Missionary in Canada, he was born in County Down, Ireland and served in Newfoundland until his death in 1837. His letters to the Missionary Committee in London, though difficult to decipher (the secretaries had to request him to write more clearly!), provide insights into everyday life in Newfoundland, including the harsh conditions and widespread poverty. They speak of food scarcities, storms, heavy snow and journeys begun and abandoned. Ellis was injured in 1814 when his boat overturned. A year later some of those travelling with him by sea were drowned. In 1819 he described an unusual service at Port de Grave, when a family of six Labrador Indians were baptized. Both congregation and family were moved to tears as, by looks and gestures, they expressed their oneness in Christ.
Early letters spoke of opposition from Anglicans, though by 1824 relations had improved. In later years he was increasingly concerned for his family in the event of his early retirement (on account of illness) or death. Could he be moved elsewhere, he wondered, perhaps to mainland Canada where a pleasanter climate might extend his usefulness? One letter reported that he was in semi-retirement and that 'the children must remain destitute of clothing and education, and ... we must beg our bread from door to door.' He was finally appointed to Bermuda for the sake of his health, but the decision came too late. He died at Harbour Grace, Newfoundland, leaving a widow and six children, the youngest of whom was less than a year old and the eldest a boy of fifteen.