Document:

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                                                                    EXHIBIT 10.1
                              EMPLOYMENT AGREEMENT

         THIS AGREEMENT, dated as of April 23, 2001, is between EarthWeb Inc., a
Delaware corporation (the "Company"), with its principal place of business at 3
Park Avenue, New York, New York, and Scot W. Melland, an individual residing at
_______________________ (the "Employee").

         In consideration of the Company securing the services of the Employee
and the Employee's undertaking employment with the Company, the Company and the
Employee hereby agree to be bound by and comply with the following terms and
conditions and agree as follows:

         Section 1. At-Will Employment. Employee acknowledges and agrees that
his employment status is that of an employee-at-will and that Employee's
employment may be terminated by the Company or the Employee at any time with or
without cause, subject to the terms and conditions in the Addendum hereto.

         Section 2.  Compensation. In consideration of the services to
         ----------  ------------
be rendered hereunder, the Employee shall be paid in accordance with the
Addendum hereto.

         Section 3.        Employee Inventions and Ideas.
         ---------         -----------------------------

         (a) The Employee will maintain current and adequate written records on
the development of, and disclose to the Company, all Inventions (as defined
herein). "Inventions" shall mean all ideas, potential marketing and sales
relationships, inventions, copyrightable expression, research, plans for
products or services, marketing plans, computer software (including, without
limitation, source code), computer programs, original works of authorship,
characters, know-how, trade secrets, information, data, developments,
discoveries, improvements, modifications, technology, algorithms and designs,
whether or not subject to patent or copyright protection, made, conceived,
expressed, developed, or actually or constructively reduced to practice by the
Employee solely or jointly with others during the term of the Employee's
employment with the Company, which refer to, are suggested by, or result from
any work which the Employee may do during his employment, or from any
information obtained from the Company or any affiliate of the Company.

         (b) The Inventions shall be the exclusive property of the Company, and
the Employee acknowledges that all of said Inventions shall be considered as
"work made for hire" belonging to the Company. To the extent that any such
Inventions, under applicable law, may not be considered work made for hire by
the Employee for the Company, the Employee hereby agrees to assign and, upon its
creation, automatically and irrevocably assigns to the Company, without any
further consideration, all right, title and interest in and to such materials,
including, without limitation, any copyright, other intellectual property
rights, moral rights, all contract and licensing rights, and all claims and
causes of action of any kind with respect to such materials. The Company shall
have the exclusive right to use the Inventions, whether original or derivative,
for all purposes without additional compensation to the Employee. At the
Company's expense,
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the Employee will assist the Company in every proper way to perfect the
Company's rights in the Inventions and to protect the Inventions throughout the
world, including, without limitation, executing in favor of the Company or any
designee(s) of Company patent, copyright, and other applications and assignments
relating to the Inventions. The Employee agrees not to challenge the validity of
the ownership by the Company or its designee(s) in the Inventions.

         (c) Should the Company be unable to secure the Employee's signature on
any document necessary to apply for, prosecute, obtain, or enforce any patent,
copyright, or other right or protection relating to any Invention, whether due
to the Employee's mental or physical incapacity or any other cause, the Employee
hereby irrevocably designates and appoints the Company and each of its duly
authorized officers and agents as the Employee's agent and attorney in fact, to
act for and in the Employee's behalf and stead and to execute and file any such
document, and to do all other lawfully permitted acts to further the
prosecution, issuance, and enforcement of patents, copyrights, or other rights
or protections with the same force and effect as if executed and delivered by
the Employee.

         Section 4.        Proprietary Information.
         ---------         -----------------------

         (a) The Employee will not disclose or use, at any time either during or
after the term of employment, except at the request of the Company or an
affiliate of the Company, any Confidential Information (as herein defined).
"Confidential Information" shall mean all Company proprietary information,
technical data, trade secrets, and know-how, including, without limitation,
research, product plans, customer lists, customer preferences, marketing plans
and strategies, software, development, inventions, discoveries, processes,
ideas, formulas, algorithms, technology, designs, drawings, business strategies
and financial data and information, including, but not limited to Inventions,
whether or not marked as "Confidential." "Confidential Information shall also
mean any and all information received by the Company from customers, vendors and
independent contractors of the Company or other third parties subject to a duty
to be kept confidential.

