ON THE PERIODICITY OF THE AURORA BOREALIS. 



247 



1 Mem. Acad. Ciencias Madrid, III. 77. 

 ! Tlie aurora was seen at Mark in 1728 seventeen times. 

 ' Those auroras seen in Germany this year were seen as 

 »peciiied for Feb. 9. 



a Gilbert. Annalen der Physik, XXXII. 336, etc. 



3 Comment. Petrop. IV. 121. 



* Tabula Meteorologica, 1728. 



1 Buchner. Miscell. Phys. Med. Math. 1729, pp. 40, 100, etc. 



6 Parish near Nincoplng. 



