( 213 ) 



No. XXXVI. 



Memoir on the Occultation of Aldebaran by the moon on the 2\st 

 of October 1793. By Jose Joaquin de Ferrer. 



Read November 16th 1804, 

 OBSERVATIONS ON THIS OCCULTATION. 



Apparent Time. 

 h 1 11 



la the Capital of Porto-Rico by Don Cosmede Churnica, CImmersion. 12 30 33 76 

 Captain of a Ship in the Royal Navy ^Emersion. 12 57 55 8ft 



In the Observatory of Ferrol by Don Manuel Herrera, Lieu- CIm. . . 18 03 40 

 tenant in the Navy £Em. . . 19 09 59 



T „. . «, ■-„' . . Clm. . . 18 59 27 7 



In Figueras by Mr. Mechain J Em. .. 20 00 17 6 



. ,, „, , r „ ., tlm. . . 19 33 09 1 



In the Observatory of Gotha 5 Em 20 13 "0 7 



j u v xt 1 ^u . CIm. .. 18 53-28 



In Pans at the Naval Observatory j Em 19 45 36 



In Berlin Im. . . 19 46 17 



In Marseilles Im. . . 19 10 04 5 



In Dantzick Im. . . 20 14 32 



b 



From these observations results the longitude of ?» J / la 1 " d . e ' * i% ?« o 

 ti .. .J- e t> ■ j- . I Mechain. 4 33 36 2 



Porto-Rico west of Pans ace ording to j Triesnecier. 4 33 58 6 



According to the statement of Mr. Lalande in the Connois- 

 sance des Temps for the year 8, Triesnecker has, contrary to 

 the opinion of this astronomer, diminished the horizontal 

 parallax of the moon given, in the third Edition of his Astro- 

 nomy, 6"; but this variation cannot produce so great a differ- 

 ence. As the position of Porto-Rico is very interesting to 

 geographers, I have proposed to calculate all the observations, 

 to examine the elements, and point out the dependence to be 

 placed on these results. 



I had formerly calculated these observations, supposing the 

 proportion between the polar and equatorial diameters of the 

 earth to be as 229 : 230 conformably to the theory of Newton, 

 and the horizontal parallax in Paris = 57' 44" 8. Since that 

 period this proportion has been ascertained to be as 333 : 334. 

 The constant parallax of the equator 57' l", from which the 

 parallax at Paris =57' 36" 8. for the moment of the con- 



