{ "id": "2be86b96ec7d6ae22e440d02b7fbc42ae1a5d4b0", "text": "LX. Observations made at the Cape of Good Hope; by Mr. Charles Mason and Mr. Dixon; reduced to apparent Time by Mr. Mason. With an Appendix.\n\nRead April 22, 1762.\n\nTABLE for the object-glass micrometer, applied to the object-end of the tube of a reflecting telescope of two feet focal length, its focal length being 495.48 inches.\n\n| Inches | Angle | Decimals of an inch | Angle | Divisions of Vernier | Angle |\n|--------|-------|---------------------|-------|---------------------|-------|\n| 1 | 7 | 5.9 | 0 | 21.3 | 1 | 0.852 |\n| 2 | 14 | 11.9 | 0 | 42.6 | 2 | 1.7 |\n| 3 | 21 | 17.8 | 1 | 3.9 | 3 | 2.6 |\n| 4 | 28 | 23.8 | 1 | 25.2 | 4 | 3.4 |\n| 5 | 35 | 29.7 | 1 | 46.5 | 5 | 4.3 |\n| | | | 2 | 7.8 | 6 | 5.1 |\n| | | | 2 | 29.1 | 7 | 6.0 |\n| | | | 2 | 50.4 | 8 | 6.8 |\n| | | | 3 | 11.7 | 9 | 7.7 |\n| | | | 3 | 33.0 | 10 | 8.5 |\n| | | | 3 | 54.3 | 11 | 9.4 |\n| | | | 4 | 15.6 | 12 | 10.2 |\n| | | | 4 | 36.9 | 13 | 11.1 |\n| | | | 4 | 58.2 | 14 | 11.9 |\n| | | | 5 | 19.5 | 15 | 12.8 |\n| | | | 5 | 40.8 | 16 | 13.6 |\n| | | | 6 | 2.0 | 17 | 14.5 |\n| | | | 6 | 23.3 | 18 | 15.3 |\n| | | | 6 | 44.6 | 19 | 16.2 |\n| 1.00 | 7 | 5.9 | 20 | | 17.0 |\n| | | | 21 | | 17.9 |\n| | | | 22 | | 18.7 |\n| | | | 23 | | 19.6 |\n| | | | 24 | | 20.4 |\n| | | | 25 | | 21.3 |\n\nMEMO\nMEMORANDA.\n\nThe body of the observatory (erected at the Cape) was circular, the radius of which 6½ feet in the clear; the height of the circular wall 5½ feet; the roof conical, and moveable, (made of board) a lid in it of 3 feet breadth, to open, which was easily turned to any part of the heavens, as the whole top moved freely.\n\nThe clock was fixed against two pieces of timber (let near 4 feet into the ground) of 10 inches by 8; these pieces being joined together by pins of 1½ inch diameter.\n\nThe mean of Fahrenheit's thermometer, as it stood at 6 or 7 in the morning, noon, 1 or 2h after, and 7 or 8 in the evening.\n\nFrom 27th of May 1761 to June 10th 59.5, Extremes 53 to 65.\nFrom 10th of June to 20th - - - 59.2, Ditto - 50 to 67.\nFrom 20th of June to 30th - - - 57.9, Ditto - 51 to 68.\nFrom 1st of July to 15th - - - 56.3, Ditto - 50 to 65.\nFrom 15th of July to 30th - - - 54.3, Ditto - 47 to 60.\nFrom 1st of August to 15th - - - 56.9, Ditto - 48 to 66.\nFrom 15th of August to 30th - - - 56.0, Ditto - 48 to 68.\nFrom 1st of September to 15th - - - 57.4, Ditto - 50 to 69.\nFrom 15th of September to 26th - - - 54.8, Ditto - 49 to 64.\n\nAt 47 upon 18th July, in the morning, and 69 the 1st and 14th of September, in the afternoon. These were the greatest differences I saw.\n\nJune 6th, at the end of the transit, 55.\n\nNote. Those observations marked : are a little dubious.\nThose marked :: are very dubious.