The library which told me it had found the poem sent me a photocopy of the song. The words were identical to those I posted above, from "American Sea Songs and Chanteys", save that it "rolled home to our dear homeland". I finally learned today, their source was "The Folksinger's Workbook" compiled and edited by Irwin and Fred Silber. I felt rather foolish. I am sure that Hugill is a thorough researcher and he was not able to answer the question. I have requested the books above by Mackay, but they will come by inter-library loan, which will probably take weeks. I am still interested in the origin of the tune. Mackay's history doesn't indicate whether the words, if they are his, were set to a new melody or an old one.