Astronomical Observations Made at the North Cape, for the Royal Society. By Mr. Bayley

XXXVI. Astronomical Observations made at the North Cape, for the Royal Society. By Mr. Bayley. 1769 April 28, 29, and 30, got the observatory and dwelling-house built, and instruments on shore. May 1 Set up an oak plank 4½ inches thick, and 14 inches wide. This plank was set a little more than 2 feet in the ground, and well rammed with earth and stones so that it was very steady and firm; to which I screwed the astronomical clock truly perpendicular (by which means it was independent of the observatory and its shaking by the wind) and set it going nearly with sidereal time. Examine the line of collimation of the quadrant, and found it correct. Examine the clock, and found the pendulum to vibrate 1°½ on each side of nothing. Here follow some corresponding altitudes of the Sun, from which the going of the clock is determined. | Date | Time | Altitude | Limb | Z.D. | |------|------|----------|------|-----| | 5 | 6 | 27 13 | 23 34 37 | Morning | Sun's upper limb | 61,30 | | | 20 | 58 | 6 13 30 | Afternoon | Sun's upper limb | 50,0 | | | 5 | 57 | 0 14 31 | Morning | Sun's upper limb | 57,36 very hazy | | | 42 | 6 | 5 33 32 | Afternoon | Sun's upper limb | 57,36 very hazy | | | 29 | 16 | 0 38 39 | Morning | Sun's lower limb | 61,20 | | | 26 | 24 | 5 16 59 | Afternoon | Sun's lower limb | 61,20 | | | 39 | 20 | 0 49 17 | Morning | Sun's upper limb | 71,20 | | | 16 | 18 | 0 | Afternoon | Sun's upper limb | 71,20 | This day set up a meridian post nearly in the meridian, by help of the quadrant, at about half a mile from the observatory. Examined the pendulum of the clock, and found it to vibrate 1°½ on each side of nothing. | Date | Time | Altitude | Limb | Z.D. | |------|------|----------|------|-----| | 15 | 1 | 9 25 | 18 54 | Morning | Sun's upper limb | 55,40 | | | 9 | 59 | 1 19 46 | Afternoon | Sun's lower limb | 70,5 | | | 48 | 48 | 5 39 0 | Morning | Sun's upper limb | 54,12 | | | 18 | 48 | 21 55 4 | Afternoon | Sun's lower limb | 54,12 | | | 55 | 31 | 2 1 42 | Morning | Sun's upper limb | 54,12 | | | 20 | 1 | 36 21 | Afternoon | Sun's lower limb | 54,12 | | | 37 | 3 | 1 47 16 | Morning | Sun's upper limb | 54,12 | | | 1 | 10 | 5 50 56 | Afternoon | Sun's lower limb | 54,12 | 1769 | Date | Time | Altitude | Z.D. | |------------|---------------|----------|--------------| | 21 June | 6h 2m | 12° 6' | Morning Sun's upper limb 69° 27' | | | 6h 28m | 12° 38' | Morning Sun's lower limb 67° 40' | | | | | | | | | | At 7h 22' per clock, clock stopped, but by what cause I cannot find, it not being down. | | | | | At 9h 15' set it going again, as near as I could guess, with sidereal time. | | | | | Pendulum vibrates 1° 2' on each side of nothing. | | | | | Wound up the clock The pendulum vibrates 1° 2' on each side of nothing. | | | | | | | | | | Morning Sun's upper limb 66° 50' | | | | | Afternoon Sun's lower limb 63° 20' | | | | | Morning Sun's upper limb 61° 54' | | | | | Afternoon Sun's lower limb 58° 42' | | | | | Morning Sun's upper limb 56° 40' | | | | | Afternoon Sun's lower limb 55° 5' | | | | | Morning Sun's upper limb 53° 0' | | | | | Afternoon Sun's lower limb 52° 5' | | | | | Morning Sun's upper limb 50° 50' | | | | | Afternoon Sun's lower limb 47° 29' | | | | | Morning Sun's upper limb 45° 52' | | | | | Afternoon Sun's lower limb 43° 27' | | | | | Morning Sun's upper limb 41° 29' | | | | | Afternoon Sun's lower limb 39° 56' | | | | | Morning Sun's upper limb 37° 58' | | | | | Afternoon Sun's lower limb 35° 24' | | | | | Morning Sun's upper limb 33° 