Observations Made, by Appointment of the Royal Society, at King George's Island in the South Sea; By Mr. Charles Green, Formerly Assistant at the Royal Observatory at Greenwich, and Lieut. James Cook, of His Majesty's Ship the Endeavour

XLIII. Observations made, by appointment of the Royal Society, at King George's Island in the South Sea; by Mr. Charles Green, formerly Assistant at the Royal Observatory at Greenwich, and Lieut. James Cook, of his Majesty's Ship the Endeavour. Read November 21, 1771. 1769 April 13 We came to an anchor in Royal Bay in King George's island. Fixed upon the North point of the bay, which is the most Northern point of the island, for the place of observation; here we built a small fort, to secure us against the natives, which we called fort Venus: it was not finished and the instruments set up in proper order until the 10th of May, therefore the time for all observations made before this day, was taken by a watch with a second hand, the going of which was ascertained by altitudes of the sun as often as were necessary. The astronomical clock, made by Shelton and furnished with a gridiron pendulum, was set up in the middle of one end of a large tent, in a frame of wood made for the purpose at Greenwich, fixed firm and as low in the ground as the door of the clock-case would admit, and to prevent its being disturbed by any accident, another framing of wood was made round this, at the distance of one foot from it. The pendulum was adjusted justed exactly to the same length as it had been at Greenwich. Without the end of the tent facing the clock, and 12 feet from it, stood the observatory, in which were set up the journeyman clock and astronomical quadrant: this last, made by Mr. Bird, of one foot radius, stood upon the head of a large cask fixed firm in the ground, and well filled with wet heavy sand. A centinel was placed continually over the tent and observatory, with orders to suffer no one to enter either the one or the other, but those whose business it was. The telescopes made use of in the observations were—Two reflecting ones of two feet focus each, made by the late Mr. James Short, one of which was furnished with an object glass micrometer. Thus furnished, the following observations were made. Observations of equal Altitudes of the Sun for the Time, made with the Astronomical Quadrant. | Time per clock of the Sun's Limb passing the Wires at equal Altitudes | Observatory Side of the clock | Remarks | |---|---|---| | **1769** | | | | 9 39 5½ | 41 43 | 42 20 | 44 65 | 45 18 | Mean noon per clock. | Baro. Th. | Baro. Th. | | 2 May 10 | 2 04 11½ | 2 35 | 00 57 | 1 58 53 | 58 18 | 55 34½ | 30 18 86 | 30 19 82 | | | 11 51 38½ | 51 39 | 51 38½ | 51 39 | 51 38½ | 11 51 38½ | 30 16 83 | 30 15 82 | | | | | | | | | C. G. | | 9 09 08 | 11 36 | 12 09 | 14 00 | 14 35 | 17 01 | 30 22 89 | 30 20 84 | | 2 12 | Cloudy | 2 30 08 | 29 36 | Cloudy | 27 10 | 24 45 | 30 29 85 | 30 14 88 | | | | | | | | | C. G. | | 9 11 38 | 14 04 | 14 40 | 16 31 | 17 04½ | 19 33 | 30 35 89 | 30 15 86 | | 2 10 | 2 29 22 | 26 58 | 26 24 | too late for these wires. | 11 50 31 | 30 1 83 | 30 09 86 | | | | | | | | | C. G. | | 9 39 23 | 42 08 | 42 47 | 44 52 | 45 30 | 48 16 | 30 16 87 | 30 14 86 | | 14 | Cloudy | | | | | | 30 20 86 | 30 19 88 | | | | | | | | | C. G. | | Without stop | 9 15 34 | 18 05 | 18 40 | 20 36 | 21 11 | 23 44 | | | | 2 23 14 | 20 43 | 20 09 | 18 12 | 17 38 | 15 05 | | | | 11 49 24 | 49 24 | 49 24½ | 49 24 | 49 24½ | 11 49 9½ | | | Without stop | 9 27 52 | 30 30 | 31 05 | 33 09 | 33 45½ | 36 25 | | | | 2 10 27 | 7 50 | 7 14 | 5 9½ | 4 33½ | 11 49 9½ | | | | | | | | | | C. G. | | Stop | 8 21 02 | 23 15 | 23 45 | 25 27 | 25 56 | 28 11 | None good but the first, all the rest in a confused haze CG | | | 3 16 41½ | | | | | | | | | 11 48 5½ | 48 52½ | 48 51 | 48 50½ | | | | Reading off | 8 36 31½ | 48 47 | 49 19 | 41 05 | 43 53 | 30 10 82 | 30 10 84 | | | 3 01 11 | 2 59 00½ | 58 26½ | Cloudy | 56 06½ | 30 09 82 | 30 08 80 | | | 11 48 5½ | 48 53½ | 48 52½ | | | | | | | | | | | | | | | | 9 44 5½ | 47 44 | 48 23 | 50 39 | 51 19 | 54 17 | | | | 1 51 07 | 48 12 | 47 27 | 45 19 | 44 36 | 41 42 | | | | 10 3 39 | 47 59 | 47 55 | 47 59 | 47 57½ | 11 47 58 | | | | 1 32 17 | | | | | | | | | 11 47 58 | | | | | | | | | | | | | | | | | | 9 12 24 | 14 59½ | 15 34 | 17 33 | 17 20 | 20 43 | | | | 2 22 27 | 19 54 | 19 20 | 17 20 | | | | | 11 47 25½ | 47 26½ | 47 27 | 47 26½ | | | | | 9 30 46½ | 33 31 | 34 07 | 36 16 | 36 55 | 39 42½ | | | | 2 03 57 | 1 15 | 2 00 39 | 58 28 | 57 52 | 55 05 | | | | 11 47 21½ | 47 23 | 47 23½ | 47 22 | 47 23½ | 11 47 22½ | | Observations Observations of equal Altitudes of the Sun for the Time, made with the Astronomical Quadrant. | Time per clock of the Sun's Limb passing the Wires at equal Altitudes. | Observatory | Side of the clock. | Remarks | |-----------------------------------------------------------------------|-------------|--------------------|---------| | **May** | | | | | Reading off | | | | | 24 | | | | | With stop | | | | | **25** | | | | | **27** | | | | | **28** | | | | | **29** | | | | | Reading off | | | | | **30** | | | | | **June** | | | | Mean noon per clock: - Baro. Th. - Baro. Th. Observations J. C. Observations of equal Altitudes of the Sun for the Time, made with the Astronomical Quadrant. | Time per Clock of the Sun's Limb passing the Wires at equal Altitudes | Observatory | Side of the clock | Remarks | |---|---|---|---| | **1769** | | | | | June | | | | | 7 39 46 | 41 48 | 42 12 | 43 52 | 44 24 | 46 29 | Mean noon per clock | | 4 12 53 | 10 43 | 10 18 | 8 37 | 8 6 | 6 1 | | 2 11 56 | 14 56 | 15 56 | 14 56 | 15 56 | 15 56 | 11 56 15 | | 7 54 39 | 56 52 | 57 17 | 58 59 | 59 32 | 8 01 38 | | 3 57 54 | 55 42 | 55 17 | 53 34 | 53 02 | 50 55 | | 11 56 16 | 56 17 | 56 17 | 56 16 | 56 16 | 56 16,8 | | **J** | | | | | 7 36 43 | 39 01 | 39 25 | 41 03 | 41 37 | 43 42 | | 4 15 17 | 13 00 | 12 35 | 10 57 | 10 26 | 8 22 | | 3 11 56 | 00 56 | 56 00 | 56 00 | 60 01 | 56 02 | | 7 46 20 | 48 32 | 48 57 | 50 38 | 51 10 | 53 15 | | 4 5 40 | 3 28 | 3 05 | 1 21 | 00 50 | 58 45 | | 11 56 00 | 56 00 | 56 01 | 55 59 | 56 