I saw the aurora of September 3rd 1870 described by H C Key and I observed it from 10.00 to 11.00 PM but here it never reached quite to the zenith, and at 11.20 was no where high. Its brightest feature was then a distinct arch, the apex of whose central line was 12 degrees in altitude. If Mr Key’s description of the clear space of 7 or 8 degrees below the aurora in the S S E, applies to that time, it would seem that part of the aurora bordering the clear space cannot have been more than 25 miles above the Earth, and was more likely only 17 or 18 miles.
It would be well if the heights of the aurora were better
known than they are; and I think if systematic observations were made
simultaneously at different stations, knowledge of the subject would be
largely increased. I am willing to be one of the observers is such an
investigation, and Mr G J Symons the editor of the Meteorological Magazine ,
has expressed his readiness to aid.
T W Backhouse Sunderland July 22nd 1871
www.theramblingastronomer.co.uk
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