\nThe transit was observed with the power that magnified 120 time.\nThe eclipses of the satellites of Jupiter with the same power.\nThe adjustment of the nonius of\nthe micrometer, thus\n\nMean = 0.52 = 0.4 to be\nadded to the observed angle, it falling to the left hand of 0.\n\nObservations made at the Cape of Good Hope.\n\n1761.\nApril\nD 27th.\nMay\nP 2.\nD 4.\n\nArrived in Sable bay.\nCarried the instruments ashore.\nSet the clock going, the pendulum having not been altered since it came from London.\n\nThe quadrant being fixed, the plumb-line shewing it did not move.\n\nStars passed the wires per clock.\n\nThe stars returned to the same plane.\n\nProcyon. D 4th May.\nh 12 5½\nh 14 36\nh 17 7½\n\nProcyon. 8th May.\nh 2 9 48½\nh 12 18\nh 14 51\n\nFahrenheit's thermometer.\n\n| Going of the clock. | May |\n|---------------------|-----|\n| A.M. | P.M. |\n| 7th | 7th |\n| 10 | 65 |\n| 11 | 62 |\n| 13 | 56 |\n| 14 | 55 |\n| 15 | 55 |\n| 17 | 62 |\n| 18 | 58 |\n| 19 | 58 |\n| 20 | 60 |\n| 21 | 60 |\n| 22 | 60½ |\n| 23 | 58 |\n| 24 | 58 |\n| 25 | 58 |\n| 26 | 59 |\n\n1761.\n| Year | Stars passed the wires per clock. | The stars returned to the same plane. |\n|------|----------------------------------|-------------------------------------|\n| May | | |\n| | Caistor. 10th. | Caistor. 12th. |\n| | h' \" | h' \" |\n| | 2 55 28 | 2 49 30 + |\n| | Clouds. | 51 52 |\n| | 56 26½ | 52 32 |\n| | 57 6½ | |\n| | Pollux. 12th. | Pollux. 13th. |\n| | 3 2 27 | 3 0 11½ |\n| | 4 17 | 2 0 |\n| | 6 5½ | 3 49 |\n| | 7 15½ | 4 57½ |\n| | Pollux. 13th. | Pollux. 14th. |\n| | 3 0 11½ | 3 0 0 |\n| | Quadrant as before, and took the other wires, which clouds prevented, on the 12th. | 59 43 — |\n| | | 1 33 — |\n| | | 2 41½ |\n| | | 5 9 + |\n| | | 5 43 |\n| | Regulus. 16th. | Regulus. 17th. |\n| | 3 33 23½ | 3 31 6 |\n| | 34 42 | 32 25½ |\n| | 35 39 + | 33 21 |\n| | 37 56 | 35 38 — |\n| | Time per clock. | |\n| May | D 18d. | |\n| | h' \" | |\n| | 2 11 24 — | 55 34 28 Procyon apparent or observed zenith distances. |\n| | 19 52 | 56 59 0 |\n| | 25 26½ | 57 56 2 |\n| | Procyon. 18d. | Procy. 19d returned. |\n| | 2 34 31½ | 2 32 17 — |\n| | 35 1½ | 32 43½ |\n| | 37 26 | 35 11 |\n| | 37 52 — | 35 34½ |\n| | 2 38 42½ | 36 37 — |\n\n1761.\nTime per clock.\n\nMay 18th.\n\n5 24 o Cloudy.\n5 36 o The eclipse of the moon had been begun some time.\n\n6 36 5 Entrance into total darkness.\n7 58 20 Emergence - - - - - all very clear.\n9 6 30 The end of the eclipse.\n\nApparent time.\n\n10 53 28\n12 15 37\n13 23 42\n\nHitherto the clock stood on a lower floor, near to the place intended for the observatory; and the observatory being now finished, I put the clock into it, wound up the pendulum, and set it to nearly sidereal time.\n\nNo observations were made material to June 5th, it being cloudy near all the time; but the 5th, in the evening, it fortunately cleared up.