Not satisfied with his discoveries in America, he crossed the steppes of Asia, the wastes of Siberia, the great Ural range, adding to the knowledge of mankind at every step. His energy acknowledged no obstacle, his life knew no leisure; every day was filled with labor and with thought.
He was one of the apostles of science, and he served his divine master with a self-sacrificing zeal that knew no abatement; with an ardor that constantly increased, and with a devotion unwavering and constant as the polar star.
In order that the people at large might have the benefit of his numerous discoveries, and his vast knowledge, he delivered at Berlin a course of lectures, consisting of sixty-one free addresses, upon the following subjects:
Five, upon the nature and limits of physical geography.
Three, were devoted to a history of science.
Two, to inducements to a study of natural science.
Sixteen, on the heavens.
Five, on the form, density, latent heat, and magnetic power of the earth, and to the polar light.
Four, were on the nature of the crust of the earth, on hot springs earthquakes, and volcanoes.
Two, on mountains and the type of their formation.