Chapman and Cutler LLP
                             111 West Monroe Street
                            Chicago, Illinois 60603


                                 July 10, 2017


Mr. Edward Bartz
Division of Investment Management
Securities and Exchange Commission
100 F Street, N.E.
Washington, DC  20549


                 Re: Guggenheim Defined Portfolios, Series 1625
               Convertible & Income Portfolio of Funds, Series 26
                       File Nos. 333-218651 and 811-03763
-------------------------------------------------------------------------------
Dear Mr. Bartz:

      This letter is in response to your comment given during a telephone
conversation with our office regarding the registration statement on Form S-6
for Guggenheim Defined Portfolios, Series 1625, filed on June 9, 2017, with the
Securities and Exchange Commission (the "Commission"). The registration
statement proposes to offer the Convertible & Income Portfolio of Funds, Series
26 (the "Trust").

PROSPECTUS

Investment Summary -- Principal Risks

       1. The duration example in the sixth bullet uses a duration of three
years. Please confirm that the average weighted duration of the fixed-income
securities held indirectly by the Trust is approximately three years or less. If
not, please revise this example to reflect the average weighted duration of the
fixed-income securities.

      Response: The average weighted duration of the fixed-income securities
held by the closed-end funds included in the Trust portfolio is approximately
five years and, therefore, the example has been revised.

      We appreciate your prompt attention to this registration statement. If you
have any questions or comments or would like to discuss our responses to your
questions, please feel free to contact the undersigned at (312) 845-3484.

                                                               Very truly yours,

                                                          CHAPMAN AND CUTLER LLP


                                                       By /s/ Morrison C. Warren
                                                       -------------------------
                                                              Morrison C. Warren