\n\nJune 5th.\n\n11 39 21 + observed Antares. I set the quadrant to these even minutes, and then waited for the star passing of the wire.\n\n11 55 16 zenith distances.\n58 12 +\n12 11 44 Clouds.\n\nEqual altitudes.\n\nEast. West. Passed the meridian.\n\nTime per clock. Time per clock. Time per clock.\n\n12 19 45 20 8 5 1/2 16 16 16 1/2 Antares point 50 40 o\n\nClouds. Clouds.\n\n12 52 4 1/2 19 35 37 + 16 16 18 Ditto - - 44 o o\n\n56 59 37 4 1/2 16 16 17 1/2\n\n13 4 58 - 19 22 44 16 16 17 1/2 Ditto - - 41 20 o\n\n7 24 + 25 11 + 16 16 17 1/2\n\nClouds. 27 37 1/2\n\n13 16 13 + 19 11 29 - 16 16 18 Ditto - - 39 o o\n\n18 39 13 55 1/2 16 16 17 1/2\n\n21 7 - 16 22 : 16 16 17 1/2\n\n1761.\n| Equal altitudes. | Passed the meridian. |\n|-----------------|----------------------|\n| **East.** | **West.** |\n| Time per clock. | Time per clock. |\n| **h'** | **h'** |\n| June 5d | |\n| 16 9 39 | 23 5 54 |\n| 12 29 | 8 45 |\n| 15 20 | 11 34 |\n| 21 44 | 22 53 46 |\n| 24 37 | 56 37 |\n| 27 27 | 59 31 |\n| 16 33 16 + | 22 41 58 |\n| 36 15 | 44 59 |\n| 39 16 | 47 58 |\n| 19 40 37 | |\n| 19 40 37½ | |\n| 19 40 36½ | |\n| 19 40 37 | |\n| 19 40 37½ | |\n| 19 40 37 | |\n| 19 40 37 | |\n| 19 40 37 | |\n\nTransit of Venus.\n\n| Time per clock. | |\n|-----------------|--|\n| **h'** | |\n| June 5d | |\n| 0 12 0 | |\n| 0 35 0 | |\n| 0 48 40 | |\n| 0 52 0 | |\n| 1 0 0 | |\n\nParts of the micrometer.\n\n| Inches. | |\n|---------|--|\n| 1 18 7 | |\n| 3 90 5 | |\n| 27 18 | |\n| 3 95 5 | |\n| 30 4 | |\n| 3 95 15 | |\n| 33 5 | |\n| 4 0 0 | |\n| 35 15 | |\n| 4 0 4 | |\n| 37 40 | |\n| 4 0 17 ::| |\n| 39 0 | |\n| 4 40 23 - | |\n| 4 40 20½ | |\n| 44 0 | |\n| 4 40 21 + | |\n| 46 0 | |\n| 4 40 23½ | |\n\nThe ⊙’s farthest limb from ♀’s farthest limb. That is, the ⊙’s northern limb from ♀’s southern limb.\n\nDitto.\n\nDitto.\n\nDitto.\n\nDitto.\n\nDitto.\n\nThe ⊙’s diameter. By a mean of these four observations, the ⊙’s diameter is = 31′ 33″·3.\n\n1761.\n| Time per clock | Parts of the micrometer |\n|---------------|-------------------------|\n| June | |\n| 5 d. | |\n| 1761 | |\n| h ' \" | Inches |\n| 48 20 | 4 10 0 - |\n| 50 58 | 4 10 5 |\n| 55 30 | 0 10 19½ |\n| 57 0 | 0 10 20 - |\n| 59 0 | 0 10 19 + |\n| 2 2 23 | 4 19 19 - |\n| 3 55 | 4 19 22½ |\n| 5 45 | 4 20 5 + |\n\nThe O's farthest limb from Q's farthest limb, as before.\n\nDitto.\n\nVenus's diameter. By a mean of these three observations, the diameter of Venus is = 59''6.\n\nDitto.\n\nDitto.\n\nThe time of internal contact very clear\n\nDitto external\n\nApparent time,\n\n2 39 16\n\n56 50\n\n2 39 12\n\n56 48\n\nDitto, per Mr. Dixon.\n\nCloudy.\n\nSaw the O (but no satellite). Cloudy after, till night.\n\nN. B. The adjustment of the nonius of the micrometer as upon the 17th May.