"Braes o' Yarrow" had been given already in Ramsey's "Tea Table
Miscellany," The opening lines--

"Busk ye, busk ye, my bonny, bonny bride,
Busk ye, busk ye, my winsome marrow"--

are quoted in Wordsworth's "Yarrow Unvisited," as well as a line of the
following stanza:

"Sweet smells the birk, green grows, green grows the grass,
Yellow on Yarrow's bank the gowan:
Fair hangs the apple frae the rock,
Sweet the wave of Yarrow flowin'."

The first edition of the "Reliques" included one acknowledged child of
Percy's muse, "The Friar of Orders Grey," a short, narrative ballad made
up of song snatches from Shakspere's plays. Later editions afforded his
longer poem, "The Hermit of Warkworth," first published independently in
1771.

With all its imperfections--perhaps partly in consequence of its
imperfections--the "Reliques" was an epoch-making book. The nature of
its service to English letters is thus stated by Macaulay, in the
introduction to his "Lays of Ancient Rome": "We cannot wonder that the
ballads of Rome should have altogether disappeared, when we remember how
very narrowly, in spite of the invention of printing, those of our own
country and those of Spain escaped the same fate. There is, indeed,
little doubt that oblivion covers many English songs equal to any that
were published by Bishop Percy; and many Spanish songs as good as the
best of those which have been so happily translated by Mr. Lockhart.