cension of the star from Table IV. or from any catalogue of the stars.

2. Subtract the sun's right ascension from that of the given star (both being expressed in time), and the remainder will be the time of the star's coming to the meridian.

If the right ascension of the sun be greater than that of the star, add to it 24 before you begin to subtract; and the remainder, if less than 12, is the time of the star's coming to the meridian in the afternoon: if the remainder be greater than 12, take 12 away, and the last remainder is the time of the star's coming to the meridian in the morning.

EXAMPLES.

At what hours do the following stars come to the meridian on Feb. 9th?

1. Lyra?

2. Aldebaran?

3. Arcturus?

4. Capella?

5. Sirius?

6. Regulus?

Answ. 9h. 1m. a. m.

Answ. 6 55 p. m.

7. Castor?

8. Fomalhaut?

9. Markab?

10. Atair?

The first of the above examples performed without the globe.

The sun's right ascension, on Feb. 9th, is 21 hrs. 29 min.; the right ascension of Lyra is 18 hrs. 30 min.: to the last add 24, and from the Sum, 42 hrs. 30 min., subtract 21 hrs. 29 min.: the remainder is 21 hrs. 1 min. From this remainder take away 12, and there is left 9 hrs. 1 min.; which is the time of the star's coming to the meridian in the morning. 18 hrs. 30 m. star's right ascension.

Required at what time the following stars come to the meridian on the respective days.

11. Regulus,

October 24.

At what hour does Alphard (Hydra's Heart) come to

the meridian on the following days?

At what hours do the following stars come to the meri

dian on the undermentioned days?

To find on what day of the year any star passes the meridian

at any given hour.

BY THE GLOBE.

1. Bring the given star to the meridian, and set the index to the given hour.

2. Turn the globe till the index point to 12 at noon; and the day of the month, corresponding to the degree of

the ecliptic then under the meridian, will be the day required.

WITHOUT THE GLOBE.

1. If the star come to the meridian in the morning, add the time that it wants to noon to the right ascension of the star, and the sum will be the right ascension of the sun on the required day.

2. If the star come to the meridian in the evening, subtract the time from noon from the star's right ascension, and the remainder will be the sun's right ascension.

3. The day of the month, answering to this right ascension, may be found from Table III.

If, in adding, the sum is more than 24 hours, or 360°, subtract from it 24 hours, or 360°, and the remainder will be the sun's right ascension.

If, when you have to subtract, the right ascension of the star is less than the time from noon, add to it 24 hours, or 360°, before subtracting.

EXAMPLES.

1. On what day does Algenib, in Perseus, come to the meridian at midnight? Answ. Nov. 13th. 2. On what day does Spica Virginis come to the meridian at half past nine in the evening? Answ. May 18th.

The first of these examples performed without the globe. 10m. right ascension of Algenib. O time from noon.

3h. Add 12

The sun's longitude answering to this R, A. in Table III. is November 13.

On what days do the following stars come to the meri.

On what days do the following stars come to the meri

dian at nine o'clock in the evening?

Required the days on which the following stars come to

the meridian, at five o'clock in the morning.

On what days do the following stars come to the meridian, at ten o'clock in the evening?

On what days does Arcturus come to the meridian, at

the following hours?

The examples in this problem may be proved by the last.

PROBLEM VI.

The latitude, hour of the night, and day of the month, being given, to find the altitude and azimuth of any star.

1. Elevate the globe for the given latitude, bring the sun's place to the meridian, and set the index to 12.

2. Turn the globe till the index point to the given hour? 3. Fix the quadrant of altitude on the zenith, and bring it over the star; then the degree upon the quadrant cut by the star will be its altitude, and the distance between the foot of the quadrant and the north or south points of the horizon will be the azimuth.

EXAMPLES.

1. Required the altitude and azimuth of Cor Leonis, at London, on May 11th, at 11 o'clock p. m.

Answ. Alt. 26° 50'.

Az. S. 76 80 W.

2. Required the altitude and azimuth of Capella, at Rome, on December 2d, at 5 in the morning.

Answ. Alt. 42°.

Az. N. 60 W.

What are the altitude and azimuth of the following stars, at Newcastle, October 6th, at the following hours?

3. Arided, Midnight?

4. Capella, 8 p. m.?

5. Castor, 10 p. m.?

7. Menkar, 11 p. m.?
?

8. Atair, 9 p. m.

9. Vega, 9 p. m.?

6. Algenib («, Perseus), 8p.m.? 10. Arcturus, 7 p. m.?

Required the altitude and azimuth of the following stars,

at London, December 21st, at 4 in the morning.

11. Spica Virginis.

12. Sirius.