00 | 56 0 | | **With stop** | | | | | 8 11 43 | 14 02 | 14 26 | 16 12 | 16 45 | 18 56 | | 3 39 58 | 37 40 | 37 16 | 35 29 | 34 56 | 32 45 | | 4 11 55 | 50 51 | 55 51 | 55 50 | 55 50 | 55 50 | | 8 29 50 | 32 13 | 32 38 | 34 28 | 35 02 | 37 16 | | **With stop** | | | | | 3 21 50 | 19 28 | 19 04 | 17 13 | 16 39 | late | | 11 55 50 | 55 50 | 55 51 | 55 50 | 55 50 | 11 55 50 | Note, the clock was exposed to the sun from 9 or 10 o'clock in the morning till 4 in the afternoon, J. C. The observations of both yesterday and today are as good as can be made, J. C. C. G. Cloudy Cloudy in the afternoon. Vol. LXI. F f f Observations Observations of equal Altitudes of the Sun for the Time, made with the Astronomical Quadrant. | Time per Clock of the Sun's Limb passing the Wires at equal Altitudes | Observatory | Side of the clock | Remarks | |---|---|---|---| | **June** | | | | | 1769 | | | | | 7 52 56 | 55 33 | 55 36 | 57 52 | Mean noon per clock | | 12 | 11 | 54 35 | 54 34 | 11 54 34½ | | 9 14 52 | 17 34 | 18 02 | 20 06 | 20 45 | | 2 34 10 | 31 28 | 30 59 | 28 54 | 28 15 | | 11 54 31 | 54 31 | 54 30½ | 54 30 | 54 30 | | 8 34 03 | 36 10 | 36 57 | 38 49 | 39 23 | | 3 14 37 | 12 10 | 11 45 | 9 54 | 9 21 | | 11 54 20 | 54 20½ | 54 21 | 54 21½ | 54 22 | | 8 15 31 | 17 52 | 18 15 | Cloudy | 20 36 | | Cloudy | 3 30 04 | 29 41 | 27 52 | Cloudy | | 53 58 | 53 58 | 53 57 | 53 57 | | 8 29 32 | 31 59 | Cloudy | 34 16 | 34 48 | | 3 15 55 | 15 33½ | 13 40½ | 13 06 | 53 57 | | 53 57 | 53 57 | 53 57 | 53 57 | | 9 13 48 | 16 32 | 16 59 | 19 04 | 19 42 | | 2 33 48 | 31 05 | 30 39 | 28 32 | 27 55 | | 11 53 48 | 53 48½ | 53 49 | 53 48½ | 53 48½ | | 8 52 55 | 55 28 | 55 55 | 57 49 | 58 25 | | 2 54 30 | 51 30 | 19 34 | 48 57 | 46 33 | | 11 53 42½ | 53 42½ | 53 41½ | 53 41½ | 53 41½ | | 8 13 26 | 15 47 | 16 11 | 18 00 | 18 33 | | 3 33 45 | 31 24 | 31 00 | 29 11 | 28 38 | | 11 53 35½ | 53 35½ | 53 35½ | 53 35½ | 53 35½ | | 7 49 01 | 51 15 | 51 38 | 53 22 | 53 54 | | 3 57 50 | 55 35 | 55 12 | 53 27 | 52 55 | | 11 53 25½ | 53 25 | 53 25 | 53 24½ | 53 24½ | | 8 25 23 | 3 21 14 | Cloudy in the afternoon. | 11 53 18½ | | 11 53 18½ | | | | | 7 57 50 | 8 00 07 | 0 30 | 2 15 | 2 49 | | 3 48 10 | 45 54 | 45 31 | 43 46 | 43 12 | | 11 53 00 | 53 00½ | 53 00½ | 53 00½ | 53 00½ | | Observations | | | | Observations of equal Altitudes of the Sun for the Time, made with the Astronomical Quadrant. | Time per clock of the Sun's Limb passing the Wires at equal Altitudes. | Observatory | Side of the clock. | Remarks | |-----------------------------------------------------------------------|-------------|--------------------|---------| | June | Baro. Th. | Baro. Th. | C. G. | | 1769 | 30 18 84 | 30 15 81 | | | 25 | | | | | 10 06 49 | | | | | 10 12 | | | | | 10 50 | | | | | 13 35 | | | | | 14 27 | | | | | 17 50 | | | | | Mean noon per clock. | | | | | 30 14 78 | | | | | 30 07 78 | | | | | 30 10 80 | | | | | July | Baro. Th. | Baro. Th. | C. G. | | 8 02 29 | 30 18 76 | 30 12 75 | | | 3 41 10 | 30 15 83 | 30 11 84 | | | 11 51 49½ | | | | | Cloudy in the afternoon. | | | | | 11 51 49½ | | | | | 9 07 13 | | | | | 9 51 | | | | | 10 19 | | | | | 12 21 | | | | | 13 00 | | | | | 15 31 | | | | | 3 36 10 | | | | | 33 34 | | | | | 33 06 | | | | | 31 02 | | | | | 30 25 | | | | | 27 52 | | | | | 51 41½ | | | | | 51 42½ | | | | | 51 42½ | | | | | 51 41½ | | | | | 11 51 42 | | | | | 7 33 21 | | | | | 35 33 | | | | | 35 55 | | | | | 37 36 | | | | | 38 07 | | | | | 40 13 | | | | | 4 09 43 | | | | | 7 31 | | | | | 5 27 | | | | | 4 57 | | | | | 2 50 | | | | | 11 51 31½ | | | | | 11 51 31,8 | | | | | 7 29 44 | | | | | 31 57 | | | | | 32 19 | | | | | 34 01 | | | | | 4 12 35 | | | | | 10 24 | | | | | 10 03 | | | | | 8 19 | | | | | 11 51 09½ | | | | | 51 10 | | | | | 11 51 10¼ | | | | Took down the Clocks and Observatory; the Pendulum vibrated 1° 55' on each Side the Center, the Bob remained as at Greenwich. Account of the going of the Astronomical clock at King George's Island, deduced from the foregoing Observations. | Day of the Month | Corrected noon per clock | Mean Time | Clock flow for M. T. | Clock loses | Interval of Days | Daily loses of clock | |------------------|--------------------------|-----------|----------------------|-------------|-----------------|---------------------| | May | | | | | | | | 1769 | H. M. S. | H. M. S. | M. S. | M. S. | | | | May | | | | | | | | 10 | 11 51 44.8 | 11 56 2.8 | 4 18.0 | 0 43.4 | 2 | 21.7 | | 12 | 11 50 58.3 | 11 55 59.7| 5 1.4 | 0 20.9 | 1 | 20.9 | | 13 | 11 50 36.7 | 11 55 59.0| 5 22.3 | 0 22.7 | 1 | 22.7 | | 14 | 11 50 13.7 | 11 55 58.7| 5 45.0 | 1 1.4 | 3 | 20.5 | | 17 | 11 49 15.0 | 11 56 1.4 | 6 46.4 | 0 20.6 | 1 | 20.6 | | 18 | 11 48 56.4 | 11 56 3.4 | 7 7.0 | 1 2.5 | 3 | 20.8 | | 21 | 11 48 3.0 | 11 56 12.5| 8 9.5 | 0 42.5 | 2 | 21.2 | | 23 | 11 47 29.4 | 11 56 21.4| 8 52.0 | 0 20.5 | 1 | 20.5 | | 24 | 11 47 14.1 | 11 56 26.6| 9 12.5 | 0 18.7 | 1 | 18.7 | | 25 | 11 47 1.1 | 11 56 32.3| 9 31.2 | 0 45.9 | 2 | 22.9 | | 27 | 11 46 28.1 | 11 56 45.2| 10 17.1 | 0 14.6 | 1 | 14.6 | | 28 | 11 46 20.7 | 11 56 52.4| 10 31.7 | 0 22.2 | 1 | 22.2 | | 29 | 11 46 6.3 | 11 57 0.2 | 10 53.9 | 0 19.0 | 1 | 19.0 | | | The clock was put forward 10' 57". | | | | | | | 30 | 11 56 52.5 | 11 57 8.4 | 0 15.9 | 0 22.2 | 1 | 22.2 | | June | | | | | | | | 31 | 11 56 39.0 | 11 57 17.1| 0 38.1 | 0 19.0 | 1 | 19.0 | | 1 | 11 56 29.1 | 11 57 26.2| 0 57.1 | 0 19.6 | 1 | 19.6 | | 2 | 11 56 18.9 | 11 57 35.6| 1 16.7 | 0 25.5 | 1 | 25.5 | | 3 | 11 56 3.2 | 11 57 45.4| 1 42.2 | 0 20.1 | 1 | 20.1 | | 4 | 11 55 53.3 | 11 57 55.6| 2 23.3 | 0 23.0 | 1 | 23.0 | | 5 | 11 55 40.8 | 11 58 6.1 | 2 25.3 | 0 20.8 | 1 | 20.8 | | 6 | 11 55 30.9 | 11 58 17.0| 2 46.1 | 0 22.3 | 1 | 22.3 | | 7 | 11 55 19.8 | 11 58 28.2| 3 8.4 | 0 20.2 | 1 | 20.2 | | 8 | 11 55 11.0 | 11 58 39.6| 3 28.6 | 0 26.5 | 1 | 26.5 | | 9 | 11 54 56.1 | 11 58 51.2| 3 55.1 | 0 37.5 | 2 | 18.7 | | 11 | 11 54 42.3 | 11 59 14.9| 4 32.6 | 0 18.7 | 1 | 18.7 | | 12 | 11 54 35.8 | 11 59 27.1| 4 51.3 | 0 16.4 | 1 | 16.4 | | 13 | 11 54 31.8 | 11 59 39.5| 5 7.7 | 0 22.2 | 1 | 22.2 | | 14 | 11 54 22.1 | 11 59 52.0| 5 29.9 | 1 2.0 | 3 | 20.7 | | 17 | 11 53 58.1 | 0 30.0 | 6 31.9 | 0 22.0 | 1 | 22.0 | | 18 | 11 53 48.9 | 0 42.8 | 6 53.9 | 0 19.8 | 1 | 19.8 | | 19 | 11 53 42.0 | 0 55.7 | 7 13.7 | 0 19.3 | 1 | 19.3 | | 20 | 11 53 35.6 | 0 8.6 | 7 33.0 | 0 23.6 | 1 | 23.6 | | 21 | 11 53 24.8 | 0 1.4 | 7 56.6 | 0 19.4 | 1 | 19.4 | | 22 | 11 53 18.2 | 0 34.2 | 8 16.0 | 0 43.6 | 2 | 21.8 | | 24 | 11 53 0.0 | 0 59.6 | 8 59.6 | 0 20.9 | 1 | 20.9 | | 25 | 11 52 51.7 | 0 12.2 | 9 20.5 | 0 42.5 | 2 | 21.2 | | 27 | 11 52 34.1 | 0 37.1 | 10 30.0 | 0 45.6 | 5 | 21.1 | | July | | | | | | | | 2 | 11 51 47.5 | 3 36.1 | 11 48.6 | 0 18.9 | 1 | 18.9 | | 3 | 11 51 39.7 | 3 47.2 | 12 7.5 | 0 20.9 | 1 | 20.9 | | 4 | 11 51 29.6 | 3 58.0 | 12 28.4 | 0 42.5 | 2 | 21.2 | | 6 | 11 51 7.7 | 4 18.6 | 13 10.9 | | | | Hence the daily rate of the clock's losing on mean time, by a mean of these 40 results, is 20.8 seconds. By the first and last days observations compared together, the clock lost 19' 49.7" on mean time in 57 days, which is at the rate of 20,"/88 or 20,"/9 per day. The swing of the pendulum pendulum on each side of the perpendicular during this time, varied between $1^\circ 50'$ and $1^\circ 55'$. **Remark.** The same clock, when fixed up at the Royal Observatory at Greenwich, before the voyage, with the pendulum of the same length, got at the rate of $1' 45.8''$ per day, on mean time, between April 19 and July 18, 1768. Therefore the force of gravity at Greenwich is to that at King George's Island, as 1000000 to 997075. N. M. ### Observations of meridian zenith distances of the sun and fixed stars for finding the latitude of the Observatory. | Day of the month | Name of the object | Meridian zen. dist. | Latitude South | Mean | |------------------|--------------------|---------------------|----------------|------| | May 6 | Sun's lower limb | 34° 33' 7" | 17° 29' 17" | | | May 27 | Sun's upper limb | 38° 39' 10" | 17° 27' 52" | | | May 28 | Ditto | 38° 50' 0" | 17° 29' 9" | | | May 29 | Ditto | 38° 59' 0" | 17° 29' 2" | | | May 30 | Ditto | 39° 8' 12" | 17° 29' 26" | | | May 31 | Ditto | 39° 16' 21" | 17° 29' 11" | | | June 7 | Ditto | 40° 3' 32" | 17° 29' 29" | | | June 8 | Ditto | 40° 9' 0" | 17° 28' 42" | | | June 9 | Ditto | 40° 13' 0" | 17° 27' 51" | | | June 10 | Ditto | 40° 17' 0" | 17° 27' 54" | | | June 11 | Ditto | 40° 21' 0" | 17° 27' 21" | | | June 12 | Ditto | 40° 26' 0" | 17° 28' 42" | | | June 13 | Ditto | 40° 29' 0" | 17° 28' 28" | | | June 15 | Ditto | 40° 34' 0" | 17° 28' 14" | | | June 17 | Ditto | 40° 36' 30" | 17° 27' 10" | | | June 18 | Ditto | 40° 38' 30" | 17° 27' 59" | | | June 19 | Ditto | 40° 39' 0" | 17° 27' 48" | | | June 20 | Ditto | 40° 39' 30" | 17° 27' 54" | | | June 22 | Arcturus | 37° 53' 0" | 17° 30' 29" | | | June 24 | α Lyrae | 56° 3' 20" | 17° 29' 53" | | | June 27 | γ Aquilæ | 27° 32' 20" | 17° 28' 45" | | | June 28 | α Aquilæ | 25° 44' 30" | 17° 28' 20" | | | June 28 | β Aquilæ | 23° 19' 0" | 17° 28' 30" | | | June 24 | α Cygni | 61° 56' 0" | 17° 29' 36" | | | June 28 | | 61° 54' 40" | 17° 28' 16" | | The... The sun and foregoing stars passed the meridian to the North; the following stars passed the meridian to the South above the poles. | Day of the month | Name of the object | Meridian zen. dist. | Latitude South | Mean | |------------------|--------------------|---------------------|----------------|------| | 1769 | | D. M. S. | | | | June 23 | Fomalhaut | 13 20 | 17 29 37 | 17 29 37 | | June 24 | γ Crucis | 44 20 | 17 28 44 | 17 28 44 | | June 25 | γ Crucis | 38 19 | 17 29 50 | 17 29 50 | | June 21 | β Crucis | 40 54 30 | 17 30 36 | 17 30 28 | | June 22 | α Centauri | 42 22 | 17 29 59 | 17 30 9 | | June 24 | β Centauri | 41 44 10 | 17 30 9 | 17 29 56 | | June 27 | β Centauri | 41 44 26 | 17 29 53 | 17 29 47 | | June 23 | β Gruis | 30 33 40 | 17 30 18 | 17 29 58 | | June 24 | β Gruis | 30 35 | 17 28 18 | 17 29 58 | | June 25 | 3 Hydri | 61 1 15 | 17 29 54 | 17 29 54 | | June 24 | α Pavonis | 39 57 36 | 17 28 5 | 17 28 31 | | June 28 | α Pavonis | 139 56 44 | 17 28 57 | 17 28 31 | The mean of the seven mean results from the sun and six stars, to the North, gives the latitude $17^\circ 28' 51''$ S. The mean of the nine results from the nine stars to the South, gives the latitude $17^\circ 29' 38''$ S. The mean of these two means is $17^\circ 29' 15''$ S. which may be taken for the latitude of the observatory. N. B. Before any observations were made with the quadrant, the line of collimation was adjusted, by means of a distant object, by inverting the quadrant. Remark. It must be confessed, that the results of these observations (most of which were made by Mr. Green) differ more from one another than they ought to do, or than those done made by other observers, with quadrants of the same size, and made by the same artifit, the cause of which, if not owing to want of care and address in the observer, I don't know how to assign. N. M. ## Lunar Observations for the Longitude. | Month | Day | Time per clock | Alt. or Z.D. of the Sun | Alt. or Z.D. of the Moon | Dist. of D.a.O. or D and * | Whether Alt. or Z.D. and what Limb | Error of Quadrant | Apparent Time cor. | Longitude given | Mean of each day's sets | |-------|-----|----------------|-------------------------|--------------------------|---------------------------|-----------------------------------|------------------|-----------------|-----------------|------------------------| | April | 22 | 17 30 | 49 34 00 | 54 30 50 | 57 31 30 | Sun's Alt. L.L. | Dan. Sun - 2 | 22 25 40 | 149 23 15 | | | | 30 | 18 46 | 51 10 00 | 52 00 10 | 26 40 | Moon's Alt. U.L. | D - 5 | 37 24 | 20 30 | | | | | 27 54 | 52 16 40 | 49 52 50 | 23 55 | | | 46 24 | 25 45 | | | May | 9 | 52 57 | 27 29 40 | 79 54 00 | 52 55 00 | *'s N.L. | *'s Altitude | 2 00 | 10 03 19 | 148 59 00 | | | 10 | 02 34 | 24 58 20 | 77 51 40 | 52 58 10 | | | 12 56 | 149 14 15 | | | | | 12 57 | 22 34 20 | 75 21 00 | 53 01 05 | | | 23 19 | 39 15 | | | | 16 | | | | | | | | | | | Antares | 10 | 44 26 | 25 17 17 | 68 14 00 | 46 44 27 | *'s Zen.Dift. | *'s Z.D.