\n\nWhen I saw the planet first, its periphery, and that of the Sun's, were in a great tremour; but this vanished, as the Sun rose, and became well defined.\n\nFour minutes before the internal contact, the Sun's disk was entirely hid by a cloud, for about one minute.\n\nEqual altitudes.\n\n| Time per clock | Time per clock | Passed the mer. |\n|----------------|---------------|-----------------|\n| 12 51 39½ | 19 35 11 | 16 15 51½ |\n| 54 5½ | 37 35 : | 16 15 50½ |\n| 56 32½ | Clouds. | |\n| 13 4 32 | 19 22 17 | 16 15 51½ |\n| 6 59 | 24 44 | 16 15 51½ |\n| Clouds. | 27 10 + | 16 15 51 |\n\nAntares 44 0 0\n\nMr. Dixon.\n\nDitto 41 20 0\n\n1761.\n| Altitude. | Time per clock. |\n|----------|-----------------|\n| June 24 11 | 20 13 55 |\n\nThe second satellite of 24 immersed. Foggy air. The satellites appeared faint.\n\nApparent time: 14 51 24\n\nEqual altitudes.\n\n| Time per clock. | Time per clock. | Passed the meridian. |\n|-----------------|-----------------|----------------------|\n| 9 12 | 12 19 10 | 20 7 20½ |\n| | 21 37½ | 9 50 - |\n| | 24 5½ | 12 18 |\n| | 12 35 21 | 19 51 10 + |\n| | 37 48 | 53 37 |\n| | 40 16 | 56 6 - |\n| | 16 15 43 | |\n| | 16 15 43½ | |\n| | 16 15 44½ | |\n| | Antares | 50 40 0 |\n| | Ditto | - 47 20 0 |\n\nApparent time: 14 7 12\n\nThe * Virginis immersed behind the D. The occultation was at the D's northern limb, near the intersection of light and darkness.\n\n| Time per clock. | Time per clock. | Passed the meridian. |\n|-----------------|-----------------|----------------------|\n| 9 14 | 12 19 1 | 20 7 10 |\n| | 21 28½ | 9 38 + |\n| | 23 57 | 12 6½ |\n| | 16 15 33½ | |\n| | 16 15 33¾ | |\n| | 16 15 33¾ | |\n| | Antares | 50 40 { Mr. Dixon. |\n| | Ditto | - 47 20 d |\n\nZenith distance: 3 2 6\n\nFomalhaut upon the meridian. Plane of the quadrant facing the west.\n\n| Time per clock. | Time per clock. | Passed the meridian. |\n|-----------------|-----------------|----------------------|\n| 9 16 | 12 35 c½ | 19 50 50 |\n| | 37 28 - | 53 18 |\n| | 39 55½ | 55 44½ |\n| | 16 15 22¾ | |\n| | 16 15 23 | |\n| | Antares | - 47 20 0 |\n\nApparent time: 15 26 32\n\nThe third satellite of 24 emerged.\nAltitude.\n\nJune\n\n1761. 22 44 55 Zenith distance\n\nFomalhaut upon the meridian. Plane of the quadrant facing the east.\n\nBy the observations of Fomalhaut, it appears the quadrant does not shew the true angle, I new-adjusted it, &c. &c.\n\nEqual altitudes.\n\nTime per clock. Time per clock. Time per clock.\n\n16 53 49½ 22 18 44½ 19 39 28½\n\n57 0 - 21 56½ 13 39 28½\n\n17 0 12 25 7 -\n\n22 44 40 Zenith distance\n\nFomalhaut upon the meridian. Plane of the quadrant facing the east.\n\n23 18 35 The second satellite of ¼ immersed\n\nPassed the meridian.