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No. XIII. 



Astronomical observations made at Lancaster, Pennsylvania, chiefly 

 with a view to ascertain the longitude of that borough, and as 

 a test of the accuracy with which the longitude may be found by 

 lunar observation; in a letter from Andrew Ellicott to Robert 

 Patterson. 



Read January 21st, 1803. 



Lancaster December 16th, 1802. 

 DEAR SIR, 



IF you think the following astronomical observations of 

 sufficient importance, you have my permission to hand them 

 to the Philosophical Society. In making them I had princi- 

 pally two objects in view; first, the determination of the longi- 

 tude of this borough; and secondly, the correction of the theory 

 of the satellites of Jupiter, by increasing the number of obser- 

 vations on their eclipses. — The latitude of the place of obser- 

 vation is about 40° 2' 39" north. 



Nov. 25th, 1801. 

 limbs. 



The observed times, and distances, between the sun and moon's nearest 



Apparent time. 



Means. 



22 12 1 . 



22 13 16 . 



22 14 6 . 



22 15 14 ■ 



22 16 6 . 



.2 2 16 53 ■ 



22 14 36 . 



. 110 29 

 . 110 28 20 | 

 . 110 28 

 . 110 27 30 I 

 . 110 27 20 

 . 110 27 , 

 . 110 27 52 



.add 15 "for the error of the sextant. 



27th, The observed times, and distances between the sun and moon's nearest limbs 



/ // 



23 19 20 

 23 20 19 

 23 21 10 

 23 21 45 

 23 22 17 

 _23230 

 Means. 23 21 18 



Apparent time. 



o / // 



88 11 10 

 88 11 0, 



88 10 40 

 88 10 20 

 88 9 50 

 88 9 30 

 88 10 25 



.add 15 ''for the error of the sextant. 



