SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                  SCHEDULE 13D

                    Under the Securities Exchange Act of 1934
                               (Amendment No. 2)*

                                CABOT CORPORATION
                                (Name of Issuer)

                     COMMON STOCK, PAR VALUE $1.00 PER SHARE
                         (Title of Class of Securities)

                                    127055101
                                 (CUSIP Number)

                               SPO Advisory Corp.
                         591 Redwood Highway, Suite 3215
                          Mill Valley, California 94941
                                 (415) 383-6600

                                 with a copy to:

                                Alison S. Ressler
                             Sullivan & Cromwell LLP
                             1888 Century Park East
                       Los Angeles, California 90067-1725
                                 (310) 712-6600

           (Name, Address and Telephone Number of Person Authorized to
                       Receive Notices and Communications)

                                 SEPTEMBER 22, 2005
             (Date of Event which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
Schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following
box |_|.

Note. Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

Page 2 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON SPO Partners II, L.P. - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS WC - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER 5,427,200 (1) ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By -0- Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER 5,427,200 (1) ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,427,200 (1) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.75% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON PN - -------------------------------------------------------------------------------- (1) Power is exercised through its sole general partner, SPO Advisory Partners, L.P.

Page 3 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON SPO Advisory Partners, L.P. - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS Not Applicable - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER 5,427,200 (1)(2) ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By -0- Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER 5,427,200 (1)(2) ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,427,200 (1)(2) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.75% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON PN - -------------------------------------------------------------------------------- (1) Solely in its capacity as the sole general partner of SPO Partners II, L.P. (2) Power is exercised through its sole general partner, SPO Advisory Corp.

Page 4 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON San Francisco Partners II, L.P. - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS WC - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION California - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER 309,400 (1) ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By -0- Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER 309,400 (1) ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 309,400 (1) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 0.5% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON PN - -------------------------------------------------------------------------------- (1) Power is exercised through its sole general partner, SF Advisory Partners, L.P.

Page 5 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON SF Advisory Partners, L.P. - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS Not Applicable - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER 309,400 (1)(2) ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By -0- Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER 309,400 (1)(2) ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 309,400 (1)(2) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 0.5% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON PN - -------------------------------------------------------------------------------- (1) Solely in its capacity as the sole general partner of San Francisco Partners II, L.P. (2) Power is exercised through its sole general partner, SPO Advisory Corp.

Page 6 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON SPO Advisory Corp. - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS Not Applicable - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER 5,736,600 (1)(2) ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By -0- Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER 5,736,600 (1)(2) ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,736,600 (1)(2) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 9.25% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON CO - -------------------------------------------------------------------------------- (1) Solely in its capacity as the sole general partner of SPO Advisory Partners, L.P. with respect to 5,427,200 of such shares; and solely in its capacity as the sole general partner of SF Advisory Partners, L.P. with respect to 309,400 of such shares. (2) Power is exercised through its three controlling persons, John H. Scully, William E. Oberndorf and William J. Patterson.

Page 7 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON John H. Scully - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS Not Applicable - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION USA - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER -0- ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By 5,736,600 (1) Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER -0- ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER 5,736,600 (1) - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,736,600 (1) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 9.25% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON IN - -------------------------------------------------------------------------------- (1) These shares may be deemed to be beneficially owned by Mr. Scully solely in his capacity as one of three controlling persons of SPO Advisory Corp.

Page 8 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON William E. Oberndorf - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS Not Applicable - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION USA - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER -0- ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By 5,736,600 (1) Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER -0- ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER 5,736,600 (1) - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,736,600 (1) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 9.25% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON IN - -------------------------------------------------------------------------------- (1) These shares may be deemed to be beneficially owned by Mr. Oberndorf solely in his capacity as one of three controlling persons of SPO Advisory Corp.

