<PAGE>

                                                                     Exhibit 4.5

                                 FIRST AMENDMENT
                                       TO
                           SECOND AMENDED AND RESTATED
                        AGREEMENT OF LIMITED PARTNERSHIP
                                       OF
                        CABOT INDUSTRIAL PROPERTIES, L.P.

            THIS FIRST AMENDMENT TO SECOND AMENDED AND RESTATED AGREEMENT OF
LIMITED PARTNERSHIP (this "Amendment") dated as of April 29, 1999, is entered
into by CABOT INDUSTRIAL TRUST, a Maryland real estate investment trust, as
general partner (the "General Partner") of CABOT INDUSTRIAL PROPERTIES, L.P.
(the "Partnership"), for itself and on behalf of the limited partners of the
Partnership, and BELAIR REAL ESTATE CORPORATION ("Belair") and BELCREST REALTY
CORPORATION ("Belcrest").

            WHEREAS, Section 4.2(a) of the Second Amended and Restated Agreement
of Limited Partnership of the Partnership (the "Partnership Agreement")
authorizes the General Partner to cause the Partnership to issue additional
Partnership Units in one or more classes or series, with such designations,
preferences and relative, participating, optional or other special rights,
powers and duties as shall be determined by the General Partner, subject to the
provisions of such section; and

            WHEREAS, pursuant to the authority granted to the General Partner
pursuant to Sections 4.2(a) and 14.1(b) of the Partnership Agreement, the
General Partner desires to amend the Partnership Agreement (i) to establish a
new class of Partnership Units, the Series B Preferred Units (as hereinafter
defined), and to set forth the designations, rights, powers, preferences and
duties of such Series B Preferred Units, (ii) to issue the Series B Preferred
Units to Belair and Belcrest and admit Belair and Belcrest as Additional Limited
Partners and (iii) to make certain other changes to the Partnership Agreement.

            NOW, THEREFORE, in consideration of good and valuable consideration,
the receipt and sufficiency of which hereby are acknowledged, the General
Partner hereby amends the Partnership Agreement as follows:

            Section 1. Definitions. For purposes of this Amendment, the term
"Parity Preferred Units" shall be used to refer to any class or series of
Partnership Interests of the Partnership now or hereafter authorized, issued or
outstanding expressly designated by the Partnership to rank on a parity with
Series B Preferred Units with respect to distributions and rights upon voluntary
or involuntary liquidation, winding-up or dissolution of the Partnership. The
term "Priority Return" shall mean, an amount equal to 8.625% per annum,
determined on the basis of a 360 day year of twelve 30 day months, cumulative to
the extent not distributed for any given distribution period pursuant to Section
5.1 of the Partnership Agreement, of the stated
<PAGE>

value of $50 per Series B Preferred Unit, commencing on the date of issuance of
such Series B Preferred Unit. The term "Subsidiary" shall mean with respect to
any person, any corporation, partnership, limited liability company, joint
venture or other entity of which a majority of (i) voting power of the voting
equity securities or (ii) the outstanding equity interests, is owned, directly
or indirectly, by such person. The term "PTP" shall mean a "publicly traded
partnership" within the meaning of Section 7704 of the Code. Capitalized terms
used herein and not otherwise defined herein shall have the meanings ascribed to
them in the Partnership Agreement.

            Section 2. Designation and Number. A series of Partnership Units in
the Partnership designated as the "8.625% Series B Cumulative Redeemable
Preferred Units" (the "Series B Preferred Units") is hereby established. The
number of Series B Preferred Units shall be 1,300,000.

            Section 3. Distributions. (a) Payment of Distributions. Subject to
the rights of holders of Parity Preferred Units as to the payment of
distributions, pursuant to Section 5.1 of the Partnership Agreement, holders of
Series B Preferred Units shall be entitled to receive, when, as and if declared
by the Partnership acting through the General Partner, out of Available Cash,
cumulative preferential cash distributions at the rate per annum of 8.625% of
the original Capital Contribution per Series B Preferred Unit. In the event that
on or prior to December 31, 1999 (i) the General Partner's senior unsecured debt
shall have an unconditional, published, Standard & Poor's rating of at least
"BBB" and (ii) neither Moody's nor any other rating agency with offices located
in at least five (5) cities in the United States shall have in effect an
unconditional, published, rating of the General Partner's senior unsecured debt
which is lower than its rating for such senior unsecured debt as of the date
hereof, then beginning on the date on which each of such foregoing conditions
are met, the rate per annum shall be 8.50% of the original Capital Contribution
per Series B Preferred Unit, in which case the designation of the Series B
Preferred Units will change accordingly to reflect such new distribution rate;
provided, that, if (y) either Moody's or any other rating agency with offices
located in at least five (5) cities in the United States shall have in effect on
December 31, 1999 an unconditional published rating of the General Partner's
senior unsecured debt which is lower than its rating of such senior unsecured
debt as of the date hereof or (z) a Standard & Poor's rating of at least "BBB"
shall no longer be in effect on December 31, 1999, then the revised rate herein
provided shall be void ab initio and the General Partner shall pay on December
31, 1999, in addition to the distribution due to the holders of the Series B
Preferred Units, the difference between (1) the dividend that would have accrued
at the original rate of 8.625% per annurn during the current and any prior
quarterly distribution period and (2) the distribution that actually accrued
during such distribution periods at the voided rate of 8.50% per annum. Promptly
after January 1, 2000 the parties hereto shall execute, acknowledge and deliver
or cause to be executed acknowledged and delivered all instruments and documents
as may be reasonably necessary or desirable to memorialize the revised
distribution rate. Such distributions shall be cumulative, shall accrue from the
original date of issuance and will be payable (i) quarterly in arrears, on March
31, June 30, September 30 and December 31 of each year commencing on June 30,
1999 and, (ii), in the event of (A) an exchange of Series B Preferred Units into
Series B Preferred Shares, or (B) a redemption of

