14 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



space remaining behind this light is the well-known dark 

 segment. 5. The radiating margin usually divides into a 

 number of secondary areas which we may call the fields of 

 radiation. 6. The fields of radiation appear to move with 

 great velocity to the westward, in the direction of the mag- 

 netic parallel circle. 7. The fields of radiation send out up- 

 ward masses of bright light arranged in columnar form the 

 rays proper which take the direction of the magnetic dip. 

 All the luminous emissions of a radiating: character in other 

 directions are not to be considered as genuine rays. 8. The 

 height of the base of the rays is various, some observations 

 making it from 80 to 140 miles, and the greatest height not 

 exceeding 160 miles. 9. The height of the summit of the rays 

 in extended auroras reaches 280 miles, sometimes 400, the 

 maximum being 600. 10. The rays always have white light 

 below, and pass at the summit into red. 19 C, February 10, 

 1872,41. 



THE AURORA OF FEBRUARY 4, 1872. 



The scientific journals at home and abroad have had much 

 to say of the extent and magnificence of the auroral display 

 of February 4, 1872. This is generally asserted to have been 

 one of the most magnificent exhibitions of the kind seen in 

 Europe for the past twenty or thirty years ; and there is per- 

 haps none recorded over as wide an extent, and as critically 

 investigated by so many scientific observers. It is quite 

 probable, indeed, that the comparison of the phenomena ob- 

 served, after the data are all accessible, w T ill add greatly to 

 our knowledge of the true nature of this celestial apparition. 



One marked feature of the exhibition was the fact that it 

 seemed not to have been noticed in the extreme north of Eu- 

 rope, where auroras are very abundant, but was observed to 

 the best advantage in countries where those displays are 

 very rarely seen. 12 A, February 22, 1872, 322. 



SPECTRUM OF THE AURORA. 



The recent brilliant displays of the aurora have afforded 

 opportunity for a number of observations with the spectro- 

 scope, which may help to unravel the mystery which sur- 

 rounds this phenomenon. We may begin this brief review 

 of recent observations by calling to mind the researches of 



