rising; to those just above the eastern horizon the sun is about to set; to all those under the upper half of the brazen meridian it is noon, and to all those under the lower half it is midnight.

PROBLEM XIV.-To find all the places to which a lunar eclipse is visible at any instant.

Find the place to which the sun is vertical at that time, and bring that place to the zenith, and set the index to the upper twelve, then turn the globe till the index point to the lower twelve, and the eclipse is visible to every part of the earth that is now above the horizon.

OF THE CELESTIAL GLOBE.

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.

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.

The Zodiac is an imaginary belt round the heavens, of about sixteen degrees broad; through the middle of which runs the ecliptic or the apparent path of the sun.

Note. The twelve signs of the Zodiac which belong to the celestial globe have been already enumerated.

Equinoctial points are the first points of Aries and Libra, so called, because when the sun appears to be in either of them, the days and nights are equal.

Solstitial points are the first points of Cancer and Capricorn; so called because when the sun arrives at 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.

Declination on the celestial globe is the same as latitude on the terrestrial; being the distance of a star from the equinoctial, either north or south.

Right Ascension of a star is its distance from the first meridian, (or that which passes through the first point of Aries) counted in degrees, on the equinoctial quite round the globe.

Latitude of a star is its distance from the ecliptic, either north or south, counted in degrees of the quadrant of altitude. The sun being always in the ecliptic, has no latitude.

Longitude of a star is counted on the ecliptic, in degrees, or in signs and degrees, from the beginning of Aries eastward round the globe.

Degrees

of Latitude.

Shewing the number of miles contained in a Degree of Longitude, in each Parallel of Latitude, from the Equator to the Poles.