for the moon's place, by White's, or any other Ephemeris, for four or five days before and after the full moon; and put a patch on each of these places. Bring the sun's place, for each day, to the brazen meridian, and set the index to twelve at noon; turn the globe westward till the moon's place, corresponding to that day, comes above the horizon, and the index will show the time of rising.

Ex. 1

Thus the difference of the time of the rising of the moon, two or three days before and after full in September, was about sixteen minutes only.

USE OF THE CELESTIAL GLOBE.

114. The Celestial Globe is an artificial representation of the heavens, having the fixed stars drawn upon it in their natural order and situation. The eye is supposed to be placed in the centre ; and if a hole were made in the places of the stars, the real stars in the heavens would be seen through those holes.

115. As the terrestrial globe, by turning on its axis, represents the real diurnal motion of the earth; so the celestial globe, by turning on its axis, represents the apparent motion of the heavens.

116. The zodiac is an imaginary belt around the heavens, of about sixteen degrees broad, in which the planets move. Through the middle of it runs the ecliptic, or the apparent path of the sun.

The twelve signs of the zodiac, which belong to the celestial globe, have been already enumerated. *

117. The first point of Aries and Libra are called the equinoctial points; because, when the sun ap

* See page 100.

pears to be in either of them, the day and night are equal.

118. The first points of Cancer and Capricorn are called solstitial points; because, when the sun is near either of them, he seems to stand still, or to be at the same height in the heavens at twelve o'clock at noon, for several days together.

119. Definition 1.-The latitude of the heavenly bodies is measured from the ecliptic, north and south. The sun, being always in the ecliptic, has no latitude.

120. Definition 2.-The longitude of the heavenly bodies is reckoned on the ecliptic, from the first point of Aries, eastward round the globe. The longitude of the sun is called the sun's place in the ecliptic.

PROBLEM I. To find the latitude and longitude of any star.*

Rule. Put the centre of the quadrant of altitude on the pole of the ecliptic, and its graduated edge on the star; then the arch of the quadrant, intercepted between the star and the ecliptic, shows its latitude and the degree which the edge of the quadrant cuts, on the ecliptic, is the degree of its longitude.

Ex.

- Thus the latitude of Regulus is 0° 28′ N. and its longitude nearly 147°. The latitude of Arcturus is 31° N. nearly its longitude is about 201°.

:

Examples for Practice.

107. What are the latitude and longitude of Cor Caroli? of Aldebaran? and, of B in Perseus?

* The latitude and longitude of the planets and moon are given in White's Ephemeris, in the Nautical Almanack, &c.

108. What are the latitudes and longitudes of Canis Minor? of Canis Major? of Capella? and, of the bright star in the Northern Crown?

PROBLEM II. To find any place in the heavens by having its latitude and longitude given.

Rule. Fix the quadrant of altitude, as in the last problem, letting it cut the longitude given on the ecliptic; then seek the latitude on the quadrant, and the place under it is the place sought.

Ex.

Thus, if I am asked what part of the heavens that is, whose longitude is 60° 30′ and latitude 5° 30′ south, I find it is the place which Aldebaran occupies.

Examples for Practice.

109. What star is that whose longitude is 85°, and whose latitude is 16°, south?

110. What star is that whose longitude is 2002, and whose latitude is 20, south?

111. If a comet appears in that part of the heavens whose longitude is 125°, and latitude 64°, to what constellation must I look for it?

PROBLEM III. To find the declination of the sun and stars.

Def. The declination of any heavenly body is measured upon the meridian from the equator. Rule.- Bring the sun or star to the brazen meridian, and then its distance, in degrees from the equator, is its declination.

Ex. north.

Thus, the sun's declination, April 19, is 11° 19' On the 1st of December it is 21° 54' south.

Examples for Practice.

112. What is the declination of the sun on the 18th of February, and on the 15th of May?

113. What is the declination of the sun on the 11th of August, and on the 21st of September?

114. What is the declination of the sun on the 10th of November, and on the 21st of December?

115. What is the declination of ß in Draco, and of the Pole Star?

116. What is the declination of a in Libra, and of y in the Dragon's Head?

PROBLEM IV. To find the right ascension of the sun, or of any star.

Def. The right ascension of any heavenly body, is its distance from the first meridian, (or that which passes through the first point of Aries,) counted on the equator.

Rule. Bring the sun's place, or that of the star, to the brazen meridian; and the number of degrees on the equator, between that meridian and the first point of Aries, is the right ascension.

Ex. Thus, the sun's right ascension on April 19th is 27° 30'; on the 1st of December 247° 30'.

Examples for Practice.

117. What is the sun's right ascension on the 15th of January, and on the 18th of March?

118. What is the sun's right ascension on the 24th of May, 16th of September, and 19th of December?

119. What is the right ascension of the star ẞ in Auriga's shoulder?

120. What is the right ascension of Dubhe on the back of the Great Bear?

121. What is the right ascension of the Bull's eye?

122. What is the right ascension of Rigel in Orion's foot? 123. What is the right ascension of ẞ in the Northern Scale?

PROBLEM V.-The latitude of the place, the day and hour being given, to represent the face of the heavens at that time, by the celestial globe, so as to find and point out all the constellations, and principal stars, there visible.

Rule.

Elevate the globe to so many degrees

1

above the horizon, as are equal to the latitude of the place, and set the globe due north and south; find the sun's place in the ecliptic, bring it to the orazen meridian, and set the index to twelve at noon; turn the globe westward till the index points to the given hour; then the surface of the globe represents the exact face of the heavens at the given place.

Examples for Practice.

124. Let the learner now represent the face of the heavens for six and ten o'clock in the evening of the 5th of November. 125. For nine and twelve at night of the 10th of May. 126. For the same hours on the 19th of October.

PROBLEM VI. To find the time when any of the heavenly bodies rise, set, or come to the meridian. Rule. Rectify the globe to the latitude of the place; bring the sun's place in the ecliptic to the meridian, and set the index to XII. Then turn the globe till the given body comes to the eastern part of the horizon, and the index shows the time of its rising. Bring the body to the meridian, and the index shows the time of its coming to it. Bring the body to the western horizon, and the index shows the time of its setting. Thus the time of the sun's rising and setting may be found. Turn the globe about its axis: all those stars which do not descend below the horizon, never set at that place; and those which do not ascend above it, never rise there.

Examples for Practice.

127. At what time does the sun rise and set on the 10th of May?