33' | | | | | Afternoon Sun's lower limb 31° 52' | | | | | a mean of four observations Z.D. ⊙ L.L. = 69° 26' 15" | 769 | Date | Time | Altitude | Time | Altitude | Time | Altitude | Time | Altitude | Time | Altitude | Time | Altitude | |------------|------|----------|------|----------|------|----------|------|----------|------|----------|------|----------| | June 9 | 33° 43' | Morning | Sun's upper limb | 65° 32' | | | 46° 18' | Afternoon | Sun's lower limb | 57° 0' | | | 40° 16' | Morning | Sun's lower limb | 66° 44' | | | 39° 45' | Afternoon | Sun's upper limb | 59° 26' | | | 28° 43' | Morning | Sun's lower limb | 57° 48' | | | 8° 51' | Afternoon | Sun's upper limb | 59° 30' | | | 1° 36' | Morning | Sun's lower limb | 57° 30' | | | 8° 43' | Afternoon | Sun's upper limb | 55° 32' | | | 23° 28' | Morning | Sun's lower limb | 64° 36' | | | 10° 56' | Afternoon | Sun's upper limb | 63° 20' | | | 23° 34' | Morning | Sun's lower limb | 55° 25' | | | 0° 0' | Afternoon | Sun's upper limb | 51° 3' | | | 0° 59' | Morning | Sun's lower limb | 50° 54' hazy | | | 9° 28' | Afternoon | Sun's upper limb | 57° 30' | | | 1° 6' | Morning | Sun's lower limb | 64° 36' | | | 9° 21' | Afternoon | Sun's upper limb | 63° 20' | | | 1° 20' | Morning | Sun's lower limb | 55° 25' | | | 9° 7' | Afternoon | Sun's upper limb | 51° 3' | | | 1° 28' | Morning | Sun's lower limb | 50° 54' hazy | | | 6° 47' | Afternoon | Sun's upper limb | 57° 30' | | | 1° 42' | Morning | Sun's lower limb | 64° 36' | | | 9° 27' | Afternoon | Sun's upper limb | 63° 20' | | | 1° 49' | Morning | Sun's lower limb | 55° 25' | | | 9° 20' | Afternoon | Sun's upper limb | 51° 3' | | | 2° 9' | Morning | Sun's lower limb | 50° 54' hazy | | | 9° 0' | Afternoon | Sun's upper limb | 57° 30' | | | 2° 16' | Morning | Sun's lower limb | 64° 36' | | | 9° 0' | Afternoon | Sun's upper limb | 63° 20' | | | 3° 24' | Morning | Sun's lower limb | 55° 25' | | | 4° 5' | Afternoon | Sun's upper limb | 51° 3' | | | 3° 35' | Morning | Sun's lower limb | 50° 54' hazy | | | 4° 23' | Afternoon | Sun's upper limb | 57° 30' | | | 1° 7' | Morning | Sun's lower limb | 64° 36' | | | 1° 11' | Afternoon | Sun's upper limb | 63° 20' | | | 2° 30' | Morning | Sun's lower limb | 55° 25' | | | 1° 40' | Afternoon | Sun's upper limb | 51° 3' | | | 0° 39' | Morning | Sun's lower limb | 50° 54' hazy | | | 0° 0' | Afternoon | Sun's upper limb | 57° 30' | | | 0° 45' | Morning | Sun's lower limb | 64° 36' | | | 1° 48' | Afternoon | Sun's upper limb | 63° 20' | | | 2° 22' | Morning | Sun's lower limb | 55° 25' | | | 9° 12' | Afternoon | Sun's upper limb | 51° 3' | | | 2° 29' | Morning | Sun's lower limb | 50° 54' hazy | | | 1° 54' | Afternoon | Sun's upper limb | 57° 30' | | | 3° 32' | Morning | Sun's lower limb | 64° 36' | | | 8° 2' | Afternoon | Sun's upper limb | 63° 20' | | | 3° 58' | Morning | Sun's lower limb | 55° 25' | | | 1° 27' | Afternoon | Sun's upper limb | 51° 3' | From the above corresponding Altitudes the going of the Clock is determined. | Apparent noon per clock, per equal altitudes | Clock too slow for sidereal time | Rate of clock with respect to sidereal time | |---------------------------------------------|---------------------------------|------------------------------------------| | h | " | h | " | " | " | | May 6 | 2 53 31,0 | 1 1,0 | +4,6 | | 8 | 3 1 25,2 | 0 52,3 | +1,2 | | 15 | 3 28 59,2 | 0 43,2 | -1,3 | | 20 | 3 48 43,9 | 0 49,6 | | June 3 | h | " | h | " | " | |---------------------------------------------|---------------------------------|------------------------------------------| | 4 45 51,1 | 1 13,6 | -0,5 | | 5 9 46,4 | 1 16,6 | +1,3 | | 10 5 13 56,9 | 1 15,3 | +2,1 | | 11 5 18 71,3 | 1 13,2 | -0,2 | | 15 5 34 42,5 | 1 14,0 | +0,07 | | 18 5 47 10,3 | 1 14,2 | | Mean rate of clock +0,91 Clock stopped. TRANSITS taken with a Transit Instrument over the Meridian, on the Island of Maggeræ, or the North Cape of Europe. 