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

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. Read April 22, 1762. TABLE 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. | Inches | Angle | Decimals of an inch | Angle | Divisions of Vernier | Angle | |--------|-------|---------------------|-------|---------------------|-------| | 1 | 7 | 5.9 | 0 | 21.3 | 1 | 0.852 | | 2 | 14 | 11.9 | 0 | 42.6 | 2 | 1.7 | | 3 | 21 | 17.8 | 1 | 3.9 | 3 | 2.6 | | 4 | 28 | 23.8 | 1 | 25.2 | 4 | 3.4 | | 5 | 35 | 29.7 | 1 | 46.5 | 5 | 4.3 | | | | | 2 | 7.8 | 6 | 5.1 | | | | | 2 | 29.1 | 7 | 6.0 | | | | | 2 | 50.4 | 8 | 6.8 | | | | | 3 | 11.7 | 9 | 7.7 | | | | | 3 | 33.0 | 10 | 8.5 | | | | | 3 | 54.3 | 11 | 9.4 | | | | | 4 | 15.6 | 12 | 10.2 | | | | | 4 | 36.9 | 13 | 11.1 | | | | | 4 | 58.2 | 14 | 11.9 | | | | | 5 | 19.5 | 15 | 12.8 | | | | | 5 | 40.8 | 16 | 13.6 | | | | | 6 | 2.0 | 17 | 14.5 | | | | | 6 | 23.3 | 18 | 15.3 | | | | | 6 | 44.6 | 19 | 16.2 | | 1.00 | 7 | 5.9 | 20 | | 17.0 | | | | | 21 | | 17.9 | | | | | 22 | | 18.7 | | | | | 23 | | 19.6 | | | | | 24 | | 20.4 | | | | | 25 | | 21.3 | MEMO MEMORANDA. The 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. The 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. The 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. From 27th of May 1761 to June 10th 59.5, Extremes 53 to 65. From 10th of June to 20th - - - 59.2, Ditto - 50 to 67. From 20th of June to 30th - - - 57.9, Ditto - 51 to 68. From 1st of July to 15th - - - 56.3, Ditto - 50 to 65. From 15th of July to 30th - - - 54.3, Ditto - 47 to 60. From 1st of August to 15th - - - 56.9, Ditto - 48 to 66. From 15th of August to 30th - - - 56.0, Ditto - 48 to 68. From 1st of September to 15th - - - 57.4, Ditto - 50 to 69. From 15th of September to 26th - - - 54.8, Ditto - 49 to 64. At 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. June 6th, at the end of the transit, 55. Note. Those observations marked : are a little dubious. Those marked :: are very dubious. The transit was observed with the power that magnified 120 time. The eclipses of the satellites of Jupiter with the same power. The adjustment of the nonius of the micrometer, thus Mean = 0.52 = 0.4 to be added to the observed angle, it falling to the left hand of 0. Observations made at the Cape of Good Hope. 1761. April D 27th. May P 2. D 4. Arrived in Sable bay. Carried the instruments ashore. Set the clock going, the pendulum having not been altered since it came from London. The quadrant being fixed, the plumb-line shewing it did not move. Stars passed the wires per clock. The stars returned to the same plane. Procyon. D 4th May. h 12 5½ h 14 36 h 17 7½ Procyon. 8th May. h 2 9 48½ h 12 18 h 14 51 Fahrenheit's thermometer. | Going of the clock. | May | |---------------------|-----| | A.M. | P.M. | | 7th | 7th | | 10 | 65 | | 11 | 62 | | 13 | 56 | | 14 | 55 | | 15 | 55 | | 17 | 62 | | 18 | 58 | | 19 | 58 | | 20 | 60 | | 21 | 60 | | 22 | 60½ | | 23 | 58 | | 24 | 58 | | 25 | 58 | | 26 | 59 | 1761. | Year | Stars passed the wires per clock. | The stars returned to the same plane. | |------|----------------------------------|-------------------------------------| | May | | | | | Caistor. 10th. | Caistor. 12th. | | | h' " | h' " | | | 2 55 28 | 2 49 30 + | | | Clouds. | 51 52 | | | 56 26½ | 52 32 | | | 57 6½ | | | | Pollux. 