prime object in all his lectures was to elevate and enlarge the mental vision. He sought to present the truth as his studies had shown it to him in a manner to awaken the interest of his audience and make them informed upon the subject. He sunk himself in his theme, kept the question of money profit farthest from his thoughts, and was never known to relinquish a course because it did not pay. It would be impracticable to enumerate here the several subjects of these lectures or speak of the places in the East and West where they were delivered. The whole country knew him through them. They were given first chiefly in the Eastern States, then Chicago and the Northwest became the principal field, and in the later years of the author's life the Pacific and Southern States. They were delivered in public halls, before lyceums, in colleges, in the field, in churches, before Young Men's Christian Associations, and were nearly everywhere listened to with absorbed attention, and well received even by those whose views were very different from his, and were commended by the public, by scholars, and by men of science. Sometimes they met with opposition and hostile criticism, as at Brooklyn, N. Y., and at Keene, N. H., where the Young Men's Christian Association took pains to resolve that it would not be held responsible for his views. Darwinism had not yet ceased to be a novelty and a shock to theologians, and there were not wanting men who were ready to use any pretext for attacking him on this ground. He was never at a loss for a sufficient answer to these attacks, and simply relied on facts for the vindication of his position. The accounts given by the hearers of his lectures all speak of wonderful power in them—descriptive and persuasive.
He soon came into demand as a contributor to periodicals, and through the columns of such journals as The Congregationalist, Christian Union, Theodore Tilton's Golden Age, Lippincott's Magazine, etc., his articles reached tens of thousands of readers. While addressing common intelligence he would never trifle with his subject or "make a toy of science," and declined offers for papers on the "science-made-easy" plan. His purpose and the thought that animated him were well expressed in the preface to his Life History of our Planet—published in Chicago in 1876, with illustrations by Mrs. Mary Gunning, in the observation that teaching the facts of a science is not teaching the science; that "facts do not enlarge the mind unless they are fertilized by principles," and that he sought to conduct his reader "through method to results."
Visiting Europe in 1866, after the death of the first Mrs. Gunning, he made a pedestrian tour through Yorkshire; was a guest on geological excursions of Sir Thomas Crosley in Halifax; was entertained by Prof. Robert Harley; lectured at Huddersfield
