- In Wales, Where it Comes From (1938)
- Tales of the Welsh Saints: Gwyr Sanctaidd Cymru (1941)
- The Sea Flyers: A Legend of the Isle of Bardsey (1941)
- Land of the Red Dragon (1943)
- The Song of the Three Holy Children: Based on the Apocryphal Story (1943)
- A Book of Welsh Saints: Lives of the Principal Saints of Wales as Set Down by the Chroniclers (1947)
- A Bundle of Welsh Tales: A Collection of Welsh Tales Selected from the Mabinogion and Adapted for Young Readers (1950)
- St. David: A Study of His Life and Times (1953)
- Celtic Heritage: Ancient Tradition in Ireland and Wales (1961)
- The Life and Times of Giraldus Cambrensis (1985)