OBSERVATORY AT WEST POINT. 199 
the solar spots; and as I have not met with it before, I have thought it would not be out 
of place to give it here. 
Let s denote the apparent diameter of the sun in seconds of space, 
4 | x the apparent distance between the parallel wires of the micrometer 
Y expressed in the same unit, ¢ the time of the sun’s diameter passing 
each wire, supposed perpendicular to the equator, and ?’ the time re- 
y quired for the same limb to pass from one wire to the other. Then 
rl | assuming that the motion of the sun in right ascension is uniform during 
the transit over each wire, will 
whence calling v the value of one division on the screw head, and the number of these 
divisions which mark the separation of the wires, we have 
Bic Bagot 
Va eee sl —7 . . e ° * . (8) 
ee : 
EXAMPLE. 
March 24th, 1843. 
‘Ist §11"25" 40.5... (1) Ist §11" 32m 12. .. . (1) 
Limb. 211 26 34. ...(2) (4 Limb.21) 83 04.5...(2) \p 
MG: SII SH iler ary Qd Cll 84 24.5... (1) 
Limb. 211 28 42.5... (2) Limb. 211 85 18. ... (2)! 
A § (LY —(1)=2 1355 
(2)/—(2)—2 08.5 
B ie el 12°.5 
(2)’—(2)—2 08.5 
4)8 43 = 2" 10°75 = 130.75 =. 
A §(2) —(1) $535 
(2)—(1)’=48 .5 
p § (2)—(1) =62".5 
(2)—(1)' 48 5 
4) 203 = 60°.75 =f. 
From Naut. Alm. s = 1925’.68. 
The wires were separated by a distance of ten revolutions in each screw, and the heads 
having one hundred divisions each, 
n = 2000. 
