City of Washington, May 29th 1823.
Since the close of the last session of Congress, I have turned my attention to a strict examination of such parts of my astronomical calculations, given in abstract, as relate to solar eclipses and occultations of fixed Stars by the Moon, by various methods and rules, referring to the equator, as well as to the Ecliptic, that the results contained in the report made in November, 1821, might be impartially tested, and their accuracy or defects exhibited to the view of Congress at their next session,—The coincidence obtained by the use of those different methods and rules, in the Moon’s parallaxes in longitude and latitude, must prove to the Conviction of every intelligent and unprejudiced mind, that the principles on which the work is founded, and the process connected therewith, are correct. On comparing the results thus determined, with those given in the report, I find a variance of only 5 feet, 9 inches of our admeasurement, or about 1/16 of a second of longitude,—I have always thought, that occultations and Solar eclipses were the best methods which can be adopted to obtain an accurate result of the longitude of a place, because the process of calculation admits of a reduction of both the latitude, as referred to the centre of the Earth, and of the Moon’s equatorial horizontal parallax, according to the true or spheroidal form of the Earth.
Having proposed the subject of a first meridian to the Consideration of Congress, in December, 1809, and called their attention repeatedly to its establishment since that time, I am unwilling to see it abandoned, or the efforts made to lay a foundation, under-rated or disregarded. A permanent Security of our independence on foreign kingdoms or States, in this respect, and the dissemination of knowledge among our fellow-citizens relating to an useful branch of science, were contemplated by me, when the original calculations were submitted, and I have spared no labor or effort which I supposed might contribute to an ultimate completion of this national object. A commencement, it is true, has been made, and Sanctioned by the constituted authorities of the government; but if it be allowed to stop here, all that has been done, will be of little or no importance; for if the distance between the meridians of the Capital, in Washington, and Greenwich, were ascertained to a hair’s breadth, it would be of no use to our mariners and geographers. A first meridian for any country, is a national concern, and must be confirmed, and decided on by its government, otherwise, the exertions of one or more individuals to establish it, are, and must be unavailing.
I have taken the liberty to state to you, in what manner my time has been employed; and should be much gratified to have my work, in manuscript, examined by some competent person, friendly disposed to its author, and interested in the accomplishment of the object he has long had in view. I am now, and have been for some time past, of opinion, that without the active, persevering exertions of influential lovers of science, whose station and character in society entitle their opinions to peculiar respect, all that I have done, or can do, for the establishment of a national meridian for the United States, will fall to the ground, and be as little regarded as the “baseless fabric of a vision.”
DLC: Papers of Thomas Jefferson.