Complex sentence: Jenson was appointed as a full-time Assistant Church Historian in 1897 and served as acting Church Historian, with John Jaques, from 1899 until the appointment of Anthon H. Lund as Church Historian in 1900.
Split into simpler sentences: Jenson was appointed as a full-time Assistant Church Historian in 1897. Along with John Jaques, Jenson was the Acting Church Historian from 1899 until the appointment of Anthon H. Lund as Church Historian in 1900.