A few months earlier than the school circular Agassiz issued another prospectus, which had an even more important bearing upon his future work. This was the prospectus for his "Contributions to the Natural History of the United States." It was originally planned in ten volumes, every volume to be, however, absolutely independent, so that the completeness of each part should not be impaired by any possible interruption of the sequence. The mass of original material accumulated upon his hands ever since his arrival in America made such a publication almost imperative, but the costliness of a large illustrated work deterred him. The "Poissons Fossiles" had shown him the peril of entering upon such an enterprise without capital. Perhaps he would never have dared to undertake it but for a friendly suggestion which opened a way out of his perplexities. Mr. Francis C. Gray, of Boston, who felt not only the interest of a personal friend in the matter, but also that of one who was himself a lover of letters and science, proposed an appeal to the public spirit of the country in behalf of a work devoted entirely to the Natural History of the United States. Mr. Gray assumed the direction of the business details, set the subscription afloat, stimulated its success by his own liberal contributions, by letters, by private and public appeals. The result far exceeded the most sanguine expectations of those interested in its success. Indeed, considering the purely scientific character of the work, the number of subscribers for it was extraordinary, and showed again the hold Agassiz had taken upon the minds and affections of the people in general. The contributors were by no means confined to Boston and Cambridge, although the Massachusetts list was naturally the largest, nor were they found exclusively among literary and scientific circles. On the contrary, the subscription list, to the astonishment of the publishers, was increased daily by unsolicited names, sent in from all sections of the country, and from various grades of life and occupation. In reference to the character of this subscription Agassiz says in his Preface: "I must beg my European readers to remember that this work is written in America, and more especially for Americans; and that the community to which it is particularly addressed has very different wants from those of the reading public in Europe. There is not a class of learned men here distinct from the other cultivated members of the community. On the contrary, so general is the desire for knowledge, that I expect to see my book read by operatives, by fishermen, by farmers, quite as extensively as by the students in our colleges or by the learned professions, and it is but proper that I should endeavor to make myself understood by all." If Agassiz, perhaps, overestimated in this statement the appreciation of the reading public in the United States for pure scientific research, it was because the number and variety of his