Humboldt and Fremont.

Among the scientific honors paid to Col.

Fremont, as a pioneer of American discovery, certainly not the least notable was that conferred by the King of Prusia in "the great Golden Medal of Progress in the Sciences."

The manner of its communication added a rare value to the gift.

It was sent with a most complimentary letter of Baron Humboldt, who took occasion to add the warmest expressions of his own personal respect and admiration.

As this letter has apparently been overlooked in the notices recently made of Fremont by the press, we avail ourselves of the advance sheets of the new biography in the course of publication by Derby & Co., of this city, to lay it before our readers.

One sentence of Humboldt's letter we have marked in italics; it was a conscientious tribute paid to the Senator then; it is highly significant of Fremont's "friendship to liberty and to the "progress of intelligence" now.

The following isthe English translation of Baron Humboldt's letter:

"To Col.

Fremont, Senator--It is very agreeable to me, Sir, to address you these lines by my excellent friend, our Minister to the United States, M. de Gerolt.

After having given you, in the new edition of my 'Aspects of Nature,' the public testimony of the admiration which is due to your gigantic labors between St. Louis, of Missouri, and the coasts of the South Sea, I feel happy to offer you, in this living token, (dans ce petit signe de vie,) the homage of my warm acknowledgment.

You have displayed a noble courage in distant expeditions, braved all the dangers of cold and famine, enriched all the branches of the natural sciences, illustrated a vast country which was almost entirely unknown to us.

"As merit so rare has been acknowledged by a sovereign warmly interested in the progress of physical geography; the King orders me to offer you the grand golden medal destined to those who have labored at scientific progress.

I hope that this mark of the Royal good will, will be agreeable to you at a time when, upon the proposition of the illustrious geographer, Chas.

Ritter the Geographical Society at Berlin has named you an honorary member.

For myself I must thank you particularly also for the honor which you have done in attaching my name and that of my fellow laborer and intimate friend, Mr. Bonpland, to countries neighboring to those which have been the object of our labors.

California, which has so nobly resisted the introduction of Slavery, will be worthily represented by a friend of Liberty and of the progress of intelligence.

"Accept, I pray you, Sir the expression of my high and affectionate consideration.

"Your most humble and most obedient servant A. V. HUMBOLDT.

"Sans Souci, October 7, 1850."

On the envelope thus addressed: "To Colonel Fremont.

Senator.

With the great Golden Medal For progress in the sciences.

Baron Humboldt."

The following is the description of the medal: "Of fine gold, massive, more than double the size of the American double eagle, and of exquisite workmanship.-- On the face is the medallion head of the King, Frederic- William the Fourth, surrounded by figures emblematical of Religion, Jurisprudence, Medicine, and the Arts.

On the reverse , Apollo , in the chariot of the Sun, drawn by four high-mettled, plunging horses, traversing the zodiac, and darting rays of light from his head."

The following is the public testimony of the Baron's admiration of the gigantic labors of Fremont, referred to in the letter, as contained in the new or third editions of his "Aspects of Nature," and which, as a reference, becomes a natural appendant to the letter:

"Fremont's map and geographical investigations comprehend the extensive region from the junction of the Kansas River with the Missouri to the Falls of the Columbia and to the missions of Santa Barbara and Puebla de los Angeles, in New California; or a space of 28 degrees of longitude, and from the 34th to the 45th parallel of latitude . Four hundred points have been determined hyposometrically by barometric observations, and, for the most part, geographically by astronomical observations; so that a district which, with the winding of the route, amounts to 3,600 geographical miles, from the mouth of the Kansas to Fort Van Couver and the shores of the Pacific, (almost 720 miles more than the distance from Madrid to Tobolsk,) has been represented in profile, showing the relative hights above the level of the sea.

"As I was, I believe, the first person who undertook to represent, in geognostic profile, the form of entire countries--such as the Iberian Peninsula, the high lands of Mexico, and the Cordilleras of South America, (the semi-perspective projections of a Siberian traveler, the Abbe Chappe, were founded on mere and generally ill-judged estimations of the fall of rivers)--it has given me peculiar pleasure to see the geographical method of representing the form of the earth in a vertical direction, on the elevations of the solid portion of our planet above its watery covering, applied on so grand a scale as has been done in Fremont's map."