I feel the need of expressing it to some one who will understand me, and your sympathy would make me the happiest of mortals. I am so pursued by this thought of a scientific journey that it presents itself under a thousand forms, and all that I undertake looks toward one end. I have for six months frequented a blacksmith's and carpenter's shop, learning to handle hammer and axe, and I also practice arms, the bayonet and sabre exercise. I am strong and robust, know how to swim, and do not fear forced marches. I have, when botanizing and geologizing, walked my twelve or fifteen leagues a day for eight days in succession, carrying on my back a heavy bag loaded with plants or minerals. In one word, I seem to myself made to be a traveling naturalist. I only need to regulate the impetuosity which carries me away. I beg you, then, to be my guide." The unfinished letter closes abruptly, having neither signature nor address. Perhaps the writer's courage failed him and it never was sent. An old letter (date 1827) from Cuvier to Martius, found among Agassiz's papers of this time, and containing the very notes on the Spix Fishes to which allusion is here made, leaves no doubt, however, that this appeal was intended for the great master who exercised so powerful an influence upon Agassiz throughout his whole life. In the spring of 1829 Agassiz took his diploma in the faculty of philosophy. He did this with no idea of making it a substitute for his medical degree, but partly in deference to Martius, who wished the name of his young colleague to appear on the title-page of the Brazilian Fishes with the dignity of Doctor, and partly because he believed it would strengthen his chance of a future professorship. Of his experience on this occasion he gives some account in the following letter:-- TO HIS BROTHER. MUNICH, May 22, 1829.