310 



Prof, Fisher on the Orbit of the Comet of 1819. 



rly twice as g 



On 



when its brightness 



naked ejre had greatly diminished, the greatest perceptible diame- 



istment of the focus was made by 



/ 



ter was 2^ minutes. The adjustment 

 looking at Jupiter ; and the micrometer employed in these meas- 

 urements gave the diameter of Jupiter within about S'''' ot the 

 truth. 



r 



After the 12th of July, the brightness of the head began sen- 

 sibly to decline, and the length of the tail gradually diminished. 

 The following table contains the estimated brightness compared 

 with that of surrounding stars, and the lengtb of the tail; at 



al 



> 



before its disapp 



Time. l-Vlag-nitude.JLeng'th of the tail. 



July 5 



13 



19 



25 

 31 



1 



2.3 

 4 

 5 

 6 



8° 

 8 



or 9 



5 

 1° 



3° 





After the morning of July 31st, it was not seen in New Haven 

 With a forty inch refractor, it was supposed to have been seen ii 

 New York, as late as the 10th of August. 



. ■ 



O 



the 



mornm 



distances of the 



July 6th, a series of 



convenient fixed stars was 



commenced in the Lyceum of Yale College, and continued 



the state of the atmosph 



would permit 



disappeared 



These observations were made when the comet was between 5° and 

 iO^ above the horizon, and therefore, independently 



of the neces- 



y 



mperfection of 



ployed, are liabl 



uncertainty, on account of the irregularity of refraction. 



A first approximation to the elements of the orbit was deduced 



from fiv 



made betwe 



J 



July 6th and 



The 



/ 



^ 



