410 Astronomical and Nautical Collections, 



Angle B 13° 51' 0'' Sec. 0.01281 



Semidiameter .... 14 46 P. L . 1.08599 



DifF. of apparent altitudes . 14 20 P. L. 1.09880 

 •)(-'s apparent altitude , 47 28 9 

 > 's apparent altitude . 47 42 49 Sec. 0.17204 

 Reduced horizontal parallax 54 9 P. L. 0.52167 



Log. cosec. compl. A 1.10696 



Orbit, parallax + 2 51 P. L. 1.80067 



Log. tan. compl.. A 8.89437 



Perp. parallax , . . . -36 20 P. L . 0.69504 



Nearest distance .... 50 31 

 Perp. parallax . , . . — 36 20 ' 



Sum 14 11 



Semidiameter 14 46 



Sum 28 57 P. L. 0.79362 



Difference 35 P. L . 2.48900 



2)3.28262 



Side * . + 4' 7'^ P. L . 1.64131 



Orbit, parallax .... +_2_51 



+ 6 58 



Whence 6' 58'^ gives 14™ 4" .4 of time, wliich subtracted 

 from 3'^ 17"^ 1" leaves the 



Tme time at Greenwich . 3^^ 2™ 56".6 



True time at ship . . 1 37 49 



Difference of time . . 1 25 7.6 == 21° 16' 54" W. long. 



Longitude found by Mr. Henderson'sl pi n K W 



method j ~~ ^ 



Error of his method, in the present! 16 39 



example J 



Now by referring to a diagram, it may be easily disco- 

 vered, that the operation marked % ought to comprehend the 

 solution of a rightangled plane triangle, whose hypotenuse 

 is the moon's parallax in altitude, the perpendicular being 

 the perpendicular parallax, and the base the orbital parallax. 



This would be precisely the case, if, in the second term, 

 the log. secant of the moon's apparent altitude were substi- 



