Thomas Jefferson Papers

To Thomas Jefferson from Andrew Ellicott, 31 January 1802

From Andrew Ellicott

Lancaster Jany. 31st. 1802.

Dear Sir

I have lately received some valuable astronomical observations, made at several places on the Mississippi, by my ingenious friend Jose Joahin de Ferrer: by these observations I shall be enabled to make some small corrections in the Map sent on some weeks ago by Mr. Duane; and which I presume has been safely delivered.—

Owing to a great press of business in the land office, and an uncommon portion of cloudy weather, I have made but few observations since I wrote to you last, and those have generally been equal altitudes of the sun, (to determine the error, and rate of going of the Regulator,) and the eclipses of Jupiter’s satellites.—

Our legislature has been in session great part of the winter, but the republican interest has such a decided ascendency, that party violence appears to have wholy subsided in that body.—Govr. Mc.Kean’s firmness, like the club of Hercules, has crushed the opposition, and in all probability secured his reelection.—

With the highest consideration and esteem I am your Hbe. Servt.

Andw; Ellicott

RC (DLC); at foot of text: “Thos. Jefferson President U.S. and of the A.P.S.”; endorsed by TJ as received 4 Feb. and so recorded in SJL.

Ellicott had also used the word Ingenious to describe José Joaquín Ferrer y Cafranga in a letter to TJ in May 1801. Ferrer, who was originally from Spain but spent a good deal of time in North America, traveled down the Ohio and Mississippi rivers from Pittsburgh to New Orleans in the spring of that year. He had two chronometers and made astronomical observations along the journey to determine latitude and longitude of several locations. In 1809, the Transactions of the American Philosophical Society printed his data from that trip along with other sets of his observations. In Europe, Franz Xavier von Zach of Gotha, who regularly published contemporary astronomical data, also printed Ferrer’s observations from the trip down the Ohio and Mississippi (APS description begins American Philosophical Society description ends , Transactions, 6 [1809], 159; John C. Greene, American Science in the Age of Jefferson [Ames, Iowa, 1984], 142; Vol. 30:161–2n; Vol. 34:120–1).

For Ellicott’s description of the map he had prepared of the Mississippi River, see Vol. 35:106–7, 423–4, 548.

It was difficult to regulate a timepiece by observing the exact instant at which the sun reached its zenith at noon. The method of equal altitudes eased this problem by allowing the observer to calculate the moment when noon occurred by measuring the sun’s altitude above the horizon once in the morning and once in the afternoon. Using a telescope, published astronomical tables, and a clock adjusted to local time, one could observe Jupiter’s satellites to find the time difference from Greenwich, and therefore the longitude of the point of observation (Richard S. Preston, “The Accuracy of the Astronomical Observations of Lewis and Clark,” APS description begins American Philosophical Society description ends , Proceedings, 144 [2000], 171–3).

In June 1800, when Thomas McKean was replacing numerous officeholders in Pennsylvania, he declared to John Dickinson that he was no Hercules but had “to cleanse the Augean Stables with little or no aid.” When Ellicott wrote the letter above, some opposition had arisen in the legislature over the fact that Alexander J. Dallas, the U.S. district attorney, was also recorder of the city of Philadelphia. In February 1802, McKean vetoed a bill that would bar Dallas and Michael Leib from dual officeholding. The legislature overrode the veto, but neither Federalists nor disenchanted Republicans could mount much of a challenge to McKean, who faced reelection in the fall of 1802 (Rowe, McKean description begins G. S. Rowe, Thomas McKean, The Shaping of an American Republicanism, Boulder, Colo., 1978 description ends , 320, 326–31).

Index Entries