Marsh.] 26 [March. 



Newburyport, its southern edge having an elevation of about 89" 

 above the southern horizon. 



Fortunately, Mr. Tenney was, at the moment of its formation, en- 

 gaged in correcting the altitude of that of January 16. He says : 



*' Whilst we were looking this evening, at 8 o'clock, there was a 

 magnificent auroral display, mostly, however, made up of shooting 

 beams. But all at once an arch was formed — say about ^° wide (and 

 as it passed through the belt of Orion I have a good measure for 

 that), the upper edge cutting just below Venus, and so on through 

 Orion, that being its greatest elevation, and losing itself near the 

 horizon a little south of east. The arch lasted but a few moments, 

 but for an instant or two it shone magnificently." 



By tracing on a globe an arch 3° wide, passing through the belt 

 of Orion, and similar in form to that indicated by Dr. Perkins's ob- 

 servations, we get a probable elevation of 41° for the southern mar- 

 gin, which, combined with the Newburyport elevation, gives 67 

 miles for the height of the arch. 



This arch was also seen at Dr. G. Smallwood's observatory, at 

 Montreal. He says : 



"At 7h. 50m. p. M." (exactly 8 o'clock, Newburyport time), "an 

 auroral arch was seen from this place, stretching from horizon to ho- 

 rizon E. and W., passing through the constellation Orion. It was 

 from 2° to 3° in breadth, and lasted about 18 minutes." 



Assuming this arch to have had the exact form and position of a 

 parallel of latitude, at the height of 67 miles over Newburyport, it 

 must, as seen from Montreal, have had a much less elevation than 

 any of the bright stars in Orion, and could not, therefore, be said to 

 " pass through" that constellation. 



This discrepancy may, probably, have resulted from irregularity of 

 form in this arch, combined with peculiarity of position. A glance 

 at a globe, in connection with Dr. Perkins's report, shows that in 

 this instance, as in several others recently, the pole of the arch was 

 considerably to the east of north. Consequently, Brunswick, which 

 is N. E. from Newburyport, is much more favorably situated for com- 

 parison with that place than Montreal, which is N. W. The part of 

 the arch nearest Brunswick, is that which is nearly vertical over 

 Newburyport, and observers, therefore, look at the very same object; 

 whereas that nearest Montreal lies much further N. W., and may be 

 quite different in form. 



Results based upon the former appear, therefore, entitled to con- 

 siderable weight, notwithstanding their disagreement with the latter. 