+2 | 10 54 48 | 149 34 15 | | | | | 59 00 | 22 07 40 | 64 55 00 | 40 00 | | | 11 09 22 | 19 15 | | | | | 11 09 48 | 19 51 00 | 62 27 00 | 37 00 | | | 11 20 10 | 07 30 | | | Regulus | 8 | 05 46 | 47 28 30 | 26 53 10 | 64 29 30 | *'s Altitude | *'s Alt.-2 | 8 16 21 | 149 57 30 | | | | | 21 54 | 44 35 00 | 23 25 50 | 34 55 | | | 32 29 | 43 30 | | | | | 30 03 | 43 06 40 | 21 11 50 | 38 10 | | | 40 38 | 150 30 15 | | | D and O | 21 | 28 54 | 38 22 00 | 26 55 10 | 100 37 05 | *'s Alt. L.L. | *'s Alt.-6 | 21 42 22 | 148 01 45 | | | | | 42 29 | 40 31 20 | 24 05 50 | 30 45 | | | 21 55 59 | 21 45 | | | | | 55 34 | 42 25 40 | 21 03 40 | 24 40 | | | 22 09 04 | 27 30 | | | D and O | 22 | 24 35 | 45 50 00 | 32 16 50 | 75 25 30 | *'s Alt. L.L. | D - 4 | 22 38 30 | 149 52 00 | | | | | 29 51 | 46 24 00 | 31 06 00 | 23 50 | | | 43 46 | 30 00 | | | | | 39 19 | 47 21 00 | 28 57 20 | 20 10 | | | 53 14 | 41 43 | | | | | 44 48 | 47 52 20 | 27 40 40 | 18 20 | | | 58 43 | 30 30 | | | | | 51 33 | 48 22 20 | 26 08 20 | 15 40 | | | 23 05 28 | 21 30 | | | *α Aquila | 18 | 49 32 | 43 12 30 | 52 53 40 | 67 03 30 | *'s Altitude | D and *+1 | 18 52 44 | 149 54 15 | | | | | 50 38 | 41 56 30 | 54 06 40 | 05 26 | | | 59 50 | 150 52 15 | | | D and O | 22 | 10 57 | 42 36 20 | 45 37 40 | 62 31 50 | *'s Alt. L.L. | D - 4 | 22 14 09 | 150 05 15 | | | | | 18 03 | 43 36 20 | 44 05 40 | 30 20 | | | 21 15 | 149 36 30 | | | | | 25 28 | 44 19 00 | 42 32 20 | 27 40 | | | 28 40 | 28 15 | | | | | 30 40 | 45 10 20 | 41 28 50 | 25 20 | | | 33 58 | 42 30 | | | | | 35 53 | 45 48 00 | 40 28 20 | 23 50 | | | 39 05 | 34 30 | | | June | 4 | 18 53 | 13 36 00 | 42 52 20 | 111 32 50 | *'s Alt. L.L. | D's Alt.-3 | 4 24 17 | 151 03 00 | | | | | 28 12 | 11 37 00 | 40 36 40 | 34 10 | | | 33 56 | 150 19 30 | | | | | 37 56 | 9 39 50 | 38 24 00 | 36 20 | | | 43 20 | 18 30 | | | | | 3 17 | 25 56 40 | 66 39 40 | 122 20 45 | *'s Alt. L.L. | D's Alt.-3 | 3 22 53 | 148 43 30 | | | | | 22 54 | 24 35 50 | 65 03 20 | 24 30 | | | 28 25 | 149 35 20 | | | | | 29 43 | 23 23 40 | 63 33 20 | 26 50 | | | 35 15 | 22 20 | | | | | 44 48 | 20 25 20 | 60 01 40 | 32 10 | | | 50 08 | 08 15 | | | | | 50 48 | 19 07 00 | 58 34 40 | 35 00 | | | 56 20 | 29 00 | | Month. ## Lunar Observations for the Longitude. | Month | Day | Time per clock | Alt. or Z.D. of ⊙ or * | Alt. or Z.D. of the ♦ | Diff.of ♦a.⊙ or ♦ and * | Whether Alt. or Z.D. and what Limb | Error of Quadrant | Apparent Time cor. | Longitude given | Mean of each Days Sets | |-------|-----|----------------|------------------------|----------------------|--------------------------|-----------------------------------|------------------|------------------|-----------------|---------------------| | 1769 | | | | | | | | | | | | June | 10 | 09 34 47 59 | 40 | 12 26 40 | 55 33 20 | ♦’s Altitude | ♦’s Alt.+5° | 10 15 40 | 149 00 51 | | | * Spica | 20 | 14 45 26 | 10 | 12 14 00 | 36 50 | ♦’s Z.D.U.L. | ♦ and ♦+1° | 26 20 | 17 30 | | | | 28 | 34 43 30 | 00 | 10 36 20 | 40 00 | | | 34 40 | 39 17 | 149 18 55 | | | 17 | | | | | | | | | | | * Fomalh. | 13 | 27 30 46 46 | 00 | 68 20 00 | 63 08 20 | ♦’s Zen.Dift. | ♦’s Alt.L.L. | 13 33 46 | 150 01 15 | | | ⊙ | 18 | 49 44 20 | 26 | 65 53 00 | 5 10 | ♦’s Alt.L.L. | ♦ and ♦+1° | 45 05 | 26 00 | | | | | 46 56 42 | 36 | 00 64 15 | 3 30 | | | 53 12 | 10 15 | 150 12 30 | | * & Aquilae | 15 | 10 21 51 09 | 20 | 27 08 40 | 51 01 00 | ♦’s Altitude | ♦’s Alt.-3° | 15 17 26 | 150 15 30 | | | | 20 | 04 49 51 | 40 | 25 24 40 | 3 00 | ♦’s Z.D.L.L. | ♦ and ♦+1° | 27 09 | 149 52 00 | | | | 24 | 32 48 22 | 40 | 24 02 00 | 4 47 | | | 34 57 | 46 00 | 149 57 50 | | | 21 | 46 12 38 | 41 | 30 49 20 | 79 45 31 | | | 21 53 37 | 149 29 00 | | | | 26 | 20 39 53 | 40 | 29 08 00 | 42 20 | ⊙’s Alt.L.L. | ⊙’s Alt.-3° | 22 01 45 | 34 15 | | | | 22 | 4 03 41 | 12 | 27 05 00 | 38 10 | ⊙’s Alt.U.L. | ⊙ and ⊙+1° | 07 07 | 23 15 | | | | | 7 48 41 | 40 | 00 26 17 | 37 00 | | | 11 28 | 33 30 | 149 26 03 | | | 20 | 36 16 56 | 00 | 50 01 20 | 66 54 10 | | | 20 43 47 | 149 09 45 | | | | 27 | 44 07 28 | 23 | 48 56 20 | 50 30 | ⊙’s Alt.L.L. | ⊙’s Alt.-3° | 51 38 | 43 00 | | | | | 50 31 29 | 31 | 40 48 00 | 49 20 | ⊙’s Alt.U.L. | ⊙ and ⊙+1° | 58 02 | 12 15 | | | | | 55 34 30 | 25 | 20 47 14 | 47 26 | | | 21 03 02 | 27 45 | 149 24 33 | | | | 59 52 31 | 09 | 40 46 34 | 45 40 | | | 07 23 | 30 00 | | | | 21 | 13 57 33 | 43 | 20 40 28 | 39 06 10 | ⊙’s Alt.L.L. | ⊙’s Alt.-3° | 21 21 44 | 149 52 30 | | | | 23 | 52 35 24 | 00 | 40 45 40 | 02 07 | ⊙’s Z.D.cent. | ⊙’s Alt.+1° | 31 39 | 150 14 45 | | | | 30 | 12 36 25 | 20 | 41 00 20 | 00 10 | | | 37 59 | 10 15 | 150 05 50 | **Note.** Every line of the Lunar Observations is the mean of three, which we call a set. We take three or five such sets at a time, and calculate the mean of each separately. The ground where all the Altitudes were taken, is 13 feet 6 inches above the horizontal level; the zenith distances are all taken with the Astronomical Quadrant. These distances of the Moon from the Sun and fixt flares, were observed with a brass Hadley's sextant, fitted with edge-bars, made by Mr. Ramsden. Mean of these Observations gives George’s Island to be in Long. 149° 36' 38" W. of Greenwich Observatory, at ♦’s fort. Observations Observations of the Eclipses of Jupiter's Satellites, with reflecting Telescopes of 2 Feet Focus, and the Longitude of the Observatory thence deduced. | Year | Time per clock | Apparent time cor. | Phænomena and Sat. | Time at Green. per Naut. Alm. | Long. W. of Green. in time | |------|----------------|--------------------|--------------------|-------------------------------|---------------------------| | 1769 | | | | | | | May | | | | | | | 10 | 10 02 30 | 16 11 1 | Emerf. of the 1st Sat. | | | | | 16 03 3c | Capt. Cook 16 12 1 | Ditto | | | | | 12 10 27 55 | 10 37 6 | | | | | | 10 28 05 | Capt. Cook 10 37 16 | | | | | | 27 11 44 04 | 11 57 39 | Second Satellite | | | | | 11 44 05 | Capt. Cook 11 57 40 | very clear | | | | | 11 47 15 | 12 00 51 | Third ditto | | | | | 11 48 08 | Capt. Cook 12 1 44 | First ditto | 20 44 39 | 9 59 4 | | June | | | | | | | 4 | 10 41 19 | 10 45 31 | | | | | | 10 41 28 | Capt. Cook 10 45 40 | | | | | | 13 7 02 45 | 7 08 19 | Ditto | 17 6 31 | 9 58 14 | | | 7 02 45 | Capt. Cook 7 8 16 | | | | | | 18 14 27 21 | 14 