18 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



EXTENSION OF THE AURORA OF FEBRUARY 4, 1872, TO THE 



SOUTHERN HEMISPHERE. 



Students of cosmical physics have been much interested in 

 learning whether the great aurora of February 4 was visible 

 in the southern hemisphere as in the northern. Letters re- 

 ceived by the French Academy from St. Denis (Bourbon Isl- 

 and), latitude 21 S., longitude 55 E., decide this question in 

 the affirmative. One writer says that during the night of 

 February 4, 1872, " a brilliant aurora was seen here. It com- 

 menced at half past eight o'clock P.M., or about five o'clock 

 Paris time. The heaven was then tinged with a purple shade, 

 which gradually increased and extended from the south to- 

 ward the southeast and southwest. It looked like the erup- 

 tion of an immense volcano. In the south the coloration ex- 

 tended up to the zenith. Between ten and eleven o'clock the 

 aurora attained its greatest brilliancy and extent. It then 

 shone so brightly that I could distinctly see the lines of my 

 hand and the features of the by-standers. At midnight the 

 aurora was a brick-red color. At three o'clock it became 

 pale again, and the color gradually changed to a golden yel- 

 low like that of sunrise." 



Comparing this account with that of the observations in 

 Europe, it is found that the principal phases of the phenom- 

 enon were seen almost simultaneously in both hemispheres. 

 But Mr. Janssen, the celebrated eclipse observer, who was in 

 India on this night, saw nothing unusual, which raises the 

 question whether the auroras seen in the two hemispheres 

 were actually joined at the equator, and not entirely separate. 

 Mr. Janssen's testimony, however, being only negative, this 

 can not be settled until the reports of other observers near 

 the equator have been received. Indeed, we learn that the 

 aurora was very brilliant at Alexandria, in Egypt, which ren- 

 ders it probable that it was continuous from the northern to 

 the southern hemisphere. 



SPECTRUM OF THE ZODIACAL LIGHT. 



This subject is intimately connected with that of the spec- 

 trum of the aurora, because Angstrom announced that the 

 zodiacal light and the aurora both gave the same monochro- 

 matic spectrum. But Liais, the Brazilian astronomer, has 