Page 9 of 25 pages CUSIP No. 127055101 - -------------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON William J. Patterson - -------------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) |_| (b) |X| - -------------------------------------------------------------------------------- 3. SEC Use Only - -------------------------------------------------------------------------------- 4. SOURCE OF FUNDS Not Applicable - -------------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(e) OR 2(f) |_| - -------------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION USA - -------------------------------------------------------------------------------- 7. SOLE VOTING POWER -0- ------------------------------------------------------ Number Of Shares 8. SHARED VOTING POWER Beneficially Owned By 5,736,600 (1) Each Reporting Person ------------------------------------------------------ With 9. SOLE DISPOSITIVE POWER -0- ------------------------------------------------------ 10. SHARED DISPOSITIVE POWER 5,736,600 (1) - -------------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,736,600 (1) - -------------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES |_| - -------------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 9.25% - -------------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON IN - -------------------------------------------------------------------------------- (1) These shares may be deemed to be beneficially owned by Mr. Patterson solely in his capacity as one of three controlling persons of SPO Advisory Corp.

Page 10 of 25 pages This Amendment No. 2 amends the Schedule 13D (the "Original 13D") filed with the Securities and Exchange Commission ("SEC") on August 29, 2005 and as amended on September 14, 2005. Unless otherwise stated herein, the Original 13D, as previously amended, remains in full force and effect. Terms used herein and not defined herein shall have the meanings ascribed thereto in the Original 13D. ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION. Item 3 is hereby amended and restated in its entirety as follows: The source and amount of the funds used or to be used by the Reporting Persons to purchase Shares are as follows: NAME SOURCE OF FUNDS AMOUNT OF FUNDS - --------------------- --------------------------- --------------- SPO Contributions from Partners $175,600,163 SPO Advisory Partners Not Applicable Not Applicable SFP Contributions from Partners $10,038,218 SF Advisory Partners Not Applicable Not Applicable SPO Advisory Corp. Not Applicable Not Applicable JHS Not Applicable Not Applicable WEO Not Applicable Not Applicable WJP Not Applicable Not Applicable ITEM 5. INTEREST IN SECURITIES OF THE ISSUER. Item 5 is hereby amended and restated in its entirety as follows: (a) Percentage interest calculations for each Reporting Person are based upon the Issuer having 62,030,447 total outstanding shares of Common Stock as reported on the Issuer's 10-Q filed with the Securities and Exchange Commission on August 9, 2005. SPO The aggregate number of Shares that SPO owns beneficially, pursuant to Rule 13d-3 of the Act, is 5,427,200 Shares, which constitutes approximately 8.75% of the outstanding Shares. SPO Advisory Partners Because of its position as the sole general partner of SPO, SPO Advisory Partners may, pursuant to Rule 13d-3 of the Act, be deemed to be the beneficial owner of 5,427,200 Shares, which constitutes approximately 8.75% of the outstanding Shares.

Page 11 of 25 pages SFP The aggregate number of Shares that SFP owns beneficially, pursuant to Rule 13d-3 of the Act, is 309,400 Shares, which constitutes approximately 0.5% of the outstanding Shares. SF Advisory Partners Because of its position as the sole general partner of SFP, SF Advisory Partners may, pursuant to Rule 13d-3 of the Act, be deemed to be the beneficial owner of 309,400 Shares, which constitutes approximately 0.5% of the outstanding Shares. SPO Advisory Corp. Because of its positions as the sole general partner of each of SPO Advisory Partners and SF Advisory Partners, SPO Advisory Corp. may, pursuant to Rule 13d-3 of the Act, be deemed to be the beneficial owner of 5,736,600 Shares in the aggregate, which constitutes approximately 9.25% of the outstanding Shares. JHS Because of his position as a control person of SPO Advisory Corp., JHS may, pursuant to Rule 13d-3 of the Act, be deemed to be the beneficial owner of 5,736,600 Shares, which constitutes approximately 9.25% of the outstanding Shares. WEO Because of his position as a control person of SPO Advisory Corp., WEO may, pursuant to Rule 13d-3 of the Act, be deemed to be the beneficial owner of 5,736,600 Shares, which constitutes approximately 9.25% of the outstanding Shares. WJP Because of his position as a control person of SPO Advisory Corp., WJP may, pursuant to Rule 13d-3 of the Act, be deemed to be the beneficial owner of 5,736,600 Shares, which constitutes approximately 9.25% of the outstanding Shares. To the best of the knowledge of each of the Reporting Persons, other than as set forth above, none of the persons named in Item 2 hereof is the beneficial owner of any Shares. (b) SPO Acting through its sole general partner, SPO has the sole power to vote or to direct the vote and to dispose or to direct the disposition of 5,427,200 Shares.