33 36 | Ditto | 24 31 41 | 9 57 41 | | | 14 28 09 | Capt. Cook 14 34 24 | | | | | | 20 8 55 15 | 9 1 43 | Ditto | 19 0 2 | 9 58 19 | | | 8 46 45 | 8 53 22 | | | | | | 8 47 44 | Capt. Cook 8 54 21 | Second Satellite | | | | | 27 10 48 45 | 10 56 15 | First ditto | 20 53 43 | 9 57 28 | | July | | | | | | | 4 | 12 42 40 | 12 51 16 | Ditto | 22 47 33 | 9 56 17 | | | 6 7 09 20 | 7 18 16 | Ditto | 17 16 05 | 9 57 47 | | | 7 09 25 | Capt. Cook 7 18 21 | | | | Eclipse of the Moon. June 18 8 18 5 8 24 18 Beginning of the eclipse 21 52 30 11 58 44 End of the eclipse 11 52 10 11 58 24 Ditto by Capt. Cook 11 55 37 12 1 48 The D clear of the penumbra 11 55 10 12 1 21 Ditto by Capt. Cook. Mean of the seven observations of the first Satellite, rejecting those of the 10th and 12th of May, as too near Jupiter's opposition to the Sun, gives the longitude of Venus's Fort 9° 57' 50" = 149° 27' 30". Add 20" for the correction of the times in the nautical almanack, as found by the observations of March 29 and April 12, at Greenwich, the true longitude will be 9° 58' 10" = 149° 32' 30". Vol. LXI. G g g Transit Transit of Venus by Mr. Green, with a reflecting telescope of 2 feet focus, magnifying power 140 times. | Time per clock | App. time | |----------------|-----------| | | June 2 | | 9 21 45 | 21 25 40 | | Light thus on the O's limb, Tab. XIV. fig. 1. | | 22 00 | 21 25 55 | | Certain, fig. 2. | | 39 20 | 21 43 15 | | First internal contact of O's limb and the O see fig. 4. | | 40 00 | 21 43 55 | | Penumbra and O's limb in contact, see fig. 5. | | | June 3 | | 3 10 05 | 3 14 3 | | First contact of penumbra, undulating, but the thread of light visible and invisible alternately | | 10 53 | 3 14 51 | | Second internal contact of the bodies | | 27 30 | 3 31 28 | | Second external contact | | 28 16 | 3 32 14 | | Total egress of penumbra, O's limb perfect | Transit of Venus by Capt. Cook, with a reflecting telescope of 2 feet focus, and the magnifying power 140. | Time per clock | App. time | |----------------|-----------| | | June 2 | | 9 21 50 | 21 25 45 | | The first visible appearance of O on the O's limb, see fig. 1. | | 39 20 | 21 43 15 | | First internal contact, or the limb of O seemed to coincide with the O's, fig. 2. | | 40 20 | 21 44 15 | | A small thread of light seen below the penumbra, fig. 3. | | | June 3 | | 3 10 15 | 3 14 13 | | Second internal contact of the penumbra, or the thread of light wholly broke | | 10 47 | 3 14 45 | | Second internal contact of the bodies, and appeared as in the first | | 27 24 | 3 31 22 | | Second external contact of the bodies | | 28 04 | 3 32 2 | | Total egress of penumbra, dubious | The first appearance of Venus on the Sun, was certainly only the penumbra, and the contact of the limbs did not happen till several seconds after, and then it appeared as in fig. the 4th; this appearance was observed both by Mr. Green and me; but the time it happened was not noted by either of us; it appeared peared to be very difficult to judge precisely of the times that the internal contacts of the body of Venus happened, by reason of the darkness of the penumbra at the Sun's limb, it being there nearly, if not quite, as dark as the planet. At this time a faint light, much weaker than the rest of the penumbra, appeared to converge towards the point of contact, but did not quite reach it, see fig. 2. This was seen by myself and the two other observers, and was of great assistance to us in judging of the time of the internal contacts of the dark body of Venus, with the Sun's limb. Fig. the 5th, is a representation of the appearance of Venus at the middle of the ingress and egress, for the very same phenomenon was observed at both: at the total ingress, the thread of light made its appearance with an uncertainty of seve- ral seconds; I judged that the penumbra was in contact with the Sun's limb 10" sooner than the time set down above; in like manner at the egress the thread of light was not broke off or diminished at once, but gradually, with the same uncertainty: the time noted was when the thread of light was wholly broke by the penumbra. At the total egress I found it difficult to distinguish Venus's limb from the penumbra; which of course made the second external contact a little doubtful, and the pre- cise time that the penumbra left the Sun could not be observed to any great degree of certainty, at least by me. Some of the other gentlemen, who were sent to observe at different places, saw at the ingress and egress the same phenomenon as we did; though much less distinct, which no doubt was owing to their telescopes being of a less magnifying power; for the penumbra was visible through my telescope during the whole Transit; and Dr. Solander, whose telescope magnified more than ours, saw it, I have reason to think, distincter than either Mr. Green or my- self; though we both of us saw enough to convince our senses, that such a phenomenon did indisputably exist, and we had a good opportunity to observe it, for every wished-for favourable circumstance attended the whole of that day, without one single impediment, excepting the heat, which was intolerable: the thermometer which hung by the clock and was exposed to the sun as we were, was one time as high as 119°. The breadth of the penumbra appeared to me, to be nearly equal to 1/8th of Venus's semidiameter. G g g 2 Transit Transit of Venus by Dr. Solander, with a 3 feet reflecting telescope. | Time per clock | First external contact plainly convex, a wavering haze seen some seconds before ingress, light seen glimmering under Venus | App. time | |----------------|-------------------------------------------------------------------------------------------------|-----------| | 9 22 11 | | 21 43 28 | | 9 39 33 | | 21 44 2 | | 9 40 07 | ?'s free from the ⊙'s limb | 3 31 49 | | 3 27 51 | ?'s true limb out | 3 32 13 | | 3 28 15 | ?'s atmosphere out | | Observations of the Transit of Venus, made by Mr. Charles Green, with Dollond's micrometer fitted to a reflecting telescope of 2 feet focus. June 2 1769. In. pts. ver. | In. pts. ver. ---|--- 0 10 24 | 0 10 5 0 10 24 | 0 10 5 0 10 24 | 0 10 4½ 0 15 