52 ON THE RECENT SECULAR PERIOD, ETC. 



air match. If the matter is combustible like ferruginous particles, a real combustion 

 would ensue ; if incombustible, ignition, simply, would follow. 



It may not be easy or possible to explain all the varieties of motion which attend 

 auroral displays, but that "rapid motions," in general, should occur, is a natural 

 consequence of the passage of the earth through a nebulous mass revolving around 

 the sun, either in a direction opposite to that of the earth, or in the same direction 

 with a less velocity. 



The magnetic phenomena accompanying the aurora, imply that the auroral matter 

 has magnetic properties. Tbese make it tend towards the magnetic pole of the 

 earth, cause it to arrange itself in columns parallel to the magnetic meridian, and to 

 form, by perspective, the corona around the pole of the. dipping needle. They like- 

 wise, for the same reason, produce marked effects on the compass-needle, and cause 

 exhibitions of the phenomenon to be more frequent in the polar than in the equa- 

 torial regions, and more abundant and intense on the western than on the eastern 

 continent, since here the principal magnetic pole of the earth is situated. 



PUBLISHED BY THE SMITHSONIAN INSTITUTION, 

 WASHINGTON, D. C. 



MAT, 1856. 