Page 12 of 25 pages SPO Advisory Partners Acting through its sole general partner and in its capacity as the sole general partner of SPO, SPO Advisory Partners has the sole power to vote or to direct the vote and to dispose or to direct the disposition of 5,427,200 Shares. SFP Acting through its sole general partner, SFP has the sole power to vote or to direct the vote and to dispose or to direct the disposition of 309,400 Shares. SF Advisory Partners Acting through its sole general partner and in its capacity as the sole general partner of SFP, SF Advisory Partners has the sole power to vote or to direct the vote and to dispose or to direct the disposition of 309,400 Shares. SPO Advisory Corp. Acting through its controlling persons and in its capacities as the sole general partner of each of SPO Advisory Partners and SF Advisory Partners, SPO Advisory Corp. has the sole power to vote or to direct the vote and to dispose or to direct the disposition of 5,736,600 Shares in the aggregate. JHS As one of three controlling persons of SPO Advisory Corp., which is the sole general partner of each of SPO Advisory Partners and SF Advisory Partners, JHS may be deemed to have shared power with WEO and WJP to vote or to direct the vote and to dispose or to direct the disposition of 5,736,600 Shares held by SPO and SFP in the aggregate. WEO As one of three controlling persons of SPO Advisory Corp., which is the sole general partner of each of SPO Advisory Partners and SF Advisory Partners, WEO may be deemed to have shared power with JHS and WJP to vote or to direct the vote and to dispose or to direct the disposition of 5,736,600 Shares held by SPO and SFP in the aggregate. WJP As one of three controlling persons of SPO Advisory Corp., which is the sole general partner of each of SPO Advisory Partners and SF Advisory Partners, WJP may be deemed to have shared power with JHS and WEO to vote or to direct the vote and to dispose or to direct the disposition of 5,736,600 Shares held by SPO and SFP in the aggregate. (c) Since the most recent filing on Schedule 13D, the Reporting Persons purchased Shares in open market transactions as set forth on Schedule I attached hereto.

Page 13 of 25 pages Except as set forth in this paragraph (c), to the best of the knowledge of each of the Reporting Persons, none of the persons named in response to paragraph (a) has effected any transactions in Shares during the past 60 days. (d) Each of the Reporting Persons affirms that no person other than such Reporting Person has the right to receive or the power to direct the receipt of distributions with respect to, or the proceeds from the sale of, Shares owned by such Reporting Person. (e) Not applicable. ITEM 7. MATERIAL TO BE FILED AS EXHIBITS. Item 7 is hereby amended and restated in its entirety as follows: Exhibit A: Agreement pursuant to Rule 13d-1(k)

Page 14 of 25 pages SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Dated September 26, 2005 By: /s/ Kim M. Silva -------------------------------- Kim M. Silva Attorney-in-Fact for: SPO PARTNERS II, L.P.(1) SPO ADVISORY PARTNERS, L.P.(1) SAN FRANCISCO PARTNERS II, L.P.(1) SF ADVISORY PARTNERS, L.P.(1) SPO ADVISORY CORP.(1) JOHN H. SCULLY(1) WILLIAM E. OBERNDORF(1) WILLIAM J. PATTERSON(1) (1) A Power of Attorney authorizing Kim M. Silva to act on behalf of this person or entity has been previously filed with the Securities and Exchange Commission.

