BARON HUMBOLDT ON AMERICAN SLAVERY.

The following highly-interesting extract is taken from a recent number of the New- York Tribune. It is from a private letter, addressed by the venerable philosopher to his friend, Mr. Julius Froebel, an author of distinction.

The Baron's testimony against Slavery adds one more to "the host of witnesses" who have raised their voice in condemnation of this iniquity.

The editor of the Tribune publishes it with the Baron's consent.

"Accept, my dear Froebel, if only in a few lines, my most cordial thanks for your kind letter and for the gift of an able work on your personal experience in America, in which you have submitted all classes of society to such a sagacious comparison.

You are here warmly cherished in the memory of all who are acquainted with your distinguished scientific attainments, the nobleness of your character, and the peculiar features of your mind. I have boasted of your enduring friendship with me in the new volume of Kosmos, p. 541. I closed this volume just as I received the first part of your travels and researches, which had already often been described to me by friends, and especially by Varnhagen von Ense. I trust I shall not lose your favour on account of my differing from you in regard to the connection between the North Mexican highlands and the Rocky Mountains.

Our controversy, as you will find when you read attentively (pp.

431--440), is almost entirely one of words.

I make a distinction between a broad, continuous elevation, and the disconnected chain rising above it, often steeply and like battlements.

The word mountain is very indefinite.

In spite of my heretical disposition, however, your ninth chapter (pp.

504--518) gives me a great deal of instruction.

You have explained many points which were only hinted at in the "Remarks (Contributions to Phys.

Geog., Smithson.

Inst.)

But there are other things which come nearer my heart than those elevations.

Your next volume on the political future of America would I, almost the original Adam, gladly live to see.

Continue to brand the shameful devotion to slavery, the treacherous importation of negroes, under the pretence of their becoming free--a means to stimulate the hunting of negroes in the interior of Africa.

What atrocities have been witnessed by one who has had the misfortune to live from 1789 to 1858.

My book against Slavery (Political Essay on the Island of Cuba) is not prohibited in Madrid, but cannot be purchased in the United States, which you call "The Republic of distinguished people," except with the omission of every thing that relates to the sufferings of our coloured fellow-men, who, according to my political views, are entitled to the enjoyment of the same freedom with ourselves.

Add to this, the anathema on other races of men, forgetting that the most ancient cultivation of humanity, before that of the white Hellenic race in Assyria, in Babylon, in the valley of the Nile, in Iran, in China, was the work of coloured men, though not woolly-haired.

"I still work hard, mostly in the night, because I am unmercifully tormented with a constantly increasing correspondence, for the most part of not the slightest interest.

I live joyless in my 89th year, because, of the much for which I have ardently striven from my early youth so little has been accomplished.

"With renewed expressions of the friendship of many years, which political events have never troubled, I am ever your illegible

Al. Humboldt.

Berlin, January 11, 1858.