[ 159 ]
the apparent; the 6th at the same hour it got only 9”. The observer was obstructed by the clouds till near the instant of the exit of Venus. This is his observation of the exit; the times are those of his clock, from which 2′10″ are to be substracted to have the apparent time. At 0h28′38″ the preceding limb of Venus appeared to touch exactly that of the Sun; at 0h22′00″ one quarter of her diameter was got out; at 0h25′10″ Mr. Seligny judged her to be half got out; at 0h28′06″ the three quarters of her diameter were emerged, and 0h31′12″ the exit was total and instantaneous. These observations follow one another very well, and they have been made by a man whom I know to be very skilful; but how the exit of Venus could appear to him to have taken up but 12′34″ I must leave to persons skilled in natural philosophy to account for. The observation of the first contact, or of the internal contact of the limbs, would give you more than 12″ for the parallax; that of the last would reduce it to eight; by a medium, the parallax would exceed 10″.
You will undoubtedly have observed a pretty remarkable difference between my observations of Venus, as I had the honour to send them to you from Lisbon March 6, 1762, and the same observations as I have related them in my memoir. I imagined I had sent the correction to some one of the members of your celebrated Society. When I made the reduction of these observations at Rodriguez, I found myself under disagreeable circumstances; and it was probably my uneasiness at that time that occasioned a want of due attention, which I was the longer in finding out as I could not easily sus-
