I am loth to have my name added to the list of people who break in upon your retirement.—

The Ambition of the correspondence of the first man of the age would not have induced me to violate the Laws of politeness by making such an intrusion1 upon a man whom I have never seen. But the known interest which you feel in whatever relates to the Geology or topography of our country & your critical information upon that subject must furnish my apology.—

I have been appointed by the executive amongst other matters to make a survey of the Blue Ridge Mountain from James River until it Crosses itself in the Allegany & thence along the last mentioned mountain2 to north Carolina

In the prosecution of this survey, I have at sundry places endeavored to ascertain the elevation of the mountains above3 their bases, & In ascending Roanoak & Stanton Rivers I have endeavored to Calculate the extend of fall from the Blue Ridge to tide water. I had no other means of observations than a Quadrant & the difficulty of getting a proper base for one side of the triangles has I fear rendered some of the estimates incorrect—This difficulty at the Peaks of Otter was sufficient to deter me from the attempt & understanding, that you had made very particular calculations of its height at a date greatly posterior to your Notes upon Virginia, I have thrown myself entirely upon your mercy under the belief that the Executive as well as the public will be better satisfied with your calculations than any I could make.—

Will you therefore be pleased to communicate to me the result of your Calculations & in what manner they were made whether with a Barometer or not? That I believe is the present common way of calculating the heights of Mountains Tho where a desirable base Can be obtained & an instrument of a considerable length of Radius certainly not the most correct—

To my great astonishment I found that part of the Alleganys on the Ridge that divides the waters, making the County Line between Montgomery & Grayson on the one side and Franklin & Patrick on the other No mountain at all, But the whole Country West presenting the appearance of a level & almost smooth surface,4 while it terminated on the east by a perpendicular pitch of nearly 2000 feet, presenting from the last mentiond Counties the View of a wall, or prodigious5 embankment of mountains of the above mentiond height.—

Will you be pleased to inform whether that is the case generally with the Allegany in the north section of the State & in the other States or not?—

If the Earth were a perfect sphere would it follow that the tides every where would determine the level of the Country, or that the Radius of the Earth from the Centre6 to the head of tide water in the St Lawrence would be just as long as another7 radius proceeding from the Centre to the head of tide water in James River? Or what is the same thing does that circumstance determine the length of such Radii every where in the same parallel—?—