233 

 XXXVIII. Intelligence and Miscellaneous Articles, 



OBSERVATIONS ON TWO ARCHES OF AURORA BOREALES. 



FROM R. POTTER, ESQ. 



THE observations I have to offer on these two appearances of the 

 aurora borealis, are not such as would be necessary for very ac- 

 curate calculations of the height of the meteor j they will nevertheless 

 suffice for determining this height approximative^ if contemporaneous 

 observations should chance to have been made in places properly situ- 

 ated for the purpose. Indeed, if we adopt the hypothesis, as already 

 sufficiently demonstrated, that the arches are portions of luminous 

 rings round the magnetic axis, we may reduce the observations of 

 any two localities to a common magnetic meridian, when the arch has 

 not exhibited any deviation from a regular curvature. 



The last arch of those below having been nearly stationary for a 

 considerable length of time, I hope it may have been observed in 

 Scotland ; and if Mr. Wharton of Dryburn near Durham shall have 

 seen it, I am sure he will in such case not have failed to have ascer- 

 tained its apparent altitude with an instrument. Though this gen- 

 tleman's observation, combined with mine, would not be adequate, 

 from the too great proximity of the places of observation, for even 

 an approximate calculation of the height, yet by using the reduction 

 mentioned above, Mr. Wharton's observation, combined with a simi- 

 lar one taken in the neighbourhood of Melrose or Edinburgh, would 

 go far to settle finally the interesting question as to the region in 

 which this meteor takes place. 



Observation 1. — The Sunday, 23rd Sept. 1832, was remarkably- 

 calm at Smedley, situated about If English mile to the north of the 

 spire of St. Mary's church in Manchester, of which the latitude and 

 longitude are on record ; in the evening the sky was generally clear, 

 though somewhat hazy near the horizon, — there was an appearance of 

 a faint aurora. A faint arch, which had appeared, had at fifty-five 

 minutes past seven o'clock an altitude of about 20° for its middle 

 breadth ; at ten minutes past eight its altitude was about 25°. It 

 afterwards rose still higher, but was become almost imperceptible 

 at half-past eight. A few faint streamers were seen, and more light 

 on the horizon. The arch was not complete, reaching only from about 

 the true north to the western horizon : its great faintness prevented 

 me taking a better observation and measuring its breadth. There 

 I ad been an auroral light visible in the north for several evenings, 

 but the sky was cloudy. 



Observation 2. — On my return from a short visit to Sir David Brew- 

 ster at Allerly, when I arrived on the 21st Dec. 1832, by the Chevy- 

 chase coach, to within thirteen miles of Newcastle-upon-Tyne, I per- 

 ceived, on looking towards the north-north-west, that there was a very 

 distinct arch of an aurora ; it was just seven o'clock in the evening 

 when I first saw the arch, and I immediately set about to estimate the 

 altitude of its highest point, which I called to be nearly 1 1° for its 

 under edge, and its breadth to be about 4°. I was rather unfavour- 

 ably seated for watching the arch continually, and it was only some 



Third Series.Vo}. 2. No. 9. March 1833. 2 H 



