Observations upon Auroral and Optical Phenomena. 219 



not affect the comparison in respect of altitude, except in a trifling 

 degree. Indeed, since the motion of the cloud was almost exactly 

 along its oivn rectilinear base, and since the comparison of the ob- 

 servations at both stations was made by taking the distance of a 6xed 

 star (Alpha Draconis) from that base, it being distant only two or 

 three degrees at farthest, it may be asserted that any uncertainty 

 arising from a difference in the watches of the observers, or their es- 

 timates of the hour and moment, is completely done away by the 

 circumstances of the phenomena. 



Under these favorable circumstances, therefore, comparing the 

 sketch and notes made on the spot, and at the time of observation, 

 by Mr. E. C. Herrick, at New Haven, at 9h. 15m. P. M. with 

 those made under like circumstances by myself at New Britain, and» 

 as it happens, at the same moment, I find the distance from Alpha 

 Draconis to be the same in both cases, — indicating the entire absence 

 of a parallax sufficiently considerable to be detected by this kind of 

 observation, — which is of course not expected to be exact, — within 

 perhaps i° or 1°. 



Prof. Stanley had not minuted his observations, at the time of 

 making them ; but before having access to any other observations he 

 fixed carefully by recollection the situation of the phenomenon at 

 9h. 40m. P. M. The cloud thus delineated by him was almost 

 identical in extent and situation with the same as delineated by my- 

 self, at the last specific observation made by me, at 9^. 30m. at New 

 Britain, — except that the distance of the lower line from Alpha Dra- 

 conis was in the first case 1° 40', and in the last 3° — showing a par- 

 allax of 1° 20' only. 



The third observer before alluded to, having also delineated zn<?e- 

 pendently on a celestial map the same cloud as observed by him, 

 gave it a situation, extent and form, agreeing closely with the obser- 

 vations of Prof. Stanley and Mr. Herrick. Not having the map at 

 hand I cannot now state particulars, although at the time this obser- 

 vation afforded a striking confirmation of the truth of the general 

 conclusions we are no\v about to deduce. 



My object is not, let it be noticed, to show the exact distance and 

 height of the cloud observed, but to exhibit proof of this one fact that 

 it was elevated, most unquestionably, either above the atmosphere, or 

 into its extreme upper regions. By Mr. Herrick's observations, 

 compared with my own, made at, or certainly near, the same mo- 

 ment of time, it would appear that the cloud was too distant for d 



