is to tell the height of the sun or stars, and when they are due east or west; also the distance of the stars from one another, and the distance of one place from another.

An Explanation of some terms pertaining to the Celestial Globe..

Declination is the distance of the sun, or any stars, from the equator, in degrees; and is called North or South, according to which side of the equator the sun or star is on.

Right Ascension is the distance from Aries (in hours or degrees, on the equator; reckoned according to the order of the signs) to the brazen meridian, when the sun or stars is brought to the meridian.

Oblique Ascension is the distance from Aries (in hours or degrees, reckoned as above) to the horizon, when the sun or star rises.

Oblique Descension is just the reverse.

Amplitude is the distance in degrees, the sun or star is from the east or west points of the horizon, when rising or setting; and is either North or South.

Altitude is the number of degrees the sun or any star is above the horizon. And Zenith Distance is the altitude taken from 90 degrees; or it is the sun's or a star's distance, in degrees, from the zenith.

Azimuth, or vertical circles, pass through the zenith and nadir, and cut the horizon at right angles. Azimuth is the point of the compass the sun or stars bears on; or it is the

number

number of degrees of the horizon the sun or star's vertical circle is from the meridian.

Almicanters are circles which run parallel to the horizon, whose poles are the Zenith and Nadir.

Latitude of a star is its distance, in degrees. from the ecliptic.

Longitude of a celestial object is its place in the ecliptic, reckoned according to the order of the signs.

The sun has longitude, but no latitude; for his apparent place is always on the ecliptic.

Problems to be solved by the Globes.
PROBLEM I.

The Longitude and Latitude of a place being given, to find it upon the Terrefirial Globe.

Bring the degrees of longitude found on the equator to the meridian; then, under the degree of latitude, on the brass meridian, is the place required. Thus, suppose an American ship falls in with a French vessel in 36 deg. north latitude, and 32 deg. longitude west from London; you will find it to be in the middle of the Atlantic ocean, a little south of the Azore isles.

PROBLEM II.

To find the Latitude of any Place.

Bring the place to the graduated side of the brass meridian, and the figure that stands

D

over

over it shews its latitude or distance from the equator. Thus, the latitude of London is 514 deg. north, Jerusalem is 32 deg. north, and the Cape of Good Hope, 34; deg. south

PROBLEM III.

To find the Longitude of any Place.

Bring the place to the brass meridian; then observe the degree the meridian cuts on the equator, and that is its longitude, or distance in degrees either eastward or westward, from the first meridian: which, in some globes, begins at Faro, in others at Teneriffe; but on the new ones, at London. Thus, the longitude of Mecca, in Arabia, is 434 degrees east; and the longitude of Port Royal, in Jamaica, is 77 degrees west from London.

PROBLEM IV.

To Rectify either Globe; i. e. to place it in fuch a particular situation as is necessary for the solution of many of the following Problems.

Having turned the graduated side of the meridian towards you, move it higher or lower till the pole stands as many degrees above the horizon, as the latitude of the place is you would rectify for. Thus, if the place be London, you must raise the pole 51 degrees (because that it is the latitude of it) which brings that city to the top, or zenith, of the globe, and over the centre of the ho

rizon;

izon; then turn the north pole of the instrument to the north part of the world, which may be done by means of a little compass, and the globe will present the natural situa tion of the earth itself.

Note, In all problems relating to north latitude, you must elevate the north pole; but in those that have south latitude, you must raise the south pole. The north pole must always incline to that part of the horizon marked December. We are to conceive ourselves on the surface of the terrestrial globe, but at the centre of the celestial, when we are solving problems.

· PROBLEM V.

To find the Sun's Place in the Ecliptic on a given day.

Look for the day of the month in the calen der upon the horizon, and opposite to it you will find the sign and degree the sun is in that day. Thus, on the 25th of March, the sun's place is 4 degrees in Aries. Then look for that sign and degree upon the ecliptic liné marked on the globe, and there fix on a small patch. Then the globe will be prepared for the solution of the following problems.

Note, The earth's place is always in the sign and degree opposite the sun's: thus, when the sun is 4 deg. in Aries, the earth is 4 deg. in Libra ; and so on of any other.

PROELEM

PROBLEM VI.

To find the Sun's Declination, having his place in the Ecliptic given.

Bring his place to the edge of the meridian, observe what degree of the meridian lies over it, and that is his declination. Thus, on the 20th of April, the sun has 11 1-2 deg. north declination; but on the 20th of October he has 12 1-2 deg. south declination.

PROBLEM VII.

To find where the Sun is Vertical at any given

Time.

Having noted the sun's declination, bring the place at which the time is known to the meridian, and set the index to the given time, then turn the globe till the index points to XII at noon, and the place which stands under the point of the sun's declination on the meridian, has the sun that moment in the zenith.

All those places which pass under the point of declination when the globe turns on its axis, have the sun vertical on the given day. The sun is never vertical to any place out of the torrid zone.

PROBLEM