The Cyberhymnal link doesn't work because you have unconsciously corrected their rather odd spelling. http://www.cyberhymnal.org/htm/b/t/btmvison.htm should do the trick.

For McGrath's benefit, 'Slane' is dealt with at some length elsewhere here, though with the usual mix of good information and complete nonsense. See in particular the old, embarrassingly-titled thread Be Thou My Vision -do ya know this Irish Tune, recently again resurrected.

The tune used for this version, however, is not related to 'Slane' so far as I can tell; neither, for that matter, is the version in Sam Henry's Songs of the People. It may be that people just assume that 'Slane' is the usual tune for Banks of the Bann, having heard it so often sung to that melody. It may only appear common because so often recorded by revival performers, though, and these do tend to learn songs from each other rather than from traditional sources, which can create quite wrong impressions as to what was normal or common in the past.

The song appeared on broadsides as The Brown Girl, and that seems to be its usual name; sometimes the Ban[n] is mentioned, sometimes the Boyne, but the broadside action appears to take place in another part of the world; perhaps the Indies which are usually mentioned. In forms found in (probably later) oral currency, the whole action moves to the banks of the Bann. I wonder if this may have happened via cross-influence from the various other "Bann" songs like Willie Archer? Martin or Tim would know much more about that than I do, and I'd hope they might comment further; but of course we especially miss John Moulden at times like this.