12th. | Pollux. 13th. | | | 3 2 27 | 3 0 11½ | | | 4 17 | 2 0 | | | 6 5½ | 3 49 | | | 7 15½ | 4 57½ | | | Pollux. 13th. | Pollux. 14th. | | | 3 0 11½ | 3 0 0 | | | Quadrant as before, and took the other wires, which clouds prevented, on the 12th. | 59 43 — | | | | 1 33 — | | | | 2 41½ | | | | 5 9 + | | | | 5 43 | | | Regulus. 16th. | Regulus. 17th. | | | 3 33 23½ | 3 31 6 | | | 34 42 | 32 25½ | | | 35 39 + | 33 21 | | | 37 56 | 35 38 — | | | Time per clock. | | | May | D 18d. | | | | h' " | | | | 2 11 24 — | 55 34 28 Procyon apparent or observed zenith distances. | | | 19 52 | 56 59 0 | | | 25 26½ | 57 56 2 | | | Procyon. 18d. | Procy. 19d returned. | | | 2 34 31½ | 2 32 17 — | | | 35 1½ | 32 43½ | | | 37 26 | 35 11 | | | 37 52 — | 35 34½ | | | 2 38 42½ | 36 37 — | 1761. Time per clock. May 18th. 5 24 o Cloudy. 5 36 o The eclipse of the moon had been begun some time. 6 36 5 Entrance into total darkness. 7 58 20 Emergence - - - - - all very clear. 9 6 30 The end of the eclipse. Apparent time. 10 53 28 12 15 37 13 23 42 Hitherto 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. No observations were made material to June 5th, it being cloudy near all the time; but the 5th, in the evening, it fortunately cleared up. June 5th. 11 39 21 + observed Antares. I set the quadrant to these even minutes, and then waited for the star passing of the wire. 11 55 16 zenith distances. 58 12 + 12 11 44 Clouds. Equal altitudes. East. West. Passed the meridian. Time per clock. Time per clock. Time per clock. 12 19 45 20 8 5 1/2 16 16 16 1/2 Antares point 50 40 o Clouds. Clouds. 12 52 4 1/2 19 35 37 + 16 16 18 Ditto - - 44 o o 56 59 37 4 1/2 16 16 17 1/2 13 4 58 - 19 22 44 16 16 17 1/2 Ditto - - 41 20 o 7 24 + 25 11 + 16 16 17 1/2 Clouds. 27 37 1/2 13 16 13 + 19 11 29 - 16 16 18 Ditto - - 39 o o 18 39 13 55 1/2 16 16 17 1/2 21 7 - 16 22 : 16 16 17 1/2 1761. | Equal altitudes. | Passed the meridian. | |-----------------|----------------------| | **East.** | **West.** | | Time per clock. | Time per clock. | | **h'** | **h'** | | June 5^d | | | 16 9 39 | 23 5 54 | | 12 29 | 8 45 | | 15 20 | 11 34 | | 21 44 | 22 53 46 | | 24 37 | 56 37 | | 27 27 | 59 31 | | 16 33 16 + | 22 41 58 | | 36 15 | 44 59 | | 39 16 | 47 58 | | 19 40 37 | | | 19 40 37½ | | | 19 40 36½ | | | 19 40 37 | | | 19 40 37½ | | | 19 40 37 | | | 19 40 37 | | | 19 40 37 | | Transit of Venus. | Time per clock. | | |-----------------|--| | **h'** | | | June 5^d | | | 0 12 0 | | | 0 35 0 | | | 0 48 40 | | | 0 52 0 | | | 1 0 0 | | Parts of the micrometer. | Inches. | | |---------|--| | 1 18 7 | | | 3 90 5 | | | 27 18 | | | 3 95 5 | | | 30 4 | | | 3 95 15 | | | 33 5 | | | 4 0 0 | | | 35 15 | | | 4 0 4 | | | 37 40 | | | 4 0 17 ::| | | 39 0 | | | 4 40 23 - | | | 4 40 20½ | | | 44 0 | | | 4 40 21 + | | | 46 0 | | | 4 40 23½ | | The ⊙’s farthest limb from ♀’s farthest limb. That is, the ⊙’s northern limb from ♀’s southern limb. Ditto. Ditto. Ditto. Ditto. Ditto. The ⊙’s diameter. By a mean of these four observations, the ⊙’s diameter is = 31′ 33″·3. 