It looks like "Hark" may have a history of change. According to the Cyber Hymnal, Wesley's words were changed in a hymn book by Chope, 1857 (the old text is given, same meter). I don't have Mendelssohn's cantata, Festgesang, so I don't know how much the tune excerpted from the cantata was "arranged" by Wm. Cummings in 1885 (this is the common one)- it could be quite a change.
Was Cookson a person or a place? You might have to trace that down to see if there was an older tune.