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II 21

The declination of a fixed star changes so slowly that it may be taken out of the Nautical Almanac by inspection, without any practical error resulting; a Greenwich date, therefore, is clearly unnecessary.

. When the zenith distance and declination are of the same name, the latitude is of that name; when the zenith distance and declination are of different names, the latitude takes the name of the greater.

The stars are inserted in the Nautical Almanac in the order of their Right Ascension, from oh to 24"; it will therefore, very much facilitate the finding of the given star in the Nautical Almanac, to turn, in the first

a Andromeda. instance, to the three pages (325–328 Nautical

Date. Almanac, 1872), and thence obtain the star's Right

R.A. Decl, N. Ascension, which find at the top of one of the pages following 332— 387, Nautical Almanac, 1872), which

ohim

28° 22' will give the star, and the declination will be found

Jan. 1

455-17 62":8 opposite the day in the side column which is nearest

45'04

618 the given day. The degrees (9) and minutes (") are

44.90 60:6 placed at the top of the column (as annexed), and the

31 44.78

592 &c.

&c. seconds (") are ranged below, for the sake of econo

May 10 45-50 49'2 mizing space in the second column below the name

45.80

4999 of the star. If the seconds exceed 60", only take the

46'12 5009 excess of 60" and increase the minutes (') at the top &c. &c.

&o. by 1. Thus, on May tenth, the declination of a Andromedæ is 28° 22' 49" N., and on January 1st, the declination is 28° 23' 3" N., 62".8 being '1' 3", which being added to 28° 22', which stands at the head of the column, gives the declination,

EXAMPLES. Ex. 1. 1872, Dec. 29th, long. 140° W.,

1872, March 12th, long. 10°E. the obs. mer. alt. of the star a Leonis obs. mer. alt. of the star Pollux, bearing (Regulus), bearing South, was 52° 7' 30", North, was 71° 59' 10", index corr. + index corr. - 207", height of eye 15 feet : 1' 15", height of eye 18 feet: required the required the latitude.

latitude. Observed altitude of star 52° 7' 30" Observed altitude of star 71° 59' 10" Index correction 27 Index correction

+ 115

&c.

20

21

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Ex, 2.

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In each of the following examples it is required to find the latitude:

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LONG

STAR.

OBS. ALT.

CORR.

EYE.

27 W.

015 N.

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22

22

91 W.

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68 23

CIVIL, DATE.

1872. 1. Nov. 7th, 90°W. a Andromeda

75° 10' 30" S. to 27" 25ft. 2. Jan, ist, a Aurige (Capella)

54

-I 45

18 3. Aug, 19th, 84 E. a Lyræ (Vega)

50

o 20 N. 4. Dec. 22nd, 82 E. a Persei

51 51 45 N. to 40 26 5. April uth, 142 W. a Virginas (Spica)

63 14 30 S. + 347 6. June roth, 151 E. a Eridani (Achernar) 40 10 25 S. to 55 24 7. Dec. 27th,

(Algenib)
78 16 45 S.

24 8. Nov. 30th, 24 W. a Arietis....

o N. I 38 28 9. Feb. 2nd, 76 E.

a Tauri (Aldebaran) 29 52 10 N. + 5 20 15 10. June 1st, a' Crucis ... 75 10 30 S.

14 11. May 22nd, 178 W. a Hydra

30 28 53 S. 7 38 12. July 17th, a Cygni

20 13 50 N.

18 13. Oct. 17th, 165 E. a Aquilæ (Altair)

60 49 10 N. to 55 17 14. March 2nd,

a Canis Majoris (Sirius) 58 58 50 N. ti 10 15. April 3rd, 11 E. a Bootis (Arcturus) ....

79 49 40 S.

5 25 16. Aug. 7th, a Scorpii (Antares)

68 49 30 S. 17. May ist, 8 E. ao Centauri 18, Oct. 29th, 5W, a Piscis Australis ( Fomalhaut) 70 6 o N. to 55 19. Mar. 31st,

a Pegasi (Markab) ........ 33 20 50 N. + I 20 20. Sept. i1th, 12 W. a Cassiopewe

62 24 50 N. - 7 30 19

97 E,

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II

29 E.

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:

Correct the courses for variation and leeway, and find the course and distance from the given point, and the latitude and longitude in by inspection.

4. 1872, January 1st, in longitude 102° 41' W., the observed meridian altitude of sun's L.L. was 59° 59' 50', bearing South, index error + 50" height of eye 15 feet: required the latitude.