\n\n12 18 34 - 20 6 36½ 16 15 3½\n\n21 1½ 9 5½ 16 15 3½\n\n23 30 - 11 33 + 16 15 3½\n\nAntares - - 50 40 0\n\n14 50 24½ Zenith distance\n\nγ Scorpii upon the merid.\n\n15 44 45½ Ditto\n\n8 31 32\n\n16 15 8 - Ditto\n\n8 2 56\n\n17 7 40½ Ditto\n\n9 11 38\n\n18 40 50 - Ditto\n\n7 21 34\n\nσ Sagittarii.\n\nThe first satellite of ¼ immersed\n\nPassed the meridian.\n\n2 22 54 - 9 31 47½ 6 0 35½\n\n26 5 + 35 4½ 6 0 35½\n\n29 24 + 38 17 6 0 35½\n\nSun’s limbs. Mr. Dixon.\n\n1761.\n| Date | Altitude | Time per clock | Zenith distance | Notes |\n|------|----------|---------------|-----------------|-------|\n| June 21 | | | | Spica upon the meridian. |\n| | | | | Passed the meridian. |\n| | | | | α Aquilæ - 67° 40' 0\" |\n| | | | | Sun's limbs. |\n| | | | | Mr. Dixon. |\n| | | | | Ditto. |\n| | | | | Spica upon the meridian. |\n| | | | | Arcturus, ditto. |\n| | | | | Bootis. |\n| | | | | α Coronæ borealis. |\n| June 23 | | | | Spica upon the meridian. |\n| | | | | Arcturus, ditto. |\n| | | | | Bootis, ditto. |\n| | | | | Antares, ditto. |\n| | | | | The third satellite of 24 not immersed. |\n| | | | | Clouds. |\n| | | | | It was immersed. |\n| | | | | Zenith distance 3° 3' 30\" Fomalhaut upon the meridian. Quadrant west. |\n\nFrom this day to the 1st of July, cloudy, with strong winds and rain.\n\nD d d 2\n\n1761.\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| July 1 | Time per clock | Time per clock |\n| 1761 | 12 58 24½ | 19 25 46 : 16 14 32 : Antares - 42 20 0 |\n| | 13 0 51 + 28 14 : 16 14 32½ | |\n| | 3 18 Clouds. | |\n| | 14 29½ | 19 0 0 |\n| | 16 56 | 12 8½ |\n| | 19 23 + 14 35 | 16 14 32½ |\n| | | 16 14 32½ |\n| | 17 17 23 Zenith distance | 2 58 6 S. |\n| | | |\n| 24 2 | Ditto - - | 3 40 48 S. |\n| | 17 17 0 | Ditto - - 2 58 8 S. |\n| | 18 5 0 | Ditto - - 4 1 45 N. |\n| | 22 44 0 | Ditto - - 3 3 8 N. |\n| 2 3 | Ditto - - | 3 40 52 S. |\n| | 17 0 | Ditto - - 2 58 0 S. |\n| | 18 0 0 | Ditto - - 4 1 42 N. |\n| | 22 44 0 | Ditto - - 3 3 4 N. |\n| | | |\n| Equal altitudes. | Passed the mer. |\n| 8 7 | 13 14 23 | 19 9 33 : 16 14 24½ : Antares point 39 0 0 |\n| | 16 49 | 12 0 + 16 14 24½ |\n| | 19 16 + 14 26½ | 16 14 24½ |\n| | | |\n| | 16 35 24 Zenith distance | 3 41 32 : S. |\n| | 17 17 0 | Ditto - - 2 58 40 S. |\n| | 18 5 0 | Ditto - - 4 1 0 N. |\n| 8 8 | Ditto - - | 3 41 34 S. |\n| | 17 17 0 | Ditto - - 2 58 48 S. |\n| | 18 5 0 | Ditto - - 4 1 8 N. |\n\nPlane of the quadrant facing the west.\n\nPlane of the quadrant facing the east.\n\n1761.