1761. | Time per clock | Parts of the micrometer | |---------------|-------------------------| | June | | | 5 d. | | | 1761 | | | h ' " | Inches | | 48 20 | 4 10 0 - | | 50 58 | 4 10 5 | | 55 30 | 0 10 19½ | | 57 0 | 0 10 20 - | | 59 0 | 0 10 19 + | | 2 2 23 | 4 19 19 - | | 3 55 | 4 19 22½ | | 5 45 | 4 20 5 + | The O's farthest limb from Q's farthest limb, as before. Ditto. Venus's diameter. By a mean of these three observations, the diameter of Venus is = 59''6. Ditto. Ditto. The time of internal contact very clear Ditto external Apparent time, 2 39 16 56 50 2 39 12 56 48 Ditto, per Mr. Dixon. Cloudy. Saw the O (but no satellite). Cloudy after, till night. N. B. The adjustment of the nonius of the micrometer as upon the 17th May. When 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. Four minutes before the internal contact, the Sun's disk was entirely hid by a cloud, for about one minute. Equal altitudes. | Time per clock | Time per clock | Passed the mer. | |----------------|---------------|-----------------| | 12 51 39½ | 19 35 11 | 16 15 51½ | | 54 5½ | 37 35 : | 16 15 50½ | | 56 32½ | Clouds. | | | 13 4 32 | 19 22 17 | 16 15 51½ | | 6 59 | 24 44 | 16 15 51½ | | Clouds. | 27 10 + | 16 15 51 | Antares 44 0 0 Mr. Dixon. Ditto 41 20 0 1761. | Altitude. | Time per clock. | |----------|-----------------| | June 24 11 | 20 13 55 | The second satellite of 24 immersed. Foggy air. The satellites appeared faint. Apparent time: 14 51 24 Equal altitudes. | Time per clock. | Time per clock. | Passed the meridian. | |-----------------|-----------------|----------------------| | 9 12 | 12 19 10 | 20 7 20½ | | | 21 37½ | 9 50 - | | | 24 5½ | 12 18 | | | 12 35 21 | 19 51 10 + | | | 37 48 | 53 37 | | | 40 16 | 56 6 - | | | 16 15 43 | | | | 16 15 43½ | | | | 16 15 44½ | | | | Antares | 50 40 0 | | | Ditto | - 47 20 0 | Apparent time: 14 7 12 The * Virginis immersed behind the D. The occultation was at the D's northern limb, near the intersection of light and darkness. | Time per clock. | Time per clock. | Passed the meridian. | |-----------------|-----------------|----------------------| | 9 14 | 12 19 1 | 20 7 10 | | | 21 28½ | 9 38 + | | | 23 57 | 12 6½ | | | 16 15 33½ | | | | 16 15 33¾ | | | | 16 15 33¾ | | | | Antares | 50 40 { Mr. Dixon. | | | Ditto | - 47 20 d | Zenith distance: 3 2 6 Fomalhaut upon the meridian. Plane of the quadrant facing the west. | Time per clock. | Time per clock. | Passed the meridian. | |-----------------|-----------------|----------------------| | 9 16 | 12 35 c½ | 19 50 50 | | | 37 28 - | 53 18 | | | 39 55½ | 55 44½ | | | 16 15 22¾ | | | | 16 15 23 | | | | Antares | - 47 20 0 | Apparent time: 15 26 32 The third satellite of 24 emerged. Altitude. June 1761. 22 44 55 Zenith distance Fomalhaut upon the meridian. Plane of the quadrant facing the east. By the observations of Fomalhaut, it appears the quadrant does not shew the true angle, I new-adjusted it, &c. &c. Equal altitudes. Time per clock. Time per clock. Time per clock. 16 53 49½ 22 18 44½ 19 39 28½ 57 0 - 21 56½ 13 39 28½ 17 0 12 25 7 - 22 44 40 Zenith distance Fomalhaut upon the meridian. Plane of the quadrant facing the east. 23 18 35 The second satellite of ¼ immersed Passed the meridian. 12 18 34 - 20 6 36½ 16 15 3½ 21 1½ 9 5½ 16 15 3½ 23 30 - 11 33 + 16 15 3½ Antares - - 50 40 0 14 50 24½ Zenith distance γ Scorpii upon the merid. 15 44 45½ Ditto 8 31 32 16 15 8 - Ditto 8 2 56 17 7 40½ Ditto 9 11 38 18 40 50 - Ditto 7 21 34 σ Sagittarii. The first satellite of ¼ immersed Passed the meridian. 2 22 54 - 9 31 47½ 6 0 35½ 26 5 + 35 4½ 6 0 35½ 29 24 + 38 17 6 0 35½ Sun’s limbs. Mr. Dixon. 