System of the Universe. 267 



circle is an arch of the secondary to the great circle passing 

 through the body and intercepted between it and the great 

 circle. 



Altitude is the angular distance of a heavenly body 

 from the horizon. The meridian altitude of the sun is the 

 height of it from the horizon at twelve o'clock. 



Declination is the angular distance of any heavenly body 

 from the equinoctial or equator, and is called north or 

 south, according to the side of the equinoctial on which 

 the declination is. 



Right ascension is an arch of the equinoctial contained 

 between the first of aries <Y and the point of it that is cut 

 by a secondary to the equinoctial passing through the hea-r 

 venly body. 



Oblique ascension is that arch of the equinoctial which 

 is contained between the first of aries and the point of the 

 equinoctial which is cut by the horizon at the rising of the 

 heavenly body. 



Ascensional difference is the difference of degrees between 

 the right and oblique ascension, which converted into time, 

 by allowing fifteen degrees for every hour, shows how 

 much the sun or star rises or sets before or after six ; that 

 is, subtract the less from the greater number, and the re- 

 mainder will give the ascensional difference. 



Amplitude is an arch of the horizon contained between 

 the true east or west points and that point of the horizon 

 where the heavenly body rises or sets, and is called north 

 or south amplitude accordingly. 



Azimuth is an arch of the horizon intercepted between 

 the north or south points and that point of the horizon to 

 which the heavenly body is referred by a secondary passing 

 through it. 



Almacanthers are less circles parallel to the horizon. 



The latitude of a heavenly body, is its angular distance 

 from the ecliptic, and is called north or south latitude ac- 



N2 