\n### Equal altitudes\n\n| Time per clock | Passed the meridian |\n|----------------|---------------------|\n| **July** | |\n| 24 9 | |\n| 13 14 13 | 16 14 14½ |\n| 16 39 | 16 14 14 |\n| 19 6½ | 16 14 14½ |\n| 16 35 8 | Zenith distance |\n| 17 17 0 | Ditto |\n| 18 5 0 | Ditto |\n| 22 44 0 | Ditto |\n\n### Equal altitudes\n\n| Time per clock | Passed the meridian |\n|----------------|---------------------|\n| **O 12** | |\n| 13 31 39 | 16 13 59 |\n| 34 5 | 16 13 59 |\n| 36 33 | 16 13 59½ |\n| 15 50 45 + | Zenith distance |\n| 14 47 22 | |\n\n### Equal altitudes\n\n| Time per clock | Passed the meridian |\n|----------------|---------------------|\n| **§ 15** | |\n| 13 0 0 | 16 13 43½ |\n| 33 49 | 16 13 43½ |\n| 36 17 - | |\n\n### Nonius of the micrometer\n\n| Inches | Moon's southern limb from σ Sagittarii |\n|----------------|----------------------------------------|\n| 17 45 18 | Ditto |\n| 52 55 | Ditto |\n| 57 58 | Ditto |\n| 18 2 15 | Ditto |\n| 7 45 | Ditto |\n\nσ Sagittarii made a near appulse to the D’s limb. The eye could not discover by the telescope, that it altered its distance, till about 17h 35'.\n\nA little hazy.\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| July 17 | 16 0 22 + 23 9 47½ | 19 37 53½ |\n| | 3 10 12 36 | 19 37 53 |\n| | 5 59½ 15 24 | 19 37 53 |\n\nThe second satellite of 24 immersed\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Aug. 21 | 5 14 59½ 10 41 53 - 8 2 5 | Sun's limb - 66 30 0 |\n| | 18 38 - 45 32 + 8 2 5 |\n| | 22 17 + 49 11 - 8 2 5½ |\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Aug. 29 | 15 20 19½ 23 48 32 + 19 37 5½ | α Aquilae - 73 20 0 |\n| | 22 59 51 11½ 19 37 5½ |\n| | 25 38½ 53 51 : |\n\nThe third satellite of 24 immersed\n\nDitto emerged\n\nThe first satellite immersed\n\nDitto, per Mr. Dixon.\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Aug. 7 | 15 30 13½ 23 37 18 - 19 36 28 | α Aquilae - 71 20 0 |\n| | 32 54 - 39 59 + 19 36 26½ |\n| | 35 36 42 40½ 19 36 27 |\n\nThe 2d satellite of 24 immersed. A little hazy\n\nThe first immersed. Clear\n\n| Date | Zenith distance | Scorpii upon the meridian. |\n|------|-----------------|-----------------------------|\n| Aug. 8 | 15 48 54 - 14 47 40 | Antares ditto. |\n| | 16 12 0 | |\n| | Ditto | |\n\n| Date | Zenith distance | Ophiuchi upon the meridian. |\n|------|-----------------|-----------------------------|\n| Aug. 9 | 17 4 45 | Sagittarii ditto. |\n| | 18 3 0 | |\n| | Ditto | |\n| | 9 11 42 | |\n| | 4 1 28 | |\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Aug. 10 | Time per clock | Time per clock |\n| h | h | h |\n| 15 19 28 + 23 47 37 | 19 36 12 | α Aquilae - 73 20 0 |\n| 22 7 - 50 17 + | 19 36 12 | |\n| 24 47 - 52 55½ | 19 36 11¾ | |\n| 16 3 50 Zenith distance | 8 55 48 | ρ Scorpii upon the meridian |\n| 11 0 Ditto | 8 2 54 | Antares ditto |\n| 0 53 45 The fourth satellite of ¼ immersed | - - - - 15 32 57 |\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Sep. 12 | Time per clock | Time per clock |\n| h | h | h |\n| 15 19 18½ | 23 47 28 | 19 36 2¾ | α Aquilae - 73 20 0 |\n| 21 58 : 50 8 - | 19 36 3 : | |\n| 24 37½ | 52 47 - | 19 36 2¾ | |\n| 14. 