                                       2
<PAGE>

Series B Preferred Units, on the exchange date or redemption date, as applicable
(each a "Preferred Unit Distribution Payment Date"). The amount of the
distribution payable for any period will be computed on the basis of a 360-day
year of twelve 30-day months and for any period shorter than a full quarterly
period for which distributions are computed, the amount of the distribution
payable will be computed on the basis of the actual number of days elapsed in
such period. If any date on which distributions are to be made on the Series B
Preferred Units is not a Business Day (as defined herein), then payment of the
distribution to be made on such date will be made on the next succeeding day
that is a Business Day (and without any interest or other payment in respect of
any such delay) except that, if such Business Day is in the next succeeding
calendar year, such payment shall be made on the immediately preceding Business
Day, in each case with the same force and effect as if made on such date.
Distributions on the Series B Preferred Units will be made to the holders of
record of the Series B Preferred Units on the relevant record dates to be fixed
by the Partnership acting through the General Partner, which record dates shall
in no event exceed fifteen (15) Business Days prior to the relevant Preferred
Unit Distribution Payment Date (the "Preferred Unit Partnership Record Date").

            The term "Business Day" shall mean each day other than a Saturday or
a Sunday, which is not a day on which banking institutions in New York, New York
are authorized or required by law, regulations or executive order to close.

      (b) Distributions Cumulative. Distributions on the Series B Preferred
Units will accrue whether or not the terms and provisions of any agreement of
the Partnership, including any agreement relating to its indebtedness at any
time prohibit the current payment of distributions, whether or not the
Partnership has earnings, whether or not there are funds legally available for
the payment of such of such distributions and whether or not such distributions
are authorized. Accrued but unpaid distributions on the Series B Preferred Units
will accumulate as of the Preferred Unit Distribution Payment Date on which they
first become payable. Distributions on account of arrears for any past
distribution periods may be declared and paid at any time, without reference to
a regular Preferred Unit Distribution Payment Date to holders of record of the
Series B Preferred Units on the record date fixed by the Partnership acting
through the General Partner which date shall not exceed fifteen (15) Business
Days prior to the payment date. Accumulated and unpaid distributions will not
bear interest.

      (c) Priority as to Distributions. (i) So long as any Series B Preferred
Units are outstanding, no distribution of cash or other property shall be
authorized, declared, paid or set apart for payment on or with respect to any
class or series of Partnership Interest of the Partnership ranking junior as to
the payment of distributions or rights upon a voluntary or involuntary
liquidation, dissolution or winding-up of the Partnership to the Series B
Preferred Units (collectively, "Junior Units"), nor shall any cash or other
property be set aside for or applied to the purchase, redemption or other
acquisition for consideration of any Series B Preferred Units, any Parity
Preferred Units or any Junior Units, unless, in each case, all distributions
accumulated on all Series B Preferred Units and all classes and series of
outstanding Parity Preferred Units have been paid in full. The foregoing
sentence will not prohibit (a) distributions payable solely in Partnership Units
ranking junior to the Series B Preferred Units as

                                       3
<PAGE>

to distributions and upon liquidation, winding-up or dissolution, (b) the
conversion of Junior Units or Parity Preferred Units into Partnership Units
ranking junior to the Series B Preferred Units as to distributions and upon
liquidation, winding-up or dissolution or (c) the redemption of Partnership
Interests corresponding to any Series B Preferred Shares (as hereinafter
defined), Parity Preferred Shares (as such term is defined in the Charter) or
Junior Shares (as such term is defined in the Charter) to be purchased by the
General Partner pursuant to Article 3 of the Declaration of Trust of the General
Partner (the "Charter") to preserve the General Partner's status as a real
estate investment trust, provided that such redemption shall be upon the same
terms as the corresponding purchase pursuant to Article 3 of the Charter.

