- Trevecka letters 1-199.
- Is-gyfres
- 1725-1739.
Dangos 1217 canlyniad
Disgrifiad archifolAdditional group of (unbound) Trevecka letters,
- Trevecca College I/2787a-2944.
- Is-gyfres
- 1730-1790.
Letters written to Associations and Societies,
- Trevecca College I/3086-3112.
- Is-gyfres
- 1738-1748.
Accounts of societies sent to Associations,
- Trevecca College I/3000-3085.
- Is-gyfres
- 1741-1750.
- Trevecca College I/2945-2999.
- Is-gyfres
- 1743-1744.
- Bala College I/656-759.
- Is-gyfres
- 1743-1918.
Letters to and from Owen Thomas,
- Bala College I/640-655.
- Is-gyfres
- 1844-1879.
Letters from James Hughes, 'Yr Esboniwr', to John Roberts, Liverpool,
- Bala College I/629-639.
- Is-gyfres
- 1831-1843.
- Bala College I/606-628.
- Is-gyfres
- 1738-1748.
[The numbers in brackets following the subject in the case of some of the letters are the numbers allotted to them in M. H. Jones, 'The Trevecka letters' (Caernarfon, 1932)]. They are described in more detail in Boyd Stanley Schlenther and Eryn Mant White, Calendar of Trevecka Letters.
- Bala College I/91-107.
- Is-gyfres
- 1807-1826.
- Bala College I/48-90.
- Is-gyfres
- 1795-1836.
- Bala College I/589-605.
- Is-gyfres
- 1898-1926.
Sermons, addresses and diaries,
- Bala College I/340-588.
- Is-gyfres
- 1847-1922.
- Bala College I/325-331.
- Is-gyfres
- 1856-1915.
Letters to Thomas Charles Edwards,
- Bala College I/311-324.
- Is-gyfres
- 1856-1915.
- Bala College I/306-310.
- Is-gyfres
- Bala College I/257-295.
- Is-gyfres
- 1835-1868.
- Bala College I/236-256.
- Is-gyfres
- 1836-1869.
- Bala College I/233-235.
- Is-gyfres
- 1816-1817.
- Bala College I/230-232.
- Is-gyfres
- 1814-1818.
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