AUROHAL ARCH. 189 



bly distant from the line of direction of the luminous arch will consti- 

 tute data for ascertaining its elevation. The observations which 1 have 

 been able to collect, although not of sufficient accuracy to determine 

 the exact height, unquestionably establish the fact that it was heyond the 

 region of the atmosphere. 



The papers of New York, Philadelphia, Baltimore, Washington, 

 Pittsburg, Chambersburg and Carlisle, all describe it as passing either 

 through or near the zenith. Professor Locke, of Cincinnati, has given 

 in the Pittsburg Gazette, a particular description of the appearance as 

 witnessed by himself on the Ohio River, between 10 and 29 miles below 

 Pittsburg, He states distinctly that it passed " a little south of zenith." 

 In reference to his description, a Philadelphia paper says " The appear- 

 ances were exactly the same as observed here and in other cities. " A 

 correspondent of the United States Gazette, writing from Dennisville, 

 Cape May County, New Jersey, describes it as passing, when first ob- 

 served at that place, '* directly through the zenith." He also mentions 

 the fact noticed at other places, that a short time before the arch began 

 to fade, its summit swayed several degrees to the southward. 



According to the preceding data, the elevation of the luminous band 

 or arch was certainly more than 50, and probably exceeded 100 miles. 

 This fact may, we think, be regarded as favoring the ingenious hypothe- 

 sis suggested by M. Poisson in order to account for the spontaneous 

 combustion of aerolites, above the limits usually assigned to the atmos- 

 phere : viz., that the electric fluid, in its neutral state, forms a kind of 

 atmosphere, extending far beyond that of air ; which is subject to the 

 attraction of the earth, although physically imponderable ; and which 

 consequently follows our globe in its motions. * 



Since writing the above, I have learned from the London Athenaeum 

 of January 2nd, 1847, that a similar phenomenon was observed in Can- 

 ada, on the 21st of September, 1846, and also in England on the same 

 night. It is worthy of remark, that during that evening also the com- 

 mon aurora borealis was very brilliant. Mr. Langton, of Fenelon, Up- 

 per Canada, who has given a very interesting description of the arch as 

 seen at that place, gives its geneial direction as almost exactly east and 

 west, and its average breadth about 4°. He states likewise that 

 the light appeared to roll from cast to west in irregular cloudy 

 waves. "The beauty and singularity of the arch," lie says in conclu- 

 ding his description, " induced me to observe its different features mi- 

 nutely at the time ; and the coincidence of a similar appearance, in Eng- 

 land, on the same night, has led me to communicate the particulars ; 

 'See Note 33, p. 113, of the English Translation of Humboldt's Cosmos: 

 Published by the Harpers, New Yoik, 



