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.
"Natural and moral science!" How broad the subject, and how incalculable the benefit to any city, great or small! What a means for the best general education; what an uplifting of the whole mental and social life of a community!
Agassiz came to Boston and gave twelve lectures on the "Plan of the Creation, especially in the Animal Kingdom." His speech had a foreign accent; but his enthusiastic love of his subject, his skill in drawing on the blackboard, and his eloquent but simple language soon won all hearts.
He was as pleased with the Americans as they were with him. He wrote to his beloved mother (his father had died ten years before): "I can only say that the educated Americans are very accessible and very pleasant. They are obliging to the utmost degree; indeed, their cordiality toward strangers exceeds any that I have met elsewhere.... The liberality of the American naturalists toward me is unparalleled.... The government (of the State of New York) has just completed the publication of a work unique of its kind, a natural history of the State in sixteen volumes, quarto, with plates. Twenty-five hundred copies have been printed, only five hundred of which are for sale, the rest being distributed throughout the State. Four volumes are devoted to geology and mining alone; the others, to zoölogy, botany, and agriculture. Yes, twenty-five hundred copies of a work in sixteen volumes, quarto, scattered throughout the State of New York alone!
"When I think that I began my studies in natural history by copying hundreds of pages from a Lamarck which some one had lent me, and that to-day there is a state in which the smallest farmer may have access to a costly work, worth a library to him in itself, I bless the efforts of those who devote themselves to public instruction."
Agassiz was at once asked to give a second course before the Lowell Institute, on glaciers. This, like the first, was greatly enjoyed by the two thousand or more persons present. Invitations now came from other cities, but he said, "I will limit myself to what I need in order to repay those who have helped me through a difficult crisis.... Beyond that all must go again to science,—there lies my true mission."
He passed his fortieth birthday, May 28, 1847, with Dr. B. E. Cotting, curator of the Lowell Institute, at whose home he had stayed through some weeks of illness. His host, seeing him standing thoughtfully at the window, said, "Why so sad?"
"That I am so old and have done so little," was the reply.
In the summer of 1847, Agassiz rented a small house in East Boston, sufficiently near to the ocean to study marine animals. He also gave lectures in New York, Philadelphia, Albany, and other eastern cities.