Note-Books and draft chapters in a considered study of the Mid-Conway valley - its geology, geography, history, folk-lore, & c by a monoglot Englishman named Herbert Marshall who came to work at the Aluminium Works (Laboratory Dept.) at Dolgarrog

Herbert Marshall later emigrated to Canada. He had learnt Welsh, and could speak it exceptionally well. More than that his methods of attack upon local history were on the right lines - ancient records, traditions of the contryside, visits to MS. repositories (e.g., he was at the N.L.W. in June, 1926). If he had been born in the Valley, had taken to Welsh a few years earlier, and had a more thorough training in the deciphering and interpretation of old MSS., Mr. Marshall would be ideally equipped for the task of writing local history. His intelligent curiosity and powers of collation are very evident in the notes he has made. He was highly self-critical; several of his chapters have been written twice over. Regarding these chapters, the leaves arrived here in such a hopeless confusion that it has been found impossible to find the proper sequence in all cases.

Another catalogue description can be found here https://archiveshub.jisc.ac.uk/data/gb222-bmsshmm