On July 9, 1804, after five years of absence, he set sail for France. Europe received him with universal joy. He had been reported dead. He was thirty-five, handsome, and famous. He had travelled over forty thousand miles, and brought back over sixty thousand specimens of plants. He was made a member of the Royal Academy of Sciences in Berlin, and later a member of the Legion of Honor, and of about one hundred and fifty other societies; indeed, of all the great associations of the land. And now the result of his travels must be given to the world in books. While he was preparing them, he yet found time to spend months together in the École Polytechnique, experimenting in chemistry with his devoted friend Gay-Lussac; with Biot, he made investigations in magnetism; with Arago, in astronomy; with Cuvier, in anatomy. Most of the time from 1808 to 1827, nineteen years, he remained in Paris, devoting his time to his great work. In the forenoons he usually studied and experimented; from twelve to seven he wrote, and then, if his evenings were spent socially, he wrote again from midnight till half-past two, usually allowing himself only four hours for sleep. So popular was he that he often went to five receptions in an evening. Year after year his works on America appeared, till twenty-nine volumes were published! The first part was entitled, "Voyage in the Equatorial Regions of the New Continent." This described a portion of his journey in three volumes; views of the Cordilleras and the native peoples of America, one volume with sixty plates; an atlas of the new continent, with thirty-nine maps; a critical examination of the history of the geography of the middle ages, in five volumes. The second part related largely to zoölogy and comparative anatomy in the new regions; the third part related chiefly to Mexico; the fourth part to astronomical observations, measurement with the barometer, etc.; the fifth part, geology, and the geography of plants; the sixth part, plants in Mexico, Cuba, and South America, in two volumes, with nearly one hundred and fifty engravings; two volumes more, with one hundred and twenty colored plates; seven volumes of new species, with seven hundred engravings, and several other books. The expense of bringing out these works was enormous; the copper-plate illustrations cost in printing and paper alone about one hundred and seventy thousand dollars. As the price of the volumes was about twenty-seven hundred dollars, the number of purchasers was comparatively limited. Humboldt had used all his fortune in his journeys and in publishing his books, and was now a poor man, dependent upon a pension from his king. But he was the pride of his nation, and beloved in France as well.