The venerable Alexander Von Humboldt, in a letter to a German periodical, complains that a testimony which he bore against American Slavery, in a work on Cuba, is omitted in the American reprint. The expunged passage is as follows:--"I have freely examined everything concerning the organization of society in the colonies, the unequal division of the rights and privileges of life, those sources of danger which may be avoided by the wisdom of legislators and the moderation of free men under any form of government. It belongs to the traveller who has closely watched the torture and degradation of human nature, to see that the complaints of misfortune reach those whose duty it is to solace them. In this expose I have shown how much less inhuman and atrocious the old Spanish slave laws are than those of the Slave States on the Continent of America north and south of the equator."