            (ii) So long as distributions have not been paid in full (or a sum
sufficient for such full payment is not irrevocably deposited in trust for
payment) upon the Series B Preferred Units, all distributions authorized and
declared on the Series B Preferred Units and all classes or series of
outstanding Parity Preferred Units shall be authorized and declared so that the
amount of distributions authorized and declared per Series B Preferred Unit and
such other classes or series of Parity Preferred Units shall in all cases bear
to each other the same ratio that accrued distributions per Series B Preferred
Unit and such other classes or series of Parity Preferred Units (which shall not
include any accumulation in respect of unpaid distributions for prior
distribution periods if such class or series of Parity Preferred Units do not
have cumulative distribution rights) bear to each other.

      (d) No Further Rights. Holders of Series B Preferred Units shall not be
entitled to any distributions, whether payable in cash, other property or
otherwise, in excess of the full cumulative distributions described herein.

            Section 4. Allocations. Sections 6.1(a) and 6.1(b)are hereby deleted
and replaced by the following:

      (a) Net Income. After giving effect to the special allocations set forth
in Section 6.2 through Section 6.4 below, Net Income shall be allocated:

            (i)   first, to the General Partner to the extent that Net Losses
                  previously allocated to the General Partner pursuant to
                  Section 6.1(b)(iii) below for all prior taxable years exceed
                  Net Income previously allocated to the General Partner
                  pursuant to this Section 6.1(a)(i) for all prior taxable
                  years,

            (ii)  second, to Partners holding any Partnership Interests that are
                  entitled to any preference in distribution to the extent that
                  Net Losses previously allocated to such holders pursuant to
                  Section 6.1(b)(ii) below for all prior taxable years exceed
                  Net Income previously allocated to such Partners pursuant to
                  this Section 6.1(a)(ii) for all prior taxable years,

            (iii) third, to Partners holding Partnership Units of a class not
                  entitled to

                                       4
<PAGE>

                  preference in distribution to the extent that Net Losses
                  previously allocated to such holders pursuant to Section
                  6.1(b)(i) below for all prior taxable years exceed Net Income
                  previously allocated to such holders pursuant to this Section
                  6.1(a)(iii) for all prior taxable years,

            (iv)  fourth, to Partners holding any Partnership Interests that are
                  entitled to any preference in distribution in accordance with
                  the rights of any such class of Partnership Interests until
                  each such Partnership Interest has been allocated, Net Income
                  equal to the excess of (x) the cumulative amount of preferred
                  distributions such Partners are entitled to receive to the
                  last day of the current taxable year or to the date of
                  redemption or exchange, to the extent such Partnership
                  Interests are redeemed or exchanged during such taxable year,
                  over (y) the cumulative Net Income allocated to such Partners,
                  pursuant to this Section 6.1(a)(iv) for all prior taxable
                  years (and, within each such class, pro rata in proportion to
                  the respective share of such Partnership Interests each
                  Partner holds as of the last day of the period for which such
                  allocation is being made), and

            (v)   fifth, with respect to Partnership Units that are not entitled
                  to any preference in the allocation of Net Income, pro rata to
                  each such class in accordance with the terms of such class
                  (and, within each such class, pro rata in proportion to each
                  Partner's respective share of such Partnership Units as of the
                  last day of the period for which such allocation is being
                  made).

      (b) Net Losses. After giving effect to the special allocations set forth
in Section 6.2 through Section 6.4, Net Losses shall be allocated:

            (i)   first, with respect to classes of Partnership Units that are
                  not entitled to any preference in distribution (including the
                  General Partner Interest), pro rata to each such class in
                  accordance with the terms of such class (and, within such
                  class, pro rata in proportion to each Partner's respective
                  share of such Partnership Units as of the last day of the
                  period for which such allocation is being made) until the
                  Adjusted Capital Account (ignoring for this purpose any
                  amounts a Partner is obligated to contribute to the capital of
                  the Partnership or is deemed obligated to contribute pursuant
                  to Regulations Section 1.704-1(b)(2)(ii)(c)(2)) of each
                  Partner with respect to such Partnership Units is reduced to
                  zero,

            (ii)  second, to the Partners holding any Partnership Interests that
                  are entitled to any preference in distribution in accordance
                  with the rights of any such class of Partnership Interests
                  (and, if there is more than one class of such Partnership
                  Interests, then in the reverse order of their preference in
                  distribution), until the Adjusted Capital Account (modified in
                  the same

                                       5
<PAGE>

                  manner as in clause (i)) of each such Partner with respect to
                  such Partnership Interests is reduced to zero, and

            (iii) third, to the General Partner.

