Dr. Maskelyne's formula for finding the longitude, &c. 145 
2. If B be equal to 90°, the right ascension is = 0 , if the 
longitude is in the first or fourth quadrant; but if the longi- 
tude is in the second or third, the right ascension is 180°. 
3. If B be greater than 90°, the following are the conse- 
quences. If the longitude is in the first quadrant, the right 
ascension falls in the fourth, and on the contrary, if the lon- 
gitude is in the fourth, the right ascension falls in the first. If 
the longitude is in the second, the right ascension falls in the 
third, and on the contrary, if the longitude is in the third, the 
right ascension falls in the second. 
4. If S be on Ee, as represented in Fig. 3 and 6, the follow- 
ing are the consequences. If S be between E and the first 
point of aries the right ascension falls in the fourth quadrant, 
but if S be between E and the first point of libra the right 
ascension falls in the third. If S be between e and the first 
point of aries the right ascension falls in the first quadrant, 
but if S be between e and the first point of libra the right 
ascension falls in the second quadrant.* 
The first of these rules will be evident after the second and 
third are demonstrated. 
Demonstration of the second Rule. 
It is evident that the circle of declination for any star in 
FA />, coincides with PAy>, and therefore in Fig. 1, 2, 3, (PI. VI.) 
in which A represents the equinoctial point of aries, the right 
ascension of such a star is 0. But in Fig. 4, 5, 6, (PI. VI. ) in 
which A represents the equinoctial point of libra, the right 
ascenlion of a star on PA p is 180°. 
Now in Fig. 3. let S be a star at the intersection of the arcs 
* No provision is made in Dr. Maskelyne’s Formulas for ascertaining the right 
ascension of a celestial object on E® in either of the two hemispheres. 
MDCCCXVI. U 