1769 May 20 3h 49' 30",7 transit of Sun's center at transit instrument, it being adjusted to the meridian mark, which was put nearly in the meridian. —— And 3h 48' 43",9 apparent noon per equal altitudes. By this it appears, the meridian mark is well of the true meridian. Shifted the meridian mark nearer to the true meridian. June 3 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 1 | 2 | 3 | 4 | 5 | | 43 | 11½ | 44 | 1½ | 47 | 7½ | | 46 | 17 | | | | | | 5 | 10 | 58,6 | | | | | 18 | 28 | 5 | | | | | 19 | 38 | 28+ | | | | | 10 | 48 | 39 | | | | | 12 | 45 | 14 | | | | | 14 | 4 | 6 | | | | | 18 | 28 | 7+ | | | | | 19 | 18 | 7½ | | | | | 20 | 7½ | | | | | | 20 | 55½ | | | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. June 9 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 1 | 2 | 3 | 4 | 5 | | 27 | 8+ | 18 | 28 | 5 | | 43 | 8 | 19 | 38 | 28+ | | 10 | 48 | 39 | | | | 12 | 45 | 14 | | | | 14 | 4 | 6 | | | | 18 | 28 | 7+ | | | | 19 | 18 | 7½ | | | | 20 | 7½ | | | | | 20 | 55½ | | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. June 10 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 1 | 2 | 3 | 4 | 5 | | 47 | 8 | 47 | 54 | | | 10 | 48 | 39 | | | | 12 | 45 | 14 | | | | 14 | 4 | 6 | | | | 18 | 28 | 7+ | | | | 19 | 18 | 7½ | | | | 20 | 7½ | | | | | 20 | 55½ | | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. June 11 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 1 | 2 | 3 | 4 | 5 | | 15 | 24 | 16 | 12+ | | | 5 | 17 | 0½ | | | | 19 | 18 | 7½ | | | | 20 | 7½ | | | | | 20 | 55½ | | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. June 15 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 32 | 46½ | | | | | 5 | 33 | 34½ | | | | 35 | 53+ | | | | | 4 | 19 | 26 | | | | 20 | 15+ | | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. June 16 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 17 | 52+ | 18 | 39 | | | 4 | 19 | 26 | | | | 20 | 15+ | | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. June 17 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 40 | 18 | 41 | 6+ | | | 5 | 41 | 54+ | | | | 44 | 15½ | | | | | 45 | 2½ | | | | | 45 | 50½ | | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. June 18 | Wire | Wire | Wire | Wire | Wire | |------|------|------|------|------| | 44 | 28 | | | | | 47 | 35 | | | | | 12 | 45 | 30 | | | Lyra. Auriga. Polaris S.P. Arcturus. Lyra. Polaris S.P. TRANSITS compared with equal Altitudes, for finding the Error of the Meridian Mark. | Tranits of Sun at transit instrument | Noon per equal altitudes | Differences | |--------------------------------------|--------------------------|-------------| | h' " | h' " | " | | June | | | | 3 | 4 45 9.3 | 4 45 5.1 | 4.2 W. | | 11 | 5 18 9.9 | 5 18 7.3 | 2.6 W. | | 15 | 5 34 43.9 | 5 34 42.5 | 1.4 W. | | 18 | 5 47 13.0 | 5 47 10.3 | 2.7 W. | Mean difference = 2.7 W. e. Hence it appears, that the Sun passed at the transit instrument too late 2", by a mean of these observations, which shews the mark was west of the true meridian; which gives the azimuth of mark = 50" south westerly. TRANSIT of VENUS, observed at the NORTH CAPE. 1769 At 13h 46' 40" per clock, or 9h 0' 2", apparent time, the Sun came out from under a cloud, with Venus on it, about ¼th of her diameter; and at 14h 0' 41" or 9h 14' 1", apparent