220 = Observations upon 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 14° be- 
tween the stations twenty six miles apart. Considering therefore the 
definite 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 191°, we find, 
without stating the calculation bere, 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 third. 
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. 
Auroral 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 
