338 Prof. Hansteen on the Polar Lights, 



2. Additional Observations and Corrections to some Observa- 

 tions on Polar Lights and Polar Nebula. 



The hasty observations to which I now offer a supplement, 

 were not intended for the pubUc at large, but were added 

 by way of notes to a notice of Capt. Scoresby's re-discovery 

 of the east coast of Greenland, in the Magazinfor Naturvi- 

 denskaberne, 1824'. vol. i. p. 85, &c. But having been re- 

 ceived in the Edinburgh Philosophical Journal, where they 

 had become either disfigured or unintelligible by translation, 

 and afterwards inserted in the Jahrb. der Chem. und. Phys. ac- 

 panied by notes of Mr. Ksemtz, I feel myself bound to fur- 

 nish the following collections and additions. 



1. The columns of light shooting up from the northern 

 horizon towards the zenith are not connected, but consist of 

 short parallel rays (or, as Dalton observes, cylinders of light), 

 whose direction nearly coincides with that of the dipping- 

 needle. For when these columns of light pass by the zenith, 

 they seem to be broken off on that point, and form what is 

 called the crown. Let NS (Plate III. fig. I.) be an arch of 

 the circumference of the earth (a part of the magnetic meri- 

 dian through the point C), F^ Ef, D^, &c. the parallel rays 

 of light, forming the mass of the aurora. If the observer at 

 C turns his eye in the direction of CF, CE, CD, a part of 

 each column of light is covered by that lying nearest to it in 

 fi'ont, and the whole mass of light from F to Z and fi'om Z 

 to D seems connected. But in the direction of CZ, where 

 the Une of vision is parallel to the columns of light, one only 

 sees the transversal section of the column ; and as these co- 

 lumns of light are at a considerable distance from each other, 

 the blue sky appears through them. If the eye turns towards 

 the west or east, the line of vision again ceases to be parallel 

 with the rays, and there also the mass of light seems to be 

 connected. It must therefore appear as if rays of light were 

 rising from the whole horizon towards the magnetic zenith Z. 

 In the magnetic meridian these rays or columns of light seem 

 to be perpendicular towards the horizon ; but towards the 

 east and west they have a perceptible inclination towards the 

 south, which I have always noticed with strong aurorae. We 

 shall have the clearest form of such an aurora by placing a 

 globe so that its axis shall not be perpendicular to the horizon, 

 but deviate about 18° or 20° from the vertical line; the me- 

 ridians then represent the apparent direction of the streaks of 

 light, and the parallel circle in 80° latitude, or the pole itself, 

 represents the crown (fig. 2.). Thus every observer will see 



the 