Page 15 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/15/2005 Buy 95 31.82 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 95 31.83 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 380 31.84 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 6,080 31.85 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 96,950 31.90 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 1,045 31.95 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 1,045 31.96 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 1,710 31.97 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 1,045 31.98 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 5,320 31.99 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 3,610 32.00 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 475 32.01 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 285 32.02 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 570 32.03 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 665 32.04 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 855 32.05 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 665 32.06 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 2,375 32.07 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 380 32.08 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 190 32.09 Open Market/Broker SPO Partners II, L.P. 9/15/2005 Buy 665 32.10 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 5 31.82 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 5 31.83 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 20 31.84 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 320 31.85 Open Market/Broker

Page 16 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- San Francisco Partners, L.P. 9/15/2005 Buy 5,050 31.90 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 55 31.95 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 55 31.96 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 90 31.97 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 55 31.98 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 280 31.99 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 190 32.00 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 25 32.01 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 15 32.02 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 30 32.03 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 35 32.04 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 45 32.05 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 35 32.06 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 125 32.07 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 20 32.08 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 10 32.09 Open Market/Broker San Francisco Partners, L.P. 9/15/2005 Buy 35 32.10 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 950 31.78 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 855 31.79 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 1,140 31.80 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 1,615 31.81 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 1,520 31.83 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 285 31.84 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 1,805 31.85 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 9,500 31.86 Open Market/Broker

Page 17 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/16/2005 Buy 285 31.87 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 2,280 31.88 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 1,710 31.89 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 14,725 31.90 Open Market/Broker SPO Partners II, L.P. 9/16/2005 Buy 47,530 32.00 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 50 31.78 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 45 31.79 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 60 31.80 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 85 31.81 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 80 31.83 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 15 31.84 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 95 31.85 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 500 31.86 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 15 31.87 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 120 31.88 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 90 31.89 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 775 31.90 Open Market/Broker San Francisco Partners, L.P. 9/16/2005 Buy 2,470 32.00 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 700 31.55 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,500 31.57 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 2,400 31.58 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 700 31.59 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 700 31.60 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,600 31.61 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,000 31.63 Open Market/Broker

Page 18 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/19/2005 Buy 1,700 31.64 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 900 31.66 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 2,200 31.69 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,800 31.70 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,000 31.71 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 200 31.72 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,000 31.73 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 800 31.74 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 5,600 31.75 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 6,100 31.76 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 900 31.77 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,900 31.78 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 2,500 31.79 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 2,600 31.80 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 2,100 31.81 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 100 31.82 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,300 31.83 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 2,100 31.84 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 24,900 31.85 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,200 31.86 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 700 31.87 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 300 31.88 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 800 31.89 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 100,800 31.90 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,000 31.91 Open Market/Broker

Page 19 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/19/2005 Buy 700 31.92 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 400 31.95 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 1,000 31.99 Open Market/Broker SPO Partners II, L.P. 9/19/2005 Buy 2,300 32.00 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 2,200 31.26 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,000 31.27 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 3,300 31.28 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 200 31.29 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,500 31.30 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 300 31.31 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,100 31.32 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 400 31.33 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 500 31.34 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,900 31.35 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 800 31.36 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,500 31.39 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 800 31.40 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,100 31.41 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,000 31.42 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 6,000 31.43 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 2,400 31.44 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,900 31.45 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 2,400 31.46 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 6,700 31.47 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 3,500 31.49 Open Market/Broker

Page 20 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/20/2005 Buy 3,100 31.51 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 400 31.52 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 3,100 31.54 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 800 31.55 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 700 31.57 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 600 31.58 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 400 31.64 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 300 31.69 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,000 31.71 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 700 31.72 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 700 31.73 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 4,400 31.74 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 12,300 31.75 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,600 31.76 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,600 31.77 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 3,000 31.78 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 4,200 31.79 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 3,300 31.80 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 400 31.81 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 300 31.82 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 700 31.84 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 200 31.85 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 100 31.87 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,900 31.88 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 2,400 31.90 Open Market/Broker

Page 21 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/20/2005 Buy 200 31.93 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 800 31.94 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 400 31.95 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 900 31.96 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,100 31.97 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 1,800 31.98 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 3,500 31.99 Open Market/Broker SPO Partners II, L.P. 9/20/2005 Buy 2,600 32.00 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 700 31.15 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 400 31.16 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 300 31.17 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 100 31.19 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 600 31.20 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 700 31.21 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 400 31.22 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 300 31.23 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 700 31.24 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 400 31.26 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 400 31.27 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 100 31.29 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 1,800 31.30 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 1,800 31.31 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 1,700 31.32 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 1,400 31.33 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 200 31.34 Open Market/Broker

