PAPER XI. FOR SECOND MATE. (1) Multiply 1008 by 4, by common logs. (2) Divide 982 by 126, by common logs. (3) 7519 5 N by WW 4 9 N.E. E. Allow 1 mile per (4) 1864, February 27th, in longitude 30° W., the observed 5′ 25′′, height of the eye 15 feet. (5) In latitude 36° 55', the departure made good was 102 miles. Required the d.long. by parallel sailing. ADDITIONAL FOR ONLY MATE. (6) 1864, June 11th. Required the A. M. and P. M. tides at Cork. (7) Required the course and distance, by Mercator's sailing, from A to B. A-Lat. 43° 27' N. A-Long. 22° 10′ W. (8) 1864, July 3rd, at 4h. 50m. A. M. apparent time at ship, in latitude 41° 10′ N., longitude 116° 25′ W., the Sun's magnetic amplitude was E. 13° 12′ N. Required the true amplitude and variation. (9) 1864, July 5th, P. M. at ship, in latitude 43° 19′ N., the observed altitude of the Sun's 1. 1. was 40° 37′ 37′′, index error 2′ 4′′, height of the eye 23 feet, time by chronometer 4d. 17h. 45m. 46s., which was fast for mean noon at Greenwich, 7m. 30s., on June 18th, and losing daily 4s.5. Required the longitude by chronometer. ADDITIONAL FOR FIRST MATE. (10) 1864, March 21st, mean time at ship 9h. 14m. A. M., in latitude 34° 19′ S., longitude 58° 20′ W., the observed altitude of the Sun's 1. 1. was 40° 47', index error 1' 20", height of the eye 25 feet, the Sun's bearing by compass N. 38° 55′ E. Required the variation. (11) 1864, November 11th, A. M. at ship, in latitude by account 35° 15′ N., longitude 152° 30′ W., the observed altitude of the Sun's 1. 1. South of the observer was 36° 45′ 15′′, height of the eye 24 feet, time by watch 10d. 23h. 16m., which had been found 21m. 10s.5 slow on apparent time at ship, but since the error was determined the ship has made 18 miles d.long. to the E. Required the latitude by reduction to the meridian. ADDITIONAL FOR MASTER. (12) 1864, March 2nd, the observed meridian altitude of the star Vega was 68° 13′ 15′′, bearing N., index error + 2′ 10′′, height of the eye 13 feet. Required the latitude. PAPER XII. FOR SECOND MATE. (1) Multiply 169 by 57, by common logs. (2) Divide 4086 by 72, by common logs. (4) 1864, November 24th, in longitude 61° 25′ E., the observed meridian altitude of the Sun's 1. 1. was 58° 32′ 50′′, bearing N., index error 2′ 40′′, height of the eye 19 feet. (5) In latitude 49° 35', the departure made good was 64 miles. Required the d.long. by parallel sailing. ADDITIONAL FOR ONLY MATE. (6) 1864, June 21st. the Eddystone. Required the A. M. and P. M. tides at (7) Required the course and distance from Constantinople to Odessa, by calculation on Mercator's principle. Lat. of Constantinople, 41° 0' N....Long. 28° 59′ E. (8) 1864, December 20th, at 5h. 24m. 32s. A.M. apparent time at ship, in latitude 26° 34' S., longitude 75° 38′ W., the Sun's magnetic amplitude was E. 13° 53′ S. Required the true amplitude and variation. (9) 1864, August 20th, A. M. at ship, in latitude 19° 36′ N., the observed altitude of the Sun's 1. 1. was 63° 5' 40", index error 2′ 50′′, height of the eye 16 feet, time by chronometer 20d. 6h. 59m. 44s., which was fast for mean noon at Greenwich 21m. 39s., on May 14th, and losing daily 2s.5. Required the longitude by chronometer. ADDITIONAL FOR FIRST MATE. (10) 1864, December 8th, at 2h. 31m. P. M. mean time at ship, in latitude 22° 35′ S., longitude 56° 47′ E., the observed altitude of the Sun's 1. 1. was 32° 14′ 40′′, index error +1'15", height of the eye 22 feet, bearing by compass N. 84° 38′ W. Required the variation. (11) 1864, October 29th, P. M. at ship, in latitude by account 11° 57′ N., longitude 97° 42′ W., the observed altitude of the Sun's 1.1. South of the observer was 62° 31′ 50′′, index error 6′ 50′′, height of the eye 16 feet, time by watch Oh. 15m. 45s., which had been found to be 56m. 22s. fast on apparent time at ship, the difference of longitude made to the W. was 17 miles since the error was determined. Required the latitude by reduction to the meridian. ADDITIONAL FOR MASTER. (12) 1864, November 16th, the observed altitude of Altair was 75° 16′ 30′′, bearing N., index error height of the eye 15 feet. Required the latitude. H the star - 3' 20", SEXTANTS AND QUADRANTS. Sextants are divided on the Arch either into 10, 15, or 20 minutes, which may be known by the number of divisions in the degree, or by the number of minutes or miles marked on the vernier at the bottom. (In reading the Sextant, either on or off the Arch, care should be taken that the reading commences from the position of the arrow or nonius.) To find the Index Error, place the arrow or nonius on the vernier to 0 on the Arch, and then if the true and reflected Suns exactly cover each other, there is no Index Error; if they do not, put the vernier so that it reads about 40 minutes on the Arch; then make the edges of the true and reflected Suns touch each other; read it and note it down; then put 40 minutes off the arc, and make their other edges touch; read it and note it down as before; the half-difference between these two readings will be the Index Error; to be subtracted if on is greatest, and additive if off is greatest. To tell if your observations are right, add the two readings together and divide by 4, which will give the Sun's semidiameter in the Nautical Almanac for the day; if not, you must repeat the observations. ADJUSTMENTS. 1st. To set the plane of the Index-glass perpendicular to the plane of the Instrument. Place the arrow or nonius near to the middle of the Arch, and holding the eye close to the Index-glass, look aslant into the glass, and observe the part of the Arch towards the right, and also its reflection towards the left. If they are in one line, the glass is perpendicular; if not, it must be adjusted by the screws at the back of the Index-glass. 2nd. To set the plane of the Horizon-glass perpendicular to the plane of the Instrument. Bring the arrow or nonius to 0 on the Arch, and, holding the Quadrant horizontally, observe whether the real and reflected horizons coincide; if so, the glass is perpendicular; if not, the horizons must be made to coincide by means of the screws at the back of the Horizon-glass. |