Solar Eclipse of July 8th, 1842. 177 



telescope, is red or green. These irregularities, as seen by many, 

 have been minutely described by Francis Baily, Esq. of London, 

 in an article in the tenth volume of the Memoirs of the Astro- 

 nomical Society, although it particularly relates to the appearan- 

 ces, observed by himself, in the south part of Scotland, during 

 the eclipse of May 15th, 1836, which was annular there. Many 

 of the appearances described by Mr. Baily, were seen through a 

 red glass at the second and third contacts of the eclipse of Feb. 

 I2th, 1831, which was annular in the southeastern part of this 

 State. Shortly afterwards, however, it having been ascertained 

 that a double screen, composed of one light red and one light 

 green glass, would not only render the light of the sun very 

 pleasant to the eye, but would far better define the limbs, and 

 would sometimes even enable me to see a small spot, that was 

 invisible through the dark red alone, a screen of that kind was 

 adapted to the telescope, and was used for the partial eclipses of 

 1832 and 1836, and those that were central in 1834 and 1838. 

 Through this screen no one of the irregularities described by 

 Mr. Baily, has ever been perceived, although carefully looked for. 

 Indeed so remarkable was the difference between the observed 

 and expected appearances of the sun's limbs at the second and 

 third contacts at Beaufort, S. C. on Nov. 30th, 1834, that even 

 then, a suspicion was excited that the entire absence of all distor- 

 tion or irregularity in the cusps, just before and after the total 

 obscuration, was to be attributed to the color of the screen ; espe- 

 cially since other observers in the vicinity of Beaufort saw through 

 red screens, many or most of the usual phenomena. This suspi- 

 cion was strengthened by the observations on the large but not 

 central eclipse of May, 1836 ; it was therefore communicated to 

 several of our astronomers, who paid particular attention to it, at 

 the formation and rupture of the ring on Sept. ISth, 1838. In 

 Philadelphia and its vicinity there were many observers, provided 

 with telescopes of nearly equal optical capacity, but protected by 

 screens of different colors. The result appears to be, that in every, 

 or nearly every instance in which the red glass was used, many 

 or all of the usual irregularities were seen, whilst those observers 

 who used yellow or green screens, saw these appearances either 

 greatly modified or not at all. At Princeton, near the northern 

 boundary of the ring, two skilful astronomers, provided with 3 J 

 feet telescopes by Dollond and Fraunhofer, were enabled dis- 



Vol. xLii, No. 1.— Oci.-Dec.1841. 23 



