220 Observations vpon Auroral and Optical Phenomena. 



parallax sufficiently considerable to be appreciated. All however 

 that we can safely deduce from this, (and so much is deduced with 

 entire certainty,) is the fact that the parallax was very small. 



Again, by combining Professor Stanley's observations with my 

 own, made indeed ten minutes earlier, but still perfectly comparable 

 with them in consequence of the peculiar and propitious circumstan- 

 ces before stated, it would appear that a parallax existed of 1\° be- 

 tween the stations twenty six miles apart. Considering therefore the 

 de6nite character of the object, and the care taken in the different ob- 

 servations, and even allowing some latitude for errors attendant on the 

 best observations of such bodies, there would seem to be no possible 

 reason for suspecting in this case a parallax of more than 1° or 2°, 

 or at most 3°. Indeed, by assuming the latter amount (3°) we shall 

 be almost certain of assigning to the cloud a distance and height far 

 less than the truth. 



Assuming however a parallax so large as 3°, between the two sta- 

 tions, twenty six miles apart, and nearly in a line with the cloud, — the 

 elevation at the most northern or nearest station being 19^°, we find, 

 without stating the calculation here, the distance of the cloud from 

 New Haven in a direction a little east of north, to have been one 

 hundred and forty one miles in a direct line ; and the height above 

 the surface of the earth to have been forty two miles and one thii-d. 

 This is the nearest point which we are at liberty to assign. It would 

 have agreed better with our direct observations to have placed the 

 cloud at a height three or four times as great : but in the present 

 state of our knowledge it is most important to settle, if possible be- 

 yond dispute, the general question respecting the region in which the 

 auroral phenomena have their residence. Therefore I have leaned 

 to the extreme of caution, 



Avroral Arch of August^ 1836. 



On the 12th of August, 1836, being on board one of the Hartford 

 steamboats going to New York, I noticed, early in the evening, au- 

 roral lights of considerable brightness and beauty ; but without making 

 any particular observations. A little before ten o'clock, P. M. how- 

 ever, there appeared a streamer (as I took it to be) in the west, rising, 

 not vertically, but somewhat obliquely — its higher parts inclining 

 southward, and the whole of a yellowish hue. Just opposite to this, 

 in the eastern quarter of the horizon, I soon noticed another streamer 



