Shall I tell you anything of my own poor and superannuated works? The sixth volume is wanting to my "Geography of the Fifteenth Century" (Examen Critique). It will appear this summer. I am also printing the second volume of a new work to be entitled "Central Asia." It is not a second edition of "Asiatic Fragments," but a new and wholly different work. The thirty-five sheets of the last volume are printed, but the two volumes will only be issued together. You can judge of the difficulty of printing at Paris and correcting proofs here,--at Poretz or at Toplitz. I am just now beginning to print the first number of my physics of the world, under the title of "Cosmos:" in German, "Ideen zur erner physischen Weltbeschreibung." It is in no sense a reproduction of the lectures I gave here. The subject is the same, but the presentation does not at all recall the form of a popular course. As a book, it has a somewhat graver and more elevated style. A "spoken book" is always a poor book, just as lectures read are poor however well prepared. Published courses of lectures are my detestation. Cotta is also printing a volume of mine in German, "Physikalische geographische Erinnerungen." Many unpublished things concerning the volcanoes of the Andes, about currents, etc. And all this at the age when one begins to petrify! It is very rash! May this letter prove to you and to Madame Agassiz that I am petrifying only at the extremities, --the heart is still warm. Retain for me the affection which I hold so dear. A. DE HUMBOLDT. In the following winter, or, rather, in the early days of March, 1841, Agassiz visited, in company with M. Desor, the glacier of the Aar and that of Rosenlaui. He wished to examine the stakes planted the summer before on the glacier of the Aar, and to compare the winter and summer temperature within as well as without the mass of ice. But his chief object was to ascertain whether water still flowed from beneath the glaciers during the frosts of winter. This fact would have a direct bearing upon the theory which referred the melting and movement of the glaciers chiefly to their lower surface, explaining them by the central heat of the earth as their main cause. Satisfied as he was of the fallacy of this notion, Agassiz still wished to have the evidence of the glacier itself. The journey was, of course, a difficult one at such a season, but the weather was beautiful, and they accomplished it in safety, though not without much suffering. They found no water except the pure and limpid water from springs that never freeze. The glacier lay dead in the grasp of winter. The results of this journey, tables of temperature, etc., are recorded in the "Systeme Glaciaire."