To Nevil Maskelyne
ALS: the Royal Society
Craven street Feb. 12. 1770
I have just received a Letter from Mr. Winthrop, dated Dec. 7. containing the following Account, viz.
“On Thursday the 9th of November, I had an Opportunity of observing a Transit of Mercury. I had carefully adjusted my Clock, to the apparent Time, by correspondent Altitudes of the Sun, taken with the Quadrant for several Days before; and with the same Reflecting Telescope as I used for the Transit of Venus, I first perceived the little Planet making an Impression on the Sun’s Limb at 2h.52′. 41″; and he appeared wholly within at 53′. 58″. Ap.T. The Sun set before the Planet reached the Middle of his Course; and for a considerable Time before Sunset, it was so cloudy, that the Planet could not be discerned. So that I made no Observations of consequence except that of the Beginning, at which time the Sun was perfectly clear. This Transit compleats three Periods of 46 Years, since the first Observation of Gassendi8 at Paris in 1631.” With great Esteem, I am, Sir, Your most obedient Servant
Addressed: To / The Revd Mr Maskelyne / Astronomer Royal / at the Observatory / Greenwich
Endorsed: Winthrop’s on Comet Jan. 10.9
8. Pierre Gassendi or Gassend (1592–1655) was famous in his day as an opponent of Descartes and one of the most versatile scholars of Europe—linguist, theologian, philosopher, physician, astronomer. His work on Mercury was published as Mercurius, in Sole Visus et Venus Invisa (Paris, 1631).
9. The date in 1771 when the extract was read to the Royal Society; it was subsequently printed in Phil. Trans., LXI (1771), 51–2.