Baron Humboldt And American Affairs. To the Editor of The N.Y. Tribune. Sir: Baron von Humboldt called my attention a day or two since to a paragraph copied from some other paper into The Semi-Weekly Tribune of May 12, headed "A Huge Pile of Serpents," and beginning thus: "Baron Humboldt says: In the savannahs of Izacubo, Guiana, I saw the most wonderful and terrible spectacle that can be seen," &c. He smiled at the idea of this story being attributed to him, for he never was in the country mentioned, and certainly could never have given such a description of a sight which he never saw anywhere. He spoke of this paragraph however, not on account of any importance he attached to it or its correction, but as affording him an opportunity of mentioning a fact in relation to himself personally, which he requested me to make known through the columns of The Tribune. For some twelve or fourteen years, he says, he has been annoyed by the use of his name by various persons in America, especially in Central and South America, who have, as supposed connections of his, enjoyed and in some cases abused the confidence of generous persons who wished and thought to do him honor. His brother left no children, he himself never married, and he is alone the last of his race. There is no person living who can claim anything as a connection of his. That there may be other persons in the world by the name of Humboldt he of course does not deny, but the probability is that many pretended discoveries in science, which have been promulgated by people calling themselves by that name, have only been the offspring of a desire to swindle and humbug in a more secure and effectual manner. I think, but am not sure, that in this conncetion he spoke of a ridiculous story of some Humboldt or other having five hundred negroes placed in his hands to be experimented on in innoculating for the yellow fever. The long letters which occasionally reach him from America and the West Indies from people who have, as they suppose, cherished members of his family in illness, or otherwise founded a claim upon his notice or friendship, are a serious annoyance, though the scientific absurdities published in the papers under the sanction of his name partake more of the ludicrous. This noble and venerable man, though now some years beyond four score, still retains a lively interest in the progress of our country. To every American whom he meets he speaks of his friends, Jefferson and Gallatin, and laments the change on the question of Slavery which has come over our Government since their day. He speaks of Webster's last days with expressions of the sincerest and deepest regret; nor does he omit any opportunity to impress upon the minds of Americans the deep moral degradation in which the United States as a nation has plunged itself within the last few years. Though an intimate friend of the King, it is said (of course he says nothing of this) that the subject of politics and political affairs is never spoken of between them. From the interest with which he watches the development and progress of the Republican idea in America it would seem that politics must indeed be banished from among the subjects which he can discuss with Frederick William. At his request I showed him on the map the boundaries of the new Territories, Kansas and Nebraskahis map, though recent, dating back beyond the Douglas and Pierce outrage. It is very gratifiying to our national pride to hear his praises of some of our authors, Prescott being, in his opinion, one of the finest, if not the finest, historian now living and writing in the English language. He has several times expressed his wish that he could know that man. Of Prescott's works I think he likes best the "Ferdinand and Isabella." As to the "Conquest of Mexico," could the distinguished author have traveled to Mexico and viewed with his own eyes the scenes he describes, so as to have, in addition to the elegance of his style and extreme accuracy, added the charm of description of scenes he personally knew, Humboldt seems to think the book would have been perfect. It is natural that he should feel something of a want of this kind in a work upon Mexico, but I do not see how a reader who has not the personal recollections of the Baron can feel this want. Parts of Owen's great report upon the Lake Superior region have pleased him much. I was surprised that Whitney's new work on the Mineral Resources of the United States had not reached his notice, for the great chemist, Rose, had made it the subject of several papers before the Geographical Society; but Humboldt seldom goes out to such meetings now. The following passages from a note written soon after reading in the The Tribune the account of the opening of the Panama Railroad, I think may be translated for your paper without any impropriety, as a breach of the sanctity of private correspondence: "Le chemin de fer de Panama a ete propose par moi, des l'Annee 1805, avec le projet beaucoup plus utile et tres executable du canal oceanique du Capica a l'Atrato. "Les tristes debats sur la propagation du systeme de l'esclavage ont hereusement offert l'occasion a quelques ames nobles de prononcer des paroles consolantes. Il ne s'agit pas de demander a la fois l'abolition de l'esclavage, mais d'amener peu a peu des adoucissements dans la legislation actuelle par ne plus vendre l'enfant a la mamelle. La pretention du President dans la lettre a M. Soule de se croire en droit de conquerer l'ile de Cuba lorsque un etat voisin fait mine de rendre sa legislation plus humaine, m'a paru des plus sauvages." I give the following transversion of these paragraphs: "The Panama Railroad was proposed by me as early as 1805, with the imposing project, which would be far more useful and quite as practicable, of an interoceanic Canal between Capica and Atrato. "The sad debates which have taken place on the extension of the system of Slavery have happily offered an opportunity to a few noble souls to speak words of consolation. There is no need of demanding immediately the abolition of Slavery, but of gradually introducing mitigations into the present legislation, so that the babe may no longer be sold from the breast. The claim of the President in his letter to Mr. Soule, that believed he had a right to conquer the Island of Cuba when a neighboring State untertook to render its legislation more humane, appears to me to be a most barbarous one." Tastes may differ, but I would rather have the honor of the approbation expressed in these lines of the noble course pursued by Seward, Sumner and Chase than the title of President, which Pierce wears, so obtained! The approval of Humboldt is worth that of all the men-stealers and women-sellers from the Potomac to the boundary of Mexico. Your obedient servant, AN AMERICAN IN GERMANY. Berlin, Prussia, June 10, 1855.