THE MOON S PARALLAXES. 323 



11. If the altitude of the nonagefimal degree be 

 greater than the moon's polar diftance, take the fum of 

 the arcs m and n for the parallactic angle; but if it be 

 lefs, take their difference. 



12. Add the cofecant of the parallactic angle, the fine 

 of P, and the fine of the altitude of the nonagefimal de- 

 gree, together; the fum (rejecting twice radius) is the 

 iine of the moon's true zenith diftance. 



13. To the fine of the moon's true zenith diftance 

 add the logarithm of the horizontal parallax; the fum 

 (rejecting radium) is the logarithm of the parallax in 

 altitude nearly : add the parallax, thus found, to the 

 true zenith diftance, and the fum will be the corrected 

 •zenith diftance. 



14. Add the fine of the corrected zenith diftance, the 

 cofineof the parallactic angle, and the logarithm of the 

 horizontal parallax, together; the fum (rejecting twice 

 radius) is the logarithm of the parallax in latitude. 



15. Add the logarithm of the parallax in latitude, the 

 tangent of the parallactic angle, and the fecant of the 

 moon's latitude, together; the fum (rejecting twice 

 radius) is the logarithm of the parallax in longitude. 



EXAMPLE. 



cc What is the altitude and longitude of the nonage- 

 fimal degree at Ludlow, whofe latitude is 52 23' north, 

 and longitude o h . il m . weft of Greenwich, 7th February, 

 1778, at io h . 56. 11 app. time, being the time of an 

 occulation of p gcminorum ?" 



Not 



