In 1877 Henry Drummond became lecturer on natural science in the Free Church College, which enabled him to combine all the pursuits for which he felt a vocation. His studies resulted in his writing Natural Law in the Spiritual World, the argument of which is that the scientific principle of continuity extends from the physical world to the spiritual. Before the book was published in 1883, an invitation from the African Lakes Company drew Drummond away to Central Africa.
Upon his return in the following year he found himself famous. Large bodies of serious readers, among the religious and the scientific classes alike, discovered in Natural Law the common standing-ground which they needed; and the universality of the demand proved, if nothing more, the seasonableness of its publication. Drummond continued to be actively interested in missionary and other movements among the Free Church students.