            Section 5. Liquidation Proceeds. (a) Upon voluntary or involuntary
liquidation, dissolution or winding-up of the Partnership, distributions on the
Series B Preferred Units shall be made in accordance with Section 13.2 of the
Partnership Agreement.

      (b) Notice. Written notice of any such voluntary or involuntary
liquidation, dissolution or winding-up of the Partnership, stating the payment
date or dates when, and the place or places where, the amounts distributable in
such circumstances shall be payable, shall be given by (i) fax and (ii) by first
class mail, postage pre-paid, not less than thirty (30) and not more than sixty
(60) days prior to the payment date stated therein, to each record holder of the
Series B Preferred Units at the respective addresses of such holders as the same
shall appear on the transfer records of the Partnership.

      (c) No Further Rights. After payment of the full amount of the liquidating
distributions to which they are entitled, the holders of Series B Preferred
Units will have no right or claim to any of the remaining assets of the
Partnership.

      (d) Consolidation, Merger or Certain Other Transactions. The voluntary
sale, conveyance, lease, exchange or transfer (for cash, shares of stock,
securities or other consideration) of all or substantially all of the property
or assets of the General Partner to, or the consolidation or merger or other
business combination of the Partnership with or into, any corporation, trust,
partnership, limited liability company or other entity (or of any corporation,
trust, partnership, limited liability company or other entity with or into the
Partnership) shall not be deemed to constitute a liquidation, dissolution or
winding-up of the Partnership.

            Section 6. Optional Redemption. (a) Right of Optional Redemption.
The Series B Preferred Units may not be redeemed prior to the fifth (5th)
anniversary of the issuance date. On or after such date, the Partnership shall
have the right to redeem the Series B Preferred Units, in whole or in part, at
any time or from time to time, upon not less than thirty (30) nor more than
sixty (60) days' written notice, at a redemption price, payable in cash, equal
to the Capital Account balance of the holders of Series B Preferred Units (the
"Redemption Price"); provided, however, that no redemption pursuant to this
Section 6 will be permitted if the Redemption Price does not equal or exceed the
original Capital Contribution of such holder plus the cumulative Priority
Return, whether or not declared, to the redemption date to the extent not
previously distributed or distributed pursuant to Section 3(a). If fewer than
all of the outstanding Series B Preferred Units are to be redeemed, the Series B
Preferred Units to be redeemed shall be selected pro rata (as nearly as
practicable without creating factional units).

      (b) Limitation on Redemption. The Partnership may not redeem fewer than
all of the outstanding Series B Preferred Units unless all accumulated and
unpaid distributions have been

                                       6
<PAGE>

paid on all Series B Preferred Units for all quarterly distribution periods
terminating on or prior to the date of redemption.

      (c) Procedures for Redemption. (i) Notice of redemption will be (A) faxed,
and (B) mailed by the Partnership, by certified mail, postage prepaid, not less
than thirty (30) nor more than sixty (60) days prior to the redemption date,
addressed to the respective holders of record of the Series B Preferred Units at
their respective addresses as they appear on the records of the Partnership. No
failure to give or defect in such notice shall affect the validity of the
proceedings for the redemption of any Series B Preferred Units except as to the
holder to whom such notice was defective or not given. In addition to any
information required by law, each such notice shall state: (1) the redemption
date, (2) the Redemption Price, (3) the aggregate number of Series B Preferred
Units to be redeemed and if fewer than all of the outstanding Series B Preferred
Units are to be redeemed, the number of Series B Preferred Units to be redeemed
held by such holder, which number shall equal such holder's pro rata share
(based on the percentage of the aggregate number of outstanding Series B
Preferred Units the total number of Series B Preferred Units held by such holder
represents) of the aggregate number of Series B Preferred Units to be redeemed,
(4) the place or places where such Series B Preferred Units are to be
surrendered for payment of the Redemption Price, (5) that distributions on the
Series B Preferred Units to be redeemed will cease to accumulate on such
redemption date and (6) that payment of the Redemption Price will be made upon
presentation and surrender of such Series B Preferred Units.

