a' Ghrian was collected in the Isle of Barra, Scotland in the 19th century, but it is likely the song is of considerably older origin. https://www.electricscotland.com/books/pdf/carminagadelicah01carm.pdf

https://digital.nls.uk/early-gaelic-book-collections/archive/78430800 pages 340-341

The translation , I suppose by either Andrew or Alexander Carmichael, as published in Carmina Gadelica is

THE SUN From John MacNeill, cottar, Buaile nam Bodach, Barra

Hail to thee, thou sun of the seasons,
As thou traversest the skies aloft;
Thy steps are strong on the wing of the heavens,
Thou art the glorious mother of the stars.
Thou liest down in the destructive ocean
Without impairment and without fear;
Thou risest up on the peaceful wave-crest
Like a queenly maiden in bloom.

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Shaun Daveys "The Pilgrim" suite was commissioned on 1983 for the Celtic festival at L'Orient, Britamny. For a subsequent performance in Glasgow "He introduced the concept of a journey by St. Colum Cille through the Celtic countries" (Wikipedia). So the closing song, A' Ghrian, is also connected with this year's Colm Cille 1500 commemoration of the saint's birth.