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East from Paris. These are the reasons which make me believe that the longitude of Selenginsk cannot be made less than 6h57’50″ from the meridian of our Royal Observatory. This being supposed, the observation of Mr. Rumowski compared with mine would give 10″1 for the horizontal parallax of the Sun in the month of June, and 10″26 for that parallax when the Sun is at the mean distance. 'Tis true, the same observation, compared with that of Mess. Mason and Dixon, would much reduce this parallax; and therefore it can be of no use to decide the question, unless we had some from Africa or from the adjacent seas.
I have one, which I have not dared yet to lay before our Academy; it appears to me a downright phenomenon. As it was made at the isle of France or Mauritius, it might pretend to the glory of deciding between Mess. Mason and Dixon and me; but it is such a one as can only at most determine how far the difference of sights or that of telescopes could extend or shorten the duration of the exit. I am acquainted with the observer, Mr. de Seligny, an officer in the service of the East India company; and I think I can answer for his capacity, talents, zeal and accuracy. He had no instrument but an eight foot telescope, and an excellent clock: this he regulated by altitudes of the Sun taken the 5th and 6th of June with Hadley's quadrant. That method is not strictly true, but our observer could do no better; and besides, whether the clock went too fast by a few seconds more or less, the difference cannot at all affect the duration observed by Mr. de Seligny. His clock on the 5th of June about 3 o'clock advanced 18” 12 upon
