108 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



that which is above the horizon is called the upper or visible 

 hemisphere ; that which is below, the lower or invisible 

 hemisphere. When the sun, moon, or stars, descend below 

 this circle, we say they are set ; on the contrary, when they 

 appear above it, we say they have risen. 



On the broad circle, representing the horizon, are marked 

 the thirty-two points of the mariner's compass ; the east, 

 west, north, and south points, are principally to be regard- 

 ed ; these are called cardinal points. 



On the inside of the horizon are two notches for receiving 

 a strong brass circle representing the meridian. 



It is suspended on two pins, at two opposite points of 

 the meridian ; these pins are a continuation of the axis of 

 the sphere both ways, and as the sphere turns round upon 

 them, they are considered as poles, and are called, one the 

 north, the other the south pole. 



The equator is that circle which goes round the sphere 

 exactly in the middle between the two poles. 



The ecliptic is that circle which crosses the equator ob- 

 liquely ; it is divided into twelve parts, each of which consists 

 of thirty degrees. 



The equinoctial colure is the great circle which passes 

 through those two points of the equator that are intersected 

 by the ecliptic. 



The solstitial colure is the other great circle at right 

 angles to the equator. 



There are four lesser circles of the sphere, two tropics, 

 and two polar circles ; these four circles are all parallel to 

 the equator. 



The tropic of Cancer is the parallel which is on the north 

 side of the equator, and 23^ degrees distant therefrom. 



The tropic of Capricorn is situate on the south side of the 

 equator, and also 23 degrees distant therefrom. 



The two polar circles are at the same distance from the 

 two poles that the tropics are from the equator, that is, 

 twenty-three degrees and a half. 



That towards the north pole is called the arctic circle, 

 that towards the south pole, the antarctic circle. 



The point in the heavens which is directly over the head 

 of the spectator, is called the zenith. The point which is 

 directly under his feet, is called the nadir. 



To rectify the Sphere, elevate the pole till the same num- 

 ber of degrees is above the plane of the horizon, as the pole 