0 | 0 10 4 0 10 24 | 0 10 5 0 10 24 | 0 10 4 Mean 0 10 24,14 | Mean 0 10 4,5° Half the difference of these two means is +9,82 ver. = +8,4'' the correction of the adjustment of the micrometer to be added to all observations made on the scale; and half the sum of the two means is 10 pts. 14,31 ver. = 54,97'' Venus's apparent diameter. After the above measurements of Venus' diameter, I fixed my telescope on an equatorial stand, which was screwed down to a large cask filled with sand and water; and by repeated trials a day before, an object (as the sun) would move on along the wire a quarter of an hour without any sensible difference. Thus equipped, I took the following observations, a careful person noting the time by the clock and another writing down. By repeated peated trials some days before, I found the telescope at distinct vision, when it stood at on the scale; therefore I put it to this before I measured Venus's diameter. I read them all off myself and saw each written down. | Time by the clock | Apparent time | Measure by micrometer | D° red.& cor. in min. & sec. | |-------------------|---------------|-----------------------|----------------------------| | H M S | H M S | In. pts. V. | M S | | 22 35 28 | 22 39 24 | 0 50 18 | 3 57,4 | | 22 41 0 | 22 44 56 | 0 50 15 | 3 54,8 | | 22 45 34 | 22 49 30 | 0 50 12 | 3 52,3 | | 22 50 54 | 22 54 50 | 0 50 20 | 3 59,1 | | 22 57 44 | 23 1 40 | 0 50 8 | 3 48,8 | Difference of declination between the North limb of Venus and the North limb of the Sun. Distance of the Eastern limbs of the Sun and Venus in lines parallel to the equator; or rather the translation of Venus, in order to produce an artificial internal contact with the Sun to the East. Distance of the Western limbs of the Sun and Venus in lines parallel to the equator. Difference of declination between the Northern limbs of the Sun and Venus. Difference of declination between the South limb of the Sun and the North limb of Venus. I now took my telescope from the equatorial stand, and placed it on its own proper stand and took the following observations. June 3 1769 | Time | Nearest dist. of O's N. limb from Q's S. limb | Greatest dist. of O's S. limb from Q's N. limb | |------|---------------------------------------------|---------------------------------------------| | 0 2 10 | 0 6 7 0 80 3 5 52,7 | Greatest dist. of O's S. limb from Q's N. limb | | 0 7 53 | 0 11 5 0 75 2 26 51,9 | Nearest dist. of O's N. limb from Q's S. limb | | 0 11 42 | 0 15 39 0 80 2 5 51,8 | Greatest dist. of O's S. limb from Q's N. limb | | 0 14 17 | 0 18 14 3 75 3 26 52,8 | Nearest dist. of O's N. limb from Q's S. limb | | 0 18 19 | 0 22 16 0 80 0 5 50,1 | Greatest dist. of O's S. limb from Q's N. limb | | 0 20 14 | 0 24 11 3 70 16 26 42,5 | Nearest dist. of O's N. limb from Q's S. limb | | 0 23 13 | 0 27 10 0 80 6 5 55,2 | Greatest dist. of O's S. limb from Q's N. limb | | 0 25 28 1/2 | 0 29 25 3 70 18 26 44,2 | Nearest dist. of O's N. limb from Q's S. limb | | 0 27 37 | 0 31 34 0 80 5 5 54,4 | Time | | Time by the clock | Apparent time | Measure by micrometer | D°, red., & cor. in min. & sec. | |-------------------|---------------|----------------------|--------------------------------| | H M S | H M S | In. pts. V | M S | | 0 29 35 | 0 33 32 | 3 70 20 | 26 45,9 | | 0 34 18 | 0 38 15 | 0 80 5 | 5 54,4 | | 0 36 59 | 0 40 50 | 3 70 19 | 26 45,1 | | 0 38 53½ | 0 42 50 | 0 80 3 | 5 52,7 | | 0 40 37 | 0 44 34 | 3 70 24 | 26 49,3 | | 0 42 19 | 0 46 16 | 0 80 4 | 5 53,5 | | 0 44 34 | 0 48 31 | 3 70 23 | 26 48,5 | | 0 46 12 | 0 50 9 | 3 75 0 | 26 50,2 | | 0 48 11 | 0 52 8 | 0 80 0 | 5 50,1 | | 0 58 13 | 1 2 10 | 0 75 15 | 5 41,6 | | 1 0 55 | 1 4 52 | 3 75 10 | 26 58,8 | | 1 3 4 | 1 7 10 | 0 75 9 | 5 36,5 | | 1 5 51 | 1 9 48 | 3 75 15 | 27 3,0 | | 1 8 2½ | 1 12 19 | 0 75 2 | 5 30,5 | | 1 10 47 | 1 14 44 | 3 75 21 | 27 8,2 | | 1 12 34 | 1 16 31 | 0 70 21 | 5 25,4 | | 1 15 57 | 1 19 54 | 3 80 8 | 27 18,3 | | 1 17 12 | 1 21 9 | 0 70 16 | 5 21,1 | | 1 19 34½ | 1 23 32 | 0 70 15 | 5 20,2 | At the last observation I looked at the thermometer which was close by me, and it was 113 degrees high. With my telescope as before, I measured the following horizontal diameters of the Sun and Venus. The Sun’s horizontal diameter: | 4 35 24 | 4 35 24 | 4 40 0 | 4 40 0 | 4 35 24 | 4 35 24 | 4 40 0 | |---------|---------|--------|--------|---------|---------|--------| | Mean | 4 35 24,43 | 31 27,4 | Venus’s diameter measured off the scale: | 0 10 24 | 0 10 23½ | 0 10 24 | 0 10 24 | 0 10 24½ | |---------|----------|---------|---------|-----------| | Mean | 0 10 24 | Venus’s diameter measured on the scale: | 0 10 3 | 0 10 4 | 0 10 4 | 0 10 5 | 0 10 6 | 0 10 3 | |--------|--------|--------|--------|--------|--------| | Mean | 0 10 4,16 | Half Half the difference of these two means, is \(+9.92\) vern. \(= +8.5''\) the correction of the adjustment of the micrometer, which only differs \(\frac{1}{6}\)th of a second from what was found by the measures of Venus's diameter before. Half the sum of the two means is \(10^{\circ} 14.08 = 54.77''\) Venus's apparent diameter, which was found before \(54.97''\). The mean of the two results is \(54.87''\) or \(54.9''\). After the last measurements of the Sun and Venus's diameters, I replaced my telescope on the equatorial stand, and took the following observations. | Time by the clock | Apparent time | Measure by micrometer | D° red. & cor. in min. & sec. | |-------------------|---------------|-----------------------|-------------------------------| | H M S | H M S | In. pts. V | M S | | 1 59 37 | 2 3 35 | 85 21\(\frac{1}{2}\) | 6 29.9 | | 2 6 32 | 2 10 30 | 3 45 | 24 42.0 | | 2 10 44 | 2 14 42 | 95 10 | 7 2.8 | | 2 14 30 | 2 18 28 | 3 25 4 | 23 20.0 | | 2 17 55 | 2 21 53.1 | 0 2 | 7 17.3 | | 2 21 52 | 2 25 33 | 25 1 | 23 17.5 | | 2 24 72 | 2 28 50 | 75 20 | 5 45.9 | | 2 27 54 | 2 31 52.3 | 65 0 | 26 7.4 | Here follows the Table of the value of the scale of the object glass micrometer, which was delivered in by Mr. Short, together with the telescope, by which the reductions of the foregoing observations were made. **Table** for the object glass micrometer; the