1761. | Date | Altitude | Time per clock | Zenith distance | Notes | |------|----------|---------------|-----------------|-------| | June 21 | | | | Spica upon the meridian. | | | | | | Passed the meridian. | | | | | | α Aquilæ - 67° 40' 0" | | | | | | Sun's limbs. | | | | | | Mr. Dixon. | | | | | | Ditto. | | | | | | Spica upon the meridian. | | | | | | Arcturus, ditto. | | | | | | Bootis. | | | | | | α Coronæ borealis. | | June 23 | | | | Spica upon the meridian. | | | | | | Arcturus, ditto. | | | | | | Bootis, ditto. | | | | | | Antares, ditto. | | | | | | The third satellite of 24 not immersed. | | | | | | Clouds. | | | | | | It was immersed. | | | | | | Zenith distance 3° 3' 30" Fomalhaut upon the meridian. Quadrant west. | From this day to the 1st of July, cloudy, with strong winds and rain. D d d 2 1761. | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | July 1 | Time per clock | Time per clock | | 1761 | 12 58 24½ | 19 25 46 : 16 14 32 : Antares - 42 20 0 | | | 13 0 51 + 28 14 : 16 14 32½ | | | | 3 18 Clouds. | | | | 14 29½ | 19 0 0 | | | 16 56 | 12 8½ | | | 19 23 + 14 35 | 16 14 32½ | | | | 16 14 32½ | | | 17 17 23 Zenith distance | 2 58 6 S. | | | | | | 24 2 | Ditto - - | 3 40 48 S. | | | 17 17 0 | Ditto - - 2 58 8 S. | | | 18 5 0 | Ditto - - 4 1 45 N. | | | 22 44 0 | Ditto - - 3 3 8 N. | | 2 3 | Ditto - - | 3 40 52 S. | | | 17 0 | Ditto - - 2 58 0 S. | | | 18 0 0 | Ditto - - 4 1 42 N. | | | 22 44 0 | Ditto - - 3 3 4 N. | | | | | | Equal altitudes. | Passed the mer. | | 8 7 | 13 14 23 | 19 9 33 : 16 14 24½ : Antares point 39 0 0 | | | 16 49 | 12 0 + 16 14 24½ | | | 19 16 + 14 26½ | 16 14 24½ | | | | | | | 16 35 24 Zenith distance | 3 41 32 : S. | | | 17 17 0 | Ditto - - 2 58 40 S. | | | 18 5 0 | Ditto - - 4 1 0 N. | | 8 8 | Ditto - - | 3 41 34 S. | | | 17 17 0 | Ditto - - 2 58 48 S. | | | 18 5 0 | Ditto - - 4 1 8 N. | Plane of the quadrant facing the west. Plane of the quadrant facing the east. 1761. ### Equal altitudes | Time per clock | Passed the meridian | |----------------|---------------------| | **July** | | | 24 9 | | | 13 14 13 | 16 14 14½ | | 16 39 | 16 14 14 | | 19 6½ | 16 14 14½ | | 16 35 8 | Zenith distance | | 17 17 0 | Ditto | | 18 5 0 | Ditto | | 22 44 0 | Ditto | ### Equal altitudes | Time per clock | Passed the meridian | |----------------|---------------------| | **O 12** | | | 13 31 39 | 16 13 59 | | 34 5 | 16 13 59 | | 36 33 | 16 13 59½ | | 15 50 45 + | Zenith distance | | 14 47 22 | | ### Equal altitudes | Time per clock | Passed the meridian | |----------------|---------------------| | **§ 15** | | | 13 0 0 | 16 13 43½ | | 33 49 | 16 13 43½ | | 36 17 - | | ### Nonius of the micrometer | Inches | Moon's southern limb from σ Sagittarii | |----------------|----------------------------------------| | 17 45 18 | Ditto | | 52 55 | Ditto | | 57 58 | Ditto | | 18 2 15 | Ditto | | 7 45 | Ditto | σ 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'. A little hazy. | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | July 17 | 16 0 22 + 23 9 47½ | 19 37 53½ | | | 3 10 12 36 | 19 37 53 | | | 5 59½ 15 24 | 19 37 53 | The second satellite of 24 immersed | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Aug. 21 | 5 14 59½ 10 41 53 - 8 2 5 | Sun's limb - 66 30 0 | | | 18 38 - 45 32 + 8 2 5 | | | 22 17 + 49 11 - 8 2 5½ | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Aug. 