He had worked earnestly upon the "Principles," which showed wonderful research, study, and thought. He said, "The facts which are given in a few sentences require weeks of reading to obtain.... By the aid of a good amanuensis, my eyes hold out well." The sale of the book was large and satisfactory. It was, of course, opposed, from its advanced views as to the age of the world, but Lyell wisely made no reply. He said, "I have sworn to myself that I will not go to the expense of giving time to combat in controversy. It is an interminable work." A great lesson, learned early. In 1831 he visited Germany. Now he wrote home not only to his family, but to another, who was hereafter to brighten and beautify his life--Mary Horner, the daughter of a prominent scientist. To great personal beauty she added unusual mental ability. Wise man indeed was Charles Lyell to have known, what some fail to know beforehand, that intellect demands intellect for the best companionship. He wrote to her: "I am sure you will work at it" (the German language) "with more zeal if you believe you can help me by it, as I labor with greater spirit, now that I regard myself as employed for you as well as for myself. Not that I am at all sanguine about the pecuniary profits that I shall ever reap, but I feel that if I could have fair play for the next ten years, I could gain a reputation that would make a moderate income for the latter part of my life, yield me a command of society, and a respect that would entitle me to rest a little on my oars, and enable me to help somewhat those I love.... As to geology having _half_ of my heart, I hope I shall be able to give my _whole_ soul to it, with that enthusiasm by which alone any advance can be made in any science, or, indeed, in any profession." In 1832 Lyell was made professor of geology in King's College, London, which position he resigned later, because he wished "the power of commanding _time_ to increase his knowledge and fame." This year also, July 12, when he was thirty-five, he was married to Mary Horner, and made a tour up the valley of the Rhine. The earnest life was now more earnest and busy than ever. He said, "I am never so happy as when, at the end of a week, I feel I have employed every day in a manner that will tell to the rest of my life." Would that all of us could live after so noble a plan!