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

                                     HMC MINING, LLC

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

                                       9
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                                     PHC ACQUISITION CORP.

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

                                     RANDOLPH LAND HOLDING COMPANY, LLC

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

                                     UNION COUNTY COAL CO., LLC

                                     By: /s/ Walter L. Hawkins, Jr.
                                         --------------------------------
                                     Name: Walter L. Hawkins, Jr.
                                     Title: Vice President & Treasurer

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                                   SCHEDULE 1

                          NEW GUARANTEEING SUBSIDIARIES

DIXON MINING COMPANY, LLC, a Kentucky Limited Liability Company
DODGE HILL HOLDING JV, LLC, a Delaware Limited Liability
DODGE HILL OF KENTUCKY, LLC, a Delaware Limited Liability
DODGE HILL MINING COMPANY, LLC, a Kentucky Limited Liability Company
HMC MINING, LLC, a Delaware Limited Liability
PHC ACQUISITION CORP., a Delaware corporation
RANDOLPH LAND HOLDING COMPANY, LLC, a Delaware Limited Liability
UNION COUNTY COAL CO., LLC, a Kentucky Limited Liability Company

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