         (b) The Employee hereby acknowledges and agrees that all personal
property, including, without limitation, all books, manuals, records, reports,
notes, contracts, lists, blueprints, and other documents, or materials, or
copies thereof, Confidential Information as defined in Section 4(a) above, and
equipment furnished to or prepared by the Employee in the course of or incident
to his employment, including, without limitation, records and any other
materials pertaining to Inventions, belong to the Company and shall be promptly
returned to the Company upon termination of employment. Following termination,
the Employee will not retain any written or other tangible or electronic
material containing any Confidential Information or information pertaining to
any Invention.

         Section 5.        Limited Agreement Not to Compete.
         ---------         --------------------------------

         (a) While employed by the Company and for a period of nine (9) months
after the termination of the Employee's employment with the Company, the
Employee shall not, directly or indirectly, as an employee, employer,
consultant, agent, principal, partner, manager,

                                      -2-
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stockholder, officer, director, or in any other individual or representative
capacity, engage or participate in any business that is competitive with the
business of the Company. Notwithstanding the foregoing, the Employee may own
less than two percent (2%) of any class of stock or security of any corporation,
which competes with the Company listed on a national securities exchange.

         (b) While employed by the Company and for a period of twelve (12)
months after the termination of the Employee's employment with the Company, the
Employee shall not, directly or indirectly, solicit for employment any person
who was employed by the Company at the time of the Employee's termination from
the Company.

         Section 6. Company Resources. Other than incidental personal use, the
         ----------
Employee may not use any Company equipment for personal purposes without written
permission from the Company. The Employee may not give access to the Company's
offices or files to any person not in the employ of the Company without written
permission of the Company.

         Section 7. Post-Termination Period. Because of the difficulty of
         ---------
establishing when any idea, process or invention is first conceived or developed
by the Employee, or whether it results from access to Confidential Information
or the Company's equipment, facilities, and data, the Employee agrees that any
idea, invention, research, plan for products or services, marketing plan,
computer software (including, without limitation, source code), computer
program, original work of authorship, character, know-how, trade secret,
information, data, developments, discoveries, technology, algorithm, design,
patent or copyright, or any improvement, rights, or claims relating to the
foregoing, shall be presumed to be an Invention if it is conceived, developed,
used, sold, exploited or reduced to practice by the Employee or with the aid of
the Employee within one (1) year after termination of employment. The Employee
can rebut the above presumption if he proves the idea, process or invention (i)
was first conceived or developed after termination of employment, (ii) was
conceived or developed entirely on the Employee's own time without using the
Company's equipment, supplies, facilities, personnel or Confidential
Information, and (iii) did not result from or is not derived directly or
indirectly, from any work performed by the Employee for the Company or from work
performed by another employee of the Company to which the Employee had access.

         Section 8. Injunctive Relief. The Employee agrees that the remedy at
         ---------
law for any breach of the provisions of Section 4, Section 4 or Section 5 of
this Agreement shall be inadequate, the Company will suffer immediate and
irreparable harm, and the Company shall be entitled to injunctive relief in
addition to any other remedy at law which the Company may have.

         Section 9. Severability. In the event any of the provisions of this
         ---------
Agreement shall be held by a court or other tribunal of competent jurisdiction
to be unenforceable, the other provisions of this Agreement shall remain in full
force and effect.

         Section 10.       Survival.  Sections 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
         ----------        --------
11, 12 and 14 and the Addendum survive the termination of this Agreement.

                                      -3-
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         Section 11. Representations and Warranties. The Employee represents and
         ----------
warrants that the Employee is not under any obligation to any third party which
could interfere with the Employee's performance under this Agreement, and that
the Employee's performance of his obligations to the Company during the term of
his employment with the Company will not breach any agreement by which the
Employee is bound not to disclose any proprietary information including, without
limitation, that of former employers; provided that notwithstanding the
foregoing, in the event employee determines that an action which the Company
requests him to pursue would cause him to violate any such agreement, so informs
the Company, and the Company instructs him to proceed with such action,
Employees proceeding with such action shall not be deemed to be a violation of
this representation and warranty.

         Section 12. Governing Law. The validity, interpretation,
         ----------
enforceability, and performance of this Agreement shall be governed by and
construed in accordance with the laws of the State of New York without giving
effect to its conflict of law rules.

         Section 13.       Not Used.
         ----------

         Section 14. General. This Agreement supersedes and replaces any
         ----------
existing agreement between the Employee and the Company relating generally to
the same subject matter, and may be modified only in a writing signed by the
parties hereto. Failure to enforce any provision of the Agreement contains the
entire agreement between the parties with respect to the subject matter herein.
The Employee agrees that he will not assign, transfer, or otherwise dispose of,
whether voluntarily or involuntarily, or by operation of law, any rights or
obligations under this Agreement. Any purported assignment, transfer, or
disposition shall be null and void. Nothing contained in this Agreement shall
prevent the consolidation of the Company with, or its merger into, any other
corporation, or the sale by the Company of all or substantially all of its
properties or assets, or the assignment by the Company of this Agreement and the
performance of its obligations hereunder. Subject to the foregoing, this
Agreement shall be binding upon and shall inure to the benefit of the parties
and their respective heirs, legal representatives, successors, and permitted
assigns, and shall not benefit any person or entity other than those enumerated.

