From Robert Patterson
Philada March 12th 1811
Agreeably to your desire I send herewith Garnetts’ Nautical Almanacs for the years 11. & 12—& shall not fail, life remaining, to forward those for succeeding years as soon as published.
I have lately added to the common artificial horizon, (the polished plane surface adjusted by a spirit-level) a very simple appendage, by the aid of which any altitude of the sun &c may be taken, on land, from 0 to 90°, either by the common octant or sextant, with the utmost ease & accuracy—a desideratum, so far as I know, hitherto unattained, in the use of this valuable instrument.
Instead of giving you a description of this apparatus, I request you will permit me to send you one, with directions for its use. It is no larger than a moderate sized snuff-box. By what conveyance can I forward it?—
RC (MHi); endorsed by TJ as received 17 Mar. 1811 and so recorded in SJL. Enclosures: John Garnett, The Nautical Almanac and Astronomical Ephemeris (New Brunswick, 1803–13; Sowerby, description begins E. Millicent Sowerby, comp., Catalogue of the Library of Thomas Jefferson, 1952–59, 5 vols. description ends no. 3810), editions for 1811 and 1812.
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