174 PROCEEDINGS OF THE ACADEMY OP 



side of any stratum, say two hundred feet thick, is always negative to the 

 upper side ; and at the same time it is positive to the upper side of a stratum 

 directly below. The lower side of this lower stratum is positive to the solid 

 earth below, which is negative to tiie air above. From this condition in the 

 air, and the relative condition between the air and the ground, there must be 

 a constant passage of electricity more or less from the atmosphere to the 

 earth. As the extra accumulation is at the north, it must go south through 

 the earth for the equilibrium. This extra accumulation in the north is proved 

 by the visible aurora iiorealis. 



The second path southward of the superabundant electricity at the north is 

 along the top, or through the exceedingly rare upper regions of the atmos- 

 phere. The auroral arch has in some cases been found to be about forty 

 miles above the earth's surface. We may say it is at or near the top of the 

 atmosphere possessing an appreciable density. This arch always moves to- 

 wards the south. While it moves it seems to part with portions of Itself in 

 the form of " streamers," — far extending lines upward, — in the directions of 

 the magnetic curves. The "streamers" cease to be visible before they reach 

 low southern latitudes, and so does the arch ; but the want of visibility, either 

 in the streamers or In the arch, is no reason why the electric fluid does not 

 continue to flow In both cases towards the equator. Streamers cannot be 

 supposed to rise from the arch in the lower latitudes, because there the mag- 

 netic curves coincide so nearly with the horizon ; and the parting of the 

 streamers may perhaps cause the visibility of the arch. 



Nearly twenty years ago 1 had a very distinct view of the electric fluid 

 flashing along the top of the atmosphere. It consisted of sheets of flame, 

 thin and broken, darting from north to south. I was standing on the back 

 platform of the last car of a train travelling from New York to Newark, N. J., 

 where I then resided. The sky was perfectly clear, and I think, though I am 

 not certain, it was bright moonlight. I remember very distinctly that no 

 aurora borealls was seen, — at least such as the aurora generally ajjpears. But 

 in looking towards the east I saw at intervals bright patches of flaiue shooting 

 from north to south. These fiery patches were not the mild faint glow of the 

 ordinary aurora, but bright like flame, though very much broken and ragged, 

 evidently very thin, and about eight or ten degrees in diameter. Their course 

 before disappearance ran through an arc a little longer. It was as though 

 something was passing rapidly through the atmosphere along its top, and by 

 friction was grating fire now and then as it passed. A few others saw the 

 display, and I believed then, as 1 believe now, that I saw the frlctlonal effect 

 of the electric fluid against the atmosphere while flowing from the jjolar to- 

 ward the equatorial regions. The direction of the passage was not towards 

 the zenith to form a corona, but from north to south, while appearing in the 

 eastern sky at an elevation of from 30 to 40 degrees. 



During the display of April 15, 1869, one of the most remarkable features 

 was the quick passage offtakes of the light glowing aurora from the northern 

 horizon to the zenith, and sometimes fifteen or twenty degrees beyond. The 

 transfer of the electric matter through this entire space occupied only the 

 fraction of a second. For distinctness of appearance I could not help com- 

 paring these passages with those of breezes of wind across the surface of the 

 water, or over a wheat field when seen from a neighboring elevation. As 

 there are successive flaws of wind, one chasing another, so there were suc- 

 cessive and frequent flaws or discharges of electricity. The next day an ob- 

 server, quite a young man, remarked to me that it was wonderful to see the 

 white clouds rise up from the north and fly swiftly overhead. This very ra- 

 pidity, moving through such an arc In a fraction of a second, shows these 

 clouds to have been electric. It was impossible for me then to conceive how 

 they could have been mere flashes of light. They were not intense in bright- 

 ness like those I saw twenty years ago, but the pale auroral glow as seen in 

 the artificial auroral tube. I gazed at them lung and often, with the profound 



[August, 