focal length of which object glass is \(= 482.867\) inches. | Inches | Corresponding angle in min. and sec. | Dec. of the arc | Angle in min. and sec. | Part of the arc | Angle in seconds | |--------|-------------------------------------|-----------------|------------------------|-----------------|------------------| | 1 | 7 7.2 | 0.05 | 0 21.4 | 1 | 0.9 | | 2 | 14 14.3 | 0.10 | 0 42.7 | 2 | 1.7 | | 3 | 21 21.4 | 0.15 | 1 4.1 | 3 | 2.6 | | 4 | 28 28.6 | 0.20 | 1 25.4 | 4 | 3.4 | | 5 | 35 35.8 | 0.25 | 1 46.8 | 5 | 4.3 | | | | | 2 8.1 | 6 | 5.1 | | | | | 2 29.5 | 7 | 6.0 | | | | | 2 50.9 | 8 | 6.8 | | | | | 3 12.2 | 9 | 7.7 | | | | | 3 33.6 | 10 | 8.6 | | | | | 3 54.9 | 11 | 9.4 | | | | | 4 16.3 | 12 | 10.3 | | | | | 4 37.6 | 13 | 11.1 | | | | | 4 59.0 | 14 | 12.0 | | | | | 5 20.4 | 15 | 12.8 | | | | | 5 41.7 | 16 | 13.7 | | | | | 6 3.1 | 17 | 14.5 | | | | | 6 24.4 | 18 | 15.4 | | | | | 6 45.8 | 19 | 16.3 | | | | | 20 | 17.1 | | | | | | 21 | 18.0 | | | | | | 22 | 18.8 | | | | | | 23 | 19.7 | | | | | | 24 | 20.5 | | Observations Observations on the Transit of Venus, June 3, 1769, by Dollond's micrometer fitted to a reflecting telescope of 18 inches focus, by Capt. James Cook. Venus's diameter, soon after the ingress. | Off the scale | On the scale | |---------------|-------------| | In. Dec. Ver. | In. Dec. Ver. | | 0 10 4 | 0 10 4 | | 0 10 3 | 0 10 6 | | 0 10 4 | 0 10 6 | | 0 10 4 | 0 10 5 | | 0 10 3\(\frac{3}{4}\) | 0 10 5\(\frac{1}{4}\) | By these measurements the correction of adjustment of the micrometer —\(0\frac{3}{4}\) of a division of the vernier, and \(q\)’s diameter 10 d. 4\(\frac{1}{2}\) v. = 56,8. June 2 | Time per Gl. | Appar. Time | In. D. V. | M | S | |--------------|-------------|----------|---|---| | 23 3 | 23 6 57 | 3 20 20 28 | 6,6 | | 23 6 46 | 23 10 42 | 3 20 18 28 | 4,6 | | 23 10 8 | 23 14 4 | 3 20 15 28 | 1,4 | | 23 14 36 | 23 18 32 | 3 20 10 27 | 56,2 | | 23 24 36 | 23 28 32 | 0 55 23 | 5 8,8 | | 23 26 38 | 23 30 35 | 0 60 3 | 5 14,0 | | 23 29 38 | 23 33 35 | 0 60 4 | 5 15,1 | | 23 31 54 | 23 35 51 | 0 60 9 | 5 20,3 | Greatest distance of \(q\) and \(o\) in outer contact. Least distance of \(q\) and \(o\) in outer contact. Venus's diameter June 3. | Off the scale | On the scale | |---------------|-------------| | In. D. V. | In. D. V. | | 0 10 2 | 0 10 6 | | 1 | 7 | | 2 | 6 | | 2 | 6 | By these measurements the correction of adjustment is \(-2\frac{1}{2}\) and Venus's diameter 0 10 4 = 56,"'28. Mean 0 10 1\(\frac{3}{4}\) o 10 6\(\frac{1}{4}\) The Sun's horizontal diameter at 0\(^h\) 22'. In. D. V. 3 60 18 16 19 17 The Sun's horizontal diameter at $9^h\ 22'$. | In. D. V. | 16 | 17 | 17 | 20 | 18 | 17 | 20 | 21 | |-----------|----|----|----|----|----|----|----|----| Mean $3\ 60\ 18$ From which subtract $2\frac{1}{4}$ leaves $3\ 60\ 15\frac{3}{4}$ | Time per Cl. | App. Time | Measure by micrometer | In. D. V. | M S | |--------------|------------|-----------------------|----------|-----| | h / " | h / " | In. D. V. | | | | 4 29 | 8 26 | 3 10 11 | 47 | 3,8 | | 7 17 | 11 14 | 3 10 18 | 27 | 11,5| | 8 33 | 12 30 | 3 10 23 | 27 | 16 3| | 14 16 | 18 13 | 3 10 15 | 5 | 25 1| | 15 45 | 19 42 | 3 10 15 | 5 | 25 1| | 16 55 | 20 52 | 3 10 09 | 5 | 18,8| | 25 2 | 29 22 | 3 15 18 | 27 | 37,2| | 27 29 | 31 26 | 3 15 18 | 5 | 2,3 | | 32 15 | 36 13 | 3 20 12 | 127 | 45,5| | 34 12 | 38 10 | 3 20 15 | 4 | 47,7| | 36 5 | 40 3 | 3 20 10 | 27 | 54,9| | 38 19 | 42 1 | 3 20 15 | 28 | 0,1 | | 40 5 | 44 3 | 3 20 15 | 4 | 43,5| | 41 48 | 45 46 | 3 20 21 | 4 | 39,4| | 43 24 | 47 22 | 3 20 22 | 8 | 7,4 | | 46 c | 49 58 | 3 50 15 | 4 | 33,1| Greatest distance of $q$ and $\odot$ in outer contact. Least distance of $q$ and $\odot$ in outer contact. Greatest dist. Least dist. Greatest dist. Least dist. Greatest dist. Least dist. Greatest dist. Least dist. Greatest dist. Least dist. The Sun's diameter at $2^h\ 10'$. $3\ 60\ 18$ $18$ $16\frac{1}{2}$ $17$ $17$ $20$ $16$ Mean $3\ 60\ 17\frac{1}{2}$ from which subtract $3\frac{1}{4}$ leaves $3\ 60\ 13\frac{3}{4}$ Venus's diameter. \[ \begin{array}{cccc} 0 & 10 & 20 & 10 \\ 5 & 24 & 6 & \\ 5 & 24 & 8 & \\ 10 & 0 & 8 & \\ \end{array} \] By these measurements, the correction of adjustment of the micrometer, i.e., \(3\frac{1}{4}\) and Venus's diameter \(10\) D. \(3\frac{1}{4} V. = 56''\),02. The mean of the three separate deductions of Venus's observed diameter, is \(56''\),4. A Table for reducing the foregoing observations deduced from the measures of the Sun's horizontal diameter, supposed \(= 31' 31''\). | Inches | Angle | Decimals of an In. | Angle | Div. of Vern. | Angle | |--------|-------|--------------------|-------|---------------|-------| | 1 | 8 | 41,1 | 0 | 26,1 | 1 | | | | ,05 | | | 1,0 | | 2 | 17 | 22,2 | 0 | 52,1 | 2 | | | | ,10 | | | 2,1 | | 3 | 26 | 3,3 | 1 | 18,2 | 3 | | | | ,15 | | | 3,1 | | | | ,20 | | | 4 | | | | ,25 | | | 4,2 | | | | ,30 | | | 5 | | | | ,35 | | | 5,2 | | | | ,40 | | | 6 | | | | ,45 | | | 6,2 | | | | ,50 | | | 7 | | | | ,55 | | | 7,3 | | | | ,60 | | | 8 | | | | ,65 | | | 8,3 | | | | ,70 | | | 9 | | | | ,75 | | | 9,4 | | | | ,80 | | | 10 | | | | ,85 | | | 10,4 | | | | ,90 | | | 11 | | | | ,95 | | | 11,5 | | | | 1,00 | | | 12 | | | | | | | 12,5 | | | | | | | 13 | | | | | | | 13,5 | | | | | | | 14 | | | | | | | 14,6 | | | | | | | 15 | | | | | | | 15,6 | | | | | | | 16 | | | | | | | 16,7 | | | | | | | 17 | | | | | | | 17,7 | | | | | | | 18 | | | | | | | 18,8 | | | | | | | 19 | | | | | | | 19,8 | | | | | | | 20 | | | | | | | 20,8 | | | | | | | 21 | | | | | | | 21,9 | | | | | | | 22 | | | | | | | 22,9 | | | | | | | 23 | | | | | | | 24 | | | | | | | 24,0 | | | | | | | 25 | | | | | | | 25,0 | | | | | | | 26 | | | | | | | 26,1 | N. B. The observations made by Mr. Green with Dollond's micrometer, particularly those concerning the difference of declination of Venus and the Sun's limbs, and the distances of Venus from the Sun's limb in lines parallel to the equator, will be better understood by consulting a paper intitled Directions for observing the Differences of Declination &c. with Dollond's Micrometer, by N. Maskelyne, Astronomer Royal, a copy of which was given to Mr. Green, before