I have accompanied this by a few sheets of my observations, they contain an account of the work on the boundary as far as to Pearl, or half-way river. The manner of describing the prime vertical as mentioned at the beginning of the line, I have not found noticed by any writer, but should think it too obvious to be new.—I am sorry the plate containing the references is not yet engraved.—

Whilst I was engaged in the City of Washington some years ago I made a number of observations to determine its longitude, but all of them with some papers relative to the plan of the City were lost, when the office was pillaged: But fortunately two very important observations had been communicated to our late worthy friend Mr. Rittenhouse, and published in the 4th. volume of the Transactions of our Society.—The first is on an annular eclipse of the Sun, and the second an occultation of (α ♉︎) Aldebaran by the moon.—Observations of this kind answer very well for the determination of the longitude, but the calculations are critical, and labourious, owing to the moon’s parallax in altitude, latitude, and longitude, and therefore not in common use:—However for want of other materials, and having little to do besides correcting the press, I have gone thro’ the calculations.—

The observation on the eclipse stands as below

			D h  ′  ″
1791 April		Annulas completed at	2 18 35 45		Apparent time		Observed at George
		Annulas broken	2 18 39 57				Town
		End of the eclipse	2 19 52 20				Lat. N. 38° 55’

	h ′  ″
The Longitude by the completion of the Annulas is	5 7 53		West from Greenwich
do   by the breaking of the Annulas	5 8 14
do   by the end of the eclipse	5 8 5

The second observation was made near the meridian of the
Capitol in latitude 38° 52′ 40″ N. and as follows.

			D h  ′  ″
1793 January		α ♉︎ immersed at	21 7 55 49.5		apparent time
		α ♉︎ emerged at	21 9 25 21.5

	h ′ ″
Longitude by the immersion	5 7 13		West from Greenwich
do   by the emersion	5 7 47

The observation on the eclipse was made about 10” west from where the occultation was observed, which when deducted from the eclipse, the results will stand as below for the meridian of the Capitol.

		h ′ ″
Longitude by the completion of the annulas		5 7 43		West from Greenwich
do   by the breaking of the annulas		5 8 4
do   by the end of the eclipse		5 7 55
do   by the immersion of α ♉︎		5 7 13
do   by the emersion of α ♉︎		5 7 47
	Mean	5 7 44.4		= 76° 56′ 6″

From which it appears, (in the language Americans ought to use), that Greenwich is 5h 7′ 44.4″ or 76° 56′ 6″ east from the City of Washington.—

I have been long wanting our longitudes to be reckoned, or counted, from our own Capitol, and not from a place within another country; and for this purpose calculated, and published an Almanac with the sun’s declination, eclipses of ♃trs. Satellites &c. adapted to the meridian of the City of Washington, which I had estimated at 5h 8′ west from Greenwich, but the plan fell thro when I left the City.—

We appear yet to be connected to Great Britain by a number of small ligaments, which tho apparently unimportant, are nevertheless a drawback upon that absolute independence we ought as a nation to maintain.—It would be very well when the longitude of the City of Washington is more accurately settled by a sufficient course of observations, consisting both of the eclipses of ♃trs. Satellites, and lunar distances, to have an American gazetteer published, in which the longitudes should be reckoned east, and west from the Capitol.—Wishing you health and happiness in discharging the important duties of your appointment, I am with sincere respect, and friendship, your Hbl. Servt.