"Unless I can feel that I am working to some decided end, such as that of fame, money, or partly both, I cannot be quite happy, or cannot feel a stimulus to that strenuous application without which I should not remain content." He had learned what "strenuous application" means, and knew that there is no success without it. When congratulated by his friends "in not looking older for his hard work," he said, "The way to do much and not grow old is, to be moderate in not going out, to work a few hours, or half-hours, at a time, ... and to go to bed at eleven o'clock." He would not accept many invitations socially. "A man should have some severity of character, and be able to refuse invitations, etc.," he said. "The fact is, that to become great in science, a man must be nearly as devoted as a lawyer, and must have more than mere talent.... I think I never do so much as when I have fought a battle not to go out." Those who have written books will appreciate this statement, and recall the many days when they have closed the shutters and worked, though they longed to be out-of-doors in the sunlight. In 1833, the year after his marriage, he gave by invitation a course of seven lectures before the Royal Institution, a high honor. In 1834, he passed several months in Sweden, and wrote back to his "dearest Mary,"--"I have been ten hours without a word with my love, but thinking of her more than half the time, and comforting myself that she is less alone than I am." ... He kept a journal for her of his daily work. "It is now twenty-five days that we have been separated, and I have often thought of what you said, that the active occupation in which I should constantly be engaged would give me a great advantage over you. I trust, however, that you also have been actively employed. At leisure moments I have done some things towards planning my next volume. It will be necessary for us to have a work together at fossils at Kinnordy, first, and then in town, and then in Paris." Thus fully had the young wife entered into his studies. In 1835, having received the gold medal of the Royal Society, for his "Principles of Geology,"--now in its fourth edition, which Sir John Herschel said he had read three times,--he was elected president of the Geological Society of London, and made extensive researches in Switzerland, Germany, and Scotland. In 1841, already famous as well as beloved, Lyell was invited to give twelve lectures before the Lowell Institute, in Boston. He and his wife spent thirteen months in the United States, studying the country geologically; its social life, its politics, and our benevolent and educational institutions. Between two and three thousand persons came, both morning and evening, to listen to the distinguished scholar, who had travelled almost the world over to study his beloved science.