Histnnj of Astronomy for the Year 1806. Cg 



tlie sliding tubes H, till the pencil is within half an inch of 

 the paper (in the middle of the board), and proceed as be- 

 fore. 



1 o make the drawing smaller, shorten the tubes C and H 

 by sliding them in, and proceed as before. 



Any thing not clearly understood will be explained by the 

 maker. 



The price of the instrument is five guineas, neatly packed 

 in a box fourteen inches lona;, three inches deep, and six 

 inches wide. 



X. History of Astronomy for (he Year 1806. By Jerome 

 DE Lalande *. 



JL HE comet discovered by M. Pons at Marseilles deserves 

 to be first mentioned in the History of Astronomy for 1806: 

 he saw it on the 1 ith of November, in the morning, and it 

 is the 97th we are acquainted with, according to the cata- 

 logue given in my Astronomie, and in the different volumes 

 of the ConnoisiOfices des Terns published since the year 



1792, in which I have given notices of the conie's; and it 

 is the sixth which M. Pons found since the 11th of July 

 1801. M. Thulis, director of the observatory, observed it 

 as well as the bad weather would permit him, as the months 

 of November and December arc inimical to astronomical 

 pursuits even at Marseilles. This comet was very small, 

 shapeless, without any sensible nucleus, and not visible to 

 the naked eye. On the 9lh of November, at 17'' mean 

 ♦ime, it had 181° 3' right ascension and 2° of northern de- 

 clination. 



As soon as I received this intelligence I communicated it 

 to M. Rouvard and M. Burckhardt, who observed it at Paris; 

 the latter furnished us, on the day following, with the ele- 

 ments of its orbit, and continued to observe it : on the 

 18th of December, at IG'' 26' mean time, it had J l"' 12' 4l'^ 

 of right ascension and 32" 37' of declination : it advanced 



* From Magazin Encijdopidiquc, February 1807, p. 'ZQ'U 



E 3 rapidly 