            (ii) If the Partnership gives a notice of redemption in respect of
Series B Preferred Units (which notice will be irrevocable) then, by 12:00 noon,
New York City time, on the redemption date, the Partnership will deposit
irrevocably in trust for the benefit of the Series B Preferred Units being
redeemed funds sufficient to pay the applicable Redemption Price and will give
irrevocable instructions and authority to pay such Redemption Price to the
holders of the Series B Preferred Units upon surrender of the Series B Preferred
Units by such holders at the place designated in the notice of redemption. If
the Series B Preferred Units are evidenced by a certificate and if fewer than
all Series B Preferred Units evidenced by any certificate are being redeemed, a
new certificate shall be issued upon surrender of the certificate evidencing all
Series B Preferred Units, evidencing the unredeemed Series B Preferred Units
without cost to the holder thereof. On and after the date of redemption,
distributions will cease to accumulate on the Series B Preferred Units or
portions thereof called for redemption, unless the Partnership defaults in the
payment thereof. If any date fixed for redemption of Series B Preferred Units is
not a Business Day, then payment of the Redemption Price payable on such date
will be made on the next succeeding day that is a Business Day (and without any
interest or other payment in respect of any such delay) except that, if such
Business Day falls in the next calendar year, such payment will be made on the
immediately preceding Business Day, in each case with the same force and effect
as if made on such date fixed for redemption. If payment of the Redemption Price
is improperly withheld or refused and not paid by the Partnership, distributions
on such Series B Preferred Units will continue to accumulate from the original
redemption date to the date of payment, in which case the actual payment date
will be considered the date fixed for redemption for purposes of calculating the
applicable Redemption Price.

                                       7
<PAGE>

            Section 7. Voting Rights. (a) General. Holders of the Series B
Preferred Units will not have any voting rights or right to consent to any
matter requiring the consent or approval of the Limited Partners, except as set
forth in the Partnership Agreement and except as set forth below.

      (b) Certain Voting Rights. So long as any Series B Preferred Units remain
outstanding, the Partnership shall not, without the affirmative vote of the
holders of at least two-thirds of the Series B Preferred Units outstanding at
the time (i) authorize or create, or increase the authorized or issued amount
of, any class or series of Partnership Interests senior to the Series B
Preferred Units with respect to payment of distributions or rights upon
liquidation, dissolution or winding-up of the Partnership or reclassify any
Partnership Interests of the Partnership into any such senior Partnership
Interest, or create, authorize or issue any obligations or security convertible
into or evidencing the right to purchase any such senior Partnership Interests,
authorize or create, or increase the authorized or issued amount of any Parity
Preferred Units or reclassify any Partnership Interest into any such Partnership
Interest or create, (ii) authorize or issue any obligations or security
convertible into or evidencing the right to purchase any such Partnership
Interests but only to the extent such Parity Preferred Units are issued to an
Affiliate of the Partnership, other than the General Partner to the extent the
issuance of such interests was to allow the General Partner to issue
corresponding preferred stock to persons who are not Affiliates of the
Partnership (or to Affiliates purchasing the preferred stock on the same terms
as nonaffiliated purchasers) or (iii) either (A) consolidate, merge into or
with, or convey, transfer or lease all or substantially all of its assets to,
any corporation or other entity or (B) amend, alter or repeal the provisions of
the Partnership Agreement, whether by merger, consolidation or otherwise, that
would materially and adversely affect the powers, special rights, preferences,
privileges or voting power of the Series B Preferred Units or the holders
thereof; provided, however, that with respect to the occurrence of a merger,
consolidation or a sale or lease of all or substantially all of the
Partnership's assets as an entirety, so long as (1) the Partnership is the
surviving entity and the Series B Preferred Units remain outstanding with the
terms thereof unchanged, or (2) the resulting, surviving or transferee entity is
a partnership, limited liability company or other pass-through entity organized
under the laws of any state and substitutes the Series B Preferred Units for
other interests in such entity having substantially the same terms and rights as
the Series B Preferred Units, including with respect to distributions, voting
rights and rights upon liquidation, dissolution or winding-up of the
Partnership, then the occurrence of any such event shall not be deemed to
materially and adversely affect such rights, privileges or voting powers of the
holders of the Series B Preferred Units and no vote of the Series B Preferred
Units shall be required in such case; and provided further that any increase in
the amount of Partnership Interests or the creation or issuance of any other
class or series of Partnership Interests, in each case ranking (y) junior to the
Series B Preferred Units with respect to payment of distributions or the
distribution of assets upon liquidation, dissolution or winding- up of the
Partnership, or (z) on a parity with the Series B Preferred Units with respect
to payment of distributions and the distribution of assets upon liquidation,
dissolution or winding- up of the Partnership to the extent such Partnership
Interests are issued to an affiliate of the Partnership, other than the General
Partner to the extent the issuance of such interests was to

                                       8
<PAGE>

allow the General Partner to issue corresponding preferred stock to persons who
are not affiliates of the Partnership, shall not be deemed to materially and
adversely affect such rights, preferences, privileges or voting powers and no
vote of the Series B Preferred Units shall be required in such case.

