Various observations made by Professor Olmsted, in conjunction with Professor Twining, of New Haven, led him, on the contrary, to fix the elevation on different occasions at forty-two, one hundred, and one hundred and sixty miles. He claims that it is rarely less than seventy miles from the earth, and never more than one hundred and sixty. He also claims that its origin is cosmical,--or, in other words, that the earth, in revolving in its orbit, at certain periods passes through a nebulous body, which evolves this strange light in more or less brilliancy, as the body is larger or smaller. To support this theory, he attempted to establish that there were fixed epochs for its display in the highest degree of brilliancy. The length of these periods was from sixty to seventy years, and the next appearance was to be in 1890. The remarkable displays of August 28th and September 2d show the fallacy of his conclusions in this respect.
Mairon and Dalton had also thought that the aurora borealis was a cosmical, and not an atmospheric phenomenon. But M. Biot, who had himself had an opportunity of observing the aurora in the Shetland Isles in 1817, had already been led to recognize it as an atmospheric phenomenon, by the consideration that the arcs and the coronae of the aurora in no way participate in the apparent motion of the stars from east to west,--a proof that they are drawn along by the rotation of the earth. Hence, almost all observers have arrived at the same conclusions; we will in particular cite MM. Lottin and Bravais, who have observed more than a hundred and forty aurorae boreales. It is therefore now clearly proved that the aurora borealis is not an extra-atmospheric phenomenon. To the proofs drawn from the appearance of the phenomenon itself we may add others deduced from certain effects which accompany it, such as the noise of crepitation, which the dwellers nearest to the pole affirm that they have heard when there is the appearance of an aurora, and the sulphurous odor that accompanies it. Finally, if the phenomena took place beyond our planet and its atmosphere, why should they take place at the polar regions only, as they often do?
J. S. Winn, in a letter to Dr. Franklin, dated Spithead, August 12th, 1772, says: "The observation is new, I believe, that the aurora borealis is constantly succeeded by hard southerly or southwest winds, attended with hazy weather and small rain. I think I am warranted from experience in saying _constantly_, for in twenty-three instances that have occurred since I first made the observation it has invariably obtained; and the knowledge has been of vast service to me, as I have got out of the Channel when other men as alert, and in faster ships, but unapprised of this circumstance, have not only been driven back, but with difficulty escaped shipwreck."