ASTRONOMY AND METEOROLOGY. 395 



BRORSEN'S COMET. 



A comet discovered by Bruhn's of Berlin during the past year, has ac- 

 quired an unusual interest, from the fact that its identity with a comet dis- 

 covered by Brorscn of Kiel, has been satisfactorily proved, and its time of 

 rotation about the sun determined. This amounts to a period of 2,026 days, 

 (five years six and a half months) and the greatest axis of the line of rotation 

 is about 000,000,000 miles long. This is the third comet of short rotation 

 known to us, the two others being those of Biela and Encke. 



ON THE POSSIBLE EXISTENCE OF A LUNAR ATMOSPHERE. 



The occultation of the planet Jupiter by the moon on the 2nd of January, 

 1857, afforded to English observers some results which have given rise no 

 little speculation and theory. 



An occultation of any of the larger planets is always an occurrence of sur- 

 passing interest to astronomers, because the clear, well-defined images which 

 they present in good telescopes, are pictures of such exquisite delicacy, that 

 they afford a very severe test of the condition of the lunar surface as to 

 the presence or absence of gaseous or vaporous investment, when that sur- 

 face is seen in front of the picture in the act of sweeping before it ; the small- 

 est amount of vapor or gas would perceptibly dim and distort the delicately 

 sketched light image contemplated under such circumstances. When it is 

 Jupiter that undergoes occultation, there is also additional interest, because 

 this planet is" waited upon by four satellites of considerable brilliancy, which 

 have to pass in succession behind, and out from the border of the moon ; 

 so that there are, as it were, five occupations in one to be observed. 



During the recent occultation of Jupiter, a large number of excellent ob- 

 servations were recorded. From among the trust-worthy observers, Messrs. 

 TV. fl. Grove, Dawes, Hartnup, and J. Watson, Dr. Mann and Lord Wrot- 

 tcsly agreed in the positive statement that there was no perceptible altera- 

 tion of the planet's figure, or distortion of outline, while the planetary image 

 was in apparent contact with the moon, and under good optical definition. 

 Mr. William Simms and Mr. Lassell, on the other hand, described the 

 curved outline of the planet as appearing to be flattened, or bent outwards 

 towards the moon's limb. Mr. Lassell's observation, however, affords a su"-- 



O 



gcstion for the ready explanation of this discrepancy. This gentleman 

 noted distortion as the planet went behind the moon, but distinctly states 

 that there was none as it came out from concealment; and further remarks, 

 that the air was very unsettled, and vision very unsteady at the commence- 

 ment, but the definition much more even and satisfactory at the conclusion 

 of the occupations. Mr. William Simms also says that the atmosphere at 

 Carshalton, where his observation was made, was very unsteady. In all 

 probability, the distortion of the planet's figure, noticed by these observers, 

 was due to the unfavorable state of the earth's own atmosphere at their stations, 

 causing the image of the planet to tremble and undulate while under in- 

 spection. 



