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  "text": "XL. A Letter from M. Pingré, of the Royal Academy of Sciences at Paris, to the Rev. Mr. Maskelyne, Astronomer Royal, F.R.S.\n\nSIR,\n\nShould long ere now have sent you my American observations, could I have presumed you would have so far honoured them as to receive them with pleasure. With your permission, Sir, I shall in future direct to you, and at present send you my several observations in chronological order.\n\nAt Fort Royal in Martinico, on the new bastion, emersion of the first satellite, the 12th of May, 1769, at $16^h\\ 28'\\ 23''$ apparent time, serene sky; the satellite very near $4$, with an achromatic telescope of five feet, having only two glasses for the object glass, and two plano-convex eye-glasses; the magnifying power about 140 times, made by M. l'Estang at Paris.\n\nThe 13th, emersion of the third satellite, at $10^h\\ 01'\\ 00''$ apparent time, very serene, the same telescope; at $10^h\\ 01'\\ 22''$ by M. de Fleurieu, captain of the king's frigate Isis, with an achromatic telescope $2\\ \\frac{1}{2}$ feet long, made at London by Mr. Dollond, a two-glass object-glass, and two plano-convex eye-glasses, the magnifying less than the former, but much clearer.\n\nThe 14th, emersion of the first satellite at $10^h\\ 57'\\ 14''$ apparent time, M. de Fleurieu with the same telescope. I had been much fatigued, and quitted my post.\n\nVol. LX.\nThe same day, by several meridian altitudes of stars taken some to the North, some to the South, I found the latitude $14^\\circ 35' 49\\frac{1}{2}''$. M. de Fleurieu made it $14^\\circ 35' 54\\frac{1}{2}''$.\n\nThe 15th the rains began.\n\nAt Cape Francis in the island of St. Domingo.\n\nJune 3 we first perceived Venus entering on the Sun's disk.\n\nat $2 \\ 26 \\ 14\\frac{1}{2}$ apparent time, with Dollond's $2\\frac{1}{2}$ feet telescope. M. de Fleurieu.\n\n$2 \\ 26 \\ 16\\frac{1}{2}$ apparent time, with an achromatic of 3 feet, by l'Eftang. M. la Filiere.\n\n$2 \\ 26 \\ 20\\frac{1}{2}$ apparent time, with a common telescope of 2 feet, only 2 lenses. M. des Saqui Tourés.\n\n$2 \\ 26 \\ 12\\frac{1}{2}$ apparent time, with a five-feet achromatic. Myself.\n\nAfter having given our eyes some respite, we returned to the telescopes; and M. de Fleurieu perceived a luminous little circle all round Venus, not yet entered more than about one third of her diameter. This luminous thread made, to all appearance, a perfect circle with the part of the circumference of Venus already advanced on the solar disk. I likewise observed the same phenomenon, but a good while after. M. de Fleurieu.\n\nVenus\nVenus appeared totally entered\n\nat 2 44 45 M. de Fleurieu.\n        44 41 M. le Chev. de la Filiere.\n        44 50 M. Saqui des Tourés.\n        44 44 Myself.\n\nDuring both these observations, every thing was quiet and still, not a word uttered, to intimate that any one had observed the contact.\n\nStormy weather almost every night hindered us from observing the eclipses of the satellites. However, the 10th of June proving a clear night, afforded us an opportunity of determining the latitude of our observatory; which by meridian altitudes of several stars, both to the North and South, I determined to be $19^\\circ 47' 03''$. The new church of the Cape, situated nearly in the middle of the town, may be about $20''$ or $25''$ more Southward than our observatory, whence its latitude $19^\\circ 46' 40''$ North.\n\nAs to the longitude, we had no other way but to take with our quadrant some altitudes of the moon's lower limb:\n\n| Alt. | Times by clock. | Apparent times. |\n|------|-----------------|-----------------|\n| 37   | 9 12 53         | 9 8 30 54       |\n| 36   | 17 25           | 13 2 43         |\n| 35   | 21 55           | 17 32 31        |\n| 34   | 26 21           | 21 58 20        |\n| 33   | 30 48,5         | 26 25 58        |\n\nThese\nThese altitudes taken with a quadrant of two French feet radius, $1'6''$ must be added to each, to correct the error of the quadrant.\n\nM. de Fleurieu's were:\n\n| Alt. | Times by clock | Apparent times |\n|------|----------------|----------------|\n|      | h  '  ''       | h  '  ''       |\n| 34   | 45             | 9 22 28,5      | 9 18 05,80 |\n| 34   | 15             | 24 41,5        | 20 18,74  |\n| 33   | 45             | 26 56          | 22 33,19  |\n| 32   | 45             | 31 23,5        | 27 0,57   |\n| 32   | 15             | 33 36,5        | 29 13,51  |\n| 31   | 45             | 36 51,5        | 31 28,46  |\n\nThese altitudes were taken with an English quadrant of M. Sisson's make, 16 inches radius. $8'34''$ are to be added to each altitude to correct the error of the instrument, and for the semi-diameter of the wire.\n\nOn computing these altitudes by M. Clairaut's tables, corrected nearly by observations made at Paris the 30th of May and the 1st of June 1751, I find the longitude of Cape Francois, West of the meridian of Paris, by my own altitudes, $4^h58'8''$, and by those of M. de Fleurieu $4^h58'20''$.\n\nI return to Venus: the time which we have noted for the total entry is that when we perceived a very slender thread of light between the limbs of the $\\odot$ and $\\oplus$. I judged that the limbs were in contact, but a few seconds before that instant. At the exit of $\\oplus$ in 1761, the limbs, being not yet in contact, and even sensibly distant asunder, I saw as it were a dark spot detach itself from Venus, and gain the\nthe limb of the Sun; at which instant I estimated\nthe internal contact. Many have this year seen the\nsame phenomenon at the total entry of Venus. I was\nin expectation of it; neither I or my associates per-\nceived any such thing. In 1761 the Sun's limbs were\nmost exquisitely well defined; in 1769 they undulated,\nespecially at the beginning of the entry; at the total\nentry the undulation was considerably less, and not-\nwithstanding this undulation I believe our observation\na good one. On comparing the duration of the\ntransit observed at the Prince of Wales's Fort, with\nthat of Father Hell, at Wardhus, I find, on a first\ncalculus, which I believe at least nearly exact, that the\nSun's parallax is $9''$.11.\n\nAugust 16, at St. Croix in Teneriffe, the first\nsatellite emerged at $9^h\\ 16'\\ 5''$, apparent time.\n\nI am, &c.\n\nParis, March 10, 1770.\n\nPingré.",
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    "identifier": "jstor-105912",
    "title": "A Letter from M. Pingre, of the Royal Academy of Sciences at Paris, to the Rev. Mr. Maskelyne, Astronomer Royal, F. R. S.",
    "authors": "M. Pingre",
    "year": 1770,
    "volume": "60",
    "journal": "Philosophical Transactions (1683-1775)",
    "page_count": 6,
    "jstor_url": "https://www.jstor.org/stable/105912"
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