Great job, Rossey. It would still be nice to see the 1840 original, but it was clearly the "same" song.

Christie's tune isn't quite today's standard, but it would be foolish to quibble about the differences.

In the USA, the song isn't even mentioned until ca1895.

The English collector Frank Kidson wrote in the Leeds Mercury (Feb. 25, 1888) as follows:

"I've never seen it in print, but the following are fragments picked up among the cotters of Eskdale. They are wedded to a very beautiful old air, to which certain other old songs are sung [Like what, dammit?! -ed.], and it may find a place in these columns some day:

    On yon bonny banks and yon bonny braes,
      Where the moon shines so bright and clearly,
    Where I and my ain true love went out to gaze
      On the bonny, bonny banks of Loch Lomond.

    It's na for the leaving of this bonny place,
      Nor my master and mistress that grieves me,
    But it's a' for the leaving o' my kind comrades a',
      And the bonny lass that lo'es me so dearly.

    You take the high road and I'll take the low road,
      And I'll be in Scotland before you, &c."

British papers begin mentioning concert performances of the song later in 1888, and they soon become notably frequent.

The first U.S. notice I've found is from 1890. Performances here take off in 1894.

So it would seem that a somewhat obscure 1840s parlor song entered oral tradition in Scotland and was popularized by stage performers (and, I assume, new sheet music) everywhere some fifty years later.