Agassiz now began work on his "Nomenclator Zoölogicus," and his "Bibliographia Zoölogiæ et Geologiæ," the former comprising "an enumeration of all the genera of the animal kingdom, with the etymology of their names, the names of those who had first proposed them, and the date of their publication." The latter contained a list of all the authors named in the Nomenclator, with notices of their works. This was published by the Royal Society in England, in 1848, the expense being too great for one person. In 1843 the "Fossil Fishes," in five large volumes, was completed, and the following year his "Monograph on the Fossil Fishes of the Old Red Sandstone, or the Devonian System of Great Britain and Russia," was published, a large volume accompanied by forty-one plates. The discovery of these fossils was due to Hugh Miller, whose interesting life and pathetic death will always be associated with the study of the Old Red Sandstone. In the spring of 1846, a great change took place in the life of the overworked naturalist. He had long hoped to visit the United States for scientific investigation, and now the time had come. The King of Prussia, at the request of Humboldt, granted him fifteen thousand francs for this purpose--he had previously given Agassiz one thousand dollars for his glacial researches.... Leaving his wife and daughters with Alexander Braun, her brother, at Carlsruhe, and his son Alexander at school at Neuchâtel, Agassiz said good-by to his students, who came at two o'clock at night, in procession with torchlights. Going to Paris, he spent some time in bringing out his second work upon the glaciers, "Système Glaciaire," receiving the Monthyon Prize of Physiology from the Academy, and sailed for America in September, 1846. Humboldt wrote him from Sans-Souci: "Be happy in this new undertaking, and preserve for me the first place under the head of friendship in your heart. When you return, I shall be here no more, but the king and queen will receive you on this historic hill with the affection which, for so many reasons, you merit. Your illegible but much attached friend." Sir Charles Lyell, of England, who had given a successful course of lectures before the Lowell Institute, Boston, arranged a similar course with Mr. Lowell for his friend Agassiz. Perhaps money has never been given more wisely in our country than by the refined John Lowell, Jr., of Boston, who, dying in a foreign country at thirty-seven, bereft of wife and children, left a quarter of a million dollars to "provide for regular courses of _free_ public lectures upon the most important branches of natural and moral science, to be annually delivered in the city of Boston." None of the bequest could be used for buildings, and ten per cent. of the accumulation of the fund was to be set aside annually to continue it. Since December 1, 1839, from six to ten courses have been given yearly to large audiences, by some of the most distinguished persons in Europe and America.