2G ON THE RECENT SECULAR PERIOD 



longitude. 1 That of Sept ember 3d, 1839, which was very splendid in the Northern 

 States, was also so conspicuous at New Orleans as to be mistaken for a fire, and to 

 call out fire companies with their engines. At places nearly in the same latitude, 

 however widely they may differ in longitude, the exhibition is everywhere nearly the 

 same; or at least has the same leading characteristics, and a similar degree of mag- 

 nificence. But in different latitudes, especially in places differing widely in latitude, 

 the effect of parallax is plainly discernible. Thus the great aurora of September 3d, 

 1839, which was described as very brilliant in England, in Connecticut, and in 

 Missouri, exhibited in Tennessee only an auroral bank in the north, and a few bril- 

 liant streamers, although it was pronounced to be the most splendid aurora ever seen 

 there by the oldest inhabitants. 2 So that of July 1, 1837, which was magnificent at 

 New Haven, only exhibited streamers for half an hour at Columbus in Georgia. 3 

 The extraordinary exhibition of September 29th, 1851, which in the Northern 

 States was attended by a gorgeous retinue of columns, arches, and coronas, formed 

 at the city of Washington, but half the corona, and at places farther south scarcely 

 any traces of it. 4 While, about 7 o'clock, the corona was completely formed at New 

 Haven, there were seen at Charleston, S. C, only different cloudy masses of purple 

 light, occupying the region of the sky above the northern quarter of the horizon, 

 extending about 40° to the east, and as much to the west of the north point, and 

 rising nearly to the height of the pole star. 3 At 11 o'clock only a faint gleam of 

 auroral light was visible, and soon after a dark band whose culminating point was 

 only two thirds the altitude of the pole star; yet was it at this time that Hon. A. 

 N. Skinner, of New Haven, then at Staten Island, saw a splendid arch with a dense 

 bank of auroral vapor which sent forth streamers, within 20° of the southern horizon. 6 



V. Auroral VAroR. — A great aurora is preceded by a large bank, or cloud, of a 

 peexdiar vapor, resting on the northern horizon, commonly of a milky ap>pearance, but 

 sometimes of a smoky hue, or of the two mixed together. This vapor apparently contains 

 the material from which the aurora is fed, and when it is either wanting, or is 

 small in quantity, the exhibition seldom reaches a high order or lasts long. That 

 the auroral vapor has a density extremely low — less than the lightest fog, is 

 evident from the stars being seen through it with little loss of light. It is, how- 

 ever, sometimes so much accumulated and so luminous as sensibly to impair the 

 brightness of the stars, or even to extinguish those of the lower magnitudes. 



VI. Auroral Waves. — These leaves, when peexdiarly grand, make their appearance 

 later than the streamers and arches, and usually later than the corona; and they con- 

 tinue to a later hour of the night, often presenting a sublime feature after the other 

 leading characteristics of the aurora are over. They appear at a lower level than 



' It is worthy of remark, that great auroras extend much further from east to west than from north 

 to south. As they are very seldom seen below lat. 30°, we may take 60° from the pole as the maxi- 

 mum in latitude, while in longitude they extend, as in the case of that of November, 1848, at least 150°. 

 Since, however, there is reason for believing that the exhibition which descends as low as 30° does not 

 reach to the pole on the north, probably the extent from north to south is much less than 60°. 



a Amer. Journ., XXXVIII, 261. 3 lb., XXXIII, 144. 



4 National Intelligencer, Oct. 4th. 5 Professor Gibbes, in Charleston Daily News. 



New Haven Journal and Courier, Oct. Gth. 



