Benjamin Franklin letter to Nevil Maskelyne, 12 February 1770

Craven Street, [London], February 12, 1770.

DEAR SIR,

I have just received a letter from Mr. Winthrop, dated December 7th, containing the following account, viz. "On Thursday, the Qth 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 2 h 52' 41" ; and he appeared wholly within at 53' 58" apparent time. 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 completes three periods of forty-six years, since the first observation of Gassendi at Paris, in 1631."

I am, Sir, with great esteem,

Your most obedient servant,

B. FRANKLIN.