ARTICLE XVIII. 



Observations ofEncke's Comet, at the High School Observatory, Philadelphia, 

 March and April 1842, with the Fraunhofer Equatorial, by Sears C. Walker, 

 and E. Otis Kendall. Read May 20, 1842. 



The following observations were made with a Fraunhofer Filarmicrometer, 

 with illuminated wires, applied to the nine feet Equatorial. The value of a 

 revolution of the Micrometer screw is 25". 626, as determined by several hun- 

 dred transits of stars over the wires, the interval being varied from time to 

 time, and measured on different parts of the scale. The magnifying power 

 used for all these observations was seventy-five. On all the evenings except 

 the 31st of March and 11th of April, the distance and position of the comet 

 were measured from some known star or stars. On these two evenings this 

 method was impracticable; there being no star visible in the same field of view 

 with the comet, transits of the comet and stars preceding or following it, nearly 

 on the same parallel, over the wires of the micrometer were observed, giving 

 us of course only the correction of the ephemeris in right ascension for those 

 two evenings. On all the others the corrections in right ascension, and decli- 

 nation were obtained. 







Philadelphia Siderial Time. 



Position. 



Turns of 

 Micrometer 



Measured 

 Distance. 





No. 



Observation. 







Screw. 



Remarks. 







.w 



S'. 



m. 



s' 





1 



Comet from Star a 9th mag. 



7"^ 36"» 0^3 





8.665 



222".06 



1842, March 27. 



2 



b 



7 40 53.3 





11.080 



283 .94 



Bar. 29.83. 



3 



a 



7 50 5.3 



114° 55' 







Alt. therm. 56. 



4 



b 



7 50 35.2 



51 35 







No. 1 doubtful. 



5 



b 



7 51 35.2 



53 35 









6 



a 



7 52 35.2 



113 7 









7 



(( 



7 54 57 .2 





9.827 



251 .83 





8 



b 



7 59 21 .2 





13.047 



334 .35 





9 



(C 



8 4 29.1 





13.954 



357 .60 





10 



a 



8 7 50.1 





11.153 



285 .82 





11 



(( 



8 10 25.1 



108 40 









12 



b 



8 12 20.1 



55 40 











VIII. — 4 D 