            Section 8. Transfer Restrictions. The Series B Preferred Units shall
be subject to the provisions of Article XI of the Partnership Agreement,
provided, however, that (i) the General Partner shall act reasonably in
exercising its discretion pursuant to the provisions of Section 11.4(a)(ii) to
transferees of Series B Preferred Units, (ii) the provisions of Clause B of
Section 11.3(d) shall not be applicable to holders of Series B Preferred Units
if at the time of such transfer, the Partnership already has 100 Partners; (iii)
if only a portion of the Series B Preferred Units shall be transferred, the
transferee of such transferred Series B Preferred Units shall, subject to the
provisions of Section 11.4, be substituted as a Limited Partner in place of the
transferring holders only as to the Series B Preferred Units so transferred; and
(iv) the provisions of Sections 11.6(c) and 11.6(d) shall not be applicable to
any transfer of Series B Preferred Units; and provided further that "transfer"
when used in Article 11 shall not be deemed to include any exchange pursuant to
Section 9 below.

            Section 9. Exchange Rights. (a) Right to Exchange. (i) Series B
Preferred Units will be exchangeable in whole or in part at anytime on or after
the tenth (10th) anniversary of the date of issuance, at the option of the
holders thereof, for authorized but previously unissued shares of 8.625 % Series
B Cumulative Redeemable Preferred Shares of the General Partner (the "Series B
Preferred Shares") at an exchange rate of one Series B Preferred Share for one
Series B Preferred Unit, subject to adjustment as described below (the "Exchange
Price"), provided that the Series B Preferred Units will become exchangeable at
any time, in whole or in part, at the option of the holders of Series B
Preferred Units for Series B Preferred Shares if (y) at any time full
distributions shall not have been timely made on any Series B Preferred Unit
with respect to six (6) prior quarterly distribution periods, whether or not
consecutive, provided, however, that a distribution in respect of Series B
Preferred Units shall be considered timely made if made within two (2) Business
Days after the applicable Preferred Unit Distribution Payment Date if at the
time of such late payment there shall not be any prior quarterly distribution
periods in respect of which full distributions were not timely made or (z) upon
receipt by a holder or holders of Series B Preferred Units of (1) a notice from
the General Partner that the General Partner or a Subsidiary of the General
Partner has taken the position that the Partnership is, or upon the occurrence
of a defined event in the immediate future will be, a PTP and (2) an opinion
rendered by an outside nationally recognized independent counsel familiar with
such matters addressed to a holder or holders of Series B Preferred Units, that
the Partnership is or likely is, or upon the occurrence of a defined event in
the immediate future will be or likely will be, a PTP. In addition, the Series B
Preferred Units may be exchanged for Series B Preferred Shares, in whole or in
part, at the option of any holder prior to the tenth (10th) anniversary of the
issuance date and after the third (3rd) anniversary thereof if such holder of a
Series B Preferred Units shall deliver to the General Partner either (i) a
private letter ruling addressed to such holder of Series B Preferred Units or
(ii) an opinion of independent counsel reasonably acceptable to the General
Partner based on the enactment of temporary or final

                                       9
<PAGE>

Treasury Regulations or the publication of a Revenue Ruling, in either case to
the effect that an exchange of the Series B Preferred Units at such earlier time
would not cause the Series B Preferred Units to be considered "stock and
securities" within the meaning of section 351(e) of the Code for purposes of
determining whether the holder of such Series B Preferred Units is an
"investment company" under section 721(b) of the Code if an exchange is
permitted at such earlier date. Furthermore, all the Series B Preferred Units
held by any holder thereof which is a real estate investment trust within the
meaning of Sections 856 through 859 of the Code for Series B Preferred Shares
may be exchanged in whole but not in part (but only if the exchange may be
accomplished consistently with the ownership limitations set forth under Article
3 of the Charter (taking into account exceptions thereto)) if at any time, (i)
the Partnership reasonably determines that the assets and income of the
Partnership for a taxable year after 1999 would not satisfy the income and
assets tests of Section 856 of the Code for such taxable year if the Partnership
were a real estate investment trust within the meaning of the Code or (ii) any
such holder of Series B Preferred Units shall deliver to the Partnership and the
General Partner an opinion of independent counsel reasonably acceptable to the
General Partner to the effect that, based on the assets and income of the
Partnership for a taxable year after 1999, the Partnership would not satisfy the
income and assets tests of Section 856 of the Code for such taxable year if the
Partnership were a real estate investment trust within the meaning of the Code
and that such failure would create a meaningful risk that a holder of the Series
B Preferred Units would fail to maintain qualification as a real estate
investment trust.