         Section 15. Employee Acknowledgment. The Employee acknowledges (i) that
         ----------
he has consulted with or has had the opportunity to consult with independent
counsel of his own choice concerning this Agreement and has advised to do so by
the Company, and (ii) that he has read and understands the Agreement, is fully
aware of its legal effect, and has entered into it freely based on his own
judgment.

AGREED TO BY:

EARTHWEB INC.                         Scot W. Melland

Sign: _______________________         Sign: _______________________

Date: _______________________         Date: _______________________

                                      -4-
<PAGE>

         Addendum to Employment Agreement -- Scot W. Melland (Employee)
         --------------------------------------------------------------

Section 1

Title and Job Description. The Employee shall be employed on a full-time basis,
as President and Chief Executive Officer of the Company. In such capacity, the
Employee shall be responsible for the day-to-day operation of the Company and
any other responsibilities reasonably assigned by the Company from time to time.
The Employee shall report to the Board of Directors of the Company (the "Board")
and shall serve as a Director on the Board.

The Employee shall be located in EarthWeb's New York offices currently located
in New York City or within 40 miles of New York City.

Section 2

Compensation. In consideration of the services to be rendered hereunder, the
Employee shall be paid an annual base salary of $300,000 per year (prorated for
calendar year 2001). The Employee shall also be eligible for an annual bonus
targeted at 75% of his base salary; provided, however, that the bonus amount for
2001 shall be a minimum of 75% of the base salary paid to the Employee during
2001, with amounts in excess of such percentage in the discretion of the
Compensation Committee of the Board of Directors. Except for the minimum bonus
amount stated in the proviso of the foregoing sentence, bonus compensation will
be determined by the Compensation Committee of the Board of Directors and will
be based on the performance of the Employee and the performance of the Company.

As an inducement for the Employee to accept employment with the Company, the
Employee shall receive 697,391 stock options ("Stock Options") to be granted on
administration dates following the initial date of the Employee's employment
with the Company, of which 600,000 Stock Options shall be awarded pursuant to
the terms and conditions of EarthWeb's 1998 Stock Incentive Plan (the "Stock
Option Plan") and of which 97,391 shall be awarded outside the Stock Option Plan
but on the same terms and conditions as if made thereunder, and in each case,
pursuant to option-granting documents and subject to approval by the Board. The
Stock Options shall vest over four years, with twenty-five percent (25 %)
vesting upon the first anniversary of the grant and six and one-quarter percent
(6 1/4 %) vesting quarterly thereafter.

The Employee shall be eligible for all employee benefits under the Company's
benefit plans in effect from time to time, including health, life, dental,
vision, short-term disability, 401(k) Plan, and Employee Stock Purchase Plan.
The Employee shall be entitled to four weeks of vacation per year.

The Employee's compensation shall be reviewed on at least an annual basis.

                                      -5-
<PAGE>

Section 3

Severance. In lieu of any severance pay or severance benefits otherwise payable
---------
to the Employee under any plan, policy, program or arrangement of the Company or
its subsidiaries, the following shall apply:

(a) If there is a Termination (as herein defined) of the Employee's employment
with the Company at any time prior to a "Change of Control" (as defined herein)
without "Cause" (as defined herein), the Employee shall be entitled to receive a
lump-sum severance payment equal to (i) one hundred percent (100%) of his then
current annual salary plus (ii) the amount of his then current target bonus. The
Employee is then entitled to accelerated vesting with respect to twenty-five
(25%) of his then unvested Stock Options.

(b) If there is a Termination of the Employee's Employment with the Company
following a Change of Control, the Employee shall be entitled to receive a
lump-sum severance payment equal to (i) one hundred percent (100%) of his then
current annual salary plus (ii) the amount of his then current bonus target. If
the Change of Control occurs within the first ninety (90) days of his employment
with the Company, the Employee shall be entitled to accelerated vesting with
respect to thirty-three percent (33%) of his Stock Options. If such Change of
Control occurs between the ninety-first day of the Employee's employment with
the Company and his first anniversary with the Company, he shall be entitled to
accelerated vesting with respect to fifty percent (50%) of his Stock Options. If
the Change of Control occurs after his first anniversary with the Company, he
shall be entitled to accelerated vesting with respect to one-hundred percent
(100%) of his Stock Options.

