Height of Aurora. Sir John Franklin considers it within the region of the clouds. At no great elevation.
Sir John Franklin (Narrative of a Journey on the Shores of the Polar Sea in the years 1819, ’20, ’21, ’22) says:—“My notes upon the appearance of the Aurora coincide with those of Dr. Richardson in proving that that phenomenon is frequently seated within the region of the clouds, and that it is dependent in some degree upon the cloudy state of the atmosphere.” And further:—“The observations of Dr. Richardson point particularly to the Aurora being formed at no great elevation, and that it is dependent upon certain other atmospheric phenomena, such as the formation of one or other of the various modifications of cirro-stratus.”
Sir John Franklin also refers to notes from the Journal of Lieut. Robert Hood, R.N., on an Aurora:—
Observations of Lieut. Robert Hood and Dr. Richardson. A beam not more than 7 miles from the earth. An arch 7 miles from the earth.
The observations were made at Basquian House, and at the same time by Dr. Richardson at Cumberland House, quadrants and chronometers having been prepared for the purpose. On the 2nd April the altitude of a brilliant beam was 10° 0´ 0″ at 10h 1m 0s at Cumberland House. Fifty-five miles S.S.W. it was not visible. It was estimated that the beam was not more than 7 miles from the earth, and 27 from Cumberland House. On the 6th April the Aurora was for some hours in the zenith at that place, forming a confused mass of flashes and beams; and in lat. 53° 22´ 48″ N., long. 103° 7´ 17″, it appeared in the form of an arch, stationary, about 9° high, and bearing N. by E. It was therefore 7 miles from the earth.
An arch between 6 and 7 miles from the earth.
On the 7th April the Aurora was again in the zenith before 10 P.M. at Cumberland House, and in lat. 53° 36´ 40″ N., long. 102° 31´ 41″. The altitude of the highest of two concentric arches at 9h P.M. was 9°, at 9h 30m it was 11° 30´, and at 10h 0m 0s P.M. 15° 0´ 0″, its centre always bearing N. by E. During this time it was between 6 and 7 miles from the earth. [The bearings are true, not magnetic.]
Sir John Franklin’s remarks.
Sir J. Franklin says this was opposed to the general opinion of meteorologists of that period: he also noticed he had sometimes seen an attenuated Aurora flashing across the sky in a single second, with a quickness of motion inconsistent with the height of 60 or 70 miles, the least that had hitherto been ascribed to it.