time, Venus's outer limb seemed to be in contact with the Sun's limb; but no light of that part of the Sun's limb could be seen, Venus being apparently joined to the Sun's limb by a black ligament, which gradually diminished in breadth; and at 14h 1' 36", or 9h 14' 56", the Sun's light broke through it, and Venus and the Sun were to appearance perfect (this was certain to about 10 or 15 seconds of time), and the black ligament contracted itself, so that Venus was considerably within the Sun's limb, suppose ½th of her diameter. During these observations the air was red and hazy, and the Sun's limb very tremulous, and the spots in the Sun very indistinct, and Venus seemed very ill defined when on the Sun. But a better idea will be formed of the bad appearance of Venus at the internal contact, owing to the very hazy state of the air, from the representation of it, plate XIII. Here follow some measures I was able to take during the time the clouds were off the Sun. | Time per clock. | App. time. | Measures of microm. in inches, &c. | Measures of microm. in degrees, &c. | |-----------------|------------|-----------------------------------|-----------------------------------| | 0,1 24 | | | | | 0,1 23 + | | | | | 0,1 23 - | | | | | 0,1 22 + | | | | | 0,1 22 | | | | | 0,1 23 - | | | | | 0,1 24 - | | | | | 0,1 23 | | | | | 0,1 23 - | | | | | Mean of 12 | | | | Soon after the internal contact, measures of Venus's diameter. Measures of the Sun's horizontal and vertical diameters, taken immediately after Venus's diameter. | Horizontal Diameter | Vertical Diameter | |---------------------|-------------------| | 4.9 21 2 | 4.8 12 | | 4.9 23 | 4.8 10 | | 4.9 23 | 4.8 11 | | 4.9 21 2 | 4.8 9 | | Mean 4.9 22 2 | 4.8 10 5 30' 50'' 73 | Difference ### Difference of Declinations of the North Limbs of the Sun and Venus. | Time per clock | App. time | Measures of microm. in inches, &c. | Measures of microm. in degrees, &c. | |----------------|-----------|-----------------------------------|-----------------------------------| | h | h | | | | 14 38 37 | 9 51 50 | 0,51 1 | 3 29,7 | | 44 30 | 57 32 | 0,52 9 | 3 35,8 | | 46 56 | 10 0 | 0,52 13 | 3 38,8 | | 52 45 | 5 56 | 0,52 23 | 3 40,4 | ### Difference of Declination of the South Limbs of the Sun and Venus. | | | | | |----------------|----------|-----------------------------------|-----------------------------------| | 14 54 50 | 10 8 | 1,42 5 | 26 58,6 | | 57 43 | 10 53 | 1,42 0 | 26 54,8 | | 59 32 | 13 2 | 1,42 20 | 26 51,0 | | 15 2 | 15 9 | 1,42 16 | 26 48,0 | ### Equatoreal Distances of the Western Limbs of the Sun and Venus. | | | | | |----------------|----------|-----------------------------------|-----------------------------------| | 15 8 | 10 21 | 3,1 17 | 19 50,8 | | 10 28 | 23 36 | 3,1 2 | 19 39,4 | | 12 15 | 25 23 | 3,02 20 | 19 34,1 | | 13 48 | 26 56 | 3,02 12 | 19 27,9 | ### Equatoreal Distances of the Eastern Limbs of Venus and the Sun. | | | | | |----------------|----------|-----------------------------------|-----------------------------------| | 15 15 | 10 28 | 6,82 8 | 11 49,4 | | 17 38 | 30 45 | 1,82 20 | 11 58,1 | | 19 33 | 32 40 | 1,9 8 | 12 8,0 | | 22 0 | 35 6 | 1,9 19 | 12 16,4 | | 24 5 | 37 11 | 1,92 7 | 12 26,2 | ### Greatest and least Distances of Venus’s nearest Limbs from the Sun’s Limbs, for finding the nearest Distance of their Centers. | | | | | |----------------|----------|-----------------------------------|-----------------------------------| | 15 49 | 11 2 | 0,62 17 | 4 19,9 | | 51 22 | 4 23 | 4,0 2+ 25 21,3 | | | 54 24 | 7 25 | 0,7 7 | 4 31,3 | | 58 1 | 11 1 | 3,92 