Page 22 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/21/2005 Buy 76,300 31.35 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 100 31.37 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 1,700 31.40 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 3,100 31.41 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 8,600 31.42 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 1,500 31.43 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 400 31.44 Open Market/Broker SPO Partners II, L.P. 9/21/2005 Buy 14,800 31.45 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 2,500 31.15 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 300 31.16 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 1,100 31.17 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 400 31.18 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 400 31.19 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 1,500 31.20 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 800 31.22 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 400 31.23 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 600 31.24 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 19,300 31.25 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 100 31.28 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 1,700 31.29 Open Market/Broker SPO Partners II, L.P. 9/22/2005 Buy 10,500 31.30 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 1,100 31.02 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 600 31.05 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 1,100 31.06 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 800 31.07 Open Market/Broker

Page 23 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/23/2005 Buy 600 31.08 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 800 31.09 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 2,300 31.10 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 1,100 31.11 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 200 31.13 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 2,100 31.14 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 1,100 31.15 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 800 31.16 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 1,300 31.20 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 2,000 31.21 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 2,100 31.22 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 3,600 31.23 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 100 31.24 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 2,600 31.25 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 600 31.26 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 1,000 31.27 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 700 31.29 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 1,000 31.31 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 300 31.32 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 900 31.33 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 18,300 31.35 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 400 31.37 Open Market/Broker SPO Partners II, L.P. 9/23/2005 Buy 400 31.39 Open Market/Broker

Page 24 of 25 pages SCHEDULE I TO SCHEDULE 13D DATE OF PRICE PER WHERE/HOW TRANSACTION REPORTING PERSON TRANSACTION TYPE NUMBER OF SHARES SHARE ($) EFFECTED - ---------------------------- ---------- ---- ---------------- --------- ---------------------- SPO Partners II, L.P. 9/26/2005 Buy 1,600 31.53 Open Market/Broker SPO Partners II, L.P. 9/26/2005 Buy 4,400 31.54 Open Market/Broker SPO Partners II, L.P. 9/26/2005 Buy 2,100 31.55 Open Market/Broker SPO Partners II, L.P. 9/26/2005 Buy 4,700 31.56 Open Market/Broker SPO Partners II, L.P. 9/26/2005 Buy 14,800 31.57 Open Market/Broker SPO Partners II, L.P. 9/26/2005 Buy 4,400 31.58 Open Market/Broker SPO Partners II, L.P. 9/26/2005 Buy 1,700 31.59 Open Market/Broker SPO Partners II, L.P. 9/26/2005 Buy 8,800 31.60 Open Market/Broker

Page 25 of 25 pages EXHIBIT INDEX EXHIBIT DOCUMENT DESCRIPTION PAGE NO. - ------- ------------------------------------ -------- A Agreement Pursuant to Rule 13d-1(k) 1

                                    EXHIBIT A

         Pursuant to Rule 13d-1(k) of Regulation 13D-G of the General Rules and
Regulations of the Securities and Exchange Commission under the Securities
Exchange Act of 1934, as amended, the undersigned agrees that the statement to
which this Exhibit is attached is filed on behalf of each of them in the
capacities set forth below.


Dated: September 26, 2005                  By:     /s/ Kim M. Silva
                                               --------------------------------
                                                   Kim M. Silva

                                           Attorney-in-Fact for:

                                           SPO PARTNERS II, L.P.(1)
                                           SPO ADVISORY PARTNERS, L.P.(1)
                                           SAN FRANCISCO PARTNERS II, L.P.(1)
                                           SF ADVISORY PARTNERS, L.P.(1)
                                           SPO ADVISORY CORP.(1)
                                           JOHN H. SCULLY(1)
                                           WILLIAM E. OBERNDORF(1)
                                           WILLIAM J. PATTERSON(1)

                                           (1) A Power of Attorney
                                           authorizing Kim M. Silva to
                                           act on behalf of this
                                           person or entity has been previously
                                           filed with the Securities and
                                           Exchange Commission.