his departure from England; which will appear in this volume. Observations on the Dipping Needle. | Time when | Place where | Dip of the North or South point | |-----------|-------------|--------------------------------| | 1768 | | | | Sept. 13 | In Funchal Bay, dip of N. end of needle | 77° 18' | | October 25| Crossing the line in long. 30° 18' W. of Greenwich | 26° to 28° N. point | | 1769 | | | | January 10| At sea in lat. 52° 54' S. and long. 63° 10' W. | 63° S. point | | 20 | Good Succes Bay in Straits Le Maire | 68° Ditto | | 24 | On board the ship at anchor in the above bay | 65° Ditto | | 30 | At sea in lat. 60° 04' S. long. 74° 10' W. | 65° Ditto | | March 3 | Ditto, ditto, 36° 49' S. ditto 111° 54' W. | 65° Ditto | | 13 | Ditto, ditto, 30° 46' S. ditto 125° 28' W. | 64° Ditto | | April 5 | Ditto, ditto, 18° 25' S. ditto 140° 51' W. | 30° Ditto | N. B. Each of the above Observations is the mean of ten, twelve, or more; with the face of the instrument turned alternately East and West: those made at sea are a little dubious on account of the motion of the ship; but, by means of a swinging table we had made to set the compass upon, we could, in a tolerable smooth sea, be certain of the dip to a degree, or at the most two, by taking the mean of a great number of trials. 1769 May 30 George's Island | Time | Dip | |------|-----| | 29 | 26° South point Face East | | 29 | 40° West | | 30 | 10° East | | 31 | 45° West | | 31 | 00° East | | 31 | 00° West | | 30 | 51° East | | 30 | 40° West | | 30 | 18° East | | 30 | 25° West | | 30 | 21° East | | 30 | 40° West | | 31 | 00° East | | 30 | 42° West | | 30 | 45° East | | 31 | 30° West | | 31 | 50° East | | 30 | 16° West | | 30 | 16° East | | 30 | 48° West | | 31 | 45° East | Mean 30° 43' H h h ? Observations 1770 January 19, in Queen Charlotte's Sound, lat. 41° 5' S. long. 184° 35 W. The dip of the South end of the needle 54° 40'. Observations on the Dipping Needle. May 1 Botany Bay Lat. 34° 00 S. Long. 208° 37 W. | Time | South Point Face | East | West | |------------|------------------|------|------| | 67° 20 | | | | | +6° 40 | | | | | 66° 55 | | | | | 67° 08 | | | | Mean 67° 01 July 18 Endeavour River Lat. 15° 26 S. Long. 214° 48 W. | Time | South Point Face | West | East | |------------|------------------|------|------| | 36° 54 | | | | | 40° | | | | | 35° 14 | | | | | 35° 14 | | | | | 36° 00 | | | | | 00° | | | | Mean 36° James Cook. Observations on the Tides at K. Georges Island. | Day of the month | Time of low water | Time of high water | Height of tides | The moon passes the merid. above the merid. below the horizon | |------------------|-------------------|--------------------|-----------------|---------------------------------------------------------------| | 1769 | H M | H M | Inches | H M | | June | | | | | | 4 | 6 o A.M. | Noon | 9½ | 0 36 P.M. | | 5 | 6 o A.M. | Noon | 8½ | 1 40 P.M. | | 6 | 7 30 A.M. | 1 45 P.M. | 9 | 3 34 P.M. | | 7 | 8 o A.M. | 2 10 P.M. | 8½ | 4 25 P.M. | | 8 | 8 41 A.M. | 3 15 P.M. | 9½ | 5 12 P.M. | | 9 | 8 42 A.M. | 4 o P.M. | 8½ | 5 57 P.M. | | 10 | 5 o P.M. | | | 7 23 P.M. | | 12 | | | | | | 14 | 7 41 A.M. | | | | | 17 | 8 40 A.M. | 1 16 P.M. | 9½ | | | 18 | 8 50 A.M. | 11 40 A.M. | 10 | | | 19 | 8 10 A.M. | 0 15 P.M. | 9 | | | 20 | 8 o A.M. | 0 30 P.M. | | | water stands at 5 inches on mark water stands at 14 inches on mark Observations ### Observations on the Tides at K. George's Island. | Day of the month | Time of low water | Time of high water | Height of tides | The moon passes the merid. above the horizon | The moon passes the merid. below the horizon | |------------------|-------------------|--------------------|-----------------|---------------------------------------------|---------------------------------------------| | **1769** | | | | | | | June | | | | | | | 21 | 7 30 A.M. water at 5 in. | 8 30 A.M. water at 5 in. | 10 15 A.M. | 7 0 A.M. 12½ | 6 19 A.M. 2 4 P.M. | | 22 | | | | 8 0 A.M. 13 | 7 11 A.M. 2 50 P.M. | | 25 | | | | 11 13 A.M. | 5 8 P.M. | | July | | | | | | | 2 | 6 30 A.M. Noon | 3 0 P.M. water at 3 inches | 7 15 A.M. water at 3 inches | 10 0 P.M. water at 13 inches | 10 1 13 P.M. | | 3 | 6 30 A.M. Noon | 3 0 P.M. water at 3 inches | 7 15 A.M. water at 3 inches | 10 0 P.M. water at 13 inches | 10 1 13 P.M. | | 4 | 7 30 A.M. water at 3 inches | 7 30 A.M. water at 3 inches | 7 30 A.M. water at 3 inches | 7 30 A.M. water at 3 inches | 7 30 A.M. water at 3 inches | Hence the mean height of the tides is about 10 inches, and the greatest height scarcely exceeds one foot, in the middle of this wide-extended ocean; which falls far short of what might have been expected from physical principles. The cause of this remarkable difference deserves farther inquiry. The time of high water also appears to precede the moon’s passing the meridian by 45 minutes at a medium, and the time of low water to precede the same, by 6h 31'. But the mean difference of high and low water, should be 6h 12', which subtracted from 6h 31', leaves 0h 19', by which the time of high water should precede the moon’s passing the meridian; the mean of this and 0h 45' is 32', by which the time of high water precedes the moon’s passing the meridian, by a medium of all the observations. The times of high and low water seem to be subject to great irregularity on particular days; no doubt owing to the small rise of the water, and the smallness of its force in consequence, which renders it more liable to be disturbed by the action of the winds and other causes: part of the irregularity may be attributed to the difficulty of observing the time of the flood or ebb, with any degree of certainty. N. M. N. B. The island here named King George’s Island, is called by the natives Ota-heite, by which name it will henceforth be called, the name of K. George’s Island having been given before to another island in lat. 14 S. discovered by Commodore Byron. * Mr. Green having died at sea in the passage home from Batavia, all the astronomical and other observations were partly arranged by Capt. Cook, and partly by the Astronomer Royal, from the original manuscripts, and calculated by the latter.