City of Washington, 26th. Decr. 1804.
I had the honor to receive this morning, with the high respect it deserves, your very friendly and polite communication of the 22d. instant. Since I submitted to you the result of my calculations, I have ascertained with a degree of precision which may be confidently relied on, the latitude of the place of observation, which I find to be 38.° 53.’ 30.9", or in whole numbers 38.° 53.’ 31." from which I intend to calculate both by the immersion and emersion, the longitude from Greenwich, considering the earth, in the first instance, as a perfect sphere, and afterwards taking into view its true form, that of an oblate spheroid: When I have finished these calculations, I intend, if you will please to accept of it, to furnish you with a copy, which I am well persuaded, will be more accurate than that you have seen. The method you have proposed in your valuable communication to me, is one of the best and most to be depended on of any which has been discovered for ascertaining the longitude of places on the Earth; but as I have no instruments for taking necessary observations of my own, I was willing to avail myself of the opportunity that offered on the 20th. of October last, although I was well aware of the labor, and consequently, the liability to error, which would attend the calculations.
With the most sincere and perfect respect, I have the honor to be, Sir, Your most obedient servant,
DLC: Papers of Thomas Jefferson.