In 1833 he was enabled by the liberality of Humboldt, who had been his devoted friend since the commencement of their acquaintance in Paris, to begin the publication of the great work on the fossil fishes. This is in 5 volumes, with a folio atlas containing about 400 plates. About 1,000 species are described and figured in the natural size, with the colors of their beds, and there are short indications of about 700 more. The discovery and description of so many new species led to the recognition of new types, and an entirely new classification, based chiefly on the characters of importance in the fossils. The great generalizations to which these researches led have stood the test of time, and have been strengthened and extended by later investigations. The geological results of those researches were remarkable. The relative ages of the formations in which the fossil fishes were found were more clearly established by comparisons of their structures. Moreover, the fossil species differ from those now living, and differ in different stages of the same formation, as well as in different formations, leading to the conclusion that our globe has been peopled by a series of creative acts; and, as peculiar species occur in certain regions and not elsewhere, that these creations were not only successive but local, each having assigned to it a natural limit - man alone, and the animals associated with him, forming the exceptions to this last general law.

From this general survey Agassiz drew several very important conclusions respecting the relation of the Creator to the universe. The existence of a superior intelligence, whose power alone could establish and sustain such an order of things, he considers to have been established by rigid demonstration, and on a truly scientific foundation. He believes that species do not insensibly pass into each other, but each has its appointed period, and is not connected, except in the order of time, with its predecessor. "An invisible thread, in all ages, runs through this immense diversity, exhibiting as a general result the tact that there is a continual progress in development, ending in man, the four classes of vertebrates presenting the intermediate steps, and the invertebrates the constant accessory accompaniment. Have we not here the manifestations of a mind as powerful as prolific ? the acts of an intelligence as sublime as provident ? the marks of goodness as infinite as wise? the most palpable demonstration of the existence of a personal God, author of all things, ruler of the universe, and dispenser of all good ? This, at least, is what I read in the works of creation." Such is the tone of the closing part of the chapter on classification.

Prof. Agassiz visited England several times, and was everywhere received with respect and enthusiasm. The universities of Edinburgh and Dublin conferred on him the degree of LL.D., and the corporations enrolled him among their citizens. He was the guest of Sir Robert Peel, and Lord Egerton, afterward Lord Ellesmere, and Sir Philip Egerton, honored him with a lifelong friendship. Of the eminent naturalists, Buckland, Owen, and Sir Roderick Murchison should be enumerated as among his friends. In 1834 his "Prodromus of the Echinoderms" appeared, which was soon followed by his monographs on that class of animals, in the preparation of which he was aided by Prof. Valentin and Mr. Desor. During this period he continued to collect materials for his "History of the Fresh-water Fishes." He formed a lithographic establishment at Neufchatel, where the plates for the atlas of this work were executed, and the prints struck off under his own eye. The great expense, however, exhausted his pecuniary resources, and he not only found it impossible to continue it on the original plan, but it entailed upon him a heavy debt, which cost him the labors of many subsequent years to pay off.

In the elaboration of some portions of the subject he was assisted by Karl Vogt, a Swiss naturalist, distinguished for his zeal and attainments in zoology. The publication of the "Fresh-water Fishes," in 1839-'40, was followed by the Nomenclator Zoologicus, con-taining an enumeration of all the genera in the animal kingdom, with the etymology of their names, the names of those who first proposed them, the date of their publications, etc. This J work was founded upon registers, in which Agassiz entered the names of the animals as they occurred in his studies. They were then methodically arranged, the nomenclature of each class being submitted to the revision of naturalists distinguished for their investigations in each special branch. This was accompanied by another extensive and important work, the Bibliotheca Zoologice et Geologiae, containing a list of the authors mentioned in the former, with notices of their writings. This work, published at the expense of the Ray society in England, has appeared since the author's residence in the United States, with emendations and additions by H. Strickland and Sir W. Jardine, in 4 large octavo volumes. - From 1836 to 1845 Agassiz spent his summer vacations among the Alps, chiefly engaged in the J study of the glaciers and the geological phe-nomena they produce.

The indications of their greater extension in a former period, and the traces they have left upon the surface of the earth, were carefully followed through the countries adjoining Switzerland, as well as England, Scotland, and Ireland. Before him, De Saussure, Venetz, Charpentier, and others, had written upon the glaciers, and the distribution of bowlders over the valley of Switzerland. De Saussure's theory of their distribution referred it to the action of water. The idea of glacial agency in transporting bowlders appears to have originated among the chamois hunters, who had noticed the fact that every i year huge masses of rock were moved by glaciers from their original position. This idea was adopted by Venetz, and extended by Charpentier, who explained the distribution of the bowlders throughout the valley of Switzerland, and on the slopes of the Jura, by the extension of glaciers beyond their present limits in a former period. In 1836 Agassiz visited Charpentier, and accompanied him to the glacier of the Diablerets, where he saw the actual transportation of the bowlders by the glacier, and the rounding and polishing of the rocks at its sides. These observations removed his former doubts.