10 | 25 8,4 | | 16 0 | 40 13 | 3,92 7 | 25 6,1 | | 4 4 | 17 3 | 0,7 23 | 4 43,4 | | 6 24 | 19 22 | 0,72 5 | 4 48,8 | | 9 55 | 23 53 | 3,9 14 | 24 52,5 | | 16 29 | 29 26 | 0,7 12 | 4 35,1 | | 21 31 | 34 27 | 0,7 8 | 4 32,1 | | 16 25 | 55 11 | 3,82 20 | 24 38,0 | ### A Table for reducing the Scale of the micrometer to Degrees, &c. | Inches | Value | Tenths | Value | Vernier | Value | |--------|-------|--------|-------|---------|-------| | 1 | 6 19,95 | 1 | 0 37,99 | 1 0,76 | | 2 | 12 39,91 | 2 | 1 15,99 | 2 1,52 | | 3 | 18 59,86 | 3 | 1 53,98 | 3 2,28 | | 4 | 25 19,81 | 4 | 2 31,98 | 4 3,04 | | 5 | 31 39,77 | 5 | 3 9,97 | 5 3,80 | | 6 | 3 47,97 | 6 | 4 4,56 | 6 4,56 | | 7 | 4 25,97 | 7 | 5 3,27 | 7 5,32 | | 8 | 5 3,96 | 8 | 6 0,88 | 8 6,08 | | 9 | 5 41,96 | 9 | 6 8,48 | 9 6,84 | | 10 | 6 7,66 | | | | | 11 | 8 3,36 | | | | | 12 | 9 1,22 | | | | | 13 | 9 8,88 | | | | | 14 | 10 6,44 | | | | | 15 | 11 4,44 | | | | | 16 | 12 1,12 | | | | | 17 | 12 9,22 | | | | | 18 | 13 6,66 | | | | | 19 | 14 4,44 | | | | | 20 | 15 2,22 | | | | | 21 | 15 9,66 | | | | | 22 | 16 7,22 | | | | | 23 | 17 4,88 | | | | | 24 | 18 2,44 | | | | | 25 | 18 9,99 | | | | On examination, the micrometer scale wanted no adjustment. ECLIPSE of the SUN, observed at the NORTH CAPE. 1769 June 3 At 1h 48' 4", the clouds clearing away, I saw the Sun, and the Moon had made a small impression or notch in the Sun's limb; by observing the increase of the eclipse, I suppose it began 4, 5, or 6 seconds sooner than I first saw it, or at 1h 48" o" per clock, or 20h 59' 19" apparent time, nearly. Distances of the Cusps. | App. time | Measures | Reduced | |-----------|----------|---------| | h ' " | h ' " | | | 2 10 22 | 21 21 0 | 3,7 5 | 23 29,6 | | 13 19 | 24 34 | 3,8 9 | 24 29,6 | | 19 1 | 30 15 | 4,1 6 | 26 21,3 | | 21 3 | 32 16 | 4,2 7 | 26 41,1 | | 23 50 | 35 3 | 4,3 8 | 27 38,8 | | 27 38 | 38 50 | 4,4 14 | 28 21,4 | | 31 10 | 41 21 | 4,5 10 | 28 56,4 | | 34 56 | 46 7 | 4,6 13 | 29 17,7 | | 36 4 | 47 14 | 4,6 15 | 29 38,2 | | 39 11 | 50 21 | 4,7 0 | 29 45,8 | Sun's horizontal Diameter, measured directly after the Eclipse ended. | | | |--------|--------| | 4,9 21 1/2 | | | 4,9 20 | | | 4,9 20 | | | 4,9 22+ | | | 4,9 21- | | Mean 4,9 20,9 = 31' 35",9 Measures of the lucid Part, near the Middle of the Eclipse. | | | |--------|--------| | 2 43 7 | 21 54 16 | | 44 11 | 55 20 | | 47 50 | 58 59 | | 49 35 | 0 43 | | 52 14 | 3 22 | By comparing the end with Mr. Maskelyne's observation at Greenwich, the difference of meridians comes out 1h 44' 6" of time. = 26° 1' 30" east, or difference of longitude of my observatory from Greenwich to the east. From whence the longitude of the point called the North Cape is 25° 49' east of Greenwich. Distances of the Cusps. | | | |--------|--------| | 2 54 55 | 22 6 2 | | 57 1 | 8 8 | | 59 55 | 11 2 | | 3 2 24 | 13 30 | | 4 31 | 15 37 | | 6 37 | 17 42 | | 8 13 | 19 18 | | 10 34 | 21 38 | | 14 57 | 22 26 | Clouds came on, so that I saw the Sun no more till 3h 38' o" per clock, and it broke away very clear, and continued clear to the end, which was at 3h 48' 19" per clock, or 22h 59' 17" apparent time. The air being very clear, the end seemed certain to about two seconds. The telescope used was a reflector of 2 feet focus, made by Mr. Dollond; and the magnifying power, applied for the ingress of Venus, and the beginning and end of the solar eclipse, was 100. The magnifying power used with the micrometer, was 50. Adjustments Adjustments of the telescope with the different eye-pieces and little speculums, as combined together when used. N.B. — shews that (o) on