[3] In 1877 he was lecturer on natural science in the Free Church College on Lynedoch Street in Glasgow, which enabled him to combine all the pursuits for which he felt a vocation.

In 1884 he was a guest at Haddo House for a dinner hosted by John Hamilton-Gordon, 1st Marquess of Aberdeen and Temair in honour of William Ewart Gladstone on his tour of Scotland.

[6] Large bodies of serious readers, among the religious and the scientific classes alike, discovered in Natural Law the common ground they needed; and the universality of the demand proved, if nothing more, the seasonableness of its publication.

He had meant to keep them aside for mature revision, but an attempted piracy compelled him to hasten their publication, and they appeared in 1894 under the title of The Ascent of Man.

Their object was to ratify altruism or, the disinterested care and compassion of animals for each other, important in effecting the survival of the fittest, a thesis previously maintained by philosopher professor John Fiske.

In 1905 a medallion plaque to his memory was erected in the Free Church College in Edinburgh, sculpted by James Pittendrigh Macgillivray.