(c) The Employee, such Employee's spouse and eligible dependents will continue
to be provided with medical and dental benefits for the twelve (12)-month period
following such Employee's Termination on the same basis as provided to active
employees of the Company. Following such twelve (12)-month period, the Employee,
such Employee's spouse and eligible dependents will begin eligibility for
continuation of medical and dental coverage in accordance with Section 4980B of
the Internal Revenue Code of 1986, as amended (the "Code"). The Employee shall
have no duty to mitigate damages by seeking other employment. The Company shall
have no right to offset hereunder with respect to any compensation or benefits
received by the Employee from or in connection with any employment subsequent to
such Employee's Termination of employment with the Company.

Section 4

Definitions.
-----------

(a)           For purposes of this Employment Agreement only, a "Change of
              Control" of the Company shall be deemed to have occurred if at any
              time on or after the date of the Employment Agreement one or more
              of the following events shall have occurred:

              (i) the direct or indirect acquisition by any person or related
                  group of persons (other than an acquisition from or by the
                  Company or by a Company-sponsored employee benefit plan or by
                  a person that directly or indirectly controls, is controlled
                  by, or is under common control with, the Company) of
                  beneficial

                                      -6-
<PAGE>

                  ownership (within the meaning of Rule 13d-3 of the
                  Securities Exchange Act of 1934, as amended (the "Exchange
                  Act")) of securities possessing more than fifty percent (50%)
                  of the total combined voting power of the Company's
                  outstanding securities; or
             (ii) any stockholder-approved transfer or other disposition of all
                  or substantially all of the Company's assets; or
            (iii) the Company adopts any plan of liquidation providing for the
                  distribution of all or substantially all of its assets; or
             (iv) the consummation by the Company of a reorganization, merger or
                  consolidation or sale or other disposition of all or
                  substantially all of the assets of the Company or the
                  acquisition of assets or stock of another corporation (a
                  "Business Combination"), in each case, unless, following such
                  Business Combination, (a) all or substantially all of the
                  individuals and entities who were the beneficial owners,
                  respectively, of the outstanding common stock and outstanding
                  company voting securities immediately prior to such Business
                  Combination beneficially own, directly or indirectly, more
                  than 60% of, respectively, the then outstanding shares of
                  common stock and the combined voting power of the then
                  outstanding voting securities entitled to vote generally in
                  the election of directors, as the case may be, of the
                  corporation resulting from such Business Combination
                  (including, without limitation, a corporation which as a
                  result of such transaction owns the Company or all or
                  substantially all of the Company's assets either directly or
                  through one or more subsidiaries) in substantially the same
                  proportions as their ownership, immediately prior to such
                  Business Combination of the outstanding Company common stock
                  and outstanding Company voting securities, as the case may be,
                  (b) no person (excluding any corporation resulting from such
                  Business Combination or any employee benefit plan (or related
                  trust) of the Company or such corporation resulting from such
                  Business Combination) beneficially owns, directly or
                  indirectly, 20% or more of, respectively, the then outstanding
                  shares of common stock of the corporation resulting from such
                  Business Combination or the combined voting power of the then
                  outstanding voting securities of such corporation except to
                  the extent that such ownership existed prior to the Business
                  Combination and (c) at least a majority of the members of the
                  board of directors of the corporation resulting from such
                  Business Combination were members of the incumbent board at
                  the time of the execution of the initial agreement, or of the
                  action of the board of directors, providing for such Business
                  Combination; or
             (v)  a change in the composition of the Board over a period of
                  thirty-six (36) months or less such that a majority of the
                  Board members (rounded up to the next whole number) ceases, by
                  reason of one or more contested elections for Board
                  membership, to be comprised of individuals who are continuing
                  directors.

     (b)     For purposes of this Employment Agreement only, "Cause" shall mean
             (i) embezzlement by the Employee, (ii) misappropriation by the
             Employee of funds of the Company, (iii) conviction of a felony,

                                      -7-
<PAGE>

             (iv) commission of any other act of dishonesty which causes
             material economic harm to the Company, (v) acts of fraud or deceit
             by the Employee which causes material economic harm to the Company,
             (vi) material breach of any provision of the Employment Agreement
             by the Employee, (vii) willful failure by the Employee to
             substantially perform such Employee's duties hereunder, (viii)
             willful breach of fiduciary duty by the Employee to the Company
             involving personal profit or (ix) significant violation of Company
             policy of which the Employee is made aware (or such Employee should
             reasonably be expected to be aware) or other contractual, statutory
             or common law duties to the Company. No act, or failure to act on
             the part of the Employee, shall be deemed willful unless it is
             done, or omitted to be done, by the Employee in bad faith or
             without reasonable belief that the Employee's action or omission
             was in the best interests of the Company.

