He married Ann Chalk in 1845. In 1852, when his health began to fail, he sold his practice and spent a year in France. By the next year he had graduated from King's College, Aberdeen, with plans to become a physician.[2]
Missionary work
Soon after graduating, he became interested in missionary work. In 1854, he was made a deacon by John Colenso, bishop of Natal having become a member of the Church of England two years earlier. Soon afterwards, he went as a missionary to Africa. Initially, he was stationed at Ekukanyeni (near Pietermaritzburg), but, after being ordained as a priest in 1855, he was made rector of St. Andrew's church, Pietermaritzburg . [2]
In 1873, he was recalled to England so he could be consecrated[5] as the first missionary Bishop of St John's, Kaffraria. He left Great Britain the following year. In 1876, he moved the seat of his diocese to Umtata, where he founded St John's Theological College.[2]
His health, however, began to fail, and he resigned his post in 1886. The next year he returned to England, making his home at Ottery Saint Mary, where he lived until his death in 1890.
Immediate Revelation. London: Harvey and Darton. 1842. Being a Brief View of the Dealings of God with Man in All Ages, Showing the Universal and Immediate Agency of the Holy Spirit Under Different Dispensations...
The Last Word of "Modern Thought.". 1866. Two Sermons, Preached at Saint Peter's Cathedral, and at Saint Andrew's Church, Pietermaritzburg, Natal ... December, 1865
^"Church News - A New African Bishopric". Hampshire Advertiser. 13 August 1873. Retrieved 8 September 2014 – via British Newspaper Archive. A new bishopric has been formed for British Kaffraria, and the Rev. H. Callaway, a Missionary of the Church of England at Spring Vale, Natal, has been named as the first occupant of the see. He will probably be consecrated by the Primus of the Episcopal Church in Scotland. The diocese will be between the Colonies of the Cape and Natal, and be in extent equal to the whole ef England. Dr. Callaway was some years ago an eminent surgeon in Southwark.
Colenso, John William (1854). The Good Tidings of Great Joy. London. A Sermon Preached in the Cathedral Church of Norwich, on Sunday, August 13, 1854, on the Occasion of Ordaining Henry Callaway, M.D. (Late A Member of the Society of Friends,) as a Missionary among the Heathen in the Diocese of Natal, By the Right Reverend John William Colenso, D.D., Lord Bishop of Natal (1854)
The Collects, Epistles, and Gospels, from the Book of Common Prayer of the Church of England. Translated into Zulu. Springvale, Natal: J. A. Blair. 1866.
Anon (1873). "Diocese of Maritzburg". In J.J. Halcombe (ed.). Mission Life: Or Home and Foreign Church Work.