23 36 11 The first satellite of ¼ immersed | - - - - 14 0 50 |\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Sep. 20 | Time per clock | Time per clock |\n| h | h | h |\n| I put the clock forward. |\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Sep. 21 | Time per clock | Time per clock |\n| h | h | h |\n| 16 39 26½ | 22 36 0½ | 19 40 43½ | α Aquilae - 59 40 0 |\n| 42 22 | 39 4¾ | 19 40 43¾ | |\n| 45 26 - | 42 6½ | 19 40 43½ | |\n| 2 2 35 The first satellite of ¼ immersed | - - - - 15 56 2 |\n| 2 30 Ditto, per Mr. Dixon. |\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Oct. 23 | Time per clock | Time per clock |\n| h | h | h |\n| 16 51 19 : | 22 23 34 - | 19 40 35¾ | α Aquilae - 57 40 0 |\n| 54 27 - | 26 44½ | 19 40 35¾ | |\n| 57 37½ | 29 52 + | 19 40 35½ | |\n| 20 38 8 The first satellite of ¼ immersed | - - - - 10 25 10 |\n| 38 2 Ditto, per Mr. Dixon. |\n\n1761.\n| Date | Equal altitudes | Passed the meridian |\n|------|----------------|---------------------|\n| Aug. 27 | Time per clock | Time per clock |\n| h | \" | h | \" |\n| 16 50 58 + | 22 23 14 - | 19 40 15 |\n| 54 6 - | 26 24 | 19 40 15 |\n| 57 16 + | 29 32 + | 19 40 15 + |\n| α Aquilae | 57 40 0 |\n\nApparent time.\n\nThe fourth satellite of ¼ immersed - - - 9 53 32\n\nDitto, per Mr. Dixon.\n\nThe fourth satellite emerged - - - - 12 49 0\n\n| Date | Equal altitudes | Passed the meridian |\n|------|----------------|---------------------|\n| Oct. 30 | Time per clock | Time per clock |\n| h | \" | h | \" |\n| 16 50 40½ | 22 22 58 - | 19 39 58½ |\n| 53 49 - | 26 8 - | 19 39 58½ |\n| 56 59 - | 29 16 | 19 39 58½ |\n| α Aquilae | 57 40 0 |\n\nApparent time.\n\nThe first satellite of ¼ immersed - - - 12 21 32\n\nSept. 8 1.\n\nThe 2d satellite of ¼ immersed. Flying clouds 9 2 20\n\n| Date | Equal altitudes | Passed the meridian |\n|------|----------------|---------------------|\n| 24 3. | Time per clock | Time per clock |\n| h | \" | h | \" |\n| 17 22 52½ | 21 49 16 | 19 39 42½ |\n| 26 24 + | 52 52 | 19 39 38 |\n| 30 8½ :: | 56 25½ | 19 39 39 |\n| α Aquilae | 52 40 0 |\n\nApparent time.\n\nA small * immersed behind the D 7 1 52\n\nAnother very small * ditto - - 7 34 24\n\nThe 3d satellite of ¼ immersed - 8 36 33\n\nDitto.\n\n| Date | Equal altitudes | Passed the meridian |\n|------|----------------|---------------------|\n| 9 4. | Time per clock | Time per clock |\n| h | \" | h | \" |\n| 17 Clouds. | 21 49 10 | 19 39 32½ |\n| 26 18½ | 52 47½ | 19 39 33 |\n| 29 55½ | 56 19 + | α Aquilae | 52 49 0 |\n\nApparent time.\n\n25 Librae immersed behind the D - - - 7 6 53½\n\nDitto. emerged from the D.\n\n1761.