. . .I returned day before yesterday from my trip in Wurtemberg, and though I already knew what precautions had been taken everywhere in anticipation of cholera, I do not think my journey was a useless one, and am convinced that my observations will not be without interest,--chiefly for myself, of course, but of utility to others also I hope. Your letter being so urgent, I will not, however, delay my departure an instant. Between to-day and to-morrow I shall put in order the specimens lent me by the Museum, and then start at once. . .In proportion to my previous anxiety is my pleasure in the prospect of going to Paris, now that I am better fitted to present myself there as I could wish. I have collected for my fossil fishes all the materials I still desired to obtain from the museums of Carlsruhe, Heidelberg, and Strasbourg, and have extended my knowledge of geology sufficiently to join, without embarrassment at least, in conversation upon the more recent researches in that department. Moreover, Braun has been kind enough to give me a superb collection, selected by himself, to serve as basis and guide in my researches. I leave it at Carlsruhe, since I no longer need it. . .I have also been able to avail myself of the Museum of Carlsruhe, and of the mineralogical collection of Braun's father. Beside the drawings made by Dinkel, I have added to my work one hundred and seventy-one pages of manuscript in French (I have just counted them), written between my excursions and in the midst of other occupations. . .I could not have foreseen so rich a harvest. Thus prepared, he arrived in Paris with his artist on the 16th of December, 1831. On the 18th he writes to his father. . ."Dinkel and I had a very pleasant journey, though the day after our arrival I was so fatigued that I could hardly move hand or foot,--that was yesterday. Nevertheless, I passed the evening very agreeably at the house of M. Cuvier, who sent to invite me, having heard of my arrival. To my surprise, I found myself not quite a stranger, --rather, as it were, among old acquaintances. I have already given you my address, Rue Copeau (Hotel du Jardin du Roi, Numero 4). As it happens, M. Perrotet, a traveling naturalist, lives here also, and has at once put me on the right track about whatever I most need to know. There are in the house other well-known persons besides. I am accommodated very cheaply, and am at the same time within easy reach of many things, the neighborhood of which I can turn to good account. The medical school, for instance, is within ten minutes' walk; the Jardin des Plantes not two hundred steps away; while the Hospital (de la Pitie), where Messieurs Andral and Lisfranc teach, is opposite, and nearer still. To-day or to-morrow I shall deliver my letters, and then set to work in good earnest."