352 



Astronomieal and Nautical Collections. 



7. Apply the four corrections thus found to the apparen 

 distance, subtracting the parallactic correction, and adding the 

 refractions, when the intersection of the chords is on the same 

 side of the radius concerned with the other radius, and the 

 reverse when on the opposite side ; and adding the correction 

 for obliquity, when the distance is less than 90°. 



The diagram here exhibited was constructed, of the same size, 

 from an example in the Requisite Tables, with a common ivory 

 half inch diagonal scale, and a six inch sector only. The ob- 

 served distance J) O is 43° 36', the moon's altitude 9° 38', 

 Z. D. 80° •22' ; the suns or stars 11° 17', Z. D. 78° 43'; and 

 the moon's horizontal parallax 54' 42'— 3282". Hence we 

 obtain the parallactic correction 350", the refractional distances 

 DR aiid OR about 34° 40' and 9°, giving for the corrections 

 40' and 9" ; and, measuring the segment of the chord, found 