\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Sept. 6 | 17 22 32 - 21 48 56½ | 19 39 19½ |\n| | 26 5½ 52 32½ | 19 39 19 |\n| | 29 42½ 56 6 - | 19 39 19 |\n| Sept. 7 | 18 13 24 Zenith distance | 8 23 46 |\n| Sept. 8 | 22 52 15 The second satellite of 24 immersed | Apparent time: 11 42 20 |\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Sept. 22 | 19 0 29 + 2 20 47½ | 22 43 8¾ |\n| | 3 0 23 18 - | 22 43 9 |\n| | 5 30 - Clouds. | |\n| | 19 37 48 Zenith distance | 42 10 42 |\n| | 22 43 16½ Ditto | 3 3 16 |\n| Sept. 24 | 21 27 14 The first satellite of 24 emerged | Apparent time: 9 21 35 |\n| | 27 15 Ditto, per Mr. Dixon. | |\n\n| Date | Equal altitudes | Passed the meridian |\n|------|-----------------|---------------------|\n| Sept. 27 | 19 29 38½ | 1 51 1 |\n| | 32 7 + 53 29½ | 22 42 48¾ |\n| | 34 36 - 55 57½ | 22 42 48¾ |\n| Sept. 28 | Packed up the instruments. | |\n| Oct. 29 | Put them on board the Mercury, Capt. Harrold. | |\n| Oct. 3 | Sailed for St. Helena. | |\n\nCharles Mason.\nThe instruments made use of, in these observations, were,\nTwo reflecting telescopes, each two feet focal length, and magnifying 120 times,\nmade by Mr. Short.\nA quadrant of one foot radius, made by Mr. Bird, and the property of the Earl\nof Macclesfield.\nAn astronomical clock, made by Mr. Ellicott.\n\nAPPENDIX.\n\nEclipses of Jupiter's satellites, observed at the Royal Observatory\nat Greenwich, with a reflector of two feet focus, magnifying\n95 times.\n\n| Apparent time | Immersion of the third satellite. |\n|---------------|----------------------------------|\n| June 23. | 15 10 24 |\n| July 20. | 15 54 28 - - - of the second. |\n| 22. | 12 35 29 - - - of the first. |\n| Aug. 7. | 10 51 52 - - - of the first. |\n| Sept. 8. | 10 28 5 - - - of the second. |\n| 10. | 11 27 6 - - - of the third. |\n| 15. | 13 6 36 - - - of the second. |\n| 24. | 8 7 46 Emersion of the first. |\n\nEclipses of Jupiter's satellites, observed at Mr. Short's house in\nSurry-street in the Strand, London, by Dr. Bevis, with a re-\nflecting telescope of four feet focal length, magnifying 140 times,\nand by Mr. Short, with a reflector of two feet focus, magni-\nfying 95 times.\n\n| Apparent time | Immersion of the first satellite, by Dr. Bevis. |\n|---------------|-------------------------------------------------|\n| July 22. | 12 35 13 |\n| | 12 34 58 |\n| Aug. 7. | 10 29 43 - - - of the 2d satellite, by Dr. Bevis.|\n| | 10 29 31 |\n| 27. | 8 41 16 - - - of the 4th satellite, by Dr. Bevis.|\n| | 8 37 4 |\n| 30. | 11 7 31 - - - of the first satellite, by Mr. Short.|\n| Sept. 8. | 10 29 3 - - - of the 2d satellite, by Dr. Bevis.|\n| | 10 28 35 |\n\nN. B. Mr. Short's house is 26' ¼ of time to the west of the Royal Observatory.\n\nLXI. 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With an Appendix", "authors": "Charles Mason, Mr. Dixon", "year": 1761, "volume": "52", "journal": "Philosophical Transactions (1683-1775)", "page_count": 18, "jstor_url": "https://www.jstor.org/stable/105637" } }