29 | 15 20 19½ 23 48 32 + 19 37 5½ | α Aquilae - 73 20 0 | | | 22 59 51 11½ 19 37 5½ | | | 25 38½ 53 51 : | The third satellite of 24 immersed Ditto emerged The first satellite immersed Ditto, per Mr. Dixon. | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Aug. 7 | 15 30 13½ 23 37 18 - 19 36 28 | α Aquilae - 71 20 0 | | | 32 54 - 39 59 + 19 36 26½ | | | 35 36 42 40½ 19 36 27 | The 2d satellite of 24 immersed. A little hazy The first immersed. Clear | Date | Zenith distance | Scorpii upon the meridian. | |------|-----------------|-----------------------------| | Aug. 8 | 15 48 54 - 14 47 40 | Antares ditto. | | | 16 12 0 | | | | Ditto | | | Date | Zenith distance | Ophiuchi upon the meridian. | |------|-----------------|-----------------------------| | Aug. 9 | 17 4 45 | Sagittarii ditto. | | | 18 3 0 | | | | Ditto | | | | 9 11 42 | | | | 4 1 28 | | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Aug. 10 | Time per clock | Time per clock | | h | h | h | | 15 19 28 + 23 47 37 | 19 36 12 | α Aquilae - 73 20 0 | | 22 7 - 50 17 + | 19 36 12 | | | 24 47 - 52 55½ | 19 36 11¾ | | | 16 3 50 Zenith distance | 8 55 48 | ρ Scorpii upon the meridian | | 11 0 Ditto | 8 2 54 | Antares ditto | | 0 53 45 The fourth satellite of ¼ immersed | - - - - 15 32 57 | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Sep. 12 | Time per clock | Time per clock | | h | h | h | | 15 19 18½ | 23 47 28 | 19 36 2¾ | α Aquilae - 73 20 0 | | 21 58 : 50 8 - | 19 36 3 : | | | 24 37½ | 52 47 - | 19 36 2¾ | | | 14. 23 36 11 The first satellite of ¼ immersed | - - - - 14 0 50 | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Sep. 20 | Time per clock | Time per clock | | h | h | h | | I put the clock forward. | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Sep. 21 | Time per clock | Time per clock | | h | h | h | | 16 39 26½ | 22 36 0½ | 19 40 43½ | α Aquilae - 59 40 0 | | 42 22 | 39 4¾ | 19 40 43¾ | | | 45 26 - | 42 6½ | 19 40 43½ | | | 2 2 35 The first satellite of ¼ immersed | - - - - 15 56 2 | | 2 30 Ditto, per Mr. Dixon. | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Oct. 23 | Time per clock | Time per clock | | h | h | h | | 16 51 19 : | 22 23 34 - | 19 40 35¾ | α Aquilae - 57 40 0 | | 54 27 - | 26 44½ | 19 40 35¾ | | | 57 37½ | 29 52 + | 19 40 35½ | | | 20 38 8 The first satellite of ¼ immersed | - - - - 10 25 10 | | 38 2 Ditto, per Mr. Dixon. | 1761. | Date | Equal altitudes | Passed the meridian | |------|----------------|---------------------| | Aug. 27 | Time per clock | Time per clock | | h | " | h | " | | 16 50 58 + | 22 23 14 - | 19 40 15 | | 54 6 - | 26 24 | 19 40 15 | | 57 16 + | 29 32 + | 19 40 15 + | | α Aquilae | 57 40 0 | Apparent time. The fourth satellite of ¼ immersed - - - 9 53 32 Ditto, per Mr. Dixon. The fourth satellite emerged - - - - 12 49 0 | Date | Equal altitudes | Passed the meridian | |------|----------------|---------------------| | Oct. 30 | Time per clock | Time per clock | | h | " | h | " | | 16 50 40½ | 22 22 58 - | 19 39 58½ | | 53 49 - | 26 8 - | 19 39 58½ | | 56 59 - | 29 16 | 19 39 58½ | | α Aquilae | 57 40 0 | Apparent time. The first satellite of ¼ immersed - - - 12 21 32 Sept. 8 1. The 2d satellite of ¼ immersed. Flying clouds 9 2 20 | Date | Equal altitudes | Passed the meridian | |------|----------------|---------------------| | 24 3. | Time per clock | Time per clock | | h | " | h | " | | 17 22 52½ | 21 49 16 | 19 39 42½ | | 26 24 + | 52 52 | 19 39 38 | | 30 8½ :: | 56 25½ | 19 39 39 | | α Aquilae | 52 40 0 | Apparent time. A small * immersed behind the D 7 1 52 Another very small * ditto - - 7 34 24 The 3d satellite of ¼ immersed - 8 36 33 Ditto. | Date | Equal altitudes | Passed the meridian | |------|----------------|---------------------| | 9 4. | Time per clock | Time per clock | | h | " | h | " | | 17 Clouds. | 21 49 10 | 19 39 32½ | | 26 18½ | 52 47½ | 19 39 33 | | 29 55½ | 56 19 + | α Aquilae | 52 49 0 | Apparent time. 25 Librae immersed behind the D - - - 7 6 53½ Ditto. emerged from the D. 1761. | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Sept. 6 | 17 22 32 - 21 48 56½ | 19 39 19½ | | | 26 5½ 52 32½ | 19 39 19 | | | 29 42½ 56 6 - | 19 39 19 | | Sept. 7 | 18 13 24 Zenith distance | 8 23 46 | | Sept. 8 | 22 52 15 The second satellite of 24 immersed | Apparent time: 11 42 20 | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Sept. 22 | 19 0 29 + 2 20 47½ | 22 43 8¾ | | | 3 0 23 18 - | 22 43 9 | | | 5 30 - Clouds. | | | | 19 37 48 Zenith distance | 42 10 42 | | | 22 43 16½ Ditto | 3 3 16 | | Sept. 24 | 21 27 14 The first satellite of 24 emerged | Apparent time: 9 21 35 | | | 27 15 Ditto, per Mr. Dixon. | | | Date | Equal altitudes | Passed the meridian | |------|-----------------|---------------------| | Sept. 27 | 19 29 38½ | 1 51 1 | | | 32 7 + 53 29½ | 22 42 48¾ | | | 34 36 - 55 57½ | 22 42 48¾ | | Sept. 28 | Packed up the instruments. | | | Oct. 29 | Put them on board the Mercury, Capt. Harrold. | | | Oct. 3 | Sailed for St. Helena. | | Charles Mason. The instruments made use of, in these observations, were, Two reflecting telescopes, each two feet focal length, and magnifying 120 times, made by Mr. Short. A quadrant of one foot radius, made by Mr. Bird, and the property of the Earl of Macclesfield. An astronomical clock, made by Mr. Ellicott. APPENDIX. Eclipses of Jupiter's satellites, observed at the Royal Observatory at Greenwich, with a reflector of two feet focus, magnifying 95 times. | Apparent time | Immersion of the third satellite. | |---------------|----------------------------------| | June 23. | 15 10 24 | | July 20. | 15 54 28 - - - of the second. | | 22. | 12 35 29 - - - of the first. | | Aug. 7. | 10 51 52 - - - of the first. | | Sept. 8. | 10 28 5 - - - of the second. | | 10. | 11 27 6 - - - of the third. | | 15. | 13 6 36 - - - of the second. | | 24. | 8 7 46 Emersion of the first. | Eclipses of Jupiter's satellites, observed at Mr. Short's house in Surry-street in the Strand, London, by Dr. Bevis, with a re- flecting telescope of four feet focal length, magnifying 140 times, and by Mr. Short, with a reflector of two feet focus, magni- fying 95 times. | Apparent time | Immersion of the first satellite, by Dr. Bevis. | |---------------|-------------------------------------------------| | July 22. | 12 35 13 | | | 12 34 58 | | Aug. 7. | 10 29 43 - - - of the 2d satellite, by Dr. Bevis.| | | 10 29 31 | | 27. | 8 41 16 - - - of the 4th satellite, by Dr. Bevis.| | | 8 37 4 | | 30. | 11 7 31 - - - of the first satellite, by Mr. Short.| | Sept. 8. | 10 29 3 - - - of the 2d satellite, by Dr. Bevis.| | | 10 28 35 | N. B. Mr. Short's house is 26' ¼ of time to the west of the Royal Observatory. LXI. Lat-