364 On a Luminous Arch seen in the Sky.- [Nov. 



the meridian of this town, till it meets the lines between me and 

 the extremities of the arch's visible part, then it will intersect the 

 eastern line near the town of Thorns, in the West Riding of York- 

 shire ; and the western line at a point about 30 miles N, E. by E. 

 of St. Hilary Point, in the Isle of Anglesea ; having an interme- 

 diate distance for the visible part of the arch of about 74 miles. As 

 the arch at the western extremity was reduced nearly to a point, it 

 could not extend much farther in this direction j but as its dimen- 

 sions increased toward the west, the distance to which it might 

 extend beyond my view in this direction is not attainable. 



The height from a horizontal line drawn from where I stood to 

 the middle part of the arch subtended an angle of 17°, which 

 makes its altitude 7£ miles above that line. As 1 cannot be certain 

 that my observations were made exactly at the same moment as 

 those at Lancaster, I will not maintain the altitude of the arch to 

 be precisely what I have made it, but it probably approximates so 

 near to the truth that the extremes of possibility will not make it 

 more than nine nor less than six miles. 



The depth of the arch at the western extremity subtended an 

 angle of 1° 15', at its middle 52', and at the eastern part 15': 

 from which observations it appears that its depth at the first place 

 was 1504 yards, at the second place 1041 yards, and at the third 

 place 209 yards. 



The breadth of the arch at the western end subtended an angle 

 of only 8', and at the middle an angle of 5', but at the eastern end 

 the breadth was scarcely visible ; so that the breadth of the arch 

 would be nearly equal to half its depth. 



Such was the arch when I first subjected it to observation. But 

 prior to that time, as I was informed by two or three persons, its 

 length increased from west to east, as if it had been slowly projected 

 in that direction. It was then considerably to the north of Kendal. 

 It appears from accounts published in the newspapers that it was 

 seen at Dublin and Newry, in Ireland ; at the latter place, at 

 7 h 30' p. m. ; in Scotland, at Glasgow, Dumfries, and Annan, 

 about the same time; in England, at Whitehaven, at 7 U 45'; at 

 Carlisle, Kendal, and Lancaster, at 8 h 10' p. m. 



The. luminous arch moved to the southward. This motion, I 

 think, was caused by the current of the air being in this direction. 

 The air, indeed, had no sensible motion where 1 was ; but we can, 

 often see the clouds to move when we do not feel the wind that 

 moves them. This motion was not equal in every part of the archj 

 for when I first observed it its direction was N. 80 E. and S. 80 

 W.; when it had reached Lancaster it was N. 60 E. and S. 60 W.; 

 and when it was opposite Derbyshire its direction at one time was 

 N. 75*45 E. and S. 7^*45 W. During these changes of the arch's 

 direction its western part must first have been moved faster than its 

 eastern part for a certain distance ; then its eastern faster than its 

 western part for the remainder of the distance between a small 

 distance on this side of Lancaster till when it was opposite Derby- 



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