ON THE PERIODICITY OF THE AURORA BOREALIS. 11 



catalogue of 534 auroras observed at Christiania, Norway, between 1837 and 1853 ; 

 Rudolph's catalogue of 185 auroras observed at Jakobshavn, Greenland, between 1840 

 and 1S51 ; Eisenlohr's catalogue of 87 auroras observed at Carlsruhe, Germany, 

 between 1779 and 1831 ; and Cotte's catalogue of 231 auroras observed at Franeker, 

 Holland, between 1771 and 1781, by Van Swinden. Much assistance has been found 

 in Force's notices of auroras published in the Smithsonian Contributions. No great 

 use could be made of Boue's learned catalogue on account of the confusion of old and 

 new style, the substitution of the number of auroras in a month for the day of the 

 month, and other numerous inaccuracies in the compilation and printing of this 

 catalogue. It is not necessary to refer to the general catalogues or tables of Arago, 

 Quetelet, 1 Kamtz, 2 Muncke, Bertholon, Reuss, or to the Collection Academique, as they 

 contain little not derived from older sources already enumerated. 



I have also made a laborious examination of the publications of the English, Swc 

 French, German, Russian, Austrian, and Italian Academies, and of the Journals of those 

 countries, and have collected from these and other sources, as travels, Arctic voyages, 

 histories, &c, numerous examples of auroras which have entered into no former 

 catalogue. The name of the country where an aurora is observed, when known, is 

 printed in italics. The name of the observer is addetj if possible, and also that of the 

 author of the printed record, with such other authorities and references as may be 

 convenient for the student. An attempt has also been made to reduce the date of 

 each observation, when given in old style, to the Gregorian reckoning. But this task is 

 beset with great difficulties. 



In 1780 Van Swinden 3 submitted to the Royal Academy of Sciences of Paris the 

 prospectus of a " Plan d'un Traite sur 1'Aurore Boreale, pour servir de suite a celui de 

 M. de Mairan." Van Swinden informs the public that it was within his power to insert 

 many auroras which Mairan had overlooked, — partly drawn from printed books, but 

 especially derived from two manuscript collections which had been given to him, — 

 the first of 170 auroras observed at Breda by Eckhard, between 1719 and 1740, for 

 which he was indebted to the son of the observer (of these auroras there are G4 

 which are not found in the catalogue of Mairan) ; and the second of G4 auroras 

 observed in North Holland, between 1741 and 1749, which Van Swinden received 

 from Engelman. Van Swinden also promised some observations on auroras made 

 during a maritime voyage, in 1741, which he had in manuscript. He also proposed 

 to extend Mairan's catalogue from 1751 to 1778, by adding printed and manuscript 



1 Sur la Physique du Globe, par Quetelet. 3 Lehrbuch der Meteorologie, III. 46*. 



8 Rozier, Observations sur la Physique, XV. 128-134. 



