The following letters of Humboldt contain materials of inestimable importance for forming a true, legitimate, and unveiled picture of his mind and character. It was his will and desire that they should be made public at his death, as will be seen distinctly expressed in the extract on a previous page. Nowhere has he expressed himself with less reserve or more sincerity than in his intercourse with Varnhagen, his long tried and trusty friend, whom he loved and valued above all others. In him he reposed the most unreserved confidence, and although ordinarily in the habit of destroying most of the letters addressed to him, it was with Varnhagen that he deposited such as he considered important and desired to have preserved. He reckoned upon Varnhagen, who was the younger of the two, surviving him.

Varnhagen, however, died first, and transferred to me the duty, now become doubly such, of publishing these wondrous records of the life, activity, and habits of thought of this great man. In fulfilling so sacred a duty it became an act of piety to let every word remain exactly as it was written down. To have presumed to alter his expressions would indeed have been to offer an insult to the shade of Humboldt!