A versatile poet, Ellis wrote elegies on Evan Evans (Ieuan Brydydd Hir) and on his old schoolmaster Edward Richard (qq.v.). Probably his greatest service to his contemporaries was to translate the following English works into Welsh: The knowledge and practice of Christianity by Thomas Wilson (London, 1774); A short manual of prayers for common occasions, by James Merrick (London, 1774 and 1805); and The History of the Holy Jesus, by William Smith (Trefriw, 1776). He translated into Welsh a poem by Evan Evans (Ieuan Brydydd Hir), entitled The Penitent Shepherd: a sacred poem, which was published in Blodau Dyfed, an anthology compiled by J. Howell (Carmarthen, 1824) [p. 55]. He also copied a large number of Welsh manuscripts which today are included among such well-known collections as Peniarth, Cwrtmawr, and N.L.W., in the National Library of Wales; Gwyneddon in the library of the U.C.N.W., Bangor, and Cardiff City Free Library. He also made a transcript of Mona Antiqua Restaurata, by Henry Rowlands (1655-1723) (q.v.), which he presented to the library of his old school at Ystrad Meurig.