He died four years later, tenderly watched over by his illustrious brother, to whom he said in dying, "Think of me often, but always with cheerfulness. I have been very happy, and even to-day has been a glorious day with me, for there is nothing more beautiful than love. I shall soon be with _the mother_, and enter upon a higher order of being." This death was a great blow to Alexander. He said, "I am quite bereft of hope. I did not think that my old eyes could have shed so many tears.... I am the unhappiest of men.... I have lost half of myself." A few months later William's eldest daughter, Caroline, died, to whom Alexander was tenderly attached. From henceforth his life was devoted to his sovereign Frederick William IV., to "Cosmos," and to his ever widening circle of friends. Two thousand letters or more came to him yearly, and till late in life he answered each one, and answered it promptly, showing thereby how truly well bred he was in manner, and how truly kind in heart. In 1834, when he was sixty-five, he began the publication of "Cosmos," in five volumes, the "most comprehensive compendium of modern science." It was soon translated into English, meeting with a cordial reception in that country, and into French, Dutch, and Italian. Even at the age of sixty-five, so eager was he to know more that he attended courses of lectures on Grecian antiquities and literature, and upon chemistry, taking notes among the young university students. He now lived with the king, at Sans-Souci, spending every evening with him, and becoming the confidential friend of both king and queen. When Humboldt was ill, the king would read to him by the hour. Frederick William IV. conferred on him the decoration of the Star of the Red Eagle, the Order of the Black Eagle, the highest honor in the royal power to confer, and the Order of Merit, given to those "who throughout Europe have won for themselves a name either in the arts or sciences." Till the last years of his life Humboldt showed the same marvellous energy and industry. At eighty he said, "I am more than ever filled with a zest for work and literary distinction." When he wrote to friends for information in finishing "Cosmos," he asked for speedy answers, saying, "The dead ride fast." On the fortieth anniversary of his return to Europe, a fête was given in his honor, by the Berlin Academy. Later his bust was placed in the French Institute. The freedom of the city of Berlin was presented to him. America sent him in 1858, on his eighty-ninth birthday, an album of nine maps, showing the scores of towns, counties, rivers, bays, and mountains which had received his name. Letters came from all parts of the world, breathing love and admiration. Yet, with all this honor, he was often lonely, and spoke of the _ennui_ of life. After the regency, Humboldt lived at Berlin, in an unostentatious home, with his attendant, Seifert.