            (ii) Notwithstanding anything to the contrary set forth in Section
9(a)(i) hereof, if an Exchange Notice (as defined herein) has been delivered to
the General Partner, then the General Partner may, at its option, elect to
redeem or cause the Partnership to redeem all or a portion of the outstanding
Series B Preferred Units for cash in an amount equal to the original Capital
Contribution per Series B Preferred Unit and all accrued and unpaid
distributions thereon to the date of redemption. The General Partner may
exercise its option to redeem the Series B Preferred Units for cash pursuant to
this Section 9(a)(ii) hereof by giving each holder of record of Series B
Preferred Units notice of its election to redeem for cash, within five (5)
Business Days after receipt of the Exchange Notice, by (y) fax, and (z)
registered mail, postage paid, at the address of each holder as it may appear on
the records of the Partnership stating (A) the redemption date, which shall be
no later than sixty (60) days following the receipt of the Exchange Notice, (B)
the redemption price, (C) the place or places where the Series B Preferred Units
are to be surrendered for payment of the redemption price, (D) that
distributions on the Series B Preferred Units will cease to accrue on such
redemption date (E) that payment of the redemption price will be made upon
presentation and surrender of the Series B Preferred Units and (F) the aggregate
number of Series B Preferred Units to be redeemed, and if fewer than all of the
outstanding Series B Preferred Units are to be redeemed, the number of Series B
Preferred Units to be redeemed held by such holder, which number shall equal
such holder's pro-rata share (based on the percentage of the aggregate number of
outstanding Series B Preferred Units the total number of Series B Preferred
Units held by such holder represents) of the aggregate number of Series B
Preferred Units being redeemed.

            (iii) In the event an exchange of all or a portion of Series B
Preferred Units

                                       10
<PAGE>

pursuant to Section 9(a)(i) hereof would violate the provisions on ownership,
limitation of the General Partner set forth in Article 3 of the Charter with
respect to the Series B Preferred Shares, the General Partner shall give written
notice thereof to each holder of record of Series B Preferred Units, within five
(5) Business Days following receipt of the Exchange Notice, by (y) fax, and (z)
registered mail, postage prepaid, at the address of each such holder set forth
in the records of the Partnership. In such event, each holder of Series B
Preferred Units shall be entitled to exchange, pursuant to the provision of
Section 9(b) a number of Series B Preferred Units which would comply with the
provisions on the ownership limitation of the General Partner set forth in such
Article 3 of the Charter and any Series B Preferred Units not so exchanged (the
"Excess Units") shall be redeemed by the Partnership for cash in an amount equal
to the original Capital Contribution per Excess Unit, plus any accrued and
unpaid distributions thereon, whether or not declared, to the date of
redemption. The written notice of the General Partner shall state (A) the number
of Excess Units held by such holder, (B) the redemption price of the Excess
Units, (C) the date on which such Excess Units shall be redeemed, which date
shall be no later than sixty (60) days following the receipt of the Exchange
Notice, (D) the place or places where such Excess Units are to be surrendered
for payment of the Redemption Price, (E) that distributions on the Excess Units
will cease to accrue on such redemption date, and (F) that payment of the
redemption price will be made upon presentation and surrender of such Excess
Units. In the event an exchange would result in Excess Units, as a condition to
such exchange, each holder of such units agrees to provide representations and
covenants reasonably requested by the General Partner relating to (1) the widely
held nature of the interests in such holder, sufficient to assure the General
Partner that the holder's ownership of stock of the General Partner (without
regard to the limits described above) will not cause any individual to
Beneficially Own in excess of the Ownership Limit (all as defined in the General
Partner's Charter); and (2) to the extent such holder can so represent and
covenant without obtaining information from its owners, the holder's ownership
of tenants of the Partnership and its affiliates.

            (iv) The redemption of Series B Preferred Units described in Section
9(a)(ii) and (iii) shall be subject to the provisions of Section 6(b)(i) and
Section 6(c)(ii); provided, however, that the term "Redemption Price" in such
Section shall be read to mean the original Capital Contribution per Series B
Preferred Unit being redeemed plus all accrued and unpaid distributions to the
redemption date.

      (b) Procedure for Exchange. (i) Any exchange shall be exercised pursuant
to a notice of exchange (the "Exchange Notice") delivered to the General Partner
by the holder who is exercising such exchange right, by (A) fax and (B) by
certified mail postage prepaid. The exchange of Series B Preferred Units, or a
specified portion thereof, may be effected after the fifth (5th) Business Day
following receipt by the General Partner of the Exchange Notice by delivering
certificates, if any, representing such Series B Preferred Units to be exchanged
together with, if applicable, written notice of exchange and a proper assignment
of such Series B Preferred Units to the office of the General Partner maintained
for such purpose. Currently, such office is Two Center Plaza, Suite 200, Boston,
Massachusetts 02108. Each exchange will be deemed to have been effected
immediately prior to the close of business on the date on which

                                       11
<PAGE>

such Series B Preferred Units to be exchanged (together with all required
documentation) shall have been surrendered and notice shall have been received
by the General Partner as aforesaid and the Exchange Price shall have been paid.
Any Series B Preferred Shares issued pursuant to this Section 9 shall be
delivered as shares which are duly authorized, validly issued, fully paid and
nonassessable, free of pledge, lien, encumbrance or restriction other than those
provided in the Charter, the Bylaws of the General Partner, the Securities Act
and relevant state securities or blue sky laws.

