22 KANSAS CITY REVIEW OF SCIENCE. 



claimed that the orb of day was approaching, before whose light all luminaries 

 should pale, and so ended the auroral display of that night, but not until a fitting 

 . "finale" was had by a merry dance. The basis of the auroral light is electrici- 

 ty, in fact it may be considered an electric light. True, it is not so brilliant as 

 the light of the same name as that produced by mechanical appliances. This is 

 owing to the diff'usion of electricity over a space of great extent, while in the 

 case of the artificial light the electricity is concentrated and the arc of light in- 

 stead of being diffused is made to flash from one point. That the air is highly 

 charged with electricity during the existence of auroral displays, has been amply 

 verified by the difficulty experienced during Sunday by telegraphers. The dis- 

 patches traversed the wires during the active displays in a confused and unintelli- 

 gible manner, and at times the magnets were almost solely under the influence of 

 nature's great electric battery the " Aurora Polaris." 



VARIETIES OF AURORA. 



Auroras exhibit an infinite variety of appearances, but they may generally 

 be referred to one of the following : 



First — A horizontal aurora or break of day. The polar light may be dis- 

 tinguished from the true dawn by its position in the heavens, since in the United 

 States it always appears in the northern quarter. 



Second — An arch of light somewhat in the form of a rainbow. This arch 

 frequently extends entirely across the heavens from east to west, and cuts the 

 magnetic meridian nearly at right angles. This arch does not long remain sta- 

 tionary, but frequently rises and falls ; and when the aurora exhibits great splen- 

 dor several parallel arches are often seen at the same time, appearing as broad 

 belts of light stretching from the eastern to the western horizon. 



Third — Slender luminous beams or columns, well-defined and often of a 

 bright light. These beams rise to various heights in the heavens, sometimes, 

 though rarely, passing the zenith. Frequently they last but a few minutes some- 

 times they continue a quarter of an hour, a half hour, or even a whole hour — 

 sometimes they remain at rest, and sometimes they have a quick, lateral motion. 



Fourth — The coronas luminous sometimes shoot up simultaneously from near- 

 ly every part of the horizon and converge to a point a little south of the zenith, 

 forming a quivering canopy of flame, which is called the corona. The sky now 

 resembles a fiery dome, and the crown appears to rest upon variegated fiery pil- 

 lars which are frequently traversed by waves or flames of light. This may be 

 called a complete aurora, and comprehends most of the peculiarities of the other 

 varieties. The corona seldom continues complete longer than an hour. The 

 streamers then become fewer and less intensely colored ; the luminous arches 

 break up, while a dark segment is still visible near the northern horizon, and at 

 last nothing remains but masses of cirro-cumulus clouds. 



Fifth — Waves or flashes of light. The luminous sometimes appear to shake 

 with a tremulous motion ; flashes like waves of light roll up toward the zenith, 

 and sometimes travel along the line of an auroral arch. Sometimes the beams 