     (c)     For purposes of this Employment Agreement only, "Good Reason" shall
             mean (i) a diminution in the responsibilities, title, duties and
             reporting lines of the Employee compared to those existing
             immediately prior to a Change of Control, (ii) a reduction in
             salary, incentive compensation and other employee benefits of the
             Employee compared to those existing immediately prior to the Change
             of Control, (iii) relocation of the Employee to an office more than
             40 miles from the principal office at which the Employee is
             employed immediately prior to the Change of Control, (iv) any
             breach by the Company of the Employment Agreement or (v) the
             failure of any successor to assume, in writing, all obligations
             under the Employment Agreement.

     (d)     For purposes of this Employment Agreement only, "Termination" shall
             mean termination of the Employee's employment without Cause or by
             the Employee for Good Reason.

Section 5

Excise Tax. In the event that the Employee becomes entitled to the payments and
benefits provided in Section 3 (the "Severance Payments") of this Addendum to
the Employment Agreement, if any of the Severance Payments will be subject to
the excise tax (the "Excise Tax") imposed under Section 4999 of the Code, the
Company shall pay to the Employee an additional amount (the "Gross-Up Payment")
such that the net amount retained by the Employee, after deduction of any Excise
Tax on the Severance Payments and any Federal, state and local income and
employment tax and Excise Tax upon the payments and benefits provided for by
Section 5 of this Addendum to the Employment Agreement, shall be equal to the
Severance Payments. For purposes of determining whether any of the Severance
Payments will be subject to the Excise Tax and the amount of such Excise Tax,
(i) any other payments or benefits received or to be received by the Employee in
connection with a change in ownership or control (within the meaning of section
280G of the Code and the regulations promulgated thereunder) of the Company or
the Employee's termination of employment by the Company without Cause or by the
Employee for Good Reason (whether pursuant to the terms of the Employment
Agreement or any other plan, arrangement or agreement with the Company, any
person whose actions result in a change of control or any person affiliated with
the Company or such person) shall be treated as "parachute payments" within the
meaning of section 280G(b)(2) of the Code, and all "excess parachute payment"
within the meaning of section 280G(b)(1) of the Code shall be treated as subject
to the Excise Tax, unless in the opinion of tax counsel selected by the
Company's'

                                      -8-
<PAGE>

independent auditors and reasonably acceptable to the Employee such
other payments or benefits (in whole or in part) do not constitute parachute
payments, including by reason of Section 280G(b)(4)(A) of the Code, or such
excess parachute payments (in whole or in part) represent reasonable
compensation for services actually rendered, within the meaning of section
280G(b)(4)(B) of the Code, in excess of the "base amount" allocable to such
reasonable compensation, or are otherwise not subject to the Excise Tax, (ii)
the amount of the Severance Payments which shall be treated as subject to the
Excise Tax shall be equal to the lesser of (A) the total amount of the Severance
Payments or (B) the amount of excess parachute payments within the meaning of
section 280G(b)(1) of the Code (after applying clause (i), above), and (iii) the
value of any non-cash benefits or any deferred payment or benefit shall be
determined by the Company's independent auditors in accordance with the
principles of sections 280G(d)(3) and (4) of the Code. For purposes of
determining the amount of the Gross-Up Payment, the Employee shall be deemed to
pay Federal income taxes at the highest marginal rate of Federal income taxation
in the calendar year in which the Gross-Up Payment is to be made and state and
local income taxes at the highest marginal rate of taxation in the state and
locality of the Employee's residence on the date of termination, net of the
maximum reduction in Federal income taxes which could be obtained from the
deduction of such state and local taxes.

Section 6

All amounts payable hereunder shall be subject to and paid net of, all required
withholding taxes.

AGREED TO BY:

EARTHWEB INC.                             Scot W. Melland

Sign: _______________________             Sign: _______________________

Date: _______________________             Date: _______________________

                                      -9-<PAGE>
                                                                    Exhibit 4.13

             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:

               (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

<PAGE>

          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.

          (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

<PAGE>

     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

               (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

<PAGE>

     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 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

<PAGE>

     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.

     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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