            (ii) In the event of an exchange of Series B Preferred Units for
Series B Preferred Shares, an amount equal to the accrued and unpaid
distributions, whether or not declared, to the date of exchange on any Series B
Preferred Units tendered for exchange shall (A) accrue on the Series B Preferred
Shares into which such Series B Preferred Units are exchanged, and (B) continue
to accrue on such Series B Preferred Units, which shall remain outstanding
following such exchange, with the General Partner as the holder of such Series B
Preferred Units. Notwithstanding anything to the contrary set forth herein, in
no event shall a holder of a Series B Preferred Unit that was validly exchanged
into Series B Preferred Shares pursuant to this section (other than the General
Partner now holding such Series B Preferred Unit), receive a cash distribution
out of Available Cash of the Partnership, if such holder, after exchange, is
entitled to receive a distribution out of Available Cash with respect to the
Series B Preferred Shares for which such Series B Preferred Unit was exchanged
or redeemed.

            (iii) Fractional shares of Series B Preferred Shares are not to be
issued upon exchange but, in lieu thereof, the General Partner will pay a cash
adjustment based upon the fair market value of the Series B Preferred Shares on
the day prior to the exchange date as determined in good faith by the Board of
Directors of the General Partner.

      (c) Adjustment of Exchange Price. (i) The Exchange Price is subject to
adjustment upon certain events, including, (A) subdivisions, combinations and
reclassification of the Series B Preferred Shares, and (B) distributions to all
holders of Series B Preferred Shares of evidence of indebtedness of the General
Partner or assets (including securities, but excluding dividends and
distributions paid in cash out of equity applicable to Series B Preferred
Shares).

            (ii) In case the General Partner shall be a party to any transaction
(including, without limitation, a merger, consolidation, statutory share
exchange, tender offer for all or substantially all of the General Partner's
capital stock or sale of all or substantially all of the General Partner's
assets), in each case as a result of which the Series B Preferred Shares will be
converted into the right to receive shares of capital stock, other securities or
other property (including cash or any combination thereof), each Series B
Preferred Unit will thereafter be exchangeable into the kind and amount of
shares of capital stock and other securities and property receivable (including
cash or any combination thereof) upon the consummation of such transaction by a
holder of that number of Series B Preferred Shares or fraction thereof into
which one Series B Preferred Unit was exchangeable immediately prior to such
transaction. The General Partner may not become a party to any such transaction
unless the terms thereof are consistent with the foregoing.

                                       12
<PAGE>

            Section 10. No Conversion Rights. (a) The holders of the Series B
Preferred Units shall not have any rights to convert such shares into shares of
any other class or series of shares or into any other securities of, or interest
in, the Partnership.

            (b) The Series B Preferred Units shall not be subject to the
provisions of Section 4.2(e) of the Partnership Agreement.

            Section 11. No Sinking Fund. No sinking fund shall be established
for the retirement or redemption of Series B Preferred Units.

            Section 12. Admission of Limited Partners, Exhibits to Partnership
Agreement. In accordance with Section 12.2(b), Belair and Belcrest are hereby
admitted as Additional Limited Partners. In order to duly reflect the issuance
of Series B Preferred Units provided for herein, the Partnership Agreement is
hereby amended by deleting Exhibit A attached thereto and substituting Exhibit A
attached hereto therefor.

            Section 13. Reaffirmation. Except as modified herein, all terms and
conditions of the Partnership Agreement shall remain in full force and effect,
which terms and conditions the General Partner hereby ratifies and affirms.

                            *          *          *

                                       13
<PAGE>

      IN WITNESS WHEREOF, this Amendment has been executed as of the date first
above written.


                                    CABOT INDUSTRIAL TRUST

                                    By: /s/ Franz Colloredo-Mansfeld
                                        -------------------------------
                                    Name: Franz Colloredo-Mansfeld
                                    Title: Chief Financial Officer


                                    BELCREST REALTY CORPORATION

                                    By: /s/Thomas E. Faust, Jr.
                                        -------------------------------
                                    Name: Thomas E. Faust, Jr.
                                    Title: Executive Vice President


                                    BELAIR REAL ESTATE CORPORATION

                                    By: /s/Thomas E. Faust, Jr.
                                        -------------------------------
                                    Name: Thomas E. Faust, Jr.
                                    Title: Executive Vice President

                                       14