the vernier, is behind, or to the left hand of the first division on the scale; and + to the right hand, or before. Long eye-piece and short focus little speculum magnifying 100 times = - o + 11\(\frac{1}{2}\) on vernier. Long eye-piece and long focus little speculum with micrometer on = - o + 19\(\frac{3}{4}\) on vernier. The eye-piece with moveable wires, and long focus little speculum, and micrometer = + o + 4 on vernier. These are a mean of 10 or 12 observations each. The Value of the Scale of the Object Glass Micrometer was found as follows: A base of 120 feet was carefully measured on level ice (which was covered with frozen snow about half an inch thick), with two 10 feet fir rods; and the measure being taken four different times, no one differed from any of the others so much as \(\frac{1}{10}\)th of an inch. But as the fir rods might not consist of 10 feet exactly of the same standard from which the micrometer scale was laid off, I therefore took six inches between the fine points of a pair of compasses, from the micrometer scale; and, by repeating this measure, found the exact length of the fir rods in measures of the micrometer scale; and thence corrected the length of the base, found immediately by the rods, and reduced to the standard of the micrometer scale. Perpendicularly over the base, at one end, was placed the center of the divided object glass, and perpendicularly over the base, at the other end, a board was placed, having its plane at right angles with the base line, white paper pasted on its upper part; and at the height of the center of the object glass, nearly above the horizon, was a strong black line drawn, as \(AB = 8\) inches, \(Ag\) and \(Ae\) being small but equal distances from \(A\); by bringing \((ed\) and \(gb)\) to coincide alternately with \((Aa)\) the error of adjustment of the micrometer scale was found; and by separating the glasses till \((Aa)\) and \((Bb)\) made but one line; from this separation the value of one extent of the micrometer scale was found, by making this proportion. As the length of the base : is to the length \((AB)\) :: so is 206265" (the number of seconds in an arch equal to the radius of a circle) to a fourth number, which will be the seconds of the angle measured by that opening of the glasses, which is shewn by the micrometer scale; and other angles will be in direct proportion to the respective measures whence the table was formed. **Zenith Distances** taken with an Astronomical Quadrant, of one Foot Radius, made by Mr. Bird, at the North Cape of Europe. | Bar. | Ther. | |------|-------| | Inches | out | in | | Interior arch | Exterior arch | Exterior arch reduced | | 1769 | May 14 | 29° 8' 43" | U.L. on the merid. | 51° 59' 10" | 55° 1' 26" | 15° 51' 58" | 59° 2" | | | June 3 | 29° 9' 36" | L.L. ditto | 51° 10' 40" | 54° 2' 12" | 8° 51' 10" | 45° 9" | | | 11 | 29° 5' 46" | L.L. | 48° 52' 44" | 52° 0' 18" | 6° 48' 52" | 36° 6" | | | 15 | 29° 6' 41" | U.L. | 48° 20' 54" | 51° 2' 9" | 4° 48' 20" | 49° 8" | | | 16 | 29° 7' 44" | L.L. | 47° 35' 37" | 50° 3' 3" | 4° 47' 35" | 40° 3" | | | 17 | 29° 7' 44" | U.L. | 47° 54' 27" | 51° 0' 13" | 4° 47' 54" | 33° 8" | | | 29° 7' 47" | Arcturus | 52° 13' 36" | 55° 2' 27" | 5° 52' 13" | 27° 4" | | | 29° 7' 52" | L.L. | 47° 50' 28" | 51° 0' 4" | 4° 47' 50" | 30° 5" | | | 29° 7' 52" | U.L. | 47° 18' 50" | 50° 1' 26" | 4° 47' 18" | 42° 0" | | | 29° 7' 52" | Lyra | 50° 36' 8" | 53° 3' 30" | 5° 30' 36" | 21° 2" | | | 29° 7' 52" | Center | 91° 1' 12" | 90° 3' 6" | 15° 91' 7" | 19° 4" | | | 29° 7' 52" | L.L. | 32° 25' 18" | 34° 2' 11" | 3° 32' 