1865.J 25 [Marsh. 



lonj^. 69° 55'), contained the following notice by the editor (Mr. A. 

 G. Tenney) : 



** We observed a magnificent aurora on Monday night, just about 

 8 o'clock. At that hour it formed two bows, the larger and exterior 

 one spanning the sky from N. E. to N. W., at an angle of about 45° 

 at its greatest elevation above the horizon, while the interior bow 

 extended only a few degrees, and rose not more than 4° or 5° above 

 the horizon. Both were as perfectly marked, well defined, and dis- 

 tinct as any rainbow that we ever saw; although, in the case of the 

 aurora, the bows were broad bands of light, the larger one covering 

 several degrees of the heavens." 



Mr. T. informs me that the estimated altitude was obtained by 

 fixing his eye upon what he supposed to be the zenith, and then 

 running it down to the upper edge of the bow, and estimating the 

 proportional parts. On going again to the same spot, and recalling 

 as nearly as possible the position of the arch, he was confirmed in hia 

 original estimate. But subsequently being furnished with a star 

 chart, upon which he could trace its position, he satisfied himself 

 that his figures were too high, and the path which he finally marked 

 upon the chart as the result of repeated trials, indicates an elevation 

 of only 32°. In view of the well-known tendency, in all unprac- 

 tised observers, to underestimate zenith distances, this change is 

 about what might have been anticipated, and the corrected result 

 seems to be entitled to confidence as an approximation. 



Eight o'clock at Brunswick corresponds to 7h. 39m. at German- 

 town, at which time my notes show that the upper margin was about 

 11° below Zeta, or about 7^° above the horizon. 



Taking as a base line the difference of latitude (3° 52'), and com- 

 bining these results, we get for the actual height of the arch from 

 the surface of the earth, 67.3 miles. 



On the 20th of February there was another arch, which was thus 

 noticed by Dr. Henry C. Perkins, in the " Newburyport Herald" of the 

 following day : 



*• As the Pleasant Street clock struck eight last evening, a bril- 

 liant arch, about 6° or 7° in width, spanned the heavens from east 

 to west; involving in its luminosity the four stars in the head and 

 neck of Leo; passing about 2° to the north of Castor; having Ca- 

 pella on its southern edge, inclosing Perseus and Andromeda in its 

 folds, and thence coming more directly to the west. It was quite 

 uniform in its width and brilliancy, but lasted only a few minutes." 



This description shows that this arch passed through the zenith at 



VOL. X. — D 



