Observations upon Auroral and Optical Phenomena. 227 



lax which could be assigned, consistently with the observations, would 

 elevate the bow more than one hundred miles above the surface. 

 Indeed, Prof. Olmsted has publicly expressed his own judgment as 

 to the height of this bow at the time of his observations, which he 

 makes as great as one hundred and sixty miles. The last, however, 

 ought perhaps to be esteemed the maximum height which we are at 

 liberty to assign. The meridian of this arch, like that of August, 

 appears to have been directed to the east of north. 



Dip of the Auroral Streamers. 



In the brilliant aurora of Nov. 17th, 1835, a corona was formed 

 at about 11 o'clock, P.M. Its position was, to my own view, in 

 23i° N. Dec. I made the observation at Berlin, in Lat. 41° 40'. 

 Taking into view the position of the magnetic meridian, the dip, of 

 course, was 71°, very nearly, at that place. The first corona of 

 April 22d, 1836, at about midnight, was, to my view at New Haven, 

 (lat. 41° 18',) in 235° N. Dec. It moved regularly north, and in 

 three quarters of an hour, was in 25^° N. Dec. In one hour and 

 a quarter more it had returned to 24° 10'. The average dip would 

 be about 72^°. Much the most definite observation of the kind 

 I have been able to make was on the occasion of the magnificent 

 display of Jan. 25th, I83T. The corona was then situated in Dec. 

 N. 23|°, and the dip was of"course near 71i°. 



r take this opportunity to relate the occurrence of a few optical 

 appearances, which I have witnessed at different times, and which 

 may deserve notice. 



Supernumerary Rainbows. 



In the latter part of September, 1823, being on the river St. Law- 

 rence, and having arrived at Montreal just at sunrise, I noticed in 

 the west a dark blue cloud, which came over rapidly. The sun was 

 shining very brightly from the opposite quarter, and formed in the 

 cloud a bow of remarkable vividness and completeness. The se- 

 condary was also complete, and nearly as distinct in all its colors as 

 the primary commonly is. The primary, although vivid, was less 

 cheerful than usual in its aspect ; owing probably to the sombre sha- 

 ding of the cloud seen through it. The violet seemed darkened to 

 a dull red. Under the primary, an arc of the same color with the 

 interior of the primary, (i. e. violet, or rather a dull red,) extended 

 parallel with it nearly through the arch. Then followed a second arc, 