25" | 22° 0" | | | 29° 7' 52" | Center | 15° 2' 27" | 0° 0" | 1° 26' 55" | 4" | From From the foregoing Zenith Distances of the Sun, and of Arcturus, and α Lyrae, the Latitude of the Observatory is determined, as follows: | From | Latitude | |------|----------| | U. L. | 71° 43.2' | | L. L. | 71° 0.1' | | Center | 71° 43.5' | | Center | 71° 39.8' | | Center | 71° 39.7' | | Center | 71° 40.6' | | Arcturus | 71° 0.9' | | α Lyrae | 71° 48.6' | Mean ———— 71° 47.0' From whence the latitude of the point of land called the North Cape is 71° 10' north. By a great many trials with a very good compass, of Dr. Knight's construction, I found the variation to be 6 degrees west; and by a dipping needle, I found, by repeated trials, the dip of the north end of the needle to be 79 degrees. May 15, at 13h ¼ P. M. apparent time, or 1h 7' after high water, by a mean of 7 observations, I found the dip of the horizon of the sea, from the observatory, to be 12° 18'. Height of the barometer 29.70 inches; thermometer, without, 24°; thermometer, within, 28°. And May 20, at 7h ¾ P. M. apparent time, or 9h 33' after high water, from a mean of 8 observations, I found the dip = 12° 25',; barometer 29.70 inches; thermometer, without, 43°, and, within, 40°. Both these observations were made on the N. N. E. point of the true compass. During each of these observations the water was very smooth, and the horizon clear.—I found it was high water, at the full and change of the Moon, at 3h 44' P. M. apparent time, at the Cape; and, by a series of observations, I found the water to rise 8 feet 1 inch, nearly, perpendicular at the spring tides; and at neap tides 6 feet 8 inches, perpendicular; and the tides seemed to follow very regular, as they ought to do when not disturbed by bad weather ——June 8, I found the height of the observatory 140 feet 6 inches above low water mark. A JOURNAL of the Barometer and two Thermometers, during the Time I was on Shore in the Island of MAGGEROE, or NORTH CAPE, viz. from the 1st of May to the 21st of June. At noon. | Bar. | Ther. | |------|-------| | out | in | | Inches | ° | | 1769 | | | May 1 | 29.72 | 19 | 24 | | 2 | 29.68 | 26 | 28 | | 3 | 29.90 | 18 | 22 | | 4 | 29.96 | 28 | 31½ | | 5 | 29.92 | 34 | 32 | | 6 | 29.91 | 58 | 33 | | 7 | 29.74 | 60 | 40 | | 8 | 29.84 | 56 | 39 | At noon. | Bar. | Ther. | |------|-------| | out | in | At midnight. | Bar. | Ther. | |------|-------| | out | in doors | | Inches | Inches | |--------|--------| | | | The thermometers were kept, the one in the observatory, and the other without, in the open air; but always in the shade; and were always observed at noon and midnight, after the 10th of May; but before, only at noon. The Instruments used at the NORTH CAPE, by Mr. BAYLY, were as follows: A quadrant of 1 foot radius, and two thermometers, made by Mr. Bird. A 2 feet reflector, with an achromatic object glass micrometer, by Mr. Dollond. A transit instrument, of 4 feet, made by Mr. Bird; with an achromatic object glass, by Mr. Dollond. A barometer, by Mr. Ramden. An astronomical clock with a gridiron pendulum, a journeyman clock, and an alarum clock, by Mr. Shelton. A dipping needle, belonging to the Royal Observatory, made by Mr. Graham. A like set, exclusive of a dipping needle, was used by Mr. Dixon, at the island of Hammerfest. N. B. The adjoining chart, and views of the sea-coast and islands, near the North Cape of Europe, Tab. XIV. were drawn from the joint observations of Messieurs Dixon and Bayly. A CHART of the SEA COAST and SANDS near the North Cape of Europe by JERE. DIXON and Wm. BAYLY 1769.