THE 



AMERICAN 

 JOURNAL OF SCIENCE, &c. 



Art. I. — Observations upon certain Auroral and Optical Phe- 

 nomena; by Alexander C. Twining. 



The height of auroral phenomena is a subject which has divided 

 philosophers. Some consider them as lying in the lower regions of 

 the atmosphere ; while others would elevate them beyond its sup- 

 posed limits, or at least into its extreme upper regions. It is my in- 

 tention to prove in three instances of late occurrence, that the latter 

 opinion is the true one. 



Auroral Cloud of December, 1835. 



On the evening of the 1 0th of December, 1 835, being at the village 

 of New Britain, which is twenty six miles N. and 15° E. from the 

 city of New Haven, I observed attentively, for more than an hour, 

 an auroral cloud of very unusual appearance. At the beginning of 

 my observations, about half past 8 o'clock, P. M. it was situated 

 about 25° east of north, and at an average altitude of 11°. The 

 star Beta Ursae Majoris was enveloped in its upper portion, but not 

 obscured. 



This altitude changed only 9° during the period of my observa- 

 tions, although the cloud moved horizontally towards the west not 

 less than 20° in the same time. The cloud had a horizontal extent 

 of at first about 16° ; but was narrow (only 4°) in the vertical di- 

 rection, — being irregular in its upper outline, but shaped, on the 

 whole, somewhat like a very excentric semi-ellipse. Its lower limit 

 however was a well defined line; and in respect of this feature the 

 cloud continued unchanged, whenever it was visible, through all its 



Vol. XXXIL— No. 2. 28 



