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                                                                     EXHIBIT 8.1


             [LETTERHEAD OF BALLARD SPAHR ANDREWS & INGERSOLL, LLP]






                                                March 17, 1999



Hercules Incorporated
Hercules Trust I
Hercules Plaza
1313 North Market Street
Wilmington, Delaware 19894-0001

                  RE:      9.42% TRUST ORIGINATED PREFERRED SECURITIES
                           OF HERCULES TRUST I

Ladies and Gentlemen:

                  We have acted as special tax counsel for Hercules
Incorporated, a Delaware corporation (the "Company"), and Hercules Trust I, a
statutory business trust organized under the Business Trust Act of the State of
Delaware (12 Del. Code Ann., tit. 12, Sections 3801, et seq.) (the "Trust"), in
connection with the sale pursuant to an Underwriting Agreement dated March 17,
1999 among the Company, the Trust and the underwriters (the "Underwriters")
named therein (the "Underwriting Agreement") of 14,500,000 9.42% Trust
Originated Preferred Securities (liquidation amount $25 per preferred
security) of the Trust (the "Preferred Securities"), representing undivided
beneficial interests in the assets of the Trust.

                  The Preferred Securities are guaranteed by the Company with
respect to distributions and payments upon liquidation, redemption, and
otherwise pursuant to the Preferred Securities Guarantee Agreement, dated as of
March 17, 1999 (the "Guarantee Agreement"), between the Company and The Chase
Manhattan Bank, as trustee, for the benefit of the holders of the Preferred
Securities.

                  In connection with the issuance of the Preferred Securities,
the Trust is also issuing 448,454 9.42 % Common Securities (liquidation amount
$25 per common security) (the "Common Securities"), representing undivided
beneficial interests in the assets of the Trust.

                  The entire proceeds from the sale of the Preferred Securities
and the Common Securities are to be used by the Trust to purchase an aggregate
principal amount of $373,711,350
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Hercules Trust I
March 17, 1999
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9.42% Junior Subordinated Deferrable Interest Debentures due 2029 (the
"Subordinated Debentures"), to be issued by the Company. The Preferred
Securities and the Common Securities are to be issued pursuant to the Amended
and Restated Trust Agreement, dated as of March 17, 1999 (the "Trust
Agreement"), among the Company, as sponsor, Chase Manhattan Bank Delaware, as
Delaware trustee (the "Delaware Trustee"), The Chase Manhattan Bank, as property
trustee (the "Property Trustee"), and Israel J. Floyd, Jan M. King, and Stuart
C. Shears, as administrative trustees (the "Administrative Trustees"). The
Subordinated Debentures are to be issued pursuant to the junior subordinated
debentures indenture, dated as of March 17, 1999 (the "Indenture"), between the
Company and The Chase Manhattan Bank, as indenture trustee (the "Indenture
Trustee").

                  Capitalized terms used but not otherwise defined herein shall
have the respective meanings set forth in the Underwriting Agreement.

                  In connection with this opinion, we have examined originals or
copies, certified or otherwise identified to our satisfaction, of (i) the
Prospectus Supplement dated March 12, 1999 (including a Prospectus dated October
30 1998) ; (ii) the Certificate of Trust filed with the Secretary of State of
the State of Delaware as of September 14, 1998, by an Administrative Trustee and
the Delaware Trustee; (iii) an executed copy of the Trust Agreement including
the designation of the terms of the Preferred Securities; (iv) the form of the
Preferred Securities and a specimen certificate thereof; (v) an executed copy of
the Guarantee Agreement; (vi) an executed copy of the Indenture; (vii) the form
of Subordinated Debentures and a specimen certificate thereof; (viii) the form
of Common Securities and a specimen certificate thereof; (ix) an executed copy
of the Underwriting Agreement; and (x) representations from an officer of the
Company dated March 17, 1999. We have also examined originals or copies,
certified or otherwise identified to our satisfaction, of such records of the
Company and the Trust and such agreements, certificates of public officials,
certificates of officers, trustees or other representatives of the Company, the
Trust and others, as applicable, and such other documents, certificates and
records as we have deemed necessary or appropriate as a basis for the opinions
set forth herein.

                  In our examination, we have assumed the legal capacity of all
natural persons, the genuineness of all signatures, the authenticity of all
documents submitted to us as originals, the conformity to original documents of
all documents submitted to us as certified, conformed or photostatic copies, and
the authenticity of the originals of such latter documents. In making our
examination of documents executed, or to be executed by parties other than the
Company or the Trust, we have assumed that such parties had, or will have the
power, corporate or other, to enter into and perform all obligations thereunder
and have also assumed the due authorization by all requisite action, corporate
or other, and execution and delivery by such parties of such
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Hercules Trust I
March 17, 1999
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documents and that such documents constitute, or will constitute, valid and
binding obligations of such parties. As to any facts material to the opinions
expressed herein which were not independently established or verified, we have
relied upon oral or written statements and representations of officers, trustees
and other representatives of the Company, the Trust and others.

                  In rendering our opinion, we have participated in the
preparation of the Prospectus Supplement. Our opinion is conditioned on, among
other things, the initial and continuing accuracy of the facts, information,
covenants, and representations set forth in the documents referred to above and
the statements and representations made by the Company and the Trust.

                  In rendering our opinion, we have considered the provisions of
the Internal Revenue Code of 1986, as amended, Treasury regulations (proposed,
temporary and final) promulgated thereunder, judicial decisions and Internal
Revenue Service rulings all as of the date hereof, and all of which are subject
to change, which changes may be retroactively applied. A change in the
authorities upon which opinion is based could affect our conclusions. There can
be no assurance, moreover, that any opinion expressed herein will be accepted by
the Internal Revenue Service or, if challenged, by a court.

                  Based solely upon the foregoing, we are of the opinion that
under current United States federal income tax law, although the discussion set
forth in the Prospectus Supplement under the heading "CERTAIN UNITED STATES
FEDERAL INCOME TAX CONSEQUENCES" does not purport to discuss all possible United
States federal income tax consequences of the purchase, ownership, and
disposition of the Preferred Securities, in our opinion such discussion
constitutes, in all material respects, a fair and accurate summary of the United
States federal income tax consequences, to the holders who purchase the
Preferred Securities at their original issuance, of the purchase, ownership, and
disposition of the Preferred Securities.

                  Except as set forth above, we express no opinion to any party
as to the tax consequences, whether United States federal, state, local or
foreign, of the issuance of the Subordinated Debentures, the Preferred
Securities, the Common Securities, or any transactions related to or
contemplated by such issuance.

                  We are furnishing this opinion to you solely for your benefit
in connection with the sale of the Preferred Securities pursuant to the
Underwriting Agreement and the opinion is not to be used, circulated, quoted, or
otherwise referred to for any other purpose without our prior written
permission. This opinion is expressed as of the date hereof, and we disclaim any
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Hercules Trust I
March 17, 1999
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undertaking to advise you of changes of the facts stated or assumed herein or
any subsequent changes in applicable law.

                  We consent to the filing of this opinion as Exhibit 8.1 to the
Form 8-K of the Company dated March 17, 1999 as filed with the Securities and
Exchange Commission on March 17, 1999, and to the reference to Ballard Spahr
Andrews & Ingersoll, LLP therein under the caption "Legal Matters". In giving
this consent, we do not thereby admit that we are within the category of persons
whose consent is required under Section 7 of the Securities Act of 1933, as
amended or the rules or regulations of the Securities and Exchange Commission
promulgated thereunder.


                              /s/ Ballard Spahr Andrews & Ingersoll, LLP