LXXXni. On the Passage of the Comet 0/ 1819 across the Disc 

 of the Suvt *. By M. Olbers. 



All the elements indicated this passajre. According to thos,e 

 of Dirksen, the immersion was to take place at 17'' 30' 34", and 

 the emersion at 21'' 5' 37 " on the 2Jth June 1819; the hours 

 were reckoned according to true time, Milan meridian. At 19^ 

 IS' 6'' the centre of the comet was only removed from that of 

 the sun 2' S". The aberration retards these phases 5' 31" and 

 the parallax half a minute for the observatories of Germany. 



In the Ephemeris of Berlin for 1822, 1 concluded (says 

 M. Olbers) from tlie observation of M. de Lindener, confirmed by 

 an observation made in Austria, that the comet had been invisible 

 on the disc of the sun ; but it is now proved that the sun was 

 not without spots at that epoch ; and if these spots were not re- 

 marked by the two observers to whom I have alluded, the comet, 

 much more difficult to be seen, may also have escaped their no- 

 tice, although a more attentive or more piercing eye might have 

 been able to discern it. The following are incontestable proofs 

 of the existence of the spots. 



(I). M. Schumaker, then at Altona, had determined the col- 

 limation of his Troughton's sextant several tin)es in the course of 

 the month of June ; and among others, on tlie 25th at 20''. He 

 recollects most positively of never having seen the sun without 

 j-pots. The glass of the sextant multiplied nearlv teiJ times; it 

 is therefore not probable that one of these spots could be the 

 comet. 



(2.) Professor Brandes at Breslau viewed the sun on the 2Cth 

 of June, a little before midday, with a glass of a thirty-four times 

 uuilliplying power, and he perceived a spot distinctly visible, al- 

 most passing behind the disc, and precisely at the place where it 

 ought to have been according to the preceding observations. 

 This observation becomes important when compared with that 

 of Dr. Gruithuisen inserted in the Gazelle Politique of Munich, 

 of the 12th of August 1819. According to the Meteorological 

 Journal of Dr. Gruithuisen, there were on the 2()th of June, at 

 eight in the morning, two small spots without nebulositv near the 

 west limb of the sun. One also was seen in the midst of the 

 apparent disc. As well as he can recollect, the spot in the mid- 

 dle was very small and undefined ; it is possible, therefore, that 

 this philosopher might have seen the comet on the disc of the 

 sun. Nevertheless doubts must still remain, until we learn that 

 some other observer has seen this black point, either forward 



* K.xtracied from a Memoir by M. Olbers in the Ephemeris of Berlin 

 far \623. 



