In the winter of 1865 it became necessary for me, on account of some disturbance of my health, to seek a change of scene and climate, with rest from work. Europe was proposed; but though there is much enjoyment for a naturalist in contact with the active scientific life of the Old World, there is little intellectual rest. Toward Brazil I was drawn by a lifelong desire. After the death of Spix, when a student of twenty years of age, I had been employed by Martius to describe the fishes they had brought back with them from their celebrated Brazilian journey. From that time, the wish to study this fauna in the regions where it belongs had been an ever-recurring thought with me; a scheme deferred for want of opportunity, but never quite forgotten. The fact that the Emperor of Brazil was deeply interested in all scientific undertakings, and had expressed a warm sympathy with my efforts to establish a great zoÖlogical museum in this country, aiding me even by sending collections made expressly under his order for the purpose, was an additional incentive. I knew that the head of the government would give me every facility for my investigations. Nevertheless, tempting as was the prospect of a visit to Brazil, as a mere vacation it had little charm for me. Single-handed, I could make slight use of the opportunities I should have; and though the excursion might be a pleasant one for myself, it would have no important result for science. I could not forget that, had I only the necessary means, I might make collections on this journey which, whenever our building could be so enlarged as to give room for their exhibition, would place the Museum in Cambridge on a level with the first institutions of the kind. But for this a working force would be needed, and I saw no possibility of providing for such an undertaking. While I was brooding over these thoughts I chanced to meet Mr. Nathaniel Thayer, whom I have ever found a generous friend to science. The idea of appealing to him for a scheme of this magnitude had not, however, occurred to me; but he introduced the subject, and, after expressing his interest in my proposed journey, added, “You wish, of course, to give it a scientific character; take six assistants with you, and I will be responsible for all their expenses, personal and scientific.” It was so simply said, and seemed to me so great a boon, that at first I hardly believed I had heard him rightly. In the end, I had cause to see in how large and liberal a sense he proffered his support to the expedition, which, as is usual in such cases, proved longer and more costly than was at first anticipated. Not only did he provide most liberally for assistants, but, until the last specimen was stored in the Museum, he continued to advance whatever sums were needed, always desiring me to inform him should any additional expenses occur on closing up the affairs of the expedition. It seems to me that the good arising from the knowledge of such facts justifies me in speaking here of these generous deeds, accomplished so unostentatiously that they might otherwise pass unnoticed.

All obstacles thus removed from my path, I made my preparations for departure as rapidly as possible. The assistants I selected to accompany me were Mr. James Burkhardt as artist, Mr. John G. Anthony as conchologist, Mr. Frederick C. Hartt and Mr. Orestes St. John as geologists, Mr. John A. Allen as ornithologist, and Mr. George Sceva as preparator. Beside these, my party was enlarged by several volunteers, to whom I was indebted for assistance as untiring and efficient as if they had been engaged for the purpose. These were Mr. Newton Dexter, Mr. William James, Mr. Edward Copeland, Mr. Thomas Ward, Mr. Walter Hunnewell, and Mr. S. V. R. Thayer. I should not omit to mention my brother-in-law, Mr. Thomas G. Cary, as one of my aids; for, though not nominally connected with the expedition, he made collections for me at Monte Video, Buenos Ayres, and other places. I was also joined by my friends Dr. and Mrs. Cotting. Dr. Cotting, like myself, was in need of a vacation, and it was his intention to remain with us for as long a time as he could spare from his professional practice. But the climate proved unfavorable to his health, and after passing a couple of months in Rio, and sharing with us all our excursions in that neighborhood, he sailed with Mrs. Cotting for Europe, where they passed the summer. His presence with us during that time was most fortunate, for it so happened that the only serious cases of illness we had among us occurred before he left, and his medical advice and care were of great service. I lost the assistance of Mr. Anthony, and Mr. Allen also, early in the expedition; their health, always delicate, obliging them to leave for home. With these exceptions, our working force remained intact, and I am happy to state that every member of the party returned in safety to the United States.^[1]

No sooner was the Brazilian Expedition known to the public, than I received a letter from Mr. Allen McLane, President of the Pacific Mail Steamship Company, offering to me and my whole party the hospitality of their magnificent ship the Colorado, then just sailing from New York for the Pacific coast. She was going almost empty of passengers, being bound by the way of Cape Horn for San Francisco. We left New York on board this beautiful vessel, on the 1st of April, 1865. The record of our delightful voyage to Rio de Janeiro will be found in the narrative; but I wish here publicly to acknowledge my obligation to Mr. McLane for his generosity to the expedition. Besides the sympathy accorded me by private individuals, I have to thank the Hon. Gideon Welles, Secretary of the Navy, for a general order, received on the eve of my departure, desiring the officers of the United States Navy, wherever I should fall in with them, to afford me such assistance in my scientific researches as would not interfere with the regular service; and I learned at Rio that Mr. Seward had warmly recommended the expedition to General Webb, at that time United States Minister to Brazil. Finally, I would express my thanks also to Messrs. Garrison and Allen for the free passage offered to myself and my companions for our return, on board the line of steamers established between New York and Rio de Janeiro during our stay in Brazil.

It will be seen hereafter what facilities were granted me throughout this journey by the Brazilians themselves, and that the undertaking, so warmly speeded on its way, was welcomed no less cordially in the country to which it was bound.

One word as to the manner in which this volume has grown into its present shape, for it has been rather the natural growth of circumstances than the result of any preconceived design. Partly for the entertainment of her friends, partly with the idea that I might make some use of it in knitting together the scientific reports of my journey by a thread of narrative, Mrs. Agassiz began this diary. I soon fell into the habit of giving her daily the more general results of my scientific observations, knowing that she would allow nothing to be lost which was worth preserving. In consequence of this mode of working, our separate contributions have become so closely interwoven that we should hardly know how to disconnect them, and our common journal is therefore published, with the exception of a few unimportant changes, almost as it was originally written. In this volume I have attempted only to give such an account of my scientific work and its results as would explain to the public what were the aims of the expedition, and how far they have been accomplished. It is my hope to complete a work, already begun, on the Natural History, and especially on the Fishes of Brazil, in which will be recorded not only my investigations during the journey and those of my assistants in their independent excursions, but also the researches now regularly carried on in connection with the immense Brazilian collections stored in the Museum at Cambridge. This must, however, be the slow labor of many years, and can only be published very gradually. In the mean time I hope that this forerunner of the more special reports may serve to show that our year in Brazil, full as it was of enjoyment for all the party, was also rich in permanent results for science.