5. In latitude 37° N., the departure made good was 89'2 miles: required the difference of longitude by parallel sailing.

6. Required the course and distance from Toulon to Valencia by Jercator's Sailing Lat. Toulon

Long. Toulon

5° 56' E.
Lat. Valencia

Long. Valencia
HH

43° 8' N. 39 29 N.

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24 W.

ADDITIONAL FOR ONLY MATE. 7. 1872, January 6th, find the times of high water at Cherbourg, A.M. and P.M.*

7a. 1872, January 17th, find A.M. and P.m. tides at A, longitude 50° W., change tide 2h 10m (by Rule LXIV, pages 179 and 180).

76. 1869, Jan. 6th, find A.M. and P.m. tides at Cherbourg (Admiralty Tide Tables.)

8. 1872, January 1st, at 8h 4m A.m, apparent time at ship, in latitude 50° 32' N., longitude 139° 51' W., the sun's magnetic amplitude E. by S. 1S.: required the true amplitude and variation.

9. 1872, January 29th, P.m. at ship, latitude 42° 26' N., observed altitude sun's L.L. 13° 40', index error - 1 14", height of eye 16 feet, time by chronometer 294 61 48m 40%, which was 8m 78 slow for Greenwich mean noon, January 1st, and gaining 6s 3 daily : required the longitude by chronometer.

THE SAME, AS PROPOSED AT LIVERPOOL :1872, January 29th, at about 3' 301 P.M. at ship, latitude 42° 26' N., longitude account 49° 15' W., observed altitude sun's L.L. 13° 40', index corr. 1 14", height of eye 16 feet, when a chronometer showed 6h 48m 40%, which was 8m 78 slow for Greene wich mean noon, January ist, and gaining 683 daily.

ADDITIONAL FOR FIRST MATE. 10. 1872, January 15th, mean time at ship gh 39m 44o A.M., latitude 23° 39' S., longitude 127° 52' W., sun's magnetic azimuth S. 93° E., observed altitude sun's L.L. 55° 8' 30', index error 2' 30", height of eye 12 feet: required the true azimuth and variation.

1872, January 17th, P.M. at ship, latitude by account 36° 2' N., longitude 149° 28' E., observed altitude sun's L.L. South of observer was 32° 54' 15", index error

+ 2'18', height of eye 22 feet, time by watch 11" 59", which had been found to be 20m 248 slow on apparent time at ship, the difference of longitude made to the West, since the error of watch on apparent time at ship was determined, was 39''2: required the latitude by reduction to meridian.

ADDITIONAL FOR MASTER ORDINARY.

II.

12.

1872, January 24th, the observed meridian altitude of the star a Tauri (Aldebaran) was 52° 36' bearing South, index correction — 23", height of eye 20 feet: required the latitude,

13. Correct the following compass courses for deviation, as given at page 138:N.N.W., N., and N.E. by N.

EXAMINATION PAPER.No. II.

FOR SECOND MATE,

1. Multiply 50060 by 800, by common logarithms.

Divide 9999.46 by 67.8, by common logarithms.

2.

Only one method of working Tides is required of candidates-Method I is used at most of the English Ports; at London and Liverpool, Method III, by Admiralty Tide Tables, while at Aberdeen Method II is used.

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4. 1872, February ist, in longitude 78° 14' E., the observed meridian altitude of sun's L.L. was 78° 4' 10", bearing South, index error + 55", height of eye 12 feet: required the latitude.

5. In latitude 47° 30' N., the departure made good was 115'5 miles: required the difference of longitude by parallel sailing.

6. Required the course and distance from St. Helena to Cape Horn, by calculation on Mercator's principle. Latitude St. Helena 15° 55'S.

Longitude St. Helena

5° 44' W. Latitude Cape Horn 55 59 S.

Longitude Cape Horn 67 16 W. ADDITIONAL FOR ONLY MATE, 7. 1872, February 15th: required the times of high water at Aberdeen, A.m.and P.m.

7a. 1872, February 14th: find A.M. and P.m. tides at A, longitude 75° E., change tide 3h 30m apparent time (by Method II).

76. 1869, February 11th: find A.M. and P.m. tides at Filey Bay (Admiralty Tide Tables, by Method III).

8. 1872, February 20th, at 6h 9m P.M. apparent time at ship, latitude 11° 58' S., longitude 179° 42' E., sun's magnetic amplitude W.S.W.: required the variation,

9. 1872, February 10th, A.m. at ship, latitude 50° 48' N., observed altitude sun's L.L. 9° 10' 50”, index correction 3' 20", height of eye 18 feet, time by chronometer Feb. 94 9h 5925, which was 34" 12" fast for mean noon at Greenwich, January 10th, and losing 109.8 daily: required the longitude.

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