Very nice, Simon!
Simon wrote: "it's a nice melody."
Agree.
It's apparently an old trad Irish folk melody, which someone years ago decided to name "Slane".
It's been used for lots of different hymns, including "Be Thou My Vision" (the one I've heard the most), and "Lord Of All Hopefulness".
Near as I can tell, the earliest known written instance of the *melody* is in the 1909 book "Old Irish Folk Music and Songs", where the melody is used for the song "With My Love on the Road" (PDF page 192, or if you're going by the book's own semi-useless page numbers it's 151).
Incidental notes about the aforementioned tunebook:
1. The book's *index* starts on the PDF's page 30. When you're looking up tunes listed in that index, just be aware that the book's original page-numbering system of course doesn't match the modern PDF page numbers which count everything including the front cover.
2. It's a large download (454-page book, which shows as 24 MB here) but it seems to work fine in the MobileSheetsPro app (NFI) which is what I'm using to look at it right now on my phone. Of course it also is readable in other standard PDF reader apps on computers or elsewhere.
3. The scan quality is quite bad on some pages, too light to read.
4. In the index and on the page numbers, some of the number 4's look like the number "1" instead, which adds further challenges to trying to look up tunes in that book. The number-readability issue is partly due to the lousy scan quality, and partly due to the fact that the original 1909 book used a completely stupid typeface whose numbers don't align vertically in a logical way (yes I'm aware that such typefaces were/are quite popular, but IMO it's still a poor choice to use in number-centric things like an index where readability should take precedence over style). So anyway, when you see what looks like a 1, it might be a 4 instead. Just keep that in mind if trying to use the index to look up other tunes.
A technical aside, and completely off-topic, I learned a new technical thing today as a result of Simon's post and my subsequent reading - rummaging through that 454-page Irish tunes PDF prompted me to finally learn how to add *bookmarks* in the MobileSheetsPro sheetmusic-reader app. I've been using the app for a number of years already but had never had any reason to use bookmarks, as nearly all the other sheetmusic I have in there is only one or two pages, three at most, no bookmarks required. But 454 pages gave me incentive to finally try adding bookmarks. It turns out to be an intuitive process, I didn't even have to look up instructions online, and seems to work well although if you inadvertently delete a bookmark there doesn't seem to be an "undo", so I have to pay attention to exactly what it is I'm tapping on my screen. So anyway now I know how to do that, which could come in handy for any future large PDF's (that app will read *any* PDF, doesn't have to be sheetmusic, I've occasionally used it to read various newsletters that people insist on sending me in PDF format instead of plaintext which would be more sensible, but I digress).
Anyway... music can be useful in unexpected ways! If I hadn't seen Simon's post and wonderfully-played tune, I wouldn't have learned how to do the bookmarks in the sheetmusic-reader app.
(Typing this on my phone, hope the formatting and links show up correctly)