Astronomical Society. 151 



author proceeds to give his own observations on Encke's comet, at 

 the time of its last perihelion passage in 1838, when it appeared 

 under circumstances favourable for observing the nebulosity. He 

 states that he was able to follow the comet till the evening before 

 the perihelion j^assage ; that he observed it to diminish rapidly, and, 

 after being prodigiously reduced, to melt away, as it were, under his 

 eyes, disappearing only in consequence of its extreme smallness, in- 

 asmuch as its brilliancy should, from its position, have continued to 

 increase. The observations are as follows: — 



On the 9th and 10th of October, the nebulosity subtended an an- 

 gle of 20', but it diminished continually after that time. On the 

 loth of October, he first i*emarked it to be elongated in the direction 

 of the sun ; and the elongation continued to increase until the 25th 

 of October, when the greater diameter appeared to be double the 

 smaller, after which it began to diminish. The most luminous part 

 was not at the centre, but at the point opposite the sun. On the 

 25th of October, the nebulosity was reduced to 15', and the real 

 volume was then eighteen times smaller than on the 10th. On the 

 6th of November, the nebulosity was 13', and the volume reduced 

 to l-40th. On the 13th of November, the nebulosity was 11' ; on 

 the 16th, between 8' and 9' ; on the 20th between 6' and 7'; on the 

 23rd, 4' ; on the 24th, 3', and the real volume, 826 times less than on 

 the 10th of October. On the 29th of November, the comet could 

 no longer be seen in the evening twilight, but it reappeared on the 

 morning of the 7th of December *. On the 12th of December it ap- 

 peared as a star of the fifth magnitude ; and its diameter was less 

 than 20", being entirely covered by a wire of that thickness. The 

 volume deduced from this apparent magnitude would be 80,242 

 times less than on the 10th of October. On the 14th of December 

 it appeared feebler, and equal to a star of the sixth magnitude, with 

 which it was compared; its diameter was then estimated at 15". 

 On the 1 6th the comet appeared as a star of the seventh magnitude, 

 and its apparent diameter was from 10" to 12". On the 17th it was 

 reduced to the eighth magnitude at most, and its apparent diameter 

 was from 7" to 8". On the 18th of December it was entirely invi- 

 sible, although stars of the seventh and eighth magnitudes were 

 seen in its neighbourhood. From these comparisons it appears that 

 the real diameter must have undergone a diminution from the 10th 

 of December*, when it was first observed in the morning, until the 

 1 8th, when it finally disappeared. 



A Letter from Professor Schumacher, to Francis Baily, Esq., an- 

 nouncing the Discovery of a Comet by M. Galle, assistant in the 

 Berlin Observatory. 



The comet was discovered on the 2nd of the present month, 1 7^^ 

 45°^ mean time (Berlin), in the constellation Virgo. Comparing it 

 by the great refractor, with a star of the tenth magnitude (which 

 star was immediately compared with y Virginis), M. Galle obtained 

 the follomng positions : — 



* There must be some error here in the dates. — Edit. 



